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1.
针对上海同步辐射装置(SSRF)光束线前端挡光元件需要承受高热负载的要求,对挡光元件所使用的纳米Al2O3颗粒增强Cu基复合材料Glidcop(R),采用一维稳态纵向热流法测量其在不同应变状态下的热传导系数.用有限元模拟了试件的温度场分布,并对试验结果进行了误差分析,揭示了试验误差的主要来源.试验测量结果表明,经历半寿命低周疲劳循环所产生的应变损伤累积对Glidcop(R)导热系数的影响可以忽略.  相似文献   

2.
电阻应变片是目前常用的测量应变传感元件.应变片特性的标定方法影响到测量值的准确程度.本文介绍我们测量应变极限的方法,并对灵敏系数标定梁表面应变的计算公式提出一点看法.  相似文献   

3.
分析了分布式光纤传感器测量结果的可靠性,提出从应变系数和温度系数标定到分布式光纤传感器物理量测量以及结果评价的方法,设计了分布式光纤传感器的应变系数和温度系数标定装置,同时分析了应变标定装置的不确定度来源,采用基于光频域反射技术的分布式光纤解调仪进行了实验验证。应变标定范围为-5000με~5000με,温度标定范围为20℃~50℃,第一次测量得到应变系数和温度系数分别为:-6.6775με/GHz和-0.5921℃/GHz。使用获得的应变系数和温度系数再次测量,得到在测量范围内,应变测量相对误差为1%,温度测量相对误差为2%,满足工程应用要求。上述结果表明,设计、发展的数据标定及分析方法可用于分布式光纤传感器应变系数和温度系数的标定。  相似文献   

4.
1 前言应变测量装置是以电阻应变片(作为检测元件或作为传感器的敏感元件)为主体的力学测量仪器。它实质上是一种测量电阻应变片的微小电阻变化或电阻相对变化量的电子仪器。对于电阻值为120欧姆和灵敏系数K=2.00的应变片而言,分辨1微应变只能产生0.00024  相似文献   

5.
本文应用光纤光栅传感器实现了对钢筋混凝土试件内部应变的测量.试验不仅就应用光纤光栅进行混凝土结构内部应变测量的技术、工艺进行研究,还通过设计温度控制试验,考察了光纤光栅传感器的温度补偿问题,以及横向应变对测量结果的影响.  相似文献   

6.
介绍了由压电陶瓷和树脂材料构成的正交异性压电复合材料(Orthotropic Piezoelectric Composite Material,简称OPCM)应变传感元件的构造及传感原理,推导了粘贴式和埋入式OPCM传感元件测量正交异性材料构件中应力的传感方程。对受平面应力场的作用的正交异性板的表面应力,应变进行了实测研究,并对测试误差进行了分析。  相似文献   

7.
高温合金材料循环相关热机械疲劳寿命预测   总被引:5,自引:0,他引:5  
在变温非线性运动强化规律所描述的高温合金材料热机械寿命应力-应变循环特性的基础上,讨论了应变控制的循环相关热机械疲劳寿命预测技术,所建模型采用了由应变以密度表示的损伤参数,并且引入了温度损伤系数,考虑了温度变化范围以及温度循环和应变循环相位关系对疲劳寿命的影响,在确定模型的一些参数,采用等温力学试验和疲劳试验的数据,为了把等温疲劳研究成果推广到变温疲劳分析领域,开辟了新的途径。  相似文献   

8.
动态拉伸试验中试样应变测试的有效性分析   总被引:3,自引:0,他引:3  
田宏伟  郭伟国 《实验力学》2008,23(5):403-410
为了评估将试样通过胶粘连接到加载杆的Hopkinson杆装置所获得试样应变的有效性,对四种强度刚度差异较大的纤维增强复合材料进行了动态拉伸试验。试验时,试样通过环氧胶和杆夹层粘接,试样的应变分别按照Hopkinson杆一维应力波理论计算和试样上应变计直接准确测量得到。结果证明:对小变形碳纤维复合材料,按一维应力波理论计算的应变与试样上直接所测应变值偏差超过100%;对较大变形的GFRP和KFRP层合板,两者偏差小于40%。说明采用Hopkinson杆一维应力波理论计算的试样应变不准确。为修正不准确性,一是通过大量数据分析建立按一维应力波理论计算值与直接测量应变之间的关系式,用此式可使此试验装置获得有效的试样应变;二是借助ABAQUS有限元模拟分析得出粘胶层以及试样过渡弧段的变形,用一维应力波理论计算的应变减去此变形,也可获得有效的试样应变。  相似文献   

9.
实心圆轴扭转测定本构关系的概念和方法   总被引:6,自引:0,他引:6  
何蕴增  邹广平 《实验力学》2003,18(3):426-432
本文提出了实心圆轴扭转试验建立有限应变本构关系(τ—γ曲线)的概念,并在文[1]工作的基础上完成了通过实心圆轴扭转试验建立文献[6]形式的有限应变本构关系的方法,它比单向拉伸试验所得到的本构关系更为精确,因拉伸实验变形较大时试件伸长和变细对测量结果有影响,尤其在“颈缩”后,很难对有关力学量作有效测量和分析,扭转本构关系的描绘也更为完整,以低碳钢为例,扭转本构关系所描述的有效范围比拉伸本构关系大十余倍,本文方法将有利于探讨研究更大应变下的材料力学行为。  相似文献   

10.
为测量结构内部动应变,我们采用了在结构内部预埋应变片的方法。首先将应变片制成应变元件或应变体以固定应变片的位置,然后按照要求将应变元件或应变体埋入模型中,浇注成整体,进行测试。这里介绍的是我们预埋 ...  相似文献   

11.
12.
国际传热研究前沿──微细尺度传热   总被引:69,自引:0,他引:69  
微细尺度传热问题的工程背景来自于80年代高密度微电子器件的冷却和90年代出现的微电子机械系统中的流动和传热问题.它的特点是,当空间和时间尺度微细化后,出现了很多与常规尺度下不同的物理现象,其原因可以分为两大类:一类是连续介质的假定不再适用,另一类则是各种作用力的相对重要性发生了变化.所需研究的挑战性问题有,导热系数的尺度效应、导热的波动现象,微小通道中流动和传热,流动压缩性和界面效应等的影响,微细尺度下的辐射和相变等.  相似文献   

13.
A mass transfer measuring method based on absorption, chemical and coupled colour reaction is used to visualize and determine the shell side local heat transfer in the first baffle compartment of shell-and-tube heat exchangers with segmental baffles for staggered tube arrangement. Local mass transfer coefficients were transformed into heat transfer coefficients by using the analogy between heat and mass transfer. The local, per-tube and integral heat transfer coefficient distributions are presented.  相似文献   

14.
下降液膜在逆向流动空气作用下的换热   总被引:1,自引:0,他引:1  
以下一代核电站反应堆安全壳非能动冷却为背景,对竖直管内过冷下降液膜在逆向空气.水蒸汽流动作用下的换热提出了一个分析模型,对液膜采用边界层近似理论,对空气.水蒸汽混合气采用由热质传递比拟理论引出的关联式进行分析,考察了各种条件下液膜的厚度、温度、吸收热量与蒸发热量沿流向的变化,与相关研究进行了对比,表明了模型的合理性。  相似文献   

15.
Freezing around a spherical heat sink immersed in an infinite phase change medium — a free boundary problem involving growth and decay of the free boundary — is analysed here. A one-dimensional conduction model is formulated and the resulting partial differential equations are solved by finite difference methods. The energy discharged from the phase change medium during the heat transfer process is analysed for latent heat thermal energy storage applications. Results are presented for a wide range of parameters that are encountered in energy storage devices. The cases of slab/cylindrical heat sink are reexamined for a range of parameters not covered by the earlier investigators  相似文献   

16.
This study proposed a new method, namely a tube-by-tube reduction method to analyze the performance of fin-and-tube heat exchangers having plain fin configuration under dehumidifying conditions. The mass transfer coefficients which seldom reported in the open literature, are also presented. For fully wet conditions, it is found that the reduced results for both sensible heat transfer performance and the mass transfer performance by the present method are insensitive to change of inlet humidity. Unlike those tested in fully dry condition, the sensible heat transfer performance under dehumidification is comparatively independent of fin pitch. The ratio of the heat transfer characteristic to mass transfer characteristic (hc,o/hd,o Cp,a) is in the range of 0.6~1.0, and the ratio is insensitive to change of fin spacing at low Reynolds number. However, a slight drop of the ratio of (hc,o/hd,o Cp,a) is seen with the decrease of fin spacing when the Reynolds number is sufficient high. This is associated with the more pronounced influence due to condensate removal by the vapor shear. Correlations are proposed to describe the heat and mass performance for the present plate fin configurations. These correlations can describe 89% of the Chilton Colburn j-factor of the heat transfer (jh) within 15% and can correlate 81% of the Chilton Colburn j-factor of the mass transfer (jm) within 20%.  相似文献   

17.
For a uniform saturated porous layer heated from below, the dependence of the quantity of heat transferred on the distribution of the heat source is investigated. It is found, using perturbation methods and numerical techniques, that very small nonuniformities in the heat source having the same wavelength as the preferred convection mode significantly reinforce natural convection.  相似文献   

18.
Generally, it is an economic advantage to operate a heat pipe in a condition where the ratio of heat flow rate, Q, to mass, m, is a maximum. It is shown that a maximum of the function Q/m may be obtained if the ratio between the evaporator and the condenser lengths is optimum. To achieve this optimization, all the other geometrical elements of the heat pipe and the heat transfer coefficients are considered constants, the only variables being the two lengths.  相似文献   

19.
In order to examine if the heat conduction in porous material behaves like a wave as claimed by other researchers, experiments on transient heat transfer is conducted in casting sand. The results show that the heat propagation can be described neither by wave nor by diffusion model. The CV-wave concept is discussed and challenged according to the experimental results in the entire transient stage, including the transient response of temperature and the response curve of penetration-depth versus penetration-time.  相似文献   

20.
Heat transfer from a flat plate has been investigated when a cylinder array is located near the wall. Each cylinder in the cylinder array was positioned normal to the flow direction and parallel to the flat plate surface. Measurements of the heat transfer coefficient and the optimum value for the cylinder pitch and spacing between the cylinders and the flat plate surface were obtained. A comparison of the heat transfer mechanism in this flow system with that obtained previously for the case when a single cylinder is inserted in the boundary layer was made.  相似文献   

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