Experimental study on ultrasonic-assisted grinding of micro-structured surface on silicon carbide using small diameter grinding wheel

Journal of Mechanical Science and Technology - As an effective machining method for hard and brittle materials, ultrasonic-assisted grinding (UAG) was employed to manufacture microstructures on SiC...     

An active manufacturing method of surface micro structure based on ordered grinding wheel and ultrasonic-assisted grinding

At present, many studies have shown that crosshatch micro structures can effectively improve surface performance. This paper presents a method for manufacturing micro structure based on ultrasonic-assisted grinding (UAG) and ordered grinding wheel. Firstly, the parameters of ordered grinding wheel and the surface characteristic parameters in relation to working performance are proposed. According to the kinematics of grinding, the governing equation between the surface characteristic parameters and the machining parameters is established. Based on the proposed characteristic parameters, the pattern parameters and machining parameters are inversely solved by the governing equation. The crosshatch micro structure manufacturing based on ordered grinding wheel and ultrasonic-assisted grinding is achieved, and because the fabrication technology of the grinding wheel is not mature, its correctness and feasibility are preliminary verified by the numerical simulation method and grinding experiment. The paper method is original for the active manufacturing of the crosshatch micro structure and is of reference value for the micro structure active manufacturing.     

铁氧体陶瓷材料的磨削表面粗糙度试验研究

结合单因素和正交试验全面分析了不同磨削工艺参数及砂轮特性对铁氧体陶瓷的磨削表面粗糙度影响规律,为铁氧体零件的磨削加工提供了依据.     

In-process measurement of surface roughness during cylindrical grinding process

An in-process surface roughness sensor developed by the author has been applied to cylindrical grinding operations. The sensor utilizes fibre optics to illuminate a workpiece surfacec and to detect the intensity of the reflected light. A change of surface roughness during one plunge grinding cycle is measured for various grinding conditions. It is confirmed by the measurements that the surface roughness is closely related to changes of the workpiece radius during a grinding cycle. The result is quite simple and it is useful in determining the cycle time of a grinding operation.     

基于最小二乘支持向量机的外圆磨削表面粗糙度预测系统

为解决磨削加工中影响因素多,难以实现自动化加工的困难,对磨削系统的表面粗糙度预测系统进行了研究。在分析目前常用预测方法的基础上,建立了基于最小二乘支持向量机的外圆纵向磨削表面粗糙度预测模型。该模型采用等式约束,把原来求解一个二次规划问题转化成求解一个线性方程组,方法简单且有效。比较实验显示,该方法响应时间快、测量精度高,测量精度误差比BP神经网络预测方法小4%,比进化神经网络(BP+GA)预测方法小1.3%,所提供的预测方法可以实现对工件表面粗糙度的在线预测。将其应用于外圆纵向磨削智能系统中,实时计算预测值与给定粗糙度的差值,引导磨削专家系统修正磨削参数,实现智能控制,取得了较好的效果。     

A model to simulate surface roughness in the pad dressing process

Pad dressing, which is one of the most important planarization processes, is widely used in CMP. The estimation of surface roughness under various machining parameters (such as dressing force, diamond density of the dresser, rotational speed of the dresser, different machining paths, etc.) is essential to the pad dressing process. In this study, elastic-plastic theory and the wear model are used to construct the expression for the magnitude of material removal as a function of the indentation depth. The deformation of the pad is obtained by using elastic-plastic theory, and the material removal caused by individual micro-contacts is calculated with the help of wear theory. Finally, the macroscopic wear volume is found by summing the volumetric wear of each individual micro-contact. A parametric study is conducted to explore the influence on the surface roughness results and the pad dressing interfacial phenomena of operational parameters. The results reveal that a rapid initial improvement followed by a leveling off, manifesting a saturation effect. Moreover, the model shows that a higher dressing force with a dresser speed close to the pad speed and a moderate translation speed increase the material removal rate corresponding with a lower surface roughness dressing.     

基于全参考彩色图像质量算法的磨削表面粗糙度测量

当前基于机器视觉的粗糙度测量方法使用的图像指标考虑因素少、无参考使得预测模型精度受限、受光源亮度影响大。针对此问题,论文提出了一种基于全参考彩色图像质量算法的粗糙度测量方法。该方法根据粗糙表面成像机理分析,在视觉显著性图像质量评估算法(VSI)的基础上引入结构信息,提出了基于视觉结构显著性(VSIS)的图像质量评估算法,与此同时设计了一套基于图像质量的磨削样块表面粗糙度测量装置。实验结果表明,提出的VSIS图像质量评估算法与表面粗糙度R_a之间存在明显的相关性。使用最小二乘法拟合出的曲线关系,能够对粗糙度大于等于0.965μm的磨削样块进行低离散高精度预测,平均误差为0.111μm,标准差为0.079μm。相比于考虑单一因素的粗糙度关联图像特征指标,VSIS有着较好的综合性能,且能一定程度上克服光源亮度的影响,为非接触粗糙度测量提供可选择途径。     

Some effects of dressing on grinding performance

This paper presents a review of dressing from the work of Pahlitzsch in 1953 up to the present day and concentrates on the single-point diamond dressing of vitreous bonded wheels. Particular emphasis is made of the role of dressing on cutting forces, specific energy, wheel wear and the surface finish of the workpiece. The extent to which an optimum wheel condition is a compromise is discussed together with the practical methods of achieving and monitoring such a condition.     

Study on micro-interacting mechanism modeling in grinding process and ground surface roughness prediction

In the research on grinding process modeling, the stochastic nature of grain sizes and locations need to be considered. A new numerical model was developed which will describe the micro-interacting situations between grains and workpiece material in grinding contact zone. The model was established based on a series of reasonable assumptions, the critical conditions of starting points of plowing and cutting stages, and the redefined grinding contact zone. It indicated that there are four types of grain existing in grinding contact zone: uncontact, sliding, plowing, and cutting grains. The number of grains per unit wheel volume (N _v ) and the undeformed chip thickness (h _cu,max), which are key parameters in grinding process modeling, were firstly obtained. The numbers and distributions of different grain types along grinding contact zone were then obtained and analyzed. Calculation results showed that only a small fraction of grains participate in cutting interactions and the changing laws of each grain types along grinding contact length are very different from each other, which gives a deeper insight into grinding process and can be a good foundation for more precise grinding force prediction and thermal analysis. Another important application of this model is for ground surface roughness prediction and a new method on this purpose was developed. At last, two comparisons were made between calculation results and existing experimental data for validating the work on paper. Comparison results showed that the roughness of ground surface can be well predicted and gave the method theoretically to reduce ground surface roughness.     

Prediction of surface roughness and wavelength with progress of cut in grinding

The topography of a grinding wheel was modeled as a convolution of random waves of large wavelength for the grain and of small wavelength for the cutting edges. The superimposition of these two waveforms gives the “characteristic grain”. On the basis of these concepts, expressions for the roughness and wavelengths, taking into account elastic deflection, were derived for the ground surface along the longitudinal and transverse directions. The fracture and attritious wear mechanisms were used to introduce separate wear rates for the grains and the cutting edges with the progress of cut. These wear rates were used in developing expressions for the roughness and wavelength of the surface generated with the subsequent cuts. Given the wheel type and dressing conditions, predictions obtained from these expressions were validated with the experimental results.     

高速深切磨削陶瓷工件表面粗糙度的在线监测

直接从放在工件夹具上的声发射（AE）传感器测得的磨削加工中的AE信号中,提取有关磨削表面粗糙度的信息,用神经网络的方法对高速深切平面磨削工程陶瓷氧化铝的工件表面粗糙度进行了在线连续监测。结果表明,该新方法不仅简易直接,而且切实可行,通过进一步改进,可以用于高速深切磨削加工工程陶瓷工件表面粗糙度的在线监测。     

基于修整力的树脂结合剂金刚石砂轮机械修整

研究了树脂结合剂金刚石砂轮修整过程中修整力与修整效果的关系,基于修整力的变化表征了砂轮的表面形貌及磨削性能。首先,对碳化硼、碳化硅、白刚玉3种砂轮修整工具进行实验,并采集了修整过程中修整力的变化;然后,利用白光干涉仪观测修整后砂轮的表面形貌;最后,对修整后砂轮进行磨削验证实验,得到不同修整工具修整后砂轮的磨削性能。基于上述实验,分析并验证了修整力的变化与砂轮表面形貌和砂轮磨削性能的关系。结果表明,法向力Fn能够表征砂轮的磨粒切削刃密度以及磨粒突出高度;修整比率β反映了砂轮的锋锐程度,当β稳定时,砂轮达到充分修整。因此修整力反映了砂轮表面形貌和磨削性能,根据修整力的变化可以把握砂轮的修整进程。     

螺旋曲面数控成型磨削与砂轮修整控制研究

提出了一种螺旋曲面磨削加工和砂轮修整控制与协调问题的新方法，解决了砂轮修整时砂轮廓形数据的更新、砂轮半径的补偿等问题。     

The effect of dynamic behavior on surface roughness of ball screw under the grinding force

The dynamic behavior of a ball screw under a moving grinding force and the resulting ball screw surface roughness are investigated. The system includes a ball screw, a headstock, a tailstock, a steady rest, a grinding wheel, and a wheel head. Equations of motion of the system are derived through Lagrangian approach combined with global assumed mode method in this study. The transient responses of the system due to a moving force are evaluated using Runge?CKutta method. Results show that the steady rest can reduce 90% vibration in a grinding process. An equation is proposed to predict the maximum response by the cutting depth. Then we simulate the grain height distribution on the grinding wheel, considering transient response on the ball screw and the grinding wheel. Lastly, the ball screw surface roughness could be simulated via calculating the depth of all working grains. The purpose of using grinding process is that the ball screw needs fine surface roughness. The ball screw surface roughness is influenced by the grain size more than the structure numbers can be.