Effect of Fillet Radius at the Shank-to-Body Transition on the Local and Global Structural Responses of a Lifting Hook

Abstract

Geometric modifications of lifting hooks are generally evaluated based on changes in stress at the modified region; however, a reduction in local stress does not necessarily produce a corresponding change in the global response of the hook. This study evaluates the effect of fillet radius at the transition between the shank and hook body on the local and global structural responses. Four fillet radii, namely 5, 10, 15, and 20 mm, were analyzed using the finite element method in ANSYS Static Structural with AISI 1045 Hot Rolled steel under a static load of 49,050 N. The reliability of the model was evaluated through mesh convergence analysis and comparison with an analytical stress concentration factor approach. The results show that increasing the fillet radius from 5 to 15 mm reduced the local stress at the fillet by 15.59%, from 68.49 MPa to 57.81 MPa, whereas a further increase to 20 mm did not produce an additional reduction. In contrast, the maximum global stress occurring at the inner bowl surface changed by only 0.25%, from 138.15 to 138.49 MPa, resulting in a relatively constant factor of safety in the range of 2.383–2.389. The maximum deformation also changed by only 0.69% across the range of fillet radii. These results indicate that the fillet radius has a more pronounced effect on the local stress response than on the global structural response. Therefore, a reduction in stress at the fillet region alone is insufficient to demonstrate an improvement in the overall strength of the lifting hook, particularly when the modified region is not the location of maximum stress. Evaluation of geometric modifications in lifting hooks should therefore consider the location of critical regions and distinguish between local and global structural responses.