航天器用十一种热控材料热物理性质及其与显微组织和工艺因素关系的研究

应用自行研制的激光脉冲法热导仪、小平板稳态法热导仪、铜卡计和冰卡计法比热仪, 对航天器用的十一种热控材料的导热系数、导温系数和比热及其与材料显微组织和工艺因素的关系进行了实验研究. 结果表明, 在室温至1800℃温区内, 绝热材料和防热材料的导热系数均随温度升高而增大, 多孔绝热材料的有效导热系数是由多种导热因子相互作用的结果, 并存在对应于最小导热系数的最佳密度. 所得数据为热控材料的优选提供了科学判据, 亦为航天器的热控系统热设计提供了参数.     

时域径向积分边界元法在平面单相凝固问题中的应用

该文将时域精细积分边界元方法与界面追踪法相结合,给出平面单相凝固热传导问题的一个有效数值分析方法。首先,利用稳态热传导问题的基本解和径向积分法给出瞬态传热问题的边界积分方程,并采用精细积分方法求解离散的微分方程组,获得相变界面的热流密度。然后应用相变界面上的能量守恒方程,采用界面追踪法来预测相变边界的移动位置,从而给出相关问题数值模拟的结果。最后,为验证该文方法的有效性,给出两个数值算例并与解析解进行了对比。结果表明,该文方法具有较高的求解精度,是求解相变热传导问题的一种有效数值方法。     

An analytical method for thermal stresses of a functionally graded material cylindrical shell under a thermal shock

In this paper, the thermal stresses of a thin functionally graded material (FGM) cylindrical shell subjected to a thermal shock are studied. An analytical method is developed. The studied problem for an FGM cylindrical shell is reduced to a plane problem. A perturbation method is used to solve the thermal diffusion equation for FGMs with general thermal properties. Then, the transient thermal stresses are obtained. The results show that the thermal shock is much easier to result in failure than the steady thermal loading. The present method can also be used to solve the crack problem of an FGM cylindrical shell with general thermal properties.     

复合材料热传导系数均匀化计算的实现方法

均匀化理论可以有效预测周期性结构复合材料的等效热传导系数,然而其控制方程的载荷项形式特殊,通用有限元软件中没有对应的载荷形式,难以直接求解.提出一种本构关系及场变量的类比方法,证明了在此类比下等效热传导系数均匀化方程与等效弹性模量均匀化方程是等价的.根据求解等效弹性模量均匀化方程的热应变法,提出一种新的等效热传导系数均匀化方程数值求解方法.以ABAQUS为平台,预测单向纤维复合材料以及金属蜂窝夹芯板的等效热传导系数,计算结果与参考值吻合良好.该方法为基于通用有限元软件的复合材料等效热传导系数的均匀化计算提供了简便途径.     

碳纳米管/聚对苯二甲酸乙二酯纳米复合材料热降解动力学

用原位聚合的方法制备了聚对苯二甲酸乙二醇酯(PET),带羧基的多壁碳纳米管/PET(MWNTs-COOH/PET)纳米复合材料和带羟基的多壁碳纳米管/PET(MWNTS-OH/PET)纳米复合材料。用热重分析(TG)仪测试了三种样品的热降解稳定性,用Friedman法和Ozawo法对测试结果进行了热降解动力学分析。结果表明,通过加入MWNTs,两种MWNTs/这PET纳米复合材料的热稳定性都有不同程度的提高。MWNTs-COOH/PET的稳定性从开始降解到结束都比纯PET高,MWNTs-OH/PET开始降解阶段的稳定性不如纯PET,而在降解后期稳定性明显比纯PET高。     

蜂窝芯体面外方向导热系数等效研究

利用商用有限元软件分析了高温阶段蜂窝芯体面外方向等效导热系数,分析结果与试验数据和半经验公式结果进行了对比,对比结果显示有限元软件可以用来预测蜂窝芯体面外方向等效导热系数。利用有限元软件分析了低温阶段蜂窝芯体面外方向等效导热系数,证明在0℃以下时辐射换热对蜂窝芯体面外方向导热系数的影响可以忽略,同时得到了铝合金蜂窝芯体在0℃以下时面外方向等效导热系数近似公式。     

单向纤维复合材料导热性预测

本文利用均匀化方法预测复合材料导热性。采用这一方法给出了单向纤维复合材料沿纤维方向的导热性表达式;将该方法与有限元技术结合得到了在垂直于纤维方向上复合材料导热性数值形式的预测结果。根据这些结果我们用曲线形式给出了材料导热性同各组分体分比间的关系,分析了体分比、纤维截面形状和分布方式、纤维和基体间的相对导热系数等因素对材料整体导热性影响。注意到纤维分布的随机性,本文还研究了纤维相对位置对材料导热性的影响,指出相对位置的变化可导致材料的各向异性导热性。本文指出基体相导热性对材料整体导热性的影响比纤维相的影响更重要。和已有的理论和实验结果的比较说明,本文提出的方法是很有效的。      

Verification of the new viscoelastic method of thermal stress calculation in asphalt layers of pavements

The new viscoelastic method of thermal stress calculations in asphalt layers has been developed and published recently by the author. This paper presents verification of this method. The verification is based on the comparison of the results of calculations with results of testing of thermal stresses in Thermal Stress Restrained Specimen Test. The calculations of thermal stresses according to the new method were based on rheological parameters of the Burgers model. The parameters were measured in laboratory at different low temperatures, at long time creep under constant loading. Five asphalt mixes were tested. Three of them were high modulus asphalt concretes and two conventional asphalt concretes. Specimens were prepared in exactly the same way both for rheological creep tests and for the Thermal Stress Restrained Specimen Test. The results of measured thermal stresses were compared with thermal stresses calculated from the new viscoelastic method developed by the author and in most cases a good agreement was found. For comparison, the measured stresses were compared with results of calculations according to the existing methods. The viscoelastic Monismith method failed in prediction of thermal stresses. The prediction from the quasi-elastic Hills and Brien method was underestimated, but better than from the Monismith method and worse than from the new viscoelastic method. The reasons of discrepancies were discussed.     

以物体表面温度推算变导热系数的测试原理及技术

提出了一种根据第三类边界条件下物体表面温度的测定值推算随温度线性变化的物体导热系数的测试原理和方法。利用设计的测试系统对几种材料的导热系数进行了测量和计算。结果表明，测试计算方法简单可行。为测定物体变导热系数提供了一个有效的方法。     

Measurements of the Thermal Conductivity and Thermal Diffusivity of Polymer Melts with the Short-Hot-Wire Method

In this paper, the thermal conductivity and thermal diffusivity of four kinds of polymer melts were measured by using the transient short-hot-wire method. This method was developed from the hot-wire technique and is based on two-dimensional numerical solutions of unsteady heat conduction from a wire with the same length-to-diameter ratio and boundary conditions as those in the actual experiments. The present method is particularly suitable for measurements of molten polymers where natural convection effects can be ignored due to their high viscosities. The results have shown that the present method can be used to measure the thermal conductivity and thermal diffusivity of molten polymers within uncertainties of 3 and 6%, respectively. Further, the thermal conductivity and thermal diffusivity of solidified samples were also measured and discussed.     

考虑参数更新的大跨桥梁温差极值分布估计方法研究

为了建立可靠的大跨桥梁全寿命温差极值分布模型,提出采用广义帕累托分布（Generalized Pareto Distribution,GPD）对超阈值温差的统计特征进行描述,并给出了超阈值温差样本相关性的去除方法和最优阈值的确定方法。为了融合温差分布的先期经验信息和不断递增的温差监测样本,建立了考虑参数更新的贝叶斯估计方法,利用Gibbs抽样对贝叶斯后验分布进行计算,进而得到准确的基于广义帕累托分布的温差极值分布模型。最后利用九堡大桥长期监测温差数据进行了验证。研究结果表明,广义帕累托分布能够对超阈值温差样本的尾部统计特征进行准确描述,提出的考虑参数更新的温差极值分布贝叶斯估计方法能够对广义帕累托分布的参数进行可靠估计,估计的统计模型比极大似然估计计算的结果更接近真实情况。研究结果可为大跨桥梁温差特性分析提供参考。     

Bi2Sr2CaCu2O8＋x单晶的热导率测量

介绍了有关高温超导材料的热导率性质、测试方法和测试结果。结合我们的测试经验，讨论了稳态热流法测量高温超导体热导率应注意的问题。给出了Ｂｉ２Ｓｒ２ＣａＣｕ２Ｏ８＋ｘ单晶沿ａｂ面热导率的测试结果。     

Dynamic Measurements of the Thermal Conductivity of Insulators

Measurements of the thermal conductivity of insulators that are commonly used in civil engineering are as a rule performed using Pönsgen??s guarded hot-plate method under steady-state conditions. Achieving these steady-state conditions is a time consuming and relatively expensive procedure. Therefore, the application of a method that is less time consuming and less costly to common building insulating materials is of interest. The method should also have the accuracy and repeatability comparable to that of presently used methods. One such method is the transient hot-wire method (predominantly used for liquids, non-Newtonian fluids, plastics, semi-plastics, and similar materials), a dynamic method that uses a very thin pure platinum wire that functions as a thermal source in combination with a temperature sensor that detects temperature transients. This article describes the application of the transient hot-wire method to most commonly used building thermal insulating materials. The transient hot-wire measurements of the thermal conductivity were performed on many building material samples. For the sake of comparison, the thermal conductivity of samples made from the same materials was also tested using the stationary Pönsgen??s guarded hot-plate method. This article describes the comparison and evaluation of the measurement results obtained from both methods as well as the estimation of pertinent measurement uncertainties. The results are presented in graphical and numerical form in tables and diagrams for each type of thermal insulator.     

热冲击作用下的陶瓷材料破裂过程数值分析

运用热传导和热2力耦合的相关理论 , 借助统计分布来考虑陶瓷中存在的微孔洞和微裂隙 ; 建立了一种可以模拟陶瓷遭受热冲击作用下的裂纹萌生、 扩展过程的数值模拟方法 , 并通过材料破坏过程分析系统 (RF2PA , Realistic Failure Process Analysis) 加以实施。该数值方法基于细观非均匀性假设 , 突破了以往连续介质力学视陶瓷为均匀介质的假设 , 并从细观损伤角度考虑陶瓷热冲击破坏演化的过程。运用该方法对三面绝热、 一面受热冲击的平板状陶瓷材料的破裂过程进行了数值试验。结果表明 : 起始裂纹发端于受热冲击表面 , 且在初始的裂纹萌生阶段 , 在受热冲击表面产生一系列无序的裂纹 ; 但随着时间的延续 , 裂纹逐渐演变成多条近乎平行的、沿受冲击表面内法向方向扩展的主裂纹 , 其中一些裂纹的发展受到了屏蔽 , 这一结果与试验结果吻合较好。本数值方法为相关研究提供了新的思路。      

热重法研究漆酚镍螯合高聚物热分解动力学

用非等温热重法研究了漆酚镍螯合高聚物的热分解反应动力学,结果表明漆酚镍螯合高聚物热分解过程是一级反应,用Ozaw-(I)法和Reich法求得的热分解反应平均活化能分别是173.21KJ mol~(-1) 和181.12KJ mol~(-1)。     

非饱和土壤热导率模型的优化研究与应用

本文在Campbell模型和de V-1模型的基础上,以Campbell模型为主,对该模型中的两个参数形状因子（ga）和土壤固相热导率（ ）采用de V-1模型中的计算方法,提出了一种新的预测土壤热导率温度关系的模型。该模型土壤固相热导率和形状因子均考虑了土壤颗粒组成成分,也包含了温度对土壤固相热导率的影响。此外,与前两种模型进行比较,该模型与实验值吻合较好,能够更好地预测土壤热导率。基于该模型,分析了土壤温度和体积含水率两个变量对不同类型土壤热导率的影响。研究表明：在同一温度及体积含水率工况下,土壤热导率是砂土>壤土>粘土。该研究为地埋管换热器周围非饱和土壤热湿耦合迁移模型的建立提供新的思路。     

近地空间下X/EUV透射光栅的热力学有限元分析

为了实现极紫外透射光栅光谱仪在近地空间的应用,针对其核心色散元件2000线/毫米X/EUV透射光栅,本文采用有限元方法建立了机械模型并对其热学性能和耦合特性进行计算机模拟计算,通过模拟热膨胀系数不同的材料构成的薄膜光栅在近地空间受到太阳辐照后的温度场,得到该光栅表面的热形变分布.结果表明,在高真空热环境下,该透射光栅表面形变量平均可达0.56μm,而影响光栅周期的纵向形变平均值则为71.5 nm.由于热形变会对光栅衍射效率产生重要影响并导致光谱仪精度和性能的下降,利用有限元分析模拟的结果,进一步优化光栅的封装和设计制作,使其栅线处纵向热形变趋近于零,为2000线/毫米X/EUV透射光栅在太阳极紫外辐射探测器上得到应用提供了科学依据和有效支持.     

水滑石/钙锌复合热稳定剂对PVC的热稳定作用

本文制备了水滑石/钙锌复合热稳定剂,采用XRD、FT-IR及静态热老化、脱HCl等实验及分析手段,探讨了水滑石对PVC的热稳定机理,研究了水滑石/钙锌复合热稳定剂对PVC的热稳定性能。实验表明,水滑石对PVC热解释放的HCl进行吸附分两个过程,首先层板羟基与HCl反应,然后层间CO32-与Cl-进行交换,可明显改善PVC的热稳定性,使PVC脱HCl的诱导时间提高了1.4倍。     

不同防老剂对胶清橡胶性能影响的研究

分别采用乳液共混法与机械共混法,研究不同防老剂与胶清橡胶并用的力学性能、热性能、加工性能。结果表明:防老剂的加入能提高胶清橡胶的力学性能,其中加有防老剂264、防老剂SP-P的胶清橡胶老化性能提升较为显著;乳液法共混制得胶清橡胶的力学性能和老化性能优于机械共混法;防老剂的加入使热性能有所提升,但乳液共混法的热性能略微好于机械共混法。RPA加工分析表明,防老剂的加入使胶清橡胶加工性能下降,但机械共混法所制备的胶清橡胶加工性能优于乳液共混法。     

面向非稳态传热的热像仪相对测温性能评估

提出了一种热像仪相对测温的性能评价方法。将薄片热电偶的热节点固定在温度场均匀的加热单元表面,作为标准辐射温度发生单元,被待评价的热像仪观测和测温,对比热像仪观测的热电偶热节点表面温度场数据和热电偶自身测得的温度数据的相似度,对热像仪相对测温性能进行评价。基于国内外4个品牌的7款不同规格热像仪进行测试,结果表明热像仪的相对测温误差和绝对测温误差相差较大,相对测温误差通常介于噪声等效温差和绝对测温误差之间,同时发现6号热像仪性能较差,温漂严重,通过装置中的A、B两靶标同时测试热像仪性能,评价结果的标准差均在8%以内,这表明该方法具有较高的可靠性,对热像仪相对测温性能评价研究有一定的参考意义。