JP2004354081A - Fatigue tester - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fatigue tester, of which the testing precision can be enhanced, capable of being utilized in a hydraulic servo fatigue tester or the like for acquiring ultrahigh cycle region data. <P>SOLUTION: The fatigue tester 10 is equipped with a main body 11 having a test piece attaching part 20 and an actuator part 40, and a control means 60 which performs feedback control for feeding back the detection signal corresponding to the load applied to a test piece 1 and constituted so that the algorithm of the calculation processing related to the correction of a mu-factor is stepwise changed over corresponding to the converging degree to a target value signal of a detection signal when the waveform of the detection signal is compared with that of the target value signal and the calculation processing related to the correction of the mu-factor and a zero point is performed on the basis of the comparison result by a mu-factor/zero point correcting calculation means 78. Further, this tester may be constituted so as to stepwise change over the algorithm of the calculation processing related to the correction of not only the mu-factor but also the zero point. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

【００７９】
ピークボトムホールド７７は、ひずみ計２２で検出される実測荷重値の波形についての各周期の最大値および最小値を測定し、それを記憶保持する処理を行うものである。
【００８０】
増幅率補正／零点補正計算手段７８は、目標値信号の波形と、ひずみ計２２の検出信号の波形（フィードバック波形）とを比較し、この比較結果に基づき増幅率（ゲイン）および零点（オフセット）の補正に関する計算処理を行うものである。これは、適応比例制御を行うための処理である。目標値信号の波形とフィードバック波形との比較とは、目標値信号の波形の振幅とフィードバック波形の振幅との比較、および目標値信号の波形の零点（オフセット）とフィードバック波形の零点（オフセット）との比較である。ここで、目標値信号の波形の振幅およびオフセットは、前述した如く、図５の試験条件設定画面２００で最初に試験条件を設定するときに外部処理装置９０により算出決定された値である。一方、フィードバック波形の振幅およびオフセットは、ピークボトムホールド７７により測定された最大値および最小値に基づき、増幅率補正／零点補正計算手段７８により算出される。なお、これらの波形の比較処理および比較結果に基づく補正に関する計算処理は、波形一周期毎に行うのが原則であるが、複数周期毎に行うようにしてもよい。
【００８１】
また、増幅率補正／零点補正計算手段７８は、応答信号（ひずみ計２２の検出信号）の目標値信号への収束度に応じ、増幅率（ゲイン）および零点（オフセット）の補正に関する計算処理のアルゴリズムを段階的に切り替える処理を行う。これは、多段適応比例制御を行うための処理である。なお、切り替えるか否かの判断処理は、波形一周期毎に行うのが原則であるが、複数周期毎に行うようにしてもよい。
【００８２】
アルゴリズムを段階的に切り替える処理の具体例として、以下のような２段階の切替処理を挙げることができるが、切替の段階数、アルゴリズムの内容、切替判断方法等は、以下の例に限定されるものではない。
【００８３】
例えば、増幅率（ゲイン）については、次のようなアルゴリズムＡとアルゴリズムＢとを、下記の条件に基づき自動的に切り替えることができる。
【００８４】
＜アルゴリズムＡ＞
疲労試験中のある時刻に、実測荷重の振幅がＡ_ｃで、そのときの比例ゲインがＧ_ｃであるとする。ここで、到達目標荷重の振幅をＡ_ｔとすると、これを達成するための比例ゲイン予測値Ｇ_ｔは、Ｇ_ｔ＝（Ａ_ｔ／Ａ_ｃ）×Ｇ_ｃと考えることができる。このＧ_ｔの値と、現在の比例ゲインＧ_ｃとの差をΔＧとすると、ΔＧは、次の式（４）で与えられる。
【００８５】
ΔＧ＝Ｇ_ｔ−Ｇ_ｃ＝（（Ａ_ｔ／Ａ_ｃ）−１）×Ｇ_ｃ ・・・・・・・（４）
【００８６】
通常の適応比例制御における増幅率の補正に関する計算処理（ＡＧＣ：Ａｕｔｏ Ｇａｉｎ Ｃｏｎｔｒｏｌ）では、上記の式（４）のΔＧを基本にして、次の式（５）で示されるアルゴリズムで最適ゲインを求める計算を行っている。
【００８７】

【００８８】
ここで、ｉは、ｉ番目のサンプリングデータであることを示し、各周期に対応する。従って、ｉの値は、前記式（１）〜式（３）におけるｋよりも長い時間間隔で変わる。また、ｇｔｐは、比例ゲインの変化を滑らかにするために用いるパラメータ（ゲインチューニングパラメータ）である。このｇｔｐの値としては、例えば、経験値として０．０２等を用いることができるが、これに限定されるものではない。以上の方法が、アルゴリズムＡである。
【００８９】
＜アルゴリズムＢ＞
通常の適応比例制御では、上記のアルゴリズムＡのみでＡＧＣを行っている。しかし、実測荷重値が目標値にある程度収束すると、ｇｔｐ×ΔＧの値が極端に小さくなるため、収束が頭打ちになり、誤差を例えば１％よりもさらに小さな値に収束させることが困難となる。
【００９０】
そこで、多段適応比例制御では、試験開始後、実測荷重値が目標値にある程度収束した時点で、ＡＧＣのアルゴリズムを、上記のアルゴリズムＡから下記のアルゴリズムＢに変更する。
【００９１】
（１）Ａ_ｃ＜Ａ_ｔの場合には、比例ゲインを０．０００２増加させる。
（２）Ａ_ｃ＞Ａ_ｔの場合には、比例ゲインを０．０００２減少させる。
（３）Ａ_ｃ＝Ａ_ｔの場合には、比例ゲインをそのままとする。
【００９２】
なお、このようなアルゴリズムＢにおいて、増減量は上記の０．０００２に限定されず、他の値としてもよく、また、増加量と減少量とを異なる値としてもよい。
【００９３】
アルゴリズムＡからアルゴリズムＢへの切替のタイミングは、アルゴリズムＡによる制御を行っている際に、初めてｇｔｐ×ΔＧ＜０．０００６を満たした時点である。従って、各周期毎にｇｔｐ×ΔＧ＜０．０００６を満たしているか否かを判断する。なお、０．０００６という数値は、実験により経験的に得られた値であるが、判断基準値は、これに限定されるものではない。
【００９４】
以上のようなアルゴリズムＡからアルゴリズムＢへの切り替えを行う多段適応比例制御により、誤差を±０．１％以下にまで収束させることができる。なお、アルゴリズムＡにおけるｇｔｐの値を、収束の度合いを監視しながら、動的に変更させたり、あるいは上記の例では０．０００６のみとなっている切替の判断基準値（ｇｔｐ×ΔＧの境界値）を複数設け、アルゴリズムＢにおける増減量を変更する等により、３段階以上の切替えを行う多段適応比例制御としてもよい。
【００９５】
また、零点（オフセット）については、次のようなアルゴリズムＣとアルゴリズムＤとを、下記の条件に基づき自動的に切り替えることができる。
【００９６】
＜アルゴリズムＣ＞誤差が定格出力の１．５％よりも大きいときに、次のアルゴリズムＣを用いる。
【００９７】
（１）現在の荷重平均値が目標荷重平均値よりも大きい場合には、オフセットの値を小さくする。調整量は、定格出力の０．１５％である。
（２）現在の荷重平均値が目標荷重平均値よりも小さい場合には、オフセットの値を大きくする。調整量は、定格出力の０．１５％である。
（３）現在の荷重平均値が目標荷重平均値と同じ場合には、オフセットをそのままとする。
【００９８】
＜アルゴリズムＤ＞誤差が定格出力の１．５％以下のときに、次のアルゴリズムＤを用いる。
【００９９】
（１）現在の荷重平均値が目標荷重平均値よりも大きい場合には、オフセットの値を小さくする。調整量は、定格出力の０．００６％である。
（２）現在の荷重平均値が目標荷重平均値よりも小さい場合には、オフセットの値を大きくする。調整量は、定格出力の０．００６％である。
（３）現在の荷重平均値が目標荷重平均値と同じ場合には、オフセットをそのままとする。
【０１００】
ここで、定格出力とは、目標荷重の最大値の絶対値と、目標荷重の最小値の絶対値とのうち、大きい方の値を指す。
【０１０１】
従って、アルゴリズムＣ，Ｄのいずれについても、オフセットの補正量を決定する処理の流れは、同じであり、調整量の数値が異なるだけである。前述したように、本発明では、このように使用データの相違のみの場合も、アルゴリムが相違するものと捉え、「アルゴリズム」を定義している。なお、定格出力の０．１５％、０．００６％という各調整量の値は、実験により経験的に求めたものであるが、この数値に限定されるものではない。また、アルゴリズムＣ，Ｄの切替の判断基準値となる定格出力の１．５％という誤差の値も、これに限定されるものではなく、他の値を用いてもよい。
【０１０２】
なお、上記の例で、定格出力の１．５％となっている切替の判断基準値（誤差の境界値）を複数設け、調整量も別の数値を追加して用意することにより、３段階以上の切替えを行う多段適応比例制御としてもよい。
【０１０３】
また、増幅率補正／零点補正計算手段７８は、ＡＧＣが無効にされているときでも、自動オフセットコントロール（ＡＯＣ：Ａｕｔｏ ｏｆｆｓｅｔ ｃｏｎｔｒｏｌ）を常時有効としている。つまり、試験中、荷重平均値は常に目標値に一致または略一致していることになる。実験者は、図６の試験中画面３００で「ＡＧＣ有効」ボタン３６０を用いて、ＡＧＣの有効・無効の選択を行うことができる。なお、本実施形態の疲労試験機１０では、試験前に、一度平均値の調整を行うため、試験開始直後から平均値の誤差を小さい値にとどめることができる。従って、実際に使用されるオフセット調整量は、殆どアルゴリズムＤの値となってもよい。
【０１０４】
増幅率補正手段７９および零点補正手段８０は、増幅率補正／零点補正計算手段７８による計算結果をメモリに記憶しておき、この計算結果に基づき、増幅率および零点の補正処理をそれぞれ行うものである。増幅率補正／零点補正計算手段７８による処理が波形一周期毎に行われるので、増幅率補正手段７９および零点補正手段８０による補正処理の内容は、波形一周期毎に更新される。
【０１０５】
カウンタ７５は、疲労試験に必要な繰返し数の計数処理を行うとともに、カウンタリミットの処理を行うものである。カウンタリミットは、試験繰返し数が規定の値に達した時点で試験を停止する機能である。規定の値とは、実験者が、図５の試験条件設定画面２００の打切り繰返し数の入力部２３３で入力した値である。
【０１０６】
リミッタ７６は、最大リミッタ、最小リミッタ、ゲイン発振防止リミッタ、試験片破断検出機構の各処理を行うものである。
【０１０７】
最大リミッタは、ピークボトムホールド７７で検出した最大値が、試験前に予め設定した値を上回ったときに、一方、最小リミッタは、ピークボトムホールド７７で検出した最小値が、試験前に予め設定した値を下回ったときに、それぞれ試験動作を停止し、異常な荷重負荷が繰り返されることを防止する機能である。試験前に予め設定した値とは、実験者が、図５の試験条件設定画面２００の許容過大誤差の入力部２３１で入力した値に基づき算出された値である。
【０１０８】
ゲイン発振防止リミッタは、オートチューニングにより、無制限に出力が増大し、試験が不安定となることを防止する機能である。実験者が、図５の試験条件設定画面２００の許容最大ゲインの入力部２３２で入力した値によりリミッタをかける。
【０１０９】
試験片破断検出機構は、応答荷重波形の急激な変化を感知することにより試験片１の破断を検出し、試験片１が破断した瞬間に疲労試験を停止することで試験片破面と疲労試験機１０そのものを保護する機能である。
【０１１０】
外部処理装置９０は、コンピュータにより構成され、制御性能に直接関係しない各種処理を行う処理手段９０Ａと、例えばキーボードやマウス等の入力手段９６と、例えば液晶ディスプレイやＣＲＴディスプレイ等の表示手段９７とを備えて構成されている。また、例えばプリンタやプロッタ等の出力手段を適宜設けてもよい。
【０１１１】
処理手段９０Ａは、待機中画面表示・入力受付処理手段９１と、試験条件設定画面表示・入力受付処理手段９２と、試験中画面表示・入力受付処理手段９３と、相反操作強制無効手段９４と、入力パラメータ監査手段９５とを含み構成されている。
【０１１２】
待機中画面表示・入力受付処理手段９１は、試験中以外の状態でアクチュエータ部４０を動作させる場合に使用する図４の待機中画面１００を表示する処理、およびこの待機中画面１００を用いて行われる実験者によるアクチュエータ部４０に対する操作入力を受け付ける処理を行うものである。
【０１１３】
試験条件設定画面表示・入力受付処理手段９２は、試験条件を設定するための図５の試験条件設定画面２００を表示する処理、およびこの試験条件設定画面２００を用いて行われる実験者による試験条件の設定入力を受け付ける処理を行うものである。実験者が、図５の試験条件設定画面２００で必要な数値を入力して決定を指示すれば、入力された試験条件は、この試験条件設定画面表示・入力受付処理手段９２により、ＤＳＰコントローラ７０の制御プログラムが解釈できるパラメータに自動変換され、ＤＳＰコントローラ７０に転送される。
【０１１４】
試験中画面表示・入力受付処理手段９３は、試験中に試験状況をモニタする図６の試験中画面３００を表示する処理、およびこの試験中画面３００を用いて行われる実験者による入力を受け付ける処理を行うものである。また、試験中画面表示・入力受付処理手段９３は、試験中に異常が発生し、試験が停止した場合には、ＤＳＰコントローラ７０の制御プログラムと通信を行って原因を調査し、レポートする処理を行う。
【０１１５】
相反操作強制無効手段９４は、ある操作を実行中に、行ってはならない操作または行うべきでない操作を強制的に無効にする処理を行うものである。例えば、試験中には、試験条件のパラメータを変更することができないようになっている。
【０１１６】
入力パラメータ監査手段９５は、実験者により入力されるパラメータ（試験条件等）が異常か否かを監査する処理を行うものである。例えば、図５の試験条件設定画面２００での矛盾したパラメータ入力を監視する。
【０１１７】
そして、処理手段９０Ａに含まれる各手段９１〜９５は、外部処理装置９０を構成するコンピュータ本体（パーソナル・コンピュータのみならず、その上位機種のものも含む。）の内部に設けられた中央演算処理装置（ＣＰＵ）、およびこのＣＰＵの動作手順を規定する一つまたは複数のプログラムにより実現される。
【０１１８】
このような本実施形態においては、以下のようにして疲労試験機１０を用いて超高サイクル域データを取得するための疲労試験が行われる。
【０１１９】
先ず、実験者は、疲労試験を行う前に、調芯用ダミー試験片を用いて疲労試験機１０の本体１１の調芯作業を行う。図２および図３において、調芯作業では、先ず最初に、調芯用ダミー試験片を下側（ピストン４１側）の掴み部２５に装着する。この際には、試験片ホルダ２５Ａに形成された挿入穴３２に、調芯用ダミー試験片の下側の端部２Ｂを挿入し、ボルト３４を締め込んで試験片固定蓋２５Ｂにより調芯用ダミー試験片の下側の端部２Ｂを押さえ付けて固定する。
【０１２０】
次に、上側（ロードセル２１側）の掴み部２４の試験片ホルダ２４Ａに形成された挿入穴３１に、調芯用ダミー試験片の上側の端部２Ａが入るようにロードセル２１の水平位置を調整する。
【０１２１】
続いて、ロードセル２１の水平位置を調整後に、ボルト２６によりロードセル２１を固定し、ロックナット３０を締める。最後に、調芯用ダミー試験片を取り外す。
【０１２２】
以上の調芯作業は、数分程度で行うことが可能であり、従来のように試験片にひずみゲージを貼って調芯作業を行う場合に比べ、作業時間が格段に短縮できる。この調芯作業の後は、疲労試験用の試験片１を無作為に何回取り付けたとしても、試験片１には、側面からの拘束力が加わることはない。従って、この調芯作業は、従来の場合と異なり、疲労試験毎に行う必要はない。
【０１２３】
実験者は、上記の如く調芯用ダミー試験片を用いて調芯作業を行った後に、疲労試験を行うために、疲労試験機１０の本体１１の試験片取付部２０に、試験片１を取り付ける。この際、実験者は、外部処理装置９０の待機中画面表示・入力受付処理手段９１により表示手段９７の画面上に表示された図４の待機中画面１００を用いて、試験片１の取付作業に必要なピストン４１の操作を行う。
【０１２４】
図４において、待機中画面１００には、フィードバック値表示部１１０と、試験条件表示部１２０と、ピストンコントロール部１３０と、「通信終了」ボタン１４０と、「試験条件設定」ボタン１５０と、「試験コンソールへ」ボタン１６０と、「数値オフセット入力」ボタン１７０とが設けられている。
【０１２５】
フィードバック値表示部１１０には、ひずみ計２２の検出信号から得られる負荷荷重の表示部１１１と、負荷荷重を試験片直径を用いて換算した負荷応力の表示部１１２とが設けられている。応力値への換算処理は、待機中画面表示・入力受付処理手段９１により行われる。
【０１２６】
試験条件表示部１２０には、最大絶対応力、試験応力比、試験片直径、試験周波数の各表示部１２１〜１２４が設けられている。これらの表示値は、実験者が「試験条件設定」ボタン１５０をクリックして図５の試験条件設定画面２００で入力した値である。
【０１２７】
ピストンコントロール部１３０には、ピストン４１を前進移動（上昇）させる上昇ボタン１３１と、ピストン４１を後退移動（下降）させる下降ボタン１３２と、ピストン４１を中央位置にするニュートラルボタン１３３と、ピストン４１の前進量（上昇量）をバー表示する前進量表示部１３４と、ピストン４１の後退量（下降量）をバー表示する後退量表示部１３５と、サーボバルブ５０の零点の調整量を入力するバルブ零調入力部１３６と、バルブ零調入力部１３６で入力した値を実際に設定する「Ｓｅｔ」ボタン１３７とが設けられている。なお、サーボバルブ５０の零点は、通常、安全サイドにずらしてあるので、これを予め補正して精密な制御を行うために零点調整を行う。
【０１２８】
「通信終了」ボタン１４０は、ＤＳＰコントローラ７０との通信を終了させるボタンであり、「試験条件設定」ボタン１５０は、図５の試験条件設定画面２００へ移動するためのボタンであり、「試験コンソールへ」ボタン１６０は、図６の試験中画面３００へ移動するためのボタンであり、「数値オフセット入力」ボタン１７０は、試験開始前等の調整時に、強制的に零点（オフセット）をある値に定める場合に使用するボタンである。
【０１２９】
実験者は、試験前に試験条件の設定も行う。この際には、実験者は、図４の待機中画面１００で「試験条件設定」ボタン１５０をクリックする。すると、外部処理装置９０の表示手段９７の画面上には、試験条件設定画面表示・入力受付処理手段９２により、図５の試験条件設定画面２００が表示される。
【０１３０】
図５において、試験条件設定画面２００には、試験条件のうちの主要条件を設定する主要条件設定部２１０と、試験条件のうちの高度な条件の設定を行う高度条件設定部２２０と、各種のリミッタの値を設定するリミッタ設定部２３０と、各設定部２１０，２２０，２３０での入力を取り消す「キャンセル」ボタン２４０と、各設定部２１０，２２０，２３０で入力した条件を実際に設定する「条件を設定」ボタン２５０とが設けられている。
【０１３１】
主要条件設定部２１０には、最大絶対応力、試験応力比、試験片直径、試験周波数の各入力部２１１〜２１４が設けられるとともに、圧縮−圧縮試験を行う場合にチェックを入れるための圧縮−圧縮試験選択チェック入力部２１５が設けられている。ここで入力した最大絶対応力、試験応力比、および試験片直径の各値は、前述した式（１）中の到達目標荷重のサイン波振幅Ａ_ｔおよびサイン波平均値（零点）ＯＦＦ_ｔの算出決定処理に用いられる。この算出決定処理は、試験条件設定画面表示・入力受付処理手段９２により行われる。また、ここで入力した試験周波数の値は、前述した式（１）中のＦの値として設定される。
【０１３２】
高度条件設定部２２０には、ロードセル変換定数、真空バイアス、デフォルトゲインの各入力部２２１〜２２３が設けられている。ロードセル変換定数は、ロードセル２１に負荷される荷重と、ひずみ計２２の出力電圧との関係を示し、ロードセル２１の較正結果に応じて入力するものであり、前述した式（１）中の到達目標荷重のサイン波振幅Ａ_ｔおよびサイン波平均値（零点）ＯＦＦ_ｔの算出決定処理等の各種処理における荷重−電圧換算処理に用いられる。また、デフォルトゲインは、増幅率（ゲイン）の初期値を設定するものである。
【０１３３】
リミッタ設定部２３０には、許容過大誤差、許容最大ゲイン、打切り繰返し数の各入力部２３１〜２３３が設けられている。これらの入力値は、リミッタ７６およびカウンタ７５により行われる各種のリミットの処理に用いられる。
【０１３４】
実験者が、各設定部２１０，２２０，２３０での入力を終えて「条件を設定」ボタン２５０をクリックすると、入力した条件が設定され、図４の待機中画面１００に戻る。そして、実験者は、試験を開始する際には、この画面１００で「試験コンソールへ」ボタン１６０をクリックする。すると、外部処理装置９０の表示手段９７の画面上には、試験中画面表示・入力受付処理手段９３により、図６の試験中画面３００が表示される。
【０１３５】
図６において、試験中画面３００には、試験条件を表示する試験条件表示部３１０と、試験状況を数値表示する試験状況数値表示部３２０と、試験状況として実測荷重に基づく応力表示をグラフ表示で行う試験状況グラフ表示部３３０とが設けられている。
【０１３６】
試験条件表示部３１０には、最大絶対応力、試験応力比、試験片直径、試験周波数の各表示部３１１〜３１４が設けられている。これらの表示値は、実験者が図５の試験条件設定画面２００で入力した値である。
【０１３７】
試験状況数値表示部３２０には、カウンタ７５の計数値を表示するカウント表示部３２１と、現在のゲインを表示するゲイン表示部３２２と、サーボバルブ５０の定格入力のうち何％まで使用しているか（最大流量に対して何％の流量となっているか）という出力レベルを表示する出力ＬＶ表示部３２３と、試験誤差表示部３２４とが設けられている。ここで表示する試験誤差とは、（実荷重振幅−目標荷重振幅）／目標荷重振幅×１００（％）のことをいう。
【０１３８】
試験状況グラフ表示部３３０には、実荷重から算出した応力の波形（横軸を時間とし、縦軸を応力とした波形）が表示される。この際の荷重値から応力値への換算処理は、試験中画面表示・入力受付処理手段９３により行われる。
【０１３９】
これらの試験状況数値表示部３２０および試験状況グラフ表示部３３０の表示内容は、試験中画面表示・入力受付処理手段９３により、定期的に更新される。
【０１４０】
また、試験中画面３００には、オフセットを自動調整する「オフセット自動調整」ボタン３４０と、試験を停止する「試験停止」ボタン３５０と、ＡＧＣを有効にする「ＡＧＣ有効」ボタン３６０と、カウンタ７５の計数値をリセットする「カウンタリセット」ボタン３７０と、除荷を行う「除荷」ボタン３８０と、図４の待機中画面１００に移動するための「メインコンソールへ」ボタン３９０とが設けられている。
【０１４１】
なお、実際に試験を行う場合には、目標荷重のオフセットの値まで静的にオフセットを調整し、その後、それに加算してサイン波形を重畳させる。「オフセット自動調整」ボタン３４０は、試験開始前に荷重を静的にそのオフセット値まで自動的にもっていくためのボタンである。
【０１４２】
また、「ＡＧＣ有効」ボタン３６０をクリックしないと、多段適応比例制御が有効にならず、単なる比例制御となる。この場合には、増幅率（ゲイン）や零点（オフセット）の値は一定値となり、実荷重が外的要因によって目標荷重からずれたとしても、それに適応して増幅率や零点の値の修正動作は行われない。
【０１４３】
このような本実施形態によれば、次のような効果がある。すなわち、増幅率補正／零点補正計算手段７８は、増幅率および零点の補正に関する計算処理を行う際に、実荷重信号（ひずみ計２２の検出信号）の目標値信号への収束度に応じ、増幅率の補正に関する計算処理のアルゴリズムを段階的に切り替える構成とされているので、検出信号が目標値信号にある程度収束したときに、増幅率の補正に関するアルゴリズムを切り替えることにより、検出信号の目標値信号への収束度を高めることができる。従って、試験精度の向上を図ることができる。
【０１４４】
また、増幅率補正／零点補正計算手段７８は、検出信号の目標値信号への収束度に応じ、増幅率のみならず、零点の補正に関する計算処理のアルゴリズムを段階的に切り替える構成とされているので、検出信号の目標値信号への収束度をより一層高めることができ、試験精度をより一層向上させることができる。
【０１４５】
さらに、増幅率補正／零点補正計算手段７８は、アルゴリズムを切り替えるか否かの判断を波形一周期毎に行う構成とされているので、適切なタイミングでアルゴリズムの切替を行うことができる。このため、収束の速度を向上させることができ、試験精度をより一層向上させることができる。
【０１４６】
具体的には、従来の適応比例制御で、目標値信号と検出信号との誤差の収束度が例えば±１％程度であったとすると、本実施形態の多段適応比例制御では、±０．１％以内に収束させることができる。
【０１４７】
そして、疲労試験機１０は、制御手段６０として、ＤＳＰコントローラ７０と外部処理装置９０とを備えているので、ＤＳＰコントローラ７０には、制御性能に直接関係する演算処理（目標値信号と荷重信号との比較、増幅率補正、零点補正、ピークボトムホールド、多段適応比例制御を行うための増幅率や零点の補正に関する計算等の処理）のみを負担させ、一方、外部処理装置９０には、制御性能に直接関係しない演算処理（フィードバックされた電圧を荷重に換算する演算処理、応力の数値表示・応力のグラフ表示・ピストン移動量のバー表示・ピストン操作用ボタンの矢印表示等のように人間が見て扱いやすい表示にするためのインターフェースに係る演算処理）を負担させることができる。つまり、制御性能に直接関係する演算処理用のプログラムと、制御性能に直接関係しない演算処理用のプログラムとを完全に分離し、これらの各プログラムを実行するハードウェアを分離することができる。
【０１４８】
このため、ＤＳＰコントローラ７０の処理負担を軽減できるので、応答性や荷重精度、外乱に対する収束性等の制御性能に直接関係する演算処理についての処理速度を向上させることができ、この点でも試験精度の向上を図ることができる。
【０１４９】
また、外部処理装置９０は、待機中画面表示・入力受付処理手段９１、試験条件設定画面表示・入力受付処理手段９２、および試験中画面表示・入力受付処理手段９３を備えているので、実験者は、試験およびその準備の各場面において、図４の待機中画面１００、図５の試験条件設定画面２００、図６の試験中画面３００の３つの画面のうちのいずれかを参照しながら、各場面で必要となる情報の表示のみを確認し、また、各場面で必要となる入力作業のみを行うことができる。従って、実験者は、試験およびその準備の各場面で必要最低限の操作を行えばよくなるので、余分な操作を行ったり、余分な情報を参照して余分な事を考える余地を排除することができ、操作性の向上を図ることができる。そして、操作性の向上を図ることができるため、誤認識や誤操作等の発生も回避または抑制することができ、試験精度の向上にも繋がる。
【０１５０】
そして、待機中画面表示・入力受付処理手段９１により、図４の待機中画面１００のピストンコントロール部１３０において、上昇ボタン１３１および下降ボタン１３２が矢印表示とされ、前進量表示部１３４および後退量表示部１３５がバー表示とされているので、実験者は、ピストン４１の操作を直感的に行うことができる。また、これにより誤操作等も回避または抑制することができる。さらに、フィードバック値表示部１１０が設けられ、応力表示が行われるので、実験者は、現在の荷重の負荷状態を容易に確認することができる。
【０１５１】
また、試験条件設定画面表示・入力受付処理手段９２により、図５の試験条件設定画面２００で、最大絶対応力、応力比、および試験片直径の入力を受け付けることができる。このため、実験者は、応力・応力比・試験片直径という普段使用するパラメータのみを使用すればよくなるので、疲労試験機１０の操作性を向上させることができ、疲労試験機や制御の知識がない実験者でも容易に疲労試験を行うことができる。
【０１５２】
さらに、試験中画面表示・入力受付処理手段９３により、図６の試験中画面３００の試験状況グラフ表示部３３０において、応力のグラフ表示が行われるので、実験者は、現在の試験状況を容易かつ直感的に把握することができる。また、実験者は、各ボタン３４０〜３９０を押していくだけで、設定した条件での疲労試験を適切に行うことができる。
【０１５３】
そして、外部処理装置９０は、相反操作強制無効手段９４を備えているので、誤操作を防止できる。
【０１５４】
また、外部処理装置９０は、入力パラメータ監査手段９５を備えているので、試験の安全性を高めることができる。
【０１５５】
さらに、疲労試験機１０では、試験片１および本体１１の各構成部品の各面の平行度を向上させたので、偏荷重の発生を抑えることができる。また、これと併せ、試験片１の端部１Ａ，１Ｂと上下の掴み部２４，２５とのはめ合いを緩めにしたので（図３参照）、試験片１に側面（試験片１の端部１Ａ，１Ｂの外周面１Ｅ，１Ｆ）からの拘束力が加わらないようにすることができ、偏荷重の発生を抑えることができる。このため、試験精度を向上させることができる。そして、通常、はめ合いを緩くすると、疲労試験中に試験片１の横ずれが懸念されるが、試験片１および本体１１の各構成部品の各面の平行度を向上させているので、試験片１に横ずれを生じさせる力が加わることを回避できる。
【０１５６】
そして、試験本番で用いる試験片１の端部１Ａ，１Ｂよりも大きい端部２Ａ，２Ｂを有する調芯用ダミー試験片を用いて調芯作業を行うので、調芯作業を精度よく行うことができることに加え、前述した緩めのはめ合いも容易に実現できる。また、調芯用ダミー試験片による調芯作業を一回行えば、そのままの状態で複数の試験を行うことができるので、実験者の作業の手間を軽減できる。
【０１５７】
なお、本発明の効果を確かめるために、次のような手順で偏応力Δσの測定実験を行った。先ず、調芯用ダミー試験片を用いて疲労試験機１０の調芯作業を行う。次に、試験片中央部の外周を３分割した位置に合計３枚のひずみゲージを貼った試験片１を試験片取付部２０に取り付ける。この際、ひずみゲージの値は参考にしない。続いて、試験片１に±４００ＭＰａの静的応力を負荷する。最後に、ひずみゲージの値から偏応力Δσを算出する。そして、以上の測定を数回行った。
【０１５８】
上記の測定結果は、次のようになった。負荷応力±４００ＭＰａのときの偏応力Δσは、３．２〜３．９ＭＰａであった。Δσの割合は、負荷応力に対して０．８〜２．３％である。この値は、疲労試験結果には全く影響しない値である。また、前述した特許文献１に記載された本願出願人による疲労試験機（球状ベアリングを備えた疲労試験機）では、負荷応力４００ＭＰａに対するΔσの割合は、３．５〜７．４％である。従って、本実施形態の疲労試験機１０では、偏荷重を大幅に軽減できたことがわかり、これにより本発明の効果が顕著に示された。
【０１５９】
なお、本発明は前記実施形態に限定されるものではなく、本発明の目的を達成できる範囲内での変形等は本発明に含まれるものである。
【０１６０】
すなわち、前記実施形態では、増幅率補正／零点補正計算手段７８は、増幅率および零点のいずれについても、それらの補正に関する計算処理のアルゴリズムを段階的に切り替える構成とされていたが、本発明では、増幅率についてだけアルゴリズムを段階的に切り替える構成としてもよい。但し、前記実施形態のように増幅率および零点の双方についてアルゴリズムを段階的に切り替える構成としておけば、試験精度をより一層向上することができる。
【０１６１】
【発明の効果】
以上に述べたように本発明によれば、増幅率補正／零点補正計算手段により、検出信号の波形と目標値信号の波形とを比較してこの比較結果に基づき増幅率および零点の補正に関する計算処理を行う際に、検出信号の目標値信号への収束度に応じ、増幅率の補正に関する計算処理のアルゴリズムを段階的に切り替えるので、検出信号が目標値信号にある程度収束したときに、増幅率の補正に関するアルゴリズムを切り替えることにより、検出信号の目標値信号への収束度を高めることができ、試験精度の向上を図ることができるという効果がある。
【０１６２】
また、本発明によれば、デジタルコントローラとは別途に設けられた外部処理装置により、待機中画面、試験条件設定画面、試験中画面の３つの画面の表示処理およびこれらの画面を用いた入力の受付処理を行うので、操作性の向上を図ることができ、実験者の操作負担を軽減して誤認識や誤操作等の発生を回避または抑制し、試験精度の向上を図ることができるという効果がある。
【０１６３】
さらに、本発明によれば、試験片および試験機本体構成部品の各面の平行度を向上させ、かつ、試験片の端部と掴み部とのはめ合いを緩めにしたので、偏荷重の発生を抑えることができ、試験精度の向上を図ることができるという効果がある。
【図面の簡単な説明】
【図１】本発明の一実施形態の疲労試験機の全体構成図。
【図２】前記実施形態の疲労試験機の本体を構成する試験片取付部の断面図。
【図３】前記実施形態の試験片取付部の要部の拡大断面図。
【図４】前記実施形態の疲労試験機の制御手段を構成する外部処理装置による処理に伴う待機中画面の例示図。
【図５】前記実施形態の疲労試験機の制御手段を構成する外部処理装置による処理に伴う試験条件設定画面の例示図。
【図６】前記実施形態の疲労試験機の制御手段を構成する外部処理装置による処理に伴う試験中画面の例示図。
【符号の説明】
１ 試験片
１Ａ 試験片の上側の端部
１Ｂ 試験片の下側の端部
１Ｃ 試験片の上側の端面
１Ｄ 試験片の下側の端面
１Ｅ 試験片の上側の端部の外周面
１Ｆ 試験片の下側の端部の外周面
１０ 疲労試験機
１１ 本体
２０ 試験片取付部
２４，２５ 掴み部
３１Ａ，３２Ａ 試験片当接面
３５，３６ 隙間
４０ アクチュエータ部
６０ 制御手段
７０ デジタルコントローラであるＤＳＰコントローラ
７２ 制御信号発生手段を構成するサーボ増幅器
７８ 増幅率補正／零点補正計算手段
７９ 増幅率補正手段
８０ 零点補正手段
９０ 外部処理装置
９１ 待機中画面表示・入力受付処理手段
９２ 試験条件設定画面表示・入力受付処理手段
９３ 試験中画面表示・入力受付処理手段[0001]
TECHNICAL FIELD OF THE INVENTION
INDUSTRIAL APPLICABILITY The present invention relates to a fatigue tester, and can be used, for example, in a hydraulic servo fatigue tester for acquiring data of an ultra-high cycle range.
[0002]
[Background Art]
Fatigue accounts for more than 70 to 80% of damage to mechanical structures, and countermeasures against fatigue are one of the most pressing issues for mechanical engineers. Generally, the SN curve of a steel material is 10 ⁶ -10 ⁷ The horizontal part, that is, the fatigue limit, appears at a certain number of repetitions. Except for the case where repair or part replacement for a certain period of time such as an aircraft or nuclear power equipment is assumed, a general machine is designed based on a fatigue limit.
[0003]
However, in recent years, in high-strength steel, surface hardened steel, etc., 10 ⁷ -10 ⁸ Even in the above long life range, a phenomenon has been reported in which a horizontal portion does not appear in the SN curve and a fatigue limit is not recognized. This phenomenon is called ultra high cycle fatigue or ultra long life fatigue, and active research is currently being conducted to elucidate its mechanism.
[0004]
A testing machine for such ultra-high cycle fatigue is required to have higher performance in terms of repetition rate, load accuracy, load stability, removal of eccentric load, and the like than a conventional fatigue testing machine. Accordingly, the applicant of the present application has developed a shaft load fatigue tester with improved load accuracy, load stability, and operability by operating a hydraulic servo mechanism by performing digital control using a DSP (Digital Signal Processor) controller. (See Patent Document 1). In this axial load fatigue tester, high responsiveness is secured by increasing the natural frequency of the system by increasing the natural frequency of the system by integrating the components of the main body of the tester, and the data of ultra-high cycle range Many acquisitions have been achieved. In addition, a spherical bearing (spherical bearing) is incorporated in the test piece mounting portion, and automatic alignment is performed when a tensile load is applied to the test piece. Further, a computer is connected to the DSP controller, and on the screen of the computer, it is possible to display measured values during the test and to input control parameters.
[0005]
In addition, as a hydraulic fatigue tester that performs digital control, for example, a low cycle fatigue tester that performs data sampling each time the value of the controlled object output amount reaches each of a plurality of predetermined levels, etc. (See Patent Document 2, etc.). In this low-cycle fatigue tester, the number of data points per cycle of the repetitive change of the controlled object output amount can be approximated to an appropriate number without being affected by the length of the cycle of the repetitive change.
[0006]
[Patent Document 1]
JP-A-2002-243606 (FIGS. 1 and 3, paragraphs [0061] to [0063], [0068], [0074] to [0076])
[Patent Document 2]
JP-A-2000-131203 (FIGS. 1 and 7, paragraphs [0007] to [00011], [0026], [0040])
[0007]
[Problems to be solved by the invention]
Incidentally, since the fatigue tester is affected by various disturbances, the load signal may not follow the target value signal when the amplification factor is set to a constant value. In such a case, the maximum value and the minimum value of the load signal are monitored in real time, and the optimum amplification factor correction amount and zero point correction amount are calculated from the difference between the monitoring result and the target value signal. , A correction operation for the disturbance of correcting the amplification factor and the zero point is performed. Such a proportional control is sometimes referred to as an adaptive proportional control because the amplification factor and the zero point are changed every moment according to the disturbance or the like even when there is a disturbance or the like. This adaptive proportional control is also performed in the machine.
[0008]
However, even when such adaptive proportional control is performed, if the load signal converges to the target value signal to some extent, it may not converge any more. Therefore, this problem is solved, and the test is performed by further increasing the degree of convergence. It is desired to improve the accuracy.
[0009]
Also, in the above-mentioned Patent Document 2, the AGC (Auto Gain Control) method for automatically controlling the amplification factor is based on the amplitude of the control target output amount actually generated in a certain cycle during the execution of the control. Since this method modifies the amplitude of the target value signal used in the next cycle, high-precision control cannot be performed from the first cycle. Therefore, the area of the hysteresis curve of the stress-strain curve of the test specimen It is described that it is difficult to apply the method to a low cycle fatigue test having a relatively large value. Therefore, the low cycle fatigue tester described in Patent Document 2 does not control the AGC method in the first place, and thus does not solve the above-mentioned problem.
[0010]
Furthermore, in the fatigue tester described in Patent Document 1 described above, on a screen of a computer connected to a DSP controller, an actual measurement value during a test (for example, a load applied to a test piece, a maximum value thereof, Although the display of the minimum value, the value of the signal of the function generator, etc.) is performed, these displays are displayed as the load value and the voltage value, and are not the stress displays required by the experimenter. Therefore, the experimenter had to calculate and understand the stress based on the diameter of the test piece. In addition, the input of the control parameter cannot be also input by the stress value, and it is necessary to calculate the value of the load or voltage to be controlled based on the diameter of the test piece and to input the value as the control parameter. Furthermore, erroneous recognition or erroneous input hinders improvement in test accuracy. For this reason, it is desired to create an environment in which the operability and usability of the testing machine are improved, the labor of the experimenter and the labor of judgment are reduced, and the test accuracy can be more reliably improved.
[0011]
Incidentally, the fatigue fracture of a high-strength material that is the subject of ultrahigh-cycle fatigue research is more sensitive to surface flaws and stress concentration of inclusions present on the surface than the fatigue fracture of low- and medium-strength materials. If an unbalanced load is applied to the test piece, the surface may be broken even if the test piece originally breaks internally. In such a case, since the reliability of the test results may be significantly reduced, it is necessary to pay close attention to the alignment of the test pieces, and to avoid this, simplify the alignment work (alignment free). Therefore, a test machine and a test piece used for ultra-high cycle fatigue research are required to have a mechanism for preventing an unbalanced load. Therefore, in the fatigue tester described in Patent Document 1 described above, a spherical bearing is incorporated in a test piece mounting portion, and self-alignment is performed when a tensile load is applied to the test piece, so that alignment is performed. Free is realized.
[0012]
However, when a spherical bearing is incorporated as described above, the test conditions are limited to a fatigue test in which only a tensile load is applied (tensile-tensile fatigue test), and a fatigue test involving a compressive load cannot be performed. In the fatigue study, since the tensile-compression fatigue test in which the stress ratio (minimum stress / maximum stress) is -1 is the basic data, the axial load fatigue tester used for ultra-high cycle fatigue research has an alignment-free function. Further, it is required to have a mechanism capable of applying a tension-compression load. On the other hand, in order to obtain high-accuracy data without such a mechanism, it is necessary to perform a centering operation by attaching a strain gauge to a test piece in order to prevent an uneven load. However, this alignment work needs to be performed for each test, and it requires a great deal of time and effort. For this reason, it is desired to improve the test accuracy by preventing the offset load while realizing alignment-free.
[0013]
An object of the present invention is to provide a fatigue tester capable of improving test accuracy.
[0014]
[Means for Solving the Problems]
The present invention controls the operation of an actuator unit by feeding back a detection signal according to a load applied to a test piece, and a main body having a test piece mounting unit for mounting the test piece and an actuator unit for applying a load to the test piece. And a control means for performing feedback control to send a control signal to the main body, the control means is configured to include a digital controller for performing the feedback control by digital processing, the digital controller, the detection signal and A control signal generating means for generating a control signal corresponding to a deviation amount from the target value signal; and an amplifier used for generating a control signal based on a result of comparison between a waveform of the detection signal and a waveform of the target value signal. Amplification factor correction / zero correction calculator for performing calculation processing relating to the correction of the gain and the zero, and an amplification factor correction / zero correction meter Gain correction means for performing gain correction processing based on the calculation result by the means, and zero correction means for performing zero correction processing based on the calculation result by the gain correction / zero correction calculation means. The correction / zero-point correction calculation means is characterized in that the algorithm of the calculation processing relating to the correction of the amplification factor is switched stepwise according to the degree of convergence of the detection signal to the target value signal.
[0015]
Here, the “calculation processing for the amplification factor and the correction of the zero point” includes the processing of calculating the amount of increase or decrease with respect to the original value of the amplification factor and the zero point (the value before correction), and the zero point and the corrected zero point. Any process of calculating the amplification factor value itself (correction value itself) is included.
[0016]
Further, the “configuration for switching algorithms stepwise” includes both a configuration for switching two algorithms and a configuration for switching three or more algorithms. The switching at this time includes both one-way switching that does not return to the original algorithm after switching once, and mutual switching that can return to the original algorithm even after switching once.
[0017]
Further, "switching" the "algorithm" includes, for example, the following. That is, (1) switching of the form of the mathematical expression used for the calculation process is included. For example, there is a change from a linear function to a quadratic function, a change in the exponent, a change from an addition term to a subtraction term or vice versa, a change in the number of terms, and the like. (2) Switching the value of a coefficient or a constant included in a mathematical expression used in the calculation process is included. For example, a process multiplied by 0.1% is changed to a process multiplied by 0.05%. (3) Switching data or data groups used for calculation processing is included. (4) Switching the structure of a selection process (for example, processing of an IF statement or the like) or a branching process (for example, processing of a CASE statement or the like) is included. For example, the order and position of the selection processing in the program are changed, the number of branches is increased / decreased, and the degree of layering of the selection processing and the branch processing is changed. (5) Switching to a completely different algorithm is included. For example, switching from an algorithm for performing a calculation process using a mathematical expression to an algorithm for performing a data selection process, or switching from an algorithm for performing a calculation process using a mathematical expression to a routine having a different processing content (for example, a routine using a different mathematical formula, Switching to an algorithm for performing a selection process of a routine using different data.
[0018]
In such a fatigue tester of the present invention, the amplification factor correction / zero correction calculation means compares the waveform of the detection signal with the waveform of the target value signal, and calculates the amplification factor and zero correction based on the comparison result. When performing the processing, the algorithm of the calculation processing relating to the correction of the amplification factor is switched stepwise according to the degree of convergence of the detection signal to the target value signal.
[0019]
Therefore, when the detection signal converges to the target value signal to some extent, by switching the algorithm related to the correction of the amplification factor, it is possible to avoid a state where the convergence reaches a plateau and increase the degree of convergence of the detection signal to the target value signal. Becomes possible. Therefore, the test accuracy is improved, and the above-mentioned object is achieved.
[0020]
Further, in the fatigue tester described above, the amplification factor correction / zero correction calculation means is configured to switch the algorithm of the calculation process for the correction of the zero in a stepwise manner according to the degree of convergence of the detection signal to the target value signal. It is desirable.
[0021]
In the case where the algorithm of the calculation process related to the correction of the zero point is switched stepwise as described above, the algorithm can be switched not only for the amplification factor but also for the calculation process related to the correction of the zero point. It is possible to further improve the degree of convergence to the test and further improve the test accuracy.
[0022]
Further, in the fatigue test machine described above, the amplification factor correction / zero correction calculation means compares the waveform of the periodically changing detection signal with the waveform of the periodically changing target value signal for each cycle of the waveform. Then, based on the amount of deviation between both waveforms obtained as a result of the comparison, calculation processing relating to amplification factor and zero point correction is performed for each cycle of the waveform, and whether to switch the algorithm when performing this calculation processing is determined. It is desirable that the judgment is made every cycle.
[0023]
In the case where the determination as to whether or not to switch the algorithm is made in each cycle of the waveform, the switching of the algorithm can be performed at an appropriate timing, the convergence speed is increased, and the test accuracy is further improved. Is improved.
[0024]
In the specification of the present application, the control that involves the stepwise switching of the algorithm of the calculation processing relating to the correction of the amplification factor and the zero point as described above is referred to as multi-stage adaptive proportional control (MAP: Multimode Adaptive Proportional Control). . Such multi-stage adaptive proportional control can be applied not only to the fatigue tester of the present invention but also to other controlled devices. That is, an output signal (corresponding to a detection signal corresponding to the load applied to the test piece) from the controlled device (corresponding to the body of the fatigue tester) is fed back to control the controlled device. In order to realize a system for performing feedback control that sends a control signal to a control target device, a digital controller that performs feedback control by digital processing is provided, and the digital controller is provided in accordance with a deviation amount between an output signal and a target value signal. Control signal generating means for generating a control signal; comparing the waveform of the output signal with the waveform of the target value signal; and performing calculation processing relating to correction of the amplification factor and zero used in the generation processing of the control signal based on the comparison result. Amplification factor correction / zero correction calculation means; and amplification correction processing based on the calculation result by the amplification correction / zero correction calculation means. And a zero-point correction unit for performing a zero-point correction process based on the calculation result of the amplification-factor correction / zero-point correction calculation unit. It is also possible to adopt a configuration in which the algorithm of the calculation process relating to the correction of the amplification factor is switched stepwise according to the degree of convergence to the value signal. Further, in addition to the amplification factor, a configuration may be adopted in which the algorithm of the calculation process regarding the correction of the zero point is switched stepwise.
[0025]
The present invention provides a main body having a test piece mounting part for mounting a test piece and an actuator part for applying a load to the test piece, and feeds back a detection signal corresponding to the load applied to the test piece to control the operation of the actuator part. In a fatigue tester provided with control means for performing feedback control for sending a control signal for control to the main body, the control means includes a digital controller for performing feedback control by digital processing, and a digital controller connected to the digital controller. And an external processing device that performs processing other than the processing related to feedback control by transmitting and receiving information between the external processing device and the standby processing device that is used when the actuator unit is operated in a state other than during the test. The process of displaying the middle screen and performed using this waiting screen Waiting screen display / input reception processing means for performing processing for accepting operation input to the actuator unit by the examiner, processing for displaying a test condition setting screen for setting test conditions, and an experiment performed using the test condition setting screen Test condition setting screen display / input reception processing means for performing processing for accepting test condition setting input by a user, processing for displaying an in-test screen for monitoring the test status during a test, and an experiment performed using the in-test screen And a screen display / input acceptance processing means for performing a process of accepting an input by a user.
[0026]
Here, the “processing related to feedback control” includes, for example, the above-described calculation processing related to the correction of the amplification factor and the zero point, the correction processing of the amplification factor and the zero point, and the like, in addition to the processing of the main loop of the feedback.
[0027]
In such a fatigue tester of the present invention, the display processing of the three screens of a standby screen, a test condition setting screen, and a screen during the test are performed by an external processing device provided separately from the digital controller, and these screens are displayed. The input process used is accepted. Therefore, these screens are switched for each situation of the test machine operation, that is, for each scene from the test preparation stage to the actual stage.
[0028]
For this reason, in each scene of the test and its preparation, the experimenter checks only the display of the information necessary for each scene while referring to any of the three screens, and inputs necessary information for each scene. Only work. Therefore, the experimenter only needs to perform the minimum necessary operations in each stage of the test and the preparation thereof, and eliminates the need to perform extra operations or refer to extra information and think about extra things. Since it becomes possible, operability is improved. Since the operability is improved, the occurrence of erroneous recognition or erroneous operation is avoided or suppressed, which leads to an improvement in test accuracy.
[0029]
In addition to the standby screen display / input reception processing means, the test condition setting screen display / input reception processing means, and the test-in-progress screen display / input reception processing means, an operation that must not be performed or performed while an operation is being performed. Reciprocal operation forced invalidation means for forcibly invalidating operations that should not be performed, or input parameter auditing means for inspecting whether parameters (test conditions and the like) input by the experimenter are abnormal may be provided. This prevents erroneous operation, which leads to further improvement in test accuracy.
[0030]
Further, the standby screen display / input reception processing means, the test condition setting screen display / input reception processing means, and the test screen display / input reception processing means are all provided in an external processing device. Does not bear the display processing of the three screens and the input reception processing on the three screens. That is, the functions of the man-machine interface between the experimenter and the test machine are all realized by the external processing device, and the digital controller bears only the arithmetic processing directly related to the control performance. For this reason, the processing load on the digital controller is reduced, and the speed of arithmetic processing directly related to control performance such as responsiveness, load accuracy, and convergence to disturbance is improved. The above objects are achieved by these.
[0031]
Further, in the fatigue test machine described above, the test condition setting screen display / input reception processing means performs the combination of the maximum stress and the minimum stress, the combination of the maximum stress and the stress ratio, the minimum stress and the stress as the test conditions on the test condition setting screen. Any of the combinations of the ratios, as well as the input of the test piece diameter, is configured to receive the test screen display / input reception processing means, a configuration in which a test status is displayed as a test status on the test screen, and a graph of stress is displayed. It is desirable to have been.
[0032]
In this way, if the system is configured to accept input based on the stress / stress ratio / specimen diameter on the test condition setting screen and display the stress graph on the screen during the test, the experimenter will Since it is sufficient to use only the commonly used parameter of the piece diameter, the operability of the tester is improved. Moreover, since the stress display on the screen during the test is graphed, the experimenter can intuitively grasp the test status, and the operability of the test machine is further improved. For this reason, even an experimenter who does not have knowledge of a fatigue testing machine or control can easily perform a fatigue test.
[0033]
As described below, a program for causing a computer to function as the external processing device is also a distribution target and a transaction target, as described below. That is, as the external processing device described above, a program or a part thereof for causing a computer to function is, for example, a magneto-optical disk (MO), a read-only memory (CD-ROM) using a compact disk (CD), Read only memory (DVD-ROM) using CD recordable (CD-R), CD rewritable (CD-RW), digital versatile disk (DVD), random access memory (DVD-RAM) using DVD ), Flexible disk (FD), magnetic tape, hard disk, read-only memory (ROM), electrically erasable and rewritable read-only memory (EEPROM), flash memory, random access memory (RAM), etc. Can be recorded and stored or distributed In addition, for example, a local area network (LAN), a metropolitan area network (MAN), a wide area network (WAN), a wired network such as the Internet, an intranet, an extranet, or a wireless communication network; It is possible to transmit using a transmission medium such as a combination of these, and it is also possible to carry on a carrier wave. Furthermore, the program described above may be a part of another program, or may be recorded on a recording medium together with a separate program.
[0034]
Further, the present invention includes an actuator portion for applying a load to the test piece, and a test piece mounting portion for mounting the test piece in a state where the test piece is arranged in a direction along the load direction by the actuator portion. A gripping part for gripping both ends of the test piece, and a test piece contacting surface formed on each of these gripping parts with a test piece contact surface with which both end faces of the test piece abut respectively. In the above, the end faces on both sides of the test piece satisfy the parallelism of 0.01 and serve to define the parallelism between the test piece contact surfaces of the gripping portions facing each other among the surfaces of the test machine main body component. The surfaces that fulfill the requirements are all finished in a state that satisfies the parallelism of 0.01, and with the test piece attached to the test piece mounting part, the outer peripheral surface of each end of the test piece and each gripping part That a gap is formed between them It is an feature.
[0035]
Here, the “parallelism” is a parallelism in drafting science (parallelism described in a manufacturing drawing), and is a parallelism of a plane portion with respect to a reference plane. "Parallelism 0.01" means that the space between two planes each parallel to the reference plane and having an interval of 0.01 mm is set as an allowable range. The reference plane may be, for example, a surface on the opposite side of each component.
[0036]
In addition, "each surface that plays a role in defining the parallelism between the test piece contact surfaces of the opposing gripping portions" means that when assembling a plurality of test machine body components to form the test machine body, Specifically, it refers to a surface that will affect the relative posture between the test piece contact surfaces of each gripping portion.
[0037]
In this way, when the parallelism of each surface of the test piece and the components of the test machine main body was improved, and when the fitting between the end portion of the test piece and the grip portion was loosened, the parallelism was improved. As a result, the generation of an eccentric load is suppressed, and since the loose fitting is performed, the restraining force from the side surface (outer peripheral surface of the end of the test specimen) is not applied to the test piece, thereby generating the eccentric load. Can be suppressed. Therefore, the test accuracy is improved. Furthermore, if the fit is loose, there is a concern that the specimen may shift laterally during the fatigue test.However, since the parallelism between the test specimen and each surface of the test machine main body components is improved, the lateral displacement of the test specimen is Is not applied.
[0038]
Further, in the aforementioned fatigue test machine, the gap between the fitting of the outer peripheral surface of each end of the test piece used in the actual test and each gripping portion is the same as that of the dummy test piece for alignment used in the alignment work performed before the test. It is desirable that the gap is larger than the clearance between the fitting between the outer peripheral surface of each end portion and each grip portion.
[0039]
In the case where the alignment work can be performed using the alignment dummy test piece having a larger end than the test piece used in the test production as described above, the alignment dummy test piece is required before the test. After performing the centering operation using the test piece, the dummy test piece for centering is removed, and a test piece used in the actual test is attached. Thus, the alignment work can be performed with high precision, and the loose fitting described above can be easily realized. In addition, if the alignment work is performed once using the alignment test piece, a plurality of tests can be performed in the same state, and the labor of the experimenter is reduced.
[0040]
BEST MODE FOR CARRYING OUT THE INVENTION
An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows the overall configuration of a fatigue tester 10 according to the present embodiment. FIG. 2 is a cross-sectional view of a test piece mounting portion 20 constituting the main body 11 of the fatigue tester 10, and FIG. 3 is an enlarged cross-sectional view of a main part of the test piece mounting portion 20. 4 to 6 show examples of screens associated with processing by the external processing device 90 constituting the control unit 60 of the fatigue tester 10. The fatigue tester 10 is a fatigue tester for acquiring ultra-high cycle range data.
[0041]
In FIG. 1, a fatigue tester 10 includes a main body 11 for mounting a test piece 1 and applying a load to the test piece 1, and control means 60 for controlling an operation for applying a load on the main body 11. It is configured.
[0042]
The main body 11 includes a test piece mounting part 20 for mounting the test piece 1, an actuator part 40 for applying a load to the test piece 1, and a servo valve 50 for switching the hydraulic pressure supplied to the actuator part 40. Have been.
[0043]
In FIG. 2, a test piece mounting part 20 is connected to an upper end 1 </ b> A of the test piece 1 via a plurality of components and detects a load applied to the test piece 1, and detects a strain of the load cell 21. A load cell holder 23 for holding the load cell 21, an upper (load cell 21 side) gripping portion 24 for gripping the upper end 1A of the test piece 1, and a lower end 1B of the test piece 1 for holding. And a lower gripping portion 25 (toward the piston 41).
[0044]
The load cell 21 is fixed to the upper surface 23A of the load cell holder 23 by a plurality of bolts 26. The load cell 21 is slightly deformed by receiving a force from the test piece 1, and the strain at that time is detected by the strain gauge 22, whereby the load applied to the test piece 1 is detected.
[0045]
The load cell holder 23 is fixed to the upper surface 42A of the cylinder 42 of the actuator section 40 by a plurality of bolts (not shown). The load cell holder 23 has a configuration in which upper and lower flange portions are connected by a plurality of (for example, two) pillar portions, and is formed of, for example, a block of metal material.
[0046]
The upper grip portion 24 is provided with a round bar-shaped shaft portion 27 extending upward, and an upper portion of the shaft portion 27 is provided with a male screw 28. A bush 29 is sandwiched between the shaft portion 27 and the load cell 21, whereby the relative positioning between the upper grip portion 24 and the load cell 21 in a direction orthogonal to the load direction (the vertical direction in FIG. 2). Has been done. A lock nut 30 is screwed into the male screw 28 of the shaft portion 27. By tightening the lock nut 30, the relative position of the upper grip portion 24 with respect to the load cell 21 in the load direction is fixed. It has become.
[0047]
The lower grip 25 is screwed to a piston screw 41D provided at the tip of the first piston rod 41B of the actuator section 40 and fixed to the first piston rod 41B. As a result, a load due to the forward and backward movement of the piston 41 of the actuator section 40 is applied to the test piece 1.
[0048]
2 and 3, each of the gripping portions 24 and 25 for gripping the upper and lower ends 1A and 1B of the test piece 1 has a circular insertion hole 31, for inserting the upper and lower ends 1A and 1B of the test piece 1, for example. The upper and lower ends 1A, 1B of the test piece 1 inserted into the respective insertion holes 31, 32 by tightening the plurality of bolts 33, 34 and the test piece holders 24A, 25A having the 32 formed thereon are pressed down and fixed. The test piece fixing lids 24B and 25B are provided. Each of the test piece fixing lids 24B and 25B has a disk shape having a through hole through which the test piece 1 is inserted in the center, that is, a donut shape. Of the cover.
[0049]
Further, each of the test piece fixing lids 24B and 25B may not be divided into two parts, but may be divided into three parts. For example, in the case of three divisions, each of the lid pieces is divided into 120-degree sections to form substantially fan-shaped lid pieces, and each of these lid pieces is attached to each of the test piece holders 24A and 25A using two bolts 33 and 34, respectively. Fix it. That is, the test piece fixing cover 24B is fixed with a total of six bolts 33, and the test piece fixing lid 25B is fixed with a total of six bolts. As a result, even when the test piece 1 is fixed with the same total of six bolts 33, 34, the load applied to each end 1A, 1B of the test piece 1 is more uniform in the three-part division than in the two-part division. become. Therefore, for the test piece 1, a more reasonable load can be achieved by using the three-piece test piece fixing lids 24B and 25B than by using the two-piece test piece fixing lids 24B and 25B. However, there is also an advantage that the two-parting is easier to install. For this reason, for a material that may be fatigue-destructed from a contact portion between the upper and lower ends 1A and 1B of the test piece 1 and the test piece fixing lids 24B and 25B in a long life region, for example, a three-part test is performed. For a material that does not cause the above-described destruction such as high-strength steel using the piece fixing covers 24B and 25B, the test piece 1 is formed by using the two-piece test piece fixing covers 24B and 25B. Depending on the material, the test piece fixing lids 24B and 25B having different numbers of divisions may be used.
[0050]
In FIG. 3, the bottom surfaces of the insertion holes 31 and 32 formed in the test piece holders 24A and 25A serve as test piece contact surfaces 31A and 32A with which the upper and lower end surfaces 1C and 1D of the test piece 1 contact. I have. When the test piece 1 is mounted on the test piece mounting portion 20, the outer peripheral surfaces 1E and 1F of the upper and lower ends 1A and 1B of the test piece 1 and the test piece holders 24A and 25A of the upper and lower grip portions 24 and 25 are provided. The gaps 35 and 36 are respectively formed between the inner peripheral surfaces (side surfaces) 31B and 32B of the insertion holes 31 and 32 formed in the holes.
[0051]
In FIG. 3, the upper and lower ends 2A and 2B of the alignment test specimen used in the alignment work performed before the test are indicated by two-dot chain lines in the figure. Except for the upper and lower ends 2A and 2B, this dummy test piece for centering is the same as the test piece 1 used in the actual test. The outer diameters (diameters) W1 and W2 of the upper and lower ends 2A and 2B of the centering dummy test piece are the outer diameters (diameters) of the upper and lower ends 1A and 1B of the test piece 1 used in the actual test. Each is larger than D1 and D2. Therefore, assuming that the inner diameters (diameters) of the insertion holes 31 and 32 formed in the test piece holders 24A and 25A of the upper and lower grip portions 24 and 25 are H1 and H2, the upper and lower ends of the test piece 1 used in the test production. The gaps (H1-D1) and (H2-D2) for fitting between the outer peripheral surfaces 1E and 1F of 1A and 1B and the inner peripheral surfaces (side surfaces) 31B and 32B of the insertion holes 31 and 32 are dummy tests for alignment. From the gaps (H1-W1) and (H2-W2) between the outer peripheral surfaces 2E and 2F of the upper and lower ends 2A and 2B of the pieces and the inner peripheral surfaces (side surfaces) 31B and 32B of the insertion holes 31 and 32. Are also getting bigger.
[0052]
Furthermore, the processing accuracy of each component (see FIG. 2) that plays a role in defining the parallelism between the test piece contact surfaces 31A and 32A (see FIG. 3) of the upper and lower grip portions 24 and 25 is high, and each component is high. Each surface (upper surface or lower surface) is finished to satisfy the parallelism of 0.01. Further, the surface roughness of each of these surfaces is a roughness equivalent to polishing finish. Note that the parallelism of each of these surfaces is a degree of parallelism after securing a perpendicularity to the load direction (the direction in which the piston 41 advances and retreats).
[0053]
Specifically, the following surface is processed to have a parallelism of 0.01 and a roughness equivalent to polishing finish. That is, in FIG. 3, (1) upper and lower end faces 1C and 1D of the test piece 1, (2) test piece contact surfaces 31A and 32A of the upper and lower grip portions 24 and 25, and (3) upper and lower ends of the test piece 1. Opposite surfaces 1G, 1H of parts 1A, 1B, (4) Upper and lower back side bottom surfaces 24C, 25C of upper and lower test piece fixing lids 24B, 25B abutting on these opposing surfaces 1G, 1H, (5) Upper and lower gripping parts 24, 25 (6) The surfaces 24D, 25D of the test specimen holders 24A, 25A, and (6) the heights satisfying the above conditions for the back side joining surfaces 24E, 25E of the upper and lower test specimen fixing lids 24B, 25B joined to the surfaces 24D, 25D. Accurate processing is performed.
[0054]
2, (7) upper surface 42A of cylinder 42 of actuator section 40, (8) lower surface 23B of load cell holder 23, (9) upper surface 23A of load cell holder 23, (10) lower surface 21A of load cell 21 and (11) ) Lower surface 30A of lock nut 30, (12) Upper surface 29A of bush 29, (13) Lower surface 29B of bush 29, (14) Upper surface 24F of upper gripper 24, (15) Lower surface 25F of lower gripper 25. (16) The upper end surface 41E of the first piston rod 41B is processed with high accuracy satisfying the above conditions.
[0055]
The actuator section 40 is the same as the actuator section of the fatigue tester described in Patent Document 1 by the applicant of the present application, and therefore, detailed illustration is omitted. In FIG. 1, an actuator section 40 includes a piston 41 that moves forward and backward to apply a load to the test piece 1, and a cylinder 42 that is arranged around the piston 41 and guides the sliding of the piston 41. I have. The piston 41 has a head portion 41A that moves forward and backward due to a difference in front and rear oil pressure, a first piston rod 41B provided on a forward side of the head portion 41A, and a second piston provided on a retreat side of the head portion 41A. And a piston rod 41C.
[0056]
In the cylindrical space inside the cylinder 42, a first pressure chamber 43 is formed on the forward side of the head 41A of the piston 41, and a second pressure chamber 44 is formed on the retreat side of the head 41A. The first pressure chamber 43 and the second pressure chamber 44 are supplied with oil for applying oil pressure to the head portion 41A through the first flow path 45 and the second flow path 46 formed in the cylinder 42. ing.
[0057]
The servo valve 50 is similar to the servo valve of the fatigue tester described in Patent Document 1 by the present applicant, and includes four ports (not shown), namely, a P port, an R port, a C1 port, and a C2 port. ing. The P port is connected to a supply pressure pipe of a hydraulic unit (not shown), and the R port is connected to a return pipe connected to an oil tank (not shown). The C1 port and the C2 port are connected to a first flow path 45 and a second flow path 46 formed in the cylinder 42 of the actuator section 40, respectively.
[0058]
The servo valve 50 switches the oil that has entered from the P port to the C1 or C2 port according to a current signal or a voltage signal sent from the DSP controller 70 and allows the oil to flow. For example, when switching to the C1 port, the oil that has flowed out of the C1 port enters the first pressure chamber 43 through the first flow path 45 and pushes the head 41A of the piston 41 to move the piston 41 backward. Due to the backward movement of the piston 41, the oil in the second pressure chamber 44 is pushed by the head portion 41A and enters the C2 port through the second flow path 46. Then, the oil that has entered the servo valve 50 from the C2 port is guided to the R port in the servo valve 50 and finally flows to the return pipe of the hydraulic unit. The oil circulates through such a path. The same is true when switching to the C2 port, in which case the piston 41 moves forward.
[0059]
Accordingly, the switching control of the servo valve 50 causes the piston 41 to move forward and backward. At this time, as shown in FIG. 2, the first piston rod 41B of the actuator unit 40 is connected to the lower end 1B of the test piece 1 via the lower grip 25. Therefore, displacement of the lower end portion 1B of the test piece 1 in the longitudinal direction is given to the lower end 1B of the test piece 1 as the piston 41 moves forward and backward, and as a result, a load is applied to the test piece 1. Has become.
[0060]
As the servo valve 50, for example, a so-called nozzle flapper type servo valve can be suitably used, and a so-called direct drive type servo valve may be used from the viewpoint of further improving responsiveness. Here, the former nozzle flapper type servo valve moves the spool by a pressure difference between the nozzle and the flapper in a part called a first stage, and the latter direct drive type servo valve has a spool Is directly driven by a driving element such as a voice coil or a giant magnetostrictive element or an electrostrictive element.
[0061]
In FIG. 1, a control unit 60 feeds back a detection signal of the strain gauge 22 corresponding to a load applied to the test piece 1 and feeds a control signal for controlling an operation of the actuator unit 40 to the servo valve 50. The DSP controller 70 performs digital processing for processing directly related to the control performance, and transmits and receives information between the DSP controller 70 and the DSP controller 70, thereby directly controlling the control performance. And an external processing device 90 that performs processing that does not need to be performed.
[0062]
1, the DSP controller 70 includes a function generator 71, a servo amplifier 72 constituting a control signal generator, a DA converter 73, an AD converter 74, a counter 75, and a limiter 76. ing. The DSP controller 70 includes a peak bottom hold 77, an amplification factor correction / zero correction calculation unit 78, an amplification factor correction unit 79, and a zero correction unit 80.
[0063]
Each component of the DSP controller 70 includes one or a plurality of central processing units (CPU) provided inside the DSP controller 70 and one or a plurality of control units that define an operation procedure of the CPU. It is realized by a program and various memories such as a ROM and a RAM. The hardware constituting the DSP controller 70 may include, for example, a product-sum operation unit in addition to the CPU. The control program is a program in which an execution program created and compiled by the external processing device 90 is mounted on the DSP controller 70. This control program is created by combining a program created by the external processing device 90 with various instructions (for example, an instruction to output a sine waveform) prepared by a DSP board built in the DSP controller 70. Generally, all parts of the control program may be created by the external processing device 90.
[0064]
The DSP controller 70 performs the following fully digitalized feedback control. Describing from the outline of the control, first, a signal corresponding to the target load is generated in the function generator 71. This signal is amplified at a predetermined amplification rate by the servo amplifier 72, and is converted into an analog current signal or a voltage signal through the DA converter 73. The analog current signal or the voltage signal is replaced with oil having a flow rate proportional to the magnitude of the signal in the servo valve 50, and is guided to the first pressure chamber 43 or the second pressure chamber 44 of the actuator section 40. As a result, the piston 41 moves, and a load is applied to the test piece 1.
[0065]
Next, the load applied to the test piece 1 is converted into an analog voltage signal or a current signal proportional to the load by the load cell 21 and the strain gauge 22, and further converted into a digital signal through the AD converter 74. Then, a deviation value between the target value signal from the function generator 71 and this load signal is calculated, and this value is sent to the servo amplifier 72 again. The deviation finally converges by such a feedback loop, and a load corresponding to the target value signal is applied to the test piece 1.
[0066]
On the other hand, since the fatigue tester 10 is affected by various disturbances as a whole system, the load signal may not follow the target value signal when the amplification factor is set to a constant value. In such a case, a correction operation for disturbance is performed by the peak bottom hold 77, the amplification factor correction / zero correction calculation unit 78, the amplification factor correction unit 79, and the zero correction unit 80. That is, the maximum value and the minimum value of the load signal are monitored in real time by the peak bottom hold 77, and the amplification factor correction / zero correction calculation means 78 calculates the optimum amplification factor correction amount from the deviation between the monitoring result and the target value signal. And the zero point correction amount are calculated. Then, based on the calculation result, the signal of the function generator 71 is corrected by the zero-point correcting means 80, and the amplification factor of the servo amplifier 72 is corrected by the amplification factor correcting means 79.
[0067]
When the load signal deviates from a preset range, such as when the test piece 1 is broken or when an emergency occurs, the fatigue tester 10 is stopped by the limiter 76. The counter 75 counts the number of repetitions required for the fatigue test.
[0068]
Next, the details of the control, that is, the details of the processing of each component of the DSP controller 70 will be described.
[0069]
The function generator 71 performs a process of generating a target value r (k). The target value r (k) is a sine waveform, and is represented by the following equation (1).
[0070]
r (k) = A _t × sin (2π × (F × k / F _s )) + OFF _t ... (1)
[0071]
Where A _t Is the sine wave amplitude (amplitude) of the attained target load, F is the repetition frequency (frequency) of the fatigue test, and F _s Is the operating frequency (sampling frequency) of the A / D converter 74 of the DSP controller 70, and OFF _t Is the sine wave average value (offset) of the zero point, that is, the target load. k is a value meaning one time of the discretized time, for example, the sampling frequency F _s Is set to 50 Hz, time data can be measured 50 times per second. At this time, data of k = 1 represents the first time data of 50 data.
[0072]
Also, the sine wave amplitude A of the target load _t And zero point OFF _t Is determined from the maximum stress and stress ratio input by the experimenter using the test condition setting screen 200 of FIG. 5 described later. This determination processing is performed by the processing means 90A of the external processing device 90, and the result of the determination is transferred to the function generator 71 and used for the processing in the function generator 71. For example, assume that the load cell 21 is calibrated to output 10 V at 1000 kgf (9.81 kN). At this time, when it is desired to apply a repetitive load having a maximum value of 1000 kgf (9.81 kN) and a minimum value of 100 kgf (0.98 kN) to the test piece 1, the amplitude of the target load is (1000−100) / 2 = It is 450 kgf (4.41 kN), and the average value of the sine wave of the target load is (1000 + 100) / 2 = 550 kgf (5.39 kN). In other words, this waveform is a sine waveform having an amplitude of 450 kgf (4.41 kN) vertically around 550 kgf (5.39 kN). At this time, since 1 kgf (9.81 N) corresponds to 0.01 V, if the above target load is converted into a target voltage signal, the amplitude A _t = 450 × 0.01 = 4.5V, zero point OFF _t = 550 × 0.01 = 5.5V. In the fatigue testing machine 10, as described later, the test condition setting screen display / input reception processing means 92 of the external processing device 90 receives the setting input based on the stress value on the test condition setting screen 200 in FIG. The operator does not need to perform the conversion work from the stress value to the load value, and the external processing device 90 performs the conversion processing from the stress value to the load value, the calculation and determination processing of the amplitude and the zero point of the target load, and the conversion into the voltage value. Perform all processing automatically.
[0073]
Further, the repetition frequency F of the fatigue test is input by an experimenter using a test condition setting screen 200 in FIG. 5 described later.
[0074]
The servo amplifier 72 performs a process of generating a control signal to be sent to the servo valve 50. The control by the DSP controller 70 is proportional control, and the manipulated variable u (k) of the proportional control sent to the servo valve 50 as a control signal is expressed by the following equation (2).
[0075]
u (k) = G × e (k) (2)
[0076]
Here, G is an amplification factor, that is, a proportional gain (gain). e (k) is the deviation amount between the target value r (k) and the response value (the load value detected by the strain gauge 22) x (k), and e (k) = r (k) -x (k) ).
[0077]
Accordingly, considering the calculation processing of the deviation e (k) and the processing by the servo amplifier 72 based on the deviation e (k), the value of the control signal finally sent to the servo valve 50 is calculated by the above equation. Substituting equation (1) into (2), the following equation (3) is obtained.
[0078]

[0079]
The peak bottom hold 77 measures the maximum value and the minimum value of each cycle of the waveform of the actually measured load value detected by the strain meter 22, and performs a process of storing and measuring the maximum value and the minimum value.
[0080]
The amplification factor correction / zero correction calculator 78 compares the waveform of the target value signal with the waveform (feedback waveform) of the detection signal of the strain gauge 22, and based on the comparison result, the amplification factor (gain) and the zero (offset). The calculation processing relating to the correction is performed. This is a process for performing adaptive proportional control. The comparison between the waveform of the target value signal and the feedback waveform includes comparing the amplitude of the waveform of the target value signal with the amplitude of the feedback waveform, and comparing the zero point (offset) of the waveform of the target value signal with the zero point (offset) of the feedback waveform. Is a comparison. Here, the amplitude and offset of the waveform of the target value signal are values calculated and determined by the external processing device 90 when the test conditions are first set on the test condition setting screen 200 in FIG. 5 as described above. On the other hand, the amplitude and offset of the feedback waveform are calculated by the amplification factor correction / zero correction calculation unit 78 based on the maximum value and the minimum value measured by the peak bottom hold 77. It should be noted that the comparison processing of these waveforms and the calculation processing relating to the correction based on the comparison result are basically performed for each cycle of the waveform, but may be performed for a plurality of cycles.
[0081]
Further, the amplification factor correction / zero correction calculation means 78 performs a calculation process relating to correction of the amplification factor (gain) and the zero (offset) according to the degree of convergence of the response signal (the detection signal of the strain gauge 22) to the target value signal. A process for switching the algorithm step by step is performed. This is a process for performing multi-stage adaptive proportional control. Note that the process of determining whether or not to switch is performed in principle for each cycle of the waveform, but may be performed for a plurality of cycles.
[0082]
As a specific example of the process of switching the algorithm stepwise, the following two-stage switching process can be given. However, the number of switching stages, the content of the algorithm, the switching determination method, and the like are limited to the following examples. Not something.
[0083]
For example, regarding the amplification rate (gain), the following algorithm A and algorithm B can be automatically switched based on the following conditions.
[0084]
<Algorithm A>
At a certain time during the fatigue test, the amplitude of the measured load is A _c And the proportional gain at that time is G _c And Here, the amplitude of the attained target load is A _t Then, the proportional gain predicted value G for achieving this is _t Is G _t = (A _t / A _c ) × G _c Can be considered. This G _t And the current proportional gain G _c ΔG is given by the following equation (4).
[0085]
ΔG = G _t -G _c = ((A _t / A _c ) -1) × G _c ・ ・ ・ ・ ・ ・ ・ (4)
[0086]
In a calculation process (AGC: Auto Gain Control) related to the correction of the amplification factor in the normal adaptive proportional control, an optimum gain is obtained by an algorithm expressed by the following equation (5) based on ΔG of the above equation (4). We are doing calculations.
[0087]

[0088]
Here, i indicates the i-th sampling data, and corresponds to each cycle. Therefore, the value of i changes at a longer time interval than k in the equations (1) to (3). Gtp is a parameter (gain tuning parameter) used to smooth the change in the proportional gain. As the value of gtp, for example, 0.02 or the like can be used as an empirical value, but is not limited thereto. The above method is algorithm A.
[0089]
<Algorithm B>
In normal adaptive proportional control, AGC is performed only by the algorithm A described above. However, when the measured load value converges to the target value to some extent, the value of gtp × ΔG becomes extremely small, so that the convergence peaks out and it is difficult to converge the error to a value smaller than, for example, 1%.
[0090]
Therefore, in the multi-stage adaptive proportional control, the AGC algorithm is changed from the above algorithm A to the following algorithm B when the actually measured load value converges to the target value to some extent after the start of the test.
[0091]
(1) A _c <A _t In this case, the proportional gain is increased by 0.0002.
(2) A _c > A _t In this case, the proportional gain is reduced by 0.0002.
(3) A _c = A _t In the case of, the proportional gain is left as it is.
[0092]
In such an algorithm B, the increase / decrease amount is not limited to the above-mentioned 0.0002, and may be another value, or the increase amount and the decrease amount may be different values.
[0093]
The timing of switching from the algorithm A to the algorithm B is a time when gtp × ΔG <0.0006 is satisfied for the first time during the control by the algorithm A. Therefore, it is determined whether gtp × ΔG <0.0006 is satisfied in each cycle. Note that the numerical value 0.0006 is a value obtained empirically through experiments, but the criterion value is not limited to this.
[0094]
The error can be converged to ± 0.1% or less by the multi-stage adaptive proportional control for switching from the algorithm A to the algorithm B as described above. Note that the value of gtp in the algorithm A is dynamically changed while monitoring the degree of convergence, or the switching criterion value (boundary value of gtp × ΔG, which is only 0.0006 in the above example). ) May be provided, and multi-stage adaptive proportional control may be performed in which three or more steps are switched by changing the amount of increase or decrease in the algorithm B.
[0095]
As for the zero point (offset), the following algorithm C and algorithm D can be automatically switched based on the following conditions.
[0096]
<Algorithm C> The following algorithm C is used when the error is larger than 1.5% of the rated output.
[0097]
(1) If the current load average is larger than the target load average, the offset value is reduced. The adjustment amount is 0.15% of the rated output.
(2) If the current load average value is smaller than the target load average value, increase the offset value. The adjustment amount is 0.15% of the rated output.
(3) If the current load average value is the same as the target load average value, the offset is left as it is.
[0098]
<Algorithm D> When the error is 1.5% or less of the rated output, the following algorithm D is used.
[0099]
(1) If the current load average is larger than the target load average, the offset value is reduced. The adjustment amount is 0.006% of the rated output.
(2) If the current load average value is smaller than the target load average value, increase the offset value. The adjustment amount is 0.006% of the rated output.
(3) If the current load average value is the same as the target load average value, the offset is left as it is.
[0100]
Here, the rated output refers to the larger one of the absolute value of the maximum value of the target load and the absolute value of the minimum value of the target load.
[0101]
Therefore, the flow of the process for determining the offset correction amount is the same for both algorithms C and D, and only the numerical value of the adjustment amount is different. As described above, the present invention defines the "algorithm" by considering that the algorithm is different even in the case of only the difference in the usage data. The values of the respective adjustment amounts of 0.15% and 0.006% of the rated output are empirically obtained by experiments, but are not limited to these values. Further, the error value of 1.5% of the rated output, which is a criterion value for switching between the algorithms C and D, is not limited to this, and another value may be used.
[0102]
In the above example, a plurality of switching reference values (error boundary values) that are 1.5% of the rated output are provided, and the adjustment amount is prepared by adding another numerical value. Multi-stage adaptive proportional control that performs the above switching may be used.
[0103]
Further, the amplification factor correction / zero point correction calculation means 78 always keeps the automatic offset control (AOC: Auto offset control) valid even when the AGC is invalidated. That is, during the test, the load average value always matches or substantially matches the target value. The experimenter can select the valid / invalid of AGC by using the “AGC valid” button 360 on the in-test screen 300 of FIG. In the fatigue tester 10 of the present embodiment, since the average value is adjusted once before the test, the error of the average value can be kept small immediately after the start of the test. Therefore, the offset adjustment amount actually used may be almost the value of the algorithm D.
[0104]
The amplification factor correction means 79 and the zero point correction means 80 store the calculation results of the amplification factor correction / zero point correction calculation means 78 in a memory, and perform the amplification factor and zero point correction processing based on the calculation results. is there. Since the processing by the amplification factor correction / zero point correction calculation means 78 is performed for each cycle of the waveform, the content of the correction processing by the amplification rate correction means 79 and the zero point correction means 80 is updated for each cycle of the waveform.
[0105]
The counter 75 performs a process of counting the number of repetitions necessary for the fatigue test and a process of a counter limit. The counter limit is a function to stop the test when the number of test repetitions reaches a specified value. The specified value is a value input by the experimenter through the input section 233 of the number of times of discontinuation on the test condition setting screen 200 in FIG.
[0106]
The limiter 76 performs processing of a maximum limiter, a minimum limiter, a gain oscillation prevention limiter, and a test piece breakage detection mechanism.
[0107]
The maximum limiter is set when the maximum value detected by the peak bottom hold 77 exceeds the value set in advance before the test, while the minimum limiter is set when the minimum value detected in the peak bottom hold 77 is set before the test. When the value falls below the set value, the test operation is stopped to prevent the abnormal load from being repeated. The value set in advance before the test is a value calculated based on the value input by the experimenter in the input section 231 of the allowable excessive error on the test condition setting screen 200 in FIG.
[0108]
The gain oscillation prevention limiter has a function of preventing the output from being increased without limit by the automatic tuning and making the test unstable. The experimenter sets a limiter based on the value input in the allowable maximum gain input section 232 of the test condition setting screen 200 in FIG.
[0109]
The test piece rupture detection mechanism detects the rupture of the test piece 1 by sensing a sudden change in the response load waveform, and stops the fatigue test at the moment when the test piece 1 ruptures. This function protects the machine 10 itself.
[0110]
The external processing device 90 includes a processing unit 90A configured by a computer and performing various processes not directly related to control performance, an input unit 96 such as a keyboard and a mouse, and a display unit 97 such as a liquid crystal display and a CRT display. It is provided with. Further, for example, an output unit such as a printer or a plotter may be appropriately provided.
[0111]
The processing unit 90A includes a standby screen display / input reception processing unit 91, a test condition setting screen display / input reception processing unit 92, a test screen display / input reception processing unit 93, a reciprocal operation forced invalidation unit 94, And an input parameter auditing means 95.
[0112]
The standby screen display / input reception processing means 91 performs processing for displaying the standby screen 100 of FIG. 4 used when the actuator unit 40 is operated in a state other than during the test, and performs processing using the standby screen 100. This is a process for receiving an operation input to the actuator unit 40 by the experimenter.
[0113]
The test condition setting screen display / input reception processing means 92 performs a process of displaying the test condition setting screen 200 of FIG. 5 for setting test conditions, and a test condition by an experimenter performed using the test condition setting screen 200. The processing for accepting the setting input is performed. When the experimenter inputs necessary numerical values on the test condition setting screen 200 of FIG. 5 and instructs the determination, the input test conditions are transmitted to the DSP controller 70 by the test condition setting screen display / input reception processing means 92. Are automatically converted into parameters which can be interpreted by the control program of the first embodiment, and transferred to the DSP controller 70
[0114]
The in-test screen display / input reception processing means 93 displays the in-test screen 300 of FIG. 6 for monitoring the test status during the test, and receives the input by the experimenter performed using the in-test screen 300. Is what you do. When an error occurs during the test and the test is stopped, the screen display / input reception processing means 93 during the test communicates with the control program of the DSP controller 70, investigates the cause, and performs a process of reporting. Do.
[0115]
The reciprocal operation forcibly invalidating means 94 performs a process of forcibly invalidating an operation that should not be performed or an operation that should not be performed, while a certain operation is being performed. For example, during the test, the parameters of the test conditions cannot be changed.
[0116]
The input parameter auditing unit 95 performs a process of inspecting whether parameters (test conditions and the like) input by the experimenter are abnormal. For example, inconsistent parameter inputs on the test condition setting screen 200 in FIG. 5 are monitored.
[0117]
Each of the units 91 to 95 included in the processing unit 90A is a central processing unit provided inside a computer main body (including not only a personal computer but also a higher model thereof) constituting the external processing device 90. It is realized by a device (CPU) and one or a plurality of programs that define an operation procedure of the CPU.
[0118]
In the present embodiment as described above, a fatigue test for acquiring ultra-high cycle range data is performed using the fatigue tester 10 as follows.
[0119]
First, the experimenter performs the centering operation of the main body 11 of the fatigue tester 10 using the centering dummy test piece before performing the fatigue test. 2 and 3, in the centering operation, first, a dummy test piece for centering is attached to the lower (piston 41 side) grip portion 25. At this time, the lower end 2B of the dummy test piece for centering is inserted into the insertion hole 32 formed in the test piece holder 25A, and the bolt 34 is tightened. The lower end 2B of the dummy test piece is pressed down and fixed.
[0120]
Next, the horizontal position of the load cell 21 is adjusted such that the upper end 2A of the dummy test piece for alignment is inserted into the insertion hole 31 formed in the test piece holder 24A of the grip portion 24 on the upper side (the load cell 21 side). I do.
[0121]
Subsequently, after adjusting the horizontal position of the load cell 21, the load cell 21 is fixed with the bolt 26 and the lock nut 30 is tightened. Finally, the dummy specimen for alignment is removed.
[0122]
The above alignment work can be performed in about several minutes, and the operation time can be remarkably reduced as compared with the case where a strain gauge is pasted on a test piece and the alignment work is conventionally performed. After the centering operation, no restraint force is applied to the test piece 1 from the side surface, no matter how many times the test piece 1 for the fatigue test is attached at random. Therefore, unlike the conventional case, this alignment work does not need to be performed for each fatigue test.
[0123]
After performing the alignment operation using the dummy specimen for alignment as described above, the experimenter attaches the test piece 1 to the test piece mounting portion 20 of the main body 11 of the fatigue tester 10 in order to perform a fatigue test. Attach. At this time, the experimenter uses the standby screen 100 of FIG. 4 displayed on the screen of the display means 97 by the standby screen display / input reception processing means 91 of the external processing device 90 to mount the test piece 1. The operation of the piston 41 required for is performed.
[0124]
In FIG. 4, the standby screen 100 includes a feedback value display unit 110, a test condition display unit 120, a piston control unit 130, a "communication end" button 140, a "test condition setting" button 150, and a "test A “to console” button 160 and a “numeric offset input” button 170 are provided.
[0125]
The feedback value display section 110 is provided with a display section 111 for a load obtained from a detection signal of the strain gauge 22, and a display section 112 for a load stress obtained by converting the load into a test piece diameter. The conversion process into the stress value is performed by the standby screen display / input reception processing means 91.
[0126]
The test condition display section 120 includes display sections 121 to 124 for a maximum absolute stress, a test stress ratio, a test piece diameter, and a test frequency. These display values are values entered by the experimenter on the test condition setting screen 200 in FIG. 5 by clicking the “test condition setting” button 150.
[0127]
The piston control unit 130 includes an up button 131 for moving the piston 41 forward (up), a down button 132 for moving the piston 41 backward (down), a neutral button 133 for moving the piston 41 to the center position, and a A forward amount display section 134 for displaying the forward amount (rising amount) as a bar, a retreat amount displaying section 135 for displaying the retreat amount (lowering amount) of the piston 41 as a bar, and a valve zero for inputting the adjustment amount of the zero point of the servo valve 50. An adjustment input section 136 and a “Set” button 137 for actually setting the value input by the valve zero adjustment input section 136 are provided. Since the zero point of the servo valve 50 is normally shifted to the safe side, the zero point adjustment is performed to correct this in advance and perform precise control.
[0128]
The “communication end” button 140 is a button for terminating communication with the DSP controller 70, and the “test condition setting” button 150 is a button for moving to the test condition setting screen 200 in FIG. The "to" button 160 is a button for moving to the in-test screen 300 in FIG. 6, and the "numeric offset input" button 170 is forcibly setting the zero point (offset) to a certain value at the time of adjustment before the start of the test or the like. This button is used when setting.
[0129]
The experimenter also sets test conditions before the test. In this case, the experimenter clicks a “test condition setting” button 150 on the standby screen 100 of FIG. Then, the test condition setting screen display 200 shown in FIG. 5 is displayed on the screen of the display means 97 of the external processing device 90 by the test condition setting screen display / input reception processing means 92.
[0130]
In FIG. 5, a test condition setting screen 200 includes a main condition setting unit 210 for setting main conditions of the test conditions, an advanced condition setting unit 220 for setting advanced conditions of the test conditions, and various types of test conditions. A limiter setting unit 230 for setting a limiter value, a “cancel” button 240 for canceling an input in each of the setting units 210, 220, 230, and a condition for actually setting conditions input in each of the setting units 210, 220, 230 "Set condition" button 250 is provided.
[0131]
The main condition setting section 210 is provided with input sections 211 to 214 for a maximum absolute stress, a test stress ratio, a test piece diameter, and a test frequency, and a compression-compression for checking when performing a compression-compression test. A test selection check input unit 215 is provided. The values of the maximum absolute stress, the test stress ratio, and the test piece diameter input here are the sine wave amplitude A of the attained target load in the aforementioned equation (1). _t And sine wave average (zero) OFF _t Is used in the calculation determination process of This calculation determination processing is performed by the test condition setting screen display / input reception processing means 92. The value of the test frequency input here is set as the value of F in the above-described equation (1).
[0132]
The altitude condition setting unit 220 includes input units 221 to 223 for load cell conversion constant, vacuum bias, and default gain. The load cell conversion constant indicates the relationship between the load applied to the load cell 21 and the output voltage of the strain gauge 22, and is input according to the calibration result of the load cell 21. Sine wave amplitude A of load _t And sine wave average (zero) OFF _t Is used in load-voltage conversion processing in various processing such as calculation determination processing. The default gain sets an initial value of the amplification factor (gain).
[0133]
The limiter setting section 230 is provided with input sections 231 to 233 for the permissible excessive error, permissible maximum gain, and number of repetition of discontinuation. These input values are used for various limit processes performed by the limiter 76 and the counter 75.
[0134]
When the experimenter finishes the input in each of the setting sections 210, 220, and 230 and clicks the "set condition" button 250, the input condition is set, and the screen returns to the standby screen 100 of FIG. Then, when starting the test, the experimenter clicks a “To test console” button 160 on this screen 100. Then, the screen under test 300 of FIG. 6 is displayed on the screen of the display means 97 of the external processing device 90 by the screen under test display / input reception processing means 93.
[0135]
In FIG. 6, a test condition screen 310 for displaying test conditions, a test status numerical display 320 for numerically displaying the test status, and a stress display based on the actually measured load as the test status are displayed on the in-test screen 300 in a graph. A test status graph display unit 330 for performing the test is provided.
[0136]
The test condition display section 310 is provided with display sections 311 to 314 for maximum absolute stress, test stress ratio, test piece diameter, and test frequency. These display values are values input by the experimenter on the test condition setting screen 200 in FIG.
[0137]
The test status numerical display unit 320 includes a count display unit 321 that displays the count value of the counter 75, a gain display unit 322 that displays the current gain, and what percentage of the rated input of the servo valve 50 is used. An output LV display section 323 for displaying an output level of "(% of the maximum flow rate)" and a test error display section 324 are provided. The test error displayed here means (actual load amplitude−target load amplitude) / target load amplitude × 100 (%).
[0138]
The test situation graph display section 330 displays a waveform of stress calculated from the actual load (a waveform in which the horizontal axis represents time and the vertical axis represents stress). The conversion process from the load value to the stress value at this time is performed by the screen display / input reception processing means 93 during the test.
[0139]
The display contents of the test status numerical value display unit 320 and the test status graph display unit 330 are updated periodically by the screen display / input reception processing unit 93 during the test.
[0140]
In addition, on the screen 300 during the test, an “offset automatic adjustment” button 340 for automatically adjusting the offset, a “test stop” button 350 for stopping the test, an “AGC enable” button 360 for enabling the AGC, and a counter 75 are provided. A "counter reset" button 370 for resetting the count value of the "", an "unloading" button 380 for unloading, and a "go to main console" button 390 for moving to the standby screen 100 of FIG. 4 are provided. I have.
[0141]
When the test is actually performed, the offset is statically adjusted up to the offset value of the target load, and then the sum is added to superimpose the sine waveform. The “automatic offset adjustment” button 340 is a button for automatically bringing the load statically to the offset value before the start of the test.
[0142]
If the "AGC validity" button 360 is not clicked, the multi-stage adaptive proportional control does not become valid, and only the proportional control is performed. In this case, the values of the amplification factor (gain) and the zero point (offset) become constant values, and even if the actual load deviates from the target load due to an external factor, the operation of correcting the amplification factor and the zero value is adapted accordingly. Is not done.
[0143]
According to this embodiment, the following effects can be obtained. That is, the amplification factor correction / zero correction calculation means 78 performs amplification based on the degree of convergence of the actual load signal (the detection signal of the strain gauge 22) to the target value signal when performing the calculation processing relating to the amplification factor and zero correction. Since the algorithm of the calculation process related to the correction of the gain is configured to be switched stepwise, when the detection signal converges to the target value signal to some extent, the algorithm related to the correction of the amplification factor is switched, so that the target value signal of the detection signal is changed. Convergence degree can be increased. Therefore, the test accuracy can be improved.
[0144]
Further, the amplification factor correction / zero point correction calculation means 78 is configured to switch not only the amplification factor but also the algorithm of the calculation process relating to the correction of the zero point stepwise according to the degree of convergence of the detection signal to the target value signal. Therefore, the degree of convergence of the detection signal to the target value signal can be further increased, and the test accuracy can be further improved.
[0145]
Further, the amplification factor correction / zero correction calculation means 78 is configured to determine whether or not to switch the algorithm for each cycle of the waveform, so that the algorithm can be switched at an appropriate timing. Therefore, the convergence speed can be improved, and the test accuracy can be further improved.
[0146]
Specifically, assuming that the convergence degree of the error between the target value signal and the detection signal is, for example, about ± 1% in the conventional adaptive proportional control, the multi-stage adaptive proportional control of the present embodiment is ± 0.1% Can be converged within.
[0147]
Since the fatigue tester 10 includes the DSP controller 70 and the external processing device 90 as the control means 60, the DSP controller 70 includes arithmetic processing (target value signal, load signal, Comparison, amplification factor correction, zero point correction, peak bottom hold, and calculation of the amplification factor and zero point correction for performing multi-stage adaptive proportional control). Calculations that are not directly related to the operation (operations that convert the feedback voltage to load, numerical display of stress, graph display of stress, bar display of piston movement, arrow display of piston operation buttons, etc. Computational processing relating to an interface for making display easy to handle). That is, it is possible to completely separate an arithmetic processing program directly related to control performance from an arithmetic processing program not directly related to control performance, and to separate hardware for executing each of these programs.
[0148]
For this reason, the processing load on the DSP controller 70 can be reduced, so that the processing speed of arithmetic processing directly related to control performance such as responsiveness, load accuracy, and convergence to disturbance can be improved. Can be improved.
[0149]
Also, the external processing device 90 includes a standby screen display / input reception processing unit 91, a test condition setting screen display / input reception processing unit 92, and a test screen display / input reception processing unit 93. In each scene of the test and its preparation, each of the three screens of the standby screen 100 in FIG. 4, the test condition setting screen 200 in FIG. 5, and the test screen 300 in FIG. Only the display of information necessary for each scene can be confirmed, and only the input work required for each scene can be performed. Therefore, the experimenter only needs to perform the minimum necessary operations in each stage of the test and its preparation, so that there is no need to perform extra operations or refer to extra information to eliminate the need to consider extra things. Operability can be improved. In addition, since operability can be improved, occurrence of erroneous recognition or erroneous operation can be avoided or suppressed, and test accuracy can be improved.
[0150]
Then, by the standby screen display / input reception processing means 91, the up button 131 and the down button 132 are displayed as arrows in the piston control section 130 of the standby screen 100 in FIG. Since the portion 135 is displayed as a bar, the experimenter can intuitively operate the piston 41. In addition, erroneous operations can be avoided or suppressed. Further, since the feedback value display unit 110 is provided and the stress is displayed, the experimenter can easily confirm the current load state of the load.
[0151]
The test condition setting screen display / input reception processing means 92 can receive the input of the maximum absolute stress, the stress ratio, and the test piece diameter on the test condition setting screen 200 of FIG. Therefore, the experimenter can use only commonly used parameters such as stress, stress ratio, and test piece diameter, so that the operability of the fatigue tester 10 can be improved, and knowledge of the fatigue tester and control can be improved. Even a non-experimenter can easily perform a fatigue test.
[0152]
Further, since the stress display is performed in the test status graph display section 330 of the test-in-test screen 300 of FIG. It can be grasped intuitively. Further, the experimenter can appropriately perform the fatigue test under the set conditions only by pressing the buttons 340 to 390.
[0153]
Since the external processing device 90 includes the reciprocal operation forced invalidation means 94, erroneous operation can be prevented.
[0154]
Further, since the external processing device 90 includes the input parameter auditing means 95, the safety of the test can be improved.
[0155]
Furthermore, in the fatigue tester 10, since the parallelism of each surface of each component of the test piece 1 and the main body 11 is improved, it is possible to suppress the occurrence of an uneven load. At the same time, the fitting between the end portions 1A and 1B of the test piece 1 and the upper and lower grip portions 24 and 25 was loosened (see FIG. 3). It is possible to prevent the restraining force from being applied from the outer peripheral surfaces 1E and 1F) of 1A and 1B, and it is possible to suppress the occurrence of the uneven load. For this reason, the test accuracy can be improved. Usually, when the fit is loosened, the lateral displacement of the test piece 1 during the fatigue test is concerned. However, since the parallelism of each surface of each component of the test piece 1 and the main body 11 is improved, 1 can be prevented from being applied with a force causing lateral displacement.
[0156]
Since the alignment work is performed using the dummy alignment test piece having the ends 2A and 2B larger than the ends 1A and 1B of the test piece 1 used in the actual test, the alignment work can be performed accurately. In addition to being able to do so, the loose fitting described above can be easily realized. In addition, if the alignment operation is performed once using the alignment dummy test piece, a plurality of tests can be performed as it is, so that the labor of the experimenter can be reduced.
[0157]
In order to confirm the effect of the present invention, an experiment for measuring the partial stress Δσ was performed in the following procedure. First, the alignment test of the fatigue tester 10 is performed using the dummy test piece for alignment. Next, the test piece 1 having a total of three strain gauges affixed to a position obtained by dividing the outer periphery of the test piece central portion into three is attached to the test piece mounting portion 20. At this time, the value of the strain gauge is not referred to. Subsequently, a static stress of ± 400 MPa is applied to the test piece 1. Finally, the partial stress Δσ is calculated from the value of the strain gauge. Then, the above measurement was performed several times.
[0158]
The above measurement results were as follows. The bias stress Δσ when the applied stress was ± 400 MPa was 3.2 to 3.9 MPa. The ratio of Δσ is 0.8 to 2.3% with respect to the applied stress. This value does not affect the fatigue test result at all. Further, in the fatigue tester (fatigue tester provided with a spherical bearing) described in the above-mentioned Patent Document 1 by the present applicant, the ratio of Δσ to the applied stress of 400 MPa is 3.5 to 7.4%. Therefore, it was found that the fatigue test machine 10 of the present embodiment was able to significantly reduce the unbalanced load, and the effect of the present invention was remarkably shown.
[0159]
It should be noted that the present invention is not limited to the above embodiment, and modifications and the like within a range that can achieve the object of the present invention are included in the present invention.
[0160]
That is, in the above-described embodiment, the amplification factor correction / zero correction calculation unit 78 is configured to switch the algorithm of the calculation process regarding the correction of both the amplification factor and the zero in a stepwise manner. Alternatively, the configuration may be such that the algorithm is switched stepwise only for the amplification factor. However, if the algorithm is switched stepwise for both the amplification factor and the zero point as in the above-described embodiment, the test accuracy can be further improved.
[0161]
【The invention's effect】
As described above, according to the present invention, the amplification factor correction / zero correction calculation means compares the waveform of the detection signal with the waveform of the target value signal, and calculates the amplification and zero correction based on the comparison result. When performing the processing, the algorithm of the calculation processing concerning the correction of the amplification factor is switched stepwise according to the degree of convergence of the detection signal to the target value signal. By switching the algorithm related to the correction of the above, the degree of convergence of the detection signal to the target value signal can be increased, and the effect of improving the test accuracy can be achieved.
[0162]
Further, according to the present invention, an external processing device provided separately from the digital controller allows display processing of three screens, a standby screen, a test condition setting screen, and a screen under test, and input of data using these screens. Since the reception process is performed, the operability can be improved, the operation burden on the experimenter can be reduced, and the occurrence of erroneous recognition or erroneous operation can be avoided or suppressed, thereby improving the test accuracy. is there.
[0163]
Further, according to the present invention, since the parallelism of each surface of the test piece and the component parts of the test machine main body is improved, and the fitting between the end portion of the test piece and the grip portion is loosened, the occurrence of an uneven load occurs. And the test accuracy can be improved.
[Brief description of the drawings]
FIG. 1 is an overall configuration diagram of a fatigue test machine according to an embodiment of the present invention.
FIG. 2 is a cross-sectional view of a test piece mounting portion constituting a main body of the fatigue tester of the embodiment.
FIG. 3 is an enlarged cross-sectional view of a main part of a test piece mounting portion of the embodiment.
FIG. 4 is a view showing an example of a standby screen associated with processing by an external processing device constituting control means of the fatigue tester of the embodiment.
FIG. 5 is an exemplary view of a test condition setting screen associated with processing by an external processing device that constitutes control means of the fatigue tester of the embodiment.
FIG. 6 is a view showing an example of a screen during a test associated with processing by an external processing device which constitutes control means of the fatigue tester of the embodiment.
[Explanation of symbols]
1 Test piece
1A Upper end of test piece
1B Lower edge of test piece
1C Upper end face of test piece
Lower end face of 1D specimen
1E Outer peripheral surface of upper end of test piece
1F Outer peripheral surface of lower end of test piece
10 Fatigue testing machine
11 Body
20 Test piece mounting part
24, 25 gripping part
31A, 32A Test piece contact surface
35, 36 gap
40 Actuator section
60 control means
70 DSP controller which is a digital controller
72 Servo amplifier constituting control signal generating means
78 Amplification rate correction / zero point correction calculation means
79 Amplification rate correction means
80 Zero point correction means
90 External processing unit
91 Standby screen display / input reception processing means
92 Test condition setting screen display / input reception processing means
93 Screen display / input acceptance processing means during test

Claims (7)

A main body having a test piece mounting part for mounting a test piece and an actuator part for applying a load to the test piece, and a feedback of a detection signal corresponding to the load applied to the test piece to control the operation of the actuator part Control means for performing feedback control to send a control signal of the main body to the main body,
The control unit is configured to include a digital controller that performs the feedback control by digital processing,
This digital controller
Control signal generating means for generating the control signal according to a deviation amount between the detection signal and the target value signal,
Amplification factor correction / zero correction calculation means for comparing a waveform of the detection signal with a waveform of the target value signal and performing a calculation process relating to an amplification factor and a zero correction used for the generation processing of the control signal based on the comparison result When,
Amplification factor correction means for performing the amplification factor correction processing based on the calculation result by the amplification factor correction / zero point correction calculation means;
Zero point correction means for performing the zero point correction processing based on the calculation result by the amplification factor correction / zero point correction calculation means,
The amplification factor correction / zero correction calculation means is configured to switch an algorithm of a calculation process for correction of the amplification factor in a stepwise manner in accordance with a degree of convergence of the detection signal to the target value signal. Fatigue testing machine. The fatigue tester according to claim 1,
The amplification factor correction / zero correction calculation means is configured to switch an algorithm of a calculation process regarding the correction of the zero in a stepwise manner according to the degree of convergence of the detection signal to the target value signal. Fatigue testing machine. The fatigue tester according to claim 1 or 2,
The amplification factor correction / zero correction calculation means compares the periodically changing waveform of the detection signal with the periodically changing waveform of the target value signal for each one cycle of the waveform, and obtains the comparison result. Also, based on the amount of deviation between the two waveforms, a calculation process relating to the amplification factor and the correction of the zero point is performed for each cycle of the waveform, and whether or not to switch the algorithm when performing this calculation process is determined for each cycle of the waveform. A fatigue tester characterized in that it has a configuration to perform. A main body having a test piece mounting part for mounting a test piece and an actuator part for applying a load to the test piece, and a feedback of a detection signal corresponding to the load applied to the test piece to control the operation of the actuator part Control means for performing feedback control to send a control signal of the main body to the main body,
The control means,
A digital controller that performs the feedback control by digital processing;
An external processing device that is connected to the digital controller and performs processing other than the processing related to the feedback control by transmitting and receiving information to and from the digital controller,
The external processing device,
A standby screen used to display a standby screen used when operating the actuator unit in a state other than during a test, and a process of receiving an operation input to the actuator unit by an experimenter performed using the standby screen. Display / input reception processing means;
A process for displaying a test condition setting screen for setting test conditions, and a process for receiving a test condition setting input by the experimenter performed by using the test condition setting screen. A test condition setting screen display / input receiving process. Means,
A process of displaying an in-test screen for monitoring the test status during the test, and an in-test screen display / input reception processing means for performing a process of receiving an input by the experimenter performed using the in-test screen. Characterized fatigue testing machine. The fatigue tester according to claim 4,
The test condition setting screen display / input reception processing means includes, as the test condition on the test condition setting screen, a combination of a maximum stress and a minimum stress, a combination of a maximum stress and a stress ratio, and a combination of a minimum stress and a stress ratio. Any combination, and the configuration to accept the input of the specimen diameter,
The fatigue tester, wherein the under-test screen display / input reception processing means displays a stress graph as the test status on the under-test screen. An actuator for applying a load to the test piece, and a test piece mounting part for mounting the test piece in a state of being arranged in a direction along a load direction by the actuator part, wherein the test piece mounting part includes the test piece In a fatigue test machine in which grip portions for gripping both end portions of both sides are provided, and each of these grip portions is formed with a test piece contact surface to which the both end surfaces of the test piece are respectively contacted,
The end faces on both sides of the test piece satisfy the parallelism of 0.01, and serve to regulate the parallelism between the test piece contact surfaces of the gripping portions facing each other among the surfaces of the testing machine main body component. Are also finished in a state that satisfies the parallelism of 0.01,
In a state where the test piece is mounted on the test piece mounting portion, a gap is formed between an outer peripheral surface of each end of the test piece and each of the grip portions. testing machine. The fatigue tester according to claim 6,
The gap between the outer peripheral surface of each end of the test piece used in the actual test and the fitting of each gripping portion is the outer peripheral surface of each end of the dummy test piece for alignment used in the alignment work performed before the test. A fatigue tester characterized in that it is larger than a clearance of fitting with each of the grip portions.

Images