A numerical analysis based on M-integral about the interaction of parallel surface cracks in an infinite plate

Abstract

Multiple cracks have been widely observed in pressure vessels and structure components. When multiple cracks approach each other, the interaction between them could affect the stress field around the cracks. So multiple cracks should be taken into account simultaneously because the interaction could change the stress intensity factor (SIF) of the cracks. In ASME Boiler and Pressure Vessel Code Section XI, a flaw combination criterion is provided for interacting parallel surface cracks. However, the criterion for the offset distance does not consider the influence of crack size on the magnitude of the interaction and is only given by an absolute value. In present paper, firstly, SIF for parallel surface cracks is evaluated as a function of the crack front position, relative position, aspect ratio and relative size by numerical analysis based on M-integral. And the influence of the interaction on SIF is quantified. It is shown that the crack front position, relative position between two cracks, aspect ratio and relative size are important parameters to determine the interaction between parallel surface cracks. Secondly, the new combination criteria for the offset distance are proposed for the fracture evaluation based on analysis results.