Predicting the fatigue strength and life of 316L steel sinters of varying porosity for implants in a uniaxial loading state

• Published in: Engineering fracture mechanics Vol. 200; pp. 146 - 165
• Main Authors: Falkowska, A., Seweryn, A., Szusta, J.
• Format: Journal Article
• Language: English
• Published: New York Elsevier Ltd 01.09.2018; Elsevier BV
• Subjects: 316L stainless steel; Austenitic stainless steels; Crack propagation; Damage accumulation; Fatigue failure; Fatigue life; Fatigue strength; Fatigue tests; Implants; Life prediction; Load history; Materials fatigue; Mathematical models; Numerical prediction; Plastic deformation; Porosity; Porous materials; Porous sinters; Powder metallurgy; Sinter; Sintering (powder metallurgy); State variable; Steel; Tensile strength; Tensile stress; Porous sinters; Fatigue life; 316L stainless steel; Damage accumulation; Fatigue strength; Implants
• ISSN: 0013-7944; 1873-7315
• DOI: 10.1016/j.engfracmech.2018.07.030

•The strength and fatigue life of porous sintered material were tested.•Mechanisms of damage to the porous material have been identified.•The model of fatigue damage accumulation is presented. This paper presents a new approach to predicting the fatigue strength and life of 316L steel sinters of varying porosity used in the production of implants. Uniaxial monotonic and periodically variable loads were taken into account. The research material consisted of sinters of 316L austenitic steel, with porosities p = 26%, p = 33% and p = 41%, obtained by powder metallurgy. Determined monotonic and fatigue curves within the range of uniaxial tension-compression made it possible to identify the process of fatigue damage growth and formulate numerical dependencies for predicting the fatigue life of porous materials. The variables of the porous sinter’s damage state were defined, and the law of damage accumulation (linear and non-linear approach) was formulated incrementally, so as to enable analysis of the influence of loading history on the material's fatigue life. In the proposed model, the increment of the damage state variable was made dependent on the increment of plastic strain and of the tensile stress value in the sample, and in the non-linear approach, also on the actual value of the damage state variable. The numerical model of fatigue damage accumulation was experimentally verified through tests performed by the authors on samples of porous sintered material with varying degrees of compaction.