Effects of soft hemispherical particle on local surface stress of hard matrix

Finite element analysis was performed to investigate the stresses within and around a soft hemispherical particle located on the surface of a hard matrix under a remote external tensile load. The purpose was to understand the effects of neodymium rich particles on the fatigue properties of Ti-55 alloy. Three case studies were considered. First both particle and matrix were perfect, second a crack existed within the particle, and third a crack was located in the matrix adjacent to the particle. Numerical results show that soft particles cause stress concentration in regions of the matrix adjacent to the particle, but that such stress concentrations are much weaker than those associated with a cavity. A crack within the particle increases the stress concentration in the matrix only a little when the crack is far from the interface. However, a crack in the matrix significantly increases local stress in the particle.