JP4932609B2 - Molding condition determination system - Google Patents

Description

  The present invention relates to a molding condition determination system that determines molding conditions in a press working apparatus. Specifically, the present invention relates to a method for determining molding conditions according to the strain state of a press-formed product.

Conventionally, it is known that the molding speed has a great influence on the quality of a molded product in press working. For this reason, in order to prevent cracks, wrinkles, dimensional accuracy defects and the like that occur in a molded product, a pressing method and a pressing apparatus that control a molding speed have been proposed (for example, see Patent Document 1). According to the pressing method and the pressing apparatus disclosed in Patent Document 1, the molding speed is controlled so that the ratio between the amount of movement of the upper mold and the amount of inflow of the material falls within a preset appropriate range. .
JP 2005-125355 A

  Incidentally, a molded product having a complicated shape such as a fuel tank of a motorcycle has a portion to be drawn and a portion to be stretched. These two moldings have different optimum molding speeds. Specifically, since the inflow of material increases when the molding speed is increased, it is preferable to press-mold the portion to be drawn at a higher molding speed. On the other hand, since the elongation of the material increases when the molding speed is slowed, it is preferable that the part to be stretch-molded is press-molded at a slow molding speed.

  That is, in press molding, it is necessary to appropriately adjust the molding speed depending on which of the draw molding and the stretch molding is dominant. However, the molding speed determination method as disclosed in Patent Document 1 cannot determine the molding speed for properly forming a molded product having such a complicated shape. Therefore, in such a case, the molding speed is often determined by the experience of the operator, and therefore it may take time to determine the molding speed.

  Further, in a press machine such as a servo press that can change the forming speed and the wrinkle pressing pressure during forming, there are a wide variety of combinations of the forming speed and wrinkle pressing pressure that can be set. For this reason, for example, when determining the optimum combination of the forming speed and the wrinkle presser pressure, if the forming speed is determined based on the operator's experience as described above, it may take enormous time, a lot of materials and costs. was there.

  An object of this invention is to provide the molding condition determination system which can determine the shaping | molding speed of a press work apparatus appropriately and rapidly.

The molding condition determination system of the present invention is a molding condition determination system that determines molding conditions of a press working apparatus (for example, press working apparatus 30 described later) for press forming a plate material (for example, a steel plate 32 described later). Molding simulation means (for example, molding simulation means 131 described later) that performs molding simulation under molding conditions including speed, and the strain state in each element of the press-molded plate material based on the result of the molding simulation means Strain distribution plotting means (for example, strain distribution plotting means 132 described later) for plotting on a forming limit diagram including a limit line to create a strain distribution map, points plotted by the strain distribution plotting means, and the points Based on the relative positional relationship with the forming limit line, Crack risk maximum point what crack is likely to occur (e.g., a crack risk maximum point Q _{A below)} extracted as, determining means for determining whether the quality of the press-molded product reaches a certain level (e.g., When it is determined by the determination means 133) described later and the determination means that the quality of the press-formed product does not reach a certain standard, and the minimum principal strain at the crack risk maximum point is 0 or less, the molding When the molding condition is set by increasing the speed, and the minimum principal strain at the maximum point of risk of cracking is greater than 0, a molding speed increasing / decreasing means for decreasing the molding speed and setting the molding condition (for example, described later) Molding speed increasing / decreasing means 134), and repeating the molding simulation means, strain distribution plotting means, and judging means in this order until the judging means judges that the quality reaches a certain standard. It is characterized by that.

Here, the region where the minimum principal strain is greater than 0 is a region to be stretch-formed, and the region where the minimum principal strain is 0 or less is a region to be drawn.
According to the present invention, a molding simulation is performed by the molding simulation unit, and a strain distribution diagram is created by the strain distribution diagram plotting unit based on the result. Next, of the points plotted in the strain distribution diagram, the point where cracking is most likely to occur is extracted as the crack risk maximum point by the determination means, and the quality of the molded product is determined based on this.

  Here, when it is determined that the quality of the molded product does not reach a certain standard, and the minimum principal strain at the maximum risk point of cracking is 0 or less, the draw molding is dominant in this molded product. The molding speed is increased by the molding speed increasing / decreasing means. Further, when it is determined that the quality of the molded product does not reach a certain standard and the minimum principal strain at the maximum point of risk of cracking is greater than 0, it is determined that the stretch molding is dominant in this molded product, and the molding speed The molding speed is reduced by the increasing / decreasing means.

  The processing by these molding simulation means, strain distribution plotting means, and judgment means is repeated until it is judged that the quality of the molded product reaches a certain standard, whereby the optimum molding speed corresponding to the shape of the molded product is automatically set. To be determined. Therefore, the molding speed of the press working apparatus can be determined appropriately and quickly as compared with the conventional case where the molding speed is determined based on the intuition and experience of the operator. Further, according to the present invention, since the molding speed can be automatically determined, the number of trial productions using an actual press working apparatus or material can be greatly reduced, and the cost can be reduced. Further, at the stage of designing the shape of the product, a product having a complicated shape can be molded by predicting the molding condition using the molding condition determination system of the present invention.

  According to this invention, compared with the case where the forming speed is determined based on the operator's intuition and experience as in the prior art, the forming speed of the press working apparatus can be determined appropriately and quickly. Further, according to the present invention, since the molding speed can be automatically determined, the number of trial productions using an actual press working apparatus or material can be greatly reduced, and the cost can be reduced. Further, at the stage of designing the shape of the product, a product having a complicated shape can be molded by predicting the molding condition using the molding condition determination system of the present invention.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
FIG. 1 is a diagram showing a schematic configuration of a molding condition determination system 1 according to an embodiment of the present invention. The molding condition determination system 1 includes an arithmetic processing device 10 that is connected to the press working device 30 and executes various programs, and an input unit 20 that inputs information to the arithmetic processing device 10.
The press working apparatus 30 is a servo press machine driven by a servo, and the molding condition determination system 1 outputs the press molding conditions including the molding speed and the pressing force to the press working apparatus 30.

  The molding condition determination system 1 includes a molding condition optimization unit 11 and a press control data generation unit 14 as programs developed on an OS (Operating System) that performs operation control.

  The molding condition optimizing unit 11 includes a wrinkle presser pressure optimizing unit 12 and a molding speed optimizing unit 13, and optimizes the wrinkle presser pressure and the molding speed included in the press molding conditions. Specifically, the wrinkle presser pressure optimizing means 12 and the forming speed optimizing means 13 each perform a forming simulation (CAE analysis) based on information input from the input means 20, and based on this, the optimum wrinkle presser is determined. Determine pressure and molding speed.

The press control data generation unit 14 generates data for operating the press working apparatus 30 based on the molding conditions determined by the molding condition optimization unit 11.
The input unit 20 is a keyboard, and information necessary for performing a molding simulation by the molding condition optimization unit 11 can be input.

FIG. 2 is a diagram illustrating a schematic configuration of the press working apparatus 30.
The press working apparatus 30 is a so-called servo press machine, and moves the upper mold 51 closer to and away from the lower mold mechanism 40 having the lower mold 41 disposed on the lower side of the steel plate 32 as a workpiece and the lower mold 41. An upper mold mechanism 50 to be operated, and a lower mold mechanism 40 and a control device 31 for controlling the upper mold mechanism 50.

  The upper mold mechanism 50 includes a servo motor 52, a reduction gear 53 that is rotationally driven by the servo motor 52, a rotary plate 54 that is rotationally driven by the reduction gear 53 with a large torque, and an upper end on the side surface of the rotary plate 54. The part has a connecting rod 55 pivotally supported.

  The servo motor 52 is, for example, an AC type, and has high responsiveness and small torque unevenness. The shaft rotation position of the servo motor 52 is detected by an encoder (not shown), and the servo motor 52 is feedback-controlled based on the detected shaft rotation position.

  The upper mold mechanism 50 further includes a slider 56 that is pivotally supported at the lower end of the connecting rod 55, and the upper mold 51 is provided on the lower surface of the slider 56.

  The upper die 51 is pressed by pressing the steel plate 32 together with the lower die 41, and a die surface 51a for contacting the upper surface of the steel plate 32 is provided on the lower surface. This 51 is a concave curved surface, and an annular holder 57 is provided around the upper mold 51. The front end surface of the holder 57 is horizontal and slightly protrudes from the mold surface 51a. Therefore, the holder 57 comes into contact with the steel plate 32 prior to the mold surface 51a.

  In addition to the lower mold 41, the lower mold mechanism 40 includes a fixed base 42 that serves as a base, an annular blank holder 43 that supports the periphery of the steel plate 32, and a die cushion mechanism 44 that raises and lowers the blank holder 43. .

  The lower die 41 is provided on the upper part of the fixed base 42 and presses the steel plate 32 together with the upper die 51. On the upper surface of the lower mold 41, a mold surface 41a for contacting the lower surface of the steel plate 32 is provided.

  The blank holder 43 is provided at a position facing the holder 57 and sandwiches the end portion of the steel plate 32 together with the holder 57 in order to prevent wrinkles and displacement when the steel plate 32 is pressed.

  The die cushion mechanism 44 includes a plurality of pins 45 that pass through the fixed base 42 and the lower mold 41 from below and support the lower portion of the blank holder 43, and a hydraulic lifting mechanism (not shown) that lifts and lowers these pins 45. .

  The lifting mechanism includes a hydraulic cylinder (not shown) connected to the pin 45 and a servo device (not shown) that drives the hydraulic cylinder. This servo device is connected to the control device 31 and performs a predetermined pressure control based on a signal from the control device 31, so that the peripheral portion of the steel plate 32 is appropriately pressured by the blank holder 43 and the holder 57. Press with (wrinkle presser pressure) to hold the wrinkle.

  The control device 31 drives the servo motor 52 to move the upper die 51 forward and backward relative to the lower die 41 and drives the die cushion mechanism 44 to raise and lower the blank holder 43.

  A procedure for processing the steel plate 32 using the above press working apparatus 30 will be described with reference to FIG.

  First, in step S1, initial setting is performed. That is, the blank holder 43 is raised to a predetermined position, and the blank steel plate 32 is supported by the blank holder 43. Further, the upper mold 51 is raised to the top dead center. Next, in step S <b> 2, under the action of the control device 31, the servo motor 52 is rotationally driven to lower the slider 56.

  When the slider 56 is lowered to some extent, the holder 57 comes into contact with the upper surface of the steel plate 32, and the steel plate 32 is held between the holder 57 and the blank holder 43. From this point, the blank holder 43 is lowered under the action of the control device 31 (step S3). Specifically, under the action of the control device 31, the blank holder 43 generates an appropriate force so that the lower surface of the steel plate 32 appears to be pressed, and pressure control is performed so as to descend while securely holding the steel plate 32. . That is, the blank holder 43 is pressed through the steel plate 32 by the holder 57 and is pressed down while applying an appropriate pressure to the steel plate 32. Thereby, the steel plate 32 is lowered while the peripheral portion is held (clamped) by the holder 57 and the blank holder 43, and is gradually pressed into the product shape by the upper die 51 and the lower die 41.

  In step S4, the control device 31 causes the position of the slider 56 to reach the bottom dead center (that is, the lowest point during one stroke of the upper mold 51). In step S5, under the action of the control device 31, the servo motor 52 is rotationally driven to raise the slider 56 to the panel transport position.

  In step S6, it is confirmed whether or not the position of the slider 56 has reached the panel transport position. If it has reached, the process proceeds to step S7, and if not reached, the slider 56 continues to rise. In step S <b> 7, the blank holder 43 is raised under the action of the control device 31. As a result, the blank holder 43 rises slightly later than the slider 56.

  In step S8, the blank holder 43 is raised to the panel transport position under the action of the control device 31. In step S9, the raising of the blank holder 43 is temporarily stopped, and the steel plate 32 that has been subjected to the draw forming process is transported to the next process station by a transport means (not shown).

  In step S10, the control device 31 raises the blank holder 43 again to reach the blank holder 43 to the processing standby position. In step S11, an unprocessed steel plate is placed at a predetermined position. During this time, the slider 56 continues to rise. In step S12, the control device 31 causes the slider 56 to reach the top dead center.

Next, displacement of the slider of the press working apparatus 30 will be described with reference to FIG.
In the above-described draw molding, the drawing is performed by displacing the slider 56, that is, the upper die 51 as shown in FIG. Specifically, the upper die 51 is lowered from the top dead center (X ₁ ), and the speed is reduced just before the position (X ₂ ) in contact with the steel plate, and press molding is performed. When the upper mold 51 reaches the bottom dead center (X ₃ ), the upper mold 51 is raised at the original predetermined speed. In the following, the forming speed is assumed to be the speed of the slider 56 in the section from the contact position (X ₂ ) to the bottom dead center (X ₃ ) in FIG.

FIG. 5 is a block diagram showing a schematic configuration of the molding speed optimizing means 13.
The forming speed optimizing means 13 includes a forming simulation means 131 for performing a forming simulation, a strain distribution diagram plotting means 132 for creating a strain distribution diagram, a determining means 133 for determining the quality of a press-formed product, and setting of the forming speed. A molding speed increasing / decreasing means 134 for increasing / decreasing is provided.

  The molding simulation unit 131 performs press molding molding simulation. When an analysis condition is input, the molding simulation unit 131 performs a molding simulation under the analysis condition and outputs the analysis result. In addition to the press forming conditions including the forming speed and the wrinkle pressing pressure, the analysis conditions include the shape and material of the workpiece, the shape of the press-formed product, and boundary conditions necessary for forming simulation.

  FIG. 6 is a diagram illustrating an example of the shape of a workpiece input as one of analysis conditions. FIG. 7 is a diagram illustrating an example of the shape of a press-formed product that is input as one of analysis conditions. In the molding simulation means 131 in the present embodiment, for example, a molding simulation for forming a fuel tank 90 of a substantially box-shaped motorcycle as shown in FIG. 7 by press-molding a plate-like workpiece 80 as shown in FIG. Is done.

As shown in FIG. 6 and FIG. 7, a plurality of mesh-like elements P _{1 to} P _N are assumed for the workpiece 80 on which the forming simulation is performed in order to measure the state of the press-formed product. In addition, the analysis result of the forming simulation includes the maximum principal strain and the minimum principal strain that serve as indices of wrinkles and surface strain of the press-formed product in each of the elements P _{1 to} P _N.

Based on the analysis result output from the forming simulation means 131, the strain distribution diagram plotting means 132 converts the strain state in each element P _{1 to PN} of the press-formed work into a forming limit line including a forming limit line. Plot to create a strain distribution diagram.

8 and 9 are diagrams showing examples of strain distribution diagrams created by the strain distribution diagram plotting unit 132. FIG. Specifically, in FIG. 8, the horizontal axis is the maximum principal strain ε ₁ (≧ 0) in the in-plane direction of the steel sheet, the vertical axis is the minimum principal strain ε ₂ in the in-plane direction of the steel sheet, and this ε ₁ -ε on ₂ coordinate, it is a plot of state (deformation state) strain in the elements P ₁ to P _N of the press-molded product.

In the strain distribution diagram of FIG. 8, a line (ε ₂ = ε ₁ ) extending from the origin O to the upper right represents equal biaxial tension. By this equal biaxial tension (ε ₂ = ε ₁ ), the steel sheet is stretched to a shape substantially similar to that before forming. This equibiaxial tension corresponds to, for example, the deformation state of the bottom of the deep-drawn container.

A line (ε ₂ = 0) extending rightward from the origin O represents plane strain tension. By this plane strain tension (ε ₂ = 0), the steel sheet is stretched along the height direction (direction along ε ₁ ) without changing the dimension along the width direction (direction along ε ₂ ). It becomes. This plane strain tension corresponds to, for example, a bent portion of a wide steel plate or a deformed state near the shoulder-side wall boundary of a deep-drawn container.

A line extending from the origin O to the lower right (ε ₂ = −0.5ε ₁ ) represents uniaxial tension. By this uniaxial tension (ε ₂ = −0.5ε ₁ ), the steel sheet is squeezed along the width direction (direction along ε ₂ ) and stretched along the height direction (direction along ε ₁ ). Will be. That is, uniaxial tension corresponds to a deformed state pulled in a uniaxial direction.

Further, the forming limit line FL is indicated by a broken line in FIG. This forming limit line FL is obtained by measuring the breaking strain by changing the strain ratio ε ₂ / ε ₁ in the plate surface, and plotting it on the ε ₁ -ε ₂ coordinates. Depends on etc. Here, in the ε ₁ -ε ₂ coordinates, the region of ε ₂ > 0 indicates a stretched region where the workpiece is stretched and the region of ε ₂ ≦ 0 indicates the stretched region where the workpiece is stretched. Show.
The strain distribution diagram plotting means 132 plots the strain state at each element P _{1 to} P _N of the press-formed workpiece as points Q _{1 to} Q _N on the above-described forming limit diagram, as shown in FIG. Create a strain distribution map as shown.

The determination unit 133 determines whether the quality of the press-formed product reaches a certain standard based on the strain distribution diagram created by the strain distribution diagram plot unit 132. Specifically, what most cracks are likely to occur among the strain distribution diagram plotted points Q ₁ to Q _N extracted as crack risk maximum point Q _A, based on the position of the crack risk maximum point Q _A Thus, it is determined whether or not the quality of the press-formed product reaches a certain standard.

First, the determination unit 133 calculates crack risk degrees E _{1 to} E _N at all points Q _{1 to} Q _N plotted in the strain distribution diagram. Specifically, the crack risk level E is determined based on the intersection between a straight line passing through the origin and the target point Q and the forming limit line as R, and the distance between the origin and the intersection R as the point Q and the target point Q. It is calculated by dividing by the distance.

For example, a crack risk _{E A} in the interior point _{Q A} strain distribution diagram shown in Figure 9, the maximum value of the principal strain and minimum principal strain at point _{Q A} and _(e 1, e _2), the maximum intersection _{R A} If the values of the main strain and the minimum main strain are (e ₃ , e ₄ ), they are calculated by the following equations.

  That is, the crack risk E is an index indicating the risk of cracking in the press-formed product, and the risk increases as the crack risk E decreases. When E> 1, it is estimated that the risk of cracking is low, when E = 1, it is estimated that the crack is at the limit, and when E <1, it is estimated that a crack occurs.

Judging means 133, at all points of strain distribution diagram plotted points _Q 1 to Q _N, and calculates a crack risk _E 1 to E _N, from these cracks risk _E 1 to E _N, most A point having a small crack risk is extracted, and this is set as the maximum crack risk point. In the example shown in FIG. 9, the point Q _A is extracted as a crack risk maximum point.

Further determination unit 133, based on the size of the crack risk E _A of the extracted crack risk maximum point Q _A, determines the quality of the molded article. Specifically, the determination unit 133 sets a predetermined value greater than 1 as a threshold value in consideration of safety, and determines that the quality of the press-formed product has reached a certain standard if the threshold value is larger than this threshold value. .

Forming speed adjusting unit 134, according to the value of the minimum principal strain e ₂ crack risk maximum point Q _A, to increase or decrease the setting the forming speed to be input to the forming simulation means 131 described above.
Specifically, the molding speed adjusting unit 134, the determination unit 133 is determined as the quality of the press-molded product does not reach the predetermined reference, and the value of the minimum principal strain e ₂ crack risk maximum point Q _A 0 In the following cases, the molding speed is increased and this molding speed is set. Further, the forming speed increasing / decreasing means 134 determines that the quality of the press-formed product does not reach a certain standard by the determining means 133 and the value of the minimum principal strain e _{2 at} the crack risk maximum point Q _A is greater than zero. In this case, the molding speed is decreased and the molding speed is set.

  The molding speed optimizing means 13 configured as described above changes the setting of the molding speed input to the molding simulation means 131 until the judgment means 133 determines that the quality of the molded product reaches a certain standard, and molding is performed. The process is repeated in the order of the simulation unit 131, the strain distribution diagram plot unit 132, and the determination unit 133. Here, when the determination means 133 determines that the quality of the molded product reaches a certain standard, the molding speed at this time is determined as the optimum molding speed.

Next, the operation of the molding speed optimizing means 13 will be described using the flowchart of FIG.
First, in S21, the shape of the press-formed product is set, and in S22, the work is divided and a plurality of elements are set. Specifically, in the present embodiment, the workpiece 80 provided with the elements P _{1 to} P _N as shown in FIG. 6 is set to be press-molded in the fuel tank 90 of the motorcycle shown in FIG. In S23, boundary conditions necessary for the molding simulation are set in addition to the molding conditions including the molding speed and the wrinkle presser pressure.

In S24, the molding simulation analysis described later with reference to FIGS. 14 to 22 is executed under the analysis conditions set in S21 to S23. In S25, a strain distribution diagram as shown in FIG. 8 is created based on the result of the molding simulation analysis. In S26, the crack risk maximum point Q _A in the created strain distribution diagram is extracted.

In S27, based on the value of the crack risk E _A at the extracted crack risk maximum point Q _A, it determines whether the quality of the press-molded product has reached a certain level. If this determination is Yes, the set molding speed is determined as the optimum molding speed, the process is terminated, and if No, the process proceeds to S28.

In S28, the minimum main strain at the crack risk maximum point Q _A is determined whether 0 or less. If this determination is Yes, the process moves to S29, and if No, the process moves to S30. In S29, the set molding speed is increased, the process proceeds to S24, and the molding simulation analysis is performed again. Specifically, when forming speed set were forming speed as shown by the solid line D ₀ in FIG. 4, raising the forming speed as shown in a broken line D _2. In S30, the set molding speed is reduced, and the process proceeds to S24, where the molding simulation analysis is performed again. Specifically, when forming speed set were forming speed as shown by the solid line D ₀ in FIG. 4, lower the molding speed, as indicated by the broken line D _1.

FIG. 11 is a graph showing the relationship between the forming speed and the elongation of the press-formed work.
As shown in FIG. 11, the elongation of the work decreases as the forming speed increases. That is, in the case of stretch forming in which the elongation of the workpiece has a great influence on the forming limit, that is, when the minimum principal strain is greater than 0, the reduction rate of the thickness of the formed portion decreases as the forming speed decreases. Is preferably slower.

FIG. 12 is a graph showing the relationship between the forming speed and the coefficient of friction between the workpiece and the mold, and FIG. 13 is a graph showing the relationship between the forming speed and the inflow amount of the workpiece.
As shown in FIG. 12, the coefficient of friction between the workpiece and the mold decreases as the molding speed increases. As a result, as shown in FIG. 13, the inflow amount of the work increases as the forming speed increases. In other words, in the case of draw forming in which the inflow amount of the work greatly affects the forming limit, that is, when the minimum principal strain is 0 or less, the plate thickness reduction rate of the formed portion decreases as the forming speed increases. A higher molding speed is preferable.
Further, since the influence of friction increases as the surface pressure increases, as shown in FIG. 13, the inflow amount of the steel sheet increases more significantly when the surface pressure is large than when the surface pressure is small. .

Next, the procedure of the molding simulation analysis, that is, the operation of the molding simulation means 131 will be described using the flowchart of FIG.
In S31, analysis conditions are input. Specifically, analysis conditions including molding conditions such as the shape of the press-molded product, the shape and material of the workpiece, the molding speed, the wrinkle pressing pressure, the stress-strain relationship of the workpiece, and the friction coefficient are input. Here, the stress-strain characteristics depend on the strain rate, and the friction coefficient depends on the sliding speed between the workpiece and the mold and the contact surface pressure.

  In S32, it is determined whether or not deformation occurs. If this determination is Yes, the process moves to S33, and if No, the process moves to S36.

  In S33, the strain rate of the deformed portion is calculated, and in S34, the stress-strain relationship is determined based on this strain rate. The determination of the stress-strain relationship is performed every predetermined cycle until the end time is reached.

FIG. 15 is a diagram illustrating a stress-strain relationship.
As shown in FIG. 15, the stress-strain relationship depends on the strain rate, and the stress at the same strain amount tends to increase as the strain rate increases.
Specifically, the strain rates at the same strain amount decrease in the order of strain rates 10, 1, 0.1, and 0.01.

Further, as shown in FIG. 16, when the strain rate changes during the deformation, the stress-strain relationship after the strain rate changes depends only on the strain rate after the change regardless of the strain rate before the change. It has been found. That is, the stress-strain relationship after the strain rate changes is not affected by the speed history before the strain rate changes.
Specifically, even if the strain rate is 1, 0.1, or 0.01, when the strain rate changes to 0.1, the stress follows the graph of the strain rate of 0.1.

Therefore, the stress-strain relationship is defined as follows using equivalent stress and equivalent plastic strain. The equivalent stress is a stress converted to uniaxial tension, and the equivalent plastic strain is a plastic strain converted to uniaxial tension. By converting in this way, the comparison can be made easily and the strength evaluation becomes easy.
That is, as shown in FIG. 17, the relationship between a predetermined equivalent plastic strain and an equivalent stress is obtained for a predetermined strain rate by an experiment or the like, and point sequence data is generated.

  Here, the predetermined strain rate is 0.01, 0.1, 1, 10, and the predetermined equivalent plastic strain is 0, 0.05, 0.1, 0.15, 0.2, 0.25. As shown in FIG. Then, these point sequence data were plotted on a graph as shown in FIG. 18, and each point was connected by a straight line.

Note that if the strain rate and equivalent plastic strain to be calculated are not included in the above point sequence data, the equivalent stress-equivalent plastic strain relationship cannot be obtained directly from the point sequence data. Ask in the procedure.
When the equivalent plastic strain value to be calculated is located between the two equivalent plastic strains defined in FIG. 18, the equivalent stress-equivalent plastic strain relationship is obtained using the interpolation values of these two equivalent plastic strains. Ask for.

When the strain rate to be calculated is located between the two strain rates defined in FIG. 18, the equivalent stress-equivalent plastic strain relationship is obtained using the interpolation value of these two strain rates.
In addition, the above interpolation value may be calculated | required using a linear function (straight line), and may be calculated | required using a quadratic or more function.

  However, when the strain rate to be calculated is larger than the maximum strain rate defined in FIG. 18, the equivalent stress-equivalent plastic strain relationship at the defined maximum strain rate is used. When the strain rate to be calculated is smaller than the minimum strain rate defined in FIG. 18, the equivalent stress-equivalent plastic strain relationship at the defined minimum strain rate is used. That is, an extrapolated value of strain rate is not used.

For example, as shown in FIG. 19, the point sequence data of the strain rate x is xa, xb, xc, and the point sequence data of the strain rate y is ya, yb, yc.
When obtaining the equivalent stress at the equivalent plastic strains d and e at the strain rate z, first, the interpolated values of the point sequence data of the two strain rates x and y are set as the point sequence data of the strain rate z. Of the point sequence data of the strain rate z, the interpolated values of the equivalent stresses za, zb, and zc at the equivalent plastic strains a, b, and c are set as equivalent stresses at the equivalent plastic strains d and e at the strain rate z. .
Accordingly, as shown by a thick line A in FIG. 19, the equivalent stress-equivalent plastic strain relationship at an arbitrary strain rate can be easily calculated, and even if the strain rate changes during the deformation, the strain rate changes. The equivalent stress-equivalent plastic strain relationship can be easily calculated.

  In S35, the stress of the deformed portion is calculated using the selected equivalent stress-equivalent plastic strain relationship. In S36, it is determined whether or not the workpiece and the mold are in contact with each other. If this determination is Yes, the process moves to S37, and if No, the process moves to S41.

In S37, the sliding speed between the workpiece and the mold is calculated, and in S38, the contact surface pressure between the workpiece and the mold is calculated.
Subsequently, in S39, the friction coefficient is determined based on the sliding speed and the contact surface pressure between the workpiece and the mold. The determination of the friction coefficient is performed every predetermined cycle until the end time is reached.

FIG. 20 is a diagram illustrating the relationship between the sliding speed, the contact surface pressure, and the friction coefficient.
As shown in FIG. 20, when a fluid having a lubricating function such as cleaning oil exists between the workpiece and the mold, the friction coefficient depends on the sliding speed between the workpiece and the mold, and the sliding speed is The larger the size, the smaller the tendency.
In addition, as the contact surface pressure between the workpiece and the tool increases, the friction coefficient tends to greatly depend on the sliding speed. That is, as the contact surface pressure between the workpiece and the tool increases, the friction coefficient decreases as the sliding speed increases.
In the draw forming, the contact area between the workpiece and the mold is small, so the contact surface pressure increases. In the overhang forming, the contact area is large, so the contact surface pressure tends to decrease.

Therefore, the relationship between the sliding speed and contact surface pressure and the friction coefficient is defined as follows.
That is, as shown in FIG. 21, the relationship between a predetermined sliding speed and a friction coefficient is obtained for a predetermined contact surface pressure by experiments or the like, and set as point sequence data.
Here, the predetermined contact surface pressure was 1, 2, 5, 10, and the predetermined sliding speed was 1, 5, 10, 50, 100, 200. Then, these point sequence data were plotted on a graph as shown in FIG. 22, and each point was connected by a straight line.

If the sliding speed and contact surface pressure to be calculated are not included in the above point sequence data, the relationship between the sliding speed and contact surface pressure and the friction coefficient is obtained directly from the point sequence data. Since it is not possible, it asks in the following procedures.
When the sliding speed to be calculated is located between the two sliding speeds defined in FIG. 21, the sliding speed and the contact surface pressure are calculated using the interpolation values of these two sliding speeds. Find the relationship with the coefficient of friction.

When the contact surface pressure to be calculated is located between the two contact surface pressures defined in FIG. 21, the sliding speed and the contact surface pressure are calculated using the interpolated values of these two contact surface pressures. Find the relationship with the coefficient of friction.
In addition, the above interpolation value may be calculated | required using a linear function (straight line), and may be calculated | required using a quadratic or more function.

  However, when the contact surface pressure to be calculated is larger than the maximum contact surface pressure defined in FIG. 21, the relationship between the sliding speed at the defined maximum contact surface pressure, the contact surface pressure, and the friction coefficient. Is used. Further, when the contact surface pressure to be calculated is smaller than the minimum contact surface pressure defined in FIG. 21, the relationship between the sliding speed and the contact surface pressure at the defined minimum contact surface pressure and the friction coefficient. Is used. That is, the extrapolated value of the contact surface pressure is not used.

For example, as shown in FIG. 22, point sequence data with a contact surface pressure of 5 kgf / cm 2 is pf and pg, and point sequence data with a contact surface pressure of 10 kgf / cm 2 is qf and qg.
When obtaining the friction coefficient at the sliding speed h of the contact surface pressure of 8 kgf / cm2, first, the interpolated value of the point sequence data of the two contact surface pressures of 5 kgf / cm2 and the contact surface pressure of 10 kgf / cm2 is obtained as the contact surface pressure of 8 kgf / cm2. It is point sequence data of cm2. Of the point sequence data of the contact surface pressure of 8 kgf / cm 2, the interpolated values of the friction coefficients rf and rg at the sliding speeds f and g are used as the friction coefficient at the sliding speed h of the contact surface pressure of 8 kgf / cm 2. .

Subsequently, in S40, the contact reaction force of the contacting portion is calculated, and in S41, the equation of motion of each element is solved. In S42, it is determined whether or not the end time has been reached. If this determination is No, the process returns to S32, and if Yes, the result is output (S43) and the process ends.
This output result includes the maximum principal strain and the minimum principal strain which are indicators of wrinkles and surface strain.

According to this embodiment, there are the following effects.
A molding simulation is performed by the molding simulation unit 131, and a strain distribution diagram is created by the strain distribution diagram plotting unit 132 based on the result. Next, the determination unit 133, among the plotted points strain distribution diagram, most cracks are prone points are extracted as the maximum point Q _A cracking risk, the quality of molded products is determined on this basis.

Here, when it is determined that the quality of the molded product does not reach a certain standard and the minimum principal strain at the crack risk maximum point Q _A is 0 or less, the drawing is dominant in this molded product. The molding speed is increased by the molding speed increasing / decreasing means 134. Further, when it is determined that the quality of the molded product does not reach a certain standard, and the minimum principal strain at the crack risk maximum point Q _A is larger than 0, it is assumed that the overhang molding is dominant in this molded product. The molding speed is decreased by the molding speed increasing / decreasing means 134.

  The processing by the molding simulation unit 131, the strain distribution diagram plotting unit 132, and the determination unit 133 is repeated until it is determined that the quality of the molded product reaches a certain standard, and thereby the optimal molding according to the shape of the molded product. The speed is automatically determined. Therefore, compared with the case where the forming speed is determined based on the operator's intuition and experience as in the prior art, the forming speed of the press working apparatus 30 can be determined appropriately and quickly. Further, according to the present invention, since the molding speed can be automatically determined, the number of trial productions using the actual press working apparatus 30 and materials can be greatly reduced, and the cost can be reduced. Further, at the stage of designing the shape of the product, a product having a complicated shape can be molded by predicting the molding condition using the molding condition determination system 1 of the present invention.

  It should be noted that the present invention is not limited to the above-described embodiment, and modifications, improvements, etc. within a scope that can achieve the object of the present invention are included in the present invention.

It is a figure which shows schematic structure of the molding condition determination system which concerns on one Embodiment of this invention. It is a figure which shows schematic structure of the press work apparatus of the molding condition determination system which concerns on the said embodiment. It is a flowchart which shows the process sequence of the press work apparatus which concerns on the said embodiment. It is a figure which shows the relationship between the displacement of the slider of the press work apparatus which concerns on the said embodiment, and shaping | molding time. It is a block diagram which shows schematic structure of the molding condition optimization means of the molding condition determination system which concerns on the said embodiment. It is a perspective view which shows an example of the shape of the workpiece | work input as one of the analysis conditions of the shaping | molding simulation means which concerns on the said embodiment. It is a figure which shows an example of the shape of the press molded product input as one of the analysis conditions of the shaping | molding simulation means which concerns on the said embodiment. It is a figure which shows an example of the strain distribution figure which showed the distortion | strain state of the press-molded product in the shaping | molding limit diagram which concerns on the said embodiment. It is a figure which shows an example of the strain distribution figure which showed the distortion | strain state of the press-molded product in the shaping | molding limit diagram which concerns on the said embodiment. It is a flowchart which shows operation | movement of the molding speed optimization means which concerns on the said embodiment. It is a graph which shows the relationship between the forming speed which concerns on the said embodiment, and the elongation of a workpiece | work. It is a graph which shows the relationship between the shaping | molding speed concerning the said embodiment, and the friction coefficient between a workpiece | work and a metal mold | die. It is a graph which shows the relationship between the forming speed which concerns on the said embodiment, and the inflow amount of a workpiece | work. It is a flowchart which shows operation | movement of the shaping | molding simulation means of the shaping | molding condition determination system which concerns on the said embodiment. It is a figure which shows the stress-strain relationship in the shaping | molding simulation which concerns on the said embodiment. It is a figure for demonstrating the case where the strain rate in the stress-strain relationship which concerns on the said embodiment changes. It is a figure which shows the point sequence data of the equivalent stress which concerns on the said embodiment. It is the figure which plotted the point sequence data of the equivalent stress which concerns on the said embodiment. It is a figure for demonstrating the procedure which calculates | requires the interpolation value of the equivalent stress which concerns on the said embodiment. It is a figure which shows the relationship between the sliding speed and contact surface pressure, and a friction coefficient in the shaping | molding simulation which concerns on the said embodiment. It is a figure which shows the point sequence data of the friction coefficient which concerns on the said embodiment. It is the figure which plotted the point sequence data of the friction coefficient which concerns on the said embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Molding condition determination system 10 Processing unit 11 Molding condition optimization means 12 Wrinkle presser pressure optimization means 13 Molding speed optimization means 13 Molding speed optimization means 131 Molding simulation means 132 Strain distribution diagram plotting means 133 Determination means 134 Molding speed Increase / decrease means 20 Input means 30 Press working device

Claims (1)

A molding condition determination system for determining molding conditions of a press processing apparatus for press molding a plate material,
Molding simulation means for performing molding simulation under molding conditions including molding speed,
Based on the result of the forming simulation means, a strain distribution diagram plotting means for creating a strain distribution diagram by plotting a strain state in each element of the press-formed plate material on a forming limit diagram including a forming limit line;
Based on the relative positional relationship between the points plotted by the strain distribution diagram plotting means and the forming limit line, the most likely cracks of the plotted points are extracted as the maximum crack risk point, and press forming Determination means for determining whether the quality of the product reaches a certain standard,
When it is determined by the determining means that the quality of the press-formed product does not reach a certain standard, and the minimum principal strain at the maximum crack risk point is 0 or less, the forming condition is increased by increasing the forming speed. When the minimum principal strain of the crack risk maximum point is larger than 0, the molding speed increasing and decreasing means for setting the molding conditions by reducing the molding speed,
A molding condition determining system that repeats the molding simulation unit, the strain distribution diagram plotting unit, and the determining unit in this order until the determining unit determines that the quality reaches a certain standard.

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