碰撞引起的宇航设备冲击响应仿真分析

利用运动学、动力学原理、有限元等分析方法对宇航设备在碰撞过程中的碰撞速度、撞击力、静强度、动力学响应等进行了仿真分析,由于碰撞力无法直接测量,应用碰撞理论和简化假设处理,计算得到碰撞力的分布函数,通过应用有限元理论和通用有限元程序NASTRAN,建立了研究对象的有限元模型,计算得到结构力学响应并结合以往的环境试验结果,验证了局部应力过高导致次结构破坏的现象,得出了主结构内部无法检测部件的环境适应性结论。还将理论仿真结果与模拟试验测量结果进行了对比分析,计算结果与实测结果有较好的一致性。分析表明,利用运动学和碰撞的有关理论可以较好地模拟文中设备的碰撞过程,对于撞击力的分布服从半正弦分布的假设在工程实践中是可行的。计算结构频率耦合作用而产生的结构内部放大或衰减效应。     

基于有限元分析的洗衣机跌落冲击仿真及改进设计

基于有限元理论实现某型全自动洗衣机在跌落冲击载荷下的仿真分析和设计改进.首先运用CAD软件Unigraphics(UG)建立洗衣机运输包装件的初始设计模型,然后将实体模型导入有限元软件Abaqus建立有限元网格模型并进行跌落仿真分析.分析结果表明跌落过程中箱体部件会发生起皱变形缺陷,仿真预测结果与试验结果吻合良好.针对当前设计中存在的问题,对洗衣机进行了局部改进设计和重新分析验证.改进设计后的洗衣机整机强度得到了有效增强,满足了跌落试验要求.这种"基于仿真的设计方法"为家电产品开发提供了一种新的有效手段.     

某特种车空投着陆过程数值仿真分析与改进

在基于LS-DYNA的环境中对某特种车整车的空投着陆进行了数值仿真研究。根据该特种车空投着陆的实际要求和整车结构尺寸,采用有限元软件HyperMesh建立空投着陆特种车整车的有限元模型,调用LS-DYNA求解器进行求解,最后利用LS-PREPOSTD做后处理。通过数值仿真结果和试验数据的对比,验证了该整车有限元模型的有效性。根据数值仿真结果,分析了该特种车车架的受力情况,提出了一些相应的改进措施,从而为车架的实际优化提供了依据。     

液压成形同步冲孔工艺仿真分析及试验

对液压冲孔过程进行分析,介绍了液压成形同步冲孔的工艺原理,分析了不同类型液压冲孔的特点和应用范围。采用有限元分析方法,建立了液压冲孔仿真有限元模型,并对冲孔过程中应力分布和应变变化情况进行分析。在此基础上,进行液压冲孔工艺试验,把工艺试验结果与有限元分析结果进行比较。结果显示,液压冲孔仿真分析与工艺试验呈现相同的变化规律,仿真分析能够较好预测实际冲孔过程。     

长导体断裂无损检测及仿真技术的应用

阐述了长导体断裂无损检测的基本原理，并通过实验验证了此原理的可行性，对发射脉冲的宽度和幅值进行了分析，建立了长导体分布参数电路模型，用计算机仿真软件对断点位置的测试进行了模拟和仿真，仿真结果与实验结果有很好的一致性。     

医用泡罩包装容器热成型仿真及工艺参数优化

目的通过数值模拟技术,仿真某医用泡罩包装热成型容器在柱塞辅助热成型工艺过程中,不同时刻片材的厚度变化规律及分布情况,并验证有限元仿真模拟结果的可靠性。仿真拉伸头不同预拉伸深度下的热成型容器的壁厚分布情况,找出使壁厚分布更加均匀的最佳预拉伸深度值,以优化工艺参数。方法利用Solid Works软件建立了有限元模型,通过Ansys Polyflow软件仿真该医用泡罩包装容器的热成型工艺过程。并通过对实际热成型产品进行热成型实验,验证了有限元仿真模拟结果的可靠性。结果仿真值与实验值的相对误差约为2%,仿真结果与实际情况大体一致,仿真结果比较可靠。结论通过有限元仿真模拟得到该医用泡罩包装制品的最佳热成型预拉伸深度值为6.5 mm。     

阵列式脉冲远场涡流管道缺陷检测方法

针对采用单个枪测线圈在管道缺陷检测中存在的检测分辨力较低的问题,研究了管道缺陷定量检测中的阵列式脉冲远场涡流检测技术.利用有限元仿真的方法对阵列传感器结构进行了优化设计,并且分析了不同深度缺陷对感应电压信号的影响规律.最后通过实验对仿真结果进行了验证,实验结果表明本文设计的阵列传感器具有较高的检测精度和灵敏度,可以实现对管道缺陷的定量检测.     

考虑刚度非线性的某橡胶隔振试件随机振动试验仿真研究

通过建立振动台、夹具和橡胶隔振试件整体有限元模型，对橡胶隔振试件振动台随机振动试验进行了仿真研究。仿真过程发现薄壳结构和橡胶隔振器在几百赫兹以上中高频段响应存在严重的衰减现象。通过研究发现动刚度在中高频段的非线性特性是影响响应衰减的主要因素。结合真实试验结果，对薄壳结构和橡胶隔振器的中高频动刚度进行了修正，修正结果表明薄壳结构和橡胶隔振器动刚度随频率增加而增大，获得了其动刚度随频率的变化趋势曲线。修正后的仿真结果整个频段内与实验结果基本一致，解决了仿真过程中高频段响应衰减问题。     

重型燃气轮机支撑结构动刚度计算分析方法

采用有限元仿真计算和实验测试相结合研究手段,测试某重型燃气轮机支架动刚度,以形成较为完备计算燃机支架动刚度的有限元仿真流程和计算分析方法。三维模型和实验测试所用试验件按4:1进行缩比并建立模型、加工制作。采用锤击法进行测试,并以其结果对有限元仿真计算结果进行验证。经过对比验证发现两者所得到结果吻合较好。结果表明,基于实验测试燃气轮机支撑结构动刚度有限元仿真流程及分析计算方法是可行的,计算结果具有一定可靠性,对进行相关方面研究具有一定参考价值。     

楔形板带轧制过程跑偏计算模型及其仿真

 在轧制过程中,由于外扰而引起的板带跑偏现象不能被很好控制,其直接原因在于轧制过程中板带的跑偏量不能精确测量和计算,很难进行精确控制.根据楔形板带轧制过程的物理跑偏模型,建立楔形板带的跑偏计算模型,并利用有限元分析软件,依据现场轧制参数建立有限元轧制模型.仿真结果验证了所建立的计算模型的合理性和精确性.     

Numerical Solution of a Problem of Thermal Stresses of a Magnetothermoelastic Cylinder with Rotation by Finite-Difference Method

The present article deals with the investigation thermal stress of a magnetothermoelastic cylinder subjected to rotation, open or closed circuit, thermal and mechanical boundary conditions. The outer and inner surfaces of the cylinder are subjected to both mechanical and thermal boundary conditions. A The transient coupled thermoelasticity in an infinite cylinder with its base abruptly exposed to a heat flux of a decaying exponential function of time is devised solve by the finite-difference method. The fundamental equations’ system is solved by utilizing an implicit finite-difference method. This current method is a second-order accurate in time and space; it is also unconditionally stable. To illustrate the present model’s efficiency, we consider a suitable material and acquire the numerical solution of temperature, displacement components, and the components of stresses with time t and through the radial of an infinite cylinder. The results indicate that the effect of coupled thermoelasticity, magnetic field, and rotation on the temperature, stresses, and displacement is quite pronounced. In order to illustrate and verify the analytical developments, the numerical solution of partial differential equations, stress components, displacement components and temperature is carried out and computer simulated results are presented graphically. This study is helpful in the development of piezoelectric devices.     

Low-Contrast Thermal Resolution Test Targets: A New Approach

A new type of thermal resolution test target optimized to minimize the effects of lateral thermal gradients at low thermal contrast is described. This target consists of thin-film inconel heater strips over an etched silica substrate bonded to an aluminum heat sink. A simple, finite-difference model is used to study how variations in target construction and materials affect the generated thermal resolution test pattern. The construction, testing, and use of this type of target to extend the lower end of the contrast range of a conventional target are described.     

轻质复合材料高温隔热性能

设计了一套隔热材料高温(>1200℃)隔热效果的测试装置,可对隔热材料进行快速、低成本的有效测试和筛选.采用本装置在材料热面中心温度为1600℃±10℃时,考察了碳/酚醛复合材料和ZrO2纤维板材料背部升温历程,评价了2种材料的隔热性能,并采用有限差分法数值模拟了ZrO2纤维板材料背部升温历程,预测其有效导热系数.研究...     

Three-dimensional reconstruction of subsurface defects using finite-difference modeling on pulsed thermography

We develop a technique to analyze pulsed thermography videos in order to detect and reconstruct subsurface defects in homogeneous and layered objects. The technique is based on the analysis of the thermal response of an object to a heat pulse. This thermal response is compared to the predictions of a finite-difference model that is systematically and progressively adjusted to minimize a cost function. With this minimization process, we obtain a depth and a thickness function that allow us to determine the three-dimensional shape, size, depth, thickness, and location of internal defects. The detected defects are reliably reconstructed with graphics of easy interpretation.     

Numerical Modeling of Heat Flux in Fixed-Point Cells Due to the Hydrostatic-Head Effect

The article presents the numerical analysis of a particular thermal effect, which occurs during the calibration of standard platinum resistance thermometers in fixed-point cells. The temperature within the fixed-point cell varies linearly with the immersion depth due to the hydrostatic-head effect, so a quasi-linear temperature gradient in the vertical direction is inherently present. If there is a temperature gradient, a resulting heat flux will appear. This heat flux flows across the thermal conductivities, which change with depth, so the resulting temperature field is distorted. The key issue that is tackled in this article is the magnitude of these temperature deviations and their influence on the measurement accuracy. This effect should not be confused with the perturbing heat exchange toward the thermal enclosure and ambient. These are independent effects that are in real systems superimposed on each other. To get a better insight into this phenomenon, a numerical model based on a finite-difference method was developed. The model allows the simulation of the measurement of the thermometer immersion profile and of the use of different bushings, as two of the methods for assessing the thermal effects. The results of the modeling showed that there is an inherent difference between the temperature measured by the thermometer sensor and the temperature at the point of the phase transition, even if the immersion depth was infinite and there was no perturbing heat exchange toward the thermal enclosure and ambient. Nevertheless, in several cases the thermometer would still almost perfectly follow the immersion-profile curve. The only exception is near the bottom of the cell, where a small deviation from the immersion profile was observed. This is in agreement with previously presented experimental results, where this behavior was noticed, but never satisfactorily explained.     

Applications of three-dimensional finite-difference seismic modeling in oil field exploitation and simulation

Two-dimensional finite-difference seismic models are excited by a line-source which leads to incorrect amplitudes. Moreover, in a structurally complex environment with strong three-dimensional (3-D) features, the results obtained from such models are often incorrect and do not include any out-of-plane events. On the other hand, 3-D models based on the ray-theory approximation fail to provide vital information such as diffractions and interference patterns which can strongly influence the seismic expression associated with hydrocarbon reservoirs. We present the results of a study in which an approximate version of mapped surfaces was used to carry out a synthetic 3-D finite-difference survey. This followed the necessary adjustment of various horizons and it involved the calibration of synthetic sections by comparing them with the corresponding unmigrated real-data sections. The simulation of reservoir characteristics was accomplished in reference to two key seismic horizons used in the model.     

Convective heat transfer in conditions of a transient boundary layer at a cylinder in a transverse flow

A finite-difference method is proposed for solving the equations of the thermal boundary layer at a circular cylinder, and the results of calculating the heat transfer in transient flow conditions are presented.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 54, No. 5, pp. 709–714, May, 1988.     

考虑亚稳态影响的非绝热毛细管数学模型及数值计算

根据两相流动的均相流动模型，考虑亚稳态的影响，建立了非绝热毛细管的数学模型，在此基础上进行数值计算，并将结果与实验文献进行了比较。     

Optimisation of Ni–Ti shape memory alloy response time by transient heat transfer analysis

Nickel–Titanium (Ni–Ti) shape memory alloys (SMAs) are commonly applied in commercial actuator design due to the high associated fatigue and tensile strengths, low cost and high activation temperature. Consequently, Ni–Ti SMAs provide an opportunity for the development of novel electromechanical actuators. However, the cooling response time is typically of significantly larger duration than the associated heating response time. The applicability of SMA actuators would be significantly greater if the cooling response time was reduced to allow a symmetric, high speed activation profile. This work provides insight into the opportunities associated with enhancing thermal heat transfer efficiency to achieve this objective. An explicit model of the temperature of Ni–Ti SMA wire is developed to estimate the temperature–time profile during resistive heating. A finite-difference equation is developed to predict the associated temperature during cooling. These models are used to confirm that for a typical scenario, the cooling stage dominates the total response time, and that lagging with a highly conductive media can be used to dramatically reduce the cooling response time. The finite-difference equation is validated against steady state data, and extended to provide insight into the effects of SMA lagging, including the effects of periodic excitation on cooling rate and the minimum observed SMA temperature during a heating cycle. The outcomes of this work are generally applicable to any axisymmetric transient heat transfer optimisation problem.     

On vibration-convective flows in a Hele-Shaw cell

The influence of high-frequency horizontal vibrations on convective flow conditions in a Hele-Shaw cell located in a homogeneous gravitational field and heated from below has been studied theoretically and experimentally. The linear problem of stability of mechanical quasi-equilibrium in the case of model boundary conditions has been solved analytically. The supercritical conditions of vibrational convection have been investigated numerically by the finite-difference method. It has been shown that at small values of the thermal and vibration Rayleigh numbers in a fluid a state close to quasi-equilibrium is realized. The critical values of the thermal and vibration Rayleigh numbers at which a change of different stationary and nonstationary convective regimes takes place have been determined. A stability map of vibration-convective flows has been generated. Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 81, No. 4, pp. 712–720, July–August, 2008.