Investigation on fatigue life of Rail-Wheel assembly using Finite Element Analysis
In recent years, the axle loads on railway cars is increasing due to increased transport of the goods and faster infrastructural growth. The rail wheels are subjected to high contact stresses of alternating magnitude due to rolling action of the wheels under these loads. The rail wheels should be able to sustain these variable loading for reasonably infinite life. Accidents due to fracture of rail wheels affects the safety of railway facility. Therefore more attention is paid to the quality of rail-wheel. The rail wheels are found to fail predominantly due to fatigue under these variable loadings whereas other modes of failure are damage to railway bogie, suspension failure and in some cases derailment of the vehicle. After all the advancements in design, materials and non-destructive inspection, the fatigue propagation and failure due to damage of railway components remains an important issue for safety engineering in railways. In this work, an attempt is made to investigate the occurrence of stresses in rail-wheel assembly due to high contact loads at the assembly points. The study involves the determination of equivalent stress (von-Mises), strain, safety factor using finite element method on ANSYS® 2016. An appropriate understanding of these mechanisms needs in depth knowledge of physical interactions between rail and wheel. The rail wheel assembly is assumed to operate under the designed load. The Goodman mean stress correction theory is used to obtain results. The results on the fatigue life are presented which are assumed to depend on these factors.
Analysis of subsurface crack propagation under rolling contact loading in railroad wheels using FEM
A general subsurface crack propagation analysis methodology for the wheel/rail rolling contact fatigue problem is developed in this paper. A three-dimensional elasto-plastic finite element model is used to calculate stress intensity factors in wheels, in which a sub-modeling technique is used to achieve both computational efficiency and accuracy. Then the fatigue damage in the wheel is calculated using a previously developed mixed-mode fatigue crack propagation model. The advantages of the proposed methodology are that it can accurately represent the contact stress of complex mechanical components and can consider the effect of loading non-proportionality. The effects of wheel diameter, vertical loading amplitude, initial crack size, location and orientation on stress intensity factor range are investigated using the proposed model. The prediction results of the proposed methodology are compared with in-field observations.
Mechanics of deformable directed surfaces
Abstract The paper develops a simple, yet complete and consistent non-linear dynamic thermo-elastic shell theory based on the concepts of a two-dimensional directed continuum. The constitutive equations are postulated in a general form. Stress-strain relations are derived using the equation of energy balance and the two entropy production inequalities, which are rewritten in a special form. The linear theory is discussed in detail. The structure of the stress-strain relations is presented in the most general form and then specialized to concrete examples, in particular, to the classical shell theory, using their invariance properties with respective to certain symmetry groups. The elastic moduli are determined by demanding the coincidence of the frequency dispersion surfaces obtained using the two-dimensional theory with the lowest foils of the corresponding surfaces resulting from the three-dimensional theory of elasticity.