Abstract：The moving least square meshless method and the couple stress theory were combined together. Discrete model of moving least square meshless method was derived based on couple stress theory. First，stress concentration of the circular hole was studied under couple stress theory. The basic parameters of the method were determined；and the key technology of the algorithm application was also solved. On this basis，as for the plane stress problems，stress intensity factor and normal stress near crack tip of the central crack-I，stress intensity factor and the maximum shear stress of single and two boundary crack-I，and initial rupture of oblique central crack were studied with different characteristic lengths. Meanwhile，influence of shear force and fracture pressure on scale effect were presented. The results show that the couple stress has a significant influence on shear stress at crack-I tip，little influence on normal stress at crack-I tip. The couple stress has a significant influence on oblique crack bending propagation for plane stress problem. For oblique crack，the crack propagation angles，steps and loads show remarkable scale effect. The horizontal shear may intensify the scale effect. The fracture pressure has little influence on scale effect.
FLECK N A，HUCHINSON J W. A phenomenological theory for strain gradient effects in plasticity[J]. Journal of the Mechanics and Physics of Solids，1993，41(12)：1 825-1 857.
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2011, Vol. 30 
