Visual Inspection and Hardness Test of Fatigue Damage in Shaft Latching of Slab Tong
Abstract
Visual inspection and hardness tests were conducted to investigate the fatigue failure of the shaft latching component on a slab tong used in a truck-mounted crane system. After nearly nine years of repetitive operation under dynamic loading, the shaft latching fractured during use. The fracture surface displayed typical signs of fatigue failure, such as smooth, shiny areas and semi-circular patterns, indicating progressive crack propagation over time. To complement the visual findings, a hardness test was performed using an Equotip 2 device. The purpose of this research is to know the type of damage that occurs in shaft latching. The result showed a surface hardness of 41 HRC, significantly below the recommended 60 HRC for components subjected to cyclic loads. Based on visual evidence and comparison with theoretical references, the failure was classified as unidirectional bending fatigue. The shaft material, AISI 4140 alloy steel, may have experienced decreased fatigue resistance due to insufficient hardness and prolonged exposure to cyclic stress. The fracture occurred at a high-stress bending region, and the absence of plastic deformation suggested a sudden break following gradual crack growth.
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