A method for preprocessing water channel parameters in hot stamping simulation of thin plates

Abstract

The present invention discloses a preprocessing method for thin plate hot stamping simulation water channel parameters, comprising the following steps: Step 1, establish a 3D fluid simulation model of the cooling water channel; Step 2, divide the 3D fluid simulation model of the cooling water channel into a straight pipe part and an elbow joint part; Step 3, for the straight pipe part; Step 4, for the elbow joint part; Step 5, determine and calculate the heat transfer coefficient of the water pipe; Step 6, group the water channel parameters: group the above-mentioned water pipe center line, water pipe diameter and water channel heat transfer coefficient; Step 7, use hot stamping simulation software to read the data after grouping to form a hot stamping simulation model; The present invention processes the cooling water pipes in sections, and calculates the water pipe diameter for each section according to the principle of equal volume; the difference in the water channel heat transfer coefficient of each part can be considered in the hot stamping die simulation model, and the influence of the water channel flow velocity difference on the hot stamping forming result can be simulated, improving the accuracy of hot stamping simulation.

Description

Technical Field

[0001] The invention relates to the technical field of hot stamping simulation of automobile body parts, in particular to a method for preprocessing water channel parameters of hot stamping simulation of thin plates. Background Art

[0002] The hot stamping die needs to have cooling channels inside it. The more complex the die surface is, the more difficult it is to process the internal channels.

[0003] More and more thin-plate hot stamping parts are used on automobile bodies. Due to the complex surface structure of thin-plate hot stamping parts on automobile bodies, the development of corresponding hot stamping dies has certain technical risks. The unreasonable design of a large number of cooling water channels in hot stamping dies may cause the die to overheat, resulting in low life and substandard part performance. The use of hot stamping simulation technology can avoid the problem of failure in hot stamping die development;

[0004] There are many commercial software for hot stamping simulation, such as Autoform, Pamstamp, etc. These software can only input 2D water channels, that is, the center line of the water channel, plus the water channel diameter and the heat transfer coefficient of the water channel. The accuracy that can be achieved by this processing is limited, mainly due to the following reasons: 1. Hot stamping water pipes are complex and have multiple joints. The heat transfer coefficients of various parts of the water channel vary greatly. Using a unified heat transfer coefficient will affect the accuracy; 2. The water flow diameter at the joint of the water pipe is greatly affected by the size of the joint. Using a unified diameter will also affect the heat dissipation simulation results; 3. There is turbulence at the joint of the water pipe. The heat transfer coefficient of this part varies greatly. Using a unified heat transfer coefficient will result in a large error; these three problems make it difficult for these commercial software to consider the flow rate differences of the cooling water pipes in various parts of the mold in hot stamping simulation;

[0005] Since the existing commercial software cannot take into account the differences in heat transfer coefficients of various parts of the water channel, deviations occur between the mold temperature simulation results and the test results, resulting in the inability to accurately predict problems such as warping and cracking of hot stamping parts; therefore, the present application proposes a method for preprocessing water channel parameters for thin plate hot stamping simulation. The use of a method for preprocessing water channel parameters for thin plate hot stamping simulation of the present application can improve the accuracy of hot stamping simulation and give full play to the value of hot stamping simulation. Summary of the invention

[0006] The purpose of the present invention is to provide a method for preprocessing parameters of water channels for hot stamping simulation of thin plates, so as to solve the problem that the existing commercial software cannot take into account the differences in heat transfer coefficients of various parts of the water channel, resulting in deviations between mold temperature simulation results and test results, and the warping, cracking and other problems of hot stamping parts cannot be accurately predicted.

[0007] To achieve the above object, the present invention provides the following technical solutions: A preprocessing method for thin plate hot stamping simulation water channel parameters, comprising the following steps:

[0008] Step 1, establish a 3D fluid simulation model of the cooling water channel;

[0009] Step 2, divide the 3D fluid simulation model of the cooling water channel into a straight pipe part and an elbow joint part;

[0010] Step 3, for the straight pipe part, determine the center line of the water outlet pipe, which is a straight line. Segment according to the center line of the water pipe, with each segment being 20 - 40 mm. Determine the center point of each segment of the water pipe. Use a cross-section perpendicular to the center line to intersect with the triangular elements of the pipe wall of this section of the water channel to obtain the intersection surface of the cross-section and the pipe wall;

[0011] Two cross-section and pipe wall intersection surfaces, and the pipe wall surfaces within two segments, form a closed volume; generate multiple tetrahedrons from the closed surface, and calculate the volume of the object within the closed surface by superimposing the volumes of each tetrahedron;

[0012] Each segmented water pipe is a cylindrical surface. According to its volume and the length of the center line, obtain the water pipe diameter according to the principle of equal volume;

[0013] Step 4, for the elbow joint part, determine the center line of the water outlet pipe, which is an arc; segment the center line of the water pipe according to the curvature change, divide it into 6 - 10 segments, determine the center point of each segment of the water pipe, use a cross-section perpendicular to the center line to intersect with the triangular elements of the pipe wall of this section of the water channel to obtain the intersection surface of the cross-section and the pipe wall;

[0014] Two cross-section and pipe wall intersection surfaces, and the pipe wall surfaces within two segments, form a closed volume; generate multiple tetrahedrons from the closed surface, and calculate the volume of the object within the closed surface by superimposing the volumes of each tetrahedron;

[0015] Each segmented water pipe is a cylindrical surface. According to its volume and the length of the center line, obtain the water pipe diameter according to the principle of equal volume;

[0016] Step 5, determine and calculate the heat transfer coefficient of the water channel: Use fluid simulation to calculate the heat transfer coefficient of each triangular patch on the pipe wall inside the mold water channel. According to the above segmentation processing of the water channel, find each segment of the pipe wall triangular patch and the heat transfer coefficient on each triangular patch;

[0017] Assume that there are N triangular patches on the side of this section of the water pipe close to the mold surface. Calculate the average value of the heat transfer coefficients of the N triangular patches as the heat transfer coefficient of this section of the water pipe;

[0018] Step 6, group the water channel parameters: Group the above water pipe center line, water pipe diameter, and water channel heat transfer coefficient;

[0019] The specific grouping method is as follows: First, divide the pipe diameters into X groups of pipe diameter data according to the diameter of the water pipes, and then divide each group of pipe diameter data into Y groups according to the heat transfer coefficient of the water pipes. After grouping, the data is compiled into igs files. Each group of igs files contains the pipe diameter data, center line data, and corresponding heat transfer coefficient data of the water channels in the segmented section.

[0020] Step 7: Use a hot stamping simulation software to read the above grouped data to form a hot stamping simulation model.

[0021] Furthermore, the pipe wall of the cooling water channel is composed of triangular patches, and the inside of the water pipe of the cooling water channel is 3D finite element tetrahedral elements.

[0022] Furthermore, in step 3, the calculation formula for the cross-sectional diameter D1 of the water pipe in the straight pipe section is:

[0023]

[0024] In the formula, V is the volume of each segment of the water pipe in the straight pipe section, and L is the length of the center line of each segment.

[0025] Furthermore, in step 4, the calculation formula for the cross-sectional diameter D of the water pipe in the elbow joint section is:

[0026]

[0027] In the formula, V is the volume of each segment of the water pipe in the straight pipe section, and L is the length of the center line of each segment.

[0028] Furthermore, in step 5, the calculation formula for the heat transfer coefficient of each water channel segment is:

[0029]

[0030] In the formula, S i is the area of the i-th triangular patch in this water channel segment; H i is the heat transfer coefficient of the i-th triangular patch in this water channel segment.

[0031] Furthermore, in step 6, the grouping of water channel parameters is specifically as follows:

[0032] The diameter range of all segmented water pipes is a - b mm. Divide a - b mm into X equal parts from small to large, so as to divide the pipe diameters into X groups of pipe diameter data;

[0033] Each group of pipe diameter data contains different heat transfer coefficients. The range of the heat transfer coefficient is c - d W / m 2 ·K. Divide c - d W / m 2·K is evenly divided into Y parts from small to large, so as to divide the set of water pipe diameter data into Y groups of heat transfer coefficients.

[0034] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0035] The present invention processes the cooling water pipes in segments. For each segment, according to the principle of equal volume, the diameter of the water pipe is calculated, and the heat transfer coefficient is taken as the average value of the heat transfer coefficients of all triangular patches in this segmented part. After such segmented processing, even for the same straight water pipe, the differences in the heat transfer coefficients of different parts can be reflected, and the water channel diameter and heat transfer coefficient of the joint part can also be reflected; in the hot stamping die simulation model, the differences in the heat transfer coefficients of water channels in each part can be considered, and the influence of the differences in water channel flow velocity on the hot stamping forming result can be simulated, improving the accuracy of hot stamping simulation. BRIEF DESCRIPTION OF THE DRAWINGS

[0036] Figure 1 It is a schematic structural diagram of the 3D fluid simulation model of the cooling water channel of the present invention;

[0037] Figure 2 It is a schematic structural diagram of the triangular patches of the pipe wall of the present invention;

[0038] Figure 3 It is a schematic sectional view of the segmented part of the straight water pipe of the present invention;

[0039] Figure 4 It is a schematic sectional view of the segmented part of the elbow joint of the present invention;

[0040] Figure 5 It is a schematic diagram of the triangular patches at one end of the water pipe close to the die surface of the present invention;

[0041] Figure 6 It is a schematic diagram of the process for reading the parameters of each group of cooling water channels of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0042] Next, the technical solutions in the embodiments of the present invention will be clearly and completely described in conjunction with the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only a part of the embodiments of the present invention, rather than all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative efforts shall fall within the protection scope of the present invention.

[0043] Please refer to Figure 1-6 , the present invention provides a technical solution: a preprocessing method for the water channel parameters of thin plate hot stamping simulation, including the following steps:

[0044] Step 1, establish a 3D fluid simulation model of the cooling water channel;

[0045] Step 2: Divide the 3D fluid simulation model of the cooling water channel into a straight pipe part and an elbow joint part;

[0046] Step 3: For the straight pipe part, determine the center line of the water outlet pipe, which is a straight line. Segment it according to the center line of the water pipe, with each segment being 20 - 40 mm. Determine the center point of each segment of the water pipe. Use a cross-section perpendicular to the center line to intersect with the triangular elements of the pipe wall of this section of the water channel to obtain the intersection surface of the cross-section and the pipe wall;

[0047] The two intersection surfaces of the cross-section and the pipe wall, as well as the pipe wall surfaces within two segments, form a closed volume; Generate multiple tetrahedrons from the closed surface, and calculate the volume of the object within the closed surface by superimposing the volumes of each tetrahedron;

[0048] Each segment of the water pipe after segmentation is a cylindrical surface. According to its volume and the length of the center line, and based on the principle of equal volume, obtain the diameter of the water pipe;

[0049] Step 4: For the elbow joint part, determine the center line of the water outlet pipe, which is an arc; Segment the center line of the water pipe according to the curvature change, divided into 6 - 10 segments. Determine the center point of each segment of the water pipe. Use a cross-section perpendicular to the center line to intersect with the triangular elements of the pipe wall of this section of the water channel to obtain the intersection surface of the cross-section and the pipe wall;

[0050] The two intersection surfaces of the cross-section and the pipe wall, as well as the pipe wall surfaces within two segments, form a closed volume; Generate multiple tetrahedrons from the closed surface, and calculate the volume of the object within the closed surface by superimposing the volumes of each tetrahedron;

[0051] Each segment of the water pipe after segmentation is approximately regarded as a cylindrical surface. According to its volume and the length of the center line, and based on the principle of equal volume, obtain the diameter of the water pipe;

[0052] Step 5: Determine and calculate the heat transfer coefficient of the water channel: Use fluid simulation to calculate the heat transfer coefficient of each triangular patch on the pipe wall of the water channel inside the mold. According to the above segmentation process of the water channel, find the triangular patches on each segment of the pipe wall and the heat transfer coefficient on each triangular patch;

[0053] Assume that there are N triangular patches on the side of this segment of the water pipe close to the mold surface. Calculate the average value of the heat transfer coefficients of the N triangular patches as the heat transfer coefficient of this segment of the water pipe;

[0054] Step 6: Group the water channel parameters: Group the above center line of the water pipe, the diameter of the water pipe, and the heat transfer coefficient of the water channel;

[0055] The specific grouping method is as follows: First, divide the diameter of the water pipe into X groups of water pipe diameter data according to the diameter size of the water pipe. Then, divide each group of water pipe diameter data into Y groups according to the heat transfer coefficient of the water pipe. The grouped data is written into an igs file. Each igs file contains the water pipe diameter data, the center line data, and the corresponding heat transfer coefficient data of the segmented section where the water channel is located;

[0056] Step 7: Use hot stamping simulation software to read the data after the above grouping to form a hot stamping simulation model.

[0057] Among them, the water pipe wall of the cooling water channel is composed of triangular patches, and the inside of the water pipe of the cooling water channel is 3D finite element tetrahedral elements.

[0058] Among them, in Step 3, the calculation formula for the cross-sectional diameter D1 of the water pipe in the straight pipe section is:

[0059]

[0060] In the formula, V is the volume of each segment of the water pipe in the straight pipe section, and L is the length of the center line of each segment.

[0061] Among them, in Step 4, the calculation formula for the cross-sectional diameter D of the water pipe in the elbow joint section is:

[0062]

[0063] In the formula, V is the volume of each segment of the water pipe in the straight pipe section, and L is the length of the center line of each segment.

[0064] Among them, in Step 5, the calculation formula for the heat transfer coefficient of each section of the water channel is:

[0065]

[0066] In the formula, S i is the area of the i-th triangular patch in this section of the water channel; H i is the heat transfer coefficient of the i-th triangular patch in this section of the water channel.

[0067] Among them, in Step 6, the grouping of water channel parameters is specifically as follows:

[0068] The diameter range of all segmented water pipes is a - b mm. Divide a - b mm into X equal parts from small to large, so as to divide the water pipe diameter into X groups of water pipe diameter data;

[0069] Each group of water pipe diameter data contains different heat transfer coefficients, and the range of the heat transfer coefficient is c - d W / m 2 ·K. Divide c - d W / m 2 ·K into Y equal parts from small to large, so as to divide this group of water pipe diameter data into Y groups of heat transfer coefficients;

[0070] Further, for example, the diameter range of the water pipe is 9 mm - 32 mm. The range of 9 mm - 32 mm is evenly divided into 6 groups from small to large, with X being 6. The diameters of the 6 groups of water pipes are 9 - 12 mm, 13 - 16 mm, 17 - 20 mm, 21 - 24 mm, 25 - 28 mm, and 29 - 32 mm respectively;

[0071] Each group of water pipe diameter data contains different heat transfer coefficients, and then the water channel heat transfer coefficients in each group of water pipe diameter data that are similar are grouped again; for example, among the water pipes with a diameter range of 9 - 12 mm, the average heat transfer coefficient is 8000 - 22000 W / m 2 ·K. The range of 8000 - 22000 W / m 2 ·K is evenly divided into 14 groups from small to large, with Y being 14 (the range of 8000 - 9000 W / m 2 ·K is divided into one group, the range of 9000 - 10000 W / m 2 ·K is divided into one group, and so on. The range of 8000 - 22000 W / m 2 ·K is evenly divided into 14 groups); then, according to the above grouping, igs files are compiled. Each group of igs files contains the water pipe diameter data, center line data, and corresponding heat transfer coefficient data of the water channel in the segmented section; when reading, the water pipe diameter data, center line data, and corresponding heat transfer coefficient data in the water pipe of the corresponding segmented section are read in sequence.

[0072] In summary, the present application converts the three - dimensional pipeline fluid simulation results into the results on a two - dimensional pipeline, discretizes and segments the three - dimensional pipeline, calculates the center line, diameter, and heat transfer coefficient of each section of the water channel according to the three - dimensional pipeline fluid simulation results; groups the center line, diameter, and heat transfer coefficient of each section of the water channel within a certain range of changes, outputs the center line igs format file for each group, and names it according to a certain format; using these discretized 2D water channel data in the hot stamping simulation model can improve the hot stamping simulation accuracy;

[0073] Converting the three - dimensional pipeline fluid simulation results into the results on a two - dimensional pipeline, these results can be applied in commercial software (such as Autoform, Pamstamp, etc.) to simulate the influence of the difference in the cooling water flow velocity inside the mold on the stamping forming process; some commercial software cannot read the three - dimensional water pipe geometric model and can only read the two - dimensional water pipe geometric model parameters, that is, the center line of the water pipe and the diameter of the pipe.

[0074] Based on the water channel flow velocity simulation result file, the cooling water pipe is segmented. For each segment, according to the principle of equal volume, the center line is calculated, and the heat transfer coefficient takes the average value of the heat transfer coefficient of the water pipe on the side of the mold release surface of the water pipe wall. After segmentation, even for the same straight water pipe, the differences in the heat transfer coefficients at different parts can be reflected, and the water channel diameter and heat transfer coefficient at the joint part can also be reflected and then enter the simulation model;

[0075] By adopting the above technical solutions, the differences in the heat transfer coefficients of the water channels at various parts can be considered in the hot stamping die simulation model, improving the accuracy of the hot stamping simulation.

[0076] Although the embodiments of the present invention have been shown and described, those of ordinary skill in the art can understand that various changes, modifications, substitutions, and variations can be made to these embodiments without departing from the principles and spirit of the present invention. The scope of the present invention is defined by the appended claims and their equivalents.

Claims

1. A method for preprocessing water channel parameters for hot stamping simulation of thin plates, characterized in that: The following steps are involved: Step 1: Establish a 3D fluid simulation model of the cooling water channel; Step 2: Segment the cooling water channel 3D fluid simulation model into a straight pipe part and an elbow joint part; Step 3: For the straight pipe part, determine the center line of the outlet pipe, which is a straight line. Divide the pipe into sections according to the center line, with each section measuring 20-40 mm. Determine the center point of each section of the pipe, and use a section perpendicular to the center line to intersect the triangular unit of the pipe wall of this section of the waterway to obtain the intersection of the section and the pipe wall. The intersection of the two cross sections and the tube wall, as well as the tube wall surface in the two sections, constitute a closed volume; the closed surface is generated into multiple tetrahedrons, and the volume of the object in the closed surface is calculated by superimposing the volume of each tetrahedron; Each segment of the water pipe after segmentation is a cylindrical surface. According to its volume, centerline length, and the principle of equal volume, the diameter of the water pipe is obtained; Step 4: For the elbow joint, determine the center line of the outlet pipe, which is an arc; divide the center line of the water pipe into 6-10 sections according to the change in curvature, determine the center point of each section of the water pipe, and use a section perpendicular to the center line to intersect with the triangular unit of the pipe wall of this section of the waterway to obtain the intersection surface between the section and the pipe wall; The intersection of the two cross sections and the tube wall, as well as the tube wall surface in the two sections, constitute a closed volume; the closed surface is generated into multiple tetrahedrons, and the volume of the object in the closed surface is calculated by superimposing the volume of each tetrahedron; Each segment of the water pipe after segmentation is a cylindrical surface. According to its volume, centerline length, and the principle of equal volume, the diameter of the water pipe is obtained; Step 5: Determine and calculate the heat transfer coefficient of the water pipe: Use fluid simulation to calculate the heat transfer coefficient of each triangular facet of the water channel wall inside the mold. According to the above segmentation of the water channel, find out the heat transfer coefficient of each segment of the pipe wall triangular facet and each triangular facet; Assume that there are N triangular facets on the side of the water pipe close to the profile, and calculate the average of the heat transfer coefficients of the N triangular facets as the heat transfer coefficient of the water pipe; Step 6, water channel parameter grouping: group the water pipe centerline, water pipe diameter and water channel heat transfer coefficient; The specific grouping method is: first, divide the water pipe diameter into X groups of water pipe diameter data according to the diameter of the water pipe, and then divide each group of water pipe diameter data into Y groups according to the heat transfer coefficient of the water pipe. The grouped data are written into igs files. Each group of igs files contains the water pipe diameter data, center line data and corresponding heat transfer coefficient data of the segment where the water channel is located; Step 7: Using hot stamping simulation software to read the grouped data to form a hot stamping simulation model; Among them, in step 5, the calculation formula of the heat transfer coefficient of each water channel is: In the formula, S i is the area of ​​the i-th triangle in this waterway; H i is the heat transfer coefficient of the i-th triangle in this water channel.

2. The method for preprocessing parameters of a thin plate hot stamping simulation water channel according to claim 1, characterized in that: The water pipe wall of the cooling water channel is composed of triangular facets, and the interior of the water pipe of the cooling water channel is a 3D finite element tetrahedron unit.

3. The method for preprocessing parameters of a thin plate hot stamping simulation water channel according to claim 1, characterized in that: In step 3, the calculation formula for the water pipe cross-section diameter D1 of the straight pipe section is: Where V is the volume of each segment of the straight pipe section, and L is the length of the centerline of each segment.

4. The method for preprocessing parameters of a thin plate hot stamping simulation water channel according to claim 1, characterized in that: In step 4, the calculation formula for the cross-sectional diameter D of the water pipe at the elbow joint is: Where V is the volume of each segment of the straight pipe section, and L is the length of the centerline of each segment.

5. The method for preprocessing parameters of a thin plate hot stamping simulation water channel according to claim 1, characterized in that: In step 6, the waterway parameters are grouped as follows: The diameter range of all segmented water pipes is a-bmm. Divide a-bmm into X parts from small to large, so that the water pipe diameter is divided into X groups of water pipe diameter data; Each group of water pipe diameter data contains different heat transfer coefficients, and the range of heat transfer coefficients is c-dW / m 2 K, c-dW / m 2 K is divided into Y parts from small to large, so that the group of water pipe diameter data is divided into Y groups of heat transfer coefficients.

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