Effect of couple-stresses on the Mode I dynamic stress intensity factors for two equal collinear cracks in an infinite elastic medium during passage of time-harmonic stress waves

Dynamic stresses around two equal collinear cracks in an infinite elastic medium are evaluated based on linearized couple-stress theory while the medium is subjected to time-harmonic stress waves impinging normal to the cracks. The boundary conditions with respect to the cracks are reduced to dual integral equations using Fourier transformations. To solve these equations, the discontinuities in the displacement and in the rotation at the cracks are expanded in a series of functions that are zero-valued outside the cracks. The unknown coefficients in each series are solved using the Schmidt method to satisfy the boundary conditions along the crack faces. The stress intensity factors and the couple-stress intensity factors are determined, and they are calculated numerically for selected crack configurations.