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1.
新型高倍显微镜云纹测量技术及其应用 总被引:1,自引:0,他引:1
本文介绍了两种新型的高倍显微镜云纹测量技术,即激光扫描共聚焦显微镜(LSCM)云纹法和扫描电子显微镜(SEM)云纹法。阐述了LSCM云纹和SEM云纹的形成及测量原理,同时对此两种云纹法加以对比,比较其各自的特点。此外,还对两种云纹法的应用进行探讨,针对测量物体表面变形和表征物体表面周期性结构特征这两类应用领域,分别以测量多晶铝合金板的残余变形和识别日本纹白蝶翅膀表面结构为例介绍LSCM云纹法的应用,以识别绿带翠凤蝶翅膀表面结构为例介绍了SEM云纹法的应用。实验结果证明了LSCM云纹法和SEM云纹法的可行性、灵活性及高灵敏度特性,均为高效、无损的全场测量技术,在微纳米尺度力学特性测量和表征方面有广泛的应用前景。 相似文献
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粘接双材料界面微区力学行为的细观实验分析 总被引:1,自引:0,他引:1
本文将显微光栅与显微测距技术结构起来,实现了物体表面位移场的细观测量,应用这一方法,本文定量地测量了高分子粘接结构界面及周围区域的变形的应变,实验发现界面两侧存在着一个影响区,在影响区内材料的力学性质发生了变化,本文在实验结果的基础上讨论和分析了这一变化并对界面的力学模型进行了讨论。 相似文献
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本文讨论从被物体表面形状调制的图象江载波信号中提了以该表面深度全场信息的测量方法,结合成熟的计算机图象处理技术,该方法可构成在精度、量程、自动化程度方面具有很强适应性的无接触测量系统。文中给出了自动测量系统的构成设计,并给出了测量实例。 相似文献
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本文采用数字散斑干涉法和栅线投影法同时测量了任意曲表面的三维位移和三维形貌,并运用数字图像处理技术分析了曲表面的三维应变场,用实验方法获得了曲表面的主应变和主方向。 相似文献
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球形压痕技术在材料力学属性,诸如硬度,弹性模量等的测量中得到了广泛的应用。应用Twyman-Green及云纹干涉法并配合相移技术,本文对IN783合金进行了一系列的球形压痕实验研究,并对残余压痕的面内(u,v)及离面(w)变形场进行了定量测量和分析。应用面内变形测量结果,进一步对试件表面的应力一应变分布进行了分析和计算,并在离面变形场的基础上,确立了压痕周围的弹塑性边界,从而进一步应用面内的分析结果,得到材料的屈服强度。应用压痕实验的接触半径和压力并配合Tabor经验公式,本文进一步得到了材料的应力应变曲线。实验结果与已知的IN783合金相吻合。对所涉及的一系列压痕实验,本文也进行了二维有限元分析并得到了比较一致的结果。 相似文献
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表面涂层材料的残余应力测量技术 总被引:2,自引:0,他引:2
本文采用电测盲孔法测定表面涂层材料残余应力的测量技术,在试件和表面涂层结构上进行测试.大量试验表明,此方法可靠、有效,可在工程实际中使用,为解决表面涂层“爆裂”等问题,提供了有效的测定残余应力的手段 相似文献
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利用氪化技术测量固体润滑材料的表面工作温度 总被引:1,自引:0,他引:1
文章阐述了氪化技术测温的原理、方法和精度,报道了以其对CO_2压缩机无油润滑活塞环表面工作温度的测量结果。作者指出,利用这种技术测量固体润滑材料表面工作温度是可行的,其测温范围是从室温到1000℃,测温精度±5℃;氪化技术测温是一种在线原位测量方法,可以应用于各种摩擦副的表面工作温度测量。 相似文献
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Classical shallow-ice theory assumes that bed topography under ice sheets has slopes comparable to the surface slope of the
ice sheet. A modification of the classical steady-state theory which allows for significant bed topography on shorter length
scales has recently been developed by Morland (Proc. R. Soc L. Ser. A., 456, 1711-1739 ), but his theory requires explicit integration of the ice-flow equations over the topography length scale, which may be
below the grid size of typical numerical ice sheet models. Here we present a method for parameterising the effect of basal
topography of wavelengths much greater than ice thickness but much smaller than the horizontal extent of the ice sheet on
the bulk flow of the ice sheet. In particular, we are able to show through the use of a multiple-scales expansion technique
that the effect of such topography is described by a simple correction factor applied to the classical expression for ice
flux. This correction factor dispenses with the need to integrate explicitly over the topography length scale and could allow
the effect of such topography to be included in numerical models with limited grid size. Examples are given for the practical
implementation of this `correction factor method' in calculations of the steady-state shape of ice sheets.
Received August 20, 2002 / Accepted February 3, 2003/ Published online May 9, 2003 / L. W. Morland 相似文献
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This paper gives systematic study on the process of ice layer accretion, especially the mass and energy transfer between two-phase
distribution (air and water droplet) and icing build-up region along the surface of airfoil. Based on the theory of momentum
and thermal boundary layer, the governing equations are constituted by considering the conservation of mass and energy in
each control volume which is equivalent to the grid cell in fact. The finite volume method is used to discrete the control
equations and then the calculations for convective heat transfer coefficient and ice shape are accomplished successfully.
During the icing computation, the heat transfer characteristics are updated timely after every time step using multi-time
step algorithm. In order to verify reliability of this method mentioned above, some results are compared to the ones from
LEWICE software and experiment. At last, the effects of several key parameters on heat transfer coefficient and ice shape
are presented in this paper using the model of NACA 4412 airfoil, and these factors include free-stream velocity, static temperature,
angle of attack and the roughness height of surface. 相似文献
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在海冰与自升式海洋平台结构的相互作用过程中,冰载荷是影响平台结构振动响应和疲劳寿命的重要因素. 采用具有粘接-破碎效应的离散元模型,可对海冰与自升式海洋平台结构作用中的海冰破碎特征及相应冰载荷进行数值分析. 针对自升式海洋平台的多桩腿结构特性及其冰载荷离散元分析的大规模计算需求,建立了基于GPU 的并行算法并开发了相应的计算程序. 为实现离散元分析的高效计算,采用网格排序方法创建单元邻居列表,以快速确定海冰单元间及其与平台结构间的接触模式和作用力. 此外,还发展了球体单元与圆柱形结构在不同接触形式下的计算模型. 为检验该离散元模型的有效性,对渤海锥体海洋平台结构的作用过程进行了计算,并与现场实测冰力数据进行了对比验证. 在此基础上对多桩腿自升式平台结构的冰载荷进行了离散元分析,获得了海冰的破坏特性,确定了不同桩腿上的冰力时程. 该模型可进一步应用于不同类型海洋结构的冰载荷分析,为冰区海洋平台的结构设计和现役平台结构的疲劳分析提供参考依据. 相似文献
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海冰与自升式海洋平台相互作用GPU离散元模拟 总被引:1,自引:0,他引:1
在海冰与自升式海洋平台结构的相互作用过程中,冰载荷是影响平台结构振动响应和疲劳寿命的重要因素. 采用具有粘接-破碎效应的离散元模型,可对海冰与自升式海洋平台结构作用中的海冰破碎特征及相应冰载荷进行数值分析. 针对自升式海洋平台的多桩腿结构特性及其冰载荷离散元分析的大规模计算需求,建立了基于GPU 的并行算法并开发了相应的计算程序. 为实现离散元分析的高效计算,采用网格排序方法创建单元邻居列表,以快速确定海冰单元间及其与平台结构间的接触模式和作用力. 此外,还发展了球体单元与圆柱形结构在不同接触形式下的计算模型. 为检验该离散元模型的有效性,对渤海锥体海洋平台结构的作用过程进行了计算,并与现场实测冰力数据进行了对比验证. 在此基础上对多桩腿自升式平台结构的冰载荷进行了离散元分析,获得了海冰的破坏特性,确定了不同桩腿上的冰力时程. 该模型可进一步应用于不同类型海洋结构的冰载荷分析,为冰区海洋平台的结构设计和现役平台结构的疲劳分析提供参考依据. 相似文献
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L. A. Tkacheva 《Journal of Applied Mechanics and Technical Physics》2018,59(2):258-272
This paper consideres the behavior of a semi-infinite ice cover on the surface of an ideal incompressible fluid of finite depth under the action of a load moving with constant velocity along the edge of the cover at some distance from it. The ice cover is modeled by a thin elastic plate of constant thickness. In a moving coordinate system, the deflection of the plate is assumed to be steady. An analytic solution of the problem is obtained using the Wiener–Hopf technique. The wave forces, the deflection of the plate, and the elevation of the free surface of the fluid at different velocities of the load are investigated. 相似文献
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海冰动力学数值模拟中改进的PIC方法 总被引:2,自引:0,他引:2
为了准确地模拟海冰的动力过程,需要建立精确有效的数值方法。本文结合质点网格法(PIC)和光滑质点流体动力学方法(SPH)发展了一种改进的PIC方法。该方法在欧拉坐标下对海冰动量方程进行差分计算,在拉格朗日坐标下进行海冰质点位移、厚度和密集度计算,并采用Gauss函数进行欧拉网格点与拉格朗日质点间海冰参数的交互插值。采用改进的PIC方法对规则区域内的海冰堆积过程进行了数值试验,对渤海海冰的动力过程进行了72小时数值模拟。计算结果均表明改进的PIC方法具有计算量小,计算结果平稳精确的优点,可很好地适用于海冰动力作用过程的数值模拟。 相似文献
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Increased traffic safety levels are of highest importance, especially when driving on icy roads. Experimental investigations for a detailed understanding of pneumatic tire performance on ice are expensive and time consuming. The changing ambient and ice conditions make it challenging to maintain repeatable test conditions during a test program. This paper presents a tire–ice contact model (TIM) to simulate the friction levels between the tire and the ice surface. The main goal of this model is to predict the tire–ice friction based on the temperature rise in the contact patch. The temperature rise prediction in the contact patch is based on the pressure distribution in the contact patch and on the thermal properties of the tread compound and of the ice surface. The contact patch is next classified into wet and dry regions based on the ice surface temperature and temperature rise simulations. The principle of thermal balance is then applied to compute the friction level in the contact patch. The tire–ice contact model is validated by comparing friction levels from simulations and experimental findings. Friction levels at different conditions of load, inflation pressure, and ice temperatures have been simulated using the tire–ice contact model and compared to experimental findings. 相似文献
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In northern countries, subfreezing temperatures during the winter season result in the formation of ice covers on most rivers. Towards the end of the winter season, during the spring break-up period, stationary ice covers become weak in strength and break up. The resulting broken ice pieces or ice floes are significantly larger in thickness and have a rougher undersurface relative to sheet ice and impose higher hydraulic resistance. The downstream movement of the ice floes may be arrested under conditions such as an intact ice cover, bridge piers or channel constrictions, among others, thereby initiating a break-up ice jam. These ice jams most often have been observed to cause very high water stages. Detrimental effects caused by these high water levels encompass those of operational and design-related problems such as the flooding of communities due to ice-jam-induced backwater, flood risk assessments, altering of the open water flow regime, bed scour and flooding of bridges. The ability to predict the influence of an ice jam on the main flow is of considerable importance in river engineering and can be viewed upon by its effects on the variation in the water surface levels. All other information is dependent on the foregoing. The ice jam influence on the main flow can be regarded with respect to local and global standpoints. The primary objective of this study is to formulate the influence of the ice jam on the main channel flow. The formulation is then coupled with a two-dimensional numerical model for the simulation of the water flow regime. The data from different laboratory experiments on ice jams are reproduced numerically. Various simulations are then carried out to compute the water surface levels and velocities in channels under ice jam conditions. The numerical results are then compared with the laboratory data. Results show that the mathematical formulation developed to predict the water surface levels and velocities along the ice jam length as well as upstream and downstream of its leading and trailing edges respectively gives satisfactory predictions. 相似文献
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Driving on ice is still a risky activity. Research has investigated the factors contributing to the friction mechanism and has reported experimental studies of pneumatic tyres on ice in order to develop models that predict tractive and braking performance on ice/snow. Therefore, developing testing methods to obtain relevant experimental data for the validation of models is equally important.There are agricultural and industrial vehicles which are also designed for pulling but there are no specific studies reporting experimental tests on traction force of such machines in snowy conditions. However, this issue is very topical, as demonstrated by the appearance on the market of winter tyres for such vehicles.This study presents a method for testing winter tyres in outdoor test facilities with a focus on traction performance. The conclusions will serve in future investigations as a concise knowledge source to develop improved testing facilities and tyre–ice interaction models, aiding the development of better tyre designs and improved vehicle safety systems.The functional tests hereafter described have been carried out with the aim of evaluating the possibility of measuring the influences of different technique solutions on the performance of certain 17.5 R25 sized industrial tyres. 相似文献