管材液压胀形成形极限图构建方法的研究-机械制造及其自动化专业论文.docxVIP

IV IV Abstract Abstract Tube hydroforming (THF) is an attractive manufacturing process in automotive industry, and forming limit diagram (FLD) is a significant strategy to assess the formability of THF. The FLD for THF is proved to be a scientific and reasonable tool to assess actual production, and has great value for research. The forming limit strain state of an element at the middle of the tube can be reflected in the FLD for THF. The geometric shape of FLD for THF is various due to the influences of many factors especially the strain path. Therefore, it is badly need to discuss the establishment method of FLD for THF and to discuss the change rules of FLDs for THF under various strain paths has practical significance. In present study, the forming behavior of the thin-walled tube (1Cr13Mn9Ni1N) in the THF process, the equivalent strain rates at potential fracturing and its adjacent nodes and the influence of the influences of changing strain path for THF were investigated on the combination of theoretical analysis, experimental study and finite element (FE) simulations. The main contents of the research in present study were concluded as following. (1) The deformation condition and loaded condition of THF process were analyzed; the common failure patterns during THF process were listed; and the specify conditions that the failure patterns during THF process to be taken place were discussed. (2) The FE models of the THF process system were built based on the experimental setups; and the reliability of the FE models was confirmed by comparing the sectional geometrical parameters and the forming failure of the components which are respectively deforming in the FE simulation and the experiments. (3) A method of predicting the FLD for THF was developed based on finite element (FE) simulation with the strain rate change criterion (SRCC) as a failure criteria of identify localized necking; and the results show that this prediction method bears