Modeling and simulation of grinding surface topography considering wheel vibration

Grinding is an important means of realizing precision and ultra-precision machining. Vibration caused by an unbalanced grinding wheel in grinding process has a significant impact on the quality of workpiece surface. However, the effect of wheel surface topography and/or the relative vibration between grinding wheel and workpiece are not considered in most researches. Taking the relative vibration between grinding wheel and workpiece into account, alongside the abrasive grain trajectory equation, a new analysis and simulation model for surface topography of the grinding process is established. The model for the topography of the grinding wheel surface is first studied, and subsequently, a new simulation model for surface topography of the grinding process is proposed. Case studies are performed at the end, and the influence of grinding wheel vibration amplitude, wheel grit number, as well as grinding parameters on the surface waviness and roughness is discussed. The simulation results could be used to optimize the actual grinding process to improve the ground surface quality or predict the surface topography by given grinding parameters.     

超声振动磨削陶瓷的温度场特性研究

采用人工热电偶法,通过普通磨削和超声振动磨削对比实验,对陶瓷材料ZrO2平面磨削的温度场进行了实验研究。并对磨削参数与磨削温度的关系,进行了理论分析及实验验证。结论表明:距磨削表面越远,其磨削温度的峰值越远离热源;增大磨削深度、提高磨削速度和工作台进给速度都会使工件表面温度升高。正交试验表明,磨削深度对温度场的影响较大。普通磨削时工件表层的温度较高,易发生磨削烧伤,采用超声复合磨削能有效降低工件表层温度。     

磨削温度场的有限元模拟及仿真

金刚石砂轮磨削结构陶瓷过程中,所产生的磨削热是影响工件表面质量的关键因素之一,而磨削参数对工件表层温度分布有重要影响。本文采用有限元法,通过两种陶瓷材料对比分析,运用ANSYS软件对磨削温度场进行了仿真研究,利用仿真模型对影响因素作了分析。     

杯形砂轮磨削高硬度球面砂轮磨损的研究

采用分块杯形砂轮磨削高硬度球面,磨削过程中砂轮磨损不仅影响砂轮磨削性能,而且造成工件和砂轮实际接触面积不断产生变化,影响磨削力和磨削质量。为此,基于展成法磨削原理研究砂轮块磨损后的形状变化,分析了分块砂轮的磨损形式,揭示了进给过程中砂轮块磨损形状的变化规律,推导了砂轮磨损量和砂轮工件接触面积的计算公式,分析了砂轮磨损速度的变化趋势及其影响因素,试验最后研究了砂轮磨损量的变化规律,并验证了砂轮磨损量的计算模型。     

氮化硅陶瓷镶块低粗糙度磨削的研究

提出氧化铝砂轮磨削陶瓷表面的加工过程是砂轮磨粒与工件表面凸峰的碰撞－碰撞与摩擦共同作用－摩擦抛光。对砂轮速度，工件转速、砂轮横向进给量、光磨次数，陶瓷材料硬度以及切削液等因素对表明粗糙度的影响进行了分析，表明氧化铝砂轮通过挤压和磨削抛光作用使陶瓷工件表面的粗糙度得到显著改善，实现了在普通磨床上对陶瓷材料的高质量加工。     

Quadratic curve heat flux distribution model in the grinding zone

In order to estimate temperature distribution and the influence of grinding parameters on grinding temperature in the grinding zone, a theoretical model used for calculating and simulating the grinding process must be established. Many simplified heat source models developed previously have some errors compared with the actual heat flux to the workpiece. Therefore, based on the triangular heat flux distribution model and temperature distributions measured, an inverse method for the heat transfer mechanism in the grinding zone was investigated and a quadratic curve heat flux distribution model was developed to determine the heat flux distribution and predict the surface temperature of the workpiece. From the theoretical expression of heat flux to the workpiece, it has been found that the quadratic curve heat flux is the superposition of square law heat flux, triangular heat flux, and uniform heat flux in the grinding zone. By comparison of theoretical analysis with the experimental results, it has been demonstrated that the solution using a quadratic curve heat flux can improve the grinding model by decreasing the error, although the uniform and triangular heat fluxes can explain the condition of the heat flux to the workpiece along the grinding zone.     

叶序排布磨粒对砂轮的磨削温度场效应

在砂轮磨削过程中,磨削热影响工件表面完整性,而磨粒排布是影响磨削温度场的重要因素之一。针对磨粒叶序排布的砂轮,采用有限元法对磨削温度场进行了计算模拟分析,获得了叶序系数对工件磨削温度场的影响规律。研究结果表明,随着叶序排布系数的增大,被磨工件的表面温度和温度梯度减低。     

A hybrid of theory and numerical simulation research for virtual rolling of double-groove ball rings

The analytical thermal model of the grinding process is an important tool for predicting temperature to minimize workpiece thermal damage while improving process efficiency. As more and more numerical models are developed for the grinding temperature research, the established analytical model can be validated with numerical method. A new analytical thermal model of arc moving heat source for rectangular workpiece is deduced, and the temperature distribution results of this analytical model are compared with a validated numerical model. A principle based on the influences of parameters on the analytical and numerical results is proposed for comparing the analytical and numerical model. The comparison result shows that the temperature distribution results agree well on the contact surface, and there are few errors on the finished surface; the significant errors only appear at the boundary between different areas. The established analytical model is validated by the comparison result and can be used for further research about the heat transfer in surface grinding by cup wheel.     

Experimental study of time-dependent performance in superalloy high-speed grinding with cBN wheels

The time-dependent performance of grinding is expressed as the change of process output measures as a function of time during grinding. Although the wheel capability will be restored by dressing, the time-dependent performance of grinding during one dressing skip is the determinant on the grinding quality variation in terms of surface integrity and workpiece geometric accuracy. Therefore, understanding of grinding time-dependent performance in relation with the wheel–workpiece microscopic interaction is critical for wheel and process development to achieve stable grinding processes. In this article, the grinding of superalloy with cubic boron nitride (cBN) grinding wheels is performed. The time-dependent performance is recorded to represent the characteristic features, and the microscopic wheel topography is measured under scanning electron microscope (SEM) throughout the grinding process, so as to reveal the root cause for the time-dependent performance and its impact on the workpiece quality variation. The experiment results indicate that during the grinding process, there exist three characteristic stages, namely, initial wheel wear stage, severe wheel wear stage, and wheel resharpening stage. Moreover, the change trend of spindle power consumption, workpiece quality on surface hardness and roughness, wheel wear condition, and G ratio are consistent with the wheel topography evolution reflected by SEM photos, which can be used to present the three grinding stages. The wear and replacement of the efficient grain cutting edges result in the time-dependent performance during superalloy high-speed grinding with cBN wheels.     

加压内冷却砂轮的研制及磨削性能研究

针对高温合金材料在磨削加工过程中存在磨削烧伤问题,为避免气障效应并强化冷却液在磨削弧区的换热效果,提出采用加压式内冷却断续磨削方法。利用数值模拟方法和3D打印技术对砂轮基体、加压内冷却系统和密封结构等进行设计和验证,制备了用于平面磨削的加压内冷却开槽CBN砂轮。在相同的磨削加工参数条件下,使用加压内冷却方法与外部喷射冷却方法进行镍基高温合金磨削对比试验,分析了砂轮速度、磨削深度和工件进给速度等加工参数对磨削温度、加工表面粗糙度和表面形貌的影响规律,验证了加压内冷却断续磨削方法对磨削弧区的强化换热效果。结果表明：在相同试验参数条件下磨削镍基高温合金,加压内冷却法比外部喷射冷却法的换热效率更高,得到的磨削温度更低,表面粗糙度更小,加工表面更为光滑细腻。     

基于贝叶斯网络的平面磨削状态智能监测技术研究

为解决平面磨削过程中工件表面粗糙度预测和砂轮钝化监测困难的问题,利用贝叶斯网络建立了平面磨削状态智能监测模型。该模型在获取系统磨削用量和工件材料的基础上,在线提取磨削声发射信号的峭度系数,可以有效预测工件粗糙度和识别砂轮钝化状态,为数控系统调节加工参数提供参考。该模型在平面磨床的磨削监测试验中取得了良好的效果。     

Study on the rotary cup dressing of CBN grinding wheel and the grinding performance

A systematic research is conducted to investigate the effect of rotary cup dressing on vitrified cubic boron nitride grinding performance in grinding of nickel-based superalloys. Grinding performance is evaluated mainly in terms of specific grinding energy and radial wheel wear. The number of active grits per unit area and their slope is considered as the two grinding wheel topographical key parameters for studying grinding performance. Cup dressing conditions with various speed ratios and overlap factors were investigated. In each case, the specific grinding energy and the radial wheel wear were experimentally measured, and then the effect of changing dressing parameters on the grinding performance is analyzed. To provide a view on how various parameters influence specific energy and the importance of wheel topography and grit workpiece interaction, a new specific grinding energy model is developed. Inputs to this model are workpiece parameters, grinding process parameters, and, in particular, the grinding wheel topographical parameters. This model is validated by experimental results. The theoretical values considering the complexity of the grinding process reasonably compare with the experimental results. The effect of number of active grits per unit area and their slope on specific grinding energy and then metal removal mechanism is investigated. The results revealed that the number of active grits per unit area has less effect on specific grinding energy than grits slope.     

面齿轮磨削力建模与工艺影响分析

建立了碟形砂轮磨削面齿轮的理论模型.应用切斜面磨削理论,将不规则的曲面齿面等效转化为平面,结合Gleason点接触椭圆等特征,方便对磨削力进行分析求解.将砂轮上的工作磨粒数均匀划分成单颗磨粒成屑力与滑擦力个体,精确阐述砂轮在磨削面齿轮时的磨削力.经过实验结果与仿真数值的比照分析得到磨削力对磨削用量的影响参数,实验结果表明,砂轮转速与面齿轮磨削力成反比例关系,工件进给速度与磨削速度与面齿轮磨削力成正比例关系.通过磨削力的实验结果与仿真数值对比分析,可得出最大相对误差为１７.９％,此数据证明了建立的模型与实验结果较为契合,能够很好地反映磨削力与磨削用量之间的关系变化,在提高面齿轮磨削精度与工艺上提供了基础的理论依据.     

Kinematic simulation of the uncut chip thickness and surface finish using a reduced set of 3D grinding wheel measurements

This paper combined experimentally-measured grinding wheel topography data taken around the entire circumference of the grinding wheel with a kinematic simulation of the grinding process. Several new methods were developed in order to create the resulting high-fidelity and computationally-efficient simulation. First a novel peak-removal technique was developed and applied to effectively remove erroneous peaks in the raw wheel topography data. Next a method was found to determine only the active cutting points on the wheel model by considering the kinematics of the grinding process. This new approach was able to reduce the simulation time from over twelve hours to about four seconds without losing any information about the cutting edge–workpiece interaction. The resulting predicted workpiece surface was then experimentally validated by carrying out a grinding experiment using the same grinding wheel used to develop the grinding wheel computer model and then measuring the resulting workpiece surface profile. Good agreement between simulated and experimental workpiece profiles was observed. Finally, the validated simulator was used to develop a kinematically-exact method to calculate the maximum uncut chip thickness and the simulation results were investigated for different depths of cut, wheel speeds and workpiece feeds.     

曲面圆弧包络磨削表面粗糙度特性研究

对曲面磨削表面粗糙度成型原理进行了分析,得出曲面磨削时其表面粗糙度由磨粒划痕和砂轮两步距间的残留高度构成。探讨了其分布均匀性的原理,揭示了各参数对其均匀性的影响。通过砂轮进给速度的变速控制,可以降低约60%的表面粗糙度波动率。根据理论分析可知,在加工凹曲面时,其理论残留高度值约为凸曲面的两倍。实际加工时,采用较小的砂轮进给步距或砂轮圆弧半径可达到凸曲面的表面粗糙度效果。     

螺旋槽砂轮磨削非光滑表面形貌特征仿真

非光滑表面在机械摩擦磨损的过程中具有减少摩擦和降低能耗的作用。为获得平面工件的非光滑表面,采用磨削加工方式。将砂轮表面修整成螺旋槽形状,并建立螺旋槽砂轮表面的数学模型,根据磨削运动学建立磨粒运动轨迹方程,通过MATLAB仿真研究不同加工参数下磨削表面的形貌特征。     

砂轮约束磨粒喷射精密光整加工材料去除机理研究

基于磨粒特征尺寸与砂轮、工件间液膜厚度比值的变化,研究了砂轮约束磨粒喷射精密光整加工材料去除机理。分析了在两体加工及三体加工模式条件下,单颗磨粒运动特点以及磨粒由两体研磨加工向三体抛光加工转变的临界条件。实验证明,砂轮约束磨粒喷射光整加工中,随着加工循环的增加,工件表面微观形貌变化规律与理论分析相同,实验结果和理论分析吻合很好。     

点磨削工件微观形貌仿真与试验研究

点磨削属于外圆磨削技术的一种,其砂轮与工件轴线之间存在变量夹角α,加工过程中磨粒的运动轨迹发生改变。为探索α对工件表面粗糙度的影响,利用砂轮与工件之间的运动关系及坐标转化,将磨粒运动函数等效为抛物线,得出点磨削的切削路径。基于砂轮表面磨粒分布状态,沿砂轮轴向扩展有效干涉痕迹,得到工件的三维几何仿真形貌。将45钢淬火后作为工件材料,选择典型磨削参数,利用试验对模型进行验证。结果表明:仿真与实际工件微观形貌呈现相似特征,两形貌表面高度概率密度分布十分吻合,在不同磨削速度下,两结果之间平均相差7.8%。当α在0°～4°变化时,Ra的浮动范围小于0.1μm,工件表面粗糙度不会发生明显改变,几何仿真模型为实际磨削工件形貌分析提供了一种辅助和验证方法。     

Force modeling of microscale grinding process incorporating thermal effects

Grinding at the microscale is an essential process in view of its competitive edge over other processes in the fabrication of micro-sized features and parts. The quality of the parts produced by the microscale grinding process can be influenced by various factors related to the mechanical forces induced. Therefore, the predictive modeling of microscale grinding in the context of forces is useful to provide guidance for further development and optimization of this process. In this study, a new model to address mechanical and thermal interactions between the workpiece and an individual single grit on a microscale grinding wheel was developed. This developed model integrates the ploughing and associated friction effects and a moving heat source on the micro-grinding zone under given machining conditions to estimate the thermal effect in microscale grinding process. The ratio of heat partition into the workpiece in the thermal model was also experimentally calibrated using embedded thermocouple measurement followed by analytical calculations. This model quantitatively predicts microscale grinding forces incorporating material properties as functions of strain, strain rate, and temperature. In order to verify this developed model, the experiments based on a surface microscale grinding setup were performed for changing depths of cut. In addition to this, the sensitivity analysis of this model behavior was conducted to identify main effective factors. A comparison between the experiment data and predictions shows that the force model captures the main trend of the microscale grinding physics within the computed range of parameters.     

A new model of grit cutting depth in wafer rotational grinding considering the effect of the grinding wheel,workpiece characteristics,and grinding parameters

Wafer rotational grinding is widely employed for back-thinning and flattening of semiconducting wafers during the manufacturing process of integrated circuits. Grit cutting depth is a comprehensive indicator that characterizes overall grinding conditions, such as the wheel structure, geometry, abrasive grit size, and grinding parameters. Furthermore, grit cutting depth directly affects wafer surface/subsurface quality, grinding force, and wheel performance. The existing grit cutting depth models for wafer rotational grinding cannot provide reasonable results due to the complex grinding process under extremely small grit cutting depth. In this paper, a new grit cutting depth model for wafer rotational grinding is proposed which considers machining parameters, wheel grit shape, wheel surface topography, effective grit number, and elastic deformation of the wheel grit and the workpiece during the grinding process. In addition, based on grit cutting depth and ground surface roughness relationship, a series of grinding experiments under various grit cutting depths are conducted to produce silicon wafers with various surface roughness values and compare the predictive accuracy of the proposed model and the existing models. The results indicate that predictions obtained by the proposed model are in better agreement with the experimental results, while accuracy is improved by 40%–60% compared to the previous models.