Material Fatigue as a Cause of Construction Drilling Rig Failure

Abstract. This study aims to analyze the failure of the BG 1080MGF construction drilling rig, which occurred due to the shearing of the bolt securing the drill bit to the motor shaft. Typical causes of wear in construction machinery components are discussed first, including abrasion, corrosion, material fatigue, overheating, operational errors, and material defects. Particular attention is paid to the phenomenon of material fatigue, which plays a key role in the development of cracks and the weakening of structural components. The analyzed mounting bolt, 20 mm in diameter and with a strength class of 10.9, failed due to the action of variable shear stresses and the presence of a notch in the transition zone between the threaded and smooth parts. Observations of the fracture confirmed the fatigue nature of the failure. Although the bolt used met the strength requirements, the impact of cyclic loading led to the formation of a fatigue gap, resulting in the shearing of the component and the slippage of the drill bit from the drill shaft. The necessity of properly selecting mounting bolts and considering the impact of material fatigue in the design and operation of construction machinery is emphasized.