In order to simulate the thermal processing process of materials, it is necessary to understand the thermophysical parameters, high temperature mechanical parameters, geometric parameters, constitutive parameters, contact, friction, interface gap, and gas of the workpiece and mold (or mold, medium, filling material, etc.) materials Data of various initial and boundary conditions such as precipitation and latent heat of crystallization. Without these data, the model is just an empty shelf; and the accuracy of these data has a great influence on the calculation results. For this reason, recently attaches great importance to the acquisition of these basic data. For example, in order to obtain accurate friction boundary data, most of the research projects of forging process simulation carried out special friction experiments to measure the friction coefficient, and found that the commonly used Coulomb’s law is quite different from the actual situation.
The general way to obtain the thermophysical and mechanical parameter values of materials is: general materials mainly rely on look-up tables; special materials are provided by users; high temperature data obtained by general experiments cannot be extrapolated. 1.6 In a parallel environment, process simulation is integrated with other technical aspects of the production system and becomes an important part of the advanced manufacturing system. At the beginning, process simulation was mostly performed in isolation, and the results were only used to optimize the process design itself, and mostly for single parts Production of small batches of rough parts. In recent years, it has gradually entered the advanced manufacturing system of mass production, achieving the following three different ways of integration.
(1) Integration with product and mold CAD/CAE/CAM systems The National Center for Advanced Metalworking Technology (NCEMT) is developing RP2D (Rational Product/process Design) technology in a concurrent engineering environment with funding from the Navy. Combine casting process simulation with product, mold design and processing.
(2) Integration with parts processing and manufacturing system: In the parts processing and manufacturing system, process simulation is an important supporting technology, and efforts are made in the direction of using the simulation results as the parameters of the closed-loop control of the system. The “near-zero margin agile and precision stamping system” and “intelligent resistance welding system” researched by the Wu Xianming Manufacturing Center in the United States; the “sheet metal forming computer integrated control system” researched by Northwestern University (the technical route is shown in Figure 2), etc. this type.
(3) Realize integration with the safety and reliability of parts: In the research of important complex castings in aviation, Northwestern University linked the simulation results with the performance of the castings, especially the safety and reliability, and developed a safety critical design system for castings (Safety critical casting design system), used to guide the damage tolerance design of castings. 1.7 Based on commercial software, improve the combination of research and popularization
(1) After years of research and development, a batch of thermal processing technology commercial software has been formed, including MAGMA, PROCAST, SIMULOR, SOLDIA, SOLSIAR, AFSSolidification System3D (casting), DEFORM, AUTOFORGE, SUPERFORGE (volume plastic forming), DYNA3D, PAM -STAMP, ANSYS (sheet plastic forming), ABAQUS (welding), etc.
(2) It has been widely used in the production of casting and forging industries: For example, about 10% of foundry plants in Japan have adopted this technology; Ford and General Motors of the United States have already used the numerical simulation of the sheet metal stamping process when developing new models. As an important technical link, France has applied this technology to verify and optimize the forging process of the 400-ton nuclear power rotor forging, ensuring a successful manufacturing.
(3) Numerical simulation has gradually become an important means and method of new process research and development. In industrialized developed countries (such as the United States), the application of commercial software for numerical simulation has become a basic research method for achieving technological innovation and developing new processes as important as experiments.
(4) Choosing suitable commercial software as the software platform, combining with specific problems, conducting research on improvement and improvement, has gradually become a faster, better, and more economical research method. The specific methods are:
①Perform theoretical research on some technical problems of existing software; ②Insert self-compiled software modules to solve specific problems; ③Apply theoretical analysis compensation method, experimental compensation method, etc., to find and eliminate commercial software errors, and make the simulation results more Accurate; ④Cooperate with software companies to increase software functions and realize software upgrades. 2. Suggestions on the simulation research and application of thermal processing technology in my country
At the end of the 1970s in my country, starting from the foundry industry, research in this field was carried out. For more than ten years, with the support of the Ministry of Machinery, the National Science and Technology Commission, and the National Natural Science Foundation, research in this field has been carried out in full swing. Many units across the country have invested in this work, and a large research boom has been formed throughout the country. . The research work has basically followed the pace of foreign technology frontiers, has moved from macroscopic simulation to microstructure simulation stage, and has carried out simulation integration work under the concurrent engineering environment. Especially in 1997, the “dynamic simulation of the thermoforming process of metal materials and the optimal control of tissue performance and quality” proposed by a number of domestic research institutes and universities was jointly funded by the National Science and Technology Commission and the Ministry of Machinery (Foundation), and was selected as a national climber. The planned pre-selected projects provide good conditions for my country to catch up with the world’s advanced level. Based on the analysis of this field’s research history and technology development trends, combined with my country’s situation, the following development suggestions are put forward: 2.1 Strengthen the commercialization of simulation software
Through years of research, my country has formed some quasi-commercial software, such as FTSOLVER 4.0, SIMU-3D, etc. However, compared with industrialized countries, there is a big gap. We should adopt a variety of methods (independent development, cooperative development with foreign software companies, inserting independent development modules into existing commercial software, and realizing software upgrades) to speed up simulation Software commercialization work, developed commercial software with independent copyright. Special attention should be paid to the use of relatively mature software platforms at home and abroad (especially pre- and post-processing) to avoid starting from scratch and doing low-level repetition. 2.2 Vigorously popularize mature thermal processing technology simulation technology
It is necessary to popularize thermal processing technology simulation technology in factories and research units (including university research groups), making it an important means for optimizing process design, scientific research, and technological innovation. The popularization method can be to purchase and use commercial software, or to adopt more mature domestically developed single technologies or modules. 2.3 Attach importance to the use of physical simulation and testing technology to improve the accuracy of numerical simulation
While attaching importance to the research of process mathematical models and algorithms, it is necessary to attach importance to strengthening physical simulation and testing technology, so that it can play an important role in revealing the essence of the process, checking and verifying numerical simulation results, and improving simulation accuracy. 2.4 Concentrate superior strength, aim at limited targets, and climb the world advanced level. Some of the current research work in my country has approached or reached the world’s advanced level. Such as: welding solidification crack accurate evaluation technology and cracking criterion; welding hydrogen-induced cracking accurate evaluation technology and cracking criterion; metal thermoplastic constitutive relationship with dynamic recrystallization process; three-dimensional plastic forming grain size evolution simulation and microstructure prediction; Semi-display time integral finite element algorithm of sheet metal forming simulation; thermal stress constitutive equation and simulation simulation of metal material quasi-solid phase zone; three-dimensional simulation and optimization of electroslag casting process; microstructure simulation of ductile iron and nickel-based alloy; Theoretical analysis and simulation of the strain component of the elastic-plastic stress field under the condition of solid phase transition; the simulation of metal hot forming under concurrent engineering environment.
We should aim at the above-mentioned limited goals, concentrate our strengths, work hard on key problems, and strive to make greater achievements and climb the forefront of world science and technology. 2.5 Multi-channel funding for thermal processing technology simulation technology research
In addition to the national climbing plan funding basic and cutting-edge research work, various national and departmental programs should focus on the research, development and application of process/process simulation technology to support work at different levels.