第六届磨削及表面质量学术研讨会论文摘要

应用红外热像仪测量磨削温度场的探讨文章介绍了用红外热像仪测量磨削温度场的原理和测试方法。通过与传统的热电偶法比较,两者所得结果是一致的,但新方法具有能通过显示器将看不见的温度场的温度分布,形态、大小以及随时间变化的规律直观、清楚地展现在人们面前。文章同时就影响测量精度以及该     

红外热像仪测量切削温度的误差来源分析与实验研究

用红外热像仪测量切削温度时,拍摄角度、距离以及物体表面发射率都是导致测温误差的来源。在红外热像仪测温理论分析的基础上,对这些因素用控制变量法进行实验。结果结果表明,拍摄角度在5o~10o和30o~35o这两个范围内,测温误差较小。热像仪与切削区之间的距离在1.1m~1.2m的范围内,测量温度比较稳定。对于粗加工45号钢而言,表面发射率设在0.48~0.45之间,温度波动较小,此区间的发射率为较好。研究结果对于红外热像仪现场监测切削温度,具有实际的指导意义。     

流动沸腾条件下微通道壁面温度的红外特征

设计并搭建了沸腾换热试验台,采用TH5104红外热像仪测量微通道壁面温度来研究混合制冷工质在微通道内的沸腾换热特性.测量试件是一外径为1.22 mm,内径为0.86 mm,长为200 mm的不锈钢单圆管.实验利用红外热像仪测量并记录下质量流量为1 726～8 635 kg/m2·s,热流密度为65～231 kW/m2时壁面温度的变化情况.实验分析和讨论结果显示:微通道壁面的温度分布沿着轴向变化有明显的规律性;水平微尺度通道内流动沸腾过程中,试件前后段有较大的温差效应,温差的正负与热流密度的大小有关;壁面温度的变化与热流密度、管内工质的流型和换热形式关系密切,流型越复杂,壁面温度变化越剧烈.     

数控车床主轴热变形误差检测及改善措施

热变形误差是影响高速高精密数控机床加工精度的主要因素,对机床主轴热变形进行检测与研究显得至关重要。以CAK3665数控车床主轴为研究对象,运用传热学经典理论对主轴系统的热源分布以及传热方式进行了介绍,并通过FLIR红外热像仪测温技术和激光测距技术对主轴温升与车床热变形进行了测量与研究,测得主轴中速连续运转270min时达到稳定温升,温度对主轴轴向的热伸长误差的影响大于主轴径向的热变形误差。最后,根据测量结果提出减小主轴热变形的措施。研究工作为车床主轴的进一步改进设计和热变形补偿提供依据。     

磁悬浮磨削主轴热态特性

磁悬浮磨削主轴在散热条件差、系统温度过高时,会导致转子部件热膨胀,产生热应力或改变磁力轴承以及电动机的间隙,从而降低系统的可靠性.研究采用试验测量和有限元分析相结合的方法,在考虑传导和辐射的传热方式下,建立磁悬浮磨削主轴热态分析有限元模型,利用有限元软件ANSYS对磁悬浮磨削主轴进行温度场分析,得到主轴组件的温度场分布.利用HY-2988G红外热像仪测量磁悬浮磨削主轴的温度场分布.研究表明,提高冷却效率可有效控制磁悬浮磨削主轴的温升,另外尽可能将温度监测点的位置选择在电动机处.通过对试验和理论结果的对比分析,得出磁悬浮磨削主轴的热设计及结构设计对系统工作时温度分布有着重要影响,同时可为其温度的在线监测和控制提供理论依据.     

红外热像技术在材料疲劳研究中的应用

利用红外热像仪可以精确、实时、非接触地测量材料疲劳过程中的温度变化,确定材料的疲劳极限和Wohler线。该方法相对于传统的疲劳实验方法,红外热像法具有方便、快捷、低成本等优点,同时红外热像法确定的材料疲劳极限都在工程误差范围内。     

径向磁浮轴承温度场数值模拟与试验验证

基于热力学理论,应用ANSYS Workbench软件的热分析模块对径向磁浮轴承温度场进行数值模拟,并进行稳态热分析。同时利用红外热像仪测量径向磁浮轴承的温度场分布,对比试验数据与仿真数据,确认仿真结果的准确性,进而验证数值模拟时边界条件施加的正确性。所做仿真与试验为径向磁浮轴承的结构设计和温升控制提供了参考。     

点接触混合润滑闪温分析

基于统一的Reynold方程系统,数值分析点接触混合润滑固体表面温度分布。采用瞬态移动点热源积分方法计算闪温,通过两表面温度平衡方程迭代确定热流分配系数,研究在不同卷吸速度和滑滚比情况下,光滑表面和非高斯随机粗糙表面点接触混合润滑的温度分布。结果表明:数值模拟得出的两表面温差很小,符合实际情况;非高斯随机粗糙表面与光滑表面最大温升都在出口区,非高斯随机粗糙表面比光滑表面温升更高;滑滚比一定时,卷吸速度越大两表面温升越大;卷吸速度一定时,滑滚比越大两表面温升越大。     

红外热像仪外场测温的大气透过率二次标定

为了实现测温红外热像仪的外场精确测温,研究了大气透过率的二次标定。建立了红外热像仪的外场远距离测温标定模型,采用一个标准面源黑体和红外热像仪对大气透过率进行了二次标定。首先,用标准面源黑体的设置温度标定大气透过率的二次修正系数;然后,在已知目标感兴趣区域发射率的情况下,用二次修正系数对未知辐射源测量值进行修正,实现未知辐射源目标辐射温度的准确测量。实验显示,随黑体设置温度从50℃不断升高(二次大气透过率近似为1),大气二次透过率修正系数在50～100℃内迅速下降,在100～200℃内下降趋势减缓,逐渐接近于约为0.7的常数。实验结果为测温红外热像仪外场精确测温提供了保证。     

基于ABAQUS的单排四点接触回转支承接触分析

以单排四点接触回转支承为研究对象,以其在最大轴向力作用下滚球与滚道接触区应力分布与变形量为研究重点,通过赫兹接触理论求解得到其接触区接触椭圆大小、接触面最大接触应力以及接触中心变形量,利用ABAQUS有限元软件取得了与赫兹接触理论近似的结果,但有限元法得到的接触区应力分布与变形量情况更为全面。此外,有限元法还得到了滚道接触区最大等效应力的位置,该位置距离滚道表面的距离远小于回转支承制造时要求的滚道表面淬硬层深度。     

Nondestructive test of brazed cooling tubes of prototype bolometer camera housing using active infrared thermography

The active infrared thermography technique is used for assessing the brazing quality of an actively cooled bolometer camera housing developed for steady state superconducting tokamak. The housing is a circular pipe, which has circular tubes vacuum brazed on the periphery. A unique method was adopted to monitor the temperature distribution on the internal surface of the pipe. A stainless steel mirror was placed inside the pipe and the reflected IR radiations were viewed using an IR camera. The heat stimulus was given by passing hot water through the tubes and the temperature distribution was monitored during the transient phase. The thermographs showed a significant nonuniformity in the brazing with a contact area of around 51%. The thermography results were compared with the x-ray radiographs and a good match between the two was observed. Benefits of thermography over x-ray radiography testing are emphasized.     

Electrosurgical dispersive electrodes heat cutaneous and subcutaneous skin layers

Electrosurgical return electrodes can produce heating, and occasionally burns, of cutaneous and subcutaneous skin layers. Up to now, only limited aspects of modern, dispersive, polymer electrodes have been studied using infrared thermography and thermocouples. This report presents new results on a quantitative infrared study, and adds the aspects of subcutaneous effects using microwave thermography as a third dimension. In agreement with previous work in infrared thermography, average cutaneous temperature increases observed in a dozen human volunteers were 1.5 degrees C for the normal mode, and 5.7 degrees C at near-fault (with partial contact). The intradermal and/or subcutaneous microwave thermographic images exhibited slightly lower, but still significant temperature elevations which were located at a more leading location, and were more widespread. This significant heating of subcutaneous layers, particularly of the sensitive stratum germinativum, clearly suggests the need for multiple-depth (microwave and infrared) thermography in order to evaluate the thermal performance of dispersive electrosurgical return electrodes.     

Thermography in incremental forming processes at elevated temperatures

Temperature measurement is essential for several forming processes at elevated temperatures. It serves to determine and control the workpiece temperature. Thermography as a non-contact-based technology offers the possibility to capture thermograms of complete workpieces without any time-offset. However, the application of thermography requires the knowledge of the fundamentals of radiation thermometry, in particular the emissivity. This paper presents the results of the application of thermography in incremental sheet forming (ISF) with Joule heating and radial–axial ring rolling as a bulk forming process. Using thermography for the determination of the temperature of the forming zone allows for a real-time closed loop control in ISF with Joule heating. Additionally, the results of the temperature measurement of the surface temperature of radial–axial rolled rings are presented, which can be used as a starting point to make a forecast of the rings’ dimensions in cold state.     

线接触条件下微动摩擦特性的研究

通过试验研究了线接触微动摩擦特性。研究表明：线接触微动摩擦因数变化与点接触形式相同；位移幅值在部分滑移区时，表面粗糙度对表面磨损有影响。磨痕分析表明，承载区域接触不均匀，存在虚接触区域，其大小与表面粗糙度有关，而接触区域没有不磨损的粘着区，不同于点接触形式。     

Contact and thermal analysis of transfer film covered real composite-steel surfaces in sliding contact

For composite-steel surfaces in sliding contact an anisotropic numerical contact algorithm has been developed to study the ‘layer type’ problems. An FE contact analysis was applied to evaluate the contact parameters (real contact area, contact pressure distribution and normal approach). The contact temperature rise was determined by using both a numerical thermal algorithm for stationary and a FE transient thermal technique for ‘fast sliding’ problems.The effect of a continuous transfer film layer (TFL), that had built up during wear of the PEEK matrix material on the steel counterpart, was considered. Its thickness was assumed to be t=1 μm, and its material properties were that of PEEK at room temperature or, in the case of frictional heating, at a temperature of 150°C (i.e. above the glass transition temperature of the polymer matrix).Results are presented for a spherical steel asperity, with/without TFL, sliding over composite surfaces of different fibre orientation, and in addition, for real composite-steel surfaces (based on measured surface roughness data) in sliding contact. The TFL has an effect on the contact parameters especially at higher operating temperatures (i.e. 150°C); it results in the production of a larger contact area and a lower contact pressure distribution. The contact temperature rise is clearly higher if a TFL is present. Due to the low thermal conductivity of PEEK, the TFL is close to the melting state or it even gets molten within a small vicinity of the contact area.     

新型点磨削砂轮磨削参数对磨削温度影响研究

提出了一种带有粗磨区倾角θ的陶瓷结合剂CBN点磨削砂轮,这种新型砂轮具有磨除率高、加工精度好等优点。研究了磨削热产生与分配理论和红外测温原理。分别用不同θ角的砂轮在一系列磨削参数条件下磨削QT700材料的阶梯轴,用Thermovision A40M热像仪测量砂轮磨削工件时接触区的平均温度,得出了偏转角α、磨削深度ap、工件轴向进给速度vf和砂轮速度vs在磨削过程中对磨削温度的影响规律,并且比较了在同一组磨削参数下,三种不同θ角砂轮对磨削温度的影响情况。     

Temperature distribution over contact area and “hot spots” in rubbing solid contact

Experiments intended to understand thermal phenomena in a sliding contact were performed and their results are presented. Asperities in contact were found to undergo the pulse effect of the temperature approaching the melting point of one of the friction members. It was noted that the temperature higher than the melting point can be generated in the sapphire–aluminium and sapphire–polyethylene pairs. Temperature distributions over both the contact area and the local heat source are considered.     

Quantification of defects depth in glass fiber reinforced plastic plate by infrared lock-in thermography

The increasing use of composite materials in various industries has evidenced the need for development of more effective nondestructive evaluation methodologies in order to reduce rejected parts and to optimize production cost. Infrared thermography is a noncontact, fast and reliable non-destructive evaluation technique that has received vast and growing attention for diagnostic and monitoring in the recent years. This paper describes the quantitative analysis of artificial defects in Glass fiber reinforced plastic plate by using Lockin infrared thermography. The experimental analysis was performed at several excitation frequencies to investigate the sample ranging from 2.946 Hz down to 0.019 Hz and the effects of each excitation frequency on defect detachability. The four point method was used in post processing of every pixel of thermal images using the MATLAB programming language. The relationship between the phase contrast with defects depth and area was examined. Finally, phase contrast method was used to calculate the defects depth considering the thermal diffusivity of the material being inspected and the excitation frequency for which the defect becomes visible. The obtained results demonstrated the effectiveness of Lock-in infrared thermography as a powerful measurement technique for the inspection of Glass fiber reinforced plastic structures.     

Investigation of disc/pad interface temperatures in friction braking

Maintaining appropriate levels of friction interface temperature is important for the overall operating effectiveness of modern friction brakes, and implicitly the safety of the vehicle. Measurement and prediction of the distribution and magnitude of brake friction interface temperatures are difficult. A thermocouple method with an exposed hot junction configuration was used for interface temperature measurement, and the magnitude and distribution of the friction interface temperature were investigated in this study. Using a designed experiment approach, the factors affecting the interface temperature, including the number of braking applications, sliding speed, braking load and type of friction material were studied. It was found that the number of braking applications had the strongest effect on the friction interface temperature. The real contact area between the disc and pad, i.e. pad regions where the bulk of the kinetic energy is dissipated via friction, had a significant effect on the braking interface temperature. For understanding the effect of real contact area on local interface temperatures and friction coefficient, finite element analysis (FEA) was conducted, and it was found that the maximum temperature at the friction interface does not increase linearly with decreasing contact area ratio. This finding is potentially significant in optimising the design and formulation of friction materials for stable friction and wear performance.     

船舶艉轴机械密封温度场与热变形分析

船舶艉轴机械密封在运转时,密封环端面温度的分布及热变形对密封的泄漏有重要的影响。为了提高机械密封的密封性,采用有限元分析方法,运用整体法和分离法对机械密封的动、静环的温度场、热变形进行分析,研究在不同主轴转速下端面温度的变化情况。分析表明:机械密封端面的最高温度出现在接触区域的中间,并向内、外两侧递减;端面摩擦热与主轴的转速有密切的关系,转速越大,产生热量越多,温度越高;密封环的导热系数也对端面温度也有影响,导热系数越高,端面最高温度会越低;端面热变形量内径处大于外径处。