JP4032969B2

JP4032969B2 - Method and apparatus for determining presence or absence of surface shape in molding process simulation

Info

Publication number: JP4032969B2
Application number: JP2002380632A
Authority: JP
Inventors: 和慶藤井; 隆司杉山
Original assignee: Nissan Motor Co Ltd
Current assignee: Nissan Motor Co Ltd
Priority date: 2002-12-27
Filing date: 2002-12-27
Publication date: 2008-01-16
Anticipated expiration: 2022-12-27
Also published as: JP2004209500A

Description

【０００１】
【発明の属する技術分野】
本発明は、成形加工シミュレーションにより板材を塑性変形させたとき、その板材に面形状不良が生じるか否かを正確に判定するための成形加工シミュレーションにおける面形状不良有無判定方法及びその装置に関する。
【０００２】
【従来の技術】
従来、鍛造、圧延、プレス成形など、材料の塑性変形を伴う成形加工では、的確な素材形状、金型形状、加工条件の選定が要求される。この要求に短期間で効率的かつ安価に応えるために、有限要素法(ＦＥＭ)による数値シミュレーションが用いられる。数値シミュレーションの結果に基づいて、素材形状、金型形状、加工条件を設定すれば、実際の加工を行ったときに、所望の品質を備えた製品が得られる。
【０００３】
例えば、下記特許文献１では、金属板の成形過程を有限要素法で解析してひずみ分布及び応力分布を求め、これらの分布から加工不良の発生の有無や加工不良の発生場所を視覚的に判定し、この判定結果から最適な加工条件が設定できるようにしている。
【０００４】
【特許文献１】
特開平８−３３９３９６号公報
【０００５】
【発明が解決しようとする課題】
しかしながら、このような従来の手法では、加工不良として、破断が生じる危険性、しわが生じる危険性を視覚的に把握することはできるが、ひずみの小さな面形状不良(しわ、面ひずみ)までは判断することはできない。
【０００６】
本発明は、このような従来の手法の問題点を解消するために成されたものであり、成形加工シミュレーションを用いて板材を塑性変形させたとき、その板材に面形状不良が生じるか否かを正確に判定することができる成形加工シミュレーションにおける面形状不良有無判定方法及びその装置の提供を目的とする。
【０００７】
【課題を解決するための手段】
上記した課題を解決し、目的を達成するため、本発明にかかる成形加工シミュレーションにおける面形状不良有無判定方法では、まず、設定された成形加工条件で被成形品を擬似的に加工し、その加工過程における被成形品のひずみ分布を演算する。この演算によって被成形品の加工を開始してからその加工が終了するまでのひずみ分布がわかる。次に、演算されたひずみ分布に基づいて被成形品の各微小部分のひずみ履歴を演算する。すなわち、被成形品における時刻Ｔのひずみ分布と時刻Ｔから微小時間Δｔ前のひずみ分布から各微小部分の移動距離によるひずみの増分Δεを求め、ひずみの増分Δεが０よりも大きい微小部分は、時刻Ｔから微小時間Δｔ後のひずみの増分Δεも０よりも大きくなると予測する一方、ひずみの増分Δεが０よりも小さい微小部分は、時刻Ｔから微小時間Δｔ後のひずみの増分Δεも０よりも小さくなると予測し、予測されたひずみ分布に基づいて前記被成形品の各微小部分のひずみが時間の進行とともにその材料を引き伸ばす方向に生じているのか、または、その材料を縮める方向に生じているのかを認識する。このように被成形品の各微小部分のひずみ履歴を演算することによって時間を追うごとに各微小部分がどのようにひずんで行くかがわかる。そして最後に、演算されたひずみ履歴から被成形品の面形状不良有無を判定する。
【０００８】
また、上記した課題を解決し、目的を達成するため、本発明にかかる成形加工シミュレーションにおける面形状不良有無判定装置は、成形加工条件を設定する設定手段と、設定された成形加工条件で被成形品を擬似的に加工する加工手段と、加工過程における前記被成形品のひずみ分布を演算するひずみ分布演算手段と、演算されたひずみ分布を記憶する記憶手段と、記憶されたひずみ分布に基づいて前記被成形品の各微小部分のひずみ履歴を演算するひずみ履歴演算手段と、演算されたひずみ履歴から前記被成形品の面形状不良有無を判定する判定手段と、を有し、前記ひずみ履歴演算手段は、前記ひずみ分布に基づいて被成形品における時刻Ｔのひずみ分布と時刻Ｔから微小時間Δｔ前のひずみ分布から各微小部分の移動距離によるひずみの増分Δεを求める手段と、ひずみの増分Δεが０よりも大きい微小部分は、時刻Ｔから微小時間Δｔ後のひずみの増分Δεも０よりも大きくなると予測する一方、ひずみの増分Δεが０よりも小さい微小部分は、時刻Ｔから微小時間Δｔ後のひずみの増分Δεも０よりも小さくなると予測する手段と、を有し、前記ひずみ分布に基づいて前記被成形品の各微小部分のひずみが時間の進行とともにその材料を引き伸ばす方向に生じているのか、または、その材料を縮める方向に生じているのかを認識する。
【０００９】
本発明の成形加工シミュレーションにおける面形状不良有無判定方法及びその装置によれば、被成形品を擬似的に加工したときの各微小部分の移動距離によるひずみ分布から各微小部分のひずみ履歴を演算し、そのひずみ履歴に基づいて面形状不良の有無を判定させるようにしたので、成形加工シミュレーションを用いて板材を塑性変形させたとき、その板材に面形状不良が生じるか否かを正確に判定することができる。
【００１０】
【発明の実施の形態】
以下に添付図面を参照して、本発明にかかる成形加工シミュレーションにおける面形状不良有無判定方法及びその装置の好適な実施の形態を詳細に説明する。図１は、本発明にかかる面形状不良有無判定装置のブロック図、図２は、図１の面形状不良有無判定装置によって実行される面形状不良有無判定方法の手順を示すフローチャートである。
【００１１】
本発明にかかる面形状不良有無判定装置は、加工条件を入力する加工条件入力部１０、加工条件に従って成形加工シミュレーションを実行し被成形品のひずみ分布を演算する成形加工シミュレーション実行部１５、演算されたひずみ分布を記憶するひずみ分布記憶部２０、ひずみ分布に基づいてある時間内のひずみの増分を求めるとともに以降のひずみの増分を予測してひずみ履歴を演算し、ひずみが時間の進行とともに材料を縮める方向に生じていれば面形状不良有りと判定する面形状ひずみ演算部２５、ひずみ履歴の演算対象領域を指定する領域指定部３０、判定結果を表示する判定結果表示部３５を備えている。
【００１２】
面形状不良有無判定装置は、図２のフローチャートに示す手順で面形状不良有無判定を行う。まず、操作者は加工条件入力部１０に成形加工条件を設定する。成形加工シミュレーション実行部１５は、シミュレーションプログラムを実行し設定された成形加工条件で被成形品を擬似的に加工する。成形加工シミュレーション実行部１５は、加工過程における成形品のひずみ分布を演算する。例えば、成形加工がプレス加工であれば、プレスを開始してから終了するまで、板材全体に生じるひずみ分布を単位時間ごとに演算する。演算されたひずみ分布はひずみ分布記憶部２０に記憶する(Ｓ１)。
【００１３】
面形状ひずみ演算部２５は、ひずみ分布記憶部２０に記憶されているひずみ分布を取り出し、そのひずみ分布に基づいて、ある時間内における被成形品の各微小部分のひずみ履歴を演算する。なお、領域指定部３０でひずみ履歴の演算対象領域が指定されているときには、面形状ひずみ演算部２５は、指定されている演算対象領域に対してひずみ履歴を演算する。
【００１４】
面形状ひずみ演算部２５は、ひずみ分布に基づいて被成形品の各微小部分のひずみが時間の進行とともにその材料を引き伸ばす方向に生じているのか、または、その材料を縮める方向に生じているのかを認識するためにひずみ履歴を求める。
【００１５】
ひずみ履歴は具体的には次のようにして求める。面形状ひずみ演算部２５は、被成形品における時刻Ｔのひずみ分布と時刻Ｔから微小時間Δｔ前のひずみ分布をひずみ分布記憶部２０から取り出し、時刻Ｔと時刻Ｔ＋Δｔの時間内における各微小部分のひずみの増分Δεを求める（Ｓ２）。面形状ひずみ演算部２５は、ひずみの増分Δεが０よりも大きい微小部分は、時刻Ｔから微小時間Δｔ後のひずみの増分Δεも０よりも大きくなると予測する一方、ひずみの増分Δεが０よりも小さい微小部分は、時刻Ｔから微小時間Δｔ後のひずみの増分Δεも０よりも小さくなると予測する(Ｓ３)。
【００１６】
面形状ひずみ演算部２５は、演算されたひずみ履歴から被成形品の面形状不良有無を判定する。すなわち、被成形品のいずれかの微小部分においてひずみの増分Δεが０よりも小さくなると予測されたときに面形状不良有りと判定する。ひずみの増分Δεが０よりも小さくなると予測されたということは、被成形品の各微小部分のひずみが時間の進行とともにその材料を縮める方向に生じていると考えられるからである(Ｓ４)。
【００１７】
面形状ひずみ演算部２５は、面形状不良有りと判定したときにはその旨を判定結果表示部３５に表示させ、一方、面形状不良無しと判定したときにはその旨を判定結果表示部３５に表示させる(Ｓ５)。
【００１８】
本発明にかかる成形加工シミュレーションにおける面形状不良有無判定方法及びその装置の概略の装置構成及び動作は以上のとおりである。次に、板材をプレス加工する場合の面形状不良有無判定装置の動作を、図３に示すフローチャートに基づいて詳細に説明する。
【００１９】
まず、操作者は加工条件入力部１０に成形加工条件を設定する。加工条件入力部１０はキーボードなどの入力端末装置でも良いし、成形加工条件を記憶しているデータベースでも良い。プレス加工の場合、設定される成形加工条件は、板材の材質、厚さ、大きさ、強度、応力−ひずみ特性、プレス速度、加圧力などである。加工条件入力部１０にキーボードなどの入力端末装置を用いる場合には、これらの成形加工条件を操作者が手入力する。また、加工条件入力部１０にデータベースを用いる場合には、これらの成形加工条件をそのデータベースに記憶させておく(Ｓ１１)。成形加工シミュレーション実行部１５は、これから擬似的な加工をしようとする板材の成形加工条件を加工条件入力部１０から入力する(Ｓ１２)。成形加工シミュレーション実行部１５は、プレスのシミュレーションプログラムを実行し入力した成形加工条件で被成形品を擬似的に加工する。例えば、図４(Ａ)に示してあるような正方形の板材を、同図(Ｂ)に示すような形状にプレス加工する(Ｓ１３)。
【００２０】
成形加工シミュレーション実行部１５は、プレス過程における板材のひずみ分布を非常に短い時間ごとに演算し、演算されたひずみ分布はひずみ分布記憶部２０に記憶する。例えば、プレスを開始してから０．１秒後に板材全体にどのような大きさのひずみが生じるのかを演算し、その演算結果を記憶する。この演算と記憶の処理は、プレスを開始してから終了するまで繰り返し行われる。なお、このひずみ分布を求める演算は、従来から使用されている有限要素法を用いることによって容易に行うことができるので、その演算の具体的な説明は省略する(Ｓ１４、Ｓ１５)。ここまでの処理によって、ひすみ分布記憶部２０には、プレスを開始してから終了するまでのひずみ分布が時刻ごとに記憶されることになる。なお、ひずみ分布のサンプリング時間を短く設定すれば、面形状不良の有無が高精度で判定できるようになる。成形加工シミュレーション実行部１５にどの程度のサンプリング時間を設定するかは、プレス成形品の製品形状の複雑さや、要求される判定精度などを勘案する。サンプリング時間は、プレスを開始してから終了するまで一律の時間で設定する必要はなく、プレス過程の一部の区間だけサンプリング時間を相対的に短くし、他の区間は相対的に長くするようにしても良い。
【００２１】
面形状ひずみ演算部２５は、ひずみ分布記憶部２０に記憶されているひずみ分布の中から、プレス開始Ｔ秒後のひずみ分布とプレス開始Ｔ−Δｔ秒後のひずみ分布とを取り出す。例えば、指定された時刻がプレス開始から１秒後であり、サンプリング時間Δｔが０．１秒であれば、面形状ひずみ演算部２５は、プレス開始後０．９秒後の板材のひずみ分布と１秒後の板材のひずみ分布を取り出すことになる（Ｓ１６）。面形状ひずみ演算部２５は、サンプリング時間Δｔだけずれた２つのひずみ分布から、最も大きいひずみを呈した最大主歪ε１と最も小さい歪みを呈した最小主歪ε２を求める。有限要素法では、図４のように板材にメッシュを形成し、板材に非常に多くの要素数と節点数を持たせているので、各節点がサンプリング時間Δｔの間にどの程度の距離移動したかを演算することによって、最大主歪ε１と最小主歪ε２を求めることができる。求めた主歪は、図５のグラフで示されるように、最大主歪ε１と最小主歪ε２の相互関係がわかるデータとして、面形状ひずみ演算部２５に記憶する(Ｓ１７)。なお、領域指定部３０でひずみ履歴の演算対象領域が指定されているときには、面形状ひずみ演算部２５は、指定されている演算対象領域に対して最大主歪ε１と最小主歪ε２を演算する。
【００２２】
面形状ひずみ演算部２５は、求めた最大主歪ε１と最小主歪ε２の相互関係から、板材の各微小部分のひずみが時間の進行とともに板材を引き伸ばす方向に生じているのか、または、板材を縮める方向に生じているのかがわかるので、プレス開始からＴ＋Δｔ秒後のひずみ分布を予測する。すなわち、面形状ひずみ演算部２５は、最小主歪の増分Δε２(図５参照)が０よりも大きい微小部分は、時刻Ｔ＋Δｔの時点における最小主歪の増分Δε２が０よりも大きくなると予測する一方、最小主歪の増分Δε２が０よりも小さい微小部分は、時刻Ｔ＋Δｔの時点における最小主歪の増分Δε２が０よりも小さくなると予測する(Ｓ１８)。
【００２３】
面形状ひずみ演算部２５は、プレス過程において、最小主歪の増分Δε２が０よりも大きいと予測されるか否かを、板材の微小部分ごとに判断する。図６に示すように、最小主歪の増分Δε２が０よりも大きいと予測されることは、最小主歪の増分Δε２が図の右方向（Ｂ方向）に移動することになるので、板材の各微小部分のひずみが時間の進行とともにその板材を引き伸ばす方向に生じていると考えられる。逆に、最小主歪の増分Δε２が０よりも小さいと予測されることは、最小主歪の増分Δε２が図の左方向（Ａ方向）に移動することになるので、板材の各微小部分のひずみが時間の進行とともにその板材を縮める方向に生じていると考えられる（Ｓ１９）。
【００２４】
面形状ひずみ演算部２５は、面形状不良（しわや面ひずみなど）有りと判定したときには（Ｓ１９：ＹＥＳ）その旨を判定結果表示部３５に表示させ（Ｓ２０）、一方、面形状不良無しと判定したとき（Ｓ１９：ＮＯ）にはその旨を判定結果表示部３５に表示させる（Ｓ２１）。この表示は、微小部分ごとに分けて行われる。例えば、自動車の車体パネルをプレスするシミュレーションに対して本発明の方法を適用すると、判定結果表示部３５には図７に示すように、面形状不良無しと判定された部分と面形状不良有りと判定された部分が色分けされた画像として表示される(Ｓ２２)。
【００２５】
以上のように、本実施の形態では、ひずみ履歴を求めることによって面形状不良の有無を判定したが、塑性変形時に被成形品の微小部分にかかる応力の大きさを求めることによって面形状不良の有無を判定するようにしても良い。
【００２６】
以上、本発明にかかる成形加工シミュレーションにおける面形状不良有無判定方法及びその装置によれば、成形加工シミュレーションを用いて板材を塑性変形させたとき、その板材に面形状不良が生じるか否かを正確に判定することができる。
【００２７】
また、ひずみ履歴の演算対象領域を指定した場合には、演算の対象領域が制限されるので、面形状不良有無の判定の処理を高速化することができる。
【００２８】
さらに、判定結果を表示するようにした場合には、面形状不良が生じる恐れのある領域と面形状不良が生じることのない領域を一目瞭然に表示することができる。
【図面の簡単な説明】
【図１】本発明にかかる面形状不良有無判定装置のブロック図である。
【図２】図１の面形状不良有無判定装置によって実行される面形状不良有無判定方法の手順を示すフローチャートである。
【図３】板材をプレス加工する場合の面形状不良有無判定装置の動作を示すフローチャートである。
【図４】プレス成形の一例を示す図である。
【図５】最大主歪ε１と最小主歪ε２の相互関係を説明するための図である。
【図６】面形状不良有無の判定基準の説明に供する図である。
【図７】面形状不良有無の表示例を示す図である。
【符号の説明】
１０…加工条件入力部、
１５…成形加工シミュレーション実行部、
２０…ひずみ分布記憶部、
２５…面形状ひずみ演算部、
３０…領域指定部、
３５…判定結果表示部。[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a surface shape defect presence / absence determination method and apparatus for forming process simulation for accurately determining whether or not a surface shape defect occurs in a plate material when the sheet material is plastically deformed by the forming process simulation.
[0002]
[Prior art]
Conventionally, in a forming process that involves plastic deformation of a material such as forging, rolling, or press forming, selection of an accurate material shape, mold shape, and processing conditions is required. In order to meet this requirement efficiently and inexpensively in a short period of time, numerical simulation by the finite element method (FEM) is used. If the material shape, mold shape, and processing conditions are set based on the result of the numerical simulation, a product having a desired quality can be obtained when actual processing is performed.
[0003]
For example, in Patent Document 1 below, a metal plate forming process is analyzed by a finite element method to obtain a strain distribution and a stress distribution, and from these distributions, it is visually determined whether or not a processing defect has occurred and where the processing defect has occurred. The optimum machining conditions can be set from the determination result.
[0004]
[Patent Document 1]
JP-A-8-339396
[Problems to be solved by the invention]
However, with such a conventional method, it is possible to visually grasp the risk of breakage and the risk of wrinkles as processing defects, but until the surface shape defect (wrinkle, surface strain) with small distortion It cannot be judged.
[0006]
The present invention has been made to solve the problems of the conventional technique, and whether or not a surface shape defect occurs in the plate material when the plate material is plastically deformed using a forming process simulation. It is an object of the present invention to provide a surface shape defect presence / absence determination method and apparatus therefor in a molding process simulation capable of accurately determining the above.
[0007]
[Means for Solving the Problems]
In order to solve the above-described problems and achieve the object, the surface shape defect presence / absence determination method in the molding process simulation according to the present invention first processes a workpiece under a set molding process condition in a pseudo manner, and performs the process. Calculate the strain distribution of the molded product in the process. By this calculation, the strain distribution from the start of the processing of the molded article to the end of the processing can be found. Next, the strain history of each minute portion of the molded product is calculated based on the calculated strain distribution. That is, the strain increment Δε due to the moving distance of each minute portion is obtained from the strain distribution at time T and the strain distribution before the minute time Δt from the time T, and the minute portion where the strain increment Δε is larger than 0 is obtained as follows: While it is predicted that the strain increment Δε after the micro time Δt from the time T is also larger than 0, the micro portion where the strain increment Δε is smaller than 0 also has the strain increment Δε after the micro time Δt from the time T. And, based on the predicted strain distribution, the strain of each minute part of the molded product is generated in the direction of stretching the material as time progresses, or is generated in the direction of shrinking the material. Recognize that Thus, by calculating the strain history of each minute portion of the molded product, it can be seen how each minute portion is distorted with time. Finally, the presence or absence of a surface shape defect of the molded product is determined from the calculated strain history.
[0008]
In addition, in order to solve the above-described problems and achieve the object, the surface shape defect presence / absence determination device in the molding process simulation according to the present invention includes a setting unit that sets molding process conditions, and a molding target under the set molding process conditions. Based on the stored strain distribution, the processing means for pseudo-processing the product, the strain distribution calculating means for calculating the strain distribution of the molded article in the processing process, the storage means for storing the calculated strain distribution wherein possess the strain history calculation means for calculating the strain history of each minute portion of the molded article, the calculated strain history determination means for determining surface shape defects whether the object to be molded article, wherein the strain history calculation Means is based on the strain distribution based on the strain distribution and the strain due to the movement distance of each minute portion from the strain distribution at the time T and the strain distribution before the time T from the time T. The means for obtaining the increment Δε and the minute portion where the strain increment Δε is greater than 0 are predicted to be larger than 0 after the minute time Δt from the time T, while the strain increment Δε is greater than 0. And a means for predicting that the strain increment Δε after the micro time Δt from the time T is also smaller than 0, and based on the strain distribution, the strain of each micro portion of the molded product is It is recognized whether the material is generated in the direction in which the material is stretched over time or in the direction in which the material is contracted .
[0009]
According to the surface shape defect presence / absence determination method and apparatus therefor in the molding process simulation of the present invention, the strain history of each minute part is calculated from the strain distribution due to the movement distance of each minute part when the workpiece is simulated. Since the presence or absence of surface shape defects is determined based on the strain history, it is accurately determined whether or not surface shape defects occur in the plate material when the plate material is plastically deformed using a molding process simulation. be able to.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Exemplary embodiments of a surface shape defect presence / absence determination method and its apparatus in a molding process simulation according to the present invention will be described below in detail with reference to the accompanying drawings. FIG. 1 is a block diagram of a surface shape defect presence / absence determination device according to the present invention, and FIG. 2 is a flowchart showing a procedure of a surface shape defect presence / absence determination method executed by the surface shape defect presence / absence determination device of FIG.
[0011]
The surface shape defect presence / absence determination apparatus according to the present invention is calculated by a machining condition input unit 10 for inputting machining conditions, a molding process simulation executing unit 15 for executing a molding process simulation according to the machining conditions and calculating a strain distribution of the molded product. The strain distribution storage unit 20 stores the strain distribution, calculates the increment of the strain within a certain time based on the strain distribution, calculates the strain history by predicting the subsequent strain increment, and calculates the strain as the time progresses. A surface shape distortion calculation unit 25 that determines that there is a surface shape defect if it occurs in the shrinking direction, a region specification unit 30 that specifies a region for calculation of strain history, and a determination result display unit 35 that displays a determination result are provided.
[0012]
The surface shape defect presence / absence determination apparatus performs surface shape defect presence / absence determination according to the procedure shown in the flowchart of FIG. First, the operator sets molding processing conditions in the processing condition input unit 10. The molding process simulation execution unit 15 executes a simulation program and pseudo-processes the molded product under the set molding process conditions. The molding process simulation execution unit 15 calculates the strain distribution of the molded product during the process. For example, if the forming process is a press process, the strain distribution generated in the entire plate material is calculated every unit time from the start to the end of the press. The calculated strain distribution is stored in the strain distribution storage unit 20 (S1).
[0013]
The surface shape strain calculation unit 25 takes out the strain distribution stored in the strain distribution storage unit 20, and calculates the strain history of each minute portion of the molded product within a certain time based on the strain distribution. In addition, when the calculation target area | region of the strain history is designated by the area | region designation | designated part 30, the surface shape distortion calculating part 25 calculates a strain history with respect to the designated calculation target area.
[0014]
Whether the surface shape strain calculation unit 25 causes the strain of each minute portion of the molded product based on the strain distribution in the direction of stretching the material with time, or in the direction of shrinking the material. Strain history is obtained in order to recognize.
[0015]
Specifically, the strain history is obtained as follows. The surface shape strain calculation unit 25 extracts the strain distribution at the time T and the strain distribution before the minute time Δt from the time T from the strain distribution storage unit 20, and calculates each minute portion within the time T and the time T + Δt. A strain increment Δε is obtained (S2). The surface shape strain calculation unit 25 predicts that the minute portion where the strain increment Δε is larger than 0 is predicted to be larger than 0 after the minute time Δt from the time T, while the strain increment Δε is larger than 0. Is also predicted that the strain increment Δε after the minute time Δt from the time T is also smaller than 0 (S3).
[0016]
The surface shape strain calculation unit 25 determines the presence or absence of a surface shape defect of the molded product from the calculated strain history. That is, when it is predicted that the strain increment Δε is smaller than 0 in any minute part of the molded product, it is determined that there is a surface shape defect. The fact that the strain increment Δε is predicted to be smaller than 0 is because the strain of each minute portion of the molded product is considered to be generated in the direction of shrinking the material with the progress of time (S4).
[0017]
When it is determined that there is a surface shape defect, the surface shape strain calculation unit 25 displays that fact on the determination result display unit 35, and when it determines that there is no surface shape defect, the surface shape distortion calculation unit 25 displays that fact on the determination result display unit 35 ( S5).
[0018]
The outline apparatus configuration and operation of the surface shape defect presence / absence determination method and apparatus in the molding process simulation according to the present invention are as described above. Next, the operation of the surface shape defect presence / absence determination device when pressing a plate material will be described in detail based on the flowchart shown in FIG.
[0019]
First, the operator sets molding processing conditions in the processing condition input unit 10. The processing condition input unit 10 may be an input terminal device such as a keyboard or a database storing molding processing conditions. In the case of press working, the molding process conditions to be set are the material, thickness, size, strength, stress-strain characteristics, press speed, pressure, and the like of the plate material. When an input terminal device such as a keyboard is used for the processing condition input unit 10, the operator manually inputs these molding processing conditions. Further, when a database is used for the processing condition input unit 10, these molding processing conditions are stored in the database (S11). The forming process simulation execution unit 15 inputs the forming process conditions of the plate material to be simulated from the processing condition input unit 10 (S12). The molding process simulation execution unit 15 executes a press simulation program and pseudo-processes the molded product under the input molding process conditions. For example, a square plate material as shown in FIG. 4A is pressed into a shape as shown in FIG. 4B (S13).
[0020]
The forming process simulation execution unit 15 calculates the strain distribution of the plate material in the pressing process every very short time, and stores the calculated strain distribution in the strain distribution storage unit 20. For example, what kind of strain is generated in the entire plate material 0.1 seconds after the start of pressing is calculated, and the calculation result is stored. This calculation and storage process is repeated from the start to the end of pressing. Note that the calculation for obtaining the strain distribution can be easily performed by using a conventionally used finite element method, and therefore a specific description of the calculation is omitted (S14, S15). Through the processing so far, the strain distribution storage unit 20 stores the strain distribution from the start to the end of the press for each time. If the sampling time of the strain distribution is set short, the presence or absence of surface shape defects can be determined with high accuracy. How much sampling time is set in the forming process simulation execution unit 15 takes into account the complexity of the product shape of the press-formed product and the required determination accuracy. It is not necessary to set the sampling time in a uniform time from the start to the end of the press, so that the sampling time is relatively shortened only in some sections of the pressing process and the other sections are relatively long. Anyway.
[0021]
The surface shape strain calculation unit 25 extracts the strain distribution after T seconds from the press start and the strain distribution after T-Δt seconds from the press start from the strain distributions stored in the strain distribution storage unit 20. For example, if the designated time is 1 second after the start of pressing and the sampling time Δt is 0.1 second, the surface shape strain calculating unit 25 calculates the strain distribution of the plate material 0.9 seconds after the start of pressing. The strain distribution of the plate material after 1 second is taken out (S16). The surface shape strain calculator 25 obtains the maximum principal strain ε1 exhibiting the largest strain and the minimum principal strain ε2 exhibiting the smallest strain from the two strain distributions shifted by the sampling time Δt. In the finite element method, a mesh is formed on the plate as shown in FIG. 4, and the plate has a very large number of elements and nodes, so how much distance each node has moved during the sampling time Δt. By calculating the above, the maximum principal strain ε1 and the minimum principal strain ε2 can be obtained. As shown in the graph of FIG. 5, the obtained main strain is stored in the surface shape strain calculation unit 25 as data for understanding the mutual relationship between the maximum main strain ε1 and the minimum main strain ε2 (S17). Note that when the calculation target region of the strain history is specified by the region specifying unit 30, the surface shape strain calculation unit 25 calculates the maximum main strain ε1 and the minimum main strain ε2 with respect to the specified calculation target region. .
[0022]
The surface shape strain calculation unit 25 determines whether or not the strain of each minute portion of the plate material is generated in the direction of stretching the plate material as time progresses from the correlation between the obtained maximum principal strain ε1 and minimum principal strain ε2. Since it can be seen whether it occurs in the shrinking direction, the strain distribution after T + Δt seconds from the start of pressing is predicted. That is, the surface shape strain calculation unit 25 predicts that the minimum principal strain increment Δε2 at time T + Δt is larger than 0 at a minute portion where the minimum principal strain increment Δε2 (see FIG. 5) is greater than zero. The minute portion where the minimum principal strain increment Δε2 is smaller than 0 is predicted to be smaller than 0 at the time T + Δt (S18).
[0023]
The surface shape strain calculation unit 25 determines, for each minute portion of the plate material, whether or not the minimum principal strain increment Δε2 is predicted to be greater than 0 in the pressing process. As shown in FIG. 6, the fact that the minimum principal strain increment Δε2 is predicted to be greater than 0 means that the minimum principal strain increment Δε2 moves in the right direction (B direction) in the figure. It is considered that the distortion of each minute portion is generated in the direction of stretching the plate material as time advances. Conversely, when the minimum principal strain increment Δε2 is predicted to be smaller than 0, the minimum principal strain increment Δε2 moves in the left direction (A direction) in the figure. It is considered that the strain is generated in the direction of shrinking the plate material with time (S19).
[0024]
When the surface shape distortion calculation unit 25 determines that there is a surface shape defect (such as wrinkles or surface strain) (S19: YES), the surface result is displayed on the determination result display unit 35 (S20). When it is determined (S19: NO), that effect is displayed on the determination result display unit 35 (S21). This display is performed separately for each minute portion. For example, when the method of the present invention is applied to a simulation of pressing a car body panel of an automobile, the determination result display unit 35 has a portion determined to have no surface shape defect and a surface shape defect as shown in FIG. The determined part is displayed as a color-coded image (S22).
[0025]
As described above, in this embodiment, the presence / absence of a surface shape defect is determined by obtaining a strain history, but the surface shape defect is determined by obtaining the magnitude of stress applied to a minute part of a molded product during plastic deformation. The presence or absence may be determined.
[0026]
As described above, according to the surface shape defect presence / absence determination method and apparatus therefor in the forming process simulation according to the present invention, when a plate material is plastically deformed using the forming process simulation, it is accurately determined whether or not a surface shape defect occurs in the sheet material. Can be determined.
[0027]
In addition, when the calculation target area of the strain history is designated, the calculation target area is limited, so that the process of determining whether there is a surface shape defect can be speeded up.
[0028]
Furthermore, when the determination result is displayed, it is possible to display at a glance a region where a surface shape defect may occur and a region where a surface shape defect does not occur.
[Brief description of the drawings]
FIG. 1 is a block diagram of a surface shape defect presence / absence determination device according to the present invention.
FIG. 2 is a flowchart showing a procedure of a surface shape defect presence / absence determination method executed by the surface shape defect presence / absence determination device of FIG. 1;
FIG. 3 is a flowchart showing the operation of a surface shape defect presence / absence determination device when a plate material is pressed.
FIG. 4 is a diagram showing an example of press molding.
FIG. 5 is a diagram for explaining a mutual relationship between a maximum principal strain ε1 and a minimum principal strain ε2.
FIG. 6 is a diagram for explaining a criterion for determining whether or not a surface shape is defective.
FIG. 7 is a diagram showing a display example of presence / absence of a surface shape defect.
[Explanation of symbols]
10 ... Processing condition input part,
15 ... Molding simulation execution unit,
20 ... strain distribution storage unit,
25 ... Surface shape strain calculation unit,
30 ... area designation part,
35: Determination result display section.

Claims

Calculating a strain distribution of the molded product in a machining process by simulating the molded product under set molding conditions; and
Calculating a strain history of each minute portion of the molded article based on the calculated strain distribution;
Determining the presence or absence of surface shape defects of the molded article from the calculated strain history;
Only including,
The step of calculating the strain history of each minute portion of the molded article is as follows:
Obtaining an increment Δε of strain due to a moving distance of each minute portion from the strain distribution at time T and the strain distribution before time T from time T in the molded article;
A minute portion having a strain increment Δε larger than 0 is predicted to have a strain increment Δε larger than 0 after a minute time Δt from time T, while a minute portion having a strain increment Δε smaller than 0 is predicted to be smaller than time T. Predicting that the strain increment Δε after a minute time Δt is also less than 0,
Including
Recognizing whether the strain of each minute part of the molded product is generated in the direction of stretching the material with time or based on the predicted strain distribution A method for determining presence / absence of a surface shape defect in a molding process simulation.

2. The presence / absence of a surface shape defect in a molding process simulation according to claim 1 , further comprising a step of designating a calculation target region of the strain history before the step of calculating the strain history of each minute portion of the molded article. Judgment method.

The step of determining the presence or absence of a defective surface shape of the molded article includes
2. The molding process according to claim 1, wherein it is determined that there is a defective surface shape when it is recognized that the distortion of each minute portion of the molded product is generated in the direction of shrinking the material as time progresses. Method for determining presence or absence of surface shape in simulation.

The step of determining the presence or absence of a defective surface shape of the molded article includes
2. The surface shape defect in the molding process simulation according to claim 1, wherein it is determined that there is a surface shape defect when an increase in strain Δε is predicted to be smaller than 0 in any minute part of the molded product. Presence determination method.

2. The surface shape defect presence / absence determination method in the molding process simulation according to claim 1, further comprising a step of displaying a determination result of the surface shape defect presence / absence of the molded product .

Setting means for setting molding processing conditions;
A processing means for processing a workpiece in a simulated manner under set molding processing conditions;
Strain distribution calculating means for calculating the strain distribution of the molded product in the processing process;
Storage means for storing the calculated strain distribution;
Strain history calculating means for calculating a strain history of each minute portion of the molded product based on the stored strain distribution;
Determination means for determining the presence or absence of a surface shape defect of the molded product from the calculated strain history;
I have a,
The strain history calculation means includes
Means for obtaining an increment Δε of strain due to the movement distance of each minute portion from the strain distribution at time T in the molded article and the strain distribution before time t from time T based on the strain distribution;
A minute portion having a strain increment Δε larger than 0 is predicted to have a strain increment Δε larger than 0 after a minute time Δt from time T, while a minute portion having a strain increment Δε smaller than 0 is predicted to be smaller than time T. Means for predicting that the strain increment Δε after a minute time Δt is also smaller than 0,
Have
Based on the strain distribution, it is recognized whether the strain of each minute part of the molded product is generated in the direction in which the material is stretched over time or in the direction in which the material is contracted. The surface shape defect presence / absence determination device in the molding process simulation.

The determination means includes
The molding process according to claim 6, wherein it is determined that there is a defective surface shape when it is recognized that the distortion of each minute portion of the molded product is generated in the direction of shrinking the material as time progresses. Surface shape defect presence / absence determination device in simulation.

The determination means includes
7. A surface shape defect in a molding process simulation according to claim 6, wherein it is determined that there is a surface shape defect when an increase in strain Δε is predicted to be smaller than 0 in any minute part of the molded product. Presence / absence judging device.

7. The surface shape defect presence / absence judging device in the molding process simulation according to claim 6, further comprising designation means for designating a calculation target area of the strain history.

7. The surface shape defect presence / absence judging device in molding process simulation according to claim 6, further comprising display means for displaying a judgment result of the presence or absence of the surface shape defect of the molded product .