内压弯管在面内循环弯曲载荷作用下棘轮效应的研究

利用多轴试验机研究了内压及面内循环弯曲载荷作用下低碳钢弯管的棘轮效应。试验研究表明最大棘轮应变发生在顶线位置的环向。对于个别试件，内缘线位置也发现了环向棘轮应变，但所有试件的外缘线位置均未发现棘轮应变。内压不变时棘轮应变速率随面内循环弯曲载荷的增大而增大；面内循环弯曲载荷不变时，棘轮应变速率随内压的增大而增大。通过用户编程，采用Chen—Jiao—Kim随动强化模型，利用弹塑性有限元法对弯管进行了循环塑性分析。与试验结果相比，Chen—Jiao—Kim随动强化模型能给出较好的预测。采用C—TDF提出的等效塑性应变增量控制法确定了结构的棘轮边界。

Ratcheting Study of Pressurized Elbows Subjected to Reversed In-plane Bending

With a multi - axial test machine, ratcheting was studied experimentally for pressurized low carbon steel elbows under reversed bending. The maximum ratcheting strain occurred mainly in the hoop direction at flanks. Hoop ratcheting strain was found at intrados for individual specimen. No ratcheting strain was found at the extrados for all tests. Ratcheting strain rates grow with increase of the bending loading level at the same internal pressure or with an increase of internal pressure at the same bending load. Ratcheting simulation was performed by Elastic -plastic FEA with ANSYS in which Chen- Jiao - Kim kinematic hardening rules was applied by user programme. By comparing with the experimental data, it is found that predicted results simulate reasonably. Ratcheting boundary was determined by the equivalent plastic strain increment controlling method of C - TDF.