WP 4

Objectives

  1. Creation of a verified numerical model of the new orbital friction welding process and the aluminothermic welding process, including models of energy input and equipment set-up.
  2. Numerical simulation of the thermal, stress and strain fields present during orbital friction welding and aluminothermic welding, through finite-element calculations, with particular emphasis on cooling after welding and residual stresses and deformations, microstructure and hardness.
  3. To provide a tool for optimisation of joint properties and weld quality for both welding processes.
  4. To provide a useful tool for predicting the process parameters for welding rails made of different materials and with different dimensions.

Achievements

For Orbital Friction Welding

A validated model for heat generation in rail steel during friction welding that gives heat generation and friction coefficient during heating phase of friction welding, validated against experiments. 

 A tool to find optimal process parameters for weld quality with calculated cooling times and deformations after orbital friction welding, giving microstructure and extent of heat affected zone and shrinkage. 

 Aluminothermic welding

Validated numerical model that calculates temperatures and stresses during all phases of aluminothermic welding such as preheating, tapping, forging, cooling, water spraying. 

 Calculated temperatures, deformations and stresses during full process gives cooling times (microstructure), deformations (risk for hot cracks) and residual stresses (risk for cracks initiating from rail weld when in operation)