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31.
氮化硅陶瓷高温摩擦学性能 总被引:1,自引:0,他引:1
本文研究热压氮化硅陶瓷与3Cr2W8V钢组成的销-盘摩擦副,在空气中非润滑条件下,400~800℃不同载荷(49~343N)的摩擦磨损性能;测定了磨擦系数和Si3N4销的磨损因子;通过对Si3N4磨损面的SEM形貌观察、X射线相结构分析,探讨了陶瓷销的磨损机理 相似文献
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Friction and wear resistance are two vital tribological properties of polymer-based materials but optimization of both is rarely attempted. We have investigated blends of 70 wt% poly(vinylidene fluoride) (PVDF)+30% ultra high molecular weight polyethylene, the latter either un-irradiated or else γ-irradiated. Each sample contained varying amounts of carbon black (CB) and also had a varied degree of crosslinking and irradiation dose. We have determined static and dynamic friction, scratch resistance, and sliding wear in multiple scratching tests. Effects of the irradiation dose and CB concentration have been quantified. The electric conductivity threshold is reflected in a drop of static friction; formation of a continuous phase of the lubricant affects tribology as well as electrical properties—both for irradiated and for un-irradiated samples. The scratch resistance as represented by the residual (healing) depth is affected by crosslinking, by the stage at which irradiation is applied (before or after blending) and by CB addition. Crosslinking by moderate amounts of irradiation provides shallower residual depths while higher doses cause adverse results. Similarly, the CB lubricant can either improve or worsen the scratch resistance. A combination of both approaches produces either better or else worse results than crosslinking alone. Lower friction seems accompanied by higher scratch resistance. A combination of a specific irradiation dose and an optimized CB concentration lowers the sliding wear significantly. Strain hardening in sliding wear determination takes place for all materials studied, irrespective of the extent or radiation-induced crosslinking and of the presence and concentration of carbon black. 相似文献
34.
This paper presents some further results on adaptive sliding mode control (ASMC) for a class of nonlinear systems with bounded uncertain parameters. Given a large initial tracking error, current ASMC design generally produces an unnecessarily large switching gain, consequently leading to a serious chattering problem or a large‐amplitude control jump for the continuous counterpart. To solve such an overadaptation problem, the switching gain adaptation mechanism is first analyzed in this paper, and the adaptation induced by the initial tracking error is suggested to be removed. Then, by exploiting the global sliding mode feature of time‐varying sliding mode control and integral sliding mode control, we present two effective methodologies for ASMC design. The proposed ASMC algorithms ensure that there is no overestimation of the switching gain and the system response is not slowed down when a small switching gain is generated. The validity of the proposed methods is verified by both theoretical analysis and simulation results. Copyright © 2012 John Wiley & Sons, Ltd. 相似文献
36.
翟少将 《安徽冶金科技职业学院学报》2010,20(3):40-42
圆形混凝土护壁结构在水泥生产线中是一种常见形式,如何根据实际施工条件,合理地组织施工,对施工工期、质量、安全、成本都有积极重要影响。对施工中的关键技术和难点问题进行了阐述。 相似文献
37.
朱晓钢 《安徽冶金科技职业学院学报》2010,20(1):18-19
Φ650轧机减速机原设计为滑动轴承,为适应生产需要改为滚动轴承。阐述了滚动轴承选型的设计校核计算。 相似文献
38.
To eliminate the perturbation of interceptor detection induced by aerodynamic heating,the head pursuit (HP) guidance law for three-dimensional interception was presented. The guidance law positioned the interceptor ahead of the target on its flight trajectory,and the speed of interceptor was required to be lower than that of the target. On the basis of a novel head pursuit three-dimensional guidance model,a nonlinear guidance law was developed based on smooth sliding mode control theory. At the same time,a special observer was designed to estimate the target acceleration,and a numerical example on maneuvering ballistic target interception verified the effectiveness of the presented guidance law. 相似文献
39.
文章研究了攻击型无人机鲁棒导引系统,采用对干扰和摄动具有自适应能力的滑动模态变结构控制方法设计了攻击型无人机滑模导引规律.针对用于消除颤振的伪滑动模态不能实现精确跟踪的缺陷,对滑模导引规律中颤振消除进行了优化设计,引入系统运动状态轨迹接近角变量,使消除颤振的伪滑动模态边界层宽度随着系统状态到达滑动模态而逐渐减小为零,从而达到了既能消除颤振又能实现精确跟踪的设计目标.通过仿真验证了该导引规律具有攻击弹道平缓、抗目标机动扰动能力强、鲁棒性好、制导精度高的优点. 相似文献
40.
基于ANSYS的滑动摩擦热结构耦合分析 总被引:1,自引:0,他引:1
利用ANSYS有限元软件分析了在摩擦热和力场的耦合作用下,材料摩擦表面滑动接触区的局部温度变化、应力变化等特性.结果表明:在摩擦滑移过程中,磨损表面相当于接受固定热源作用,接触区温度逐渐上升,温度存在起伏波动现象,温度最高点在接触面中线区域,温度从接触面向四周呈递减趋势,而且温度梯度越来越小;同时,接触应力、摩擦应力也发生变化.滑动过程的热效应问题研究将有助于揭示接触过程中材料表面磨损机理. 相似文献