Dong Ying Ju

Numerical modeling and simulation of carburized and nitrided quenching process

Abstract In order to study metallo-thermo-mechanical behavior during carburized and nitrided quenching, a numerical model when considering quantitative effects of diffused carbon and nitrogen gradients and kinetics of phase transformation is proposed. Coupled calculations of diffusion, phase transformation and stress/strain give the final distributions of carbon and nitrogen contents as well as residual stress and distortion. Within the numerical simulation method, the effects of both transformation and lattice expansion induced from carbon and nitrogen absorption are considered when calculating the evolution of the internal stress and strain. In order to verify the method of numerical simulation, the simulated distributions of carbon and nitrogen content and residual stress/strain of a cylinder during carburized and nitrided quenching are compared with the measured results.

Simulation of the thermo-mechanical behavior and residual stresses in the spray coating process

Abstract In order to be able to forecast the thermo-mechanical behavior and the residual stress in the spray coating process, a continuum mecromechanical model for describing the interaction involving temperature, the solidifying mode and, the stress/strain curve is developed in this paper. A set of coupled equations of the heat conduction, stress/strain and solidification is given by the metallo-thermo-mechanical theory. For this simulation, a numerical modeling based on the finite element method for calculating the heat conduction associated with solidification and the stresses at the interface between multi-layer materials is proposed. Here, the temperature field, the solidified state and the residual stresses of the spray coating process, including interfacial combinations between substrate and sprayed layer, are presented, and the validity of the calculated results is discussed in comparison with experimental X-ray results.

Thermal Flow Simulation on Twin Roll Casting Process for Thin Strip Production of Magnesium Alloy

Strip continuous casting by twin roll method is a rapidly solidifying process, which can directly produce thin strips,reduce energy consumption and product cost of various metal materials. However, the casting of magnesium alloys with large solidifying ranges lead to some problems such as surface and internal defect, variation of solidification finish point for Mg sheet. In this research, the process conditions for a twin roll caster are analyzed by thermal flow simulation. The effect of type and dimension of delivery nozzles on production of Mg alloy are studied. A proper match of the setback distance of thin nozzle and casting speed is studied by thermal flow simulation, based on the characteristics of Mg melt handling, flow dynamics control and solidification.

Simulation of thermo-mechanical behavior and interfacial stress of metal matrix composite under thermal shock process

Abstract In this paper, a computational method is presented which aims to simulate the occurrence and evolution of residual stresses during thermal shock process of metal matrix composites. Here, a set of coupled equations of the heat conduction, stress/strain and phase transformation of materials is given in the framework of metallo-thermo-mechanical theory. As an example, simulation of a thermal shock associated with heating process by CO 2 laser to Ti–Fe matrix reinforced unidrectionally by SiC fiber is engaged in this study. In results of this simulation, the microstructural behavior and residual stress on the interface of the fiber–matrix is evaluated, and the strength of the composites after the thermal shock is also predicted.

An XPS study on the chemical bond structure at the interface between SiOxNy and N doped polyethylene terephthalate

The super-thin silicon oxynitride (SiOxNy) films were deposited onto the N doped polyethylene terephthalate (PET) surface. Varying the N doping parameters, the different chemical bond structures were obtained at the interface between the SiOxNy film and the PET surface. X-ray photoelectron spectra results showed that at the initial stage of SiOxNy film growth, the C=N bonds could be broken and C-N-Si crosslink bonds could be formed at the interface of SiOxNy∕PET, which C=N bonds could be formed onto the PET surface during the N doping process. At these positions, the SiOxNy film could be crosslinked well onto the PET surface. Meanwhile, the doped N could crosslink the [SiO4] and [SiN4] tetrahedrons, which could easily form the dense layer structure at the initial stage of SiOxNy film growth, instead of the ring and∕or chain structures of [SiO4] tetrahedrons crosslinked by O. Finally, from the point of applying SiOxNy∕PET complex as the substrate, the present work reveals a simple way to crosslink them, as well as the crosslink model and physicochemical mechanism happened at the interface of complex.

Damping Property of Epoxy Matrix Composite Beams with Embedded Shape Memory Alloy Fibers

In this present paper, an epoxy matrix composite beam with embedded SMA fibers of TiNi alloy are applied to improve the damping capacity of a beam in free vibration. In particular, an experimental method to measure the damping capacity of a beam structure using current control is proposed here. In addition, an analytical model of frequency vibration of a composite beam based on thermo-metallo-mechanical behavior due to electric heating in the SMA fiber is also proposed. The analytical results are compared with obtained experimental frequency data. Calculated and measured results illustrate the effects of current on the damping and frequency values.

Development of Remote Control and Monitor System for Autonomous Mobile Robot Based on Virtural Cell Phone

A system with abilities of remote monitor and remote control based on BREWTM, a wireless application platform, is designed for an autonomous mobile robot (ROBO-E). The construction of network environment, real-time image transfer and autonomous and manual control program of the autonomous mobile robot of the remote wireless monitor and control system are presented by using Internet and cell phone network. This system is successfully implemented into LAN and a simulation network environment of the Japanese 3G cell phone. It is realized to monitor and operate the ROBO-E remotely and wirelessly by using a developed application through Internet.

Drug Delivery System Using Nano-Magnetic Fluid

Nano-size magnetic magnetide is considered important for various medical applications. Dynamic motion of the magnetic particle is investigated in two essential models from a theoretical point of view. One is a drag model of the magnetic particle in an artery. The second is a pull model towards the surface of artery. Threshold conditions of external variables are obtained by dimensional analysis. On the basis of all these results, it is concluded that the movement of magnetic fluids can be controlled by external magnetic fields in blood vessels.

Thermal Flow Simulation and Concave Type Slot Nozzle Design for Twin Roll Casting of Magnesium Alloy AZ31

Twin- roll casting of magnesium alloys is a rapidly solidifying process, which can directly produce thin strips from molten metal. In this paper, based on a pilot vertical type twin-roll caster, 3D models of twin-roll casting process were used for simulation of thermal flow and solidification on depending of casting speed, molten pool level and pouring temperature. The effect of side dams on thermal flow behavior was also considered. Based on the analyzed results, a proper concave slot nozzle was designed to compensate temperature variation across the width of strip. Comparing with parallel type slot nozzle, it can adjust temperature distribution along the roll width continuously by adopting proper concave curves, which is more flexible than rectification boards delivery system. Strips of magnesium alloy AZ31 were produced in the pilot caster with the concave slot nozzle. The experiments show that surface quality of as cast strip was improved by using the new type of nozzle.

Transformation Plasticity and the Effect on Quenching Process Simulation

Mechanism of transformation plasticity (TP) is discussed from continuum mechanics viewpoint, and derivation of TP law from the unified thermo-mechanical and transformation plasticity constitutive equation. Result of identified TP coefficient for a chromium steel (JIS SCr420) by use of multi-functional testing machine is introduced as one of the material data together with other data to the simulation of a quenching process by use of newly developed code COSMAP. The simulated distribution of temperature, phases and stress/distortion are compared with the experimentally measured values to verify the accuracy.