Papers by Author: Zhi Ming Hao

Abstract: This paper provides a illustration of the micro vibration measurement as well as the major vibration source of precision equipment. According to propagation and attenuation law of vibration in the soil, this paper gives some methods of control vibration which used in practical projects. And it inntroduces the anti-micro vibration measures in the design of precision equipment.

Abstract: Compression experiments of spruce along axial, radial and tangential loading directions are implemented by INSTRON equipment. Mechanical properties of spruce along three directions are gained. Spruce microscopic cell failure modes under axial, radial and tangential compression condition are observed by scan electron microscope. Results show that failure modes of spruce are fiber buckling and wrinkle when loading direction is along the grain. When loading direction is along radial or tangential across to the grain, failure modes are wood fiber slippage and delamination. Theory analytic solution to single wood cell failure under different direction compression is done. The obtained expression shows that mean limit loading is relative to yield stress, cell structure dimension and wrinkle length for complete wrinkle cases.

Abstract: The curves of stress versus strain along spruce wood axial, radial and tangential directions are gained by static compression experiments. Moisture content and density of the spruce wood are 12.72% and 413 kg/m³ respectively. The results indicate that spruce compression process includes elastic, yield and compaction phases. Failure modes of spruce subjected to axial compression are fiber buckling and wrinkle. And failure modes under radial or tangential compression are wood fiber slippage and delamination. Axial compression yield strength is about nine times as that of radial and tangential compression. Radial and tangential compression yield strengths are almost equal. Energy absorption efficiency and ideality energy absorption efficiency of spruce along different loading directions are analyzed. And theory analytic solution to single wood cell buckling under axial compression is done. The obtained expression shows that the mean limit loading is relative to yield stress, cell structure dimension and wrinkle length for complete wrinkle cases.

Abstract: A three-phase constitutive model for TiNiNb shape memory alloys (SMAs) is proposed based on the fact that TiNiNb SMAs are dynamically composed of austenite, martensite and -Nb phases. In the considered ranges of stress and temperature, the behaviors of austenite, martensite and -Nb phases are assumed to be elastoplastic, and the behavior of an SMA is regarded as the dynamic combination of the individual behavior of each phase. Then a macroscopic constitutive description for TiNiNb SMAs is obtained by the conventional theory of plasticity, the theory of mixture, the theory of inclusion, and the description of phase transition by Tanaka. The method for determination of the material parameters is given. This constitutive model can describe the main characteristics of SMAs, such as ferrcelasticity, pseudoelasticity and shape memory effect.

Abstract: A three-phase constitutive model for TiNiNb shape memory alloys (SMAs) is proposed based on the fact that TiNiNb SMAs are dynamically composed of austenite, martensite and -Nb phases. In the considered ranges of stress and temperature, the behaviors of austenite, martensite and -Nb phases are assumed to be elastoplastic, and the behavior of an SMA is regarded as the dynamic combination of the individual behavior of each phase. Then a macroscopic constitutive description for TiNiNb SMAs is obtained by the conventional theory of plasticity, the theory of mixture, the theory of inclusion, and the description of phase transition by Tanaka. The method for determination of the material parameters is given. This constitutive model can describe the main characteristics of SMAs, such as ferrcelasticity, pseudoelasticity and shape memory effect.

Abstract: Precise simulation of the temperature distribution throughout welding process is basic for stress analysis. In this paper, numerical simulations and multi-factor regression were used to investigate how the three process parameters, laser power, spot radius and spot offset, influence the temperature distribution in Beryllium (Be) cylindrical shells. The experiments are designed by the compound response surface method. Based on numerical results, regression model are gained as an expression about laser power, laser spot radius and laser spot offset. Then the effects of these three parameters on temperature distribution were obtained. The results could provide guidelines for welding process of Be cylindrical shells.