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1、湖 北 文 理 学 院毕业设计(论文)英文翻译题 目 有限元热分析的陶瓷离合器专 业车辆工程班 级Xxx姓 名Xxxx学 号2010138xx指导教师职 称Xxx 副教授2014年2月25日Fethermal analysis of a ceramic clutch1. IntroductionAbrasive dry running vehicle clutches are force closure couplings. Torque and speed transmission are ensured by the frictional force generated between t
2、wo pressed surfaces. Reasons for the application of ceramic as a friction medium include good heat and wear resistance properties, which provide the opportunity to drive higher pressures, and a low density. Thus, an increasing power density is enabled with a parallel minimization of construction spa
3、ce.Measurements with a first prototype of a clutch disk using ceramic facings were performed at Karlsruhe University in a laboratory specialized in passenger car drive system testing. In the course of analysis the finite element (FE) model was to be constructed with the knowledge of measurement data
4、 and measurement conditions. Calculations were intended to determine the temperature distribution of the clutch disk and its environment at each moment in time corresponding to measurements. It is essential to be familiar with the temperature range in order to examine the wear characteristics of the
5、 system. Thus, important information is derived from measurement data. In critical load cases, the highest expected temperatures must be forecast in space and time in order to protect measuring instruments close to the location of heat generation.The goal of this study is to analyze and modify the c
6、lutch system to provide better operating conditions by improving the heat conduction and convection of the system or to increase the amount of the energy converted into frictional heat. Furthermore, it is desired to find better design solutions for more efficient clutch systems.Calculations were per
7、formed by the Cosmos Design Star software. During model development, great care had to be taken for proper simplification of geometry, the selection of element sizes, and the correct adjustment of time steps due to the substantial hardware requirements for transient calculations. Changes in thermal
8、parameters such as the surface heat convection coefficient and thermal load had to be taken into consideration on an on-going basis in terms of time and location. The two sides of the analyzed test clutch system can only be managed by two independent models linked by heat partition, according to the
9、 hypothesis that the contact temperature must be identical on both sides while there is proper contact between them and its value must be adjusted by iteration. Calculations revealed that the heat partition changed by cycle and it differed along the inner and outer contact rings. As a result of the
10、different cooling characteristics between the ceramic and steel side, a heat ow is launched from the ceramic side to the steel side. This heat flow was also determined by iteration, its value also changes by cycle and differs along the inner and outer contact rings.2. First prototype of a clutch usi
11、ng engineering ceramics as friction material The examined clutch disk was developed according to the “specific ceramic” product development process established at the Institute for Product Development (IPEK) at the University of Karlsruhe. This development process already has the possibility for con
12、nection to a real transmission shaft; further, it has a cushion spring device for the facings allowing good start behaviour. Abrasive clutches must comply with the following basic requirements:l high torque transmission according to high friction coefficients,l high comfort (no vibrations through se
13、lf-induced chattering),l homogeneous temperature distribution,l low wear characteristic.A critical element of the switch is the abrasive disk.With regard to the design utmost care must be taken to select the right material. A high and constant friction coefficient,，wear resistance and thermal resist
14、ance are desired characteristics. The clutch disk has instead of the generally applied ring-shaped abrasive inlet two rows of SSIC (as sintered) ceramic pellets. These pellets are placed on 6 separate segments. The segments are xed to the central hub by rivets. Each segment consists of 4 plates, 2 w
15、orking as facing springs and 2 as carriers.3. Measurements Measurements were performed at the department of power train development of the Institute for Product Development (IPEK) at the Karlsruhe University (TH) Research University, where a category IV component test rig is used for tests of new fr
16、ictional materials and examinations of new materials in real clutch disks. Real conditions are applied by the simulation of driving resistance (e.g. starting in the plane, starting at the hill). It is a component test rig leveled on the fourth position of the tribological testing environment.In orde
17、r to give an idea of dimensions: the equipment length is about 4-5m. The two electric motors and the axial force are controlled independently by computer; thereby many operational states can be realized. This enables the equipment to complete a myriad of tribological measurements all while properly
18、modeling the operation of a clutch disk in a passenger car. It is also equipped with an automatic IT measurement system. Measurable quantities include the following:l two heavy-duty electric motors (150 KW, Baumuller DS 160L-305),l device suitable for exerting axial force,l torque meter (Manner Sens
19、ortelemetrie MF100),l axial force meter,l steel disk in friction,l replaceable head to affix the device to be tested,l temperature along two different radii at 0.4mm below the abrasive surface of the steel disk (Omega HJMTSS-IM100U-150-2000,J-typeiro-constantan thermocouples),l revolutions per minut
20、e for both sides (Polytene LSV 065).The greatest challenge out of these is temperature measurement as we would like to know the temperature of the revolving steel disk. The two thermoelements placed in the steel disk forward data to the computer through a wireless blue tooth system and are placed 0.
21、4mm below the abrasive surface of the steel disk on the two opposite arcs of the clutch disk.3.2. Measurement processDue to component analyses and cost reduction only one side of the clutch disk is mounted with ceramic facings. Thus, the clutch disk and its fitting will be referred to as the ceramic
22、 side, and the abrasive steel disk with its environment revolving together will be referred to as the steel side. In the course of measurements, data were collected at a sampling frequency of 100 and 1000HZ. Measurements were conducted according to the time curves.The measurement starts by increasin
23、g the revolutions per minute of the steel side (the driving side) to a specific value (1500 rpm here). Then the ceramic side (the driven side), held at zero rpm, is pushed towards the steel disk and the axial force is applied until a designated value is reached (nominally 4200N here). Upon reaching
24、the designated axial force the ceramic side is released and the two sides start to synchronize. A few seconds after synchronization, the axial load is discontinued and after some time both the steel and the ceramic sidesrevolving at the same speedare slowed down. This is deemed to be one measurement
25、 cycle. Ten cycles are completed in the course of a single measurement. During application of the axial force the ceramic side is held at zero rpm until the desired force is reached to ensure synchronization occurs at nearly the same time of each cycle. This is unfavorable from the viewpoint of both
26、 measurements and calculations. Measurements are usually conducted by changing only 3 parameters: the speed, the axial load and the inertia. The following figures are applied in various combinations:l speed n: 700, 1100 and 1500 (rpm),l axial force F: 4200, 6400 and 8400 (N) andl inertia I: 1, 1.25
27、and 1.5 (kgm2).Experimental measurements are launched with approx.10-15 min intervals, during which the system cools down to about 30-40 1C. This makes calculations difficult, as the exact temperature distribution of the system is not known at the commencement of the measurement. However, it can be
28、assumed that a period of 10-15min is sufficient for a nearly homogeneous temperature distribution to be produced. The parameters for the following simulation have been chosen for an intermediate case with a speed n =1500 rpm, an axial force F = 4200 N and an inertia I = 1 kg m2.4. Calculations of he
29、at generation The mechanical energy consumed during the friction of two bodies is transformed into heat. The generated heat can be calculated by the following simple formula: Q =F W . where m is the the frictional coefficient; v is the sliding velocity; F is the force perpendicularly compressing the
30、 surfaces. And the heat flux density per surface unit is q=p Wm2. where p is the the pressure calculated as a ratio of the force and the contacting surface. As the ceramic tablets are placed at two different radii along the clutch disk, the heat generated must be calculated separately for each radii
31、. Sliding can be divided into two sections. In the first section, the ceramic side is kept in a stationary position by braking, meanwhile the axial load is increased; therefore compression changes in the course of time while the speed difference between the two sides is constant. In the second secti
32、on (at synchronization) the speed difference is equalized while the force value is constant, so velocity changes in time. On the basis thereof, the heat generated is .The nominal contact area is the aggregate of the contacting surfaces of the 24 and 18 ceramic tablets on the given ring. The diameter
33、 of ceramic tablets is: .Calculations were performed for the load case to be characterized by the following parameters: .Based on experimental measurements a constant friction coefficient of 0.4 was established. .The velocity can be calculated with the knowledge of the radius and the speed. .Surface
34、 pressure can be calculated as a ratio of the axial force and the contacting surface. This produces the same figure for each ceramic pellet, assuming an even load distribution. . Thus, the maximum values of the generated heat are .In the first section of sliding, the generated heat is rising due to
35、the increase of the load force; in the second section, it is decreasing due to the equalization of the speed difference. It is necessary to know the time of each sliding section in order to be able to specify the generated heat time curve. These can be determined from measurement data series. Synchr
36、onization time can be easily determined from the speed of the ceramic side. Speed increase is linear. Force increase is non-linear. For the sake of simplicity, force increase was substituted by a straight line in calculations so that the area below the straight line is nearly identical with the area
37、 measured below the curve. Thus, the time difference between the two terminal points of the straight line is the time of the first sliding section. The above-mentioned method was applied for each cycle and their average was specified. Based on these results, the following values were determined for
38、sliding times: .Now the time curve of heat generation can be produced. The same curve was used in each cycle as there were no significant differences between parameters in each cycle. The generated heat-calculated this way-will appear as thermal load in the thermal model. It must be distributed appr
39、opriately between the contacting surfaces by taking into consideration heat partition. Heat partition requires the contact temperatures to be identical at both surfaces. Correct adjustment requires repeated iterations.有限元热分析的陶瓷离合器1 引言 磨料空转车辆离合器是力封闭联轴器。扭矩和高速传输被压紧表面之间产生的摩擦力所保证。应用陶瓷是因为它作为摩擦介质具有好耐热和耐磨损性
40、能，提供了机会以驱动更高的压力，以及一个低的密度。因此，一个提功率密度启用了一个平行的最小化建筑空间。 测量使用陶瓷饰面离合器盘的第一个原型在卡尔斯鲁厄大学的一个实验室专门从事客车驱动系统进行了测试执行。在分析过程中的有限元（FE）模型是将与测量数据和测量条件的知识所构成。计算的目的是要确定在离合器盘上温度的分布以及环境中的在每一时刻的及时测量目。至关重要的是熟悉的温度范围，为了检验该系统的耐磨特性。因此，重要信息从测量数据中得出。在临界负载的情况下，预计最高温度必须在时间和空间上进行预测，为保护接近发热体的位置测量工具的。本研究的目的是分析和修改该离合器系统通过改进，以提供更好的工作条件热传
41、导和系统或增加转化成摩擦热的能量的对流。此外，人们希望找到更有效的更好的离合器系统设计方案。计算是由宇宙星空的设计的软件进行的。在模型开发阶段，非常谨慎，必须采取几何元素，选择适当的简化尺寸，并且由于正确调整的时间步长大量的硬件要求瞬态计算。热物性参数的改变，如表面热对流化系数和热负荷，必须考虑到到在一个持续的基础上在时间和地点方面。离合器系统的分析测试这两方面，只能通过加热隔板连接的两个独立的模型来管理，根据该假说认为，接触温度必须是在两个相同的双方，同时他们要有适当接触，其价值需通过迭代来进行调整。计算显示，该热分区按周期变化，它沿不同的内，外接触环。在不同的冷却特性下，在陶瓷和钢之间的结
42、果是不同的 ，热流从陶瓷侧面向钢侧流动。此热流也通过迭代确定;它的价值也改变了周期和不同沿着所述内和外接触环。2 采用工程陶瓷作为摩擦材料的第一个原型机这款检查过的离合器盘是根据“ 特定的陶瓷”产品而开发的，此材料的研发过程在流程在卡尔斯鲁厄大学的Institute for Product Development (IPEK)杂志上发表过。此开发过程已经具有的可能性，用于连接到一个真实的传动轴；甚至，它为面板有一个好的初始行为起到一个很好的缓冲作用。磨料配件必须符合以下基本要求：1. 根据高摩擦系数高扭矩传递2. 高舒适度（通过自感应抖动无共振）3. 均匀的温度分布4. 低磨损特性开关的一个关
43、键因素是摩擦面.在设计极限方面，必须谨慎采取选择合适的材料。高而恒定的摩擦系数，耐磨损和耐热性是理想的特性。离合器圆盘能代替通常 应用环形磨料入口两排SSIC的（烧结）陶瓷颗粒。这些小球被放置在6个单独的段位。该段由铆钉固定到中心轮毂。每个段由4片组成，2个工作面对着弹簧和2个作为载体。3 测量3.1 测量设备 测量是在卡尔斯鲁厄大学（TH）研究型大学的动力传动系完成的，同时也是用于测试新的摩擦材料和新材料在实际离合器片中检测的地方。真实情况是通过驱动电阻的仿真应用（例如，开始在平面上，开始于山）的试验装置。这是一个组件试验台夷为平地在摩擦测试环境的第四位。为了给维度的概念：设备长度大约4-5
44、m 。两台电动机和轴向力是由计算机独立控制;因此许多运营可实现的状态。这使得设备来完成一个摩擦学测量无数，而所有正确建模在乘用车上的离合器盘的操作。它还配备用自动的IT测量系统。可测量的量包括以下内容：1. 2个重型电机（150千瓦，Baume米勒DS160L-305）2. 设备适用于施加轴向力3. 扭力计（Sensortelemetrie MF100）4. 轴力计5. 钢盘的摩擦6. 可更换的头部贴上设备进行测试7. 温度沿两个不同的半径处为0.4mm以下的钢盘（欧米茄HJMTSS-IM100U-磨料表面 150-2000，J铁康铜热电偶）8. 每分钟转数为双方（Polytec LSV065
45、）。这里最大的挑战是这些我们想知道的旋转钢盘面上温度的测量。两个热元件放置在钢盘通过无线蓝牙数据转发给计算机系统和被放置为0.4mm以下的研磨面钢盘上的两个相对的圆弧的离合器盘。3.2 测量过程为了测量由组分分析和降低成本的一侧离合器盘安装用陶瓷衬片，由此，离合器磁盘及其配件将被称为陶瓷侧，而磨具钢盘与它的环境一起旋转会简称为钢侧。在测量时，数据的过程中收集在100和1000Hz的采样频率。在测量开始通过增加每转钢侧（驱动侧）的分钟为一个特定值（这里是1500转）。然后在陶瓷侧（驱动侧），在保持零转速下被推向钢盘和轴向力应用，直到一个指定的值为止（名义上4200N在这里）。当到达所指定的轴向力
46、的陶瓷侧是释放和双方开始同步。几秒钟在同步之后，在轴向载荷终止和后一段时间都在钢和陶瓷两侧绕转在相同的速度会慢下来。这被视为一个测量周期。十个周期中的一个过程中完成单次测量。在应用程序中的轴向力陶瓷侧被保持在零转速，直至所需的力达到以确保发生同步于几乎每种相同的时间周期。这是不利的从两者的观点出发，测量目和计算。测量通常通过进行仅改变3个参数：速度，轴向载荷和惯性。下面的数字是应用于各种组合： 1.转速n：700 ，1100和1500（RPM）2.轴向力F： 4200 ，6400和8400（N）3.惯量I：1 ，1.25和1.5（ kgm2为单位）实验测量与约推出,10-15分钟的时间间隔，在
47、此期间，系统冷却到约30-40摄氏度。这使得计算变得很困难，因为确切的该系统的温度分布是不知道的开始测量。然而，可以假定经过一段时间的10-15分钟就足够了一个几乎均一要产生的温度分布。下面的模拟已经选择了一个中间的情况下用转速n=1500转，一轴向力F=4200N和一个惯量I=1kgm2。4 计算两个摩擦过程中所消耗的机械能体被转化成热量所产生的热量可计算由下列简单的公式：Q =F W，其中为摩擦系数， v是滑动速度， F是垂直压缩表面上的力。和每单位表面的热通量密度q=p Wm2，其中p是计算的力的比率的压力和的接触表面。作为陶瓷片被放置在两个不同的半径沿离合器盘，所产生的热量必须分别计算每个半径。滑动可分为两部分。在第一部，所述陶瓷侧被保持在一个固定的位置由制动，同时在轴向负荷增大，因此在时间的过程中压缩的变化，而速度双方的差异是恒定的。在第二部分（在同步）的转速差进行均衡,而力值是恒定的，所以在时间的速度变化。基础物所产生的热量是： 名义接触面积是24的接触表面的聚合和18陶瓷平板电脑在给定的半径。陶瓷小块的直径是:计算进行了负荷情况的特点是以下参数:基于实验测量的恒定摩擦0.4系数成立。速率可以通过速度和半径的知识来计算： 表面压力可以计算为轴向力的比率和接触表面。这产生相同的数字的每个陶瓷颗粒，假设即使负载分布。则有： 这样的话，最大的集中热值就是： 在滑
