知识与财富的链接
屈服准则作为金属材料进入塑性的判据,在结构强度设计、金属塑性成型等领域得到广泛应用。为预测拉-压非对称金属的屈服行为,采用将各向异性和拉-压非对称性解耦的方法,把Banabic非二次式屈服准则推广到拉-压非对称,建立一个能同时描述塑性各向异性和拉-压非对称性的屈服准则,可视为广义的Banabic非二次式屈服准则。为了评估所建立屈服准则的预测能力,将其应用到AA5754-O铝合金的屈服及Cu-Al-Be形状记忆合金的相变转换起始面预测中,并与丁发兴等提出的损伤比屈服理论进行对比。结果表明,广义Banabic非二次式屈服准则和损伤比屈服理论都能很好地预测AA5754-O铝合金的屈服以及形状记忆合金Cu-Al-Be的相变转换起始面。2个准则都非常准确地预测了AA5754-O铝合金压缩屈服应力随取向的变化规律,二者的预测结果完全一致。广义Banabic非二次式屈服准则能很好地模拟AA5754-O铝合金在双向等拉(压)区附近的大曲率屈服轨迹,损伤比屈服理论则明显高估了其屈服应力;对于Cu-Al-Be形状记忆合金起始相变转换“屈服”面的预测,损伤比屈服理论预测精度高于广义Banabic非二次式屈服准则,但不能保证“屈服”面的外凸性。此外,广义Banabic非二次式屈服准则可通过单轴加载屈服强度和塑性应变比r值标定准则的系数,在缺乏双向加载实验数据的情况下更便于工程应用。因此,推广的Banabic非二次式屈服准则可用于拉-压非对称金属的屈服和塑性变形计算,极大地拓宽了经典Banabic非二次式屈服准则的应用范围。
Yield criterion is widely used as a criterion for the onset of plastic deformation of metallic materials in structural design and plastic forming of metals. In order to predict the yield behavior of tension-compression asymmetric metals, the Banabic non-quadratic yield criterion was extended to tension-compression asymmetry by using a method that decouples anisotropy and tension-compression asymmetry. The established yield criterion, which had the ability to describe both plastic anisotropy and tensile-compressive asymmetry, can be regarded as a generalized Banabic non-quadratic yield criterion. In order to evaluate the prediction ability of the established yield criterion, it was applied to the prediction of the yielding of AA5754-O aluminum alloy, as well as the prediction of phase transition initiation surface of Cu-Al-Be shape memory alloy, and compared with the damage ratio yield theory proposed by Ding Faxing, et al. The results show that both the generalized Banabic non-quadratic yield criterion and damage ratio yield theory can well predict the yielding of AA5754-O alloy, as well as the phase transition initiation surface of Cu-Al-Be. Both criteria can accurately predict the variation of compressive yield stress with orientation of AA5754-O aluminum alloy, and their predicted results are very close. The generalized Banabic non-quadratic yield criterion can well simulate the large curvature of the yield surface of AA5754-O near the equal-biaxial tension (compression) aera, but the damage ratio yield theory overestimates the yield stress in this aera obviously. For the prediction of the “yield” surface at the onset of the phase transition in Cu-Al-Be, the damage-ratio yield theory predicts a higher accuracy than the generalized Banabic non-quadratic yield criterion, but does not guarantee the convexity of the “yield” surface. In addition, the coefficients of generalized Banabic non-quadratic criterion can be calibrated by the yield stresses and r-values for uniaxial loading in different directions, which makes it more convenient for engineering applications in the absence of bi-axial loading experimental data. Therefore, the generalized Banabic non-quadratic criterion can be used for yielding and plastic deformation calculations of tensile-compressive asymmetric metals, which greatly broadens the application scope of the classical Banabic non-quadratic yield criterion.
