CN104056968A - Die structure optimizing method taking service life into account - Google Patents

Abstract

The invention discloses a method for optimizing the mold structure considering the service life: the method optimizes the high-strength mold structure, effectively reduces the stress concentration of the mold structure in the stamping process, and improves the fatigue life of the mold. The method is The development of advanced high-strength steel stamping die and the check of die strength provide a reference.

Description

A Method of Die Structure Optimization Considering Service Life

technical field

The invention relates to a method for optimizing a mold structure, and belongs to the technical field of stamping molds for automotive panels.

Background technique

With the development of modern automobiles, people have new requirements for automobile safety and fuel economy. The use of advanced high-strength steel materials is a good way to increase the strength of the body and reduce energy consumption. Advanced high-strength steel has the characteristics of good formability, high strength, and excellent impact energy absorption capacity. It is a good way to reduce the thickness of the material by using high-strength steel materials, so as to realize the lightweight of the vehicle body. High-strength steel stamping requires higher forming force, and the die stress is greatly increased. In the case of alternating stress generated by cyclic loading, high load, high impact force and stress concentration, the mold is prone to deformation and fracture failure due to fatigue. In addition, the hardness of the advanced high-strength steel plate is close to the mold material itself, which accelerates the wear of the working surface of the mold and greatly reduces the life of the mold. The abnormal failure and damage of the mold caused by the fatigue damage of the advanced high-strength steel mold will not only affect the quality of the produced products, but also cause waste of mold materials and working hours, resulting in reduced production efficiency and increased production costs.

Contents of the invention

In order to explore the structure optimization method of high-strength dies, the present invention proposes a structure optimization method considering the service life. Fig. 1 is a flow chart of the die structure optimization method based on fatigue analysis in the present invention, which mainly includes the following steps:

(1) Use the finite element method to establish the mesh model of the die, use solid elements to discretize the die, and define boundary conditions such as material properties, motion parameters, loads, and constraints; (2) Perform finite element simulation on the stamping process of the die to obtain Stress analysis results of the mold; (3) According to the stress distribution results of the mold, the strength of the mold is checked according to the material requirements. If there is no area where the stress exceeds the yield limit (tensile limit) or the stress is close to the yield limit (tensile limit) in the stress cloud map, If it proves that the mold structure meets the strength requirements, go to the next step, otherwise it proves that the mold structure does not meet the strength requirements. (4) Extract the load spectrum of the finite element model nodes in dangerous parts, set the relevant parameters of fatigue analysis, carry out fatigue analysis on the mold structure, check the fatigue strength of the mold, and estimate the fatigue life of the mold; (5) According to the stress analysis and fatigue analysis results, the The structure of the mold is optimized to reduce the stress concentration of the mold and improve the fatigue life of the mold. During the use of the mold, the service life mainly depends on the fatigue life, which can be converted into the service life according to the safety factor.

The present invention compares the advantage of prior art:

(1) Provide a basis for the selection of mold materials and reduce the waste of mold materials; (2) Estimate the fatigue life of the mold and provide a basis for the service life of the mold; (3) Optimize the mold structure and reduce the stress concentration of the mold, Improve the life of the mold; (4) provide a reference for mold design and shorten the product development cycle.

Description of drawings

Figure 1 Flow chart of die structure optimization method based on fatigue analysis

Fig. 2 Cloud map of the maximum equivalent stress distribution of the die during the stamping process

Figure 3 Sorting of the maximum equivalent stress of the mold nodes (from large to small)

Figure 4 Die fatigue analysis results

Figure 5 Binder ring structure adjustment

Fig.6 Cloud diagram of the maximum equivalent stress of the optimized blank holder structure

Fig.7 Comparison of maximum equivalent stress of blank holder structure before and after optimization

Figure 8 optimized mold fatigue analysis results

Detailed ways

The present invention will be further described below in conjunction with a method for optimizing the mold structure that considers the service life described in the present invention:

Taking the structural optimization of the blankholder of a single-action deep drawing die with a design life of 1 million stampings as an example. The sheet material is DP780 high-strength steel, and the material of the blank holder is HT300. Establish the finite element mesh model of the mold in the finite element software, and set the boundary conditions such as material parameters, motion parameters and motion constraints of the finite element simulation. The finite element simulation of the die stamping process is carried out. The finite element analysis results are shown in Figure 2. The maximum concentrated stress appears at the inner corner of the blank holder, and the maximum equivalent stress is 252MPa. HT300 is made of cast iron, and the strength check is based on the tensile limit. The maximum equivalent stress of the blank holder during the stamping process is less than the tensile limit of the material by 300MPa, which meets the strength requirements. Next, fatigue analysis is carried out. Figure 3 shows the detailed data of the node stress of the finite element model of the blank holder. The node number 169658 has a maximum equivalent stress of 252MPa. This node is selected as the object of fatigue analysis. Import the node load in the post-processing module of the finite element software, according to the fatigue performance parameters of the binder ring material, combined with the theory of linear fatigue cumulative damage, set up 1 million cyclic loading conditions, and perform fatigue analysis on the binder ring, the fatigue analysis results are shown in the figure As shown in 4: Under the condition of 1 million cycles of loading, the fatigue cumulative damage coefficient D≈1.3 of the blank holder. Fatigue cumulative damage coefficient D>1, fatigue damage occurs when 1 million cycles of loading.

In the 3D modeling software, the structural optimization of the stress concentration dangerous parts is carried out. The sharp change of the section of the part is one of the main reasons for the stress concentration. The adjustment of the blank holder structure is shown in Figure 5. The original design fillet radius of the four corners inside the blank holder structure is R=30mm, and the modified fillet radius is R=50mm. Re-establish the finite element model of the mold, and perform finite element simulation on the stamping process of the mold. The cloud diagram of the maximum equivalent stress of the modified blank holder structure is shown in Figure 6, and the curves of the maximum equivalent stress of the blank holder structure with time before and after the modification of the stamping process are shown in Figure 7. It can be seen from the simulation results that after the structure is optimized, the peak value of the maximum equivalent stress of the blank holder is reduced to 241MPa. The stress concentration phenomenon at the inner corner of the blank holder has been controlled to a certain extent. During the whole stamping process, the average value of the maximum equivalent stress has been significantly reduced compared with that before optimization. Fatigue analysis was carried out on the optimized blank holder structure, and the fatigue analysis results are shown in Figure 8: the cumulative damage coefficient D≈0.89 for 1 million cycles of loading. Cumulative damage coefficient D<1, no damage occurs within 1 million cycles of loading. After optimization, the fatigue life of the blank holder structure is improved, and the fatigue life of the blank holder structure estimated by the fatigue analysis software is about 1.116 million times.

The above descriptions are only preferred examples of the present invention, and are not intended to limit the protection scope of the present invention. Any modifications, equivalent replacements and improvements made within the spirit and principles of the present invention shall be included within the protection scope of the present invention.

Claims (6)

1. consider a method for the Optimizing die structure in service life, it is characterized in that comprising the following steps:

(1) by Finite Element Method, set up the grid model of mould, with solid element, mould is carried out discrete, definition material properties, kinematic parameter, loading environment, constraints.

(2) mould punching process is carried out to finite element simulation, obtain the stress analysis result of mould

(3) according to mold stresses analysis result, check mould structure intensity, if meet requirement of strength, enter next step, otherwise adjust mould structure according to stress analysis result, return to step (1).

(4) according to mold stresses distribution results, determine the moment and position that in punching course, the maximum concentrated stress of mould occurs, this position is the danger position that fatigue rupture may occur mould.

(5) extract dangerous position FEM model panel load spectrum, analysis of fatigue relevant parameter is set, mould structure is carried out to analysis of fatigue, check the fatigue strength of mould, estimation mould fatigue life.If mould meets fatigue life, require service life to illustrate that mould structure meets design requirement, otherwise carry out next step.

(6) according to stress analysis and analysis of fatigue result, adjust mould structure, return to step (1), re-start finite element modeling, finite element simulation, check mould structure intensity, check mould fatigue strength flow process, until mould structure meets design requirement.

2. a kind of method of considering the Optimizing die structure in service life according to claim 1, is characterized in that: in step (1), it is discrete that mould selects solid element to carry out, and plate selects shell unit to carry out discrete.

3. a kind of method of considering the Optimizing die structure in service life according to claim 1, is characterized in that: in step (2), the whole punching course of mould is carried out to emulation, finite element simulation is exported the stress analysis result of a plurality of time steps.

4. a kind of method of considering the Optimizing die structure in service life according to claim 1, is characterized in that: in step (4), according to stress distribution cloud atlas, determine the moment and position that in whole punching course, the maximum concentrated stress of mould occurs.

5. a kind of method of considering the Optimizing die structure in service life according to claim 1, is characterized in that: in step (5), from stress analysis destination file, extract the panel load spectrum of dangerous position FEM model.

6. a kind of method of considering the Optimizing die structure in service life according to claim 1, is characterized in that: in step (6), adjust mould structure, until meet design requirement die life according to stress analysis and analysis of fatigue result.