共查询到19条相似文献,搜索用时 422 毫秒
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通过测量不同涂层铣刀高速铣削不同硬度淬硬钢材料时的声发射信号和切屑形态,得到了电压-时间声发射信号以及声发射信号RMS值与切削工艺参数之间的关系。研究结果表明:声发射信号与淬硬钢材料硬度、刀具涂层类型及工艺参数有关;声发射信号可用来评价淬硬钢材料硬度的变化,随着淬硬钢材料硬度的增大,采集的声发射信号电压值呈逐渐增大的趋势;TiAlN涂层产生的锯齿形切屑的剪切带长度最小,切屑易于折断,从而导致其产生过程中的声发射RMS值偏小;随着切削速度和每齿进给量的增大,TiSiN、TiAlN、AlCrN和CrSiN四种涂层铣刀的声发射信号均快速增大,而随着轴向和径向铣削深度的增大,4种涂层铣刀的声发射信号变化不明显;在同一种切削参数条件下,可根据淬硬钢切屑变形特征的变化来间接评价刀具涂层的切削性能;声发射信号波形图的峰值大小可较好地反映锯齿形切屑的生成状态,进而可用来监控淬硬钢加工过程切削稳定性。 相似文献
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《机械传动》2018,(12)
启停过程普遍存在于旋转机械设备中,该过程转速的变化对滚动轴承动态性能的影响甚大,然而启停阶段滚动轴承动态特性的研究相对缺乏。以圆柱滚子轴承NU306为研究对象,建立了圆柱滚子轴承非线性接触的三维动态有限元模型。采用显式动力学有限元法对圆柱滚子轴承在不同角加速度和径向载荷条件下的启停过程进行了动态仿真,研究了角加速度和径向载荷两个工况参数对其启停阶段保持架角速度、内圈质心位移,以及所有滚子与保持架接触力等动态特性的影响,并进行了实验验证。研究结果表明,内圈角加速度的增大会加重滚动轴承启停过程的打滑,而径向力的增大会减小滚动轴承启停过程的打滑;在启停阶段,角加速度和径向力愈大,则内圈质心位移以及滚子与保持架接触力越大。仿真结果与实验结果吻合良好,验证了所建立有限元模型的有效性。 相似文献
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PTFE基三层滑动轴承复合材料与不同材料组成的摩擦副有着不同的摩擦学特性,研究这些摩擦副的摩擦学特性,对于优化摩擦副配副材料具有重要的实用价值。研究PTFE基三层复合材料与钢铁材料、有色金属以及聚合物材料进行配副时的摩擦磨损性能,通过扫描电镜观察磨损表面的微观形貌,分析不同摩擦副的摩擦磨损机制,并给出摩擦副配副的优选结果。结果表明:PTFE基三层滑动轴承材料与钢铁材料以及聚合物材料配副时,其磨损机制为剥层磨损,摩擦学性能较好;而与有色金属配副时,其磨损机制为黏着磨损,摩擦学性能较差。 相似文献
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采用40CrMo块试样与316L销试样组成销-块摩擦副,在干摩擦条件下进行摩擦磨损试验,研究整个摩擦磨损过程中磁记忆信号切向分量与试验表面磨损现象以及磨损状态之间的关系。试验结果表明:在摩擦磨损过程中,40CrMo试样表面磁记忆信号出现信号突变,并且突变后的信号可以准确地反应磨痕的长度与位置;整个摩擦磨损过程试样表面磨痕处磁记忆信号切向分量均值随摩擦次数的变化可以分为4个阶段,各个阶段间的转变点分别为点G、点H以及点I,并且通过现场观测、电镜扫描以及能谱分析发现磁记忆信号转变点处试样表面的磨损现象和磨损状态亦发生转变。 相似文献
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针对液膜密封状态监测领域无损监测开发不足、信号特征评估困难以及摩擦状态判别智能化特性缺乏的问题,提出一种基于声发射时频分析与卷积神经网络的液膜密封摩擦状态识别方法。该方法将声发射无损监测技术应用于液膜密封的摩擦状态监测,卷积神经网络作为液膜密封摩擦状态自主决策的实现手段,声发射信号的时频信息作为卷积神经网络的特征输入,分析短时傅立叶变换、 S变换以及小波变换3种时频分析方法对卷积神经网络识别性能的影响。结果表明:对于液膜密封的声发射信号,3种时频分析方法与卷积神经网络结合的优选顺序为:短时傅立叶变换、 S变换、小波变换;基于声发射时频分析与卷积神经网络的液膜密封摩擦状态识别方法准确率较高,相比其他识别方法取得了较好的识别效果。 相似文献
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以刮板输送机可控启动装置液黏传动软启动过程为研究对象,考虑摩擦副表面粗糙度及工作油的离心力,基于平均流量模型求解了油膜厚度及油膜压力的变化规律。基于Greenwood-Tripp接触模型建立了摩擦副粗糙接触压力和转矩方程,利用转矩平衡原理对软启动过程中摩擦副承载特性的时变性进行了分析。结果表明:当启动时间10 s,额定输出转速45 r/min,启动过程遵循S形曲线变化时,油膜厚度按照反S形曲线逐渐减小,并趋于恒定值;油膜压力随时间先增大后减小,且沿径向的分布与启动时间密切相关;摩擦副间压力按照S形曲线增大;负载越大,启动时油膜越薄,摩擦副间压力越大。研究结果为准确地分析摩擦副热特性提供了先决条件,同时也为控制策略的制定奠定了理论基础。 相似文献
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In the present paper, the influence of load and sliding speed on super-low friction of Nitinol 60 alloy was investigated experimentally using Nitinol 60 alloy pin sliding over GCr15 steel disk under castor oil lubrication. Super-low coefficient of friction (COF) of Nitinol 60 alloy was achieved at the stable state, corresponding to so-called superlubricity regime in the presence of castor oil. The experimental results indicate that sliding speed employed in the friction tests plays great roles in the lubrication behaviors of Nitinol 60 alloy. When the friction tests are executed from low sliding speed to high sliding speed, COF decreases at the initial stage and on the contrary, COF increases at the stable stage. However, with the increase in load, COF firstly increases and then decreases at the initial stage. COF is unstable but still super low and remains almost the same value at the stable stage. These phenomena are explained and discussed in viewpoint of the characteristics of castor oil during the friction tests. It is found that the influence of sliding speed on the lubrication behaviors of Nitinol 60 alloy under castor oil lubrication is more obvious than that of load due to the characteristics structure of castor oil, therefore maintaining appropriate level of sliding speed to achieve super-low friction of Nitinol 60 alloy. 相似文献
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机械密封在起停阶段或操作失误时常处于干摩擦状态,由此导致的热损伤与磨损将影响其密封性能。以某YWN8合金接触式机械密封为研究对象,建立基于硬度及磨损系数的磨损数值模型,试验测定摩擦副密封环的硬度、磨损系数、干摩擦因数,验证磨损数值模型的准确性;对机械密封磨损进行仿真模拟,研究摩擦副密封环在干摩擦运转时单力场及热力变形下的磨损深度,并用磨损理论值进行验证。结果表明:干摩擦运转时密封环端面温升较低,温度不是其失效的主要原因;热力变形后密封环内外径间隙增大,造成端面粗糙峰接触面积减小,黏着磨损较变形前呈下降趋势,导致多物理场下的磨损深度与理论值不符。 相似文献
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针对旋转组合密封性能检测问题,设计完成可对直径100 mm的轴用旋转组合密封圈进行密封性能试验的装置。采用PLC控制驱动,实现系统数据采集和压力转速自动调节控制,可对密封件在不同转速、压力下的扭矩、泄漏量等指标进行测试。利用该试验装置对某型号旋转组合密封件进行试验研究,试验结果表明:在定转速情况下,组合密封启动摩擦力矩随压力增加而增加;相同压力下,组合密封圈在低转速情况下,摩擦力矩随转速增加而增加,当转速增加到一定数值后,摩擦力矩增幅出现下降趋势。同时测试结果也表明该装置功能完善,操作简便,自身回转阻力小,在高压下工作稳定可靠。 相似文献
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Dawit Zenebe Segu Polina V. Khan Pyung Hwang 《Journal of Mechanical Science and Technology》2018,32(8):3507-3513
The purpose of this paper is to study methods for enhancing the reliability and performance of hard-disk drives (HDD) because it is essential for improving recording density, speed of data access, and output signal. This study also investigates various techniques that can be used for head/disk contact detection. The acoustic emission (AE) and friction signal characteristics were observed with respect to the durability of the head/disk interface (HDI) under various operating conditions using a contact start-stop (CSS) test. In addition, to study the influence of surface topography on the stiction performance of the HDI, a modified and polished laser pump was proposed and CSS investigations were accomplished. Moreover, the static and dynamic properties of an HDD air slider were studied using a finite element method (FEM). 相似文献
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The friction coefficient is an important factor in fretting fatigue. The frictional behavior of quenched and tempered steel 34CrNiMo6 was studied in smooth fretting point contact with measurements at partial and gross slip conditions. The effect of the start-up scheme is studied by altering the way the displacement amplitude is developed to the target value. This only has a minor effect on the maximum friction coefficient but it does alter the frictional behavior. The friction coefficient increases as tangential displacement amplitude is increased and it has a maximum value of 1.5-1.6 at the transition to gross sliding. 相似文献
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Further investigation of the relationships between friction and wear properties and the characteristics of acoustic emission was conducted in the case of dry and grease-lubricated sliding contact using a ball-on-cylinder testing apparatus. The effect of contamination simulated by the inclusion of glass bead particles was also explored. Experiments were performed at sliding speeds ranging from 0.09 m/s to 1.47 m/s, while maintaining a fixed load and duration. As a first observation and contrary to what could be expected, the higher speed did not contribute to the decrease in friction interpreted by a worsening of the starved regime that had a consequence of increasing wear. However, the results revealed a good correlation between the friction coefficient and acoustic emission (AE) rms voltage for dry sliding. Such a relationship may allow the prediction of a reasonable friction coefficient μ from an AE signal. It was also determined that the friction work correlated well with the corresponding integrated AE voltage over time, intRMS. The detection of the sliding speed threshold beyond which accelerated wear would occur was possible from the intRMS variation. Proportionality between the theoretically determined grease film thickness and the intRMS was observed. 相似文献
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Jong-Tak Kim Jae Sakong Sung-Choong Woo Jin-Young Kim Tae-Won Kim 《Journal of Mechanical Science and Technology》2018,32(1):129-138
Dynamic compression fracture behaviors together with damage mechanisms of materials subjected to a compressive load at a high strain rate were studied by using a Self-organizing map (SOM). The materials used for the analysis were Al5083, Rolled homogeneous armor (RHA) and tungsten heavy alloy (WHA). The deformation behavior and Acoustic emission (AE) signal were acquired through a Split Hopkinson pressure bar (SHPB)-AE coupled test. The self-organization map which is one of the artificial neural network technique was employed to classify the AE energy, amplitude, and peak frequency according to the characteristics of the signal. In addition, distributions of AE signals were represented in stress-strain curves. The correlation between AE characteristics and material damage mechanisms was investigated. Based on the results, it was found that cluster 1 with high AE energy, high amplitude and low frequency was the cluster of the AE signal generated near the yield point of the material. Cluster 3, which has the opposite tendency, was confirmed as a cluster of AE signals that occurred just before a fracture of the material. The change in the measured value can be seen depending on the strain rate and the material, but the overall tendency was similar. 相似文献