Researchers at the Department of Metallurgy and Materials Engineering (DMME) at the University of Malta are investigating the effect of shock waves generated at the surface of automotive Austempered Ductile Iron (ADI) gears. The 30-month project, called Laser Shock Peening for Automotive ADI gears or LaSPAAG, has a budget of €141,000 and is financed by the University of Malta through the Transdisciplinary Research and Knowledge Exchange Complex (TRAKE).
LaSPAAG is focusing on limiting wear and fatigue damage during the operation of gearboxes, which are key automotive transmission components. The surface of the materials in contact and in relative motion to each other is necessarily the first layer of defense against such damage. Laser shock peening (LSP) is a novel surface enhancement process being adopted in the aerospace and automotive industries, which could provide drastic improvements in this type of application. LSP applies a high-energy pulsed laser beam on the surface of metallic components with an exposure in the nanosecond range to generate shockwaves and induces impressive surface residual compressive stress (Figure 1). Furthermore, LSP allows for pinpoint accuracy, and thus the mechanical properties can be modified as and where required – retaining beneficial bulk characteristics where necessary.
Figure 1: Typical set-up for laser shock peening and a sketch of plasma shock wave confinement [1]*
The LaSPAAG team is currently in the process of investigating shock wave propagation and calculation of the residual stress fields by identifying the optimal laser shock process parameters and conditions through 3D Finite Element Modelling (FEM) analysis (Figure 2). In addition, preliminary experimental trials are being carried out and studied using advanced material characterisation techniques, such as SEM-EBSD (Scanning Electron Microscopy – Electron Backscatter Diffraction), XRD (X-ray Diffraction) and surface profilometry. This analysis will provide an insight into the process dynamics and extent of material change.
This project is being led by Dr Inġ. Ann Zammit, in collaboration with Prof. Inġ. Glenn Cassar and Dr Prabhakaran Subramaniyan (Department of Metallurgy and Materials Engineering, UM). Other partners working on the project are Prof. Inġ. Pierluigi Mollicone (Department of Mechanical Engineering, UM) and Dr Louis Zammit Mangion (Department of Physics, UM), Dr Pratik Shukla (), Dr Daniel Glaser (), and Prof. Remigiusz Michalczewski (, Poland).
Figure 2. LEFT: A 3D model applying laser shock pressure to the toothed crown of the gear; RIGHT: Interaction of toothed crowns
*[1] N. Shen, H. Ding, Experimetnal analysis of sheet metal micro-bending using a nanosecond-pulsed laser, The International Journal of Advanced Manufacturing Technology, 2013, 69, 319-327
