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在摩擦学和传热学理论的基础上,建立了滚动轴承温度场数值仿真模型,对轴承内部温度的分布进行了研究,获得了环境温度、工作载荷和润滑脂容积比变化时轴承温度的修正公式。并以轴承的振动和润滑脂温度为监测参数,建立了轴承状态监测系统。运用温度分布规律对测点温度进行了修正,有效地消除了环境温度、工作载荷以及润滑脂容量变化对报警准确性的影响。 相似文献
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Ooi EH Ng EY Purslow C Acharya R 《Proceedings of the Institution of Mechanical Engineers. Part H, Journal of engineering in medicine》2007,221(4):337-349
This paper presents the two-dimensional simulation of heat propagation in the human eye model during contact lens wear with finite element analysis. Three types of contact lens are studied: Lotrafilcon A, Balafilcon A, and Etafilcon A. The models are solved for both steady and transient solutions. The corneal surface temperature during contact lens wear is found to decrease (average, 0.52 +/- 0.05 degrees C compared with a bare cornea for all lens types). A contact lens with a higher water content has a lower steady state temperature than a contact lens with a lower water content does. Various initial temperatures for the contact lens are found to affect the first 400 s of the temperature variation. When the initial temperature is lower than the corneal temperature, a reduction in temperature is observed during contact lens insertion while the opposite is observed when the initial temperature is higher than the corneal temperature. The increase in evaporation rate when a contact lens is worn increases the cooling effect on the ocular surface. This is suggested to be the cause of lower corneal surface temperature when wearing a contact lens. 相似文献
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《Measurement》2016
During the production process of rolled steel plates quality control plays an important role. The temperature distribution in the plate, which is determined with a temperature measuring device, has to be assessed on homogeneity. The temperature data is stored in a rectangular array. A real-time assessment is required. A new method, the Adaptive Cross Approximation (ACA) for the temperature assessment is proposed. The ACA-method is applied to a two-dimensional rectangular temperature array. The temperature array as a result of measurements contains a stochastic measuring tolerance. Nevertheless, the temperature field, which is usually a full matrix, can be approximated by a series of low rank matrices according to the ACA-method. The number of iteration steps is used as the criterion on homogeneity. Numerical examples, based on real industrial data, illustrate the efficiency of the ACA-method. In most cases, the subjective human evaluation of temperature fields matches with the assessment made by the ACA-method. Furthermore, the ACA-method leads to a significant compression of the temperature arrays and can be also used for archiving of the measured data almost without loss of information. 相似文献
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文章根据活动保障和服务需求,在活动前期开展了多种表面温度观测,并与百叶箱气温、太阳辐射等进行对比与相关分析。结果表明:各项观测温度的日最大值均出现在正午前后,常与太阳辐射辐照度同步达到日最大值。日变化最大的观测项目为人造假发温度,其次是柏油路面温度、塑料椅面温度和百叶箱外气温,日变化最小的观测项目为百叶箱内气温;采用人造假发放置地表的观测方法所得数据的误差较大,增加真发碎发、真发发套温度观测使数据更具代表性;塑料椅面与人造假发升温和降温较快;温度较高时,柏油路面温度较其他观测项目表面高温持续时间长。 相似文献
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A reflective fiber temperature sensor system based on the ZnO thin film is proposed. The transmittance spectra and temperature dependent optical property of the sensing head with ZnO thin film is investigated theoretically and experimentally, and the temperature resolution of ~1?°C is obtained in the temperature region of 300-773 K. The temperature sensing system is only related to the wavelength shift of transmittance spectra, and has a high stability without depending on the incident light intensity. This research results also indicate a fiber optical sensor with a broad temperature measurement range (10-1800 K) can be gained as a promising temperature sensing device, and can be applied into some extremely environments, such as aircraft, nuclear power station and power transmission system, and so on. 相似文献
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The energy consumption of crushing is directly affected by the mechanical properties of cement materials. This research provides a theoretical proof for the mechanism of the stress relaxation of cement clinkers under high temperature. Compression stress relaxation under various high temperatures is discussed using a specially developed load cell, which can measure stress and displacement under high temperatures inside an autoclave. The cell shows that stress relaxation dramatically increases and that the remaining stress rapidly decreases with an increase in temperature. Mechanical experiments are conducted under various temperatures during the cooling process to study the changes in the grinding resistance of the cement clinker with temperature. The effects of high temperature on the load-displacement curve, compressive strength, and elastic modulus of cement clinkers are systematically studied. Results show that the hardening phenomenon of the clinker becomes apparent with a decrease in temperature and that post-peak behaviors manifest characteristics of the transformation from plasticity to brittleness. The elastic modulus and compressive strength of cement clinkers increase with a decrease in temperature. The elastic modulus increases greatly when the temperature is lower than 1000 °C. The compressive strength of clinkers increases by 73.4% when the temperature drops from 1100 to 800 °C. 相似文献
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A new light microscope–temperature‐controlled chamber (LM–TCC) has been constructed. The special feature of the light microscope–temperature‐controlled chamber is the Peltier‐element temperature control of a specimen holder for biological samples, with a volume capacity of 1 mL. This system has marked advantages when compared to other approaches for temperature‐controlled microscopy. It works in a temperature range of −10°C to +95°C with an accuracy of ±0.1°C in the stationary phase. The light microscope–temperature‐controlled chamber allows rapid temperature shift rates. A maximum heating rate of 12.9°C min−1 and a maximum cooling rate of 6.0°C min−1 are achieved with minimized overshoots (≤1.9°C). This machinery operates at low cost and external coolants are not required. Especially with samples absorbing irradiation strongly, temperature control during microscopy is necessary to avoid overheating of samples. For example, leaf segments of Ficaria verna exposed to 4500 μmol photons m−2 s−1 in a standard microscopic preparation show a temperature increase (δT) of 18.0°C, whereas in the light microscope–temperature‐controlled chamber this is reduced to 4°C. The kinetics of microscope‐light induced δT are described and infrared thermography demonstrates the dissipation of the temperature. Chloroplasts of the cold adapted plant Ranunculus glacialis show the tendency to form stroma‐filled protrusions in relation to the exposure temperature. The relative number of chloroplasts with protrusions is reduced at 5°C when compared to 25°C. This effect is reversible. The new light microscope–temperature‐controlled chamber will be useful in a wide range of biological applications where a rapid change of temperature during microscopic observations is necessary or has to be avoided allowing a simulation of ecologically relevant temperature scenarios. 相似文献
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踏面制动引起车轮温度急剧上升,影响车轮材料性能和轮轨接触状态,加剧车轮磨耗。基于Archard磨耗模型,建立一个考虑摩擦温升效应的地铁车轮磨耗预测模型。模型中根据车轮材料属性与温度之间的关系,考虑摩擦温升对接触斑大小、黏滑区划分和磨耗深度的影响,可实现对高温下的车轮磨耗特性的研究。相对以往的车轮磨耗预测模型,该模型能反映温度对磨耗影响的物理本质,适合研究轮轨接触界面有较大温度(如踏面制动)时的车轮磨耗演化机理。用所建立的车轮磨耗数值预测模型,计算对比不同温度下的轮轨接触状态和车轮磨耗深度。结果表明,轮轨接触斑和滑动区面积随温度的升高而增加;温度升高使接触斑单元磨耗深度增加,当踏面温度从常温25℃增加到最高温度300℃时,最大磨耗深度0.4 nm,增幅为28.4%;车轮转动一圈后,其径向磨耗深度也随温度的升高而明显增加,最大径向磨耗深度15 nm,增幅为28.2%,同时,车轮横向位置的磨耗范围增加5.8%,为踏面制动形式的地铁车轮磨耗预测研究提供更加准确的理论模型。 相似文献
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Yeon Suk Choi 《Journal of Mechanical Science and Technology》2014,28(2):747-753
An experiment to calibrate temperature sensors at cryogenic temperature has been performed. The main objective of this study was to develop a precise instrument for calibrating the temperature sensors over a temperature range of 4 K to approximately room temperature without liquid helium. The instrument consists of radiation shields, a sensor block, an electric heater, a cryocooler and a vacuum chamber. In a vacuum chamber, the cold head of the cryocooler is thermally anchored to the sensor block to bring the apparatus to a desired temperature. An electric heater is placed at the second stage of the cryocooler to control the temperature of the sensor block. The entire apparatus is covered by radiation shields and wrapped in multi-layer insulation to minimize thermal radiation in a vacuum chamber. The dimensions of components including instrumental wires are optimized to reduce total heat invasion from room temperature into cryogenic temperature. The vacuum chamber is pumped down and cooled to cryogenic temperature by a cryocooler. The resistance of each temperature sensor is measured at steady state as well as cooling down and warming up cycles, and the performance of calibration is discussed with respect to the sensitivity and resolution. 相似文献
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Flash temperature has a profound influence on the tribological behavior of contact surfaces. An asperity flash temperature model is developed for journal bearings with a thin soft coating. The asperity flash temperature of tin coated 339 Al-Si alloy bearings in contact with case hardened steel journals is analyzed. Factors influencing the flash temperature are discussed. Correlations of the flash temperature with asperity roughness parameters, such as the RMS roughness and skewness values, are explored. It was found that the maximum rise in temperature increased as the roughness and skewness increased. 相似文献
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Gangxian Zhu Anfeng Zhang Dichen Li Yiping Tang Zhiqiang Tong Qiaopan Lu 《The International Journal of Advanced Manufacturing Technology》2011,55(9-12):945-954
To discuss the influence of thin-walled blade??s curvature change and accumulating layer number on the temperature field distribution in laser direct metal deposition and obtain a uniform thickness of a thin-walled blade, the temperature field distribution was calculated by numerical simulation. The thin-walled blade??s curvature change and accumulating layer number can be studied, respectively. The effect of accumulating layer number on temperature field distribution was studied by thin wall; the effect of curvature change on temperature distribution was investigated by thin-walled rings with different curvatures. The numerical results show that the molten pool temperature of the thin wall increases with the layer number, and the molten pool temperature of thin-walled ring increases with the its curvature. The rules of laser power changing with the layer number and curvature in the processing of the thin-walled blade can be obtained by simulation when keeping molten pool temperature stable. According to the numerical results, the thin-walled blades were fabricated by experiments. The experimental results show that the laser power should be changed with the layer number and curvature if a uniform thickness of the blade can be obtained, which is in agreement with the numerical simulation. 相似文献
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基于动态内热源特性的车用锂离子动力电池温度场仿真及试验 总被引:3,自引:0,他引:3
针对电动汽车动力电池在充放电工作过程中由于热量聚集而导致的温度场非均匀性问题,采用数值仿真与试验相结合的方法,基于电池内阻温升特性,考虑耦合正负极耳的热影响,建立生热速率的时变内热源模型,获得更加精确的电池温度场分布及其动态变化规律,并深入进行温度一致性分析。以某车用锂离子动力电池为样本,对电池单体及模块分别进行温升计算和三维温度场分析及相应的测试试验。结果表明:同一充/放电倍率下,放电温升明显大于充电温升,且电池最大温差随着倍率的增大而增大;电池的温升是一个随时间先增大后恒定的非线性变化过程,且随着放电倍率的增大电池温升速率越大;电池模块温度场并非电池单体温度场的简单叠加,且在相同充放电倍率下电池模块的热一致性不如电池单体。 相似文献
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The thermal property of insulation material is essential in developing high temperature superconductor (HTS) devices operating at around liquid nitrogen temperature. Unlike metallic materials, nonmetallic materials have a thermal resistance; therefore, accurate estimate of the heat flow is difficult in the case of nonmetallic materials. In this study, a precise instrument is developed for measuring the thermal property of insulating materials over a temperature range of 30 K to approximately the room temperature by using a cryocooler. The cold head of the cryocooler is thermally anchored to the thermal link and used to cool the apparatus to a desired temperature. The temperature distribution in specimen is measured with respect to the supplied heating power, from which the thermal conductivity is calculated and compared with published data for accuracy confirmation. The effective thermal conductivity of polypropylene laminated paper (PPLP) is presented and the trend in the behavior of conductivity near liquid nitrogen temperature is also discussed. 相似文献
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A. E. Ashford W. G. Allaway F. Gubler A. Lennon J. Sleegers 《Journal of microscopy》1986,144(2):107-126
An apparatus for embedding tissues at resin temperatures down to 228 K is described. By placing thermocouples in the resin the temperature has been monitored during embedding at low temperature with glycol methacrylate (GMA) and Lowicryl K4M. Even in this apparatus with a liquid cooling bath the heat of polymerization is not dissipated and the resin temperature rises. This rise is directly proportional to the resin temperature at the onset of polymerization and is higher in Lowicryl K4M than GMA. The initial resin temperature also affects the time taken for polymerization. The time to the onset of the peak and its duration are both increased as the temperature is lowered. This effect is more pronounced with GMA than Lowicryl K4M and polymerization of GMA is inhibited at the lowest temperature used. When Lowicryl K4M, polymerized at low temperature, is warmed up to ambient a further exothermic reaction occurs, which causes the resin temperature to rise well above ambient. Both this temperature peak and that during polymerization are reduced, but not totally eliminated, by reducing the resin volume. Aircooled systems are inefficient compared with the low-temperature apparatus used here and the resin temperature rise is consequently greater and, even with small resin volumes, it can be very high. It is therefore unlikely for published methods that the temperature specified has been maintained in the resin during polymerization. The implications of these findings are discussed in relation to enzyme and antigen survival. Recommendations include use of very small volumes of resin, refrigerated liquid-bath rather than air-cooled systems and contact with a heat sink when specimens are warmed up to ambient temperature. Examples of enzyme reaction, antigen survival and structural preservation obtained with the method are presented. 相似文献