广义平均形状改变能密度断裂准则及应用

基于形状改变能为材料起裂扩展控制参量的物理事实及裂纹尖端断裂控制区能量平均概念，提出了计及裂纹尖端应力场特征级数展开奇异项和常数项的广义平均形状改变能密度(GADSED)准则，建立了I-II-III 混合型裂纹断裂判据计算式，为工程结构疲劳断裂评估提供了新选择．基于提出的GADSED 准则，系统分析了T应力对裂纹断裂判据的影响，结果表明：当参数|Ba|数值相同时：负值T应力的I-II 混合型裂纹更易起裂扩展，正值T应力的KΙf值高于负值T应力的KΙf值，正负T应力的KIIf值相同；T应力在区间0 < Bα < 0.45 时增大了KΙf值（3 %以内），T应力降低了KIIf值．根据GADSED 准则完成了双轴疲劳载荷平板表面I 型裂纹扩展寿命预报，结果表明：基于GADSED 准则的裂纹扩展寿命预报值约为传统方法预报值的40.7 %，可为工程实际评估提供借鉴．

Generalized Averaged Deviator Strain Energy Density Criterion and Its Application

A new energy-based mixed mode criterion called generalized averaged deviator strain energy density (GADSED) criterion considering both the singularity terms and the constant term T-stress is proposed in this paper based on the deviator strain energy and averaged energy concept. The fracture onset criterion of the I-II-III mixed mode crack was then given. The effect of T-stress on the fracture behavior of the mode I, mode II and mixed mode I-II crack was investigated thoroughly based on GADSED criterion. The results show that fracture is more likely to happen when the T-stress is negative at a given parameter |Ba| for the mixed mode I-II crack, and T-stress has a positive effect on KΙf when 0 < Bα < 0.45 for mode I crack while it reduces the KIΙf for mode II crack. The crack growth life of the plate surface mode I crack under the biaxial load was predicted based on the traditional criterion ΔKΙ and the proposed GADSED criterion. The results show that the crack growth life predicted by GADSED criterion is about 40.7 % of that predicted by traditional method, providing reference for practical engineering evaluation.