Researches on the enhancement of fracture toughness induced by friction between crack faces

Mechanical model is established for the mixed-mode crackin elastic-viscoplastic material with friction present between the crackfaces. Asymptotic and numeric solutions to the crack-tip fields are got andthe frictional effects are discussed with the crack loaded under compressionand shear. Calculations and analyses are made to determine the boundary ofthe crack-tip plastic region and to obtain the plastic deformation energy init. It is indicated that the crack-tip plastic region will be enlarged andthe plastic deformation energy in the crack-tip region will be enhanced whenthe crack faces are frictionally contacted. From the viewpoint of energy,the plastic deformation energy can be viewed as the fracture toughness ofthe material in the crack-tip region. Therefore, the fracture toughness ofthe material in the crack-tip region can be enhanced by the friction betweenthe crack faces. Further analysis indicates that the enhancement of thefracture toughness is mainly due to the increment of the plastic deformationenergy in the crack-tip region other than the frictional heat produced onthe crack faces. It is indicated by the calculation and analysis of thephase-angle of the crack-tip load that probable hysteresis of the crackgrowth can occur due to the friction between the crack faces. Inengineering, friction between the crack faces can be produced artificiallythrough design and manufacture to improve the carrying capacity and prolongthe service life of the cracked components loaded under compression andshear.