《v8_18_multi_msc_format》.ppt

E-N Theory Continued and Dealing with Multiaxiality Sharp and Mild Notches Refinements to the Neuber Method Neuber法是一种近似的应力-应变估算方法，适用于塑性应变仅发生在缺口附近The Neuber Method is an approximation, suitable for stress and strain estimation where plasticity is limited, e.g. at notches. 对于没有很好定义缺口的地方，可能存在应变估算不足的情况At locations where there is no well defined notch, it may underestimate the strains. Seeger-Beste 和 Mertens-Dittmann 方法使用形状系数或塑性应变集中系数的方法来修正重新分布的总体应力The Seeger-Beste and Mertens-Dittmann methods use a shape factor or plastic strain concentration factor to modify the amount of the estimated stress redistribution Seeger-Beste Method 形状系数（塑性应变集中系数）Shape Factors (Plastic Strain Concentration Factors) Bar with Mild Notch in Torsion 在产品设计开发过程中，疲劳分析日益重要Fatigue analysis is an increasingly important part of the design and development process 许多部件都处于多轴应力状态，其中一些并在临界状态情况下处于多轴应力状态Many components have multiaxial loads, and some of those have multiaxial loading in critical locations 单轴分析方法给出的结论较差，需较大的安全系数做保证Uniaxial methods may give poor answers needing bigger safety factors 疲劳分析需要由测试和有限元的计算结果相结合Fatigue tools need to work from measured and FE-derived strains The Life Prediction Process e - N Approach 3-D Stresses Tensor Representation of Stress State Stresses can be represented as tensor Diagonal terms are direct stresses Other terms are shear stresses For equilibrium purposes it must be symmetric On free surface (z is surface normal) all terms with “z” in disappear. Can be written sij Strain Tensor Strains are also represented by tensors Diagonal terms are the direct strains and the other terms are shear strains For equilibrium the matrix is symmetric Shear strains, e.g. exy are half the engineering shear strain gxy Can be written eij Transformation of Co-ordinates Stress Tensor Rotation Stress or strain tensors can be rotated to a different coordinate system by a transformation matrix. The matrix contains the direction cosines of the new co-ordinate axes in the old system The tenso