摘要：
With the methods of single-specimen and multiple-specimen, the subsequent yield surfaces of the copper underwent tension, torsion and combined tension torsion pre-deformation respectively are studied by crystal plasticity simulation comparing with the real test employing thin-walled tubular specimens. Not the variances of measured subse-quent yield surface but also the phenomena of subsequent yield surface appearing concave are discussed under considering different conditions, including different pre-deformation, the number of probing point, the test sequence of the probing points, and the specified offset strain, etc. On this basis, the rationality and validity of the two methods for subsequent yield testing are compared. The simulations probing yield surface are conducted using the FE model of thin-walled tubu-lar specimen, in which the crystal lattice orientation for each element is arranged randomly, associated with a modified crystal plasticity constitutive model that is able to reflecting the Bauschinger effect for material under reversed loading, so that the deformation characteristic of polycrystal can be exhibited. The loading procedure of modeling test is designed as same as the real test. The investigated results show that: (1) the proposed simulation method can reproduce the real test procedure, the simulated subsequent yield phenomena are found fairly consistent with that observed in actual experimen-tal measurements, which confirmed the rationality and validity of the method; (2) both the simulated and real tests show that the subsequent yield surface measured by using the thin-walled tube under combination of tension-torsion load may be concave, and the result tested by the single specimen method is more obvious in yield surface concave no matter for simulated or real test; (3) if the test material is fairly consistent in quality, the multiple-specimen method should be more reasonable than the single-specimen method for subsequent yield surface test.%通过纯铜薄壁圆管试样的实测和晶体塑性模拟,用单试样法和多试样法对分别经历拉伸、扭转和组合拉扭变形的试样后继屈服面进行研究.考虑预变形方式、测点数目、测试顺序和指定平移应变等不同条件,对后继屈服面测定结果差异及屈服面内凹现象进行探讨.在此基础上,比较了单试样和多试样两种方法的合理性与有效性.数值模拟采用能反映Bauschinger效应的晶体塑性模型,试样有限元模型每个单元的晶体取向均随机生成,能反映多晶材料变形特征.模拟试验加载过程与真实试验一致.研究表明:(1)采用本文方法可再现真实试验过程,模拟后继屈服面测试展示的现象与实测相近,证实了方法的有效性和合理性;(2)模拟测试与实测均发现,薄壁圆管组合拉扭加载测得的后继屈服面可能出现内凹,单试样法测得屈服面的内凹现象尤为显著;(3)若试验材料的材质比较一致,用多试样法测试后继屈服比用单试样法更合理.
