基于ANSYS的磨削热分析中移动热源加载技巧

介绍利用ANSYS进行磨削热分析时移动热源的加载方法,阐述当磨削面为曲面时移动热源的加载技巧,对曲面(如齿轮)磨削过程热状态研究具有指导意义.     

工程陶瓷磨削表面残余应力测试

作为特殊的硬脆工程材料,陶瓷零件的断裂强度和韧性对表面应力状态异常敏感,测试其表面应力有重要意义。 阐述X射线法的测试原理和方法,建立微挠度法的测试模型,介绍压痕裂纹法、剥层法、云纹法的测试原理。比较各种方 法,提出探求一种更精确、更经济、更实用的测量方法是非常迫切的课题。     

磨削淬硬工艺的研究现状与发展趋势

对国外磨削淬硬工艺的研究现状进行系统的概述与分析,指出磨削淬硬工艺研究中尚待解决的问题与发展趋势。     

工程陶瓷磨削表面残余应力的数学模型

作为特殊的硬脆工程材料，陶瓷零件的断裂强度和韧性对表面应力状态异常敏感，建立相应的数学模型是研究残余应力的理论基础。本文阐述了陶瓷材料在磨削过程中的弹塑性变形数学模型，建立了磨削温度模型，介绍了利用磨削参数进行编码的二次回归模型，从而为预测和控制残余应力数值及性质提供指导。     

Transient and residual thermal stresses in quenched cylindrical bodies

To predict residual and thermal stresses which occur during water quenching of solid cylindrical rod and ring cross-sectioned steel tubes, a finite element technique has been used. The variations of residual stresses on different surfaces and cross-sections, e.g. in the radial, axial and tangential directions have been examined, and the effect of internal diameter of tubes on residual stress was investigated. The results show that the residual stresses act as a compressive force along the cooling surface and then by moving away from the surface begin to decrease and reverse their sign, near the centre of the cylinder are subjected to tensile stresses. Because of the reversal of the sign of stress, the effective stress goes to a minimum at some distance from the frontal surface and this may be vital since lower plastic deformation may cause cracking failure. As in solid cylinder, in cylindrical tubes also, the frontal and the upper cooling surface has significant effect on the stress distribution. From the comparison of the residual stress distributions of solid cylinder and cylindrical tubes and using their individual stress maps it was seen that they vary considerably along different cooling surfaces, especially at the frontal surface.     

Roughness due to workpiece wear generated in surface grinding of metals

Assuming the grinding wheel surface to be fractal in nature the maximum envelope profile of the wheel and contact deflections are estimated over a range of length scales. This gives an estimate of the ‘no wear' roughness of a surface ground material. Four test materials, aluminium, copper, titanium and steel are surface ground and their surface power spectra estimated. The departure of this power spectra from the ‘no wear' estimates is studied in terms of the traction induced wear damage of the surfaces.     

Thermal modeling of the metal cutting process — Part II: temperature rise distribution due to frictional heat source at the tool–chip interface

Heat partition and the temperature rise distribution in the moving chip as well as in the stationary tool due to frictional heat source at the chip–tool interface alone in metal cutting were determined analytically using functional analysis. An analytical model was developed that incorporates two modifications to the classical solutions of Jaeger's moving band (for the chip) and stationary rectangular (for the tool) heat sources for application to metal cutting. It takes into account appropriate boundaries (besides the tool–chip contact interface) and considers non-uniform distribution of the heat partition fraction along the tool–chip interface for the purpose of matching the temperature distribution both on the chip side and the tool side. Using the functional analysis approach, originally proposed by Chao and Trigger (Transactions of ASME, 1951; 73:57–68), a pair of functional expressions for the non-uniform heat partition fraction along the tool–chip interface — one for the moving band heat source (for the chip side) and the other for the stationary rectangular heat source (for the tool side) were developed. Using this analysis, the temperature rise distribution in the chip and the tool were determined for two cases of machining, namely, conventional machining of steel with a carbide tool at high Peclet number (N_Pe≈5–20) and ultraprecision machining of aluminum with a single-crystal diamond tool at low Peclet number (N_Pe–0.5). The calculated temperature rise distribution curves on the two sides of the tool–chip interface are found to be well matched for both cases. The analytical method developed was found to be much faster, easier to use, and more accurate than various numerical methods used earlier. Further, the model provides a better physical appreciation of the thermal aspects of the metal cutting process.     

磨削加工技术的现状

综述了磨削加工在机械制造业中的重要地位,提出了高速超高速磨削技术的优越性,阐明了实现高速超高速磨削的理论依据,分析了磨削加工的国内外现状,概述了欧洲、美国、日本等国近十年内的先进磨削技术和高性能磨床,并阐述了国内近几年磨削技术的发展状况。     

On the prediction of the design criteria for modification of contact stresses due to thermal stresses in the gear mesh

The mechanism of surface failure due to temperature rise is a very important problem in gear design. Thermal considerations have received considerable attention from the gear researchers but only for scoring failures when the destruction of lubrication film occurs as a result of temperature rise. In spite of the wealth of literature on this subject, this problem is not fully analyzed.The objectives of this paper are to consider the mechanisms of thermal stresses and the thermal cycling in contact zone, during the gear mesh. This research has been conducted for the first point of contact based on consideration of transient heat transfer, elastohydrodynamic lubrications, and surface roughness and gear material.A procedure presented in this paper evaluating the stresses (thermal and mechanical) and predicting the design criteria for modifying the contact stresses due to thermal stresses. The effect of the material, oil film thickness, surface roughness and geometric operating parameters on modification parameter is illustrated. Also the effects of a load on the temperature rise and the modification parameters are evaluated.     

磨削加工技术的发展趋势

综述了磨削加工的发展趋势,主要包括高速磨削、超高速磨削、精密和超精密磨削、缓进给磨削、高效深切磨削、砂带磨削及绿色磨削技术.分析了超高速磨削加工的机理及超高速磨削的优越性.阐述了高速超高速磨削加工技术的发展前景.     

Thermal modeling of the metal cutting process: Part I — Temperature rise distribution due to shear plane heat source

The model of an oblique band heat source moving in the direction of cutting, first introduced by Hahn (Proceedings of First U.S. National Congress of Applied Mechanics 1951. p. 661–6) for an infinite medium in 1951 and subsequently modified by Chao and Trigger (Transactions of ASME 1953;75:109–20) in 1953 for a semi-infinite medium, is extended in this investigation by including appropriate image heat sources. It is used for the determination of the temperature rise distribution in the chip and the work material near the shear plane caused by the main shear plane heat source in orthogonal machining of a continuous chip. A new approach is taken in that the analysis is made in two separate parts, namely, the workmaterial side and the chip side of the shear plane and then combined. The workmaterial (or the chip) is extended past the shear plane as an imaginary region for continuity to determine the temperature distribution in the workmaterial (or the chip) near the shear plane. The imaginary regions are the regions either of the workmaterial that was cut by the cutting tool prior to this instance and became the chip or will be cut by the cutting tool prior to becoming the chip. An appropriate image heat source with the same intensity as the shear plane heat source is considered for each case. The temperature distributions in the chip and the workmaterial were determined separately by this method and combined to obtain isotherms of the total temperature distribution (and not merely the average temperatures). It appears that the significance of Hahn's ingenious idea and his general solution have not been fully appreciated; instead, an approximate approach involving heat partition between the chip and the work was frequently used (Trigger and Chao. Transactions of ASME 1951;73:57–68; Loewen and Shaw. Transactions of ASME 1954;71:217–31; Leone. Transactions of ASME 1954;76:121–5; Nakayama. Bulletin of the Faculty of Engineering National University of Yokohama, Yokohama, Japan, 1956;21:1–5; Boothroyd. Proceedings of the Institution of Mechanical Engineers (Lon) 1963;177(29):789–810). It may be noted that in utilizing Hahn's modified solution, it is not necessary to make an explicit a priori assumption regarding partitioning of heat between the workmaterial and the chip, as was common in most prior work. Instead, this information is provided as part of the solution. The results obtained with the exact analysis were compared with other methods using the experimental data available in the literature to point out some of the discrepancies in the simplified models. It may be pointed out that these models assume the temperature rise at the chip–tool interface to be nearly uniform and equals the average temperature rise in this volume. A comparison of the calculated temperature rise by these methods with the exact analysis indicates that the differences can be quite significant (50% or higher). It is hoped that future researchers would recognize the significance and the versatility of the exact analysis in determining the temperature distribution in the shear zone in metal cutting.     

刀具产生磨削裂纹的原因及预防措施

通过金相组织观察分析刀具表面磨前裂纹的产生的原因及特征,并采取相应措施,有效地控制了磨削裂纹.     

内锥面刃磨机实现麻花钻螺旋面刃磨的研究与仿真

根据内锥面刃磨机的工作原理,增加双层拖板的差动来代替传统的变导程,利用两步进电机分别带动丝杠主轴与螺母相对转动,合成任意螺距。实现导程可调的新螺旋面刃磨的方法,由此实现了在内锥面刃磨机中进行螺旋面刃磨的方法,并推导了刃磨后后角与横刃斜角的公式。然后基于Pro/E软件设计了机构的虚拟样机,并以双层拖板的分析为例对机构实现螺旋面刃磨而进行运动仿真,结果验证了改进后的机构可以实现螺旋面刃磨。此机构有利于实现数字化控制的机械刃磨。     

磨削加工对象多变时砂轮状态在线监测方法

在磨削加工对象频繁更换的情况下 ,工件的材料、加工要求、磨削条件和磨削参数经常变化 ,使声发射信号的信息也随之发生变化 ,为此提出基于声发射信号多变情况下的归原处理法 ,用于多变磨削加工环境下砂轮状态的在线监测。通过实验验证了该方法的可行性     

残余应力对航空整体结构件加工变形的影响分析

基于理论计算和有限元模拟,研究了毛坯的初始残余应力对大型整体结构件数控加工变形的影响,对单向 应力作用的矩形截面梁在剥层过程中的变形挠度值进行了求解。结果表明,理论解与有限元计算值是一致的。面 向工程应用,采用ABAQUS有限元软件模拟了残余应力对隔框类整体结构件加工变形的影响,并进行了试验验证。 有限元仿真结果与试验数值非常吻合。最后,根据工件加工变形的有限元模拟结果,提出了提高整体结构件制造 精度的工艺措施。     

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.     

不锈钢切削表面残余应力的模拟

建立了正交切削有限元模型,结合热弹塑性理论,利用有限元软件的Lagrange显式程序模拟了切削过程,研究了切削速度、切削厚度、刀具几何参数对AISI 316L钢已加工表面残余应力分布规律的影响,并对比实验结果验证了模型的可行性.     

A study on a cooling method for bone grinding using diamond bur for minimally invasive surgeries

Miniature ball-end diamond wheels are widely used for bone grinding in endoscopic surgeries. During bone grinding, a considerable amount of heat is generated, which can cause thermal injuries to the tissues adjacent to bone, including nerves. In our previous studies, it was revealed that the strong adhesion of bone chips on the wheel surface promotes heat generation. To prevent adhesion, a surface-treated wheel was proposed, and it reduced the temperature elevation. However, we found that the proposed wheel cannot stably suppress the temperature elevation because the wheel effect depends on the coolant supply rate. In this study, a bone grinding method that stably suppresses temperature elevation was investigated. Based on the obtained findings, a cooling method using cold air was developed, and the temperature elevation was stably suppressed under a cold air supply.     

Thermal influence on surface layer of carbon fiber reinforced plastic (CFRP) in grinding

In this study, we investigated thermal influence on surface layer of CFRP in grinding with heat conduction analysis using grinding temperature at wheel contact area on dry and wet condition. Moreover, the thermal affected layer was analyzed through an experiment to examine the temperature of glass transition and thermal decomposition of the matrix resin that composes the CFRP used in this study. The influence of thermal effect on grinding of CFRP was verified based on observation of ground surface finish after grinding using SEM and the measurement of surface roughness. From the measurement result of DSC (Differential Scanning Calorimetry),TG-DTA (Thermogravimetry-Differential Thermal Analysis), It was found that the thermal affected layer of CFRP includes a layer in which the matrix resin is changed in quality by exceeding the glass transition temperature and a layer in which the matrix resin is thermally decomposed by exceeding the thermal decomposition temperature. In addition, it was found that the surface roughness was significantly reduced if the thermal affected layer with thermal decomposition was generated. In each grinding atmosphere, it tended to increase of grinding temperature at wheel contact area with increasing in the setting depth of cut. In the case of dry grinding, grinding temperature at wheel contact area increased up to t thermal decomposition temperature of the matrix resin. However, in the case of the wet grinding, grinding temperature at wheel contact area did not increase until thermally decomposition temperature. From the result of simulation about thermal affected layer, influence of grinding heat increased with increasing in the setting depth of cut. Ultimately, the thermal affected layer with thermal decomposition was generated in dry grinding. Moreover, from the results of SEM observation, it was confirmed that the surface finish properties deteriorated significantly due to thermal decomposition of the matrix resin in the case of Δ = 400 μm in the setting depth of cut at fiber angle θ = 0°. On the other hand, it was confirmed that the micro damage of carbon fiber was occurred in wet grinding at each setting depth of cut.     

金刚石空心磨头结构仿真及试验验证

主要采用有限元软件对金刚石空心磨头磨削工程陶瓷过程中金刚石空心磨头的结构破坏分析,对刀具强度和刚度影响较为显著的壁厚和外径进行仿真,结果表明随着刀具壁厚的增加,刀具整体受到的等效应力明显减小,刀具外径增大的同时磨削力增大,材料去除率增大且刀具较易破坏,最终找出磨削工程陶瓷合理的刀具结构参数。最后利用金刚石空心磨头对工程陶瓷进行加工,金刚石空心磨头未发生破坏。