磨削加工中滚珠丝杠温度场仿真与实验

螺距精度是丝杠磨削加工的重要指标,累积螺距误差对丝杠定位精度起着决定性作用。砂轮磨削丝杠产生的大量热量通过磨削接触区域按照一定比例传入工件,工件受热伸长而导致的丝杠滚道行程误差会直接反映在螺距误差上。基于若干简化条件,采用有限元法对磨削加工丝杠温度场进行瞬态热分析,并利用红外热像仪构建了磨削加工中丝杠温度测量实验系统,获得了可视化的丝杠热信息,分析了无冷却磨削时工艺参数对加工过程中不同时刻工件温度场分布以及热伸长的影响,有助于丝杠磨削加工的螺距精度控制。     

复杂曲面硬脆材料零件磨削加工数值模拟

建立了大型复杂形面薄壁石英纤维复合材料的树脂金刚石磨削过程传热学模型,并基于有限元方法,利用工程数值模拟软件ANSYS对石英纤维材料磨削时的热传递过程进行了数值计算,得出工件的温度场分布规律及温度变化历程。研究表明：以现行磨削用量干磨削后,磨削最高温度达到316℃,热量主要分布在表层2 mm深范围内,对工件表面材料性能影响不大;同时得到了温度场分布随热源的移动而变化的规律及工件表面某位置下不同深度的温度变化历程。借助有限元方法对工件表层的温度场进行仿真,可以预测整个磨削过程,优化磨削参数,减少试验次数与成本,为解决磨削表面热损伤和热变形等问题提供了依据。     

基于温度匹配法的平面磨削3D有限元仿真及试验

为了准确预测工件表面及亚表面不同深度的温度场变化,基于反热源原理,以实际测量的磨削温度为基础,采用温度匹配法建立适应真实磨削加工时接触区的热源模型。运用有限元法,仿真计算工件磨削温度场的变化,并与瑞利分布热源模型预测结果对比,对工件表面及亚表面不同深度磨削弧区的磨削温度场进行测量。结果表明:基于温度匹配法建立的热源模型模拟的表面及亚表面不同深度温度场与实测值具有很好的一致性,相对误差在3.0%～7.5%,比瑞利热源模型预测的温度场分布精度提高了近2倍。      

用有限元法进行低温磨削钛合金温度场的研究

钛合金的加工性能很差，磨削温度对其磨削性能有重要影响，为了改善钛合金的磨削加工性，分析磨削区温度场分布情况并研究如何有效降低磨削区温度具有十分重要的意义，本文建立了平面磨削时工件的传热学模型，并基于有限元原理，利用工程数值模拟软件ANSYS对钛合金（TC4）工件在常温和使用液氮冷却的低温条件下的磨削情况进行了模拟仿真研究，通过分析不同温度条件下磨削钛合金时的磨削温度场分布情况，表明采用液氮冷却的低温磨削技术可以有效降低磨削区的温度，从而有利于钛合金的磨削，文章最后在常温及低温条件下对钛合金进行了磨削实验研究，验证了仿真分析的结果。     

超声振动辅助缓进给磨削温度场仿真与试验分析

目的通过对比研究磨削过程中超声振动辅助缓进给磨削工件表面的温度变化,验证超声振动对磨削热的影响,为进一步研究磨削机理提供依据。方法基于磨削温度场解析模型,建立了磨削热源平均强度。运用ANSYS软件热分析模块分别对普通缓进给磨削和超声辅助缓进给磨削进行了工件表面温度场仿真,得到了不同载荷步的温度场分布以及工件表面的温度时间变化曲线,较准确地反映了磨削工件时工件表面的温度变化。结果试验和模拟表明,缓进给磨削工件时,工件表面温度较高,对工件施加超声振动后,能够有效降低磨削力,减少磨削过程中产生的热量,降低工件表面温度20%左右。结论超声振动辅助磨削工件时,由于工件高频振动导致磨粒与工件间断性接触,使磨削过程变为有规律的脉冲状断续磨削,有利于工件散热,降低了磨削温度,为避免缓进给磨削时容易出现的磨削烧伤现象提供了技术支持。     

大面积聚晶金刚石复合片电火花加工温度场及应力场的数值模拟

在研究电火花加工机理的基础上,基于有限元原理,建立了电火花连续脉冲放电磨削聚晶金刚石复合片时的物理模型,对磨削过程工件表面的温度场、应力场分布及工件材料的变形规律进行了模拟分析.研究了脉冲宽度及峰值电流对温度场、应力场分布及复合片变形量的影响规律.结果表明,有限元法是分析大面积聚晶金刚石复合片电火花磨削过程中温度场、应力场及变形的一种有效方法,其计算结果可用来指导制定合理的加工工艺参数以提高加工质量和加工效率.     

工程陶瓷高效深磨温度场的有限元仿真

运用有限元法对工程陶瓷氧化铝及部分稳定氧化锆进行了高效深磨磨削温度场的仿真研究。基于磨削温度的实验和传热学理论,得出了工程陶瓷工件的磨削热分配比;得出了干磨及湿磨两种状态下工程陶瓷磨削温度场的分布。分析了磨削温度梯度对工程陶瓷热裂纹的影响。表明随着砂轮线速度增加,磨削温度场温度梯度增大;随着磨削深度增大,不同材料的磨削温度梯度变化不同。磨削温度梯度与磨削热裂纹的产生有一定的对应关系．     

大切深磨削温度场的理论解析

本文推导了基于半无限体表现移动倾斜面热源模型的大切深磨削非稳态温度场，通过计算，结果表明：缓进给磨削温度达到似稳态温度所需时间比高效大切深磨削温度达到似稳态温度所需时间长得多，切深对工件已加工表面磨削温度和磨削弧区内工件表面磨削温度分布有重要的影响。     

基于Deform-3D单粒磨削温度场仿真研究

单颗磨粒切削研究是认识复杂磨削作用的重要手段。基于Deform-3D有限元仿真软件,针对齿轮加工常用的45钢,在工件材料J-C本构模型基础上简化锥形磨粒,分别使用CBN、白刚玉两种不同材质磨料,获得相应的仿真磨削温度场。仿真结果显示:不同材质磨粒点磨削温度差异明显,最高温度接近工件材料熔点温度,磨削温度随着深度增加而增加,随速度增加变化不大。     

断续磨削表面烧伤机理与在线监测方法研究

目的 研究断续磨削烧伤机理和声发射在线监测方法,避免产品磨削加工烧伤现象.方法 基于平面磨削温度场理论和镜像热源方法,建立一种断续磨削工件边缘的温度场模型,基于该模型可对断续磨削烧伤机理进行研究.为验证上述模型的有效性,通过正交实验设计不同断续磨削工况实验,利用红外热成像仪和声发射信号对断续磨削区温度进行在线监测,使用酸洗法和巴克豪森噪声检测仪对磨削后工件表面进行烧伤检测验证,通过对声发射信号的小波包能量求解,建立其与磨削区温度之间的关系.结果 该模型可有效反映断续磨削时工件边缘处磨削区温度场分布情况.计算结果表明,断续磨削工件断口边缘比其他位置磨削区温度更高,且更容易引起烧伤.实验表明,声发射信号的小波包变换总能量与磨削区呈一定相关性,基于声发射信号可对断续磨削烧伤实施在线监测.结论 实验结果证明了该模型对断续磨削烧伤机理分析的有效性,以及利用声发射信号对断续磨削烧伤在线监测的可行性.最后针对某一转向螺母产品实际断续磨削加工烧伤进行在线监测应用,实践结果表明,该方法比传统酸洗烧伤检测更加高效环保,对实现磨削加工烧伤检测自动化和智能化具有重要意义.     

Experimental study on grinding force and grinding temperature of Aermet 100 steel in surface grinding

This paper investigates grinding force and grinding temperature of ultra-high strength steel Aermet 100 in conventional surface grinding using a single alumina wheel, a white alumina wheel and a cubic boron nitride wheel. First, mathematical models of grinding force and grinding temperature for three wheels were established. Then, the role of chip formation force and friction force in grinding force was investigated and thermal distribution in contact zone between workpiece and wheel was analyzed based on the mathematical model. The experimental result indicated that the minimum grinding force and the maximum grinding force ratio under the same grinding parameters can be achieved when using a CBN wheel and a single alumina wheel, respectively. When the phenomenon of large grinding force and high grinding temperature appeared, the workpiece material would adhere locally to the single alumina wheel. Grinding temperature was in a high state under the effect of two main aspects: poor thermal properties of grinding wheel and low coolant efficiency. The predicted value of grinding force and grinding temperature were compared with those experimentally obtained and the results show a reasonable agreement.     

磨削硬化深度预测

磨削硬化是利用磨削过程中产生的热、机械复合作用直接对工件进行表面淬火的新工艺。通过建立磨削温度三维分析模型和热金属效应分析,实现磨削硬化加工工件硬度的预测。基于瞬时温度分布和运动非稳定三维热传导微分方程,并考虑砂轮与工件及冷却液与工件交互作用时热传导情况和材料本身的热扩散,建立了磨削温度三维分析预测模型,结合对加工过程奥氏体相位比例的计算及珍珠岩、残余奥氏体和马氏体的转变等热冶金效应分析,得出磨削硬化加工后硬化深度,实现随加工参数变化的硬化深度分布预测。将此模型与有限元模型进行对比,并通过实验进行了验证。     

平面磨削中工件温度场的直接测温

平面磨削中工件温度场采用红外成像的电荷偶合装置(CCD)测量。在高空问、瞬时条件下红外辐射(IR)温度测量一直是沿磨削试件一侧进行测定试件表面和次表面的温度。用斜面磨削的方法，使磨削深度持续增加，获得了随材料磨除率而改变的磨削温度的变化。这些测量结果与用传统的恒磨除率磨削试验具有良好的相关性。确定了最高温度的位置和值，包括温度梯度。讨论了确定磨削热模型测量的含意及工件的烧伤苗头的预测。     

Thermal Analysis of Grinding

Thermal damage is one of the main limitations of the grinding process, so it is important to understand the factors which affect grinding temperatures. This paper presents an overview of analytical methods to calculate grinding temperatures and their effect on thermal damage. The general analytical approach consists of modeling the grinding zone as a heat source which moves along the workpiece surface. A critical factor for calculating grinding temperatures is the energy partition, which is the fraction of the grinding energy transported as heat to the workpiece at the grinding zone. For shallow cut grinding with conventional abrasive wheels, the energy partition is typically 60%-85%. However for creep-feed grinding with slow workspeeds and large depths of cut, the energy partition is only about 5%. Such low energy partitions are attributed to cooling by the fluid at the grinding zone. Heat conduction to the grains can also reduce the energy partition especially with CBN abrasives which have high thermal conductivity. For High Efficiency Deep Grinding (HEDG) using CBN wheels with large depths of cut and fast workspeeds, preheated material ahead of the grinding zone is removed together with the chips, thereby lowering the temperature on the finished surface. Analytical models have been developed which take all of these effects into account. Much more research is needed to better understand and quantify how grinding temperatures affect the surface integrity of the finished workpiece.     

Heat flux distributions and convective heat transfer in deep grinding

By using experimental data including the monitored temperature and power signals, combined with detailed theoretical analysis, the relationship between the undeformed grinding chip thickness and specific grinding energy has been studied and used to derive the heat flux distribution along the wheel-work contact zone. The relationship between the grinding chip thickness and specific grinding energy (SGE) has been shown to follow an exponential trend over a wide range of material removal rates. The distribution of the total grinding heat flux, q_t, along the grinding zone does not follow a simple linear form. It increases at the trailing edge with sharp gradients and then varies nearly linearly for the remainder of the contact length. The heat flux entering into the workpiece, q_w, is estimated by matching the measured and theoretical grinding temperatures, and it has been found that the square law heat flux distribution seems to give the best match, although the triangular heat flux is good enough for most cases to generate accurate temperature predictions. With the known heat flux distributions of q_t and q_w, the heat flux to the grinding fluid can then be estimated once the heat partitioning to the grinding wheel is determined by the Hahn model for a grain sliding on a workpiece. The convective heat transfer coefficient of the grinding fluid has been shown to vary along the grinding zone. An understanding of this variation is important in order to optimise the grinding fluid supply strategy, especially under deep grinding conditions when contact lengths are large. It has been demonstrated that the down grinding mode can provide a beneficial fluid supply condition, in which the fluid enters the grinding zone at the position of highest material removal where a high convective cooling function is needed.     

Heat flux distribution model by sequential algorithm of inverse heat transfer for determining workpiece temperature in creep feed grinding

The purpose of this study is to determine the heat flux distribution and to estimate the workpiece temperature in creep feed grinding. The sequential algorithm of the inverse heat transfer was used for determining the heat flux distribution. The amount of heat flux to the workpiece, the energy partition and the convective heat transfer coefficients both at the front and at the back of the heat flux were determined. Three heat source models using the determined amount of heat flux were applied to estimate the workpiece temperature. The workpiece temperatures estimated by the heat source models were compared with that measured by the embedded thermocouple. The scalene triangle model correlated best with measured and theoretical temperature profiles obtained for creep feed grinding.