Session: 02-09-03: Computational Modeling and Simulation for Advanced Manufacturing-III

Paper Number: 72272

Start Time: Tuesday, 03:50 PM

72272 - Process Prediction for Repair of High-Speed Train Wheelseat Axle by Extreme High-Speed Laser Material Deposition (EHLA) 

The performance and dimension of high-speed train wheelseat axle reduce to a level that cannot meet the design requirement after a period of service due to the surface scratch, wear or cracks. Interference fit method increases the detriment to the wheelseat axle when the wheelset is frequently assembled and disassembled to check the service conditions. Reasonable and efficient maintenance of those worn and valuable parts yields both economical and ecological benefit. Extreme high-speed laser material deposition (German acronym: EHLA) is characterized by increased cooling rates, elevated process speeds of up to 200 m/min and a significantly reduced heat affected zone. In this study, we focus on the feasibility of using EHLA for the repair of high-speed train wheelseat axle. First, we selected commercial available AISI 4140 powder particles as additive materials according to the comparison of chemical composition and mechanical properties of substrate and powder materials. Second, we studied how the process parameters such as laser power, powder mass flow, volume of shielding gas, and the offset between two adjacent tracks influenced the deposited material. This phase was aimed at obtaining the process parameters for a single layer with metallurgic bonding between the substrate and the layer, low porosity, and without any cracks. Then the best parameters were applied for the building up of volumes. Reduced test pieces were extracted from the laser deposited volume. Hardness, temperature history, tensile strength, rotating bending fatigue limit and residual stress of the reduced test pieces were examined experimentally. Third, a coupled thermo-mechanical finite element model was applied to investigate the possibility to transfer the process parameters determined through reduced piece testing to the full-scaled wheelseat axle. Based on the knowledge that temperature history significantly affects the mechanical properties, this phase was carried out by comparing the temperature distributions for divergent diameters of substrate with same process parameters. User-defined subroutines were also used to continuously activate clad elements and surface thermal boundary conditions as a convenient method to define ‘steps’ for updating the FE geometry and simulating clad material deposition. The results indicated that hardness, tensile strength and rotating bending fatigue limit of reduced pieces were higher than the requirements in the standard, but the magnitude of residual stress was beyond the specified range. The cross-sectional geometry of the melting pool calculated by thermal model correlated with the experimental results well. The process parameters for the full-scaled high-speed train wheelseat axle should be optimized, and heat input needs decreasing for the same temperature distribution as reduced pieces.

Presenting Author: Tianci Li Beijing Jiaotong University

Authors:

Tianci Li Beijing Jiaotong University
Lele Zhang Beijing Jiaotong University
Geng Chen Beijing Jiaotong University
Thomas Schopphoven Fraunhofer Institute for Laser Technology ILT
Andres Gasser Fraunhofer Institute for Laser Technology ILT
Reinhart Poprawe Fraunhofer Institute for Laser Technology ILT