基于SolidWorks Simulation的球磨机转轴有限元分析

基于SolidWorks三维软件平台,对磁性材料试验球磨机的重要零件之一的转轴进行三维实体建模,利用Simulation有限元分析软件对转轴实现了静态性能分析和疲劳强度分析,得出了转轴的应力、变形分布规律以及使用寿命情况,该分析结果为小型试验球磨机的设计提供了理论依据。     

球头立铣刀铣削加工表面粗糙度仿真技术研究

铣削加工表面粗糙度的形成与铣刀和工件振动、主轴偏心、刀具磨损、刀具变形等物理和几何因素有关。多年来中外学者针对各种影响因素建立了“相对单一”的数学模型。这些数学模型只考虑了一种或两种影响因素,还没有建立起描述物理和几何变化过程的综合数学模型,为此对这些相关因素进行了深入研究,建立了基于球头立铣刀的铣削加工表面粗糙度仿真的整体数学模型。从而为虚拟数控加工仿真提供技术支撑。     

Effect of tool stiffness upon tool wear in high spindle speed milling using small ball end mill

Longer tool life can be tentatively achieved at a higher feed rate using a small ball end mill in high spindle speed milling (over several tens of thousands of revolutions per minute), although the mechanism by which tool life is improved has not yet been clarified. In the present paper, the mechanism of tool wear is investigated with respect to the deviation in cutting force and the deflection of a ball end mill with two cutting edges. The vector loci of the cutting forces are shown to correlate strongly with wear on both cutting edges of ball end mills having various tool stiffnesses related to the tool length. The results clarified that tool life can be prolonged by reducing tool stiffness, because the cutting forces are balanced, resulting in even tool wear on both cutting edges as tool stiffness is lowered to almost the breakage limit of the end mill. A ball end mill with an optimal tool length showed significant improvement in tool life in the milling of forging die models.     

Effect of carbide fraction and matrix microstructure on the wear of cast iron balls tested in a laboratory ball mill

The effect of carbide volume fraction from 13 to 41% on the wear resistance of high chromium cast irons was evaluated by means of ball mill testing. Martensitic, pearlitic and austenitic matrices were evaluated.

The 50-mm diameter balls were tested simultaneously in a 40 cm diameter ball mill. Hematite, phosphate rock and quartz sand were wet ground. The tests were conducted for 200 h.

Quartz sand caused the highest wear rates, ranging from 6.5 to 8.6 μm/h for the martensitic balls, while the wear rates observed for the phosphate rock ranged from 1.4 to 2.9 μm/h.

Increasing the carbide volume fraction resulted in decreased wear rates for the softer abrasives. The almost complete protection of the matrix by carbides in eutectic microstructures caused the eutectic alloy to present the best performance against hematite or phosphate rock. The opposite effect was observed for the quartz sand. The quartz abrasive rapidly wears out the matrix, continuously exposing and breaking carbide branches. A martensitic steel presented the best performance against the quartz abrasive.

With phosphate rock, the wear rate of 30% carbide cast irons increased from 1.46 to 2.84 and to 6.39 μm/h as the matrix changed, respectively, from martensitic to austenitic and to pearlitic. Wear profiles of worn balls showed that non-martensitic balls presented deep subsurface carbide cracking, due to matrix deformation. Similar behavior was observed in the tests with the other abrasives.

In pin-on-disc tests, austenitic samples performed better than the martensitic ones. This result shows that pin tests in the presence of retained austenite can be misleading.     

球磨机联轴器的改造

介绍了球磨机联轴器进行的改造，根据设备的实际情况，通过理论计算，找出所需联轴器的型号尺寸，并介绍应用的情况。     

Modeling and control of ball mill system considering coal moisture

This study analyzes the dynamic characteristics of duplex inlet and outlet ball mill direct firing pulverizing system. A mass and energy balance-based model is built by thermodynamic analysis. As a critical parameter in pulverized coal humidity control, coal moisture is considered in the mechanism model, and an extended Kalman filter is designed to estimate the coal moisture. A multivariable control system is designed using extended state space predictive controller. The dynamic characteristic of the mill can be effectively forecasted using the established model. The system can rapidly track unit load changes while reducing the disturbance caused by coal moisture and other outlets.     

无磨损球形止回阀

论述了无磨损球形止回阀QH44、QH45型的结构、工作原理、性能和特点。介绍了该阀的计算方法。     

Wheel-rail wear simulation

This paper declares the method for the computation of the wheel-rail surface degradation in a curve where the major surface degradation phenomenon is a combination of wear and plastic deformation. Simulating the form change of the wheel-rail contacts help to identify the risk of severe or catastrophic wear resulting from increased train speeds and axle loads and can help in determining more efficient maintenance schedules for track and rolling stock. The method was previously used to simulate the form change in a two-roller contact. The progress is made in the terms of general geometry modelling, which makes differences in the various contact configurations. The normal contact problem is analysed using the modified Winkler method and calibrated using the results from FEM modelling of the wheel-rail contact with elastic-plastic material model. A piecewise approach and stick-slip analysis of the rolling-sliding contact solves the tangential problem. A linear wear law is used in the wear computation. The form change for a typical two-point contact in a low radius curve was analysed and discussed.     

Computer simulation of wear

A digital record of the profile of a machined surface is processed by a computer to yield a number of wear-sensitive parameters such as mean slope and peak curvature. Numerical techniques are used to simulate removal of successive layers of the surface. Wear sensitive parameters are recomputed at each such removal. The results agree with experimental values obtained by a computer analysis of records, obtained by relocation profilometry, of a real wear experiment performed on the same surface. It is found that the variation with depth of wear of several surface parameters can be represented by the normal probability integral.     

Modelling of Coulomb damping and wear of vibrating systems

Coulomb damping is often relied upon to control the response of nuclear boiler tube banks acted upon by fluctuating eddy forces from turbulent coolant flow. The required energy dissipation is affected by relative sliding movements between the clamped joints of the tube and support structure. These movements Z are in general related to the centre span deflection y which is coupled to the exciting forces by the relation

$\text{Z=}\text{∑}\text{n=1}\text{∞}\text{α}{}_{\mathrm{n}}\text{y}{}^{\mathrm{n}}$

where the α_n are termed coupling coefficients. Specific models of the damping are developed for direct Coulomb damping (n = 1) and second-order damping (n = 2) under conditions where a constant friction force, i.e. static loading, is assumed to act. The effects of partial slip across the joint are examined, and this gives rise to a damping contribution at amplitudes that lie below the threshold y_p for gross slip at the joint. In general direct Coulomb damping gives rise to a non-linear type of damping and also changes natural frequency with amplitude. Second-order damping tends asymptotically to a constant loss factor $\text{1}\text{Q}{}_{\mathrm{r}}$ at large amplitudes but in general would be comparable with the hysteretic damping.The penalty from frictional damping is the occurrence of an associated wear rate which can be expressed by

$\text{dW}\text{dt}\text{=}\text{k}\text{μ}\text{dξ}{}_{\mathrm{D}}\text{dt}$

where K is the specific wear rate, ξ_D is the energy dissipated as wear and μ the friction coefficient. Since K and μ are defined by environmental and material properties compatible with nuclear environments, the design should be optimized to minimize the energy dissipation.     

选矿球磨机格子板铸造工艺优化

格子板的普通砂型铸造工艺十分复杂,而且合格率低、铸件难以清理.从模样的制作、涂料的涂敷、浇注系统的确定、填砂紧实、浇注等几个方面详细介绍了用消失模铸造生产格子板类铸件的工艺方法.实践表明,该工艺是生产格子板类铸件的最佳工艺.     

MQG3640球磨机传动齿自动喷油润滑装置

攀钢(集团)选矿厂MQG3640球磨机传动齿将原来干油润滑改为稀油喷雾润滑,提高了润滑效果,降低了劳动强度。对车间的设备维护与管理都非常有利。     

球磨机衬板磨损的分析及应对措施

对球磨机衬板普遍存在的磨损问题进行分析，提出一些注意事项和应对措施，为企业节约设备费用，降低成本和提高经济效益提供合理、实用的经验和方法。     

Modelling of friction and wear for designing cryogenic valves

From a tribological point of view, the selection of materials for seals for valves of cryogenic rocket engines is a critical issue for the designer. Due to the lack of comprehensive information on this topic, data have been obtained in the framework of research programmes.In the first step, two polymers potentially usable for sealing cryogenic fluids were identified. They were submitted to general test conditions to gain some fundamental understanding of their tribological behaviour when immersed in a cryogenic fluid. This fundamental understanding proved to be helpful for an efficient technical approach.This approach with the test conditions as close as possible to those met in real valves has been used in the second step. In order to obtain the best information with the minimum number of tests, the statistical method of Doehlert has been adopted. The use of such a method led to the construction of surface response for modelling friction and wear. These surfaces and their associated equation are directly and easily usable by the designer. This way of treating technical tribological problem is illustrated by an example.     

深沟球轴承磨损失效分析

通过对6308深沟球轴承工作环境、各零件外观检查、理化检查和热处理金相组织检查后发现,该轴承的失效是由于轴承一侧缺少防尘盖,导致杂物进入轴承内部引起轴承磨损而产生的。同时,介绍了轴承的常见失效形式及预防措施。     

Influence of wear on the operational stability of ball bearings

The radial vibrations in a ball bearing due to change in its rigidity on rotation are calculated. Their wear dependence is determined.     

中储式磨煤机制粉系统的自抗扰控制

中储式磨煤机制粉系统是典型的三入三出系统。其具有强耦合。非线性。大惯性的特点。常规的PID很难满足其控制要求。自抗扰控制器是利用非线性控制理论而设计的新型控制器,能实现对被控对象的良好控制。本文利用了自抗扰控制器,设计了基于自抗扰技术的磨媒机制粉系统。仿真结果表明。自抗扰控制器有很强的抗干扰能力和鲁棒性,有很好的使用价值和应用前景。     

Design effects on the fretting wear behaviour of ball bearings

A change in design of a ball bearing is described based on the results of numerical and experimental analysis to reduce fretting wear. Increasing the radii of curvature of the inner and outer races by a small amount reduces the product of the relative slip δ and the tangential traction τ at the contact region, both of which are caused by Heathcote slip. This results in the consequent reduction in fretting wear because there is a good correlation between the amount of fretting wear and τδ. This prediction is confirmed experimentally by increasing the groove radius of the inner race from 4.02 to 4.21 mm for a ball of radius 3.97 mm.     

Study of micro ball end mill geometry and measurement of cutting edge radius

Cutting edge radius plays an important role in conventional micro machining process, as it is of the same order as uncut chip thickness. Therefore it is important to measure the edge radius accurately. There is no recommended methodology, as of now, to measure edge radius of a ball end mill. An attempt is made in this paper to study edge radius of ball end mill at normal and transverse planes on a virtual ball end mill generated using kinematic relations in CAD environment. In the present study, non-destructive methods using confocal microscope and stereo microscope are used to measure edge radius. These measurements capture the edge radius on the transverse plane. For confirmation, the tool sectioned in the transverse plane by a low speed diamond saw is examined under scanning electron microscope and the radius is assessed using suitable software. Among the non-contact approaches proposed in this work, confocal method appeared to be more reliable considering the reproducibility aspect.