Prediction of Geometric Distortion and Residual Stresses In Hot Rolled and Heat Treated Large Rings Through Finite Element Modeling
During quenching, hot rolled steel rings, especially those with a large outer diameter to wall thickness ratio, distort and develop undesired residual stresses. These phenomena are the result of three major mechanisms: metallurgical, mechanical and thermal. This paper presents the result of a comprehensive study on the heat treatment of rings by modeling via Finite Element Analysis. The simulation is carried out with coupled analysis of heat transfer, deformation mechanics and phase transformations. The material data required for the simulation of distortion during heat treatments, including TTT/CCT phase transformation diagrams, temperature dependent physical and thermophysical properties, as well as temperature and strain rate dependent mechanical properties are calculated by computer models.
Distortion Analysis of Rear Axle Shaft after Heat Treatment
: ear axle shaft is used to connect the differential system and rear wheel. During manufacturing the rear axle shaft is subjected to soft machining operation, heat treatment and finally hard machining in sequence. Rear axle shaft is subjected to induction hardening before hard machining operation. During this operation the shaft will get distorted. The aim is to reduce the distortion to minimum level during induction hardening operation. Induction hardening parameters were studied. A plan of experiments based on Taguchi technique was used to acquire the data in a controlled way. An orthogonal array and analysis of variance was employed to investigate the influence of induction hardening parameters like as power potential, scan time and quench flow rate on distortion of rear axle shaft. The objective was to investigate which induction hardening parameter significantly affects the distortion. ANOVA results showed that power potential is the parameter which influences the distortion of the shaft to the maximum extent. Thus by controlling this parameter the distortion of shaft can be minimized.
Transient nonlinear thermal stability analysis of metro cable under pulse power
The load of metro cable system varies a lot from morning rush hours to the evening closure time. With many trains hopping in the rush hours, the long term and economical short term thermal stability become a big issue as a result of the large difference between thermal time constant and the electrical time constant of cable. Based on a 10kV three-core XLPE metro power cable model, the theoretical thermal capacity was calculated according IEC standard. Then, a Finite Element Method (FEM) was employed to analyze the transient electro-thermal phenomena, taking into account various types of power loss in cable system and the non-linear electrical conductivity of the conductor. Finally, the thermal distribution inside the cable was presented as a function of time, and the maximum thermal capacity was predicted in metro cable.