Experimental and Simulative Failure Analysis of AISI 316L Stainless Steel Screw Shaft

This paper presents a study on failure analysis of a screw shaft in a pure terephthalic acid screw conveyor after about 6-year operation. A series of characterization analysis were performed by careful visual observation, mechanical properties tests, chemical content examination, microstructural analysis and microchemical analysis of nonmetallic inclusions. Furthermore, the outer surface topography of the shaft at the fracture position was measured by three-dimensional scanning method. Finite element method considering surface topography was also employed to define the evolution of critical region. Results reveal that the serious stress concentration resulted from structure discontinuity including small radius at the transition and surface roughness was the main reason leading to the crack initiated and propagated, and the latter one was proved to be the biggest driving. To prevent the failure, better controls of surface state and structure size were strongly recommended.