With the increasingly harsh service conditions, higher requirements are put forward for the cage of ceramic bearings. In this study, dynamic model of full ceramic ball bearing, in which the motion characteristics of cage is considered, under condition of non-lubrication is established, and the model accuracy is also verified by experiments. The change of contact angles, influence of ball-pocket clearance and guide clearance on the dynamic characteristics of cage are studied. Dynamic characteristics of the cage under different axial loads and rotation speeds are studied. The results show that the influence of rotation speed, radial load and axial load on contact angles are basically the same, while the increase in axial load helps to reduce the difference between internal and external contact angles. With the increase in ball-pocket clearance and guide clearance, the slip ratio of cage decreases first and then increases, so there is an optimal ball-pocket clearance and guide clearance, which makes the cage stable. Compared with the rotational speed, the axial load has a greater impact on the dynamic characteristics of the cage. The results have certain reference value for the optimal design and manufacture of full ceramic bearing cage under non-lubrication conditions.

相比于金属球轴承,全陶瓷球轴承在极端工况下的服役性能更加突出.为了揭示全陶瓷球轴承油润滑特性,提高全陶瓷球轴承的运转性能与使用寿命,以6208CE氮化硅全陶瓷深沟球轴承为例,对其在油润滑工况下所表现出的摩擦、振动、温升等特性进行试验研究,探讨供油量对全陶瓷球轴承润滑状态的影响,并对试验后的全陶瓷球轴承接触微区表层进行解析.研究发现:全陶瓷球轴承油润滑服役过程中,在某个特定工况下存在一个最佳供油量,使得轴承可实现全膜润滑,从而表现出最好的摩擦、振动、温升等特性;小于最佳供油量时,为乏油状态,轴承接触微区存在油-固混合润滑状态;大于最佳供油量时,过多润滑油液会产生的黏滞阻力;相比于载荷,轴承的转速对最佳供油量的取值具有决定性影响.研究成果对于揭示全陶瓷球轴承油润滑特性,丰富其润滑理论与方法具有一定指导意义.

In order to improve the processing accuracy of silicon nitride ceramic balls and to investigate the mechanism of forming ceramic balls by flexible support grinding method, a new cone-type flexible support grinding method with controlled deflection motion of grinding disc is proposed. Based on the new grinding method, a simulation model is established to deeply analyze the influence of the deflection motion of the grinding disc on the grinding trajectory and force state of the silicon nitride ceramic balls. Orthogonal experiments were conducted on a new cone-type flexible support grinding platform built to further analyze the effect of grinding disc motion characteristics on ball formation. Simulation and experimental results show that under the flexible support grinding method, As the increases of grinding disc deflection angle, the standard deviation of ball trajectory uniformity decreased from 43.58 to 35.49, the maximum contact force increased to 4 times the initial value, the average ball diameter variation increased from 1.466 μm to 2.382 μm, and the batch diameter variation increased from 4.98 μm to 10.27 μm. The lower grinding disc deflection motion is beneficial to optimize the grinding trajectory, but increases the unevenness of the ball force, which is not conducive to improving the average ball diameter variation and batch diameter variation of silicon nitride ceramic balls. In the actual process, the angle of deflection of the grinding disc must be controlled to within 0.02°.

For the sake of exploring the thermodynamic characteristics of hybrid ceramic bearings with metal inner rings in the application process, we established the mathematical model of bearings with metal inner rings based on the thermodynamics of bearings. The heat of the bearings, inner and outer raceway, and the deformation of bearings were calculated by the thermodynamic model. We used the bearing life testing machine to test the bearing load and speed. The consequences indicate that the temperature stability time of a hybrid ceramic bearing with the metal inner ring is about 6 hours after loading, and its temperature is about 1-2 degrees C higher than that of a metal bearing. Under the condition of a certain speed, the stable temperature of bearing operation improves with the enlargement of the load. Under the condition of a certain load, the bearing temperature also improves with the enlargement of bearing speed. The overall temperature trend of the bearing outer ring is unanimous with the overall temperature value calculated by the model. The maximum error is between 2.2 and 2.4 degrees C. The thermodynamic analysis of hybrid bearings with metal inner rings is conducive to a better study of the effect of bearing material characteristics on bearing performance.

为探究磨料对氮化硅陶瓷球精研加工的影响,从而提高氮化硅陶瓷球的表面质量和材料去除率,以基液种类、磨料种类和研磨盘转速为主要影响因素设计正交试验,并分析各因素对表面粗糙度Ra的影响程度.以表面粗糙度Ra和材料去除率为评价指标,通过单因素试验优化研磨参数.根据正交试验结果,得到精研加工过程中各影响因素对于表面粗糙度Ra的影响程度,从大到小排列依次为:磨料种类>基液种类>研磨盘转速.综合考虑陶瓷球精研加工的要求,确定最佳的研磨参数组合为:煤油基液、碳化硅磨料以及150 r/min的研磨盘转速.在金刚石、碳化硅、氮化硼、氧化铬和氧化铁这5种磨料中,氧化铁磨料修复粗研过后的氮化硅陶瓷球表面缺陷的效果最好.

A silicon nitride ceramic bearing has good self-lubricating characteristics. It still has a good operational status under the condition of a lack of oil. However, the temperature distribution of a silicon nitride ceramic bearing during its operation is unclear. To clarify the thermal distribution of a full-ceramic ball silicon nitride ceramic bearing under self-lubricating conditions, the changing trend of the rolling friction temperature between the rolling elements and channels with different accuracies is analyzed using the friction testing machine. The bearing heat generation model based on the silicon nitride material coefficient is established, and the life test machine measures the temperature of the bearing to verify the accuracy of the simulation model. The results show that the friction temperature between the ceramic ball and channel decreases with the increase in ceramic ball level. With an increase in the ceramic ball pressure and temperature, the friction temperature rises. Under self-lubrication, when the bearing bears a heavy load, the influence of the rotating speed on temperature rise tends to decrease. Under the condition of high speed, with the increase in load, the change range of temperature rise shows an upward trend. The important relationship between the bearing's heat and bearing's load and speed is revealed. It provides some theoretical guidance for the thermal analysis of a silicon nitride ceramic ball bearing under the self-lubricating condition to improve the service life and reliability of full-ceramic ball bearings.

As a new high-end bearing product, full ceramic ball bearings are favoured in a variety. However, there have been few studies on the lubrication of full ceramic ball bearings. The purpose of this study is to reveal the relationship between the vibration and temperature rise of full ceramic angular contact ball bearings and the lubricant viscosity, and to improve the service life of the bearings. In this study, the effects of lubricant viscosity on the vibration and temperature rise of silicon nitride full ceramic angular contact ball bearings under different axial loads and rotation speeds were tested. Herein, a mathematical model of oil lubrication suitable for full ceramic ball bearings is established and the relationship between the lubricant viscosity, lubricant film thickness, outer ring vibration and temperature rise of the bearing is analyzed. It was found that the vibration and temperature rise first decrease and then increase with the increase of lubricant viscosity. In this range, there is an optimal viscosity value to minimize the vibration and temperature rise of the full ceramic angular contact ball bearing. The contact surface wear of the full ceramic angular contact ball bearing varies greatly under different lubricant viscosities. There is no obvious wear on the contact surface under optimal viscosity, and the service life of the bearing is greatly improved. These results can play an important role in revealing the lubricant mechanism of full ceramic ball bearings and improving their service life under optimal lubrication.

为揭示岩石节理特征下滚刀滚压速度变化对破岩效率的影响,明确滚刀滚压速度与岩石节理特征共同变化下的岩石比能变化规律,采用ABAQUS有限元软件,选择花岗岩为研究对象,建立破岩模型,模拟滚刀滚压速度变化下的破岩过程,分析不同滚压速度与节理特征下滚动力的大小,以及比能变化趋势和破碎效果.试验结果表明:岩石节理间距一定时,滚压速度越大,滚刀所受平均滚动力越大,破岩比能越大;在滚压速度一定时,节理间距从120 mm增至200 mm时,破岩比能增大;岩石节理间距为120 mm时,比能变化平稳;固定岩石节理间距下,节理倾角变大,破岩比能呈现先增大后减小的趋势;当岩石节理间距与节理倾角一定时,滚压速度增大,滚刀平均滚动力增大,比能增大,破岩效率降低.滚刀滚压速度对节理岩石破碎效率有重要影响;节理特征对破碎效率有较大影响.

To improve the grinding efficiency of silicon nitride ceramic balls and save processing costs, the pretreatment of hydrofluoric acid that corrodes silicon nitride was introduced into the grinding process based on the chemical characteristics of silicon nitride ceramics that are not resistant to hydrofluoric acid. This paper mainly discusses the effect of hydrofluoric acid pretreatment on the corrosion and grinding of silicon nitride ceramic balls. Through comparison experiments of grinding silicon nitride balls before and after corrosion, it is found that hydrofluoric acid can effectively destroy the structure and reduce the strength of silicon nitride ceramic on the surface. After pretreatment, the grinding removal efficiency of silicon nitride ceramic balls was significantly improved, the ball diameter variation was reduced, and there was no effect on the properties of silicon nitride ceramic. This processing method is expected to be applied to the mass production of silicon nitride ceramic balls.

Full ceramic ball bearings are widely used in space technology and other cryocooling conditions due to a series of advantages. In order to verify the cryogenic adaptability of full ceramic ball bearings, experimental studies on silicon nitride (Si3N4) full ceramic ball bearings under extreme conditions are carried out, the tribological behavior and vibration characteristics are analyzed. The results show that self-lubricating film will be formed in the bearing, becoming lubricating medium, but the price is excessive wear on cage, indicating that Si3N4 rings and balls have good adaptability to extreme conditions, while the cage is a weak link, and prone to failure damage. The results are of reference value for the application of full ceramic ball bearings under extreme conditions.

为获得全陶瓷角接触球轴承在无润滑条件下内部温度分布,对Palmgren经验公式中的润滑系数进行修正,建立了无润滑条件下轴承摩擦生热模型.研究结果表明,针对于全陶瓷角接触球轴承无润滑生热计算模型中将润滑系数采用油气润滑时的85％ ～95％是合理的,并确定了轴承内部的温度分布;通过修正后的经验公式得到了摩擦热在轴承内部的传递情况,为进一步研究陶瓷球轴承服役性能,提高全陶瓷球轴承的寿命及可靠性提供了理论参考.

Compared with metal ball bearings, full ceramic ball bearings have more outstanding service performance under extreme working conditions. In order to reveal the lubrication mechanism and improve the operation performance and service life of full ceramic ball bearings, in this paper, the friction, vibration, and temperature rise characteristics of 6208 silicon nitride full ceramic deep groove ball bearing, under the condition of oil lubrication, are studied experimentally. Based on the test results, and through theoretical calculation and simulation analysis, the distribution of the lubricating oil film in bearing contact micro-zone under different working conditions was simulated. After that, the surface of contact micro-zone of full ceramic ball bearing was analyzed. It was found that there is an optimal oil supply for full ceramic ball bearing oil lubrication in service. Under the optimal oil supply lubrication, full film lubrication can be achieved, and the bearing exhibits the best characteristics of friction, vibration, and temperature rise. Compared with the load, the rotational speed of the bearing has a decisive influence on the optimal oil supply. When the rotational speed and load are constant, the minimum oil film thickness and oil film pressure in the contact area of the rolling body decrease with the increase of angle ψ from the minimum stress point of the rolling body. Under the action of high contact stress, thin oil film will be formed in the bearing outer ring raceway. In the field of full ceramic ball bearings, the research content of this paper is innovative. The research results of this paper have an important guiding significance for revealing the oil lubrication mechanism of full ceramic ball bearing and enriching its lubrication theory and methods.

In order to reveal the friction properties and improve the wear resistance of silicon nitride ceramic materials, a calculation model of static friction coefficient of silicon nitride ceramic is established. The influence law of contact surface roughness on friction coefficient under different contact load and friction speed is analyzed. The test and the results verification are carried out by using Friction Wear Testing Machine. Then the dry friction process of silicon nitride ceramic is simulated based on UDEC, and the wear failure form is analyzed. In the dry friction process of silicon nitride ceramics, the coefficient of friction is directly proportional to the contact surface roughness, inversely proportional to the contact load, and directly proportional to the friction speed. There is a critical value for the roughness of friction sub-contact surface. Silicon nitride ceramics can self-lubricate by friction when the contact surface roughness is less than this critical value. In the dry friction process, the oxidation of SiO2 has little effect on the friction. The wear surface of silicon nitride ceramics consists of shear failure units and tensile failure units, and their formation is related to the surface roughness. The results play an important role in revealing the frictional properties of engineering ceramics such as silicon nitride, as well as helpful to improve the wear resistance and service life of ceramic materials.

为探究氮化硅陶瓷球研磨过程中的磨料磨损,在Rtec MFT5000摩擦试验机上,用不同载荷及不同浓度的金刚石磨料对其进行磨损试验,用VHX-1000超景深显微镜和S-4800扫描电镜观察磨损表面,确定其磨损形式,绘制摩擦因数的拟合关系曲线图.考虑部分实际工况,建立二、三体磨损模型.结果表明:磨料浓度对磨损形式转变的影响大于载荷.磨料质量分数为5％时出现明显沟槽;质量分数为20％时沟槽较浅;质量分数为35％时几乎无沟槽.计算确定磨损形式的转变临界值D/h≈1.6,当D/h<1.6时,二体磨损逐渐转变为三体磨损,随磨料浓度增大,材料表面磨损程度降低,D/h接近1,在磨料质量分数超过35％时,磨损形式几乎全部转变为三体磨损,试验初始摩擦因数较高随后降低并趋于平稳,不同磨料浓度造成摩擦因数差值较大,不同载荷造成摩擦因数差值较小.减小载荷或增大磨料浓度使D/h减小,能适当降低磨损程度,摩擦因数主要与滚动、滑动磨粒数量有关,滑动磨粒数量越多摩擦因数越大,摩擦因数波动随载荷增大而减小.

According to the characteristics of the tool hydraulic control system of the double cutters experimental pplatform, intelligent control methodology forecasted by fuzzy neural network is introduced into the control system. The two level control systems of fuzzy neural network predictive control and fuzzy control are designed. The fuzzy neural network predictive controller mainly completes the analysis and control of the speed and pressure in the tool hydraulic system. The speed control signal and pressure control signal from the first level are output to the fuzzy controller. Then, through logical reasoning, the control signal is output and the actuator is driven by the fuzzy controller to complete the control function of the tool system. In this paper, compared with the traditional PID control, the fuzzy neural network predictive control technology has better control accuracy, dynamic response performance and steady-state accuracy. The fuzzy neural network predictive control technology can be used to control the tool hydraulic system of Tunnel Boring Machine.

为了研究滚刀旋转速度和贯入速度对含有节理特征岩石破碎效果的影响.利用ABAQUS有限元软件模拟单滚刀破岩过程,分析节理岩石破碎过程产生的应力、应变云图.结果得出:对于节理间距为80 mm、节理倾角为0的岩石,滚刀破岩的最佳旋转速度是2 ra&min;节理倾角为30.时,滚刀的最佳旋转速度为4 rad/min,最佳贯入速度为4 mm/s;节理倾角为60°时,滚刀的最佳旋转速度为3 ra&min,最佳贯入速度为6 mm/s.滚刀的旋转速度对于节理岩石破碎的影响具有不规律性;而滚刀的贯入速度对于节理岩石的破碎具有一定的规律性.在相同贯入速度下,节理倾角为60°的岩石最容易破碎.

This paper studied effects of rock joint characteristics on rock breaking with disc cutter,in order to enhance working efficiency of the full face rock tunnel boring machine( TBM). Disc cutting processes of the TBM with different rock joint characteristics were simulated using the software ABAQUS and the rock breaking results were analyzed. It is found that after joint rock break-ing,the plastic strain in the joint plane extends to the rock inside. With increase of the joint spacing,the rock breaking quantity decreases. Under the condition of the same joint spacing,if the joint orientation angle is 60°,the largest rock breaking efficiency can be obtained; but the efficiency is lowest,when the joint orientation angle is 90°. The joint orientation angle has impacts on the crack propagation of joint rock; but the joint spacing has feweffects. If the joint spacing is in a range of80 ~ 100 mm,it has a significant impact on the breaking efficiency. Conclusion is that the obtained results have a great meaning for understanding the rock breaking mechanism,optimizing structure of the cutter tool system and enhancing working efficiency of boring machines.

目的明确在相同的研磨液配比、磨料类型，不同研磨盘转速、研磨装置施加的载荷、磨粒粒径下的陶瓷球研磨轨迹对陶瓷球表面质量的影响，确定锥形研磨法加工的氮化硅陶瓷球的最优研磨参数，提高陶瓷球的表面质量。方法首先建立研磨盘和氮化硅陶瓷球的相对运动模型，利用MATLAB模拟出不同研磨参数的下氮化硅陶瓷球的研磨轨迹，分析得到研磨参数和研磨轨迹的变化关系；再利用锥形研磨装置进行单因素实验验证，参与实验的三个变量设定为磨粒型号（粒径）、研磨盘转速和研磨装置施加的载荷，将实验结果取样，通过粗糙度仪测量球体表面粗糙度，用扫描电镜和超景深三维显微镜检测研磨后的陶瓷球表面形貌，结合仿真分析和实验结果探究研磨参数对加工后表面质量的影响。结果 将不同仿真轨迹下得到的研磨参数变化规律和和实验结果相结合，得到的最佳研磨参数为：当研磨盘转速为50r/min，施加的载荷为1.30N，磨粒类型为W7，此时陶瓷球表面的粗糙度值为0.0096μm，基本能达到实际生产中对G3级精度全陶瓷球的质量要求。结论陶瓷球的表面质量受研磨盘转速、研磨装置施加的载荷以及磨粒粒径的影响较大，由仿真分析和实验结合可知；研磨过程中随着磨粒粒径的减小，研磨盘转速和载荷的下降，陶瓷球的研磨轨迹趋于稀疏，表面粗糙度值R a 呈下降趋势。研磨氮化硅陶瓷球时取粒径较小的磨粒，以较低的研磨盘转速和较小的研磨装置施加的载荷有利于提高表面质量。本文研究成果对提高陶瓷球的表面质量具有重要指导意义。