Papers by Author: Shao Rong Yu

Abstract: The deterministic analytic stress formula of double-Layer pressure vessels is derived. The optimum radius ratio between the inner and outer layers is obtained under uniform safety margins. Based on that, the method for evaluating the fuzzy stress and strength reliability is presented and an application example is given. The investigation provides a reference for further studies of uncertain mechanical problems of multi-layer pressure vessels

Abstract: The sensitivity of blast pressure of a pressure vessel to the material strength, the effective welding depth and the relative radius is studied by finite element simulations and single-factor sensitivity analyses. And the sensitivity coefficients are obtained by normalization procession. Furthermore, a three-factor regression model is obtained by multi-factor numerical experiments. The investigation of this paper provides guidelines for further researches of relating problems.

Abstract: Presently, there are a significant number of investigations that study the influences of the hydrogen embrittlement on pressure vessels for hydrogen storage. But few of them consider the effects of helium-3 decayed from hydrogen. This paper studies the effects of the high-pressure hydrogen on mechanical behavior of a kind of steel pressure vessel by elastic-plastic finite element simulations, based on the explosion tests data of 4-, 6-, 14- and 17-year hydrogen storage vessels and relating experimental data of materials properties. Then the mechanical responses of the 50-year hydrogen storage pressure vessel are predicted. The results provide guidelines for design and evaluating hydrogen storage vessels.

Abstract: In this paper, the hyperelastic constitutive theory, the well-know hyperelastic models and the range of uses are introduced. Finite element simulations of the compression tests have been performed with the incompressible Mooney-Rivlin constitutive theory. The choices of parameters in the hyperelastic modeling, the element type, mesh technique and the contact stiffness in the simulation are discussed. The predicted simulation results agree well the experimental data.

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: The theoretical value of bolt pre-tightening torque coefficient is typically 0.2 on load boundary condition simulations.A set of measuring setup has been designed in present study.Through direct measurement and electric measurement,a torque coefficient of 0.15 has been measured.The effects of pre-tightening torque coefficient on bolt stress field are studied numerically.Results show that the coefficient has significant effect on bolt stress fields and relatively conservative results will be achieved if a theoretical value of 0.2 is chosen.Studies on stresses around hole-edge and comparisons with test values show that simulated results of and agree well with test data and the relative errors are no more than 15%.

Abstract: The design of a external sealing structures is of much importance for the miniaturization design of valve. The metal diaphragm structure is the main component of the external sealing structure. So the mechanical behaviors of the metal diaphragm are significantly necessary to be determined for the valve design. This paper, by numerical simulations, studies the mechanical behaviors of the diaphragm, including: i) the stresses and deformations of a three-layered metal diaphragm under the loads of axial force and high pressure, and ii) the effects of the diaphragm layer number on the axial force and the maximum equivalent stress under effective external sealing. These results provide guidelines for design and application of the valve and its diaphragm.

Abstract: Based on the nonlinear finite element analysis method, FEA models which describe the viscoelastic friction contact state of the polyurethane foam preloaded structures are created. In the simulations, the general Maxwell viscoelastic constitutive relation is introduced and a seven-parameter general Maxwell viscoelastic model is used to fit the experimental stress relaxation curve of polyurethane foam. During the nonlinear contact analysis, coulomb friction law is adopted, and the effects of the coulomb friction coefficient on the reaction force in the axial direction are analyzed. The FE results show that the change tendencies of relation curves of the structures are similar to which of the polyurethane foams. In the end, the influences of stiffness ratio of polyurethane foam to the outer component on the structural relaxed force are discussed, and the FE results indicate that the stiffness ratios affect the stress (force) relaxation degree remarkably. That is to say a good structure design could optimize the mechanical performance of the complicated structures greatly.

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.