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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.

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

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.

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.

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.

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.

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.

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.

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.

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.

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®).

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.

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.

This study aims to review the recent advancements in high entropy alloys (HEAs) called high entropy materials, including high entropy superalloys which are current potential alternatives to nickel superalloys for gas turbine applications. Understandings of the laser surface modification techniques of the HEA are discussed whilst future recommendations and remedies to manufacturing challenges via laser are outlined.

Materials used for high-pressure gas turbine engine applications must be able to withstand severe environmentally induced degradation, mechanical, thermal loads and general extreme conditions caused by hot corrosive gases, high-temperature oxidation and stress. Over the years, Nickel-based superalloys with elevated temperature rupture and creep resistance, excellent lifetime expectancy and solution strengthening L12 and γ´ precipitate used for turbine engine applications. However, the superalloy’s density, low creep strength, poor thermal conductivity, difficulty in machining and low fatigue resistance demands the innovation of new advanced materials.

HEAs is one of the most frequently investigated advanced materials, attributed to their configurational complexity and properties reported to exceed conventional materials. Thus, owing to their characteristic feature of the high entropy effect, several other materials have emerged to become potential solutions for several functional and structural applications in the aerospace industry. In a previous study, research contributions show that defects are associated with conventional manufacturing processes of HEAs; therefore, this study investigates new advances in the laser-based manufacturing and surface modification techniques of HEA.

The AlxCoCrCuFeNi HEA system, particularly the Al0.5CoCrCuFeNi HEA has been extensively studied, attributed to its mechanical and physical properties exceeding that of pure metals for aerospace turbine engine applications and the advances in the fabrication and surface modification processes of the alloy was outlined to show the latest developments focusing only on laser-based manufacturing processing due to its many advantages.

It is evident that high entropy materials are a potential innovative alternative to conventional superalloys for turbine engine applications via laser additive manufacturing.

The purpose of this study is to reduce the cracks, pores and unfused defects in arc welding, improve the crystalline structure of the weld, refine its grains and improve the mechanical properties.

Taking E690 marine steel as the research object, the experiment adopts a new process method of laser forging coupled arc welding. Welding for comparative experiments. Experiments show that the “V”-shaped groove arc welding process has a larger fusion area, but has pores, the arc current is 168 A, the arc voltage is 28 V and the welding speed is 600 mm/min.

It can be seen from tensile tests that the coupling welding process has the highest tensile strength and yield strength, 872 MPa and 692 MPa, respectively, and the fracture elongation is 29.29%. The single-beam laser forging coupled arc welding process has a distance of laser and wire of 6–8 mm, a laser wavelength of 1,064 nm and the highest weld fusion ratio. The microhardness test shows that the average hardness of single-beam laser forging in the weld zone is 487.54 HV, which is 10.30% higher than that of arc welding. The average hardness in the fusion zone is 788.08 HV, which is 14.52% higher than that of the arc welding process.

The originality of the experiment: proposed a new process method of coupling arc repair for offshore steel forging; adopted a new process method of simultaneous coupling of single-beam short-pulse laser, double-beam short-pulse laser and arc welding; and obtained effect of pulsed laser and arc composite repair on porosity and fusion of E690 marine steel welds.

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.

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.

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.

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

This paper aims to review the effect of traditional shot peening (SP), laser shock peening (LSP) and water jet cavitation peening (WJP) on microstructure evolution and corrosion behavior of austenitic stainless steels 316L and 304.

The effect of SP, LSP and WJP on corrosion behavior of 316L and 304 were discussed in terms of surface peening–induced change in surface roughness, stress state and grain size.

Residual compressive stress and grain refinement were introduced after SP, LSP and WJP treatment in 316L and 304 stainless steels. Superior corrosion resistance can be obtained by WJP compared with SP and LSP.

The relationship between SP-, LSP- and WJP-induced change in microstructure and stress state and corrosion resistance was summarized.

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.

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.

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.

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.

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.

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.

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.

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.

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.

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.