Fracture and fatigue analysis of an agitator shaft with a circumferential notch

In this study, the failure (fracture) of an agitator shaft with a circumferential notch was selected as investigation topic. However, this study is intended for introducing fracture mechanics from an application viewpoint. It essentially focuses on both stress and fatigue analyses. Many mechanical systems subject to loading require modeling before their analyses can be executed. The important thing at this point is to be able to create an appropriate model; in addition consistent assumptions should be made. In this connection, several computer programs introduced provide much benefit to model the systems. In this study, Ansys 5.4 FEM program, to analyze the stresses at the notch tip, and TKSolver program, to perform calculations and to plot S-N diagrams for fatigue analysis were used. In general, the study gives an engineering perspective on how a real event can be analyzed by evaluating findings and data taken from the equipment. Before stress analysis, brief information on the agitator is given. In addition, the shaft material is introduced and how an fee (face-centered cubic) crystal fracture is explained. With the macroscopic examination of the fracture surface, the signs left by crack propagation are dealt in detail to interpret how the shaft is leaded to fracture. In the proceeding chapters, by setting up an agitator model, data taken from the agitator during operation and specification sheets are processed to make more realistic approximations for bending and tork forces, since they will be base for stress analysis, in which K\ is evaluated. For stress analysis, ten crack models with various crack lengths are created by using Ansys 5.4 FEM program. Again, mathematical procedure to show how to do fatigue analysis and related S-N diagrams drawn by using TKSolver program are presented.