Fracture Strength of WC-12Co Thermal Sprayed Coating under Mixed Loading Mode Ⅰ & Ⅲ in Crack Surface Displacement

摘要

Fracture strength of WC-12Co thermal sprayed coating is investigated experimentally and analytically. In the experiments, one pair of butt cylindrical specimen with coating is subjected to combined tension with torsion stresses. Fracture loci were obtained for three kinds of thickness of the coating in σ- τstress plane. Stress distributions at crack tip singular point on fractured surfaces are analyzed by Finite-Element-Method and approximated by the expression σ = KR~(-λ) where R means normalized thickness coordinate. It is found that the normal stress distributions are common to all cases of testing stress conditions and so fracture condition of the brittle coating is represented as K≧Kcr in the normal stress distribution even under mixed deformation mode Ⅰ and Ⅲ. A critical shear stress distribution for separation could also be obtained.