Applied Mechanics and Materials Vols. 52-54

Abstract: Probabilistic analysis aims at providing an assessment of cracked structures and taking relevant uncertainties into account in a rational quantitative manner. The main focus of this research work is on uncertainties aspect which relates with the nature of crack in materials. By using cracked structures modelling, finite element calculation, generation of adaptive mesh, sampling of cracked structure including uncertainties factors and probabilistic analysis using Monte Carlo method, the rigidity of cracked structures is estimated. Assessment of the accuracy in probabilistic structures is essential when limited amount of data is available. The hybrid finite element and probabilistic analysis represents the failure probability of the structures. The probability of failure caused by uncertainties relates to loads and material properties of the structure are estimated using Monte Carlo simulation technique. Numerical examples are presented to show probabilistic analysis based on Monte Carlo simulation provides accurate estimates of failure probability. The comparison shows that the combination between finite element analysis and probabilistic analysis provides a simple and realistic of quantify the failure probability.

Abstract: Stresses distribution in crankshaft fillet region are mainly discussed in this paper. FEM is used for calculating the stresses. With the analysis of the regional stresses distribution, we concludes that the stresses can be fitted by first order of Fourier expansions, while all the parameters in the expansions can be expressed as second order polynomial expansions.

Abstract: Pretest analysis is a crucial step of the process for experimental modal analysis, directly affect the test accuracy. A general procedure for pretest analysis of a vehicle body frame has been presented using CAE approach with software Virtual Lab. After the modal parameters are acquired from FEM analysis, the CAE based MAC method is used to optimize the measurement location and direction. The selection of an appropriate set of measurement locations and directions including initial accelerometers placement and test excitation point location are defined based on MAC method by Virtual Lab correlation part. Finally, for purpose of validation, the FEM modal analysis is compared with operational modal analysis. The results comparison showing that the present pretest analysis approach is more accuracy and efficiency.

Abstract: Electromechanical coupling effect must be considered in the dynamic analysis of permanent magnet AC servo-driven precision gear transmission system. According to the global coupling and local coupling analysis in servo-driven system, the global electromechanical coupling relation diagram of whole system and the local electromechanical coupling relation diagram of the permanent magnet synchronous motor-precision gear transmission subsystem are established. For this subsystem, a physical model is built up. And a mathematical model is constituted by using Lagrange-Maxwell equation, that is the dynamic equation of the subsystem. The mathematical model can provide theoretical basis for follow-up researches.

Abstract: Part of work on CFD simulations by the high-lift system design team in Fudan university for large civil aircraft is presented. The research on CFD simulation of the high-lift systems and some concepts and experience in three-dimensional geometry modeling are also presented, which are done on the self-developed platform of high-lift device aerodynamic calculation software and programs. For which, the design efficiency is substantially improved.

Abstract: In this article, four observation points are selected in the flow field when predicting aerodynamic noise of a multi-element airfoil for both a coarser grid and a finer grid. Numerical simulation of N-S equations is employed to obtain near-field acoustic information, then far-field acoustic information is obtained through acoustic analogy theory combined with FW-H equation. Computation indicates: the codes calculate the flow field in good agreement with the experimental data; The finer the grid is, the more stable the calculated sound pressure level (SPL) is and the more regularly d(SPL)/d(St) varies.

Abstract: The objectives of this study were to determine the stress concentration of the lumbar vertebra and the probability of failure associated with finite element method. The lumbar vertebra model was constructed in SolidWorks software and imported by ANSYS software for the analysis. In this work, all the model components were meshed using the tetrahedral solid element (SOLID186). In order to simplify the model, all the spinal components were modeled as an isotropic and elastic material. Monte Carlo Simulation (MCS) technique was performed to conduct the probabilistic analysis using a built-in probabilistic module in ANSYS with attempt for 100 trials. The results were observed that the highest stress concentrations were found in the adjacent posterior vertebral body with 1.2117 MPa and the corresponding probability of failure for the model is 3%. Sensitivity analysis had been revealed that the force applied to the facet (FORFCT) variable was sensitive to the stress and displacement output parameters and need to be emphasized. The current probabilistic study was very useful as a tool to understand the inherent uncertainties and variations in biological structures.

Abstract: Typically a shallow foundation is chosen to support several types of common structure. Several equations for the ultimate bearing capacity of shallow foundation have been proposed with assumption of fully saturated or completely dry conditions. In fact, almost 40 percent of natural soils on the earth surface are in an unsaturated state. Therefore, the ultimate bearing capacity of shallow strip foundation on unsaturated granular soils is developed in this paper using limit equilibrium concept. The simulations from the developed equation for a laboratory-compacted-sand are performed. The results are carefully presented and discussed.

Abstract: TheCCT curves and dynamic phase diagrams of carbon steel have been established and discussed, the corresponding structures and chemical compositions are analyzed. The computer calculation programming of phase diagram and main computer program have been setted.

Abstract: Thermal design and analysis of a satellite borne FPGA is described in this paper. Thermal-conductive glue, vias and an aluminum bar were used to the FPGA and the PCB under the FPGA in order to help conduct the heat of the FPGA to heat sink. The results of finite element analysis showed that the case temperature of the FPGA decreased from 132.5°C to 55.4°C and the junction temperature decreased from 136.1°C to59.0 °C after the thermal design, which matches the requirements of thermal design.