共查询到20条相似文献，搜索用时 250 毫秒
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作者用PLINT微动磨损试验机对聚四氟乙烯与不锈钢的摩擦磨损性能进行了研究。考察了滑移速度和载荷对微动摩擦性能的影响。试验结果表明,压应力的大小与聚四氟乙烯磨损的严重程度成正比;摩擦系数随着压应力增大而减小。在无润滑条件下,较低滑移速度对摩擦系数基本没有影响。在有润滑脂条件下,摩擦系数随着滑移速度增大而减小。有润滑脂条件下,使材料磨损大大减小。在干摩擦条件下,纯PTFE板料主要发生粘着磨损和微凸体刨切,磨损机理是粘着磨损和微凸体刨切共同作用。 相似文献
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0Cr18Ni9是一种广泛使用的奥氏体不锈钢材料,其具有非常优秀的抗腐蚀能力。本文研究在不同摩擦参数条件下,0Cr18Ni9的摩擦磨损性能,磨损后材料的形貌以及材料的磨损机制。 相似文献
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研究表明,对于7075铝合金的时效处理会影响7075铝合金的力学性能。本文对7075铝合金在经不同时效时间的T6热处理后,研究其磨损行为的差异。研究在不同摩擦参数条件下,铝合金的摩擦磨损性能,磨损后材料的形貌以及铝合金的磨损机制。 相似文献
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《科技风》2020,(4)
利用MMS-2A型摩擦磨损试验机开展不同介质下轮轨摩擦性能研究,主要研究摩擦系数的变化。研究干摩擦情况下、水态下、油介质润滑条件下、防冻液条件下对轮轨材料的摩擦磨损性能影响,系统分析研究不同条件下轮轨材料的摩擦系数变化。结果表明:不同介质工况下的轮轨摩擦系数明显不同,干态下轮轨摩擦系数最大,水润滑下次之,油润滑下还有所下降,最低的摩擦系数为添加了防冻剂后;随着环境湿度的增加,轮轨摩擦系数明显下降;滑差率对摩擦系数影响显著,随着滑差率增加,轮轨摩擦系数将显著增加;不同流量下,整体变化趋势无明显差异,随着流量的增大,干态与水态工况的状态摩擦系数的转换差异越来越趋于相似,1ml的小流量对摩擦系数影响较大;油介质下摩擦系数较小,随流量的增大,摩擦系数呈现降低趋势。 相似文献
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本文以季戊四醇为例,研究了三种不同化学结构组成的合成脂的摩擦特性。所利用的原理是由于光对弹流实验的干涉,导致合成脂烃链长度增长,加大季戊四醇酯的油膜厚度。在摩擦实验中表明,不同的载物和不同的温度情况下,合成脂的分子链增长会导致摩擦指数降低。同样,跟随实验载物以及实验温度和频率的增长,分成脂的磨损体积大大增加,其抗摩擦性能会变低。本文还会使用设备对研制出的最新合成脂类型的摩擦改进剂进行研究,并与旧型摩擦改进剂的功能进行了一个比较。 相似文献
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油气润滑技术作为一种新型高效的润滑方式,将其应用到滑动轴承当中进行可行性分析试验。在摩擦磨损试验机上对于滑动摩擦副进行了油气润滑与纯油润滑的对比试验。试验就不同工况下温升、摩擦力矩及摩擦系数进行比较,得到了对于滑动摩擦副的润滑效果油气润滑方式要优于纯油润滑。通过试验得出将油气润滑用于滑动轴承是可行的。 相似文献
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齿轮传动的失效一般是指轮齿的失效。常见的失效形式有轮齿折断、齿面点蚀、齿面磨损、齿面胶合以及塑性变形等几种形式。齿面磨损是齿轮在啮合传动过程中,轮齿接触表面上的材料摩擦损耗的现象。齿面磨损一方面导致渐开线齿廓形状被破坏,引起噪声和系统振动;另一方面使轮齿变薄,可间接导致轮齿的折断。齿轮在规定范围内的磨损正常的。齿面的磨损由于齿面间相互摩擦、滑动,研磨或划痕造成的。本文中笔者将分析齿轮齿面的磨损原因及针对磨损采取的措施。 相似文献
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I. Opatowski 《Journal of The Franklin Institute》1942,234(3):239-249
The bases for a theoretical study of wear by friction were given by Th. Reye. Starting from the obvious assumption that the more work done by the friction forces the more material is removed from the worn surface, he was able first to investigate theoretically the mechanics of different types of bearings. The importance of wear by friction is in some mechanical organs, particularly brakes, so great, that the ideas which Reye published 80 years ago still form today the theoretical basis for their design. The present paper is an attempt to go further in these investigations by taking into account two factors which up to now have been neglected: (1) the elastic deformation of the body subjected to wear and (2) the continuous change of its shape in consequence of the wear. The study, which is carried out in a case where the wear effect is particularly evident, the case of brakes, leads to formulas for the determination of the working features of this organ. It explains also in a very clear manner why a certain geometric position of the braking organs is necessary in order to obtain a progressive braking action and why this becomes worse as the wear goes on. 相似文献
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《Journal of The Franklin Institute》2006,343(4-5):372-388
This paper describes a simulation-based parameter design (PD) approach for optimizing machine operating strategy under stochastic running conditions. The approach presents a Taguchi-based definition to the PD problem in which control factors include machine operating hours, operating pattern, scheduled shutdowns, maintenance level, and product changeovers. Random factors include machine random variables (RVs) of cycle time (CT), time-between-failure (TBF), time-to-repair (TTR), and defects rate (DR). Machine performance, as a complicated function of control and random factors, is defined in terms of net productivity (NP) based on three key performance indicators: gross throughput (GT), reliability rate (RR), and quality rate (QR). It is noticed that the resulting problem definition presents both modeling and optimization difficulties. Modeling complications result from the sensitivity of machine RVs to different settings of machine operating parameters and the difficulty to estimate machine performance in terms of NP under stochastic running conditions. Optimization complications result from the limited capability of mathematical modeling and experimental design in tackling the resulting large-in-space combinatorial optimization problem. To tackle such difficulties, therefore, the proposed approach presents a combined empirical modeling and Monte Carlo simulation (MCS) method to model the sensitive factors interdependencies and to estimate NP under stochastic running conditions. For combinatorial optimization, the approach utilizes a simulated-annealing (SA) heuristic to solve the defined PD problem and to provide optimal or near optimal settings to machine operating parameters. Approach procedure and potential benefits are illustrated through a case study example. 相似文献
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在现代机械设计中,三维设计以其直观性而使得传统的二维机械设计逐步向其转化。在设计锚杆机试验台产品时应用三维软件,不仅避免了试制过程中大量的设计更改,而且大大地提高了生产效率,缩短了开发周期。简单介绍了SolidWorks三维软件及应用此软件进行煤炭企业锚杆机试验台设计的过程和方法,希望对此类的设计有一定的参考价值。 相似文献
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本设计是在MGI50（4MG200）系列滚筒采煤机的基础上进行的,保持了原系列采煤机的使用条件、基本结构、技术特征、组成部分和特点,以及相关配套设备.为了使本设计具有更大的适用性,对部分零部件在原性能的基础上进行适当的改进,加强高压水射流发生装置的适用性,使之能给多种机型的采煤机配套使用,以期创造更高的生产效率和经济效益.本设计主要是研究高压水射流在采矿工程上的应用之一即高压水射流采煤机.是在原双滚筒采煤机的基础上引入高压水射流技术,通过改进喷雾方式提高降尘、破煤效果,使之相结合为新型的采煤机. 相似文献
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Measurements were made of the skin friction of various fabrics and surfaces due to interest in the reduction of the skin friction of Zeppelin outer cover.A machine was designed and constructed using Couette type of flow for the purpose of making the measurements. Results obtained with the machine are in general agreement with wind tunnel results.It was found that a smooth surface free from nap, whatever the material, approaches a limiting value for skin friction, and that as a surface becomes smoother any improvement in skin friction becomes increasingly hard to obtain.The results are illustrated by curves. 相似文献
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Pak Kin Wong Xiang Hui Gao Ka In Wong Chi Man Vong 《Journal of The Franklin Institute》2018,355(4):1517-1538
Modern engines are controlled by electronic control units, which operate all the engine actuators based on the signals from various sensors in the engine. Traditionally, the control parameters of the actuators are obtained through huge amount of trial-and-error experiments. However, using traditional approach to calibrate these parameters becomes more challenging with the increasing incorporation of new technologies into advanced engines. In order to reduce the number of experiments required in the calibration process of modern engines, a novel point-by-point engine calibration approach based on machine learning methods is proposed in this study. It is an iterative procedure that, for a given operating point, sequential design of experiment (DoE) strategy is utilized to measure the responses of different engine sensors corresponding to different actuator signals, and a machine learning algorithm called initial-training-free online extreme learning machine is utilized to incrementally learn the relationship between the sensors and actuators based on the measurement acquired. In each iterative cycle, meta-heuristic optimization is performed on the machine-learning-based model to search for the best parameters, which are then used as the initial parameters for generating DoE plan of the next cycle. The iteration is repeated until the optimal parameters of that operating point are found. To verify the effectiveness of the proposed approach, experiments on both simulation engine in commercial software and real engine in test bench have been conducted. The results show that the engine calibration can be carried out with significant fewer experiments and time by using the proposed approach. 相似文献
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Stanley H. Jury 《Journal of The Franklin Institute》1978,305(2):79-98
Classical work on transport in heterogeneous media is reviewed to show the broad interest in it as well as the specific need for a thorough treatment of a more comprehensive model. Such a model is presented and it consists of a random distribution of one or more dispersed phases in a continuous phase. Both the stab and spherical geometry are also considered. Both the transient and steady state transport solutions are developed for each of three different cases. The equivalent diffusivities are extracted from the steady state solutions. Applications are considered to illustrate the validity of the work. It is emphasized that the flux Ji for phase i can be complex as discussed elsewhere in the literature and all of this without any detraction from the exposition presented. It is also pointed out that this exposition is apparently the first to establish the connection between a realistic model, its transient solutions and its steady state solutions from which the equivalent diffusivities have been extracted. In the case of dead-end pores the results suggest application to experimental data to serve as a precision test for the presence and amount of dead-end pores. The advantages of testing under steady state conditions are discussed in detail. An appropriate diffusion cell design is referenced. The results can be useful in the research and design of barrier materials, catalysts, etc. 相似文献
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In this paper, a sliding mode controller (SMC) is proposed for control of a wheeled inverted pendulum (WIP) system, which consists of a pendulum and two wheels in parallel. The control objective is to use only one actuator to perform setpoint control of the wheels while balance the pendulum around the upright position, which is an unstable equilibrium. When designing the SMC for the WIP system, various uncertainties are taken into consideration, including matched uncertainties such as the joint friction, and unmatched uncertainties such as the ground friction, payload variation, or road slope. The SMC proposed is capable of handling system uncertainties and applicable to general underactuated systems with or without input coupling. For switching surface design, the selection of the switching surface coefficients is in general a sophisticated design issue because those coefficients are nonaffine in the sliding manifold. In this work, the switching surface design is transformed into a linear controller design, which is simple and systematic. By virtue of the systematic design, various linear control techniques, such as linear quadratic regulator (LQR) or linear matrix inequality (LMI), can be incorporated in the switching surface design to achieve optimality or robustness for the sliding manifold. To further improve the WIP responses, the design of reference signals is addressed. The reference position for the pendulum is adjusted according to the actual equilibrium of the pendulum, which depends on the size of the friction and slope angle of the traveling surface. A smooth reference trajectory for the setpoint of the wheel is applied to avoid abrupt jumps in the system responses, meanwhile the reaching time of the switching surface can be reduced. The effectiveness of the SMC is validated using intensive simulations and experiment testings. 相似文献
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In this paper a novel type of frictionless mechanical inerter device is presented, where instead of gears, motion of the flywheel is achieved using living-hinges. The design is a type of pivoted flywheel inerter inspired in part by the Dynamic Anti-resonant Vibration Isolator (DAVI) concept, which was first developed in the 1960s. Unlike the DAVI, it will be shown that the pivoted flywheel inerter has the advantage of producing balanced forces. Furthermore the use of living-hinges eliminates the need for gears or other frictional elements in the inerter mechanism. To demonstrate the utility of the new concept, a bench-top experiment was performed using a small-scale living-hinge inerter manufactured using polypropylene hinges. By estimating the experimental system parameters, the transmissibility results from the experiment could be compared to a mathematical model. These results showed that the living-hinge inerter provided an isolation effect of at least three orders of magnitude in terms of the maximum amplitude reduction from the uncontrolled system compared to that with the inerter added. Although friction was eliminated, the living-hinges did introduce additional damping, and this was found to correspond to an increase in the equivalent damping ratio for the uncontrolled system of 1.2%. It is shown that the living-hinge inerter developed in this paper fits all of the essential conditions required to be a practical inerter device. Furthermore, as it operates without mechanical friction, or fluid flow, it represents a new paradigm in experimental inerter technology. 相似文献