组合式湿式离合制动器作为压力机传动系统的核心组成部分,其质量性能直接决定压力机能否可靠安全地运行。为研究组合式湿式离合制动器对热模锻压力机工作性能的影响,对热模锻压力机传动系统进行了动力学分析,引入修正的平均流量模型和粗糙接触模型,建立了湿式摩擦副接合过程中传递转矩模型;基于组合式湿式离合制动器液压控制原理,利用AMESim与Simulink联合仿真技术,构建了热模锻压力机传动系统仿真模型。仿真结果表明,通过对组合式湿式离合器活塞油压软离合-硬离合-软制动-硬制动变化的控制,实现离合制动器传递转矩和曲轴行程角度变化。接合压力降低、摩擦盘磨损、制动弹簧力降低均会导致离合器、制动器打滑,进而导致压力机发生闷车、滑块超程等故障,最后,针对此故障原因提出了预防与解决措施。研究结果对实现压力机可靠控制及维护安全生产具有指导意义。

The coupling characteristics of thermal-fluid-solid multi-physical fields are crucial in determining the operational performance and service life of wet clutches. However, the underlying mechanism behind the influence of cavitation effect on these coupling characteristics remains unclear. Therefore, we propose a numerical solution method for considering cavitation effect in the coupling characteristics based on the multi-physical field coupling platform MPCCI combined with ABAQUS and FLUENT. The distribution patterns and intercoupling relationships among temperature field, flow field, and stress-strain field are comprehensively analyze. The influence of relative speed, cross-sectional shape of oil grooves, and oil flow on the coupling characteristics is investigated. Experimental validation confirms that the proposed model accurately predicts temperature variation by accounting for cavitation effect. The temperature distribution of steel discs is notably affected by the cavitation effect, leading to an elevation in the maximum temperature and uneven distribution characterized by localized hot spots along the circumferential direction. Accounting for the cavitation effect reduces errors between calculated and experimental values of temperature rise. The convective heat transfer coefficient gradually decreases radially, with a more pronounced decrease in the cavitation region. An increase in relative speed and a decrease in oil flow both lead to greater cavitation volume, resulting in higher temperature of steel discs. Among three different crosssectional shapes of oil grooves investigated, rectangular grooves exhibit larger areas affected by cavitation compared to triangular grooves. These research findings provide a theoretical basis and technical support for accurate prediction of thermal characteristics within high-power wet clutches.

Thermal buckling deformation can significantly impact the operating performance of hydro-viscous drive. A thermal buckling finite element shell model was established with the nonlinear radial temperature as the thermal loading condition. The thermal buckling behavior of friction pairs was investigated under three different boundary constraints. Moreover, the influence of thickness and material parameters on the critical buckling temperature was discussed. The simulation results coincide with the failure modes of friction pairs in practice, and the most common ones are the coning mode and the potato chip mode. The ability to resist thermal buckling deformation can be improved as the thickness increases. In addition, the steel disc with outer edge simply supported is more prone to thermal buckling, because the critical temperature is minimum. The thermal expansion coefficient is the primary factor in thermal buckling study, which is inversely proportional to the critical temperature. These provide a theoretical basis for avoiding thermal failure of friction pairs in a hydro-viscous drive.

马鞍形屈曲变形是液黏离合器摩擦副最主要的热屈曲变形方式。为获取变形摩擦副的接触特性及温度场分布规律,基于椭球体赫兹点接触理论与屈曲变形规律,建立了摩擦副接触变形等效模型,获得了软启动工况下变形摩擦副接触应力的分布与变化规

A two-dimensional finite element model was developed to investigate thermoelastic instability in multilayered friction discs with finite thickness, considering the deformation modes of the steel core. The model was used to simulate four unstable modes that can occur during the engagement process, and the Fourier reduction was applied to calculate the change in critical speed under these modes. Additionally, the influence of thermal physical parameters, including the elastic modulus, thermal expansion coefficient, Poisson’s ratio, and thermal conductivity of the friction pair, on thermoelastic instability was examined. The findings indicate that the critical speed of the friction pair is lower under the symmetric (friction disc)–antisymmetric (steel disc) mode compared to the other three modes. Consequently, the symmetric–antisymmetric mode is the first to be excited and serves as the dominant mode during thermoelastic instability. Moreover, there exists a specific wave number at which the system exhibits the lowest critical speed and poorest stability. Enhancing the thermal conductivity of the friction disc and steel disc, as well as reducing the thermal expansion coefficient of the steel disc and the elastic modulus and Poisson’s ratio of both discs, can improve the thermoelastic stability of the friction pair. Notably, the thermal expansion coefficient of the friction disc has minimal impact on thermoelastic instability. These results provide a theoretical foundation for exploring the relationship between the thermal failure of friction pairs and rotational speed, as well as optimizing overall performance design. © 2024 by ASME.

为研究不同结构参数对锥形变形摩擦副承载特性的影响,建立不同结构参数下锥形变形摩擦副等效接触模型,采用Ansys Workbench进行屈曲变形仿真,结合Matlab数值模型分析,得到不同结构参数下摩擦副油膜厚度变化规律;基于油膜压力与微凸峰粗

Wear is an inevitable phenomenon in the working process of clutch and brake system. With the increase of transmission speed and power density, the thermoelastic instability (TEI) of clutch and brake system is becoming more serious over time. It is difficult to obtain the practical solution for conventional materials of clutches and brakes and their actual geometry with finite thickness using the existing analytical method. To study the comprehensive effects of wear and friction pair thickness on TEI, Archard Wear Law is combined with the Fourier Reduction Method to develop a finite element model, the accuracy of which is validated using the existing analytical method. Within the usual ranges of thickness and wear coefficient of friction pair, the increase of friction material thickness or the decrease of steel material thickness will suppress the TEI. Nonetheless, if the wear-rate is increased significantly, the effect of friction material thickness will be reversed. The worst thickness, which must be avoided in the design, and the local optimum thickness exist for the steel material.

Hydro-viscous drive has gained extensive application in fans, pumps, belt conveyors, and scraper conveyors for step-less speed regulating, soft starting, and overload protection. In the mixed friction stage, the state of contact and load-bearing capacity are always changing with the pressure of control oil. In order to predict the load-bearing capacity of friction pairs, a description of the frictional and hydrodynamic lubrication states was first made. Oil film's pressure distribution and load-bearing capacity were analyzed with the average flow model. The fractal contact model of the asperity surface was proposed for simulating mutual contact state and contact load between the asperities. The influences of fractal parameters on the contact performance of friction pairs were conducted. Eventually, test rig of load-bearing capacity was established. As indicated by the experiment, asperity contact area and load-bearing capacity of the asperity contact increase slowly at first and then rapidly with reduced film thickness ratio. Correspondingly, oil film load-bearing capacity progressively reduces. Due to the reduction of film thickness ratio, friction pairs' load-bearing capacity increases gradually. The load-bearing capacity of friction pairs is affected by the fractal dimension and scale factor. Results of the experiment well conform to the theoretical values, which illustrates that friction pairs' load-bearing capacity can be accurately predicted and computed using the average flow model and M-B fractal contact model. The calculation offers a theoretical reference to the survey about friction and torque properties of the hydro-viscous drive.
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A finite element model for the effect of wear on thermoelastic instability (TEI) is developed by combining the equations of thermoelasticity, the classical wear law, along with the conforming contact conditions. The method is based on a two-dimensional, frictional sliding model with a bimaterial interface and a simplified geometry of finite thickness. An assumption of the solution in the perturbation form leads to a quadratic eigenvalue problem. The existing analytical solutions for two half planes are employed to validate the numerical solutions for several representative scenarios, including a limiting case in the absence of wear. The analytical solutions are also sought for the special cases when one of the materials is a nonconductor and when the two materials are identical, for the purpose of comparison. In general, good agreements between the numerical and analytical approaches have been obtained. However, the discrepancies exist when the wear rates of the two materials are close to each other and when the wear rates are significantly greater than the critical rate. It is confirmed through this study that wear may suppress or amplify the effect of TEI depending on the thermomechanical properties of the materials, which is consistent with the recent research findings on the same topic via an analytical approach.

为了得到液黏离合器摩擦副的温度场分布特性,在ABAQUS软件中建立了温度场有限元模型,数值模拟计算得到了摩擦副的温度场;搭建了液黏离合器试验台架,得到了不同离合器压力下温度场分布。结果表明,摩擦片和钢片温度从内径到外径逐渐升高,油槽间的菱形区域中心温度比四周高,易形成热斑;摩擦副法向载荷会影响摩擦副的温度值,但对温度场的分布规律影响不大。试验结果与仿真结果基本一致。