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Gary J. Cheng - One of the best experts on this subject based on the ideXlab platform.
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[INVITED] A review: Warm Laser Shock Peening and related Laser processing technique
Optics and Laser Technology, 2016Co-Authors: Yiliang Liao, Chang Ye, Gary J. ChengAbstract:This paper reviews the recent progress in warm Laser Shock Peening (WLSP) and related Laser processing technique. The process design, enhanced mechanical performance, and microstructure evolution of WLSP are discussed in details. The fundamental process mechanism is reviewed by building the processing-microstructure-property relationship. In particular, the precipitation kinetics during WLSP is discussed to study the effect of process parameters on the nucleation of nano-precipitates, and multiscale discrete dislocation dynamics (MDDD) simulation results are summarized to investigate the dislocation multiplication and propagation behaviors as well as the dislocation pinning effect. In addition, the research progress of thermal engineered Laser Shock Peening (TE-LSP) technique is reviewed with a focus on the coarsening of precipitates, the extended fatigue life, and more importantly, the fundamental process mechanism.
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the mechanisms of thermal engineered Laser Shock Peening for enhanced fatigue performance
Acta Materialia, 2012Co-Authors: Yiliang Liao, Sergey Suslov, Gary J. ChengAbstract:Abstract Thermal engineered Laser Shock Peening (LSP) is a technique combining warm Laser Shock Peening (WLSP) with subsequent post-Shock tempering treatment to optimize the surface strength and fatigue performance of metallic materials. This technique integrates the advantages of LSP, dynamic strain aging (DSA), dynamic precipitation (DP) and post-Shock tempering to obtain optimized microstructures for extending fatigue life, such as nanoprecipitates and highly dense dislocations. In this work, AISI 4140 steel is used to evaluate the thermal engineered LSP process. The resulting microstructures as well as mechanical properties are studied under various processing conditions. The mechanism underlying the improvements in fatigue performance is investigated. It is found that the extended fatigue life is mainly caused by the enhanced cyclic stability of compressive residual stress as well as surface strength. This improved material stability and reliability are attributed to the enhanced dislocation pinning effect corresponding to the number density, size and space distribution of nanoprecipitates, which could be tailored by manipulating the WLSP processing conditions and by post-Shock tempering. The effects of the precipitate parameters on the precipitation kinetics as well as on the dislocation pinning strength are discussed.
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deformation induced martensite and nanotwins by cryogenic Laser Shock Peening of aisi 304 stainless steel and the effects on mechanical properties
Philosophical Magazine, 2012Co-Authors: Chang Ye, Sergey Suslov, Gary J. ChengAbstract:Laser Shock Peening (LSP) of stainless steel 304 was carried out at room and cryogenic temperature (liquid nitrogen temperature). It was found that the deformation-induced martensite was generated by LSP only when the Laser-generated plasma pressure is sufficiently high. Compared to room temperature Laser Shock Peening (RT-LSP), cryogenic Laser Shock Peening (CLSP) generates a higher volume fraction of martensite at the same Laser intensity. This is due to the increase in the density of potential embryos (deformation bands) for martensite nucleation by deformation at cryogenic temperature. In addition, CLSP generates a high density of deformation twins and stacking faults. After CLSP, an innovative microstructure, characterised by networks of deformation twins, stacking faults and composite structure (martensite and austenite phases), contributes to material strength and microstructure stability improvement. The combined effect of higher surface hardness and a more stabilised microstructure results in gre...
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Finite Element Analysis of the Variation in Residual Stress Distribution in Laser Shock Peening of Steels
JOURNAL OF MANUFACTURING SCIENCE AND ENGINEERING-TRANSACTIONS OF THE ASME, 2012Co-Authors: Rohit Voothaluru, C Richard Liu, Gary J. Cheng, C. Richard LiuAbstract:Laser Shock Peening (LSP) is a surface treatment technique similar to\nconventional shot Peening. The Laser induced plasma causes plastic\ndeformations and compressive residual stresses that are useful for\ndeveloping improved properties in the fields of resistance to fatigue,\nwear or stress corrosion cracking. The actual distribution of residual\nstresses is extremely important while designing for improved fatigue\nlife using Laser Shock Peening, as fatigue cracks would initiate from\nthe weakest point in the structure. In this paper, the variations in\ndistribution of residual stresses due to Laser Shock Peening are studied\nwith a focus on two materials, annealed 1053 and hardened 52100 AISI\nsteels. A 3D finite element model was developed to study the actual\ndistributions of the residual stresses due to Laser Shock Peening. The\neffect of hardness on the distribution of the residual stresses and the\npresence of tensile residual stresses in the surrounding regions of the\nimpact is analyzed. Much larger variations in the residual stress\ndistributions were observed in case of the 1053 steel as compared to\nhardened 52100 steel. A comprehensive analysis of the simulation results\nwas performed in order to address and explain this behavior. It was\nobserved that the extent of overlap would also affect the variations in\nthe residual stress distributions. The tensile residual stresses present\nin the areas surrounding the Shocked region were also analyzed based\nupon the extent of overlap and the hardness of the material. It was\nobserved that the ratio of peak tensile to compressive residual stresses\ndeveloped in 1053 steel was much higher as compared to that in the\nhardened 52100 steel. {[}DOI: 10.1115/1.4007780]
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Microstructure and mechanical properties of copper subjected to cryogenic Laser Shock Peening
Journal of Applied Physics, 2011Co-Authors: Sergey Suslov, Yiliang Liao, Dong Lin, Xueling Fei, Gary J. ChengAbstract:In this study, an innovative materials processing technique, cryogenic Laser Shock Peening (CLSP), is investigated. Copper is processed by Laser Shock Peening (LSP) at the cryogenic temperature and compared with LSP at room temperature (RT-LSP). The microstructure of copper after processing is characterized by transmission electron microscopy (TEM). Nanotwins were observed in copper after CLSP due to the effect of cryogenic temperature. In addition, more energy is stored in the material as defects (dislocations) by CLSP compared to RT-LSP. Because of these unique microstructure changes, it is found that high material strength with good thermal stability is achieved after CLSP. The mechanical properties after CLSP, RT-LSP, and as-received are compared.
Chang Ye - One of the best experts on this subject based on the ideXlab platform.
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[INVITED] A review: Warm Laser Shock Peening and related Laser processing technique
Optics and Laser Technology, 2016Co-Authors: Yiliang Liao, Chang Ye, Gary J. ChengAbstract:This paper reviews the recent progress in warm Laser Shock Peening (WLSP) and related Laser processing technique. The process design, enhanced mechanical performance, and microstructure evolution of WLSP are discussed in details. The fundamental process mechanism is reviewed by building the processing-microstructure-property relationship. In particular, the precipitation kinetics during WLSP is discussed to study the effect of process parameters on the nucleation of nano-precipitates, and multiscale discrete dislocation dynamics (MDDD) simulation results are summarized to investigate the dislocation multiplication and propagation behaviors as well as the dislocation pinning effect. In addition, the research progress of thermal engineered Laser Shock Peening (TE-LSP) technique is reviewed with a focus on the coarsening of precipitates, the extended fatigue life, and more importantly, the fundamental process mechanism.
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deformation induced martensite and nanotwins by cryogenic Laser Shock Peening of aisi 304 stainless steel and the effects on mechanical properties
Philosophical Magazine, 2012Co-Authors: Chang Ye, Sergey Suslov, Gary J. ChengAbstract:Laser Shock Peening (LSP) of stainless steel 304 was carried out at room and cryogenic temperature (liquid nitrogen temperature). It was found that the deformation-induced martensite was generated by LSP only when the Laser-generated plasma pressure is sufficiently high. Compared to room temperature Laser Shock Peening (RT-LSP), cryogenic Laser Shock Peening (CLSP) generates a higher volume fraction of martensite at the same Laser intensity. This is due to the increase in the density of potential embryos (deformation bands) for martensite nucleation by deformation at cryogenic temperature. In addition, CLSP generates a high density of deformation twins and stacking faults. After CLSP, an innovative microstructure, characterised by networks of deformation twins, stacking faults and composite structure (martensite and austenite phases), contributes to material strength and microstructure stability improvement. The combined effect of higher surface hardness and a more stabilised microstructure results in gre...
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fatigue performance improvement in aisi 4140 steel by dynamic strain aging and dynamic precipitation during warm Laser Shock Peening
Acta Materialia, 2011Co-Authors: Chang Ye, Eric A Stach, Sergey Suslov, Gary J. ChengAbstract:Warm Laser Shock Peening (WLSP) is a thermomechanical treatment technique combining the advantages of Laser Shock Peening and dynamic strain aging (DSA). Through DSA, WLSP of steel increases the dislocation density and stabilizes the dislocation structure by pinning of mobile dislocations by carbon atoms. In addition, WLSP generates nanoscale carbide precipitates through strain-induced precipitation. The carbide precipitates stabilize the microstructure by dislocation pinning. This results in higher stability of the dislocation structure and thus improves the stability of the compressive residual stress. In this study the mechanism of fatigue performance improvement in AISI 4140 steel by WLSP is investigated. It is found that microstructures formed after WLSP lead to a higher stability of dislocation structures and residual stress, which are beneficial for fatigue performance.
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Controlled nanocrystallization of NiTi shape memory alloy by Laser Shock Peening
Proceedings of the ASME 2011 International Manufacturing Science and Engineering Conference, 2011Co-Authors: Chang Ye, Gary J. ChengAbstract:In this paper, partial amorphization of NiTi alloys by Laser Shock Peening (LSP) is reported. The microstructure of NiTi after LSP was characterized by transmission electron microscopy (TEM). The amorphization mechanism was discussed in light of the high strain rate deformation characteristics of LSP. With subsequent controlled annealing after LSP, nanostructure with different grain size distribution was achieved. Copyright © 2010 by ASME.
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Nucleation of highly dense nanoscale precipitates based on warm Laser Shock Peening
Journal of Applied Physics, 2010Co-Authors: Yiliang Liao, Bong-joong Kim, Chang Ye, Eric A Stach, Sergey Suslov, Gary J. ChengAbstract:Warm Laser Shock Peening (WLSP) is an innovative thermomechanical processing technique, which combines the advantages of Laser Shock Peening (LSP) and dynamic aging (DA). It has been found that a unique microstructure with highly dense nanoscale precipitates surrounded by dense dislocation structures is generated by WLSP. In order to understand the nucleation mechanism of the highly dense precipitates during WLSP, aluminum alloy 6061 (AA6061) has been used by investigating the WLSP process with experiments and analytical modeling. An analytical model has been proposed to estimate the nucleation rate in metallic materials after WLSP. The effects of the processing temperature and high strain rate deformation on the activation energy of nucleation have been considered in this model. This model is based on the assumption that DA during WLSP can be assisted by the dense dislocation structures and warm temperature. The effects of the working temperature and dislocation density on the activation energy of precipitation have been investigated. This model is validated by a series of experiments and characterizations after WLSP. The relationships between the processing conditions, the nucleation density of precipitates and the defect density have been investigated.
A. H. Clauer - One of the best experts on this subject based on the ideXlab platform.
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Effect of power density and pulse repetition on Laser Shock Peening of Ti-6Al-4V
Journal of Materials Engineering and Performance, 2000Co-Authors: P. R. Smith, M. J. Shepard, P. S. Prevéy, A. H. ClauerAbstract:Laser Shock Peening (LSP) was applied to Ti-6Al-4V (wt. %) simulated airfoil specimens using a Nd:Glass Laser. Laser Shock Peening processing parameters examined in the present study included power density (5.5, 7, and 9 GW/cm^2) and number of Laser pulses per spot (one and three pulses/spot). The LSP’d Ti-6Al-4V samples were examined using x-ray diffraction techniques to determine the residual stress distribution and percent cold work as a function of depth. It was found that the residual stress state and percent of cold work were relatively independent of LSP power density. However, the number of Laser pulses per spot had a significant effect on both residual stress and percent of cold work for a given power density level. In addition, there was a strong correlation between the magnitude of residual compressive stresses generated and the percent cold work measured.
Le D Saunier - One of the best experts on this subject based on the ideXlab platform.
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Laser Shock Peening of ti 17 titanium alloy influence of process parameters
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2012Co-Authors: C Cellard, Delphine Retraint, Manuel Francois, Emmanuelle Rouhaud, Le D SaunierAbstract:Abstract The influence of the process parameters of Laser Shock Peening was investigated on specimens made of an aeronautic titanium alloy: Ti–5Al–2Sn–2Zr–4Cr–4Mo (Ti-17). In order to quantify the effect of relevant process parameters, an experimental design was carried out. It is based on a full factorial design with four factors (Laser fluence, pulse duration, number of impacts and thickness of the sample) and two levels for each factor. The process is characterised with the following variables: the depth of the impacts, the roughness of the treated surface, the hardening of the material (itself evaluated with the hardness and X-ray diffraction peak width), the residual stresses left in the sample and the global curvature of the sample. It is found that all the parameters have an influence on the residual stresses and that Laser Shock Peening has no influence on roughness and low influence on work-hardening. The variables are then analysed in order to evaluate correlations. The increase in hardness is found to be essentially due to compressive residual stresses, cold work-hardening having only a small effect. In thin specimens, the stress redistribution due to self-equilibrium leads to tensile residual stresses at the treated surface and to large deformations of the specimens.
Ying Zhu - One of the best experts on this subject based on the ideXlab platform.
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Laser Shock Peening induced fatigue crack retardation in ti 17 titanium alloy
Materials Science and Engineering A-structural Materials Properties Microstructure and Processing, 2018Co-Authors: Rujian Sun, Wei Guo, Peng Peng, T Zhai, Zhigang Che, Chao Guo, Ying ZhuAbstract:Abstract Laser Shock Peening is an advanced surface treatment technique of great interest introducing beneficial compressive residual stress and further enhancing fatigue crack propagation resistance of metallic components. In this study, fatigue crack propagation and subsequent retardation of Ti-17 titanium alloy under Laser Shock Peening are presented. Varying degrees of fatigue crack retardation were observed after Peening with pulse energy of 20 J and 30 J. The fatigue life was increased up to 2.4 times that of the unpeened counterpart. The fatigue arrests were observed in the deceleration zone after Peening, showing different angles with the fatigue crack path as the Peening energy varied. The fatigue crack retardation mechanism based on the plastic zone size and crack propagation energy density drop at the crack tip was further discussed, and a crack tip energy density criterion was proposed to quantitatively understand the fatigue crack retardation.
