钉孔挤压强化弹塑性计算中形变理论适用性探讨

本文为了检验形变理论在计算钉孔挤压残余应力场的可用性,对同一模型分别釆用全量法和增量法进行有限元计算,计算结果表明:在小的挤压量下,即δ≤2％(挤压量δ定义为(D_棒-D_板)/D_板×100％),两种方法均可釆用,当挤压量较大,即δ>2％时,全量法的结果与边界条件吻合得不好,而增量法符合得很好。从实验结果看,用全量法计算的残余应力计算试件的疲劳裂纹起始寿命与实验结果相差较大,而增量法计算的该寿命则与实验结果接近。工程中的挤压过程大都釆用较大的挤压量,所以,形变理论不适合计算钉孔挤压的残余应力场。

AN ADAPTIVE STUDY OF DEFORMATION THEORY IN ELASTO-PLASTIC COMPUTATION FOR THE PROCESS OF COLDWORKING FASTENER HOLE

The residual stress around a coldworked hole is computed with elasto-plastic finite element methods of both flow theory and deformation theory. It is shown that: when M is small, for Alalloy LY12CZ, M≤2%, where M is defined as (Dmandre.-Dhole)/Dhole×100%, both of the two tneories can be used; when M is not small, for AI alloy, M>2%, the result of the former method fits with the boundary condition, but the latter theory is not. The initiate lives of super strength steel 30 CrMnSiNi 2 A plate with a coldworked hole are calculated by using the residual stress obtained with both of the two methods. It is shown that, the former result fits with the experimental result, but the latter is not. For the process of coldworking hole, M is generally not small, therefore deformation theory is fit for computing the residual stress around a coldworked fastener hole.