Abstract
Impact-based Mechanical Surface Treatments such as shot peening are widely used in aerospace, nuclear and other industries to improve the mechanical resistance of components. Measuring the stress–strain curve of materials under high-strain rate using repeated impacts is a key issue to improve such processes. This study presents an extension of a method developed by Kermouche (2013) for identifying the material stress–strain curve. It combines numerical and experimental approach using micro-impact testing. The main originality of the present work is the use of the impact load values instead of the depth of the residual imprint as an input parameter of the inverse identification. The reliability of the proposed method is then checked from a set of numerical blind tests. A direct method derived from Tabor’s pioneering work (Tabor, 2000) is also proposed to convert the impact measurements into an approximate stress–strain curve. These two methods have been applied on a commercially pure copper and show very good agreement. The main advantage of this analysis is to determine the mechanical behaviour of metallic surface at high strain rate using limited numbers of samples and tests.
Highlights
Shot peening is a surface treatment process used in many industrial branches to improve the mechanical properties of materials by producing a compressive residual stress from the projection of spherical balls at high speed
The determination of the stress– strain curve at high strain rate is of main interest for prediction of strain and residual stress fields
Using the results of radius and load obtained after a micro-impact test at given energy, an inverse identification method has been developed
Summary
Shot peening is a surface treatment process used in many industrial branches to improve the mechanical properties of materials by producing a compressive residual stress from the projection of spherical balls at high speed (between 100–500 mm.sÀ1). The ball impacts result in large plastic deformations on the treated area that induce surface hardening and beneficial compressive residual stress (Abramov et al, 1998). To further develop this process or apply it to new alloys, a better knowledge of the behaviour of materials under similar process conditions is required. Some works (Beghini et al, 2006; Collin et al, 2009, 2008) deal with the use of instrumented indentation tests under single or repeated load cycles for determining the stress–strain curve of material. It’s proved to be costly and challenging especially when the penetration depth is required, which limits their practical use
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