Applied Mechanics and Materials Vols. 138-139

Abstract: In this work, Compact-Tension (C(T)) specimens with transverse welds in the sample centre were designed. The residual stress distributions were measured parallel and perpendicular to the weld nugget. Fatigue crack growth (FCG) rates were measured in the lab air. It is shown that compressive residual stresses around notch have significant effect on FCG rates and the effect deceases with crack growing. FCG rate is lower in the nugget than in parent material. Effects of residual stress were studied with crack growing. The lower crack growth rate in nugget is believed to be linked in part to compressive residual stress, but also in part to a microstructure effect present when crack grows in the recrystallized nugget.

Abstract: Al-Li alloy 2198-T8 was used in the fuselage application. Integral fuselage panels were joined by double friction stir welds. Fatigue tests were conducted in the R=0.1. Notch was made between two welds. Residual stresses were measured and analyzed in the test samples with double welds. Cracks grew from the centre of two welds and across the two welds were observed, and crack growth rates were measured and compared with parent material. It is shown that crack growth rates are lower between double welds, and it is close to parent material after cross the two welds. The virtual crack closure technique (VCCT) method was used to calculate stress intensity factor from residual stress (K_res) in aim to explain the experimental findings.

Abstract: Based on the actual crane accident occurring in strange cases, the calculating process is that the reel bearing seat model based on ADAMS is established after hoisting wire rope is broken, which is used for the dynamic strength analysis on the damage of the gear box bed plate & reel fulcrum bearing of crane, and the calculating result of the dynamic model is used as the input item for the load calculation analysis. Metallographic analysis & mechanics service test are applied to material strength analysis. This is an effective method for the modeling analysis of complex crane accidents based on multi-body dynamics, which provides practical and theoretical support for the design and calculation of cranes.

Abstract: Engineering ceramic machining would bring out several kinds of surface damage owing to its hard and brittle nature. In this paper, a simulation model of single-grit grinding for silicon carbide (Sic) was established to explore the high-speed grinding mechanism. The material behavior was described with the Johnson-Holmquist Ⅱ (JH-2) model. According to the simulation experiment results, the optimal grinding parameters to achieve ductile grinding for Sic has been analyzed, which would provide theoretical basis and take surface damage under control.

Abstract: It is signality for the Yangtse River estuary fine sand filling the highway subgrade which accounting for the lacking of filler and protecting along the line environment. Experiment results indicate that the sand has high strength, low compressibility, and good water stability. But the fine sand has some characteristics as grain uniformity, badness gradation, single structure, and the fine grain, and the fine sand filling subgrade is built on the soft soil foundation with high water table, so it is hidden troubles for the fine sand filling subgrade extending and application whether it can liquefy under the tempestuous earthquake load. The paper establish the liquefaction condition, carry through the liquefaction experiments and analysis the subgrade liquefaction risk relying on the Chong Ming connection engineering of Changjiang tunnel and bridge engineering. The analysis results indicate that the yangtse river estrary fine sand cannot liquefy with 7 class earthquake load, and it has no liequefaction conditions. So the subgrade has low liquefaction risk, and can be widely application.

Abstract: The geometric parameters of the composite laminate in the engineering structure tend to have random properties. It is of great significance on how to study sensitivity of random parameters of laminated plates and carry on the optimized analysis to the parameteranalys when accurately estimating the reliability of structural design. According to the first order shear deformation theory, by using the spline finite element method, we can infer and the establish a laminated plate vibration equation, the stiffness matrix, mass matrix, proportional damping matrix, before making solution of the antisymmetric laminated plates response sensitivity formula, and analyzing the normal displacement, the sensitivity, the natural frequency of compound materials laminated plate. The Numerical examples verify the effectiveness of this algorithm.

Abstract: The double-mass silicon micro gyroscope prototype, mechanical structure and working principle are introduced, which has high sesitivity. According to dynamic equations, the signal characteristics are analyzed and the mathematical models of scale factro and bias are established. Then the system level model is established on Simulink platform, including mechanical errors and electrostatic coupling errors and the performance are evaluated. Finally, five gyroscope prototypes are tested, and the performance parameters are as follows, the scale factor is 15.63~19.210mV/°/s, bias stability is 8.9~23.9°/h, bias repeatability is 7.5~19.4°/h.

Abstract: In the machining of ultrasonic gear honing, gear’s dynamic characteristics have a significant impact on the designing of vibration system and machining quality of gear. Since the gear and solid horn produce resonance, it is necessary to give a comprehensive consideration of the interaction between the two. This paper utilized the boundary conditions of the plate and the horn at the connection surface and their own dynamical equations to establish dynamical model of composite structure of the gear and the horn, which providing a theoretical basis for the horn designing and the gear’s dynamic characteristics analysis in ultrasonic gear honing. The results of calculation example are consistent with that of test, it verifies that the proposed analytical method in this paper is feasible.

Abstract: Natural boundary integral method is applied to deal with plate problems defined in irregular domains. We divide the solution into two parts, a particular solution for inhomogeneous biharmonic equation and the general solution for homogeneous biharmonic equation. For the former, the direct expansion method of boundary conditions is used to treat the arbitrary domains, and the processes of natural boundary integral method coupling with finite element method are omitted. Numerical experiments show that the method is very simple and of high accuracy.

Abstract: In this paper, we combined the Fourier cosine series and differential quadrature method (DQM) in barycentric form to develop a new method (FCDQM), which is applied to the 1D fourth order beam problem and the 2D thin isotropic plate problems. Furthermore, we solved the complex boundary conditions on irregular domains with DQM directly. The numerical results illustrate the stability, validity and good accuracy of the method in treating this class of engineering problems.