Enhancement of Material Crack Resistance Using Laser Shock Processing
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TECHNOLOGIES IN MECHANICAL ENGINEERING
Enhancement of Material Crack Resistance Using Laser Shock Processing G. Zh. Sakhvadze Blagonravov Institute of Mechanical Engineering, Russian Academy of Sciences, Moscow, 101990 Russia e-mail: [email protected] Received February 7, 2020; accepted March 27, 2020
Abstract—In this paper, we develop a numerical model that allows predicting the effect of laser shock processing of materials on the occurrence of new cracks, as well as on the propagation pattern of existing cracks. Linear cracks and so-called V-shaped cracks are studied. The fields of residual stresses arising during laser shock processing are determined. The optimal modes of laser shock processing in terms of the maximal deceleration of the propagation velocity of the cracks are revealed. The results obtained are in good agreement with the experimental data. Keywords: laser shock processing, finite element method, residual stresses, stress intensity factor, crack growth rate, crack resistance. DOI: 10.3103/S1052618820040123
Laser shock processing (LSP) of materials is a new surface treatment technology that is widely used to improve the fatigue characteristics of critical high-load machine parts. During the LSP, a high-power laser pulse penetrates through a transparent layer (usually a layer of water or glass) and focuses on the protective layer deposited on the test sample, which immediately ionizes and becomes a high-temperature plasma [1–6]. Then, this plasma explodes and creates high pressure (on the order of several GPa) for a very short period of time (10–20 ns), which leads to the generation of compressive residual stresses (CRSs) on the surface and in the near-surface regions of materials. Since it is well known that a fatigue crack can be stopped or slowed down if there are CRSs along the crack propagation path [4], it should be expected that the LSP technology can improve the fatigue performance by creating CRSs. These advantages certainly make the LSP a promising surface hardening technology for improving fatigue durability and crack resistance, especially for small and important highly loaded parts such as bearings, gears, and shafts. They are usually often used in the aerospace, energy, engineering, and biomedical industries. RESEARCH METHODOLOGY Let us describe the general methodology used in this paper. The numerical model (NM) consists of two parts: (i) FEM analysis using the finite element method (FEM, this part is circled by dashed lines in Fig. 1) to simulate the LSP technology and determine the residual stresses (RSs), and (ii) SIF analysis (SIF is the stress intensity factor). The FEM procedure was performed using the Abaqus finite element package. First, preparatory calculations are performed and the material model, loading conditions, and degree of mesh sampling are determined (Fig. 1). The RS field obtained based on the FEM procedure is used as input in the model for the SIF analysis (to obtain the residual stress intensity coefficient or RSIC). The general block diagram of numerical modeli
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