Modification of Residual Stresses in Laser Additive Manufactured AlSi10Mg Specimens Using an Ultrasonic Peening Technique.

Xiaodong Xing,Haijun Gong,Fengchun Jiang,Xiaojing Sun,Xiaoming Duan,Liquan Wang

doi:10.3390/ma12030455

Abstract

Ultrasonic peening treatment (UPT) has been proved to be an effective way of improving residual stresses distribution in weld structures. Thus, it shows a great potential in stress modification for metal parts fabricated by additive manufacturing technology. In this paper, an investigation into the ultrasonic treatment process of AlSi10Mg specimens fabricated by selective laser melting (SLM) process was conducted by means of experimental and numerical simulation. The specimens were prepared using a SLM machine, and UPT on their top surface was carried out. The residual stresses were measured with an X-ray stress diffraction device before and after UPT. Meanwhile, a finite element simulation method for analyzing the influence of UPT on the residual stress field of specimens was proposed and validated by experiments. Firstly, the thermal mechanical coupling numerical simulation of the SLM process of the specimen was carried out in order to obtain the residual stress distribution in the as-fabricated specimen. Then, the transient dynamic finite element simulation model of the UPT process of the specimen was established, and the UPT effect analysis was implemented. In the UPT simulation, the residual stress was applied as a pre-stress on the specimen, and the specimen’s material mechanical property was described by the Johnson–Cook model, whose parameters were determined by Split Hopkinson Pressure Bar (SHPB) experiment. The residual stress distribution before and after UPT predicted by the finite element model agree well with the measurement results. This paper concludes with a discussion of the effects of ultrasonic peening time, as well as the frequency and amplitude of the peening needle on residual stress.

Highlights

Metal additive manufacturing technology has been widely used since it has been introduced to the market, in aerospace and biomedical applications
Materials 2019, 12, 455 peening treatment (UPT) technology is used to modify the residual stress by applying high-frequency mechanical peening or vibration on the part surface, which can lead to plastic deformation near the surface [6]
In the early 1970s, the ultrasonic peening method was proposed by Statnikov [7] and it has been widely used in industrial fields such as aerospace, ship and ocean engineering, bridge structures, etc. [8,9,10,11] The International Welding Association has been showing great enthusiasm for the application of Ultrasonic peening treatment (UPT) to post-weld treatments to modify residual stresses [12]

Summary

Introduction

Metal additive manufacturing technology has been widely used since it has been introduced to the market, in aerospace and biomedical applications. The residual stresses generated in continuous transient melting and solidifying process are still a significant barrier for additive manufacturing of high-performance large-size metal parts, which can lead to defects such as excessive deformation and cracking [1,2,3,4,5]. Materials 2019, 12, 455 peening treatment (UPT) technology is used to modify the residual stress by applying high-frequency mechanical peening or vibration on the part surface, which can lead to plastic deformation near the surface [6]. [8,9,10,11] The International Welding Association has been showing great enthusiasm for the application of UPT to post-weld treatments to modify residual stresses [12]. UPT of the weld toe can improve the microstructure and optimize the geometry of the welding joint, so that tensile stresses in the surface areas can be transformed into compressive stresses after UPT, thereby the mechanical properties of parts such as hardness, fatigue life and strength can be improve greatly [13,14,15]

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Results

Conclusion