Fatigue failure prediction through factor of safety and stress concentration in a malfunctioned AISI 4140 automotive crankshaft

Abstract

The performance and safety of any vehicle relies on proper design of crankshaft. Crankshaft failure occurs mainly due to the combination of imbalance and minor deflections when the materials is subjected to combined bending and twisting. Failure analysis is crucial to identify the causes and modes of failure, in order to improve the service life of automotive crankshafts and prevent accidents. This research analyses the root cause of failure by testing a failed crankshaft of a twin cylinder diesel engine used in mini commercial vehicle runs around 80000 km. The important research gap identified as that there is no fool-proof techniques and validation procedures are followed in the service stations during its life cycle period. This investigation of a failed crankshaft provides detailed composition of material, its micro structure and mechanical properties. Further, rotary analysis, experimental modal analysis and mechanical testing of materials are helpful in characterizing proper materials to be selected and analyzing the root cause of failure. The experimental setup helps to test a crankshaft and its specimen as per ASTM testing procedures and the results are correlated with numerical analysis using ANSYS software. The objective of this investigation is to provide insights through failure analysis to the designers and manufacturers, thereby improve the reliability and safety of automotive crankshafts, ensure safe operation of the vehicle, and eventually minimize financial losses.