共查询到20条相似文献,搜索用时 93 毫秒
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在应变测量中,基于普通二维数字图像相关(2D-DIC)的光学引伸计易受到离面刚体位移的影响,从而使得应变测量精度不高。为此,提出了基于双反射镜成像技术的光学引伸计,将试样正反面同时记录在单相机的成像靶面上。在试样正反面对应位置各置一个光学引伸计,取两者应变平均值,则可消除离面刚体位移对光学引伸计应变测量结果的影响。基于该引伸计,开展了环氧树脂和铸铁两类脆性材料的单轴拉伸实验,分别得到了应力-应变曲线。实验结果表明,本文提出的引伸计比基于普通二维DIC的光学引伸计具有更高的应变测量精度,是一种便捷、高效、高精度的应变测量方法,非常适用于脆性试样的应变测量。 相似文献
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在J.R.Asay等提出的双屈服面法(简称AC方法)测量动态屈服强度的基础上,对实验设计和数据处理做了部分改进。在实验设计方面,在满足实验物理设计的前提下,将 AC方法的卸载实验装置(双层飞片和双台阶样品)简化为单飞片和单台阶样品,以简化波系作用,并减少了声速测量不确定度的引入因素。在数据处理方面,发现由Lagrange声速和工程应变关系曲线外推求预冲击态的体积声速容易引入较大的不确定度,而通过Lagrange声速和粒子速度关系曲线可以更清晰地得到塑性卸载起始点,使图解法和积分法得到的屈服强度值趋于一致。利用改进后的AC方法,得到了低温退火后LY12铝在20.0 GPa预冲击压力下的屈服强度为0.6 GPa。 相似文献
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一种测量固体表面温度的单色高温计经改进后,用于火焰动态温度测量,本文设计了三组实验对其可行性进行研究,即:黑火药与铝热剂的分层火焰温度测量实验、单色高温计与热电偶的测温对比实验和激波管内氢氧爆炸火焰动态温度测量实验。结果表明,当目标尺寸远大于单色高温计红外视场时,所测火焰温度可视为单色高温计光轴上的最高温度;采用单色高温计和热电偶同时测量发光火焰的温度,测量结果相差不到6.2%;单色高温计所测氢氧爆炸火焰的动态温度曲线,较好地反映了爆炸火焰的动态传播规律;经改进的单色高温计可以用于爆炸火球等发光火焰的动态温度测量。 相似文献
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在爆炸容器中进行小药量空中爆炸实验, 利用传感器序列测量冲击波速度, 根据冲击波Rankine-Hugoniot关系获得测点近似理论峰值压力, 从而实现压力传感器的标定, 获得的灵敏度相对误差较小。同时测量了相应的冲击波参数, 并利用Modified-Friedlander公式进行数据后处理, 结果表明固定超压拟合更接近物理事实, 固定正相时间拟合也具有较高精度。最后进行了误差分析, 发现不同传感器特性及数据后处理方法都会带来一定误差。实验结果表明这种测量和后处理方法具有较高的精度, 可以同时标定传感器和测量冲击波参数。 相似文献
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Nonisothermal moisture transport in hygroscopic building materials: modeling for the determination of moisture transport coefficients 总被引:1,自引:0,他引:1
Menghao Qin Rafik Belarbi Abdelkarim Ait-Mokhtar Lars-Olof Nilsson 《Transport in Porous Media》2008,72(2):255-271
A mathematical model for calculating the nonisothermal moisture transfer in building materials is presented in the article.
The coupled heat and moisture transfer problem was modeled. Vapor content and temperature were chosen as principal driving
potentials. The coupled equations were solved by an analytical method, which consists of applying the Laplace transform technique
and the Transfer Function Method. A new experimental methodology for determining the temperature gradient coefficient for
building materials was also proposed. Both the moisture diffusion coefficient and the temperature gradient coefficient for
building material were experimentally evaluated. Using the measured moisture transport coefficients, the temperature and vapor
content distribution inside building materials were predicted by the new model. The results were compared with experimental
data. A good agreement was obtained. 相似文献
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A new evaluation method for Nusselt numbers in naphthalene sublimation experiments in rotating-disk systems 总被引:1,自引:1,他引:0
Igor V. Shevchuk 《Heat and Mass Transfer》2008,44(11):1409-1415
A comparative analysis of theoretical and empirical relations, as well as experimental data for mass transfer of a rotating
disk in laminar, transitional and turbulent flows for naphthalene sublimation in air was done. New correlations between local
and average Sherwood numbers for the entire disk were offered. A new evaluation approach for Nusselt numbers based on the
experimental data for naphthalene sublimation in laminar, transitional and turbulent flows was developed. 相似文献
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The use of the stratified flow momentum balance for the deduction of interfacial and liquid wall shear stresses from experimental measurements is examined. A systematic error analysis is applied to the governing equations using the principle of maximum uncertainty. A series of air–water experiments were conducted in 50 and 80 mm diameter pipes, in which gas pressure drop, liquid height and gas wall shear stress were measured. A framework for the correlation of the deduced shear stresses is proposed from the experimental measurements. The uncertainty analysis is used to show that the definition of mean liquid height does not significantly influence the overall results. The development of empirical equations based on such methods may lead to total uncertainties of up to 40%, irrespective of accuracy of the experimental data or the appropriateness of the correlating technique. Comparisons with state-of-the-art correlations for the liquid wall and interfacial friction factor data showed even larger discrepancies between measurement and prediction. 相似文献
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《International Journal of Multiphase Flow》1999,24(8):1407-1423
The use of the stratified flow momentum balance for the deduction of interfacial and liquid wall shear stresses from experimental measurements is examined. A systematic error analysis is applied to the governing equations using the principle of maximum uncertainty. A series of air–water experiments were conducted in 50 and 80 mm diameter pipes, in which gas pressure drop, liquid height and gas wall shear stress were measured. A framework for the correlation of the deduced shear stresses is proposed from the experimental measurements. The uncertainty analysis is used to show that the definition of mean liquid height does not significantly influence the overall results. The development of empirical equations based on such methods may lead to total uncertainties of up to 40%, irrespective of accuracy of the experimental data or the appropriateness of the correlating technique. Comparisons with state-of-the-art correlations for the liquid wall and interfacial friction factor data showed even larger discrepancies between measurement and prediction. 相似文献
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Qiao Weigao 《Journal of Terramechanics》1996,33(4):167-172
This paper makes an analysis of the hull starting resistance of a boat-type vehicle. It demonstrates that the soil cohesion and friction change along with the changes in the soil moisture content. A mathematical model of the hull starting resistance of a boat-type vehicle by theoretical and experimental inference is obtained. A forecast, tests and verification of the hull starting resistance were carried out and experimental results that tallied with the forecast ones were obtained. The hull starting resistance using the model was forecast for a real vehicle and methods were explored for reducing the hull starting resistance of a boat-type vehicle along a beach and in a swamp. 相似文献
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Impact-tension compression test by using a split-Hopkinson bar 总被引:1,自引:0,他引:1
Kinya Ogawa 《Experimental Mechanics》1984,24(2):81-86
A new impact-tension-compression testing technique based on a one-dimensional elastic-stress-wave theory has been developed. The technique was applied to investigate dynamic response in pure iron. The experimental results of the loading wave agreed well with the theoretical prediction. The stress, strain, and strain rate of a specimen during impact were evaluated with the aid of a stress-wave analysis. A new experimental technique has been developed to investigate the dynamic-hysteresis loop and the dynamic Baushinger effect in materials. It is presently being developed for applications to dynamic-fatigue studies. 相似文献
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By using unique experimental techniques and carefully constructed experimental apparatus, the characteristics of flow boiling of water in microscale were investigated using a single horizontal rectangular microchannel. A polydimethylsiloxane rectangular microchannel (Dh = 103.5 and 133 μm) was fabricated by using the replica molding technique, a kind of soft lithography. A piecewise serpentine platinum microheater array on a Pyrex substrate was fabricated with the surface micromachining MEMS technique. Real time flow visualization of the phase change phenomena inside the microchannel was performed using a high speed CCD camera with microscope. The experimental local boiling heat transfer coefficients were studied, and single bubble inception, growth, and departure, as well as elongated bubble behavior were analyzed to elucidate the microscale heat transfer mechanisms. Tests were performed for mass fluxes of 77.5, 154.9, and 309.8 kg/m2 s and heat fluxes of 180–500 kW/m2. The effects of mass flux, heat flux, and vapor qualities on flow boiling heat transfer in a microchannel were studied. 相似文献
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《Particuology》2017
A computational fluid dynamics study of three-phase counter-current fluidization occurring in a turbulent contact absorber was performed. A two-dimensional, transient Eulerian multi-fluid model was used, in which the dispersed solid phase was modeled employing a kinetic theory of granular flow. The grid independence of the model, the effect of wall boundary conditions, the choice of granular temperature model, the effects of order of discretization scheme and drag models were studied for a base case setting. The results of simulations were validated against experimental results obtained from the literature. Once the model settings were finalized, simulations were performed for different gas and liquid velocities to predict the hydrodynamics of the absorber. Computed bed expansion and pressure drop were compared with experimental data. Good agreement between the two was found for low velocities of gas and liquid. 相似文献