Abstract: The nominal strength of open hole specimens has a great intense in composite material industry. The physical cohesive laws between the crack opening displacement and the cohesive stress over length of fracture processing zone FPZ are used to imply the nominal strength. The result is a valuable graph that relates the nominal strength with respect to the crack size and FPZ length ℓ. The nominal strength of quasi-brittle structures has been analyzed taking into account the geometry and size of the specimen and the shape of the cohesive law. Simple design tables for a constant and linear cohesive law have been developed. Furthermore, the procedure to compute the nominal strength with a general bilinear cohesive law is defined.

Abstract: The 316L stainless steel has been widely used in both artificial knee and hip joints in biomedical applications. The average lifetime of artificial hip joints is about 10 years due to aseptic loosening of the femoral stem attributed to polymeric wear debris; however, there is a steadily increasing demand from younger osteoarthritis patients aged between 15 and 40 years for a longer lasting joint of 25 years or more. This paper studies the properties changes of powder metallurgy 316L stainless steel, depending on the compacting pressure, sintering temperature, and the sintering atmosphere. All samples have been compacted at 150, 250, and 350 MPa, and sintered at 1200, 1250, and 1300 oC. In order to analyze the sintering atmosphere, three different media were used: nitrogen, pure argon, and vacuum. The properties of the materials are evaluated. The study covered sintering density, compressive strength, hardness, wear resistance and microstructure analysis. The results show that the porous 316L stainless steel can be used as hard tissue implant.