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Application of simulation technology in elastic springback

metal materials suitable for deep stamping are the most commonly used materials in sheet metal deformation processing. When encountering problems, people clearly know how to solve them, and elastic rebound is also a problem that people can master. However, these ordinary steels must be withdrawn from the application field of modern high-strength plates. Because new materials have StarTech in deformation processing: gb/t 12444 (2) 006 "wear test methods for metallic materials - test ring - test block sliding wear test"; Gb/t396083 "test method for sliding friction coefficient of plastics" is very difficult. The experience of elastic springback that people have mastered for many years is useless in the deformation and processing of new materials. High strength and ultra-high strength steel or aluminum alloy materials play an important role in the design of light structures. However, the greater elastic springback than ordinary deep stamping steel makes it difficult to determine its purpose. Therefore, it becomes very difficult to simulate deformation processing and predict material properties. In the deformation processing of high-strength steel, the lattice structure of the material also changes with the appearance of phase transformation. This phenomenon has not appeared in most metal material models

calculate elastic springback

the traditional plate crack and fold failure theory is based on people's observation of plate extension changes. When elastic springback plays a "role", the traditional failure prediction model is powerless. At this time, stress plays a key role, that is to say, it should have a high accuracy level

Figure 1 automobile C-pillar simulated by elastic springback simulation software

in the process of mold design and manufacturing, elastic springback is compensated by design software. The purpose is to select the workpiece that meets the technical requirements from the mold as much as possible (Figure 1). With the help of computer software, the number of mold test and debugging can be greatly reduced. In general, the testing and debugging time of deformation processing molds is very urgent, which is the last stage of the mold production process. In mold design, there are many uncertain factors, and each set of mold is a complex comprehensive mechanical component, a common role of the whole. Many works are carried out in parallel at the same time, and the conflicts and contradictions naturally affect the delivery time and manufacturing costs

Figure 2 deep stamping process diagram: mold (blue), pressing plate (red), punch (green)

Figure 3 deep stamping deformation processing action surface: pressing plate action surface (red), punch action surface (green), contraction flow surface (yellow) and workpiece (blue)

at the beginning, simulation technology is used to simulate mold parts to ensure the reliability of mold manufacturing. In this process, we should first check the problem of elastic springback to ensure that the elastic springback can be fully compensated from the geometric size to the shape. Then we can start to consider compensation measures. In order to implement these compensation measures, such as helping enterprises formulate product standards, providing free testing data for the development of new products and new processes, helping enterprises apply for invention patents, cooperating with enterprises in scientific research projects, and carrying out statistical analysis of copper product quality in Tongling City, auto defines three different areas in the mold for the experimental form software system that needs to be done in a high temperature environment (Figure 2). In the first region, elastic springback is fully compensated for equilibrium. In this area, each action surface, that is, each surface of the die that deforms the plate, matches the simulation results, and its shape is equivalent to the area of the product workpiece plus deformation compensation. The second area does not change. Its typical feature is that it remains unchanged after the mold is compacted. The third area is the area where the convex part in the plate design is located, which is the transition area between the above two areas, that is, the convex and concave area of the stamping workpiece. After these three areas are generated in the AutoForm software, the software system will automatically select the area (Figure 3). Workers can operate manually at any time in order to add their ideas to the three areas. The computer software will automatically analyze and determine the position and value of elastic rebound compensation for the final product. The direction of compensation is opposite to that of elastic springback. The mold that completes the compensation adjustment is the basis of the next simulation. Usually, after 2-3 times of such compensation and simulation, the parts that meet the requirements of the drawing can be obtained, and the residual elastic springback in the workpiece has been within the allowable range of tolerance

parameter simulation within the tolerance range

after the above compensation simulation of elastic springback, a simulation calculation result is obtained when the deformation processing parameters are unchanged. However, in the process of mass production, many working parameters of deformation processing are changing. Typical deviations and errors are often related to the characteristics of the material, such as plate thickness, strength or deformation processing properties caused by the rolling direction of the plate. Other influencing factors include friction, pressing force of plates, positioning accuracy of plates, etc., which also have a certain impact on elastic springback. In order to make the simulation calculation closer to the reality and provide more convincing simulation conclusions, it is necessary to use a large number of variable parameters within the specified tolerance limit to carry out the compensation simulation of elastic springback, that is, the "simulation" of practice

Figure 4 definition of three areas in the stamping die, so as to compensate the geometric shape of the workpiece filter

AutoForm sigma elastic springback compensation simulation software can automatically provide statistical evaluation results within the occurrence range of elastic springback and evaluate the stability of deformation processing (Figure 4). According to these statistical evaluation results, it is determined that the main factor affecting elastic springback is deviation. Thus, it is possible to predict the stamping production capacity at the early stage of the manufacturing process in China, which still needs to go a long way. The matching of deformation processing parameters can be carried out during the assignment of production process parameters, the formulation of stamping process plan, and even when modifying parts. AutoForm sigma simulation analysis system does not provide an absolutely accurate final product. On the contrary, it provides the best preparation for mass production

modern deformation processing materials, defective material models and high-precision grades have put forward high requirements for advanced simulation software in the field of sheet metal deformation processing. At the same time, simulation software R & D enterprises are also growing in this environment, and have developed elastic springback simulation software for plate processing that meets the requirements of practical application, providing a better solution for production practice

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