Numerical Simulation Of New Theory And New Technology Of Heavy Forgings

ABSTRACT AB STRACT Along with the rapid development of modem industry, such as energy, transportation and metallurgy, many heavy forgings with high quality are required. These forgings are made of ingots directly. Owing to both physical and chemical properties of metal material, there are inevitably shrinkage cavities, porosity and segregation in ingots. The larger the forgings size is, the more defects exist. Forging technology is needed to eliminate the defects to get high quality forgings. That is to say, with enough deformation, shrinkage cavities can be consolidated, porosity closed, segregation structure improved. To get this goal, there should be no tensile stress in the area where defects get together, or the situation be worsen. Upsetting and stretching are main deformation methods for heavy forgings, and exert great influence on forgings?quality. In this paper, the two working procedures are simulated by using commercialized software ANSYS. On upsetting, simulations of new upsetting theories are firstly implemented. By carrying both structural and thermal-structural couple field numerical simulation of upsetting cylinder and blank with cross section between two flat platens, the internal stress and strain distributions are given. According to the relationship between the distribution of stress and strain on the center symmetrical section and the reduction in height, the critical height width ratio (HID) for cylinder upsetting and the critical dimension ratio (A/H) for cross section blank upsetting are obtained. So the new forging theory for upsetting a cylinder and the rigid-plastic tensile stress mechanical model for upsetting a blank with cross section are verified and perfected. The discovery of cone-shaped rigid zero can explain the rigid-plastic mechanical model for upsetting a blank. Based on above simulations of new theories, the new forging technology for upsetting a cylinder with cone-shaped dies is simulated. Its even internal stress distribution and good stress state show that it is a creative one. The bi-axial tensile stress state with little height reduction can be explained clearly by the rigid-plastic mechanical model for upsetting a cylinder with cone-shaped dies. On stretching, the commonly used technology, stretching with two flat dies is analyzed based former research. Simulations of blanks with different tool width ratio (TV/H) and blank width ratio (B/H) under two load situations are implemented. The distribution of internal stress along center axis is obtained and compared with the results of upsetting a blank. It is shown that the effects of rigid ends on internal stress distribution axe influenced by both tool width ratio and blank width ratio, but not only one. So it is no sense considering only tool width ratio when studying axial stress or considering only blank width ratio for transverse stress. Thorough analysis 慖i .2 on center point抯 stress leads to the function between critical tool width ratio (W扝)~ and blank width ratio(B/H) and the relationship between critical blank width ratio (B/H)~ and tool width ratio(W/fI). The critical values of two parameters under different situation are firstly given roundly. The result not only prove the new theory of stretching with flat tools, but also lay a sound qua...