JP2019038005A - Method for previously estimating occurrence of crack when forming press-formed body - Google Patents
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- 238000000034 method Methods 0.000 title claims abstract description 21
- 230000002093 peripheral effect Effects 0.000 claims abstract description 42
- 238000010586 diagram Methods 0.000 claims abstract description 27
- 238000004088 simulation Methods 0.000 claims abstract description 18
- 238000005482 strain hardening Methods 0.000 claims abstract description 5
- 238000000465 moulding Methods 0.000 claims description 46
- 238000005336 cracking Methods 0.000 claims description 8
- 238000012795 verification Methods 0.000 description 7
- 238000002474 experimental method Methods 0.000 description 5
- 239000000463 material Substances 0.000 description 3
- 238000007493 shaping process Methods 0.000 description 2
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Abstract
Description
本発明は、被プレス板をプレス成形してプレス成形体を得る前段階において、プレス成形シミュレーションによってプレス成形体に割れが発生するか否かを事前に予測する方法に関する。 The present invention relates to a method for predicting in advance whether or not a crack occurs in a press-formed body by press-forming simulation in a stage before press forming a pressed plate to obtain a press-formed body.
従来より、自動車や家電製品等に用いるプレス成形体を設計する際において、当該プレス成形体を成形する金型の設計及び製作時における手戻りを出来るだけ少なくするために、プレス成形シミュレーションによってプレス成形体の成形時において割れが発生するか否かを事前に予測する作業が行われる。
例えば、特許文献１では、被プレス板をモデル化した複数の有限要素からなるモデルデータを作成するとともに、当該モデルデータを用いてプレス成形シミュレーションによる数値解析を行った後、モデルデータにおける各有限要素の最大主ひずみ及び最小主ひずみの値が成形限界線図における成形限界線より上側にあるか否かを見て割れが発生するか否かを事前予測している。
Conventionally, when designing a press-molded body for use in automobiles, home appliances, etc., press molding is performed by press-molding simulation in order to minimize rework during the design and production of the mold for molding the press-molded body. An operation for predicting in advance whether or not a crack will occur during the molding of the body is performed.
For example, in Patent Document 1, after creating model data composed of a plurality of finite elements that model a plate to be pressed, and performing numerical analysis by press molding simulation using the model data, each finite element in the model data It is predicted in advance whether cracks will occur or not by checking whether the maximum principal strain and the minimum principal strain value are above the forming limit line in the forming limit diagram.
ところで、上述の如きプレス成形シミュレーションに用いられる成形限界線図は、球頭パンチ張出成形や円筒パンチ張出成形により得られるものである。したがって、成形限界線図を用いてプレス成形シミュレーションによる割れ発生の事前予測を行う場合、プレス成形体の外周縁部を除く領域における割れ発生については事前予測の精度が高いものの、プレス成形体の外周縁部における割れ発生については事前予測の精度が低いという問題があった。 By the way, the forming limit diagram used in the press forming simulation as described above is obtained by ball head punch overhanging or cylindrical punch overhang forming. Therefore, when performing the advance prediction of crack occurrence by press forming simulation using the forming limit diagram, the accuracy of advance prediction is high for crack occurrence in the region excluding the outer peripheral edge of the press formed body. There was a problem that the accuracy of prior prediction was low with respect to the occurrence of cracks at the peripheral edge.
これを回避するために、例えば、特許文献２では、割れ発生を予測するプレス成形体に使用する素材について、せん断面比率γ、端部稜線方向のひずみ勾配Δεθ、端部稜線垂直方向のひずみ勾配Δεｒ、及び、限界相当塑性ひずみεｃｒの関係を事前に実験により求めるとともにこれらの関係を近似式にし、当該近似式を利用して成形限界線図における成形限界線の位置を補正することにより、プレス成形体の外周縁部における割れ発生の事前予測の精度を高めるようにしている。 In order to avoid this, for example, in Patent Document 2, with respect to a material used for a press-formed body that predicts the occurrence of cracking, the shear plane ratio γ, the strain gradient Δεθ in the end ridge line direction, and the strain gradient in the vertical direction of the end ridge line The relationship between Δεr and the limit equivalent plastic strain εcr is obtained in advance by experiment, and these relationships are approximated, and the position of the forming limit line in the forming limit diagram is corrected by using the approximated expression. The accuracy of prior prediction of the occurrence of cracks at the outer peripheral edge of the molded body is increased.
しかし、特許文献２の場合、割れ発生を予測するプレス成形体に使用する素材について事前に実験を行って近似式を算出するといった作業が必要であり、予測作業を行う作業者の作業時間が増加して作業コストが嵩んでしまうという問題がある。 However, in the case of Patent Document 2, it is necessary to perform an experiment in advance on a material used for a press-formed body that predicts the occurrence of a crack and calculate an approximate expression, which increases the work time of the worker who performs the prediction work. As a result, the work cost increases.
また、事前予測を行う際に、プレス成形体における外周縁部以外の領域の割れ発生の予測に使用する成形限界線図の成形限界線の値を利用することによって、プレス成形体の外周縁部において成形時に割れが発生するか否かを事前に予測したいという要望もあった。 In addition, when making a prior prediction, by using the value of the forming limit line of the forming limit diagram used for predicting the occurrence of cracks in the region other than the outer peripheral portion of the press formed body, the outer peripheral portion of the press formed body There is also a demand for predicting in advance whether or not cracking will occur during molding.
本発明は、斯かる点に鑑みてなされたものであり、その目的とするところは、プレス成形体の成形時において割れが発生するか否かを効率良く、且つ、コストを抑えて事前に予測する方法を提供することにある。 The present invention has been made in view of such points, and the object of the present invention is to predict in advance whether or not cracking will occur during the molding of a press-molded body, and at a low cost. It is to provide a way to do.
上記の目的を達成するために、本発明は、成形限界線図の成形限界線における最小主ひずみε２が０のときにおける成形限界線の最大主ひずみε１の値を利用してプレス成形体の外周縁部において成形時に割れが発生するか否かを予測するようにしたことを特徴とする。 In order to achieve the above-mentioned object, the present invention uses a value of the maximum principal strain ε 1 of the forming limit line when the minimum principal strain ε 2 in the forming limit line of the forming limit diagram is 0. It is characterized in that it is predicted whether or not a crack will occur at the time of molding at the outer peripheral edge portion.
具体的には、被プレス板をプレス成形してプレス成形体を得る前段階において、上記被プレス板をモデル化した複数の有限要素からなるモデルデータを作成するとともに当該モデルデータを用いたプレス成形シミュレーションによる数値解析を行うことによってプレス成形時に上記プレス成形体における外周縁部に割れが発生するか否かを予測するプレス成形体の成形時における割れ発生有無の事前予測方法を対象とし、次のような解決手段を講じた。 Specifically, in the stage before press forming the pressed plate to obtain a press-formed body, model data composed of a plurality of finite elements modeling the pressed plate is created and press forming using the model data is performed. By conducting numerical analysis by simulation, predict whether or not cracks will occur at the outer peripheral edge of the above-mentioned press-formed product during press molding. The solution was taken.
すなわち、第１の発明では、上記被プレス板の加工硬化指数がｎ、板厚がｔのときの成形限界線図を得た後、最小主ひずみε２が０のときにおける成形限界線の最大主ひずみε１の値Ｘを導き出し、しかる後、プレス成形シミュレーションによる数値解析を行って上記モデルデータにおける外周縁部に対応する各有限要素の最大主ひずみε１及び最小主ひずみε２をそれぞれ導き出すとともに最大主ひずみε１と値Ｘとを比較し、その後、最小主ひずみε２の値に関わらず最大主ひずみε１≧Ｘを満たす各有限要素に対応する上記プレス成形体の外周縁部の領域に割れが発生すると予測することを特徴とする。 That is, in the first invention, after obtaining the forming limit diagram when the work hardening index of the pressed plate is n and the plate thickness is t, the maximum forming limit line when the minimum principal strain ε 2 is 0 is obtained. The value X of the principal strain ε 1 is derived, and then numerical analysis is performed by press forming simulation to derive the maximum principal strain ε 1 and the minimum principal strain ε 2 of each finite element corresponding to the outer peripheral edge in the model data. In addition, the maximum principal strain ε 1 and the value X are compared, and then the outer peripheral edge portion of the press-formed body corresponding to each finite element satisfying the maximum principal strain ε 1 ≧ X regardless of the value of the minimum principal strain ε 2 . It is predicted that a crack will occur in the region.
本発明では、作業者がプレス成形体における割れ発生の予測作業を行う際、通常の成形限界線図を得る以外に事前に実験を行って近似式を算出するなどといった特許文献２の如き作業の必要が無い。また、本発明の予測方法では、プレス成形体の外周縁部において成形時に割れが発生するか否かの事前予測をプレス成形体における外周縁部以外の領域に割れが発生するか否かの予測をする際に使用する成形限界線図の成形限界線の値の一部をそのまま利用することができる。したがって、作業者は、プレス成形体全域の割れ発生予測を効率良く時間をかけずに行うことができ、割れ予測の作業にかかるコストを抑えることができる。 In the present invention, when a worker performs a prediction work of occurrence of cracks in a press-formed body, in addition to obtaining a normal forming limit diagram, an experiment is performed in advance to calculate an approximate expression. There is no need. In addition, in the prediction method of the present invention, a preliminary prediction as to whether or not a crack occurs at the time of molding in the outer peripheral edge of the press-formed body is made as to whether or not a crack occurs in a region other than the outer peripheral edge of the press-formed body. A part of the value of the forming limit line of the forming limit diagram used when performing the process can be used as it is. Therefore, the operator can efficiently predict the occurrence of cracks in the entire press-formed body without taking time, and the cost for the work of predicting cracks can be suppressed.
以下、本発明の実施形態を図面に基づいて詳細に説明する。尚、以下の好ましい実施形態の説明は、本質的に例示に過ぎない。 Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The following description of the preferred embodiment is merely exemplary in nature.
図１は、本発明の実施形態に係る予測方法の作業手順を示すフローチャート１である。本発明の予測方法は、図２及び図３に示すように、被プレス板２をプレス成形して目標形状であるプレス成形体３にする前段階において、上記被プレス板２をモデル化した複数の有限要素からなるモデルデータＤ１を作成するとともに当該モデルデータＤ１を用いたプレス成形シミュレーションによる数値解析を行うことによって成形時に上記プレス成形体３に割れが発生するか否かを事前に予測する方法であり、図１に示すように、７つのステップＳ１〜Ｓ７を順に経ることによってプレス成形体３の成形時において割れが発生するか否かが事前に分かるようになっている。 FIG. 1 is a flowchart 1 showing a work procedure of a prediction method according to an embodiment of the present invention. As shown in FIGS. 2 and 3, the prediction method of the present invention has a plurality of models in which the pressed plate 2 is modeled in the previous stage of press forming the pressed plate 2 into a press-formed body 3 having a target shape. A method for predicting in advance whether or not a crack will occur in the press-formed body 3 during forming by creating model data D1 composed of finite elements of the above and performing numerical analysis by press forming simulation using the model data D1 As shown in FIG. 1, it is possible to know in advance whether or not a crack occurs during the molding of the press-molded body 3 by sequentially performing the seven steps S1 to S7.
プレス成形体３の成形時に割れが発生するか否かの事前予測には、図４に示すような成形限界線図Ｇを用いる。この成形限界線図Ｇには、略Ｖ形状をなす成形限界線Ｓ１と、該成形限界線Ｓ１の下側に位置し、且つ、水平方向に延びる外周縁部割れ判定線Ｓ２とがそれぞれ表示されている。 A molding limit diagram G as shown in FIG. 4 is used in advance prediction as to whether or not a crack will occur when the press-molded body 3 is molded. In this forming limit diagram G, a forming limit line S1 having a substantially V shape and an outer peripheral edge crack determination line S2 positioned below the forming limit line S1 and extending in the horizontal direction are displayed. ing.
成形限界線Ｓ１は、例えば、被プレス板２の加工硬化指数がｎで、且つ、板厚がｔのときに、実験によって、或いは、理論的に導き出される広く一般的に認知されたものであり、本発明の予測方法では、プレス成形体３の外周部分以外の領域において成形時に割れが発生するか否かを予測するときの閾値として用いられる。 The forming limit line S1 is, for example, widely and generally recognized by experiments or theoretically when the work hardening index of the pressed plate 2 is n and the plate thickness is t. In the prediction method of the present invention, it is used as a threshold when predicting whether or not a crack will occur during molding in a region other than the outer peripheral portion of the press-formed body 3.
例えば、図２のプレス成形体３における位置Ｐ１に対応するモデルデータＤ１の有限要素ＡＰ１の最大主ひずみε１及び最小主ひずみε２が、図４に示すように成形限界線Ｓ１より上側に位置する場合、プレス成形体３における位置Ｐ１において成形時に割れが発生すると予測する。一方、図２のプレス成形体３における位置Ｐ２に対応するモデルデータＤ１の有限要素ＡＰ２の最大主ひずみε１及び最小主ひずみε２が、図４に示すように成形限界線Ｓ１より下側に位置する場合、プレス成形体３における位置Ｐ２において成形時に割れが発生しないと予測する。 For example, the maximum principal strain ε 1 and the minimum principal strain ε 2 of the finite element A P1 of the model data D1 corresponding to the position P1 in the press-formed body 3 in FIG. 2 are above the forming limit line S1, as shown in FIG. If it is located, it is predicted that a crack will occur during molding at the position P1 in the press-molded body 3. On the other hand, the maximum principal strain epsilon 1 and the minimum principal strain epsilon 2 finite element A P2 of the model data D1 corresponding to the position P2 in pressed bodies 3 in FIG. 2, below the forming limit line S1 as shown in FIG. 4 When it is located at the position P2, it is predicted that no crack will occur during molding at the position P2 in the press-molded body 3.
また、外周縁部割れ判定線Ｓ２は、成形限界線Ｓ１において、最小主ひずみε２が０のときにおける最大主ひずみε１の値Ｘを導き出して得たものであり、本発明の予測方法では、プレス成形体３の外周縁部において成形時に割れが発生するか否かを予測するときの閾値として用いられる。 The outer peripheral edge crack judgment line S2, in forming limit line S1, and those minimum principal strain epsilon 2 is obtained to derive the maximum principal strain epsilon 1 of the value X at the time of 0, in the prediction method of the present invention It is used as a threshold when predicting whether or not a crack will occur during molding at the outer peripheral edge of the press-formed body 3.
例えば、図２のプレス成形体３における位置Ｑ１に対応するモデルデータＤ１の有限要素ＢＱ１の最大主ひずみε１及び最小主ひずみε２が、図４に示すように外周縁部割れ判定線Ｓ２より上側に位置する場合、成形限界線Ｓ１よりも下側に位置する場合であってもプレス成形体３における位置Ｑ１において成形時に割れが発生すると予測する。一方、図２のプレス成形体３における位置Ｑ２に対応するモデルデータＤ１の有限要素ＢＱ２の最大主ひずみε１及び最小主ひずみε２が、図４に示すように外周縁部割れ判定線Ｓ２より下側に位置する場合、プレス成形体３における位置Ｑ２において成形時に割れが発生しないと予測する。 For example, the maximum principal strain ε 1 and the minimum principal strain ε 2 of the finite element B Q1 of the model data D1 corresponding to the position Q1 in the press-formed body 3 of FIG. 2 are the outer peripheral edge crack determination line S2 as shown in FIG. When located on the upper side, it is predicted that a crack will occur at the time of forming at the position Q1 in the press-formed body 3 even if it is located below the forming limit line S1. On the other hand, the maximum principal strain ε 1 and the minimum principal strain ε 2 of the finite element B Q2 of the model data D1 corresponding to the position Q2 in the press-formed body 3 in FIG. When located on the lower side, it is predicted that no crack will occur during molding at the position Q2 in the press-molded body 3.
このように、本発明の予測方法では、成形限界線図Ｇにおいて成形限界線Ｓ１では成形時における割れの発生有無を予測しきれないプレス成形体３の外周縁部について、当該プレス成形体３の外周縁部の割れの発生有無の予測にのみ使用する外周縁部割れ判定線Ｓ２を成形限界線Ｓ１に基づいて設定している。尚、上記外周縁部割れ判定線Ｓ２は、以下に示す検証を行うことにより導き出した。 As described above, according to the prediction method of the present invention, in the molding limit diagram G, the outer peripheral edge portion of the press molded body 3 in which the presence or absence of cracks during molding cannot be predicted on the molding limit line S1 is formed. An outer peripheral edge crack determination line S2 used only for predicting whether or not an outer peripheral edge crack has occurred is set based on the forming limit line S1. The outer peripheral edge crack determination line S2 was derived by performing the following verification.
まず、実際にプレス成形を実施した際にその外周縁部に割れが発生した種類の異なる３つのプレス成形体３ａ〜３ｃ（図５乃至図７参照）を選出するとともに、当該各プレス成形体３ａ〜３ｃの割れ発生部位Ｃ１〜Ｃ３における最大主ひずみε１及び最小主ひずみε２をプレス成形シミュレーションによる数値解析によって求めた。尚、プレス成形体３ａ〜３ｃの材質は、９８０Ｍｐａ級の冷延鋼板とした。 First, three different press-formed bodies 3a to 3c (see FIGS. 5 to 7) having different types of cracks generated in the outer peripheral edge when actually performing press-molding are selected, and each press-formed body 3a is selected. The maximum principal strain ε 1 and the minimum principal strain ε 2 at the crack occurrence sites C1 to C3 of ˜3c were determined by numerical analysis by press molding simulation. In addition, the material of the press-molded bodies 3a to 3c was a cold rolled steel sheet of 980 MPa class.
次に、各プレス成形体３ａ〜３ｃの成形条件を変更して上記割れ発生部位Ｃ１〜Ｃ３における最大主ひずみε１及び最小主ひずみε２をプレス成形シミュレーションによる数値解析によって算出した。尚、成形条件は、摩擦係数を実機の金型の状態に近くなるといわれている０．１２〜０．１５の間で変化させるとともに、各プレス成形体３ａ〜３ｃについて板厚を０．９ｍｍ、１．６ｍｍ、及び、２．３ｍｍに変更して割れ発生部位Ｃ１〜Ｃ３における最大主ひずみε１及び最小主ひずみε２を算出した。そして、算出した割れ発生部位Ｃ１〜Ｃ３における最大主ひずみε１及び最小主ひずみε２を上記成形限界線図Ｇにプロットした。すると、図８乃至図１０に示すように、各プレス成形体３ａ〜３ｃの成形時における外周縁部に割れが発生すると予測される限界ひずみは、成形限界線図Ｇにおいて、最小主ひずみε２が０のときにおける成形限界線Ｓ１の最大主ひずみε１の値Ｘ以上で、且つ、成形限界線Ｓ１より下方の領域に集中する傾向があることが分かった。 Next, the maximum principal strain epsilon 1 and the minimum principal strain epsilon 2 in the cracking sites C1~C3 by changing the molding conditions of each pressed bodies 3a~3c calculated by numerical analysis by the press forming simulation. The molding conditions are such that the friction coefficient is changed between 0.12 and 0.15, which is said to be close to the state of the actual mold, and the plate thickness is 0.9 mm for each of the press molded bodies 3a to 3c. The maximum principal strain ε 1 and the minimum principal strain ε 2 at the crack occurrence sites C1 to C3 were calculated by changing to 1.6 mm and 2.3 mm. Then, the maximum principal strain ε 1 and the minimum principal strain ε 2 in the crack generation sites C1 to C3 calculated are plotted in the forming limit diagram G. Then, as shown in FIG. 8 to FIG. 10, the limit strain that is predicted to crack at the outer peripheral edge during molding of the press-formed bodies 3 a to 3 c is the minimum principal strain ε 2 in the molding limit diagram G. It has been found that there is a tendency to concentrate on a region below the value X of the maximum principal strain ε 1 of the forming limit line S1 when the value is 0 and below the forming limit line S1.
つまり、プレス成形シミュレーションによる数値解析を行ってモデルデータＤ１における外周縁部の各有限要素Ｂｎの最大主ひずみε１及び最小主ひずみε２をそれぞれ導き出すとともに最大主ひずみε１と値Ｘとを比較し、最小主ひずみε２の値に関わらず最大主ひずみε１≧Ｘを満たす各有限要素Ｂｎに対応するプレス成形体３の外周縁部の領域において成形時に割れが発生すると予測が可能であることが分かった。 That is, numerical analysis by press molding simulation is performed to derive the maximum principal strain ε 1 and the minimum principal strain ε 2 of each finite element B n at the outer peripheral edge in the model data D1, and the maximum principal strain ε 1 and the value X are obtained. In comparison, regardless of the value of the minimum principal strain ε 2 , it is possible to predict that a crack will occur during molding in the outer peripheral edge region of the press-formed body 3 corresponding to each finite element B n satisfying the maximum principal strain ε 1 ≧ X. It turns out that.
次に、本発明の予測方法を用いたプレス成形体３の成形時における割れ発生有無の事前予測の手順について詳述する。 Next, detailed description will be given of a procedure for pre-prediction of the presence / absence of cracks during the molding of the press-formed body 3 using the prediction method of the present invention.
まず、図１に示すように、ステップＳ１において、ＣＡＤ上にて上記被プレス板２をモデル化した複数の有限要素からなるモデルデータＤ１を作成する。 First, as shown in FIG. 1, in step S1, model data D1 composed of a plurality of finite elements obtained by modeling the pressed plate 2 on CAD is created.
次に、ステップＳ２において、被プレス板２の加工硬化指数がｎで、且つ、板厚がｔのときにおける成形限界線図Ｇを得る（図４参照）。 Next, in step S2, a forming limit diagram G when the work hardening index of the pressed plate 2 is n and the plate thickness is t is obtained (see FIG. 4).
次いで、ステップＳ３において、モデルデータＤ１を用いてプレス成形シミュレーションを実施する。そして、プレス成形シミュレーションによる数値解析によって目標形状になったモデルデータＤ１における各有限要素の最大主ひずみε１及び最小主ひずみε２を得る。 Next, in step S3, a press molding simulation is performed using the model data D1. Then, obtain the maximum principal strain epsilon 1 and the minimum principal strain epsilon 2 of each finite element in the model data D1 reaches the target shape by numerical analysis by press-forming simulation.
しかる後、ステップＳ４において、解析したモデルデータＤ１の各有限要素のうちのプレス成形体３の外周部分以外の領域に対応する各有限要素Ａｎ（ｎは自然数）を抽出する。 Thereafter, in step S4, each finite element A n (n is a natural number) corresponding to a region other than the outer peripheral portion of the press-formed body 3 among the finite elements of the analyzed model data D1 is extracted.
ステップＳ５では、抽出した各有限要素Ａｎにおける最大主ひずみε１及び最小主ひずみε２を成形限界線図Ｇにプロットするとともに、プロットした各有限要素Ａｎの位置が成形限界線Ｓ１より上側に位置するか否かを比較する。そして、各有限要素Ａｎの位置が成形限界線Ｓ１より上側に位置した場合には、その有限要素Ａｎの位置に対応するプレス成形体３の領域に成形時に割れが発生すると予測する一方、各有限要素Ａｎの位置が成形限界線Ｓ１より下側に位置した場合には、その有限要素Ａｎの位置に対応するプレス成形体３の領域に成形時に割れが発生しないと予測する。 In step S5, with plotting maximum principal strain epsilon 1 and the minimum principal strain epsilon 2 in forming limit diagram G in each finite element A n extracted, plotted is above the forming limit line S1 position of each finite element A n It is compared whether it is located in. Then, while the position of each finite element A n is when positioned above the forming limit line S1 predicts that its corresponds to the position of the finite element A n cracking during forming the area of the pressed bodies 3 is generated, when the position of each finite element a n is positioned below the forming limit line S1 predicts that its corresponds to the position of the finite element a n cracking during forming the area of the pressed bodies 3 is not generated.
その後、ステップＳ６において、解析されたモデルデータＤ１の各有限要素のうちのプレス成形体３の外周部分に対応する各有限要素Ｂｎ（ｎは自然数）を抽出する。 Thereafter, in step S6, finite elements B n (n is a natural number) corresponding to the outer peripheral portion of the press-formed body 3 among the finite elements of the analyzed model data D1 are extracted.
ステップＳ７では、抽出した各有限要素Ｂｎにおける最大主ひずみε１及び最小主ひずみε２を成形限界線図Ｇにプロットするとともに、プロットした各有限要素Ｂｎの位置が外周縁部割れ判定線Ｓ２より上側に位置するか否かを比較する。そして、各有限要素Ｂｎの位置が外周縁部割れ判定線Ｓ２より上側に位置した場合には、その有限要素Ｂｎの位置に対応するプレス成形体３の外周縁部の領域に成形時に割れが発生すると予測する一方、各有限要素Ｂｎの位置が外周縁部割れ判定線Ｓ２より下側に位置した場合には、その有限要素Ｂｎの位置に対応するプレス成形体３の外周縁部の領域に成形時に割れが発生しないと予測して、プレス成形体３の成形時における割れ発生有無の事前予測を終了する。 In step S7, with plotting maximum principal strain epsilon 1 and the minimum principal strain epsilon 2 in forming limit diagram G in each finite element B n extracted, the outer peripheral edge crack judgment line position of each finite element B n of plotting It is compared whether or not it is located above S2. And when the position of each finite element Bn is located above the outer peripheral edge crack determination line S2, it cracks at the time of molding in the region of the outer peripheral edge of the press-formed body 3 corresponding to the position of the finite element Bn. When the position of each finite element Bn is located below the outer peripheral edge crack determination line S2, the outer peripheral edge of the press-formed body 3 corresponding to the position of the finite element Bn is predicted. It is predicted that no cracks will occur during molding in this area, and the preliminary prediction of whether or not cracks have occurred during molding of the press-molded body 3 is completed.
以上より、本発明の実施形態によると、作業者がプレス成形体３における割れ発生の予測作業を行う際、通常の成形限界線図を得る以外に事前に実験を行って近似式を算出するなどといった特許文献２の如き作業の必要が無い。また、本発明の予測方法では、プレス成形体３の外周縁部において成形時に割れが発生するか否かの事前予測をプレス成形体３における外周縁部以外の領域に割れが発生するか否かの予測をする際に使用する成形限界線図Ｇの成形限界線Ｓ１の値の一部をそのまま利用することができる。したがって、作業者は、プレス成形体３全域の割れ発生予測を効率良く時間をかけずに行うことができ、割れ予測の作業にかかるコストを抑えることができる。 As described above, according to the embodiment of the present invention, when an operator performs a prediction operation of occurrence of cracks in the press-formed body 3, an approximate expression is calculated by conducting an experiment in advance in addition to obtaining a normal forming limit diagram. There is no need for such work as in Patent Document 2. Further, in the prediction method of the present invention, whether or not a crack is generated in a region other than the outer peripheral edge portion of the press molded body 3 is determined in advance as to whether or not a crack is generated at the outer peripheral edge portion of the press molded body 3 during molding. A part of the value of the forming limit line S1 of the forming limit diagram G used for making the prediction can be used as it is. Therefore, the operator can efficiently predict the occurrence of cracks in the entire area of the press-formed body 3 without taking time, and the cost for the work of predicting cracks can be suppressed.
本発明は、被プレス板をプレス成形してプレス成形体を得る前段階において、プレス成形シミュレーションによってプレス成形体に割れが発生するか否かを事前に予測する方法に適している。 The present invention is suitable for a method for predicting in advance whether or not a crack occurs in a press-formed body by press-forming simulation in a stage before a press plate is press-formed to obtain a press-formed body.
１ フローチャート
２ 被プレス板
３ プレス成形体
Ｇ 成形限界線図
Ｓ１ 成形限界線
Ｓ２ 外周縁部割れ判定線
DESCRIPTION OF SYMBOLS 1 Flowchart 2 Plate to be pressed 3 Press molded body G Forming limit diagram S1 Forming limit line S2 Outer peripheral edge crack judgment line
Claims (1)
上記被プレス板の加工硬化指数がｎ、板厚がｔのときの成形限界線図を得た後、最小主ひずみε２が０のときにおける成形限界線の最大主ひずみε１の値Ｘを導き出し、
しかる後、プレス成形シミュレーションによる数値解析を行って上記モデルデータにおける外周縁部に対応する各有限要素の最大主ひずみε１及び最小主ひずみε２をそれぞれ導き出すとともに最大主ひずみε１と値Ｘとを比較し、その後、最小主ひずみε２の値に関わらず最大主ひずみε１≧Ｘを満たす各有限要素に対応する上記プレス成形体の外周縁部の領域に割れが発生すると予測することを特徴とするプレス成形体の成形時における割れ発生有無の事前予測方法。 Before the press plate is press-molded to obtain a press-molded body, model data consisting of a plurality of finite elements modeling the press plate is created and numerical analysis is performed by press molding simulation using the model data. It is a prior prediction method for the presence or absence of cracking at the time of molding of a press-molded body for predicting whether or not cracking occurs at the outer peripheral edge of the press-molded body during press molding,
After obtaining the forming limit diagram when the work hardening index of the pressed plate is n and the plate thickness is t, the value X of the maximum principal strain ε 1 of the forming limit line when the minimum principal strain ε 2 is 0 is obtained. Derived,
Thereafter, numerical analysis by press molding simulation is performed to derive the maximum principal strain ε 1 and the minimum principal strain ε 2 of each finite element corresponding to the outer peripheral edge in the model data, and the maximum principal strain ε 1 and the value X And then predicting that cracks will occur in the region of the outer peripheral edge of the press-formed body corresponding to each finite element satisfying the maximum principal strain ε 1 ≧ X regardless of the value of the minimum principal strain ε 2. A method for predicting the presence or absence of cracks during molding of a featured press-molded body.
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