Papers by Author: Yong Jun Wang

Abstract: Shape memory alloy (SMA) is a new intelligent material and is used widely in various structures. But the constitutive model of SMA is so complex and particular that it is difficult to calculate by finite element software. In this paper, a special constitutive model of SMA is chose and the constitutive variables are discretized. Through the derivation, it is made possible that the constitutive relation of SMA is put into the UMAT (user-defined material mechanical behavior) subroutine in ABAQUS. So it is available to calculate the structure contained SMA by finite element method.

Abstract: Among the functional materials, the ecological environment material is a new kind of materials. The ecological environment materials used in water pollution control process can be used as catalyst, absorbents and catalyst carrier. The functional materials investigated in this study were γ-A1₂O₃, ceramisite pellet, γ-A1₂O₃ loaded with nano-TiO₂ and ferric hydroxide, respectively. The performance of these materials and the efficiency of organic pollutant removal in high voltage electric field with these materials in the reactor were studied.

Abstract: Some catalytic materials can be utilized in environment pollution treatment. The material of ceramisite can be used in dye wastewater treatment process with its good properties. When they were filled in the high voltage discharge reactor, the ceramsite pellets were polarized, and partial discharge could take place beside every pellet, which would promote methylene blue degeneration in the dye wastewater. And when the solution pH>ceramsite pHzpc, the ceramsite surface presented the electronegativity and the ceramsite could adsorb more methylene blue, and removal rate increased.

Abstract: In order to investigate the performance of shape memory alloy wire, two types of alloy wire were studied. The results showed that the phase transition temperature of the superelastic wire were: Ms and Mf were 21.18 °C and 7.08 °C; As and Af were 12.32 °C and 25.13 °C. The phase transition temperature of memory effect alloy wire were that Ms =- 11.85 °C, Mf =- 29.37 °C, As = 36.77 °C, Af = 43.35 °C. By the tensile test of the SMA wire, the stress - strain curves of the two kinds of alloy wire were obtained.

Abstract: Under the assumption that the artificial viscosity coefficient at the propagating crack tip is in inverse proportion to power law of the plastic strain rate, a rate-sensitive constitutive relationship is derived for perfect elastic-plastic material. With the adoption of the rate-sensitive constitutive relationship, it is asymptotically investigated the propagating tip fields of plane strain mode II. And the quasi-static equations are obtained separately governing the stress and strain fields at the crack-tip by means of Airy stress function. Numerical calculations of governing equations are carried out by double parameters shooting, with selections of appropriate values of each characteristic parameter by combinations of boundary, and the fully continuous stress-strain fields are obtained at the crack-tip. The analytical and computational results indicate that viscosity effect is an important factor in crack-tip fields.

Abstract: Under the assumption that the artificial viscosity coefficient at the propagating crack tip is in inverse proportion to power law of the plastic strain rate, a rate-sensitive constitutive relationship is derived for perfect elastic-plastic material. With the adoption of the rate-sensitive constitutive relationship, it is asymptotically investigated the propagating tip fields of plane strain mode I. And the quasi-static equations are obtained separately governing the stress and strain fields at the crack-tip by means of Airy stress function. Numerical calculations of governing equations are carried out by double parameters shooting, with selections of appropriate values of each characteristic parameter by combinations of boundary, and the fully continuous stress-strain fields are obtained at the crack-tip. The analytical and computational results indicate that viscosity effect is an important factor in crack-tip fields.

Abstract: There is a bright future for hard cutting technique because of good machining flexibility, high efficiency, no pollution. This paper presents effect rules of cutting parameters (cutting speed, feed, depth of cutting) on integrality of machined surface (surface roughness, surface hardness, surface hardened depth, residual stresses, surface texture) based on orthogonalization test. Optimal cutting parameters are selected according to these rules. Surface roughness (Ra) is up to 0.6µm in terms of selected optimal cutting parameters.