Application of boundary element method to 3-D problems of coupled thermoelasticity

This paper deals with a new boundary element method for analysis of the quasistatic problems in coupled thermoelasticity. Through some mathematical manipulation of the Navier equation in elasticity, the heat conduction equation is transformed into a simpler form, similar to the uncoupled-type equation with the modified thermal conductivity which shows the coupling effects. This procedure enables us to treat the coupled thermoelastic problems as an uncoupled one, A few examples are computed by the proposed BEM, and the results obtained are compared with the analytical ones available in the literature, whereby the accuracy and versatility of the proposed method are demonstrated.     

Some experimental findings in compression-after-impact (CAI) tests of CF/PEEK (APC-2) and conventional CF/epoxy flat plates

Compression-after-impact (CAI) tests have been conducted for quasi-isotropic thick plates with 48 plies by using the NASA method and on plates with 32 plies by using the SACMA method. Specimens are made of CF/PEEK (APC-2) and conventional CF/epoxy for the NASA plates and CF/epoxy for the SACMA plates. In the NASA CAI tests, the sequence of delamination buckling and its propagation is clearly revealed through various experimental techniques. One major technique is moiré topography, and the other is thermo-mechanical stress analysis with a high-accuracy infrared sensor. The arrest of delamination propagation just before catastrophic failure due to high fracture toughness is clearly captured by the moiré camera. This behavior provides good CAI values of CF/PEEK. The initial buckling properties of the delaminated region by the impact are then extensively discussed. Numerical predictions of initial buckling stress have been obtained by modelled geometry of the delaminated region simplified from its precise structure clarified by ultrasonic C-scanning. They agree fairly well with the experimental results. The in-plane stress distribution in the delaminated region before initial buckling is measured by an infrared stress graphic system. This compared favorably with finite element predictions. Two types of symmetric buckling modes with respect to the central plate surface, twin and single peak ones, are experimentally captured.     

Finite element simulation of the mechanics of flat contact pad fretting fatigue tests

An understanding into the macro kinetic and kinematic behaviour of fretted surfaces is provided. Making use of a modified version of a previously developed in‐house two‐dimensional elastic–plastic finite element analysis numerically simulates flat contact pad fretting fatigue tests. Basic macro mechanics concepts are adopted to idealise two bodies with rough contact surfaces and loaded at two different sites with arbitrary axial loading profiles. A time scale factor is devised to recognise the earliest candidate out of the events possibly accommodated at each loading increment. The present analysis utilises a relevant experimental set up developed in the Structural Integrity Research Institute of the University of Sheffield as an application. Computational results accurate to within 1.2% and corresponding to one contact pad span and six constant normal loads acting individually with four amplitudes of two sinusoidal axial load cycles are presented. The present computations include (1) the development of the global and local normal and tangential reactions and relative sliding displacement acting along the fretting surfaces and (2) contact pad deformation, generated stress fields and plasticity development within the neighbouring region of the fretted area.     

基于ANSYS的铸嘴流体耦合场三维有限元仿真分析

作者用大型有限元分析软件ANSYS对铸嘴内稳态层流铝熔体进行仿真分析。实现了三维建模。解决了三维热一流耦合求解的问题，得到铝流体的速度、压力及温度的分布图。分析了铸嘴出口速度和温度的分布规律及其对连续铸轧的影响。     

The determinants of heat-shock element-directed lacZ expression in Saccharomyces cerevisiae.

Heat-shock induction of heat-shock protein genes is due to a specific promoter element (the heat-shock element, HSE). This study used lacZ under HSE control (HSE-lacZ) to characterize HSE activity in Saccharomyces cerevisiae cells of different physiological states and differing genetic backgrounds. In batch fermentations HSE-lacZ induction by heat shock was maximal in exponential growth, and showed marked decline with the approach to stationary phase. Expression in the absence of heat shock was unaffected by growth phase, indicating that the growth-dependent expression of many yeast heat-shock genes uses promoter elements in addition to the HSE. Heat-induced expression was strongly influenced by the temperature at which cultures were grown. While basal, uninduced expression was constant during growth at different temperatures to 30 degrees C, induction by transfer to 39 degrees C was reduced by increases in growth temperature as low as 18-24 degrees C. Maximal HSE-lacZ induction (30- to 50-fold) was in cultures grown at low temperatures (18-24 degrees C), then heat shocked at 39 degrees C. Ethanol was a poor inducer. Mutations having little effect on HSE-lacZ expression included a respiratory petite; ubi4 (which inactivates the poly-ubiquitin gene); also ubc4 and ubc5 (which each inactivate one of the ubiquitin ligases involved in degradation of aberrant protein). pep4-3 increased both basal and induced beta-galactosidase about two-fold, probably because of slower turnover of this enzyme in pep4-3 strains.     

Coupling techniques in boundary-combined methods for solving elliptic problems with singularities

Three coupling strategies in matching the Ritz-Galerkin method and the finite element method are introduced for general elliptic equations, and useful numerical techniques are provided. Numerical experiments have been carried out for solving the typical, singular Motz problem, which shows that optimal convergence rates of numerical solutions can be achieved by using the combined methods and techniques provided in this paper.     

Numerical Simulation of Deforming Manufacture Process for Automobile Bevel Gear Blank

1 Introduction Rear axle bevel gearis a vital kind of annular accessory with high precision and hugeload availablefeatures ,andit is widely used as the differential drive in automobiles and tractor .In China ,the traditional manufactureapproach of producing the rear axle bevel gear blankis die forging,which not only requires a highinvestment ofproduct equipments , but also involves a low material utilization and great noise .In order to overcome thesedrawbacks , manyresearchers have done a gre…     

基于ANSYS的闩体刚强度有限元分析

闩体的刚度和强度必须满足设计要求。用有限元法对复杂结构件进行力学性能分析是非常有效的方法。采用ANSYS软件对闩体进行了刚度和强度分析,得出了有用的结论,可供相关设计借鉴。     

Multidisciplinary optimization of gas-quenching process

Distortion as a result of the quenching process is predominantly due to the thermal gradient and phase transformations within the component. Compared with traditional liquid quenching, the thermal boundary conditions during gas quenching are relatively simple to control. By adjusting the gas-quenching furnace pressure, the flow speed, or the spray nozzle configuration, the heat-transfer coefficients can be designed in terms of both the component geometry and the quenching time. The purpose of this research is to apply the optimization methodology to design the gas-quenching process. The design objective is to minimize the distortion caused by quenching. Constraints on the average surface hardness, and its distribution and residual stress are imposed. The heat-transfer coefficients are used as design variables. DEFORM-HT is used to predict material response during quenching. The response surface method is used to obtain the analytical models of the objective function and constraints in terms of the design variables. Once the response surfaces of the objective and constraints are obtained, they are used to search for the optimum heat-transfer coefficients. This process is then used instead of the finite-element analysis. A one-gear blank case study is used to demonstrate the optimization scheme.