薄壁圆管塑性弯曲成形的失稳起皱与成形极限

Precision forming process of thin-walled tube NC bending is showing an inexorable tendency to improve and develop tube bending process into advanced plastic processing forming technology. However, It is a complex process under coupling interactive multi-factor effects and with the probability of wrinkling onset. Particularly, the development of aviation, aerospace and Hi-Tech requires bent parts to be thinner in wall-thickness, largrer in tube diameter, smaller in bending radius, and precise in forming, the prediction and control of wrinkling has become a difficult and key problem to be solved urgently in the research and development of the process. Consequently, numerical simulaton research on analyazing and predicting the wrinkling onset during the tube bending process, using combining the rigid-plastic FEM with energy criteria, has been made, which is important to developing the theory and technology of precision forming process of thin-walled tube NC bending, improving the product quality, shortening the design cycle, and reducing the development cost.. According to geometric feature of practical winkling wave NC tube bending process, A reasonable mathematic description of the winkling wave initiated on the compressed wall of tube during the bending process is proposed. Prediction criteria for the wrinkling onset is established based on the theory of thin-walled shell bending and minimum energy principal; then how to combine the criteria with the FEM simulation system to make the numerical prediction of wrinkling into reality is also resolved, which makes it possible to predict the wrinkling during a smaller bending radius process for tubes with larger diameter/thickness ratio. a reasonable FEM model has been set up and the key technology problems related to the 3D rigid-plastic FEM simulation are have been solved. A numerical wrinkling prediction system has been developed for the NC thin-walled bending process, which can be used to both predict the wrinkling phenomena and analyze the bending process. Using the system, characteristics have been obtained for the stress-strain distribution and variations of plastic zone and the ratio of plastic forming energy to wrinkling energy during the bending process of aluminum and stainless tube, which may provide a basis for research into the wrinkling mechanism; The influence of processing parameters on the minimum-bending radius(namely, the forming limit determined by wrinkling) has been revealed, which may serve as a significant guide to the determination and optimization for the relevant process and dies. .

薄壁圆管塑性弯曲成形过程力学分析有限元建模，计算机仿真；管弯曲失稳起皱的实验研究，失稳起皱波形函数的确定；基于最小能量原理的管弯曲失稳起皱准则的建立；管弯曲成形极限与规律的数值分析；基于成形极限与精度提高目标的数控弯曲管工艺优化。为管弯曲的失稳起皱预测，成形极限与精度的提高及数控弯曲工艺的应用与发展提供理论，方法和技术。