Multiple Laser Shock Research Articles

Mechanical behaviour and subsurface characteristics of Ti-6Al-4V subjected to electropulsing-assisted multiple laser shock processing impacts

Mechanical behaviour and subsurface characteristics of Ti-6Al-4V subjected to electropulsing-assisted multiple laser shock processing impacts

Reducing the Rebound Effect in Microscale Laser Dynamic Forming through Multi-Pulse Laser Shock Loading

Microscale laser dynamic forming, as a novel high-speed microforming technique, can overcome the shortcomings of traditional microforming methods. However, in practical applications, laser dynamic microforming technology is often affected by the rebound behavior of the workpiece, limiting the further improvement of processing quality and efficiency. This paper aims to reduce the rebound effect in laser dynamic forming by using multi-pulse laser shock loading. The forming results of workpieces under different laser energies and laser impact numbers were studied using experimental and numerical simulation methods. After multiple laser shocks, numerical simulations of the forming results were conducted using ANSYS/LS-DYNA software. These numerical simulation results were then experimentally validated and compared. The surface morphology of the workpieces was characterized using a confocal microscope and a scanning electron microscope (SEM). Energy-dispersive spectroscopy (EDS) was used to analyze the chemical element content changes in the collision regions at the bottoms of the workpieces after multi-pulse loading. The SEM and EDS results revealed the collision behavior patterns during the forming process. Finally, the forming laws of workpieces under multiple laser shocks were summarized.

Research on the residual stress induced by square-spot laser shock peening on 2024-T351 specimens

Laser peen forming (LPF) is an appealing technique for forming metal sheets using high-energy, short-duration laser pulses. The deformation of the target metal plate is closely related to the magnitude and distribution of laser-induced residual stress. Consequently, the relationship between process parameters and residual stress is worth researching. In this research, two process parameters in LPF, laser energy and coverage ratio (spot distance essentially), and one workpiece parameter, plate thickness, were examined through an element method (FEM) of multiple square-spot laser shock peening (SSLSP). Corresponding experiments of SSLSP on aluminum alloy 2024-T351 test blocks were conducted, together with an X-ray diffraction (XRD) residual stress measurement and a surface morphology observation. The FEM simulation and experimental results show that congested laser spots had a significant influence on the magnitude of compressive residual stress; higher laser energy was beneficial to the depth of the compressive stress layer but could decrease its magnitude. Therefore, for better forming ability, higher laser energy and a higher coverage ratio are beneficial; for surface strengthening, laser energy should not be too large, and the coverage ratio should be larger than 100% to ensure that the residual stress on the treated surface is compressive, resulting in better surface integrity.

Strain and defect engineering of high-performance monolayer two-dimensional material/Ag nanoparticles optoelectronic FET sensor through multiple laser shock

The development of sensor devices that detect low-concentrations hydrogen at room temperature is becoming increasingly important for the safe use of hydrogen. In this study, the introduction of strain and defects in two-dimensional materials has been realised by laser shock and its application in gas sensing. The strain and defect density of monolayer MoS2 increase after multiple laser shock, providing more active sites for gas adsorption and improving the ability to adsorb hydrogen atoms. Under the synergistic effect of strain and defects, the response of non-noble metal nanoparticles/MoS2 photoelectric hydrogen sensors is accelerated, and their sensing performance (83% for 200 ppm) is 9.5 times higher than that of pure MoS2 devices (8.7% for 200 ppm) at room temperature (25 ℃). As a proof of concept, laser shock induced 2D material strain and defect engineering has opened up new ideas for improving the performance of photoelectric gas sensors at room temperature.

Effect of multiple laser shock peening on the microstructure and properties of laser cladding nano-WC/Ni60 composite coatings

Effect of multiple laser shock peening on the microstructure and properties of laser cladding nano-WC/Ni60 composite coatings

Effect of multiple laser shock peening without coating on residual stress distribution and high temperature dry sliding wear behaviour of Ti-6Al-4 V alloy

Effect of multiple laser shock peening without coating on residual stress distribution and high temperature dry sliding wear behaviour of Ti-6Al-4 V alloy

Effects of multiple laser shock peening impacts on microstructure and wear performance of wire-based laser directed energy deposition 17-4PH stainless steel

As an advanced surface-strengthening technology, laser shock peening (LSP) is suitable for strengthening high-energy beam additive manufacturing components by improving the uneven temperature distribution and mechanical anisotropy problems. The present study investigated the influence of multiple LSP impacts on the microstructure evolution and wear performance of wire-based laser directed energy deposition (LDED) 17-4 PH stainless steel. Results showed that with the increase of LSP impacts, the average grain size of the wire-based LDED layer decreases and the dislocation density increases. Meanwhile, the residual stress was completely converted from tensile state to compressive state, and reaches the maximum value of 424 ± 15 MPa. In addition, the significant improvement of microhardness and wear resistance after 3 LSP impacts is attributed to the combined effects of grain refinement and dislocation strengthening.

Stepwise varying of laser parameters to enhance the residual stress field in multiple laser shock processing: numerical verification of single-point region

Stepwise varying of laser parameters to enhance the residual stress field in multiple laser shock processing: numerical verification of single-point region

Optimize Multiple Peening Effects on Surface Integrity and Microhardness of Aluminum Alloy Induced by LSP

Laser shock peening is a modernized surface enhancement performed methodically to improve fatigue life, enhance the hardness of the material and make coarse grains flat under the superficial layer. In this current study, the effect of varying optimized multiple laser shock peening (LSP) is studied on the surface integrity, microhardness, and mechanical properties. The results show that the LSP-treated specimens have visible signs of valleys, wavy and varying height distribution as well as dimples. However, the presence of non-uniformity and sharp protrusions was detected from the superficiality of the as-received specimen and this was so because of the SiC abrasive material used to polish the superficial layer of the specimen before the test experiment. Prior to LSP, the surface roughness was 2 μm, however, after LSP the roughness increased to 4 μm, 6 μm and 17 μm for 1, 2, and 4 impacts, respectively. High-density dislocation can also be observed close to the grain boundary because the grain boundary prevents the migration of dislocation which could lead to dislocation walls and dislocation tangles. The increase in impacts decrease the average grain size, nevertheless, the micro-strain increased after multiple impacts. Furthermore, coarse grains after LSP were transformed into finer grains. The increase in the number of impacts increases the micro-strain likewise the full-width half maximum (FWHM). Finally, the increase in microhardness increases as the LSP impacts increase.

Phase transformations mechanism in commercially pure titanium subjected to multiple laser shock peening

The phase transformations in commercially pure (CP) titanium subjected to multiple laser shock peening (LSP) impacts were investigated by means of scanning electron microscopy (SEM), X-ray Diffraction (XRD) and transmission electron microscopy (TEM) observations. The results showed that the LSPed samples underwent α → ω → fcc→α phase transformations as a function of the number of laser shock impacts. The α → ω phase transformation occurred during the second shock impact. The orientation relationship (OR) was {0001}ω//{11−20}α, which was consistent with the Silcock pathway. The fcc-Ti appeared after the third impact, and the content of fcc-Ti in the samples first increased and then decreased with the impact times. The α → ω → fcc phase transformations could be attributed to the input energy accumulation by multiple laser shocks, which refined the grains and formed lots of nano twins. The fcc→α reverse transformation may be related to the residual heating which is converted from laser shock energy.

A Study on Effect of Multiple Laser Shock Peening on Microstructure, Residual Stress, and Mechanical Strength of 2.5 Ni-Cr-Mo (EN25) Low-Alloy Steel

A Study on Effect of Multiple Laser Shock Peening on Microstructure, Residual Stress, and Mechanical Strength of 2.5 Ni-Cr-Mo (EN25) Low-Alloy Steel

Prediction about residual stress and microhardness of material subjected to multiple overlap laser shock processing using artificial neural network

Prediction about residual stress and microhardness of material subjected to multiple overlap laser shock processing using artificial neural network

Study on the Effects of Multiple Laser Shock Peening Treatments on the Electrochemical Corrosion Performance of Welded 316L Stainless Steel Joints

To study the influence of laser shock peening on the electrochemical corrosion resistance of welded 316L stainless steel joints, welded 316L stainless steel joints are treated with different laser shock peening treatments (i.e., one, two, and three times). Our analysis employs electron backscattering diffraction (EBSD), scanning electron microscopy (SEM), X-ray diffraction (XRD), an X-ray stress meter, and electrochemical corrosion tests to observe and analyze the microstructure, structural composition, residual stress, and corrosion resistance in different areas of the surface of 316L before and after the laser shock peening. The results show that the residual stress distribution of the welded joints is optimized after laser shock peening, with a maximum residual compressive stress near the matrix of 171 MPa. When the number of laser shock peening treatments is two, the corrosion current reaches a minimum of 9.684×10−7 A/cm2, and optimal pitting resistance is obtained. However, when the number of laser shock peening treatments is further increased to three, the corrosion current increase and the pitting resistance decreases. In summary, the electrochemical corrosion resistance of the welded joints effectively improves after laser shock peening, but its performance begins to decline after three repeated shocks, which is related to the combined effects of stress change and microstructure phase transformation.

Plastic deformation behavior of 316 stainless steel subjected to multiple laser shock imprinting impacts

Laser shock imprinting (LSI) is used to fabricate imprinted morphology on the surface of 316 stainless steel. The profile and the height variation of imprinted morphology on the sample surface treated by multiple LSI impacts were investigated by experiment and finite element modeling (FEM) simulation. The results showed that after initial LSI impact, micro bulges were imprinted on the sample surface accompanied with the generation of gradient deformation, work hardening effect and compressive residual stress. When the subsequent LSI impacts were performed, the sample surface deformed with a lower rate because of the existence of work hardening effect and compressive residual stress. The height of bulges decreased, which was due to the effect of the gradient deformation induced by laser shock wave to imprinted zone.

Effects of residual stress induced by laser shock peening on mixed-mode crack propagation behavior in 7075-T6 aluminum alloy panel

The effects of residual stress on mixed-mode crack propagation behavior of 7075-T6 aluminum alloy panel subject to multiple laser shock peening (LSP) impacts were investigated. Residual stress was obtained by an efficient LSP simulation termed continuous explicit-dynamic impact strategy. A numerical method, combining finite element (FE) method and residual stress intensity factor (SIF) analysis, was used to predict the mixed-mode (I/II) crack propagation in peened compact tension shear (CTS) sample. The effects of residual stress on the mixed-mode crack behaviors in different coverage areas were analyzed. It was found that the LSP-induced residual stress can change the crack path. Compressive residual stresses increase the effective crack length, and delay the crack propagation. The increased LSP coverage area and the decreased distance from the treated area to the crack tip are beneficial to the fatigue performance. The obvious crack turning point near the peened area is related to the significant change of mode II SIF components (KIIload and KIIres). The proposed numerical method provides a new idea for the damage tolerance analysis with respect to the applications of LSP technology in aircraft structures.

Influence of multiple laser shock peening treatments on the microstructure and mechanical properties of Ti−6Al−4V alloy fabricated by electron beam melting

Influence of multiple laser shock peening treatments on the microstructure and mechanical properties of Ti−6Al−4V alloy fabricated by electron beam melting

Optimization of multiple laser shock peening on high-cycle fatigue performance of aluminized AISI 321 stainless steel

Herein, the effect of multiple laser shock peening (LSP) on fatigue performance of aluminized steel and de-twinning behavior during cyclic deformation are investigated. Results reveal their fatigue lives successively increase within LSP times ranging from 0 to 3. Instead, life degradation is noticed after 4th LSP due to damaged adsorption layer. Consequently, the negative thermal ablations release compressive residual stress and form σ phase, accelerating crack propagation. Thus, triple LSP impacts are determined as optimal condition for fatigue resistance of aluminized steel. According to twinning dislocation initiations and glide directions, the underlying de-twinning mechanisms during cyclic deformation are also discussed.

Experimental Investigation of Multiple Laser Shock Peening on Mechanical Properties of Laser Sintering Additively Manufactured Maraging Steel

Experimental Investigation of Multiple Laser Shock Peening on Mechanical Properties of Laser Sintering Additively Manufactured Maraging Steel

Effect of multiple laser shock peening on microstructure, crystallographic texture and pitting corrosion of Aluminum-Lithium alloy 2060-T8

This study investigated the influence of multiple laser shock peening on microstructure, crystallographic texture, and pitting corrosion behavior of Aluminum-Lithium alloy 2060-T8 (in 3.5% NaCl) using EBSD, SEM and XPS techniques. Results show that microstructure and crystallographic texture were noticeably influenced by the peening passes. At single peening, plastic strain accommodation was homogenous, resulting in higher fraction of low Σ CSL boundaries, and significant crystallographic texture transformation from fibre (unpeened) into Cube {001}〈100〉 component (corresponding to dynamic recovery as plastic deformation mode) was induced. In contrast, repetitive peening (3 & 5 passes) induced heterogeneous plastic strain accommodation, developed random and low angle grain boundaries, and texture transformation from fibre to Goss {011}〈100〉, implying recrystallization as corresponding plastic deformation mode. As a result of dense atomic structured microstructures/textures, pitting corrosion after single peening was significantly lowered than that of multiple peening. Major reason for the improved corrosion behavior at single peening pass was the formation of dense and uniform α-Al2O3 type oxide film, which significantly lowered the materials dissolution. Whereas, multiple peening led to the formation of porous γ-Al2O3, θ-Al2O3 oxides and Cu-rich regions, which activated the deeper and wider pitting. Besides, the effect of precipitates (Al2CuLi, θ′ (Al2Cu) and β′ (Al3Zr)) on pitting corrosion is quantitatively examined.

Surface residual stress, micro-hardness and geometry of TC6 titanium alloy thin-wall parts processed by multiple oblique laser shock peening

The titanium alloy thin-walled part with light in weight and high specific strength is widely used in the aviation engine fan, turbine and compressor. The fatigue damage of the thin-walled part often happens under the action of the cyclic loads and high temperatures. Laser shock peening(LSP) is an innovative surface treatment process, which has been used to improve the fatigue life of metallic materials. Considering the shape and size of the thin-walled parts, the TC6 titanium alloy thin-wall parts were treated by the oblique incident laser beam in this work. The purpose of this study is to investigate the effects of multiple oblique LSP on TC6 titanium alloy thin-wall parts. Nd: YLF laser with a wavelength of 1053 nm was applied. The laser incidence angle was determined first by experiment. The effects of laser energies, impact times, pulse durations and pulse frequencies on the surface residual stress, micro-hardness and geometry of TC6 titanium alloy thin-wall parts were investigated. The results showed that by the use of oblique LSP, the higher surface residual stress and surface micro-hardness could be induced on the surface of treated specimens. However, surface deformation and surface roughness of treated specimens can also increase.