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Article
Publication date: 24 September 2019

Yezhong Fang, Xiaotian Ji, Xingquan Zhang, Jun Wang, Bin Chen, Shiwei Duan, Jinyu Tong, Guangwu Fang and Shanbao Pei

The purpose of this paper is to investigate the dynamic forming process of the micro dent fabricated by laser shock processing on 2024-T3 aluminum alloy. The effect of…

Abstract

Purpose

The purpose of this paper is to investigate the dynamic forming process of the micro dent fabricated by laser shock processing on 2024-T3 aluminum alloy. The effect of laser pluse energy on the deformation of micro dent was also discussed in detail.

Design/methodology/approach

It uses finite element analysis method and the corresponding laser shocking experiment.

Findings

The results demonstrate that the dynamic formation process of micro dent lasts longer in comparison with the shock wave loading time, and the depths of micro dents increase with the increasing laser energy. In addition, laser shocking with higher energy can result in more obvious pileup occurred at the outer edge of micro dent.

Originality/value

Surface micro dents can serve as fluid reservoirs and traps of the wear debris, which can decrease the effects of the wear and friction in rolling and sliding interfaces. The investigations can not only be propitious to comprehensively understand the forming mechanism of laser-shocked dent, but also be beneficial to get sight into the residual stress field induced by laser shocking.

Details

Multidiscipline Modeling in Materials and Structures, vol. 16 no. 1
Type: Research Article
ISSN: 1573-6105

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Article
Publication date: 11 November 2014

R. Ecault, M. Boustie, L. Berthe, F. Touchard, L. Chocinski-Arnault, H. Voillaume and B. Campagne

The purpose of this paper is to develop a laser shock adhesion test (LASAT) and evaluate its ability to reveal various bond qualities of stuck carbon fiber reinforced…

Abstract

Purpose

The purpose of this paper is to develop a laser shock adhesion test (LASAT) and evaluate its ability to reveal various bond qualities of stuck carbon fiber reinforced polymer (CFRP) industrial assemblies.

Design/methodology/approach

Four grades of adhesion were prepared by release agent contamination of CFRP prior to assembly. Laser shots were performed at different intensities on these samples.

Findings

To characterize and quantify the damage created by the propagation of shock waves in the bonded material, several diagnoses were used (confocal microscopy, ultra-sound inspection and cross-sections microscopy). These three post-mortem techniques are complementary and provide consistent results.

Originality/value

The combination of these diagnoses along with the LASAT technique provides relevant information on the bond quality in agreement with GIC values measured by the University of Patras.

Details

International Journal of Structural Integrity, vol. 5 no. 4
Type: Research Article
ISSN: 1757-9864

Keywords

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Article
Publication date: 7 December 2015

José L. Ocaña, Carlos Correa, Juan A Porro, Marcos Díaz, Leonardo Ruiz de Lara and David Peral

With the aid of the calculational system developed by the authors, the analysis of the problem of laser shock processing (LSP) treatment for induction of residual stress…

Abstract

Purpose

With the aid of the calculational system developed by the authors, the analysis of the problem of laser shock processing (LSP) treatment for induction of residual stress (RS) fields for fatigue life enhancement in relatively thin sheets in a way compatible with reduced overall workpiece deformation due to spring-back self-equilibration has been envisaged. Numerical results directly tested against experimental results have been obtained confirming the critical influence of the laser energy and irradiation geometry parameters. The paper aims to discuss these issues.

Design/methodology/approach

Plane rectangular specimens (160 mm×100 mm×2 mm) of Al-cladded (∼80 μm) Al2024-T351 were considered both for LSP experimental treatment and for corresponding numerical simulation. The test piece is fixed on a holder and is driven along X and Y directions by means of an anthropomorphic robot. The predefined pulse overlapping strategy is used for the irradiation of extended areas of material. From the geometrical point of view, a full 3D configuration for the real geometry and for the sequential overlapping strategy of pulses has been considered. The FEM elements used for the simulation are an eight-node brick reduced integration with hourglass control in the treated area, namely C3D8RT, and a six-node trainer prism in the rest of the geometry, where there is no applied load, namely C3D6T, that ease meshing complex partitions. The element size in the nearest of the treated surface is 100×100×25 µm, being the maximum element size which allows to maintain calculation convergence.

Findings

Numerical results directly tested against experimental results have been obtained confirming: first, the critical influence of the laser energy and irradiation geometry parameters on the possible thin sheets deformation, both at local and global scales. Second, the possibility of finding LSP treatment parameter regimes that, maintaining the requirements relative to in-depth RSs fields, are able to reduce the relative importance of sheet deformation. Third, the possibility of finding LSP treatment parameter regimes able to provide through-thickness compressive RSs fields at levels compatible with an effective fatigue life enhancement. Fourth, the possibility of improving this through-thickness compressive RSs fields by double-side treatments. Fifth, the capability of the experimental LSP treatment system at the authors site (CLUPM) of practically achieve the referred through-thickness compressive RSs fields in excellent agreement with the predictive assessment obtained by the used numerical code (SHOCKLAS®).

Practical implications

The referred results provide a firm basis for the design of LSP treatments able to confer a broad range of RSs fields to thin components aiming the extension of their fatigue life, an enormously relevant field in which the authors are currently working.

Originality/value

The LSP treatment of relatively thin specimens brings, as an additional consequence, the possible bending in a process of laser shock forming. This effect poses a new class of problems regarding the attainment of specified RS’s depth profiles in the mentioned type of sheets, and, what can be more critical, an overall deformation of the treated component. The analysis of the problem of LSP treatment for induction of tentatively through-thickness RS’s fields for fatigue life enhancement in relatively thin sheets in a way compatible with reduced overall workpiece deformation due to spring-back self-equilibration is envisaged in this paper for the first time to the authors knowledge. The coupled theoretical-experimental predictive approach developed by the authors has been applied to the specification of LSP treatments for achievement of RS’s fields tentatively able to retard crack propagation on normalized specimens.

Details

International Journal of Structural Integrity, vol. 6 no. 6
Type: Research Article
ISSN: 1757-9864

Keywords

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Article
Publication date: 30 August 2011

Peter A. Gaydos and Jeff L. Dulaney

Sacrificial opaque overlays used in laser peening provide optimal processing and protect the surface of the part being processed from thermal damage from the laser pulses…

Abstract

Purpose

Sacrificial opaque overlays used in laser peening provide optimal processing and protect the surface of the part being processed from thermal damage from the laser pulses. Traditional solid film overlays for laser peening often require several applications and the running of multiple partial laser peening sequences in order to completely process the desired surface. This paper aims to discuss an automated overlay system that eliminates these issues.

Design/methodology/approach

LSP Technologies' (LSPT') patented RapidCoater™ automated overlay system provides optimal laser processing and surface protection by providing a conformal opaque layer that is automatically refreshed between each laser pulses. PLC control provides precise timing of the application of the process overlays in synchronization with the laser pulse.

Findings

Use of the RapidCoater system has been shown to reduce processing time by up to five times when compared to using tape overlays. Cost reductions of about 40 percent are also achieved.

Originality/value

LSPT, Inc. invented and developed this proprietary technology to provide its laser peening customers with higher productivity and improved process affordability.

Details

International Journal of Structural Integrity, vol. 2 no. 3
Type: Research Article
ISSN: 1757-9864

Keywords

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Article
Publication date: 1 February 1997

J. Vuillon and D. Zeitoun

High‐power chemical lasers operating in high repetitive rate show a decrease of the output energy laser beam. In such lasers, the characteristic time which depends on the…

Abstract

High‐power chemical lasers operating in high repetitive rate show a decrease of the output energy laser beam. In such lasers, the characteristic time which depends on the laser output is short in comparison with those related to the flow. Consequently, shock waves, acoustic waves and thermal perturbations, induced by the strong electric energy deposition and remaining in the laser cavity between two pulses, may explain the decrease of output energy of the laser beam. For a better understanding of the flowfields, a numerical approach is carried out using flux corrected transport algorithms (FCT methods) associated with a Riemann solver on the computational domain boundaries. Under two‐dimensional assumptions, the inviscid flow in the convergent‐divergent laser cavity is computed to describe the creation and propagation of the wave system and the hot gas column in both single and multidischarge operating modes. Distortions of the contact surfaces are put into evidence through the study of flowfield instabilities. Finally, the limitations of the two‐dimensional modelization become apparent. The numerical resolution is extended to a 3D case in order to take into account the optical direction. This allows to study the influence of shock waves travelling between optics and being generated by a side effect developing at the electrodes. These waves have an effect of long duration on the flowfield and lead to a high residual perturbation level.

Details

International Journal of Numerical Methods for Heat & Fluid Flow, vol. 7 no. 1
Type: Research Article
ISSN: 0961-5539

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Article
Publication date: 8 March 2011

Patrice Peyre, Neila Hfaiedh, Hongbin Song, Vincent Ji, Vincent Vignal, Wilfrid Seiler and Stephane Branly

The purpose of this paper is to conduct a comparative study of the surface modifications induced by two different lasers on a 2050‐T8 aluminum alloy, with a specific…

Abstract

Purpose

The purpose of this paper is to conduct a comparative study of the surface modifications induced by two different lasers on a 2050‐T8 aluminum alloy, with a specific consideration of residual stress and work‐hardening levels.

Design/methodology/approach

Two lasers have been used for Laser shock peening (LSP) treatment in water‐confined regime: a Continuum Powerlite Plus laser, operating at 0.532 mm with 9 ns laser pulses, and near 1.5mm spot diameters; a new generation Gaia‐R Thales laser delivering 10 J‐10 ns impacts, with 4‐6mm homogeneous laser spots at 1.06 mm. Surface deformation, work‐hardening levels and residual stresses were analyzed for both LSP conditions. Residual stresses were compared with numerical simulations using a 3D finite element (FE) model, starting with the validation of surface deformations induced by a single laser impact.

Findings

Similar surface deformations and work‐hardening levels, but relatively lower residual stresses were obtained with the new large 4‐6 mm impact configuration. This was attributed to a reduced number of local cyclic loadings (2) compared with the small impact configuration (4). Additionally, more anisotropic stresses were obtained with small impacts. FE simulations using Johnson‐Cook's material' behavior were shown to simulate accurately surface deformations, but to overestimate maximum stress levels.

Research limitations/implications

This work should provide LSP workers a better understanding of the possible benefits from the different LSP configurations currently co‐existing: using small (<2 mm) impacts at high‐cadency rates or large ones (>4‐5 mm). Moreover, experimental results and simulated data had never been presented on 2050‐T8 Al alloy.

Originality/value

An experimental (and numerical) comparison using two distinct laser sources for LSP, has never been presented before. This preliminary work should help LSP workers to choose adequate sources.

Details

International Journal of Structural Integrity, vol. 2 no. 1
Type: Research Article
ISSN: 1757-9864

Keywords

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Article
Publication date: 8 March 2011

Miguel Morales, Carlos Correa, Juan Antonio Porro, Carlos Molpeceres and José Luis Ocaña

Laser shock peening (LSP) is mainly a mechanical process, but in some cases, it is performed without a protective coating and thermal effects are present near the surface…

Abstract

Purpose

Laser shock peening (LSP) is mainly a mechanical process, but in some cases, it is performed without a protective coating and thermal effects are present near the surface. The numerical study of thermo‐mechanical effects and process parameter influence in realistic conditions can be used to better understand the process.

Design/methodology/approach

A physically comprehensive numerical model (SHOCKLAS) has been developed to systematically study LSP processes with or without coatings starting from laser‐plasma interaction and coupled thermo‐mechanical target behavior. Several typical results of the developed SHOCKLAS numerical system are presented. In particular, the application of the model to the realistic simulation (full 3D dependence, non‐linear material behavior, thermal and mechanical effects, treatment over extended surfaces) of LSP treatments in the experimental conditions of the irradiation facility used by the authors is presented.

Findings

Target clamping has some influence on the results and needs to be properly simulated. An increase in laser spot radius and an increase in pressure produces an increase of the maximum compressive residual stress and also the depth of the compressive residual stress region. By increasing the pulse overlapping density, no major improvements are obtained if the pressure is high enough. The relative influence of thermal/mechanical effects shows that each effect has a different temporal scale and thermal effects are limited to a small region near the surface and compressive residual stresses very close to the surface level can be induced even without any protective coating through the application of adjacent pulses.

Originality/value

The paper presents numerical thermo‐mechanical study for LSP treatments without coating and a study of the influence of several process parameters on residual stress distribution with consideration of pulse overlapping.

Details

International Journal of Structural Integrity, vol. 2 no. 1
Type: Research Article
ISSN: 1757-9864

Keywords

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Article
Publication date: 8 March 2011

Kelly S. Carney, Omar Hatamleh, James Smith, Thomas Matrka, Amos Gilat, Michael Hill and Chanh Truong

The purpose of this paper is to present an analytical framework for predicting the residual stresses that result from the laser shock peening of a friction stir‐welded…

Abstract

Purpose

The purpose of this paper is to present an analytical framework for predicting the residual stresses that result from the laser shock peening of a friction stir‐welded 2195 aluminum alloy sample, using the finite element software LS‐DYNA.

Design/methodology/approach

The pressures resulting from the laser peening are directly applied in an explicit transient analysis as forces. At the completion of the transient analysis, an implicit springback analysis is performed to determine the final residual stresses. This cycle is repeated for the appropriate number of peen applications, including the appropriate overlap of application areas. To validate the analytical framework, a comparison of residual stresses between analysis and a test specimen is made using laser‐peened base material which was not friction stir‐welded. Friction stir welding (FSW) causes residual stresses and material property variations. In this work, the varying material properties regions are simplified and defined as discrete, separate materials. The residual stresses resulting from the welding are introduced directly as initial conditions in the peening transient analysis and so are combined within the analysis with the residual stresses from the peening.

Findings

Comparisons made between the experimental and analytical residual stresses are generally favorable.

Originality/value

Analysis of the laser shock peening of FSW has not been accomplished previously.

Details

International Journal of Structural Integrity, vol. 2 no. 1
Type: Research Article
ISSN: 1757-9864

Keywords

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Article
Publication date: 2 February 2015

Anoop Vasu and Ramana V. Grandhi

The impact of laser peening on curved geometries is not fully comprehended. The purpose of this paper is to explain the action of laser peening on curved components…

Abstract

Purpose

The impact of laser peening on curved geometries is not fully comprehended. The purpose of this paper is to explain the action of laser peening on curved components (concave and convex shapes for cylindrical and spherical geometries) by means of shock wave mechanics.

Design/methodology/approach

An analytical formulation is derived based on the plasticity incurred inside the material and the results are compared with the prediction by numerical simulation.

Findings

A near-linear relationship is observed between curvature and compressive residual stress; an increasing trend was observed for concave models and a decreasing trend was observed for convex models. The consistency in the analytical formulation with the simulation model indicates the behavior of laser peening for curved geometries.

Originality/value

The differences observed in the residual stresses for spherical and cylindrical geometries are primarily due to the effect of Rayleigh waves. This paper illustrates the importance of understanding the physics behind laser peening of curved geometries.

Details

International Journal of Structural Integrity, vol. 6 no. 1
Type: Research Article
ISSN: 1757-9864

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Article
Publication date: 8 March 2011

Uroš Trdan, Sebastjan Žagar, Janez Grum and José Luis Ocan˜a

The purpose of this paper is to investigate the effect of shock waves and strain hardening effect of laser and shot peening on precipitation‐hardened aluminium alloy AA 6082‐T651.

Abstract

Purpose

The purpose of this paper is to investigate the effect of shock waves and strain hardening effect of laser and shot peening on precipitation‐hardened aluminium alloy AA 6082‐T651.

Design/methodology/approach

The hardened layer was evaluated by means of surface integrity with optical microscopy, scanning electron microscope (SEM), energy dispersive spectroscopy, analysis of microhardness and residual stress profiles. Corrosion anodic polarization tests in a 3.5 per cent NaCl water solution were carried out to express a pitting potential and the degree of pitting attack, which was verified on SEM and with 3D metrology.

Findings

Research results indicated significant differences between two treatment techniques which had an important influence on the final condition of the surface layer. Potentiodynamic polarization tests inferred that laser peening enabled shift of the pitting potential to more positive values, which ensures higher corrosion resistance.

Originality/value

Results confirmed that the higher corrosion resistance of the laser‐peened specimens against pitting corrosion depends on the modification of the surface, due to ablation during plasma generation. Despite increased surface roughness, laser‐peened specimen exhibits beneficial increase of the pitting/breakdown potential and in reduction of pitting attack degree at the specimen surface.

Details

International Journal of Structural Integrity, vol. 2 no. 1
Type: Research Article
ISSN: 1757-9864

Keywords

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