Shot peening of case hardened gear steel
Experiments and computations
Time: Fri 2024-11-22 10.00
Location: D37, Lindstedtsvägen 5, Stockholm
Video link: https://kth-se.zoom.us/j/62697210590
Subject area: Solid Mechanics
Doctoral student: Erland Nordin , Solidmekanik och strukturer
Opponent: Professor Jens Hardell, Luleå tekniska universitet, Institutionen för teknikvetenskap och matematik
Supervisor: Professor Mårten Olsson, Solidmekanik och strukturer
QC 241112
Abstract
Shot peening is a process where small balls are shot at (impacting on)a target, e.g. gear teeth, so that indents are formed on the targetsurface. On gears the purpose of the peening is to increase the fatiguestrength. The indents are formed because the surface is plasticallydeformed which in turn cause three main property changes; residualcompressive stresses are created close below the surface,microstructural changes to the steel material and surface topographychanges.The shot peening process in itself is controlled with parameters suchas: Intensity, Coverage, Media hardness and shape. Simulating shotpeening requires information about the impact velocity. A method todetermine the velocity during the shot peening is presented. A materialmodel that includes plastic deformation and retained austenitetransformation is developed and can predict the experimental resultswith adequate accuracy for the basic model. Parameter variations showthat increased accuracy can be obtained by including a distribution inmedia shape. This would, however, increase the complexity andsimulation time considerably. Using spherical media was judged to bea good compromise. Residual compressive stresses and work hardeningare predicted well. Surface roughness predictions on ground partswould need to include the ground surface on the simulation target.