Researches on the enhancement of fracture toughness induced by friction between crack faces
裂纹面摩擦接触引起的断裂韧性增长的研究

Mechanical model is established for the mixed-mode crack in elastic-viscoplastic material with friction present between the crack faces. Asymptotic and numeric solutions to the crack-tip fields are got and the frictional effects are discussed with the crack loaded under compression and shear. Calculations and analyses are made to determine the boundary of the crack-tip plastic region and to obtain the plastic deformation energy in it. It is indicated that the crack-tip plastic region will be enlarged and the plastic deformation energy in the crack-tip region will be enhanced when the crack faces are frictionally contacted. From the viewpoint of energy, the plastic deformation energy can be viewed as the fracture toughness of the material in the crack-tip region. Therefore, the fracture toughness of the material in the crack-tip region can be enhanced by the friction between the crack faces. Further analysis indicates that the enhancement of the fracture toughness is mainly due to the increment of the plastic deformation energy in the crack-tip region other than the frictional heat produced on the crack faces. It is indicated by the calculation and analysis of the phase-angle of the crack-tip load that probable hysteresis of the crack growth can occur due to the friction between the crack faces. In engineering, friction between the crack faces can be produced artificially through design and manufacture to improve the carrying capacity and prolong the service life of the cracked components loaded under compression and shear.