Analysis for twinning and slip in face-centered cubic crystals under axisymmetric co-deformation

The maximum work principle of Bishop-Hill was developed to analyze the axisymmetric co-deformation in face-centered cubic crystals (f.c.c.) for twinning on {111} 112 and slip on {111} 110 systems. The influence of ξ , the ratio of critical re- solved shear stress for twinning to slip, on the yield stress states and corresponding active slip or/and twinning systems for orientations in the standard stereographic triangle of cubic crystal was investigated systematically. The Taylor factors and the anisotropy of yield strength for three important orientations [100], [110] and [111] in orientation space were analyzed. It is found that the yield strength asymmetry for the case of axisymmetric de- formation of tension and compression can be explained based on the microscopic theory of crystal plasticity. The concept of orientation factor for twinning ability was proposed and the deformation mechanism map in the orientation space was established for the case of axisymmetric deformation. The deformation texture formation and development of f.c.c. crystals with low stacking fault energy for axisymmetric tension can be explained qualita- tively on the basis of analyzed results.     

面心立方金属{111}〈110〉滑移和{111}〈112〉孪生平面共生变形？…

将Ｂｉｓｈｏｐ－Ｈｉｌｌ最大功原理拓展于ｆｃｃ金属｛１１１｝〈１１０〉滑移和｛１１１｝〈１１２〉孪生两种机制同时起作用的平面共生变形。研究了不同临界剪切应力（ＣＲＳＳ）之比ξ对各理想取向的屈服应力状态及相应活化系的影响。分析结果表明,当ξ〉１／３ｊｆ ,Ｃ,Ｇ和Ｒｃｕ３种取向共同的活化系均为滑移系,不易孪生：其它５种取向共同的活化系均包括滑移系和孪生系,有孪生倾向。同时分析了取向空间里屈服强度各向     

既有管道与内衬叠合界面受力性能及计算方法

为获悉应用非开挖离心喷涂法对缺陷管道的修复效果,并揭示修复后界面及“管道-内衬”体系的破坏机理,建立两层叠合曲梁模型,并应用变截面法推导不同材料叠合曲梁结构的截面应力及界面应力的解析公式,以修复后管道受集中荷载作用的三边承载力试验为例,验证公式的准确性.给出“管道-内衬”体系协调变形的判断标准,即当界面抗力大于荷载时形成叠合结构,抗力小于荷载时形成复合结构.通过对相关参数分析,得到界面剪切应力τ和内衬厚度与既有管道壁厚比值β、弹性模量比η和既有管道直径D的简化公式,与力学模型的精确结果误差小于1%.最终给出既有管道不同破坏模式的内衬修复设计方法.