薄壁Ti6Al4V管件采用不同车削参数加工引起的表面残余应力的测量（英文）

同时考虑测量精度、测量可行性以及节约材料诸多方面的问题,运用有限元验证的方法确定零件合适的长度。同时运用精度较高的基于有限元分析的修正方法结合X射线法测量Ti6Al4V管件车削加工引起的表面残余应力,分析不同切削参数以及退火处理对表面残余应力的影响。结果显示:切削速度、进给量以及切削深度在指定范围内增大时会导致表面切削和进给方向的压应力增大,退火处理会使得表面2个方向的残余应力减小将近85%。     

Ti6Al4V零件铣削加工表面等效残余应力与作用深度的测量及其有限元分析

金属零件在切削加工后,其被加工表面会形成一残余应力层,其所引起零件的变形是影响精密弱刚性零件精度的重要的因素。为了预测Ti6Al4V零件因铣削加工表面残余应力而引起的变形,本文介绍一种测量表面等效残余应力及其作用深度的方法而达到此目的。通过对被加工面的对面进行两次腐蚀去除材料的操作使得零件的厚度和中性层的位置发生变化,测量此过程中零件挠度和表面应变的变化,进而计算得铣削加工引起的零件表面等效残余应力及其作用深度值。通过有限元分析验证该方法得到的结果,发现有限元计算得到的零件挠度和应变的变化与实际测量值非常吻合,因此可以断定该方法得到的结果是正确的,其可以正确评估铣削加工引起的表面残余应力性质和大小并能准确预测零件铣削加工后因表面残余应力而引起的工件的变形量,从而可以预测零件是否满足精度要求。     

钛合金铣削加工表面残余应力有限元仿真

为了分析铣削工艺参数对钛合金已加工表面残余应力的影响,根据金属切削有限元分析的相关理论,以钛合金Ti6Al4V为工件材料,建立了铣削加工的有限元模型。采用正交试验设计法对钛合金Ti6Al4V铣削仿真的工艺参数进行优化,并用极差法分析不同的铣削速度、铣削深度、铣削路径对钛合金Ti6Al4V工已加工表面残余应力的影响。研究表明:在钛合金Ti6Al4V铣削过程中,对工件已加工表面残余应力影响因素由小到大依次为:铣削深度<铣削路径<铣削速度,切削深度对已加工表面残余应力影响较小,铣削速度对已加工表面残余应力影响最大;在研究范围内,随着铣削速度的增大,已加工表面残余应力逐渐增加。     

Ti6Al4V零件铣削加工表面等效残余应力与作用深度的测量

为了预测Ti6Al4V零件因铣削加工所致表面残余应力而引起的变形,介绍了一种测量表面等效残余应力及其作用深度的方法。通过对被加工面的背面进行两次腐蚀剥层的操作,使得零件的厚度和中性层的位置发生变化,测量此过程中零件挠度和表面应变的变化,进而计算得到铣削加工引起的零件表面等效残余应力及其作用深度值。通过有限元分析验证,发现有限元计算得到的零件挠度和应变的变化与实际测量值非常吻合,因此可以断定该方法得到的结果是正确的。其可以正确评估铣削加工引起的表面残余应力性质和大小并能准确预测零件铣削加工后因表面残余应力而引起的工件的变形量,从而可以预测零件是否满足精度要求。     

基于化铣剥层和挠度变化的钛合金铣削加工表面内应力的测量

对Ti6Al4V材料零件利用侧铣进行加工,其被加工表面会产生一内应力(即残余应力)层。为了测量加工引起的随深度变化的残余应力,通过对零件的应力层进行腐蚀剥层,并测量此过程中零件挠度的变化。根据弯矩与挠度的关系以及应力与弯矩的关系,最终计算得到铣削加工引起的随深度变化的残余应力。将计算得到的应力值带入有限元模型中进行计算,将计算得到的挠度的变化与实验测得的挠度的变化进行对比,发现两条曲线的重合度很高,由此说明此测量方法精度很高,可以运用与实践中加工残余应力的测量。     

钛合金切削表面残余应力影响因素及参数优化

钛合金切削过程具有温度高、摩擦力大、刀具严重磨损等缺点。为了减少钛合金表面出现微小裂纹,基于国内外研究现状,以Ti6Al4V切削表面残余应力为研究对象,建立了钛合金切削有限元模型。讨论了切削速度、切削深度、每齿进给量、不同切削用量对切削表面残余应力的影响。建立了切削表面残余应力回归模型,并采用混合遗传退火算法对切削参数进行优化,得到了最优切削参数组合。研究表明:切削速度增加,钛合金表面残余应力增加;切削深度对残余应力的影响较小;残余应力随着每齿进给量增加而减小。     

基于Deform-3D的车削残余应力分析

切削加工残余应力是零件疲劳强度的重要影响因素,因此对残余应力的研究具有很大的实际指导作用。文章根据热—弹塑性有限元理论,在DEFORM-3D中建立铝合金7075的三维有限元模型,对车削加工表面残余应力进行分析,得到不同切削用量和前角对表面残余应力的影响规律。结果表明:在切削用量和前角一定变化范围内,工件表面在切削方向主要产生残余压应力;在进给方向主要产生残余拉应力,随着距表面层深度的增加,残余拉应力逐渐变为残余压应力。     

预应力硬态切削加工表面残余应力的数值模拟与试验研究

为研究预应力硬态切削过程中预应力条件对已加工表面残余应力的影响规律,建立热力耦合、平面应变的预应力正交切削有限元模型,并结合有限元软件MARC的网格重划分功能,对PCBN刀具预应力车削轴承套圈材料GCr15(HRC62)的加工表面残余应力进行了数值模拟,同时进行了试验研究.结果表明,预应力切削方法能主动控制加工表面残余压应力的状态,从而提高轴承零件的疲劳寿命;而且随着施加的预应力的增大,表面残余压应力的大小和分布层深都显著增加.     

钛合金拉伸铣削的机理与试验研究

对钛合金TC4(Ti6Al4V)在拉伸状态下进行铣削加工.建立平面应变的残余应力形成模型,分析了拉伸装夹改变加工表层残余应力的机理.研究了铣削对钛合金表面残余应力和表面粗糙度的影响,得到了在不同切削参数下钛合金表面残余应力和表面粗糙度的实验数据.实验结果表明,拉伸装夹基本不影响表面粗糙度,但可以大大提高加工表面残余压应力并增大残余压应力层的厚度.     

钛材的表面加工

金属切削加工和磨削加工可产生金属表面的损伤,其损伤可引起金属表面特性和金属表层特性的变化.金属表面特性是指表面粗糙度、波纹、形状(公差)、显微缺陷(裂纹、凹坑等);表层特性包括表面残余应力、热影响层的显微组织变化、硬度及塑性变化等.有资料表明,选用不同的切削加工工具及不同的切削工艺进行钛材的切削加工,可使钛材的表面粗糙度、表面残余应力和疲劳强度有所不同.在Ti—6Al—4V钛     

Residual stresses in surface layer after dry and MQL turning of AISI 316L steel

Residual stresses in the surface layer exert a significant impact on functional aspects of machined parts. Their type and value depend on the workpiece and tool material properties, cutting parameters and cooling and lubrication conditions in the tool-chip-machined surface interface. As the effects of material properties and cutting parameters have been widely studied, the influence of cooling and lubrication conditions, especially minimum quantity lubrication (MQL) on the surface layer residual stresses and the relationships between them have not been investigated. In this paper the effects of dry, MQL cutting and cutting with emulsion conditions together with cutting parameters on residual stresses after turning AISI 316L steel were investigated. X-ray diffraction method was used for measuring superficial residual stresses in the cutting (hoop) and feed (axial) directions. Tensile residual stresses were detected in both directions and the values in the cutting direction turned out to be higher than in the feed direction. The effects of cooling and lubrication conditions largely depend on the selected cutting parameters, whose influence is linked to the cutting zone cooling and lubrication mode. Elaborated regression functions allow calculation and optimization of residual stresses in turning AISI 316L steel, depending on cooling and lubrication conditions as well as cutting parameters.     

纵向旋转切削加工对环形零件畸变的影响

通过旋转试验和有限元分析介绍了工件在切削加工过程中产生的畸变情况，分析了工件的装夹方式、切削速度、切削深度和进刀量对100Cr6钢环圆度的影响。通过去应力退火释放冷加工诱发的残余应力后工件的圆度与切削参数有关。另外测试了被试验环的表面残余应力，其表面残余应力与装夹方式有关。将测量的装夹力作为计算参数输入，通过有限元分析方法测试了装夹方式对工件变形的影响。协同测量结果示出了装夹方式影响工件变形的一个主要因素，表面残余应力与工件的径向变形有关，最大的拉伸应力位于夹口位置。旋转切削试验结果表明，提高切削速度圆度会稍有增加；随着切削深度的加大，圆度呈下降趋势，尽管切削力增加了；进给量的增加会导致更高的切削力，因此圆度值也增加；常规的去应力退火可使被加工环的圆度值增加。     

新型微坑车刀切削AISI4140残余应力影响因素分析研究

为了探究切削用量对新型微坑车刀切削工件表面残余应力的影响规律,应用AdvantEdge切削仿真软件,结合单因素和正交实验,通过微坑车刀和原车刀切削AISI_4140仿真及实验验证。结果表明,原车刀和微坑车刀残余拉应力随切削速度增大,先增大后减小,随进给量的增大而减小,总体上,微坑车刀切削工件残余拉应力更小。残余压应力随切削速度增大,微坑车刀切削工件先增大后减小,随进给量增大先增大后减小。原车刀几乎不变。切削用量对微坑车刀切削工件残余应力影响,进给量最大,切削速度次之,切削深度最小。通过实验验证,相同切削条件下,微坑车刀降低了加工工件表面残余拉应力,提高了加工工件表面质量,一定程度提高了工件的服役寿命。     

Effects of Edge Preparation and Feed when Hard Turning a Hot Work Die Steel with Polycrystalline Cubic Boron Nitride Tools

Polycrystalline cubic boron nitride (PcBN) is usually employed in hard turning. Selection of optimum edge preparation is machining parameter dependent. This paper investigates the effects of edge preparation and feed on tool life and workpiece residual stresses. An Arbitrary Lagrangian and Eulerian (ALE) finite element model was used to explain tool wear rate and residual stress profile. Experimental results showed that honed edges could be employed for hard turning when tensile principal stresses in the tool were maintained at a low magnitude. Chamfered edges produced less compressive residual stresses on the surface. However, away from the machined surface, compressive residual stresses penetrate deeper into the workpiece.     

On the Effects of Residual Stresses Induced by Coated and Uncoated Cutting Tools with Finite Edge Radii in Turning Operations

This paper presents an analysis of residual stresses in turning of AISI 316L and AISI 1045 steels with coated and uncoated tools having finite edge radii. An analytical predictive model, and experimental techniques involving X-ray diffraction and IR thermal imaging were used. Machining with coated tools produce higher superficial residual stresses, larger tensile layer thickness and higher residual stresses below the machined surface when using large cutting edge radii at low feed rates. This effect is correlated with the increase in the amount of heat conducted into the workpiece, and the associated generation of high tensile residual stresses and severe work-hardening.     

Influence of machining by finishing milling on surface characteristics

The aim of this study is to analyse the evolution of residual stresses, microstructure, microhardness and roughness in relation to the different parameters of milling. For finishing milling, parameters are cutting speed and feed. The hole drilling strain gage technique was used to determine the residual stresses. These are measured from the surface to the bottom of the treated workpiece. Two different materials were used in this study: a carbon steel (CS) and a duplex stainless steel (DSS). The latter belongs to a high strength stainless steel family with high corrosion resistance properties. In this study, we have used the experimental system method to analyse the evolution of different surface characteristics in connection with cutting phenomena which are cutting forces, chip geometry and cutting temperature. We have noted that a high value of cutting speed used with a small value of feed improves the quality of the machined surface.     

A comprehensive experimental study on surface integrity by end milling Ti–6Al–4V

End milling titanium Ti–6Al–4V has wide applications in aerospace, biomedical, and chemical industries. However, milling induced surface integrity has received little attention. In this study, a series of end milling experiments were conducted to comprehensively characterize surface integrity at various milling conditions. The experimental results have shown that the milled surface shows the anisotropic nature with the range of surface roughness values from 0.6 to 1.0 μm. Surface roughness value increases with feed and radial depth-of-cut (DoC), but has much less variation in the cutting speed range. Compressive residual normal stress occurs in both cutting and feed directions, while the influences of cutting speed and feed on residual stress trend are quite different. The microstructure analysis shows that β phase becomes much smaller and severely deformed in the near surface with the cutting speed, but phase transformation was absent for the milling conditions. The milled surface microhardness is about 70–90% higher than the bulk material in the subsurface.     

Comparison of the machinabilities of Ti6Al4V and TIMETAL® 54M using uncoated WC–Co tools

Single-point turning tests of cylindrical bars were undertaken to analyse and compare the machinability of Ti6Al4V, the most common titanium alloy, and TIMETAL^® 54M, a newly developed alloy with similar mechanical properties as Ti6Al4V but with better machinability. Conventional cooling and uncoated WC–Co tool inserts were used in the study, because they are the most recommended for machining these materials. The feed and the depth of cut were maintained constant, and only the cutting speed was varied because it is the most affecting parameter. Adhesion of workpiece material in the form of a built-up edge appeared in all the cutting inserts after machining both alloys, which was removed for flank- and crater-wear measurements. Lower wear rates were observed for the Ti54M alloy, especially at high cutting speeds. In the same manner, cutting-force measurements showed lower specific cutting- and feed-force values for the Ti54M alloy. Adiabatic shear bands, a typical feature in the machining of titanium alloys, were observed in chips from both alloys under all cutting conditions. Finally, scanning electron microscopy observations were carried out to analyse the adhered material on the cutting edges of the worn tools where signs of diffusion and attrition were detected.