The Die Forming Strengthing Process And It's Finite Element Simulation

Residual compressive circumferential normal stresses around the hole reduce operating stress magnitudes to minimum values for cyclic tension and this enhances fatigue life and load-carrying capacity of structures. So Residual stresses is induced deliberately around the holes by means of cold expansion,shot peening,rolling and so on. Many researches indicate that the effectiveness of those strengthening technical processes mainly depend on the residual stress—strain field, whose magnitude and distribution have great influence on the fatigue performance of the components with hole. In order to achieve perfect residual stress—strain field, many attention has been given to how to set proper processing parameters.Based on the theory of die formed working progress(DFW) given by professor Sheng Wu Wang, this paper presents a combined approach consisting of experimental and F.E modeling of residual circumferential tangential stress distribution when forming holes in work pieces of 25~# carbon steel by DFW. Attention was given to those as below:1. Based on the MSC.MARC software, mechanical model of technological process for die forming is established, with which large deformation elasto-plastic analysis was conducted. The agreement of finite element method and experimental results is good enough. Through solving the model, the relationships between die forming deformation force, residual stress, friction factor and the modular angle of the die are obtained, under different contact conditions of workpiece with die forming, different rake angle of die and different expansion ratios of the inner diameter of workpiece. These will lay a foundation in theory in order to design die forming tools, to arrange the pass in front of forming progress and enhance quality of die forming working.2. An automatic integration optimization system of DFW parameters were built based on the ISIGHT platform, aimed to make residual compressive circumferential normal stresses around the hole smallest. The result reveals that the result is best under condition that die rake angel is equal to48.5~0, dieing depth1 .9, and friction factor 0.065.Combining the methods of tests and finite element simulation, the research of die forming process was conducted. What is more, based on Isight platform optimization design was obtained. All those work above will give preference to design dieing form tools and process parameters.