JP2011088152A - Method of setting shearing condition - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method of designing the inclined angle of a punch blade, by which a sheared end face excellent in stretch-flange workability is obtained. <P>SOLUTION: In the method of setting a shearing condition, numerical simulation of shearing work with a punch constituted of an upper blade having the inclined angle with respect to the direction of a cutting line and a die having a lower blade is performed several times while changing the inclined angles, at the point of time when the edge of the blade of the punch bites into the material to be worked by any ratio of 10-30% of the thickness of a material to be worked on the numerical simulation, average triaxiality in an evaluation region around the hazardous region of the stretch-flange crack, which is previously selected, is calculated, and the inclined angle at which the average triaxiality is maximum is taken as the optimum inclined angle to the stretch-flange properties in the sheared end face; however, the triaxiality is numerical formula in the figure when σ<SB>1</SB>, σ<SB>2</SB>, σ<SB>3</SB>are taken as principal stresses. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a punching device for metal plates such as iron, aluminum, titanium, magnesium and alloys thereof used in automobiles, home appliances, building structures, ships, bridges, construction machines, various plants, penstocks, etc. In particular, the present invention relates to an improvement in stretch flangeability of a shearing end face generated by shearing.

  Metal plates such as automobiles, home appliances, and building structures are often subjected to shearing with a punch 2 and a die 3 as shown in FIG. As shown in FIG. 2, the sheared surface is formed in the clearance 4 formed by the workpiece 1 being entirely pushed by the punch 2, the clearance between the punch 2 and the die 3 (hereinafter referred to as “clearance” unless otherwise specified). In this case, the clearance between the punch 2 and the die 3 is referred to as the clearance between the punch 2 and the die 3. It consists of a fracture surface 6 formed by breaking the workpiece 1 and a burr 7 formed on the back surface of the workpiece 1.

  Usually, in order to reduce the punching load and noise, a blade (also referred to as an inclined blade) inclined with respect to the cutting line direction (also referred to as the punching direction) is used as shown in FIG. If the angle is not set appropriately, the stretch flangeability is inferior to the end face of shearing with a flat blade. This is because cracks are less likely to occur at the time of shearing by the inclined blade 9, and the end surface is work hardened than when sheared by a flat blade, and the width of the workpiece 1 by the inclined blade 9 Due to excessive bending in the longitudinal direction due to excessive bending in the longitudinal direction due to bending of the direction and insufficient plate reverse pressing, the work hardening of the punched end face and roughness of the end face properties are greater than those due to flat blades I think that the.

  From such a point of view, a shearing method in which only the stretch flange forming scheduled portion is a flat blade is disclosed in Patent Document 1 below, and a method of pressing only the stretch flange forming planned portion using an inclined plate reverse press to prevent plate bending. It is described in Patent Document 2 below.

  In addition to these, although not intended to improve stretch flangeability, in order to improve the accuracy of the shearing shape, an invention in which the tilt angle and cutting speed can be varied is disclosed in Patent Document 3 below. The following Patent Document 4 describes a shearing device that can drive a plurality of blades independently to improve the straightness of the cut portion and the quality of the cut surface.

JP 2009-0511001 A JP 2009-051000 A JP 07-108411 A JP-A-8-252718

  The techniques disclosed in Patent Documents 1 to 4 described above have several problems.

  In the method described in Patent Document 1, when there are a plurality of extending flange portions, the blade has a complicated shape, and the mold cost is high. The method described in Patent Document 2 requires time and effort for scrap processing by using a plate reverse presser. In the methods described in Patent Documents 3 and 4, the apparatus becomes complicated and the cost is high, and at the same time, the versatility is lacking. Moreover, there is no description about the stretch flangeability improvement effect.

  An object of the present invention is to avoid the increase in cost and the complexity of the apparatus and the mold, and to improve the stretch flangeability only by changing the inclination angle and the clearance.

In order to solve the above problems, the gist of the present invention is the following contents as described in the claims.
(1) A numerical simulation of shearing with a punch composed of an upper blade having an inclination angle with respect to the cutting line direction and a die having a lower blade is performed a plurality of times while changing the inclination angle. Calculates the average stress triaxiality of the evaluation area centered on the stretch flange crack risk area selected in advance at the time when any of the ratio of 10 to 30% of the work sheet thickness bites into the workpiece. A method for setting shearing conditions, characterized in that an inclination angle at which the stress triaxiality is maximized is an optimum inclination angle with respect to stretch flangeability of a shearing end face.
However, the stress triaxiality is σ ₁ , σ ₂ , σ ₃ when the main stress is

である。
（２）切断線方向に対して傾斜角度を有する上刃からなるパンチと、下刃を有するダイによるせん断加工の数値シミュレーションを、該傾斜角度及びパンチとダイとのクリアランスを変えて複数回行い、該数値ミュレーション上でパンチ刃先が被加工材板厚の１０〜３０％の何れかの比率だけ食い込んだ時点において、予め選定された伸びフランジ割れ危険部位を中心とする評価領域の平均の応力３軸度を算出し、該平均応力３軸度が最大となる傾斜角度及びパンチとダイとのクリアランスをせん断加工端面の伸びフランジ性に対する最適な傾斜角度及びパンチとダイとのクリアランスの組み合わせとすることを特徴とする、せん断加工条件の設定方法
ただし、応力３軸度はσ₁,σ₂,σ₃を主応力とした場合に、

It is.
(2) A numerical simulation of shearing with a die having an upper blade having an inclination angle with respect to the cutting line direction and a die having a lower blade is performed a plurality of times while changing the inclination angle and the clearance between the punch and the die, On the numerical simulation, the average stress 3 in the evaluation region centered on the preselected stretch flange cracking critical point at the time when the punch blade bites in any ratio of 10 to 30% of the workpiece plate thickness. Axiality is calculated, and the inclination angle and the punch-to-die clearance at which the average stress triaxiality is maximized are the combination of the optimum inclination angle and the punch-to-die clearance for the stretch flangeability of the shearing end face. The method of setting shearing conditions characterized by: However, when the stress triaxiality is σ ₁ , σ ₂ , σ ₃ as the main stress,

である。

It is.

  According to the present invention, it is possible to provide a method for setting shearing conditions that can improve stretch flangeability by only changing the inclination angle and clearance, avoiding an increase in cost and complexity of the apparatus / mold, and as a result An industrially useful remarkable effect can be obtained, for example, by providing a design method of an inclination angle of a punching blade capable of obtaining a shearing end face excellent in flange workability.

  Details of the present invention will be described below.

  When the present inventors actually conducted an evaluation test on the relationship between the inclination angle and the stretch flangeability of the workpiece 1 in shearing with the inclined blade 9, the stretch flangeability reached a peak at a specific inclination angle. I found a tendency to become. The stretch flange planned portion refers to the stretch flange portion 21 on the inner peripheral side where tensile deformation is applied to the cut surface at the time of flange-up molding after punching and cutting, for example, as shown in FIG.

  Numerical simulations were performed by simulating the experimental shearing conditions. The tilt angle has two effects: 1) The tensile force on the part to be cut due to the effect of rotating the workpiece 1 (see FIG. 3), 2) It was confirmed that the cutting pressure near the cutting edge increased as the cutting distance increased. Under tool conditions where cracks from the cutting edge are likely to occur, the work hardening of the shearing end face is reduced and the stretch flangeability is improved. It is widely known that the effect of 1) promotes crack generation from the cutting edge, and the effect of 2) suppresses crack generation. It is thought that the sex reached a peak.

  As a means for measuring both the effects of 1) and 2) with one index, there is an evaluation based on a stress triaxiality. The stress triaxiality increases if the tensile force in 1) is high, and decreases if the compressive stress in 2) is high. Therefore, the stretch flangeability has a peak under the condition where the stress triaxiality is the highest. When this condition is selected by numerical simulation, it becomes a problem to evaluate to which region of the workpiece 1 the stress triaxiality is evaluated. As a result of trial and error, the present inventors have found that the reproducibility of the experimental results is good if the evaluation is performed based on the average value of the evaluation region 11 centering on the stretch flange cracking risk region such as the region 6 in FIG. Further, it is not necessary to reproduce the fracture of the workpiece 1 by simulation as in the case of actual shearing, and the punch 2 is in any stretch between 10 to 30% of the plate thickness of the workpiece 1 in the stretched bringe planned portion. It was found that when the stress triaxiality was evaluated at the time when only the value was cut, an evaluation result equivalent to that obtained when cutting up to cutting was obtained. Reproduction of cutting by simulation has a high calculation load, and can be easily evaluated according to this method.

  The position of the dangerous part is determined by experiment and is preferably the part that was first cracked. The size of the evaluation area is as follows: 1) Cutting edge line between punch 2 and die 3 as shown in FIG. The distance in the tangential direction 10 is the thickness of the workpiece 1, the distance in the thickness direction is the distance in the thickness direction of the punch 2 and the die 3, and 3) the distance in the vertical direction of the cutting edge 10 is the punch 2 and the die 3. It is preferable to set the size of a region surrounded by a surface that satisfies the above three clearances, and such a position and size can reproduce the experimental result most.

  As described above, under the specific clearance, multiple numerical simulations are performed with only the tilt angle changed, and the tilt angle with the highest stress triaxiality evaluation value is designed as the optimum tilt angle for stretch flangeability. (Invention according to (1) above). It is also possible to select the optimum combination of clearance and inclination angle for stretch flangeability by performing the same evaluation by performing a plurality of simulations with different clearances (see (2) above). Invention). The number of times of simulation (the number of tool conditions) may be 2 degrees or more, but the optimum inclination angle can be obtained more accurately as the number of times increases.

  For the purpose of demonstrating the effect of the present invention, FIG. 6 assumes that a semi-circle having a radius of 15 [mm] is to be extracted from a steel sheet having a maximum tensile strength of 590 (MPa) with a thickness of 3.2 mm. The simulation shown was performed, and the optimum inclination angle 12 was selected for stretch flangeability. The simulation of FIG. 6 was performed using ABAQUS / STANDARD, which is a commercial finite element method code, and the workpiece 1 was divided into 20 parts in the thickness direction. The clearance was set to 0.32 [mm], and the level of the inclination angle 12 was 0 degree, 0.5 degree, 1 degree, 1.5 degree, and 2 degree. The amount by which the punch 2 is pushed when evaluating the triaxiality of the stress is 20% of the plate thickness. The evaluation part is the center of the R part of the cutting line.

  FIG. 7 shows the evaluation value of the stress triaxiality. The evaluation value is the largest when the inclination angle 12 is 0.5 degree, and the inclination angle of 0.5 degree is selected as the optimum inclination angle for stretch flangeability. FIG. 8 shows the result of an actual stretch flange test. As the stretch flange test, an in-plane bending test shown in FIG. 9 was performed, and the distance 8 between the semicircular end portions when the crack penetrated the cut end surface in the plate thickness direction was used as the evaluation value. It can be seen that when the inclination angle is 0.5 degrees, the stretch flangeability is the best, which is consistent with the evaluation results by simulation. From the above, the effectiveness of the present invention was confirmed.

For the purpose of demonstrating the effect of the present invention, the same simulation as in Example 1 was performed, and the optimum combination of inclination angle and clearance was selected for stretch flangeability. The levels of the inclination angle 12 are 0 degree, 0.5 degree, 1 degree, 1.5 degree and 2 degree, and the clearances are 0.16 [mm], 0.32 [mm] and 0.48 [mm]. did. The amount by which the punch 2 is pushed when evaluating the triaxiality of the stress is 20% of the plate thickness. The evaluation part is the center of the R part of the cutting ridgeline.

  FIG. 10 shows the evaluation value of the stress triaxiality. The combination of the inclination angle 12 of 0.5 degrees and the clearance of 0.16 [mm] has the highest evaluation value, and was selected as the optimum combination of the inclination angle 12 and the clearance for stretch flangeability. FIG. 11 shows the results of an actual stretch flange test. As the stretch flange test, the in-plane bending test shown in FIG. It can be seen that when the inclination angle 12 is 0.5 degrees and the clearance is 0.16 [mm], the stretch flangeability is the best, which is consistent with the evaluation results by simulation. From the above, the effectiveness of the present invention was confirmed.

It is the front view which showed the general shearing process typically. It is sectional drawing which shows typically the punching surface of the workpiece processed by the shearing process. It is a figure which shows typically the shearing process by the punch which has an inclination part, (a) is an elevation view, (b) is a side view. It is a figure which shows stretch flange processing typically, (a) shows before a process, (b) shows after a process. It is a figure which shows typically a stress triaxiality evaluation area | region, (a) is a general-view figure, (b) is sectional drawing. It is a figure which shows the simulation performed in Example 1, 2, (a) Simulation outline (b) Simulation result example (stress triaxial degree contour) (c) It is a tool figure. It is a figure which shows the simulation result performed in Example 1. FIG. It is a figure which shows the experimental result performed in Example 1. FIG. It is a figure which shows typically the in-plane bending test for stretch flangeability evaluation. It is a figure which shows the simulation result performed in Example 2. FIG. It is a figure which shows the experimental result performed in Example 2. FIG.

1 Work material (metal plate)
2 Punch 3 Die 4 Droop 5 Shear surface 6 Fracture surface 7 Beam 8 Plate retainer 9 Punched blade edge 10 Cutting edge 11 Stress triaxiality evaluation section 12 Blade inclination angle

Claims (2)

Numerical simulation of shearing with a punch composed of an upper blade having an inclination angle with respect to the cutting line direction and a die having a lower blade is performed a plurality of times while changing the inclination angle, and the punch edge is processed on the numerical simulation. At the point of time when any ratio of 10 to 30% of the thickness of the material is cut in, the average stress triaxiality of the evaluation area centered on the stretch flange cracking risk area selected in advance is calculated, and the average stress triaxiality is calculated. A method for setting shearing conditions, characterized in that an inclination angle at which the degree is maximum is an optimum inclination angle with respect to stretch flangeability of a shearing end face.
However, the stress triaxiality is σ ₁ , σ ₂ , σ ₃ when the main stress is

It is. A numerical simulation of shearing with a punch composed of an upper blade having an inclination angle with respect to the cutting line direction and a die having a lower blade is performed a plurality of times while changing the inclination angle and the clearance between the punch and the die. The average stress triaxiality in the evaluation area centered on the stretch flange crack risk area selected in advance at the time when the punch cutting edge bites in any ratio of 10 to 30% of the workpiece plate thickness The calculated inclination angle and the clearance between the punch and the die with the maximum triaxiality of the average stress are the combination of the optimum inclination angle with respect to the stretch flangeability of the shearing end face and the clearance between the punch and the die. How to set shearing conditions However, when the stress triaxiality is σ ₁ , σ ₂ , σ ₃ as the main stress,

It is.

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