Abstract: In order to analyze autofrettage theory of thick-walled cylinders, a bilinear hardening model was established and the analytical solutions of loading stresses, residual stresses and working stresses were derived based on the triple-shear unified strength criterion, which taken the strain hardening, Bauschinger effect, strength difference(SD) effect and the effect of intermediate principal stress into consideration. The optimal autofrettage pressure of thick-walled cylinder was deduced, the influences of ratio among tension stress and compression stress, strength criterion parameters were investigated respectively. In addition, the stress distributions of thick-walled cylinders between autofrettage and non-autofrettage, the bilinear hardening model and elastic-perfectly plastic model were compared. The results show that the optimum autofrettage pressure will increase with the increase of radius ratio and strength criterion parameter；the maximum equivalent working stress will decrease with the increase of radius ratio and strength criterion parameters, but increases with the increase of ratio between tension stress and compression stress; the maximum equivalent stresses in the elastic plastic junctions and the stresses of thick-walled cylinder along the wall thickness are well- distributed; compared with the elastic-perfectly plastic model，the radius of elastic plastic junction and residual stress of bilinear hardening model are lower, meanwhile with the increase of autofrettage pressure, the difference becomes more and more obvious; the curve of equivalent stress along with radius ratio may provide reference for choosing the optimal wall thickness; autofrettage technique may improve the working stress distribution and ultimate bearing capacity of thick-walled cylinders.

Key words: thick-walled cylinder, triple-shear unified strength criterion, autofrettage analysis, bilinear hardening mode, equivalent stress

摘要： 基于三剪统一强度准则，考虑材料应变强化效应、包辛格效应、拉压异性及中间主应力的影响，采用双线性强化材料模型对厚壁圆筒进行自增强分析，得到了厚壁圆筒加载应力、残余应力和工作应力的解析解，提出了最佳自增强压力的计算方法，探讨了拉压比、强度准则变化参数的影响，比较了自增强处理和非自增强处理及双线性强化模型和理想弹塑性模型厚壁圆筒的应力分布差异。研究结果表明：厚壁圆筒的最佳自增强压力随半径比和强度准则参数的增大而增大；工作时的最大等效应力随半径比和强度理论参数的增大而减小，随拉压比的增大而增大；自增强等效应力的最大值在弹塑性分界面处，且应力沿壁厚的分布较均匀；与理想弹塑性模型相比，双线性强化模型所对应的弹塑性分界面半径和残余应力较小，且随着自增强压力的增大，两种模型的差值越来越大；等效应力随半径比的变化规律可为厚壁圆筒选择合理的壁厚提供一定的参考；自增强技术可改善厚壁圆筒工作时的实际应力分布，提高其极限承载能力。

关键词: 厚壁圆筒, 三剪统一强度准则, 自增强分析, 双线性强化模型, 等效应力