超高速磨削工艺对45#钢表面磨削温度影响实验研究

在45#钢超高速磨削工艺实验的基础上,分析了砂轮线速度、磨削深度、工作台速度对工件表面磨削温度的影响,揭示了表面磨削温度随着砂轮线速度的提高而呈现先升高后下降的趋势,以及随磨削深度的增加而升高,随工作台速度的提高而下降的规律和机理,从而指导磨削参数的优化设计。     

Modeling of grinding wheel topography based on a joint method of 3D microscopic observation and embedded grindable thermocouple technique

The grinding wheel generally has a complicated topography for the irregularity of abrasive grits, which always has an important influence on the final quality of the grinding workpiece. In this paper, a joint method of microscopic observation and grindable thermocouple technique was adopted to model the wheel topography. The grinding wheel topography was first modeled through microscopic observation by an in-position 3D microscope KH-7700 installed on the grinding machine. Based on the measurement of grit sizes, shapes, and distributions through the 3D microscope, a wheel surface model was established and a static grit number model based on Rayleigh distribution was proposed. Moreover, a numerical model was given to validate the proposed Rayleigh distribution model of an active grit number. In order to investigate the real abrasive grit number in a grinding process, an embedded grindable thermocouple was used to detect the dynamic variation of temperature signals, which will reflect the variation of in-process wheel topography under different process parameters, machine status, and even the grit-workpiece interaction status. Through the experimental analysis, it can be concluded that the increase of depth of cut a_p could help to greatly increase the active grit number to the grinding process, while the increase of workpiece speed V_w and decrease of wheel speed V_s could lead to a subtle increase of the grit number. Moreover, the active grit number is about one fourth to one third of the static grits. The contact arc length between the wheel (CBN) and the workpiece (Ti-6Al-4V) was calculated by the contact time from the workpiece surface temperature data, and it was found that the actual contact arc length was about 1.5~2 times of the geometric size.     

基于ANSYS的平面磨削温度场的有限元仿真

通过确定移动热源的加载方式,运用ANSYS软件的热分析模块对磨削温度场进行仿真分析,得到了不同载荷步的温度场分布以及不同深度的节点的温度变化曲线,验证了越靠近热源磨削温度越高以及工件下层材料温升显著低于工件表面。通过改变砂轮线速度、工件进给速度和磨削深度,得到了主要的磨削参数对磨削区温度场的影响状况,证明了钛合金磨削存在临界磨削速度。在临界磨削速度附近某一区间磨削温度出现回落,因此适当的磨削速度、高的工件进给速度和小的磨削深度可以有效的减小磨削温度。     

一维斜向超声振动辅助磨削滚动轴承钢工艺及试验研究

针对目前只有一维轴向、一维切向等振动方向不变的一维超声振动辅助磨削的情况,首次提出了一维斜向超声振动辅助磨削工艺方法。利用MATLAB对一维斜向超声振动辅助磨削磨粒的运动轨迹进行了模拟分析。建立了超声振动试验系统的动力学模型。通过对超声振动工作台的模态分析,研制了一维斜向超声振动辅助磨削试验系统,对不同角度下超声振动辅助磨削滚动轴承钢的磨削力及表面粗糙度值进行了研究,探究了磨削力及表面粗糙度值随超声振动方向的变化规律。多次试验结果表明,超声振动角度为67.5°附近的表面粗糙度值明显优于其他角度的表面粗糙度值,磨削力也有减小。对正交试验结果的极差分析得出：当超声振动角度为67.5°、砂轮速度为20m/s、工件速度为0.5m/min以及磨削深度为4μm时,加工后的工件表面粗糙度达到最低值,其中工件速度是影响表面粗糙度的最重要工艺参数。     

Effect of parameters on grinding forces and energy while grinding Al (A356)/SiC composites

Abstract

Grinding processes require a high energy input per unit volume of material removed, which is converted to heat at the grinding zone, resulting in increased force and wear. In the present study, the influence of grinding parameters like work speed and depth of cut on grinding forces and energy was studied. An attempt has been made to study the forces and energy involved while grinding aluminium alloy (A356)/silicon carbide (SiC) composite material with different grinding wheels. Experiments were carried out on a surface grinding machine. Three different types of wheels like SiC, cubic boron nitride (CBN) and diamond wheels were used. The grinding forces increased with increase in depth of cut and work speed. SiC exhibited high grinding force compared to the CBN wheel. In the case of the diamond wheel, it was even less. The specific grinding energy was highest for the diamond wheel followed by CBN and SiC wheels. The specific grinding energy decreased with increase in depth of cut and work speed.     

Effects of Abrasive Types on Grinding of Chopped Strand Mat Glass Fiber-Reinforced Polymer Composite Laminates

A grindability study of chopped strand mat glass fiber reinforced polymer laminates (CSM GFRP) has been carried out to evaluate the effects of abrasive types on grinding force ratio and area roughness at varying grinding parameters such as speed, feed and depth of cut. Performances of alumina (Al₂O₃) and cubic boron nitride (CBN) wheels were compared. Both wheels delivered the maximum grinding force ratios at low speed, high feed and low depth of cut. Alumina wheel produced smoother surface when grinding at low speed, low feed and high depth of cut. CBN wheel, on the other hand, gave smoother surface at high feed and low depth of cut conditions, regardless of speed. With CBN wheel, it is likely that a single grinding condition exists that maximizes grinding force ratio and minimizes area roughness. The findings indicate that CBN wheel exhibited higher grinding force ratio than alumina grinding wheel in general. CBN grinding wheel also outperformed alumina grinding wheel by producing smoother ground surface in most cases.     

Experimental investigation of contact behaviour in grinding

The nature of the wheel and workpiece contact in grinding has a strong effect on the temperature, force and surface integrity as well as wheel wear in grinding. An applied power source method was used to measure the real contact length. The interpretation of contact length measurements is discussed. Experimental measurements of contact length in grinding show that the contact length is much larger than the geometrical contact length. This difference is most significant in fine grinding and in the sparkout stage of plunge grinding. The difference also increases when the table speed is increased. The contact length in wet grinding is longer than the contact length in dry grinding. The contact length when grinding cast iron is shorter than the contact length when grinding mild steel. It is found that grinding geometry, grinding force and the roughness of the grinding wheel have independent effects on the contact length. The newly developed contact length model by the authors describes these effects quantitatively. These results also show the importance of the roughness factor, R_r, for analysis of the contact behaviour in grinding processes.     

磨削表面白层厚度影响因素的实验研究

通过淬硬轴承钢GCrl5的磨削实验,研究了砂轮速度、工件速度、磨削深度以及冷却方式等磨削参数对白层厚度的影响规律.实验表明:白层是由磨削过程中工件快速升温和快速冷却以及强烈的塑性变形引起的,白层厚度的变化是磨削加工过程中各种参数共同作用的结果,而其中磨削深度是主要原因,其次是砂轮速度和工件速度;白层厚度随砂轮速度和磨削深度的增大而增大;低的砂轮速度和磨削深度以及良好的冷却条件能有效抑制白层的产生.根据实验统计结果提出了预测磨削白层厚度的经验公式.     

高速精密磨削9CrWMn冷作模具钢的磨削力和比磨削能

分析了高速精密磨削9CrWMn冷作模具钢的机理,采用DEFORM软件对高速磨削模具钢9CrWMn过程进行了磨削力仿真。使用高精密高速平面磨床对模具钢9CrWMn进行了高速精密磨削试验,并在线测量了多种工况下的磨削力。结果表明:在其他两组工艺参数不变时,随着工件进给速度增加,磨削力特别是法向磨削力会增大近45%;法向磨削力和切向磨削力随着砂轮的线速度上升而下降,法向磨削力下降近33%;磨削深度对磨削力影响较大,大的磨削深度对法向磨削力的影响尤其显著,可使法向磨削力增大近100%。分析了磨削工艺参数对比磨削能的影响规律,结果显示:随着磨削深度和工件进给速度的增大,比磨削能呈比较明显的下降趋势,符合磨削加工中的尺寸效应;随着砂轮线速度的增大,比磨削能呈上升趋势。最后,对高速磨削前后工件表面的微观形貌进行了对比分析,磨削力试验结果和仿真理论分析相一致。     

不锈钢超高速磨削试验研究

为避免不锈钢磨削中发生砂轮堵塞,减轻磨削烧伤的程度,提高加工效率,优化加工工艺,对不锈钢进行超高速磨削试验研究。在高速/超高速磨削条件下,研究了不同砂轮线速度、工件进给速度和进给量对不锈钢磨削的磨削力、表面粗糙度和表面形貌的影响作用,并检测了不同工况下的砂轮表面状态。研究结果表明,不锈钢在超高速磨削状态下,选择合理的工作台速度和磨削深度能有效提高加工效率,同时又能保证磨削质量。
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Constrained grinding optimization for time,cost, and surface roughness using NSGA-II

Selection of parameters in machining process significantly affects quality, productivity, and cost of a component. This paper presents an optimization procedure to determine the optimal values of wheel speed, workpiece speed, and depth of cut in a grinding process considering certain grinding conditions. Experimental studies have been carried out to obtain optimum conditions. Mathematical models have also been developed for estimating the surface roughness based on experimental investigations. A non-dominated sorting genetic algorithm (NSGA II) is then used to solve this multi-objective optimization problem. The objectives under investigation in this study are surface finish, total grinding time, and production cost subjected to the constraints of production rate and wheel wear parameters. The Pareto-optimal fronts provide a wide range of trade-off operating conditions which an appropriate operating point can be selected by a decision maker. The results show the proposed algorithm demonstrates applicability of machining optimization considering conflicting objectives.     

椭圆振动修整超声磨削ＺrＯ２温度试验研究

采用椭圆超声振动辅助金刚石笔修整方法修整金属结合剂金刚石砂轮,考察声学系统参数及磨削参数对超声振动辅助磨削纳米氧化锆陶瓷过程中磨削温度的影响.试验结果表明,椭圆超声振动辅助修整的金刚石砂轮超声振动磨削中,磨削温度相对较低.相比其他修整参数,修整深度对磨削温度的影响较小.磨削参数中,磨削深度对磨削温度影响因子较大,砂轮速度影响较弱.此外,磨粒在切削过程中做超声振动,改变了切削条件及散热条件,弱化了砂轮表面地貌对磨削温度的影响,因此,不同修整方式的金刚石砂轮的磨削温度差别不大,两种修整方式下磨削温度下降的梯度大致相当.     

Ants colony algorithm approach for multi-objective optimisation of surface grinding operations

An ant colony based optimisation procedure has been developed to optimise grinding conditions, viz. wheel speed, workpiece speed, depth of dressing and lead of dressing, using a multi-objective function model with a weighted approach for the surface grinding process. The procedure evaluates the production cost and production rate for the optimum grinding condition, subjected to constraints such as thermal damage, wheel wear parameters, machine tool stiffness and surface finish. The results are compared with Genetic Algorithm (GA) and Quadratic Programming (QP) techniques.Nomenclature a _p down feed of grinding (mm/pass) - a _w total thickness of cut (mm) - A _o initial wear flat-area percentage (%) - b _e empty width of grinding (mm) - b _s width of wheel (mm) - b _w width of workpiece (mm) - B _k positive definite approximation of the Hessian - doc depth of dressing (mm) - c _d cost of dressing ($) - c _s cost of wheel per mm³ ($/mm³) - CT total production cost ($/pc) - CT ^* expected production cost limit ($/pc) - d _g grind size (mm) - D _e diameter of wheel (mm) - f _b cross feed rate (mm/pass) - G grinding ratio - k _a constant dependent on coolant and wheel grind type - k _u wear constant (mm^-1) - k _c cutting stiffness (N/mm) - k _m static machine stiffness (N/mm) - k _s wheel wear stiffness (N/mm) - L lead of dressing (mm/rev) - L _e empty length of grinding (mm) - L _w length of workpiece (mm) - M _c cost per hour labour and administration ($/h) - N _d total number of pieces to be grouped during the life of dressing (pc) - N _t batch size of workpieces (pc) - N _td total number of workpieces to be grouped during the life of dressing (pc) - P number of workpieces loaded on the table (pc) - R _a surface roughness (µm) - R _a* surface finish limit during rough grinding (µm) - R _c workpiece hardness (Rockwell hardness number) - R _em dynamic machine characteristics - S _d distance of wheel idling (mm) - S _p number of spark out grinding (pass) - t _sh time of adjusting machine tool (min) - t _i time of loading and unloading workpiece (min) - T _ave average chip thickness during grinding (µm) - U specific grinding energy (J/mm) - U ^* critical specific grinding energy (J/mm³) - V _r speed of wheel idling (mm/min) - V _s wheel speed (m/min) - V _w workpiece speed (m/min) - VOL wheel bond percentage (%) - WRP workpiece removal parameter (mm³/min-N) - WRP ^* workpiece removal parameter limit (mm³/min-N) - WWP wheel wear parameter (mm³/min-N) - W _i weighting factor, 0W _i1 (W ₁+W ₂+W ₃=1)     

基于响应曲面法的轴承钢GCr15高速外圆磨削参数优化

为充分发挥轴承钢GCr15优越的材料性能,保证GCr15轴承等产品的加工质量和加工效率,开展了高速外圆磨削参数优化研究。选用立方氮化硼（CBN）砂轮进行GCr15的高速外圆磨削响应曲面试验,根据试验结果建立磨削力、磨削温度、变质层深度等磨削结果的回归模型。结合回归模型与磨粒的最大未变形切屑厚度模型,综合分析砂轮线速度、工件速度、磨削深度等磨削参数对磨削结果的影响规律。以磨削结果综合最小为目标,进行磨削参数的多目标优化,通过试验验证优化模型和优化结果的正确性。     

An experimental study on the grinding of alumina with a monolayer brazed diamond wheel

A monolayer diamond grinding wheel was fabricated by brazing in vacuum. The wheel was then used to grind alumina at three different grinding speeds. The horizontal and vertical grinding forces, and the grinding temperatures were measured during grinding. SEM observations were made for the ground workpiece surfaces. The influences of the peripheral wheel speed on the grinding forces, specific grinding energy and grinding temperatures were analyzed under different combinations of depth of cut and workpiece velocity. The dependence of the average grinding force per grain and specific grinding energy on the maximum undeformed chip thickness was discussed respectively. It was found that an increase in the peripheral wheel speed reduced grinding force, but increased force ratio, specific grinding energy, and grinding temperature.     

Selections of working conditions for creep feed grinding. Part(I)–thermal partition ratios

A thermal model focused on the heat transfer to the fluid, workpiece and grain is developed for creep feed grinding. In this model, the conduction effect in the moving direction of the workpiece is considered which is found to be very significant especially for creep feed grinding. Moreover, the thermal partition ratios to the workpiece, fluid and grain are well defined and discussed. The results reveal that the cooling effect of the fluid is more crucial especially at larger grinding depth and smaller workpiece speed. Furthermore, the promotion of the wheel speed is helpful to reduce the fraction of heat entering the workpiece. Also, the workpiece thermal partition ratio is greatly influenced by the workpiece speed. Its value is even less than 5% as the workpiece speed is smaller than 4 mm/s. Comparing the thermal partition of wet grinding to that of dry grinding, the abrupt increase of heat entering the wheel and workpiece due to the occurrence of boiling in the fluid is verified.     

超高速磨削温度的实验研究

用人工热电偶方法对40Cr和45#钢的超高速磨削温度做了深入的实验研究.发现提高砂轮线速度,工件的磨削温度随之升高;但从某一速度开始继续提高砂轮线速度,磨削温度却呈明显下降的趋势.这就预示超高速磨削温度较低,适合磨削.同时对超高速磨削的比磨削能进行了研究,表明大切深超高速磨削是可行的,发现40Cr钢的超高速磨削性能优于45#钢.     

滚珠丝杠磨削再生颤振稳定性极限预测

滚珠丝杠磨削过程中再生颤振对提高工件质量和生产效率有很大影响。在对滚珠丝杠磨削振动系统建立动力学模型的基础上,推导计算出机床再生颤振系统极限磨削深度与砂轮转速的计算公式及绘制出颤振稳定性极限预测图。最后,通过实验结果验证了该颤振稳定性极限预测模型的有效性和实用性。     

Genetic Algorithm (GA) for Multivariable Surface Grinding Process Optimisation Using a Multi-objective Function Model

A genetic algorithm (GA) based optimisation procedure has been developed to optimise the surface grinding process using a multi-objective function model. The following ten process variables are considered in this work: wheel speed, workpiece speed, depth of dressing, lead of dressing, cross-feedrate, wheel diameter, wheel width, grinding ratio, wheel bond percentage, and grain size. The procedure evaluates the production cost and production rate for the optimum grinding conditions, subject to constraints such as thermal damage, wheel-wear parameters, machine-tool stiffness and surface finish. A worked example is used to illustrate how this procedure can be used to produce optimum production rate, low production cost, and fine surface quality for the surface grinding process.     

Research on surface integrity of grinding Inconel718

Inconel718 is widely used in the aerospace industry; the finished surface quality has significant effect on service performance of component. The surface integrity in grinding Inconel718 respectively by using a vitrified bond single alumina (SA) wheel and a resin cubic boron nitride (CBN) wheel were investigated. First, effects of different grinding parameters on grinding temperature and grinding force and grinding chips feature by using a SA and a CBN wheel respectively were investigated. Then, the surface roughness and topography by using a SA and a CBN wheel through single factor experiment were compared, and in the grinding parameters range of the present study, the better surface can be obtained by a SA wheel. Finally, surface integrity by using a SA wheel and the different grinding depth was studied and analyzed by the grinding temperature and the grinding force. It was possible to conclude that better surface can be achieved by using a SA, and taking a _p?=?0.005 mm, v _w?=?16 m/min, v _s?=?25 m/s for grinding Inconel718. In this grinding case, the surface roughness was Ra0.112 μm, the surface residual stress was +700Mpa, and the surface hardness was 440 HV; the depth of residual stress layer was 40～60 μm, the depth of softened layer was 30～40 μm and the depth of plastic deformation layer was 10～15 μm.