Stress Intensity Factor for a Crack Emanating From a Shaft

Shaft is a rotational body used to transmit power or motion. Due to cyclic loading conditions, i.e. axial, bending and torsional load, surface cracks frequently grow in the shaft. Normally these cracks will propagate with a semi-circular shape and cause damage or premature failure to the whole system. These premature failures require expensive repair or replacement cost, and sometimes even worst the operators get severe injury when the shaft failed during it services. The objective of this project is to determine the stress intensity factor (SIF) for a crack 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 on the shaft and the calculation of SIF for Mode I (Opening) and Mode III (Tearing/Torsion) crack loading. The study is divided into two phases. For the first phase, modelling of the cracked shaft is carried out in the ANSYS software, while for the second phase; verification is carried out between the finite element results and those obtained semi-analytically. In the results and discussion section, the relationship between the dimensionless stress intensity factor and the normalized relative crack depth is presented. The results obtained semi-analytically and numerically had been verified and the deviation in term of percentage is relatively small. In conclusion, the stress intensity factor of a shaft determined by the numerical method was verified to be accurate.