On the Modelling of Impulsive Pressures and Residual Stresses Induced by Cavitation Peening
Author: Emmanuel Sonde, Thibaut Chaise, Daniel Nelias, Cyril Mauger, Nicolas Boisson
Source: ICSP-13
Doc ID: 2017131
Year of Publication: 2017
Abstract:
Introduction:
Residual stresses are those remaining in mechanical parts free of any external loading. They generally
come from thermal effects, mechanical loading and/or metallurgical phase transformation during the
manufacturing steps. When these stresses are of tensile type, they can have negative consequences
on the lifetime of the component by helping cracks initiation and propagation phenomena like Stress
Corrosion Cracking (SCC). In order to improve the fatigue life and avoid the premature failure of
metallic components, surface treatment processes are carried out to introduce residual stresses of
compression in materials and to raise the critical value of operating tensile stress. Conventional Shot
Peening (SP), Ultrasonic Shot Peening (USP) and Laser Shock Peening (LSP) are some of these surface
treatment methods which have been widely studied both experimentally and numerically.
Water Cavitation Peening (WCP) is a similar process of surface treatment [1]. During WCP, cavitation
bubbles are created by a high-speed submerged water jet directed toward the workpiece surface. The
cavitation phenomenon occurs in low static pressure (lower than vapour pressure of water) zones
due to the turbulence generated, at a given temperature. The collapse and/or the impact of these
bubbles on the treated surface induce high loading pressures and thereby plastic deformation of the
superficial layers of the material. Superficial compressive residual stresses are then introduced in the
material. This process is known to provide a better surface finish with less roughness than that of the
conventional shot peening because there is no solid – solid contact involved [2].
Many experimental studies have proven the efficiency of the present process to introduce
compressive residual stresses into relatively high yield strength materials and enhance their fatigue
strength [3]. However, the modelling of cavitation peening is very challenging, because of the complex
behaviour of cavitation phenomenon. Very few studies concerning the modelling and simulation of
WCP have been reported. A mechanical model based on finite element method have been proposed
by Han and Hu [4] to predict the residual stress profile obtained after WCP. The authors measured
experimentally the affected surface diameter. Then, they supposed a constant spatial distribution and
trapezoidal temporal variation, for the loading pressure. As the above-mentioned study, most of the
numerical studies about the modelling of cavitation peening employed theoretical values for pressure
magnitude and pressure pulse duration with no direct link to the process parameters. The main
reason and issue is the difficulty to determine the impulsive pressure distribution of cavitation
peening.
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