Finite Element Simulation of Waterjet-Peened Al 7075-T6 Aluminum Alloy Surface by Using Multiple Droplet Impacts
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JMEPEG https://doi.org/10.1007/s11665-020-05208-8
Finite Element Simulation of Waterjet-Peened Al 7075-T6 Aluminum Alloy Surface by Using Multiple Droplet Impacts Rihem Amri, Adnen Laamouri, and Raouf Fathallah (Submitted July 17, 2020; in revised form September 4, 2020; Accepted September 19, 2020) This paper presents simulation of waterjet peening process based on finite element (FE) modeling with adjacent water droplet sets, which impact the material at high velocities. This simulation allows predicting the peened surface integrity including residual stresses, plastic strains, surface roughness and superficial damage. The proposed modeling considers both a mono-set and multi-sets of water droplets presenting an exponential distribution of an impact velocity, which depends on the principal parameters of the waterjet peening process. The Johnson–Cook material behavior law is adapted in this modeling. The validity of this simulation is studied for a waterjet-peened Al 7075-T6 aluminum alloy. The FE modeling is discussed with the effects of several factors and configurations (droplet diameter, repeated impacts, additional covering and multi-sets impact), and the numerical results are compared to the experimental ones. It is found that the low droplet diameter dw = 0.3 mm permits to have a lower surface integrity than that with diameter dw = 0.5 mm, which is clearly better. The effects of repeated impacts and additional covering induce an increase in the surface integrity. The FE modeling, using the impacts of multi-sets, allows having a good agreement with the experimental results. Keywords
droplet impact modeling, FE simulation, high impact velocities, surface integrity, surface work hardening, waterjet peening
1. Introduction Waterjet peening (WJP) is an emerging surface treatment (Ref 1-7) used to enhance the fatigue performance and stress corrosion resistance of many metal components (Ref 8, 9). It has been applied in various mechanical fields, such as the aerospace and automotive industries, welded structures in power plants and industrial machines (Ref 10) and for metal orthopedic implants in the medical field (Ref 11). This process consists in a continuously high-velocity water droplet impingement over the component treated surface. It leads to have a high load peak, inducing incompatible localized plastic strains in the outer layers of the treated part and leading to an in-depth compressive residual stress profile (Fig. 1) (Ref 9, 10). WJP is characterized, as compared to the conventional shot peening surface treatment, by better surface finishing and increased coverage. However, a low compressive residual stress depth and magnitude and a localized erosion of the component surface are potential disadvantages related to WJP. Its principle parameters are: (1) the nozzle diameter (dn), (2) the supply Rihem Amri and Raouf Fathallah, Unit of Mechanical Engineering and Materials Production (UGPMM), National Engineering School of Sousse (ENISo), University of Sousse, Sousse, Tunisia; and Adnen Laamouri, Laboratory of M
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