Stress Intensity Factor for Cracks Emanating from a Shaft

Shaft is a rotational body used to transmit power or motion. Due to cyclic loading conditions, surface cracks frequently grow in the shaft. Normally these cracks will propagate with a semi-circular shape and cause premature failure to the whole system. In order to prevent the catastrophic incident, there must be a monitoring system that provides an early warning during the operation of the shafts. The semi-analytical or experimental method applied previously had its own limitations and disadvantages. Hence, there is a great need to determine the stress intensity factor in cracked shafts by using finite element method. The objective of this study is to determine the stress intensity factor (SIF) for cracks emanating from a shaft by using finite element method and also to verify the finite element results with those obtained semi-analytically. The scope of this study is focused on the semi-circular crack and the crack loadings considered are Mode I and Mode III. This study is divided into two phases. For the first phase, modelling of the cracked shaft was carried out in ANSYS software, while for the second phase; the results obtained from the finite element analysis were compared with those obtained semi-analytically. The relationship between dimensionless SIF and the normalized relative crack depth is presented in the results and discussion section. The results obtained numerically and semi-analytically had been compared and the deviation in term of percentage is relatively small. In conclusion, the SIF of a shaft determined by the numerical method was verified to be accurate.