基于射流支撑薄壁件镜像加工尺寸误差补偿设计

低刚度薄壁件在切削加工过程中因切削力而容易产生切削变形和切削振动等尺寸误差,对薄壁件产生尺寸误差的影响因素进行分析,并针对薄壁件在切削过程中因受切削力作用而产生尺寸误差,设计了一种应用水射流镜像加工薄壁件的新型加工工艺方法,以此减小薄壁件的尺寸误差。最后,通过实验验证了水射流镜像加工技术可有效的提高薄壁件的加工精度。     

高速超声振动切削的最佳主偏角适用范围

为了研究高速超声振动切削过程中主偏角对切削力的影响,建立了高速超声振动切削的理论模型。首先分析了高速超声振动切削在不同主偏角下的切削力分布,然后计算了不同切削区域的切削厚度和单位切削宽度,以及四个金属切削变形区的切削力,最终建立了高速超声振动切削在0～90°主偏角下的切削力模型。理论和实验结果表明,对于主切削力而言,主偏角变化范围为20°～55°时,高速超声振动切削主切削力小于常规切削主切削力;对于进给抗力而言,主偏角适用范围为15°～40°;对于吃刀抗力而言,主偏角适用范围为15°～45°。为了使高速超声振动切削的切削效果达到最好,最佳主偏角适用范围为20°～40°。     

超声振动车削TC4钛合金的切削性能研究

为了探究超声振动车削过程中切削力和切削温度的变化规律,使用Third Wave Advant Edge切削仿真软件,基于POWER-LOW本构模型和ALE网格划分方法建立TC4钛合金车削加工的有限元模型,获得传统车削与超声振动车削的切削力和最高切削温度变化情况。结合超声振动车削中刀具切削速度和位移变化规律,对传统车削与超声振动车削的切削力和最高切削温度变化规律展开对比分析;探究超声振动车削中的工件进给速度、刀具振频和振幅对切削力的影响规律,实现各加工参数的最优组合,为实际加工提供参考。     

细长轴工件切向成形车削法

如图1所示的细长轴(长度≥5倍直径)工件,承受切削力非常小,采用普通车削法或径向成形车削法,车削时容易产生弯曲和振动。而切向车削法,能对廓形深度较小和刚性差的细长轴工件进行成形车削。这种切削法比较理想,也适用于批量生产。 1.切削原理 切向成形车刀车削时,切削刃沿工件加工的表面切向切入。切削刃带有主偏角Kr,因此不是整个切削刃同时全部参与切削,而是由工件前端开始逐渐切入和切出,在瞬间只有一部分切削刃在工作,切削力较小,而且切削刃工作部分的工件前端始终为坯料的最大直径,工件刚度在切削过程中始终处于最大值,有利车削,这是…     

超声椭圆振动车削的切削特性

为了深入研究超声椭圆振动切削特性及其应用前景,通过建立超声椭圆振动切削模型,根据运动学方程,分析和推导出了切削占空比、振纹高度、振动频率、振幅之间的关系,揭示了超声椭圆振动车削表面粗糙度、加工精度、加工效率之间的相互关系。通过切削力和表面粗糙度试验对推导出来的结果进行了验证,试验结果表明有效减小切削力是超声椭圆振动切削加工应用的主要优势。     

薄壁套筒的车削加工

薄壁工件刚性差,加工中由于切削力、夹紧力和切削热的作用,易产生变形,影响加工精度和表面粗糙度。通过对装夹方式、刀具材料、刀具几何角度和切削用量四个方面进行研究,旨在探讨薄壁工件的变形程度,并寻求恰当的车削加工方法。实验结果显示,对尺寸较大的薄壁工件采用中心架和辅助支承;YT15硬质合全精车刀、较大的精车刀前角、90°主偏角和较高的精车切削速度,加工出的工件尺寸精度和表面质量都相当高,完全符合要求。     

星载复杂结构钛合金薄壁件超声振动切削研究

为了实现轻量化设计,航天器常采用复杂结构钛合金薄壁件作为承载、连接和定位元件,但是这类零件在切削过程中容易产生刀具磨损和变形,导致加工精度低,难以满足工作要求.基于钛合金薄壁件切削特性研究,采用超声振动金刚石车削方式控制切削力、装夹力引起的加工变形和残余应力,通过在线补偿修正刀具磨损误差;对壁厚(3～5)mm的典型星载钛合金薄壁件进行椭圆形超声振动切削,尺寸精度达到5μm,圆度误差为2.83μm,满足加工精度和稳定性要求.     

数控车床上加工薄壁管类零件可行性的判定

薄壁管类零件由于本身形状原因、刚度有别于实心工件，薄壁管类零件壁厚很薄，长径比很大，径向刚度很弱，在加工过程中受切削力、切削热及夹紧力等因素的影响，在切削力很大的情况下，产生径向变形和弯曲变形，是加工车削系统的薄弱环节，车削过程及其容易产生振动，使得被切削表面产生震纹，严重影响了工件表面质量。     

细长轴超声椭圆振动辅助车削试验

设计了铝合金细长轴超声椭圆振动辅助车削试验,测量了不同超声波电压下的刀具振幅。分析了铝合金细长轴超声振动辅助车削切削力变化规律,开展了普通车削与超声椭圆振动辅助车削单因素对比试验,对比了两种不同加工方法对切削力及细长轴不同区域表面粗糙度。试验结果表明:在相同切削参数条件下,超声椭圆振动辅助车削三个方向的切削力均小于普通车削切削力,并且随着振幅的增加切削力进一步降低。两种加工方式下细长轴的中间区域表面粗糙度均比两端差,但超声椭圆振动车削沿细长轴长度方向的表面粗糙度的均匀一致性优于普通车削。超声椭圆振动车削加工后的表面纹路较普通车削均匀缜密,且断屑效果优于普通车削,普通车削形成的切屑为连续切屑,切屑缠绕严重,而超声椭圆振动辅助车削的切屑形状为断续切屑,随着振幅的增大断屑效果提高。     

牙科氧化锆陶瓷的车削离散元仿真

通过力学性能试验对微观参数进行校准,建立了完全烧结牙科氧化锆陶瓷的离散元模型。基于该模型对完全烧结牙科氧化锆陶瓷常规车削加工过程进行了动态仿真,对氧化锆陶瓷车削加工后的微裂纹分布情况进行了模拟,分析了不同切削速度、切削深度对加工后表面裂纹情况及动态切削力的影响。仿真结果表明:加工后表面残留裂纹的数目及其最大深度、动态切削力均随切削深度的增大而明显增大;切削速度对表面残留裂纹的数目、动态切削力影响不明显,对表面残留裂纹最大深度影响没有明显规律。     

Thermomechanical modeling of oblique turning in relation to tool-nose radius

This article aims at predicting machining performances for oblique turning in relation to tool-nose radius. A new geometric analysis for the uncut chip area is proposed as function of depth of cut, feed rate, tool-nose radius, and edge direction angle. Cutting edge is discretized into increments and average uncut chip thickness, elementary direction angle and elementary depth of cut are determined for each one. A new thermomechanical model is developed for each increment which is supposed to be an oblique machining with single cutting edge. The predicted cutting force components are in good agreement with experimental data over a wide range of cutting conditions. In particular, the effect of tool-nose radius and cutting parameters on chip geometry, cutting temperature, and cutting force components are studied. It is underlined that tool-nose radius promotes the increase in radial force, however, its influence on the other parameters is negligible.     

超声振动和切削液联合作用下的刀刃非物理锐化

超声辅助切削和切削液的联合使用能减小切削力和降低表面粗糙度,试图说明其机理,目的是为开发精密和超精加工技术打下基础。超声辅助切削和切削液的联合使用,从性质上改变了刀刃施加给工件表面的作用力,包括摩擦力和压力：在无切削液情况下,刀刃切入时,前刀面和后刀面施加给被切削面的摩擦力方向是指向刀刃;在有切削液情况下,刀刃切入时,前刀面和后刀面施加给被切削面的摩擦力方向是背向刀刃。背向刀刃的摩擦力,相对于指向刀刃的摩擦力而言,会导致剪切角增大,等效于更锋利的刀刃所产生的剪切角;切削液的存在使得刀刃施加给工件的力更加集中,等效于圆角半径更小的刀刃所能达到的效果;切削液在刀尖部位的压力分布不利于工件表面产生微裂纹。也就是说,超声辅助切削和切削液的联合使用起到了更锋利即更小圆角半径刀刃所起的效果,称之为非物理锐化。     

Modelling of dimensional and geometric error prediction in turning of thin-walled components

In die-mold manufacturing and aircraft industry, many components that have thin-walled features are produced by turning operation. The major problem encountered during internal or external turning is cutting force induced deflection of workpiece along the periphery as well as axial length of a component. The present research work aims to develop a mathematical model for estimating dimensional and geometric errors during turning of thin-walled hollow cylinder qualitatively and quantitatively. In the proposed model, a mechanistic approach which is semi-analytical in nature is followed to achieve accuracy of the predicting results. First of all, process geometry model for thin-wall turning is developed based on process geometry variables such as uncut chip thickness, actual feed per revolution, actual depth of cut, peripheral cutting speed, effective cutting area etc. Using these process geometry variables and mechanistic cutting constants, a force model of turning is developed to estimate the tangential and radial force components. Later on, based on the predicted forces, tool-workpiece combined deflection model is developed to estimate radial, diametric and various geometric errors of the turned surface. The developed models are able to predict radial, diametric and various geometric errors such as straightness, circularly and cylindricity errors without conducting expensive actual machining operation. Hence, the present study will be helpful to take care of precautionary measures for controlling of dimensional and geometric errors more efficiently and reliably. Therefore, an attempt has been made to provide a basic platform to machining practitioners and process planners for in-depth comprehension and characterization of dimensional and geometric errors of the entire turned surface for varying machining conditions.     

A new process damping model for chatter vibration

This paper presents a new analytical process damping model (PDM) and calculation of Process Damping Ratios (PDR) for chatter vibration for low cutting speeds in turning operations. In this study a two degree of freedom complex dynamic model of turning with orthogonal cutting system is considered. The complex dynamic system consists of dynamic cutting system force model which is based on the shear angle (φ) oscillations and the penetration forces which are caused by the tool flank contact with the wavy surface. Depending on PDR, the dynamic equations of the cutting system are described by a new mathematical model. Variation and quantity of PDR are predicted by reverse running analytical calculation procedure of traditional Stability Lobe Diagrams (SLD). Developed mathematical model is performed theoretically for turning operations in this study and simulation results are verified experimentally by cutting tests.     

Effect of tool edge wear on the cutting forces and vibrations in high-speed finish machining of Inconel 718: an experimental study and wavelet transform analysis

High-speed machining has been receiving growing attention and wide applications in modern manufacture. Extensive research has been conducted in the past on tool flank wear and crater wear in high-speed machining (such as milling, turning, and drilling). However, little study was performed on the tool edge wear??the wear of a tool cutting edge before it is fully worn away??that can result in early tool failure and deteriorated machined surface quality. The present study aims to fill this important research gap by investigating the effect of tool edge wear on the cutting forces and vibrations in 3D high-speed finish turning of nickel-based superalloy Inconel 718. A carefully designed set of turning experiments were performed with tool inserts that have different tool edge radii ranging from 2 to 62???m. The experimental results reveal that the tool edge profile dynamically changes across each point on the tool cutting edge in 3D high-speed turning. Tool edge wear increases as the tool edge radius increases. As tool edge wear dynamically develops during the cutting process, all the three components of the cutting forces (i.e., the cutting force, the feed force, and the passive force) increase. The cutting vibrations that accompany with dynamic tool edge wear were analyzed using both the traditional fast Fourier transform (FFT) technique and the modern discrete wavelet transform technique. The results show that, compared to the FFT, the discrete wavelet transform is more effective and advantageous in revealing the variation of the cutting vibrations across a wide range of frequency bands. The discrete wavelet transform also reveals that the vibration amplitude increases as the tool edge wear increases. The average energy of wavelet coefficients calculated from the cutting vibration signals can be employed to evaluate tool edge wear in turning with tool inserts that have different tool edge radii.     

Surface layer microhardness changes with high-speed turning of hardened steels

In high-speed cutting of hardened steels, the surface layer is strongly affected by thermal effects and mechanical forces. Due to this, the surface layer of the machined material changes noticeably. Microhardness, one parameter of the surface integrity, is the most important. This paper deals with an investigation of microhardness. Measuring results are presented, and reasons for the sometimes significant changes in microhardness are analysed. It is proved on which part of the cutting edge the material removal will not take place but the cutting edge deforms the material plastically and how this part of the cutting edge can be reduced. With the measurement of the cutting force, the hypothesis is proved that the values of the cutting force components related to each other are different compared to the traditional turning. The passive force is 1.88?C2.25 times higher than the main cutting force. Hence, the force taking place on the flank face of the cutting tool is very high and the friction power significantly influences the cutting temperature. The friction taking place on the flank face of the cutting tool generates 2.8?C3.9 times higher heat than the cutting force. Due to the changes that occur in the surface layer, the hardness of this layer is higher with 100?C150?HV in depth of 0.1?mm than the original hardness or the hardness prescribed in the technical drawings. This phenomenon can be observed not only in internal hard turning but also machining of external and conical surfaces. Microhardness is compared after hard turning and after grinding. According to the measurements, the ground surface has not become a harder surface layer but softer. As an average result of many measurements, it has been proven that the original hardness (700?HV) after case hardening will increase to 800?C850?HV after hard turning and will decrease to 500?C550?HV after grinding. Microhardness changes are analysed considering the typical chip removal characteristics of hard turning. In this article, the focus is on how changes in microhardness influence the functional behaviour of the components and may affect their lifetimes. In this article, it has been proven that independently from the surface of the machined gear (bore, conical or face surface) the changes in the surface layer regarding microhardness do not differ.     

PCD刀具超声振动车削SiC_p/Al复合材料时的切削力特性研究

用PCD刀具对SiCp/Al复合材料进行了超声振动车削与普通车削的对比试验 ,探讨了切削速度、进给量和切深三种切削参数在两种切削状态下对切削力的影响规律 ,得出了超声振动车削SiCp/Al复合材料的主切削力经验公式。     

Machinability aspects concerning micro-turning of PA66-GF30-reinforced polyamide

This paper aims to study the behavior of machining forces and machined surface finish when micro-turning PA66-GF30-reinforced polyamide with various tool materials under distinct cutting conditions. The performance of polycrystalline diamond (PCD), CVD diamond coated carbide and plain cemented carbide tools (K15-KF and K15) were investigated in addition to the influence of feed rate on cutting forces, surface roughness and chip formation. The results indicated that the radial force was the highest force component because of the reduction in the effective cutting edge angle. Moreover, the cutting force increased almost linearly with feed, whereas the feed and radial forces remained unaltered. The cutting tools possessing lower edge radius promoted lower surface finish and turning forces, i.e., the best results were provided by the PCD tool, followed by the uncoated carbide inserts and finally by the CVD diamond-coated carbide tool.     

刀具磨损过程中的切削力特征研究

在相同的工件材料、刀具材料、切削参数和不同的刀具磨损状态下,从时域角度分析了刀具磨损状态对三向稳态切削力的影响,从频域角度利用FFT分析、功率谱分析等工具研究刀具磨损状态对动态切削力的影响情况,并对影响的机理进行讨论。分析结果表明刀具磨损状态迫使受动态力的刀具弯曲振动频率幅值和局部频率能量增大。