Search

This paper investigates the failure mechanism of the rear drive shaft in a modified pickup truck which had operated for about 3000 km. The investigation included macroscopic and microscopic evaluation to document the morphologies of the fracture surface, measurement of the material composition, metallographic preparation and examination, mechanical testing, and finite element modelling and calculations. The results obtained suggest that rotation-bending fatigue was the primary cause of the drive shaft failure. The crack initiation is located in the root of the machined threads on the drive shaft surface and expanded along the side of the machining line surface. The main cause of fatigue cracks is attributable to a high stress concentration owing to a large unilateral bending impact under overload. Meanwhile, the bidirectional torsional force also produces a higher stress concentration and thus accelerates the fatigue crack to expand radially along the surface. Furthermore, the hardness of the central section of the drive shaft was marginally below standard. This deficiency results in harm to the bearings and other mechanical components, as well as expediting the enlargement of cracks. Finite element analysis revealed significant contact stress between the bearing and drive shaft, with stress levels exceeding the fatigue limit stress of the parent material. This highlights the need for reevaluation of the heat treatment process and vehicle loading quality to enhance the drive shaft's longevity. [ABSTRACT FROM AUTHOR]

To lay a foundation for alleviating the influence of mining shaft deformation (MSD) on the guide rail (GR) and monitoring the shaft deformation state, this paper studies the deformation law and mechanism of the guide rail under the MSD. Firstly, a spring is used to simplify the interaction between the shaft lining and surrounding rock soil mass (SRSM) under MSD, and its stiffness coefficient is deduced by the elastic subgrade reaction method. Secondly, a simplified finite element model is established based on spring element, the stiffness coefficient is calculated by the derivation formula, and its effectiveness is verified. Finally, the deformation law and mechanism of GR are analyzed under different types and degrees of MSD, and the deformation characteristics are studied under the disconnection between the shaft, bunton and guide rail. The results show that the established finite element model can better simulate the interaction between the shaft lining and SRSM, and the calculation efficiency is greatly improved. The guide rail deformation (GRD) has a strong ability to characterize MSD and owns the distinctive feature corresponding to different types and degrees of MSD and the connection state. This research can provide reference and guidance for the shaft deformation monitoring and the maintenance and installation of the GR, and also lays a groundwork for studying operation characteristic of hoisting conveyance under MSD. [ABSTRACT FROM AUTHOR]

• The calculation equation with correction efficient and particle swarm optimization can improve the inversion accuracy of compressive modulus of the bottom aquifer. • The variation law of the elastoplastic interface of the vertical additional force with the bottom aquifer waterhead is deduced. • The interaction between the shaft and guide rail changes with the guide rail position due to the vertical additional force acting on the shaft. • The guide rail deformation can reflect the deformation trend of the shaft and the connection state between them under non-mining action. To lay the foundation for monitoring the mine vertical shaft deformation and mitigating its influence on the guide rail, this paper studies the deformation law of the guide rail and its interaction mechanism with the shaft under non-mining action. Firstly, the correction coefficient is introduced into the settlement equation, and its compression modulus is inverted by the particle swarm optimization (PSO). Secondly, the relationship between the elastoplastic interface of the vertical additional force (VAF) and the bottom aquifer (BA) water head is deduced, and then its distribution law varied with water head is obtained. Finally, a finite element model using spring elements to simplify the interaction between the shaft and surrounding rock-soil body is established to analyze the shaft deformation law, its interaction mechanism with the guide rail, and the guide rail deformation rule in different connection states. It can be obtained from the analysis results that using the improved settlement equation as the PSO objective function weakens the influence of compressive modulus with the change of soil settlement, and enhances the calculation precision on the BA settlement, so that the deduced relationship between the bottom aquifer water head and the elastoplastic interface of the VAF is consistent with the actual soil settlement and deformation laws. The spring element can effectively simulate the interaction between the shaft and rock-soil body, which makes the action mechanism between them to consistent with the actual situation. Owing to the vertical compression deformation of the shaft, the force direction on the guide rail subjected to the shaft varies with the position, which bears the vertical upward force in the upper section, the vertical downward force in the middle section and the vertical upward force in the lower section. There are obvious differences in the deformation laws of the guide rail corresponding to different connection states, disconnected positions and non-mining shaft deformation, which exist a certain regularity corresponding their respective states. The guide rail mainly produces the fluctuating deformation along the bunton direction, and its amplitude and range increase with the non-mining shaft deformation. All in all, the guide rail deformation can reflect the state of itself, the shaft and the connection between them, which can provide reference and guidance for the monitoring of the shaft deformation and the safety of the mine hoisting system. [ABSTRACT FROM AUTHOR]