Mechanical Engineering Commons^™

Release Behavior Of Copper Ion In A Novel Contraceptive Composite, Juan Li, Jinping Suo, Xunbin Huang, Chang Ye, Xiwang Wu

Dr. Chang Ye

Purpose

The universally used contraceptive method, the Cu-IUD, an effective contraceptive, is being increasingly used worldwide for family planning. To avoid abnormal bleeding, pain, partial and complete expulsion associated with the burst release of copper during the first few days, a novel cross-linked composite based on poly vinyl alcohol (PVA) that contains copper ions, but not metallic copper, was synthesized.

Material and Methods

PVA, well known for its good processability, high strength, long-term temperature and pH stability and biocompatibility, was used as the matrix material. The corrosion products and the release rate of copper ions after soaking in simulated body …

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

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 …

Laser Shock Peening Of Nanoparticles Integrated Alloys: Numerical Simulation And Experiments, Chang Ye, Gary Cheng

Dr. Chang Ye

Nanocomposite and multiphase structures have become more important nowadays to enhance the mechanical properties of materials. Laser shock peening (LSP) is one of the most efficient ways to increase component fatigue life. In this paper, numerical and experimental studies have been carried out to study the effects of nanoparticles integrated structures during the laser shock peening of aluminum alloys. The LSP experiment of aluminum samples with different particle densities was carried out. The effect of nanoparticle on shock wave propagation, plastic deformation, energy absorption, and residual stress magnitude was studied. A qualitative agreement is found between experiment and simulation. The …

Surface Form Memory In Niti Shape Memory Alloys By Laser Shock Indentation, Xueling Fei, David Grummon, Chang Ye, Gary Cheng, Yang-Tse Cheng

Dr. Chang Ye

An indentation-planarization method for NiTi shape memory alloys has been developed that produces a robust surface topographical memory effect that we call "surface form memory", orSFM. Surface form memory entails reversible transitions between one surface form (flat) and another (say, wavy) that occur on changing temperature. These transitions are cyclically stable and exhibit very high mechanical energy density. Our previous study has demonstrated SFM transitions in NiTi alloys derived from quasistatic (i.e., low strain rate) spherical indents, as well as other geometries. Here, we report on experiments using confined laser ablation to indent a similar martensitic NiTi substrate, but in …

Warm Laser Shock Peening Driven Nanostructures And Their Effects On Fatigue Performance In Aluminum Alloy 6160, Chang Ye, Yiliang Liao, Gary Cheng

Dr. Chang Ye

Warm laser shock peening is an innovative manufacturing process that integrates laser shock peening and dynamic aging to improve materials' fatigue performance. Compared to traditional laser shock peening (LSP), warm laser shock peening (WLSP) – i.e., LSP at elevated temperatures – provides better performance in many aspects. WLSP can induce nanoscale precipitation and high density dislocation arrangement, resulting in higher surface strength and lower surface roughness than LSP, which are both beneficial for fatigue life improvement. Due to pinning of the dislocation structure by nanoscale precipitates – so-called dislocation pinning effects – the relaxation of residual stress and surfaces dislocation …

Laser Engineered Multilayer Coating Of Biphasic Calcium Phosphate/Titanium Nanocomposite On Metal Substrates, Martin Zhang, Chang Ye, Uriel Erasuin, Toan Huynh, Chengzhi Cai, Gary Cheng

Dr. Chang Ye

In this work, laser coating of biphasic calcium phosphate/titanium (BCP/Ti) nanocomposite on Ti-6Al-4 V substrates was developed. A continuous wave neodymium-doped yttrium aluminium garnet (Nd:YAG) laser was used to form a robust multilayer of BCP/Ti nanocomposite starting from hydroxyapatite and titanium nanoparticles. In this process, low power coating is realized because of the strong laser−nanoparticle interaction and good sinterability of nanosized titanium. To guide the optimization of laser processing conditions for the coating process, a multiphysics model coupling electromagnetic module with heat transfer module was developed. This model was validated by laser coating experiments. Important features of the coated samples, …

The Mechanisms Of Thermal Engineered Laser Shock Peening For Enhanced Fatigue Performance, Yiliang Liao, Sergey Suslov, Chang Ye, Gary Cheng

Dr. Chang Ye

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 …

Nanoparticles Embedding Into Metallic Materials By Laser Direct Irradiation, Dong Lin, Chang Ye, Yiliang Liao, C. Liu, Gary Cheng

Dr. Chang Ye

We report a method to half-embed nanoparticles into metallic materials. Transparent and opaque nanoparticle (laser wavelength 1064 nm) were both successfully half-embedded (partial part of nanoparticles embedded into matrix while other parts still stay above the matrix) into metallic materials. Nanoparticles were coated on sample surface by dip coating before laser irradiation. After laser irradiation of different pulses and laser fluencies, nanoparticles were embedded into metal. The mechanism and process of embedding were investigated.

Mechanism Of Fatigue Performance Enhancement In A Laser Sintered Superhard Nanoparticles Reinforced Nanocomposite Followed By Laser Shock Peening, Dong Lin, Chang Ye, Yiliang Liao, Sergey Suslov, Richard Liu, Gary Cheng

Dr. Chang Ye

This study investigates the fundamental mechanism of fatigue performance enhancement during a novel hybrid manufacturing process, which combines laser sintering of superhard nanoparticlesintegrated nanocomposites and laser shock peening (LSP). Through laser sintering, TiNnanoparticles are integrated uniformly into iron matrix to form a nanocomposite layer near thesurface of AISI4140 steel. LSP is then performed on the nanocomposite layer to generate interaction between nanoparticles and shock waves. The fundamental mechanism of fatigue performance enhancement is discussed in this paper. During laser shock interaction with thenanocomposites, the existence of nanoparticles increases the dislocation density and also helps to pin the dislocation movement. As …

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 J. 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.