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Full-Text Articles in Mechanical Engineering

Preparation Of La0.8sr0.2ga0.83mg0.17o2.815 Powders By Microwave-Induced Poly(Vinyl Alcohol) Solution Polymerization, Yuling Zhai, Chang Ye, Feng Xia, Jianzhong Xiao, Lei Dai, Yifan Yang, Yongqian Wang Apr 2015

Preparation Of La0.8sr0.2ga0.83mg0.17o2.815 Powders By Microwave-Induced Poly(Vinyl Alcohol) Solution Polymerization, Yuling Zhai, Chang Ye, Feng Xia, Jianzhong Xiao, Lei Dai, Yifan Yang, Yongqian Wang

Dr. Chang Ye

A new and simple chemical route, named microwave-induced poly(vinyl alcohol) (PVA) solution polymerization, has been used to prepare fine, homogeneous and high-density pellets of purer La0.8Sr0.2Ga0.83Mg0.17O2.815 (denoted as LS0.2GM0.17). The effect of different contents of PVA as the polymeric carrier, was studied and we obtained an optimal amount of PVA (1.65:1 ratio of positively charged valences of the cations (Men+) to negatively charged hydroxyl (–OH−) groups of the organics), which could ensure homogenous distribution of the metal ions in the polymeric network structure and inhibit segregation. The behavior of the ...


Cryogenic Ultrahigh Strain Rate Deformation Induced Hybrid Nanotwinned Microstructure For High Strength And High Ductility, Chang Ye, Sergey Suslov, Dong Lin, Yiliang Liao, Gary Cheng Apr 2015

Cryogenic Ultrahigh Strain Rate Deformation Induced Hybrid Nanotwinned Microstructure For High Strength And High Ductility, Chang Ye, Sergey Suslov, Dong Lin, Yiliang Liao, Gary Cheng

Dr. Chang Ye

Nanocrystalline metallic materials prepared by severe plastic deformation often possess high strength but low ductility due to the low dislocation accumulation capacity of the nanograins. Here, we report a unique process, namely, cryogenic laser shock peening (CLSP), to generate gradient nanotwinned microstructure that leads to high strength while preserving the ductility. It was observed that gradient structure was generated in copper. Near the top surface, nanocrystalline with high dense nanotwins have been observed; with the depth increasing, the fraction of the twin boundaries reduces and more heavily dislocated subgrains are observed. It has been demonstrated that CLSP can significantly improve ...


Large Scale, Highly Dense Nanoholes On Metal Surfaces By Underwater Laser Assisted Hydrogen Etching Near Nanocrystalline Boundary, Dong Lin, Martin Zhang, Chang Ye, Zhikun Liu, C. Liu, Gary Cheng Apr 2015

Large Scale, Highly Dense Nanoholes On Metal Surfaces By Underwater Laser Assisted Hydrogen Etching Near Nanocrystalline Boundary, Dong Lin, Martin Zhang, Chang Ye, Zhikun Liu, C. Liu, Gary Cheng

Dr. Chang Ye

A new method to generate large scale and highly dense nanoholes is presented in this paper. By the pulsed laser irradiation under water, the hydrogen etching is introduced to form high density nanoholes on the surfaces of AISI 4140 steel and Ti. In order to achieve higher nanohole density, laser shock peening (LSP) followed by recrystallization is used for grain refinement. It is found that the nanohole density does not increase until recrystallization of the substructures after laser shock peening. The mechanism of nanohole generation is studied in detail. This method can be also applied to generate nanoholes on other ...


Deformation Induced Martensite In Niti And Its Shape Memory Effects Generated By Low Temperature Laser Shock Peening, Yiliang Liao, Chang Ye, Dong Lin, Sergey Suslov, Gary Cheng Apr 2015

Deformation Induced Martensite In Niti And Its Shape Memory Effects Generated By Low Temperature Laser Shock Peening, Yiliang Liao, Chang Ye, Dong Lin, Sergey Suslov, Gary Cheng

Dr. Chang Ye

In this study, laser shock peening (LSP) was utilized to generate localized deformation induced martensite (DIM) in NiTi shape memory alloy. The DIM was investigated by x-ray diffraction and transmission electron microscopy. The effects of temperature and laser intensity on DIM transformation were investigated. It has been found that higher laser intensity and lower processing temperature leads to higher volume fraction of DIM. This is attributed to the increase of the chemical driving force and the increase in the density of potential martensite variant for martensite nucleation at low temperatures. The localized shape memory effect in micrometer scale after low ...


Gradient Nanostructure And Residual Stresses Induced By Ultrasonic Nano-Crystal Surface Modification In 304 Austenitic Stainless Steel For High Strength And High Ductility, Chang Ye, Abhishek Telang, Amrinder Gill, Sergey Suslov, Yaakov Idell, Kai Zweiacker, Jorg Wiezorek, Zhong Zhou, Dong Qian, Seetha Mannava, Vijay Vasudevan Apr 2015

Gradient Nanostructure And Residual Stresses Induced By Ultrasonic Nano-Crystal Surface Modification In 304 Austenitic Stainless Steel For High Strength And High Ductility, Chang Ye, Abhishek Telang, Amrinder Gill, Sergey Suslov, Yaakov Idell, Kai Zweiacker, Jorg Wiezorek, Zhong Zhou, Dong Qian, Seetha Mannava, Vijay Vasudevan

Dr. Chang Ye

In this study, the effects of Ultrasonic Nano-crystal Surface Modification (UNSM) on residual stresses, microstructure changes and mechanical properties of austenitic stainless steel 304 were investigated. The dynamic impacts induced by UNSM leads to surface nanocrystallization, martensite formation, and the generation of high magnitude of surface compressive residual stresses (−1400 MPa) and hardening. Highly dense deformation twins were generated in material subsurface to a depth of 100 µm. These deformation twins significantly improve material work-hardening capacity by acting both as dislocation blockers and dislocation emission sources. Furthermore, the gradually changing martensite volume fraction ensures strong interfacial strength between the ductile ...


Controlled Nanocrystallization Of Niti Shape Memory Alloy By Laser Shock Peening, Chang Ye, Gary Cheng Apr 2015

Controlled Nanocrystallization Of Niti Shape Memory Alloy By Laser Shock Peening, Chang Ye, Gary Cheng

Dr. Chang Ye

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.


Microstructure And Mechanical Properties Of Copper Subjected To Cryogenic Laser Shock Peening, Chang Ye, Sergey Suslov, Dong Lin, Yiliang Liao, Xueling Fei, Gary Cheng Apr 2015

Microstructure And Mechanical Properties Of Copper Subjected To Cryogenic Laser Shock Peening, Chang Ye, Sergey Suslov, Dong Lin, Yiliang Liao, Xueling Fei, Gary Cheng

Dr. Chang Ye

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 ...


A Microwave-Induced Solution-Polymerization Synthesis Of Doped Lagao3 Powders, Yuling Zhai, Chang Ye, Jianzhong Xiao, Lei Dai Apr 2015

A Microwave-Induced Solution-Polymerization Synthesis Of Doped Lagao3 Powders, Yuling Zhai, Chang Ye, Jianzhong Xiao, Lei Dai

Dr. Chang Ye

A new method, called the microwave-induced solution-polymerization synthesis (denoted as MW), and the conventional Pechini (denoted as PH) method have been used to prepare powders of La0.8Sr0.2Ga0.83Mg0.17O2.815 (denoted as LS0.2GM0.17) and La0.8Sr0.2(Ga0.9Co0.1)0.83Mg0.17O2.815(denoted as LS0.2GCM0.17). A higher heating rate and a more homogenous heating manner without thermal gradients in the microwave oven resulted in a pure LSGCM powder after calcination at 1400 °C for 9 hours (h) and purer LSGM (6.2% secondary phases). The grain size of the pellets of the ...


Bimodal Nanocrystallization Of Niti Shape Memory Alloy By Laser Shock Peening And Post-Deformation Annealing, Chang Ye, Sergey Suslov, Xueling Fei, Gary J. Cheng Apr 2015

Bimodal Nanocrystallization Of Niti Shape Memory Alloy By Laser Shock Peening And Post-Deformation Annealing, Chang Ye, Sergey Suslov, Xueling Fei, Gary J. Cheng

Dr. Chang Ye

In this paper, surface nanocrystallization of NiTi intermetallic alloy by a novel method is reported. The NiTi alloy is processed by laser shock peening (LSP) and controlled annealing. The microstructure of the NiTi alloy after processing is characterized by transmission electron microscopy. At the top surface of the material, a nanostructure with bimodal grains is obtained. The mechanism of the formation of the bimodal microstructure is discussed. At the material subsurface, deformation twins are generated by LSP and retained after controlled annealing. Tensile test results showed that both strength and ductility are significantly improved through LSP and controlled annealing.


Fatigue Performance Improvement By Dynamic Strain Aging And Dynamic Precipitation In Warm Laser Shock Peening Of Aisi 4140 Steel, Chang Ye, Gary Cheng Apr 2015

Fatigue Performance Improvement By Dynamic Strain Aging And Dynamic Precipitation In Warm Laser Shock Peening Of Aisi 4140 Steel, Chang Ye, Gary Cheng

Dr. Chang Ye

Warm laser shock peening (WLSP) integrates the advantages of laser shock peening and thermal-mechanical treatment (TMT) to improve material fatigue performance. Compared to traditional laser shock peening (LSP), warm laser shock peening, i.e. LSP at elevated temperature, leads to better performance in many aspects. WLSP can induce nanoscale precipitations by dynamic precipitation and high density dislocation by dynamic strain aging (DSA), resulting in higher surface strength, which is beneficial for fatigue life improvement. Due to pinning of dislocation structure by nanoscale precipitates, and the pinning of dislocation structure by Cottrell atmosphere, or the DSA effect, stability of the dislocation ...


Nucleation Of Highly Dense Nanoscale Precipitates Based On An Innovative Process: Warm Laser Shock Peening, Yiliang Liao, Chang Ye, Gary Cheng Apr 2015

Nucleation Of Highly Dense Nanoscale Precipitates Based On An Innovative Process: Warm Laser Shock Peening, Yiliang Liao, Chang Ye, Gary Cheng

Dr. Chang Ye

Warm laser shock peening (WLSP) is an innovative thermo-mechanical 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 ...


Fatigue Performance Improvement In Aisi 4140 Steel By Dynamic Strain Aging And Dynamic Precipitation During Warm Laser Shock Peening, Chang Ye, Sergey Suslov, Bong Kim, Eric Stach, Gary Cheng Apr 2015

Fatigue Performance Improvement In Aisi 4140 Steel By Dynamic Strain Aging And Dynamic Precipitation During Warm Laser Shock Peening, Chang Ye, Sergey Suslov, Bong Kim, Eric Stach, Gary Cheng

Dr. Chang Ye

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 ...


Experiment, Thermal Simulation, And Characterizations On Transmission Laser Coating Of Hydroxyapatite On Metal Implant, Gary Cheng, Chang Ye Apr 2015

Experiment, Thermal Simulation, And Characterizations On Transmission Laser Coating Of Hydroxyapatite On Metal Implant, Gary Cheng, Chang Ye

Dr. Chang Ye

Coating of bioceramic material, Hydroxyapatite (HAp), on metal implant has attracted many attentions in biomedical industry recently because its combination of good mechanical property and biocompatibility. However, most of current HAp coatings lack coating/substrate interfacial strength, and/or biocompatibility. The cell-tissue attachment is affected by the degraded biocompatibility due to decomposition of HAp during high temperature processing. In this article, an innovative method, transmission laser coating (TLC), is investigated to coat HAp on Ti substrate with low temperature processing. This process enhances the HAp/Metal interfacial property of current coatings, while maintaining good biocompatibility. Experiments are conducted using a ...


Comparison Of The Release Behaviors Of Cupric Ions From Metallic Copper And A Novel Composite In Simulated Body Fluid, Juan Li, Jinping Suo, Xunbin Huang, Chang Ye, Xiwang Wu Apr 2015

Comparison Of The Release Behaviors Of Cupric Ions From Metallic Copper And A Novel Composite In Simulated Body Fluid, Juan Li, Jinping Suo, Xunbin Huang, Chang Ye, Xiwang Wu

Dr. Chang Ye

The copper-containing intrauterine devices (Cu-IUDs) are being increasingly used worldwide as an effective contraceptive for family planning. To avoid abnormal bleeding, pain, and partial and complete expulsion which are associated with the burst release of copper during the first few days, a novel crosslinked composite based on poly(vinyl alcohol) that contained cupric ions, but not metallic copper, was synthesized. It is hypothesized that the burst release of cupric ions could be avoided and the utility of the cupric ions could be improved by this novel composite. To evaluate these effects of the composite, the corrosion products and the release ...


Laser Assisted Embedding Of Nanoparticles Into Metallic Materials, Dong Lin, Sergey Suslov, Chang Ye, Yiliang Liao, C. Liu, Gary Cheng Apr 2015

Laser Assisted Embedding Of Nanoparticles Into Metallic Materials, Dong Lin, Sergey Suslov, Chang Ye, Yiliang Liao, C. Liu, Gary Cheng

Dr. Chang Ye

This paper reports a methodology of half-embedding nanoparticles into metallic materials. Transparent and opaque nanoparticles are chosen to demonstrate the process of laser assisted nanoparticle embedding. Dip coating method is used to coat transparent or opaque nanoparticle on the surface of metallic material. Nanoparticles are embedded into substrate by laser irradiation. In this study, the mechanism and process of nanoparticle embedding are investigated. It is found both transparent and opaque nanoparticles embedding are with high densities and good uniformities.


Effects Of Ultrasonic Nano-Crystal Surface Modification On The Microstructure And Properties Of 304 Austenitic Stainless Steel, Chang Ye, Abhishek Telang, Amrinder Gill, Sergey Suslov, Zhong Zhou, Dong Qian, Seetha Mannava, Vijay Vasudevan Apr 2015

Effects Of Ultrasonic Nano-Crystal Surface Modification On The Microstructure And Properties Of 304 Austenitic Stainless Steel, Chang Ye, Abhishek Telang, Amrinder Gill, Sergey Suslov, Zhong Zhou, Dong Qian, Seetha Mannava, Vijay Vasudevan

Dr. Chang Ye

In this study, the effects of Ultrasonic Nano-crystal Surface Modification (UNSM) on the microstructure changes and the mechanical properties of austenitic stainless steel 304 were studied. Due to the dynamic impacts induced by the multiple strikes during UNSM, surface nanocrystallization and transformation to martensite has been achieved. The work-hardened surface layers (3.5 times the original hardness) lead to significant improvement in the mechanical properties as measured by nano-indentation and tensile test. The results demonstrate that UNSM is a powerful surface processing technique that can improve component mechanical properties and performance.


Synthesis And Characterization Of Sr-And Mg-Doped Lagao_3 Powders By Polyvinylpyrrolidone Microwave-Induced Solution Polymerization, Chang Ye, Yuling Zhai, Jian-Zhong Xiao Apr 2015

Synthesis And Characterization Of Sr-And Mg-Doped Lagao_3 Powders By Polyvinylpyrrolidone Microwave-Induced Solution Polymerization, Chang Ye, Yuling Zhai, Jian-Zhong Xiao

Dr. Chang Ye

A new chemical route,named microwave-induced polyvinylpyrrolidone(PVP) solution polymerization,has been used to prepare La0.8Sr0.2Ga0.83Mg0.17O2.815(denoted as LS0.2GM0.17) powder.The effect of different contents of PVP as the polymeric carrier was studied and we obtained the optimum amount of PVP,which could ensure the homogenous distribution of the metal ions in its polymeric network structure and inhibit their segregation from the solution.The behavior of the powder after calcination at different temperatures was studied.The PVP solution process consumed less organics compared with traditional Pechini process.Consequently,PVP was a more effective ...


Dislocation Pinning Effects Induced By Nano-Precipitates During Warm Laser Shock Peening: Dislocation Dynamic Simulation And Experiments, Yiliang Liao, Chang Ye, Huang Gao, Bong Kim, Sergey Suslov, Eric Stach, Gary Cheng Apr 2015

Dislocation Pinning Effects Induced By Nano-Precipitates During Warm Laser Shock Peening: Dislocation Dynamic Simulation And Experiments, Yiliang Liao, Chang Ye, Huang Gao, Bong Kim, Sergey Suslov, Eric Stach, Gary Cheng

Dr. Chang Ye

Warm laser shock peening (WLSP) is a new high strain rate surface strengthening process that has been demonstrated to significantly improve the fatigue performance of metallic components. This improvement is mainly due to the interaction of dislocations with highly dense nanoscale precipitates, which are generated by dynamic precipitation during the WLSP process. In this paper, the dislocation pinning effects induced by the nanoscale precipitates during WLSP are systematically studied. Aluminum alloy 6061 and AISI 4140 steel are selected as the materials with which to conduct WLSP experiments. Multiscale discrete dislocation dynamics (MDDD) simulation is conducted in order to investigate the ...


Mechanism Of Fatigue Performance Enhancement In A Superhard Nanoparticles Integrated Nanocomposites By A Hybrid Manufacturing Technique, Dong Lin, Chang Ye, Yiliang Liao, C. Liu, Gary Cheng Apr 2015

Mechanism Of Fatigue Performance Enhancement In A Superhard Nanoparticles Integrated Nanocomposites By A Hybrid Manufacturing Technique, Dong Lin, Chang Ye, Yiliang Liao, C. Liu, Gary Cheng

Dr. Chang Ye

A hybrid manufacturing process, which contains Laser Sintering (LS) and Laser shock peening (LSP), is introduced to generate iron-TiN nanoparticle nanocomposites. It is a two-step process including LS followed with LSP. Before LS, TiN nanoparticles mixed with iron powders are coated on samples surface. After LS, TiN nanoparticles are embedded into iron matrix to strengthen materials. Then LSP is performed to introduce work hardening and compressive residual stress. The existed nanoparticles increase the dislocation density and also help to pin the dislocation movement. Better residual stress stability under thermal annealing can be obtained by better dislocation movement stabilization, which is ...


Numerical Simulation On Nanoparticles Integrated Laser Shock Peening Of Aluminum Alloy, Chang Ye, Gary Cheng Apr 2015

Numerical Simulation On Nanoparticles Integrated Laser Shock Peening Of Aluminum Alloy, Chang Ye, Gary Cheng

Dr. Chang Ye

In this paper, numerical simulation of nanoparticle integrated laser shock peening of aluminum alloys was carried out. A “tied constraint” was used to connect the matrix and nanoparticle assembly in ABAQUS package. Different particle size and particle volumes fraction (PVF) were studied. It was found that there is significant stress concentration around the nanoparticles. The existence of nanoparticle will influence the stress wave propagation and thus the final stress and strain state of the material after LSP. In addition, particle size, PVF and particle orientation all influence the strain rate, static residual stress, static plastic strain and energy absorption during ...


Deformation Behaviors And Critical Parameters In Microscale Laser Dynamic Forming, Huang Gao, Chang Ye, Gary Cheng Apr 2015

Deformation Behaviors And Critical Parameters In Microscale Laser Dynamic Forming, Huang Gao, Chang Ye, Gary Cheng

Dr. Chang Ye

Microscale laser dynamic forming (μLDF) is a novel microfabrication technique to introduce complex 3D profiles in thin films. This process utilizes pulse laser to generate plasma to induce shockwave pressure into the thin film, which is placed above a microsized mold. The strain rate in μLDF reaches 106–107 S−1. Under these ultrahigh strain rates in microscale, deformation behaviors of materials are very complicated and almost impossible to be measured in situ experimentally. In this paper, a finite element method model is built to simulate the μLDF process. An improved Johnson–Cook model was used to calculate the flow ...


An Extended Finite Element Method (Xfem) Study On The Effect Of Reinforcing Particles On The Crack Propagation Behavior In A Metal–Matrix Composite, Chang Ye, Jay Shi, Gary Cheng Apr 2015

An Extended Finite Element Method (Xfem) Study On The Effect Of Reinforcing Particles On The Crack Propagation Behavior In A Metal–Matrix Composite, Chang Ye, Jay Shi, Gary Cheng

Dr. Chang Ye

In this paper, the eXtended Finite Element Method (XFEM) was integrated in ABAQUS to simulate crack propagation and to predict the effect of reinforcing particles to the crack propagation behavior of Al2O3/Al6061 composite materials. It has been demonstrated that, higher reinforcing particle volume fraction leads to improved fatigue resistance and smaller particles size is more effective than larger particles at the same particle volume fraction. The underlying mechanisms of these effects are systematically investigated. The stress fields captured by XFEM during the crack propagation help in understanding the crack propagation behavior during cyclic loading.


Ultrahigh Dense And Gradient Nano-Precipitates Generated By Warm Laser Shock Peening For Combination Of High Strength And Ductility, Chang Ye, Yiliang Liao, Sergey Suslov, Dong Lin, Gary Cheng Apr 2015

Ultrahigh Dense And Gradient Nano-Precipitates Generated By Warm Laser Shock Peening For Combination Of High Strength And Ductility, Chang Ye, Yiliang Liao, Sergey Suslov, Dong Lin, Gary Cheng

Dr. Chang Ye

Nanocrystalline materials generated by severe plastic deformation often come with high strength but low ductility due to the inability to accumulate dislocations and thus the low work hardening rate. In this study, a unique high strain rate deformation process – warm laser shock peening (WLSP) – is studied to generate extremely high-density nano-precipitates in precipitation hardenable alloy. Aluminum alloy (AA) 7075 was selected to evaluate the generation of ultra-high-density precipitates by WLSP and the effects on the strength and ductility. WLSP integrates the advantages of laser shock peening (LSP), dynamic strain aging (DSA) and dynamic precipitation (DP). The nanoscale precipitate particles generated ...


Effects Of Temperature On Laser Shock Induced Plastic Deformation: The Case Of Copper, Chang Ye, Gary Cheng Apr 2015

Effects Of Temperature On Laser Shock Induced Plastic Deformation: The Case Of Copper, Chang Ye, Gary Cheng

Dr. Chang Ye

Laser shock induced plastic deformation has been used widely, such as laser shock peening (LSP), laser dynamic forming (LDF), and laser peen forming. These processes have been extensively studied both numerically and experimentally at room temperature. Recently, it is found that at elevated temperature, laser shock induced plastic deformation can generate better formability in LDF and enhanced mechanical properties in LSP. For example, warm laser shock peening leads to improved residual stress stability and better fatigue performance in aluminum alloys. There is a need to investigate the effects of elevated temperature on deformation behavior of metallic materials during shock induced ...


Laser Shock Peening Apparatuses And Methods, Gary Cheng, Yiliang Liao, Yingling Yang, Chang Ye Apr 2015

Laser Shock Peening Apparatuses And Methods, Gary Cheng, Yiliang Liao, Yingling Yang, Chang Ye

Dr. Chang Ye

Methods and apparatuses for processing materials to enhancing the material's surface strength, improving the material's cyclic and thermal stability of microstructures, and extend the material's fatigue performance. Embodiments include laser shock peening at material temperatures that are moderately elevated (from the material's perspective) above room temperature. Alternate embodiments include laser shock peening at very cold (cryogenic) material temperatures. Still further embodiments include laser shock peening while covering the surface of the material being processed with an active agent that interacts with the laser energy and enhances the pressure exerted on the surface.


Deformation-Induced Martensite And Nanotwins By Cryogenic Laser Shock Peening Of Aisi 304 Stainless Steel And The Effects On Mechanical Properties, Chang Ye, Sergey Suslov, Dong Lin, Gary Cheng Apr 2015

Deformation-Induced Martensite And Nanotwins By Cryogenic Laser Shock Peening Of Aisi 304 Stainless Steel And The Effects On Mechanical Properties, Chang Ye, Sergey Suslov, Dong Lin, Gary Cheng

Dr. Chang Ye

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 ...


Magnetic Field Effects On Laser Drilling, Chang Ye, Gary Cheng, Sha Tao, Benxin Wu Apr 2015

Magnetic Field Effects On Laser Drilling, Chang Ye, Gary Cheng, Sha Tao, Benxin Wu

Dr. Chang Ye

A magnetic field-assisted laser drilling process has been studied, where nanosecond laser ablation is performed under an external magnetic field. The study shows that the magnetic field-assisted laser drilling process produces deeper drilling depth and generates more confined plasma plume and relative less residual, as compared with laser drilling without magnetic field. This phenomenon has been rarely reported in the literature. The magnetic field effects on laser ablation have been analyzed analytically and a hypothesized explanation has been proposed based on the effect of the magnetic field on the plasma produced during laser ablation.


Numerical Investigation Of Temperature Field During Sintering Of Bioceramic Nanoparticles By Pulse Lasers, Chang Ye, Gary Cheng Apr 2015

Numerical Investigation Of Temperature Field During Sintering Of Bioceramic Nanoparticles By Pulse Lasers, Chang Ye, Gary Cheng

Dr. Chang Ye

Traditional numerical study of the temperature field of laser thermal processing is based on two assumptions: 1. heat source is a surface heat flux, and 2. uniform material properties. This method is not accurate when it comes to the laser sintering of nanoparticle integrated bioceramics coating with certain porosity. In this paper, Heat transfer (HT) model and electromagnetic (EM) model is coupled to investigate the temperature field of bioceramics nanoparticles. The heat source calculated from EM field is simultaneously input into the HT model to calculate the temperature field of the nanoparticle assembly. The interaction between the nanoparticles in the ...


Scalable Patterning On Shape Memory Alloy By Laser Shock Assisted Direct Imprinting, Chang Ye, Gary Cheng Apr 2015

Scalable Patterning On Shape Memory Alloy By Laser Shock Assisted Direct Imprinting, Chang Ye, Gary Cheng

Dr. Chang Ye

In this study, patterned microindents are generated on the surface of NiTi shape memory alloy by laser shock assisted direct imprinting (LSADI). During LSADI, the plasma pressure generated by the laser pulse punches the mask into the target material and thus generates patterned indents. It has been demonstrated that thermally controllable surface pattern can be generated on NiTi surface through LSADI. Compared to traditional imprinting techniques, LSADI does not require a sharp mold, nor does it involve any heating or etching process. More importantly, it can be used to pattern metals. It is scalable and can be potentially used in ...


Nucleation Of Highly Dense Nanoscale Precipitates Based On Warm Laser Shock Peening, Yiliang Liao, Chang Ye, Bong Kim, Sergey Suslov, Eric Stach, Gary Cheng Apr 2015

Nucleation Of Highly Dense Nanoscale Precipitates Based On Warm Laser Shock Peening, Yiliang Liao, Chang Ye, Bong Kim, Sergey Suslov, Eric Stach, Gary Cheng

Dr. Chang Ye

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 ...