形状记忆可展桁架在轨热变形分析研究

本文借助I-DEAS软件建立了针对形状记忆可展桁架的热-结构耦合分析模型,并试验验证了分析模型的准确性。在此基础上,采用多层隔热复合材料作为热控措施,计算分析有/无热控措施及预紧力大小对桁架温度与热变形的影响。结果表明,包覆多层隔热材料效果明显,可将桁架在轨周期内的温度差减小85%,位移差减小80%,有利于对可展桁架进行温控,实现展开与收拢,减小运行期间振动的影响。桁架变形大小由预紧力和热应力共同决定,随着预紧力增大,桁架位移差逐渐减小。     

热送热装工艺中板坯出连铸机温度的分析

用连铸坯凝固过程传热模型模拟了热送热装工艺中不同工况下铸坯凝固壳厚度和铸坏出连铸机的温度变化。模拟结果与实测值吻合很好。影响铸坯出连铸机温度的主要因素是铸坯尺寸、连铸机拉速和冷却制度。     

热虹吸管温度波动原因分析

对热虹吸管进行了实验研究,分析了影响热虹吸管管壁温度波动的因素。同时基于两相流动及热力学的相关理论,分析了这些因素影响热虹吸管温度波动的内在机理,这一结果对于进一步研究热管内部的传热机理和指导生产具有一定的参考价值。     

火电厂热控仪表故障类型及检修分析

火电厂经营过程中涉及多种类型热控仪表装置的使用,但长期在火电厂环境下持续运作难免会出现死机、采样误差、设备失灵等故障,直接影响火电厂经济效益和运营情况。为做好电厂热控仪表故障排查,本文分别总结电磁流量表、压差流量表以及测温装置的故障问题,分析使用过程中如何对故障进行调节与恢复,根据实际故障情况选择最佳方式,为相关人员提供参考。     

大厚度树脂基复合材料的热风箱加热固化研究

为研究某通航飞机典型树脂基复合材料热风箱加热固化过程中的热应力,建立了包括流固耦合、树脂固化放热的多物理场动量、热量输运模型和热应力模型,并通过实验验证了计算模型和方法的正确性。数值计算了不同厚度的层合板热风箱加热固化过程中的热空气流场,温度场以及层合板热应力场,并与热补仪加热固化过程中的对应参数进行对比。数值计算结果表明：热风箱在层合板周围能形成较高且稳定的温度环境,随着厚度的增大,层合板内温度分布更加均匀,层合板内部的热应力降低,且在固化过程中的热应力波动幅度减小。研究结果还表明,热风箱加热固化的板内热应力值在整个固化过程中均明显低于热补仪加热固化的热应力值,在升温阶段低幅达6%,在降温阶段低幅达10%。对于本文所研究的大厚度树脂基复合材料,热风箱加热固化具有较明显的优势。     

月面着陆器遮阳伞辅助热控方法散热性能分析

针对月面着陆器的热环境特点,为了提高月面着陆器热排散系统的散热能力,增加月面着陆器任务驻留时间,提升着陆器的探测能力与可靠性,提出了一种遮阳伞辅助热控装置。结合月面热环境特点分析并建立了月面着陆器热控分析模型,并针对无遮阳伞、固定型遮阳伞以及可调节型遮阳伞这三类应用于月面着陆器的辅助热控装置散热性能进行仿真分析,获得不同情况下月面着陆器散热能力随太阳高度角的变化关系。研究结果显示有、无遮阳伞辅助热控装置,散热性能相差300%,并且可调节型遮阳伞辅助热控装置可满足月面着陆器整个任务周期内的散热性能要求。     

复合材料增强活塞机械变形与热变形分析

国内外十分重视复合材料强化活塞的技术开发,活塞的设计、强化技术和评价技术也取得了很大进展.本文利用计算机工作站对复合材料强化后的活塞进行机械变形、热变形有限元分析,探讨复合材料强化的方式与结构尺寸对变形影响的趋势.复合材料增强活塞技术已在几种车用发动机活塞上进行了推广应用,表明复合材料增强活塞结构设计合理,热疲劳强度和抗热应力、机械应力和变形的能力得到较大的改善,活塞工作能力提高,能更好地满足汽车发动机增压强化的需要.     

复合材料增强活塞机械变形与热变形分析

国内外十分重视复合材料强化活塞的技术开发 ,活塞的设计、强化技术和评价技术也取得了很大进展。本文利用计算机工作站对复合材料强化后的活塞进行机械变形、热变形有限元分析 ,探讨复合材料强化的方式与结构尺寸对变形影响的趋势。复合材料增强活塞技术已在几种车用发动机活塞上进行了推广应用 ,表明复合材料增强活塞结构设计合理 ,热疲劳强度和抗热应力、机械应力和变形的能力得到较大的改善 ,活塞工作能力提高 ,能更好地满足汽车发动机增压强化的需要     

木粉含量对木粉/PP复合材料的热性能与燃烧性能的影响

利用热重分析法(TGA)和锥形量热仪(CONE)研究了不同木粉含量对木塑复合材料(WPC)热稳定性和燃烧性能的影响.TGA研究结果表明,随着木粉含量的增加,WPC的热稳定性逐渐降低,但体系的成炭量明显提高,800℃时成炭率由0.01％增加到14.63％;锥形量热仪(CONE)的实验结果表明,WPC的热释放速率、比消光面...     

活塞热冲击有限元分析

在热冲击试验的基础上,采用ANSYS软件对活塞在高、低周波矩形热冲击模式下的温度响应、热应力进行了计算和分析。计算结果表明:在高、低周波热冲击下,活塞的温度响应有着不同的特性。计算结果对活塞热疲劳分析有着重要的参考价值。     

A Theoretical Analysis on the Thermal Buckling Behavior of Fully Clamped Sandwich Panels with Truss Cores

This article presents a theoretical analysis on the thermal buckling behavior of sandwich panels with truss cores under fully clamped boundary conditions, subjected to uniform temperature rise. The Reissner model is developed by ignoring the flexural rigidity of the core and considering the shear stiffness of the sandwich panel is only contributed by truss cores. By using double Fourier expansions to the virtual deformation mode, the critical temperature of sandwich panels is obtained. Theoretically predicted critical temperatures are in good agreement with those from FEM. The effect of boundary conditions and structure parameters of the sandwich panel are also discussed.     

Optimum Structure Design of a Multilayer Piezo-Composite Disk for Control of Thermal Stress

This article deals with a control problem of a thermal stress in a composite circular disk consisting of a transversely isotropic structural layer onto which multiple piezoelectric layers with concentrically arranged electrodes are perfectly bonded. When a prescribed heating temperature distribution acts on the structural layer surface, the optimum structure design of the composite disk is performed so that the maximum thermal stress in the structural layer is minimized subject to constraints on stresses in the piezoelectric layers. A hybrid optimization technique combining the particle swarm optimization with the simplex method is employed for solving the optimum design problem. To resolve the difficulty in solving the problem with many optimization variables, three improvements are added to the hybrid optimization technique and an efficient design method is introduced. For a composite disk constructed of a CFRP layer and cadmium selenide layers, the layer thicknesses, the electrode dimensions, and the voltages applied to the electrodes are determined and the numerical results are presented in tabular and graphical forms. Finally, it is shown from the optimum design results that the highest suppression ratio of the maximum thermal stress reaches 40.8% in the case of a five-layer composite disk and is considered to be almost saturated.     

Thermal conductivity enhancement in a latent heat storage system

Latent heat storage systems especially those employing organic materials have been reported to exhibit a rather slow thermal response. This is mainly due to the relatively low thermal conductivity of organic latent heat materials. In this study, experiments were carried out to investigate a method of enhancing the thermal conductivity of paraffin wax by embedding aluminum powder in it. The size of the aluminum powder particles was 80 μm. The tested mass fractions in the PCM-aluminum composite material were 0.1, 0.3, 0.4, and 0.5 of aluminum. The used mass fraction in the experimental work was 0.5.The experiments were conducted by using a compact PCM solar collector. In this collector, the absorber-container unit performed the function of absorbing the solar energy and storing the phase change material (PCM). The solar energy was stored in the PCM and was discharged to cold water flowing in pipes located inside the PCM. Charging and discharging processes were carried out. The propagation of the melting and freezing fronts was studied during the charging and the discharging processes. The time wise temperatures of the PCM were recorded during the processes of charging and discharging. The solar intensity was recorded for the charging process. It was found that the charging time was reduced by approximately 60% by adding aluminum powder in the wax. In the discharging process, experiments were conducted for different water flow rates of 9-20.4 kg/h. It was found that the useful heat gained increased when adding aluminum powder in the wax as compared to the case of pure paraffin wax. The heat transfer characteristics were studied.     

Analysis for Thermal Conductance Effect on the Interfacial Thermal Stresses of Anisotropic Composites

The present work applies the regularized boundary integral equations that are newly developed to treat the thermoelastic field in thin anisotropic media. For the anisotropic thermal field, a direct domain mapping technique is applied with a unique interface condition that considers the heat conductance relation. By incorporating the heat conductance effect, the paper investigates how interfacial thermal stresses between generally anisotropic materials vary with the heat conductance coefficient. Accounting for the thermal conductance effect, the paper presents the complete algorithm for computing the thermal as well as the subsequent elastic fields on interfaces between dissimilarly adjoined anisotropic composites.     

Thermal conductivity and cycle characteristic of metal hydride sheet formed using aramid pulp and carbon fiber

This paper describes the thermal and hydrogenation properties of a metal hydride (MH) sheet consisting of MH powder, aramid pulp, and carbon fiber. MH sheets were prepared by the wet paper method in which an agglutinated slurry of raw materials was dispersed onto a stainless steel mesh in water and then the sheet was dehydrated and dried. The cyclic characteristics and thermal conductivities of the MH sheets were experimentally investigated. The effects of changing the carbon fiber ratio and the measurement direction on the effective thermal conductivity were measured by the steady heat flow method. The thermal conductivity increased to 3.20 W/m·K with increasing carbon fiber ratio only in the planar direction. The decreases in mass due to removing MH powder and/or carbon fiber from sheet were less than 1 mass% after around 100 hydrogen absorption/desorption cycles. Moreover, the MH sheet was effective at decreasing the stress on the reactor vessel due to the expansion of MH during hydrogen absorption/desorption.     

F170风冷柴油机热负荷试验分析

通过对F1170风冷柴油机温度场的分析,研究其结构参数对热负荷的影响及改善方法。     

陶瓷基点阵夹芯结构等效导热系数的数值模拟分析

为了评价陶瓷基点阵夹芯结构的热防护效能,选取陶瓷点阵夹芯结构的胞元作为研究对象,给出了表征其传热效能的等效导热系数计算方法。建立了点阵夹芯结构胞元的导热-辐射稳态耦合传热的有限元模型,通过对模型施加不同的边界条件,利用数值模拟的方法求出了点阵夹芯结构稳态温度场分布和等效导热系数,并对其换热机理和影响因素进行了分析。研究表明：点阵夹芯结构的辐射换热是结构热传导的主要方式,且随温度的升高其作用效应就越强;相对较小的材料发射率和较大的芯杆高度能够降低结构的传热效能;减小芯杆直径会降低结构热防护能力;芯杆倾角对结构的热防护性能影响较小。     

Transient Thermal Fracture Analysis of Transversely Isotropic Magneto-Electro-Elastic Materials

Modern materials such as magneto-electro-elastic materials are used in the development of smart structures. The magneto-electro-elastic materials possess the dual features that the application of electric field induces magnetization and magnetic field induces electric polarization. The theory of linear magneto-electro-elasticity is applied to solve transient thermal fracture in magneto-electro-elastic cylinder under sudden heating on its outer surface. The equilibrium equations are obtained from the constitutive equations. The governing partial differential equations are deduced by using equilibrium equations of elastic, electric and magnetic fields. The heat conduction equation is solved by separation of variable technique. Hankel transform is applied to solve elastic displacements, electric potential and magnetic potential. The problem is reduced into integral equation involving Bessel functions which is treated exactly using Abel's integral equation. Transient distributions of temperature, stress, displacement and magnetic inductions are derived for magneto-electro-elastic cylinder. Thermal stress, electric displacement and magnetic induction-intensity factors are obtained. The solutions are valid for both impermeable and permeable crack models. The studies are valuable for such material analysis and design.     

高周波活塞热冲击计算与分析

本文用6150柴油机燃气温度拟合成三角形热冲击模式，作为活塞顶面的热激励源，建立了高周波三角形热冲击及集总参数导热模型，计算该活塞顶面温度响应曲线及其变化规律，以作为活塞顶面热疲劳分析和研究的基础。