Dynamic finite element modeling and fatigue damage analysis of thermite welds

Tsang

Fatigue Fract Eng Mat Struct

et al. 2020

Self Cite

The rail clip fastening system is an important structural component of railway track systems providing flexibility and turnover resistance for running rails. High replacement frequency of fasteners was observed compared with other components because of fatigue failures of rail clips. In this study, implicit and explicit finite element (FE) models were developed for E‐clip and Fast‐clip with material and fatigue properties obtained from experimental testing. The fatigue loading experiments were conducted to determine the strain‐life relationship. The assessments of the fatigue damage and fatigue life were analysed using the FE results for the rail clip strain/stress components with the Fatemi‐Socie multiaxial fatigue criterion. A time‐efficient smallest enclosing circle algorithm was developed to search the critical plane orientation and the maximum shear strain amplitude for fatigue analysis. This work provides a method for FE and experimental study of multiaxial fatigue analysis of rail clip failures subjected to dynamic loading.

Section: Wheel-induced Dynamic Loading Fe Modelmentioning

confidence: 99%

“…In this study, multiaxial fatigue analysis using a time-efficient smallest enclosing circle algorithm was implemented in the critical plane searching process to reduce the computational time. 15 The FE models' inputs and fatigue properties were determined through clip material tensile tests, hardness tests and fatigue tests.…”

Section: Introductionmentioning

confidence: 99%

Finite element and experimental study on multiaxial fatigue analysis of rail clip failures

Tsang

Fatigue Fract Eng Mat Struct

et al. 2020

Self Cite

“…2) Sometimes the high temperature of the process causes distortion and relatively large deformations at the welding joint [17][18][19].…”

Section: Introductionmentioning

confidence: 99%

Investigation of Rail Welded Joint Stresses, by using a Narrow Gap Welding Method, in Ballasted Railway Tracks

Galdiani,

Mosayebi,

Mohit

2024

ACTA POLYTECH HUNG

In the modern railway superstructure construction and maintenance, particularly where higher speeds are required, the rail sections may be welded together to form Continuous Welded Rail (CWR). There are various methods for welding the rails, such as thermite welding, flash-butt welding, gas-pressure welding, enclosed-arc welding, etc. Narrow Gap Welding is another way of welding the rail joints and because of the lower implementation costs, easier, quicker process and acceptable performance, it is usually used over other methods in maintenance operations. Since this method is newer than others, there is lack of knowledge concerning the standard process of narrow gap welding and the factors that affect the final quality. In the narrow gap welding, two different welding electrodes are used for the welding process. One electrode, with higher stiffness, is used for the rail head and the other electrode, with lower stiffness, is used for the rail web and foot. In this research, the relationship between these different welding electrodes and the amount of stress in rail joint was investigated via experiments and modeling, by a finite element method. The results indicate that the number of stresses, in the junction of rail head and web, was reduced by 37%, when the electrode with higher stiffness was used for the whole rail head, plus 1 cm of rail web. Field investigations demonstrated that the performance of rail welds was acceptable.

Simulation-based assessment of railhead repair welding process parameters

Andersson,

Steyn,

Ekh

et al. 2024

Weld World

This study uses a finite element method based simulation methodology for in-situ railhead repair welding to investigate how welding process parameters impact the repaired rail quality. The methodology includes material modeling with cyclic plasticity, phase transformations, transformation-induced plasticity, and multi-phase homogenization. The weld process modeling includes a 3D heat transfer analysis and a 2D Generalized Plane Strain (GPS) mechanical analysis. The Heat source model used in the thermal simulation is calibrated using measurements from a repair welding experiment. To assess the performance of the repaired rail, mechanical rolling contact simulations are performed to estimate the risk of fatigue crack initiation. The process parameter study is based on the Swedish stick-welding railhead repair procedure and focuses on factors affecting the repair quality, such as preheating and operation temperature conditions as well as variations in repair geometry. Significant findings highlight both the inherent robustness of the process and regions susceptible to parameter variations. Specifically, the powerful final zig-zag weld passes provide effective resilience against variations in additional heating, and the start and end stretches of the repair welding are the most susceptible to parameter variations. Chamfered and deeper cutout repair geometries are found to be effective in mitigating adverse effects. In agreement with field observations, the simulations identify the fusion zone of the base and weld filler material as the critical region of the repaired rail in operation. This is attributed to the integrated effects of unfavorable microstructures, longitudinal tensile residual stresses from repair welding, and tensile stresses during operational traffic loads.