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Application status of precision forming technology abroad and its enlightenment to China's development

Digital precision forming technology mainly includes digital precision plastic forming and digital precision casting. Digital precision plastic forming technology is a technical system that integrates digital technology in the whole process of plastic forming and is based on system engineering, so as to realize high quality, high efficiency, low consumption and clean production. The research contents include: establishing a digital model based on computer graphics, interacting with different requirements by unified data exchange standards and engineering databases, and realizing the sharing of models and information; Based on the digital model, the product design based on precision plastic forming is carried out. Based on the digital model, the product performance analysis based on precision plastic forming process is carried out. Digital manufacturing of products includes digitalization of technological process and manufacturing equipment.

At present, the simulation of precision plastic forming process has entered the practical stage in industrialized countries. The finite element program ALPID (Analysis of Large Plastic Incremental Deformation) developed by Battelle Laboratory in the United States with the support of the US military is the beginning of numerical simulation technology of plastic forming. In the design and manufacture of engine panel dies in the United States, it is required that after the design is completed, it must be tested by computer simulation before it can be put into the manufacture of test soft dies. Biba of Quntor Company in Russia used numerical simulation method to optimize the forging die, which achieved the purpose of improving the life of the die and the accuracy of the parts. The specific method is to optimize die parameters, such as fillet radius, reduce stress concentration, and adopt shrink ring and insert.

At present, there are a lot of research hotspots in precision plastic forming, which are related to numerical simulation technology, such as mold design, sheet anisotropy, material springback, damage prediction, forming limit line and tube hydroforming technology.

General Motors Company of the United States has developed a digital development platform and system for stamping dies. The system uses a three-dimensional design platform to carry out parametric and variable design for dies, and develops the die surface based on expert system and manufacturability design, thus transforming the traditional technical die development process into digital development based on science. The system integrates decades of stamping process experience and specifications of general company, and uses numerical simulation software to analyze and modify the formability and quality of parts, so as to quantitatively predict and solve the problems in die development. Mold design, mold manufacturing, mold trial and stamping production are formed in a digital environment, and the accuracy of formability prediction reaches 9% ~ 95%, which overcomes the limitations of mold developers' personal experience, and the general mold trial can be completed in 1 ~ 2 days. Taking the stamping parts such as the body of military Hummer as an example, the digital die development system can reduce the die development cycle by 8% and the die cost by 5%. In addition, GM also organically combines optimization technology with numerical simulation technology to realize optimization based on numerical simulation.

Shim and Son of Yeungnan University in South Korea use sensitivity method to determine the initial shape of sheet metal, and determine the shape sensitivity through Pam2Stamp finite element simulation, which can optimize the drawing process design of sheet metal parts with arbitrary shape.

CA TIA method used by Canadian forming (FTI) company for metal sheet design simulation unifies design and analysis in one program. By simply changing the geometric shape, material characteristics or plate thickness, and using computer-aided optimization design, the simulation results play a role as an early warning system. Color features indicate that "the design of the workpiece is reliable", "there is a flanging trend" or "the workpiece has cracks on the red surface", thus realizing the optimization of process design. Digital precision casting technology refers to the comprehensive integration of digital technology in the casting process, including computer-aided engineering analysis (casting CAE), casting process computer-aided design (casting CAD), casting expert system and many other technologies.

At present, the research and application of information technology in foreign national defense craft casting engineering is getting deeper and deeper, and the casting technology level is being comprehensively improved. The United States and other developed countries have successfully completed the trial production of various key components such as aerospace, aviation and weapons by using computer-aided precision casting technology, and achieved obvious economic benefits.

the CIR program launched by the U.S. department of defense in 26 has carried out a number of projects related to foundry digitalization. For example, Purdue University undertakes the project of "Geometric Constraint Design Tool for Foundry Process", and recommends other improvement methods for foundry process. In order to improve the quality of castings, the research of this project will first collect "recommended design parameters" that have been confirmed by the industry, and then develop new casting design software and tools. The development of software tools will focus on the casting of complex structural parts and the influence of geometric characteristics of castings on metal casting process, with emphasis on sand casting process and metal mold casting process.

the Man Tech program of the U.S. department of defense also attaches great importance to the development and application of digital casting technology. For example, the Man Tech project of "Integrated Design of Steel Casting Oriented to Working Performance" undertaken by ABC2NACO Company aims to study the influence of shrinkage discontinuous structure on the structural properties of carbon steel and low alloy steel casting, and develop corresponding computer tools. The implementation of this technology will reduce the casting quality, increase the casting output, expand the application of steel casting, shorten the delivery cycle of order 2 and reduce the cost.

at the initial stage of developing the Delta 4 rocket core engine RS268, Lockheed Company of the United States created a working environment for concurrent development of integrated products, and completed the digital modeling of the engine by using advanced design tools and 3D modeling technology. The design of turbopump fully reflects the effect of the implementation of Rockdyne Advanced Process Integrated Development Project (RAPID). A model-centered horizontal integrated design system (HIDS) is established, and the HIDS three-dimensional digital model of the casting core is manufactured, and then the model is sent to the foundry to produce test pieces. Technicians can optimize the gate according to these test pieces, and can directly reflect various characteristics in the design of the casting, thus improving the casting quality.

after years of continuous development, the casting process simulation technology has developed from macro to micro, from experimental research to practical application, and now it has become a very mature engineering application technology, with a large number of practical simulation software and rich thermophysical properties database, which can accurately simulate the casting process of most alloys and realize process optimization design. Through numerical simulation technology, the structural manufacturability and casting process of castings are simulated, which provides an effective scientific basis for technicians to design a more reasonable casting structure and determine a reasonable process plan, thus avoiding the randomness of traditional structural design and process formulation relying on experience. In developed countries, 15% ~ 2% foundry enterprises have adopted solidification simulation analysis technology in production to accurately predict defects and improve casting yield. In recent years, domestic related enterprises and universities have successively carried out some research on digital precision forming technology, but the lack of systematic integration research can not achieve individual promotion of integration, local promotion of the whole, technological advantages can not be transformed into product advantages, and the level of precision forming technology in the whole industry has not jumped qualitatively. Therefore, domestic research on precision forming technology should strengthen independent innovation and break through key technologies. Such as product information modeling technology, process simulation and optimization technology, intelligent generation technology of mold design, etc., so as to realize the comprehensive integration of precision forming technology, improve the level of process design, further realize the integration of digital design and manufacturing, shorten the product development cycle and reduce the manufacturing cost. At the same time, we should strengthen the application of the results and improve the technical level of precision forming in the whole industry.