正交各向异性材料中微裂纹的最大屏蔽效应

Maximal Crack Tip Shielding by Microcracking in Orthotropic Elastic Solids

通过对正交各向异性材料中不同的微裂纹屏蔽源泉的分析，发现在Ｈｕｔｃｈｉｎｓｏｎ所指出的屏蔽效应的第２个源泉（即微裂纹形成引起的残余应力释放导致应力场的再分布）中，还应计及微裂纹形成引起的远场应力在微裂纹处产生的应力场的释放（可称为诱导应力），从而应重新考虑应力场的分布，在文中所研究的各向异性脆性材料中，在计及诱导应力释放对应力场的影响及局部材料刚度下降的影响时，当微裂纹倾角与微裂纹处的最大拉应力方向垂直时，微裂纹对主裂纹的屏蔽效应达到最大值，该结果与Ｏｒｔｉｚ在连续损伤力学的构架下得到的结果一致．

The shielding and anti shielding effect on the main macrocrack due to near tip microcracking in orthotropic elastic solids is evaluated by considering the release of residual stress and induced stress. It is concluded that the maximum shielding effect will be reached when the orientation of microcrack is normal to the direction of maximal tension stress at the point under investigation. This result is in agreement with the conclusion arrived by Ortiz for an isotropic brittle solid; there are no influences of distance L on the minimum anti shielding or maximum shielding effect within the fan of about -40° to 40° ahead of the tip of main macrocrack in the definite region of L . Beyond this region, the variation of distance (of microcrack center from main crack tip) L can affect the value of the shielding effect but have no influence on the microcrack oriented angle φ where the maximum shielding arrived.