CVD金刚石厚膜刀具切削参数对切削力及粗糙度影响的研究

为了探究CVD金刚石厚膜刀具切削参数(包括刀具后角、刀尖圆弧半径、切削速度、进给量和切削深度)对切削力和被加工表面粗糙度影响的初步规律,采用单因素方法进行了一系列CVD金刚石厚膜刀具车削仿真和试验研究。结果表明:AdvantEdge有限元仿真软件模拟切削力过程有一定的准确性;在试验参数范围内,随着刀具后角的增大,切削力和表面粗糙度都是先减小后增大,当后角为11°时,切削力和表面粗糙度值最小;随着刀尖圆弧半径的增大,切削力逐渐增大,而表面粗糙度则逐渐减小;随着切削速度的增大,切削力和表面粗糙度都是先增大后减小,当切削速度为90m/min时,切削力和表面粗糙度值最大;随着进给量的增大,切削力和表面粗糙度都显著增大;随着切削深度的增大,切削力和表面粗糙度都逐渐增大,但切削深度对表面粗糙度的影响较小。     

颗粒增强钛基复合材料车削试验研究

为研究切削参数对颗粒增强钛基复合材料已加工表面粗糙度的影响规律,通过对切削力和切削温度开展试验研究,探究钛基复合材料的切削加工性。结果表明:在车削钛基复合材料时,随切削速度提高,切削力先增大后减小;切削温度随切削速度的升高而升高,且在较高速度范围内温度升高放缓;切削力随着颗粒含量的升高明显增大,但切削温度有所降低;切削参数在v=80～100 m/min,a_p=0.30～0.60 mm,f=0.06～0.10 mm/r范围内,已加工表面粗糙度R_a可在0.5 μm以下。      

高速车削3Cr13不锈钢切削力的仿真分析

切削力是表征加工过程的主要参数,也是反映加工状态的重要物理量之一,切削力的大小直接影响着加工状态和加工表面质量。基于有限元分析软件Advant Edge FEM,设计了以进给量、背吃刀量、车削速度、车刀前角、车刀后角等切削参数为自变量的五因素四水平正交试验,对3Cr13不锈钢的高速车削过程进行二维有限元仿真,探讨了各自变量对切削力的影响规律。以径向切削力最小为目标,运用极差分析法获得了各切削参数的最优组合。结果表明:背吃刀量对径向切削力的影响最大、车刀后角的影响最小;在给定的切削条件下,径向切削力最小时的最优组合为进给量0.19 mm/r、背吃刀量0.3 mm、车削速度500 mm/min、车刀前角19°、车刀后角7°。     

超精密车削加工有限元仿真研究

为研究不同的切削加工参数对超精密车削加工的切削力、切削温度、切削应力等的影响,用有限元法对金刚石车削过程进行三维仿真,得到在不同切削参数下车削铝合金时的切削力、切削温度、切削应力的变化,以及切削区的微观应力的分布状态。仿真结果表明:刀具所受到的主切削力明显大于其余两个方向的力;当切屑和母体发生分离的时候,切削力会突然降低;工件上应力最大的部分是和前刀面相对的部分;切削温度较低,最高为30℃。根据仿真结果可对切削参数进行优化。     

PCBN刀具高速铣削TC4钛合金切削性能与工艺参数优化研究

针对钛合金TC4(Ti-6Al-4V)的加工特性,采用PCBN刀具,基于单因素试验,研究高速铣削条件下工艺参数对切削力、切削振动等的影响规律,提出综合考虑切削力、切削振动、表面粗糙度的工艺参数优选方法。研究表明:切削力和切削振动随切削速度v和每齿进给量f_z的增大呈现一定的波动,随径向切深a_e和轴向切深a_p的增大而增大,切削振动受切削力影响较为显著。考虑切削性能,以材料切除率为优化目标,以切削力、切削振动和表面粗糙度等为约束条件,建立工艺参数优选模型,可得到不同约束条件下工艺参数的优选组合。     

涂层硬质合金刀片高速车削蠕墨铸铁的实验研究

针对蠕墨铸铁Ru380的高速车削,本文先采用单因素实验,研究切削三要素v、f、a_p对主切削力F_z的影响,随后采用正交实验分析了v、f、a_p对主切削力F_z影响的显著程度,进一步以正交实验所得数据,采用最小二乘法,给出了实验条件下主切削力预报模型F_z=5 655.877 6×a_p~(0.964)×f~(0.558)×v~(-0.268),并利用单因素实验数据进行验证。结果表明:v与F_z呈负相关;f和a_p与F_z呈正相关,其中a_p对F_z影响最大,其次为f,最小为v,F_z预报值与实测值相差在15%以内。最后,采用超景深显微镜、激光扫描显微镜、扫描电子显微镜(SEM)、能谱仪(EDS)等多种方法观察刀片磨损形式、分析刀片失效机理。结果表明:涂层硬质合金高速车削蠕墨铸铁时以粘结磨损为主、伴随着硬质点磨损和氧化磨损。在切削热的作用下,涂层内部热裂纹明显。     

基于ABAQUS高速切削Ti-6Al-4V切削状态的有限元仿真

文章基于Abaqus/Explicit的Johnson-Cook材料模型以及断裂准则模拟高速正交切削Ti-6Al-4V,仿真分析了切削速度、切削深度、刀具前角变化时对平均切削力以及锯齿状切屑形态的影响.研究结果表明:切屑锯齿化程度和齿距随切削速度和切削深度的增加而增大,随前角的增加而减小.平均切削力在切削速度为60m/min-180m/min时趋于平稳,随切削深度增加而增大,随前角增大而减小.     

切削用量对切削力和切削振动的影响

为探究车削时切削用量对切削力和切削振动的影响,设定半精加工的切削用量范围,采用正交试验设计方法制定试验流程,在数控机床上使用硬质合金外圆车刀对45#圆钢进行切削试验,切削过程不加冷却液,并分别使用Kistler切削力测量系统和Vib Pilot M+P切削振动测量系统同时采集3个方向的切削力信号和切削振动信号,对试验数据使用方差分析(ANOVA)、贡献率计算和相关分析的方法进行处理。结果表明:背吃刀量对主切削力和进给力的影响最大,进给量对背向力和3个方向切削振动的影响最大,而切削速度对各方向切削力和切削振动的影响都最小;切削力信号的误差要远小于切削振动信号的误差。试验分析结果可以为合理设计切削用量参数,有效选择切削状态监控信号提供参考。     

SPH方法的单晶硅激光辅助切削仿真与试验

单晶硅加工过程中很容易产生细微裂纹,从而影响表面加工质量。激光辅助加工(laser-assisted machining, LAM)可以软化代加工区域,有效减小切削力,延长刀具寿命,提高表面加工质量。建立热力耦合的SPH模型,来模拟单晶硅激光辅助车削过程,在不同温度条件下,探究裂纹扩展损伤和切削应力以及转速和切深对表面粗糙度的影响,并通过LAM试验,验证仿真结果的准确性。结果表明：提高温度有利于单晶硅的塑性切削,随着切削域温度的增加刀具应力逐渐减小,300℃时的刀具应力较常温下降低了约50%,表面加工质量有明显提升;且600℃时的切屑为塑性流动锯齿线条,其塑性大幅度提高。切削时应选择较小的切削深度,低于4500 r/min的转速,单晶硅表面粗糙度S_a可在1.000 nm以下。     

碘化铯晶体的力学性能和超精密车削研究

目的 研究碘化铯(CsI)晶体(110)晶面的力学性能和以及车削参数对超精密车削表面粗糙度的影响。 方法 分别采用纳米压痕和霍普金森压杆(SHPB)试验,获得并分析CsI晶体(110)晶面在准静态下和高应变率下的力学性能。采用单点金刚石车削(SPDT)的方法在不同的方向和车削参数对晶体进行超精密加工,并使用白光干涉仪、测力仪和红外热像仪分别测量超精密车削过程中已加工表面的粗糙度Ra、切削力和切削温度。结果 CsI晶体在压痕过程中主要发生塑性变形,且无明显的脆性裂纹,其(110)晶面的维氏硬度约为100 MPa。当应变率从6 000 s^–1提高8 000 s^–1时,晶体的屈服强度提高了7 MPa。在试验中,沿着270°方向车削,可以获得Ra为20 nm以下的表面粗糙度。沿着该方向使用10°前角的金刚石车刀、转速为 2 000 r/min、进给速度为4 μm/r、切削深度为2 μm时,可以获得最好的表面质量,平均表面粗糙度Ra为8.53 nm,最大表面粗糙度Ra为11.02 nm。结论 CsI晶体具有较强的塑性,且硬度低,高应变率下,材料的强度和硬度明显提高。通过提高转速即切削速度,增大超精密车削过程中的材料应变率,改善了软塑性材料的可加工性,使CsI晶体的表面粗糙度降低了80%。结合优选的车削方向、刀具前角、进给速度和切削深度等其他车削参数,获得了Ra在10 nm以下的光滑表面。     

Investigation of the effect of rake angle and approaching angle on main cutting force and tool tip temperature

This paper deals with the comparison of measured and calculated results of cutting force components and temperature variation generated on the tool tip in turning for different cutting parameters and different tools having various tool geometries while machining AISI 1040 steel hardened at HRc 40. The geometric variables (approaching angle and rake angle) of the tool were changed using selected cutting parameters; thus, the cutting force components and temperature variations on tool face (in secondary shear zone) were determined. The selected cutting variables and the tools in different geometries were tested practically under workshop conditions. In this way, the essential information about the validity of selected values was obtained. During the tests, the depth of cut and cutting speed were kept constant and each test was conducted with a sharp uncoated tool insert. For making a comparison, the main cutting force/tangential force component for different cutting parameters and tool geometries were calculated by Kienzle approach and the temperature values were calculated based on orthogonal cutting mechanism. Finally, the effects of cutting parameters and tool geometry on cutting forces and tool tip temperature were analysed. The average deviation between measured and calculated force results were found as 0.37%. The cutting force signals and temperature values provided extensive data to analyse the orthogonal cutting process.     

Radial immersion angle estimation using cutting force and predetermined cutting force ratio in face milling

Radial immersion ratio is an important factor to determine the threshold for tool conditioning monitoring and automatic force regulation in face milling. In this paper, a method of on-line estimation of the radial immersion angle using cutting force is presented. When a tooth finishes sweeping, a sudden drop of cutting force occurs. This force drop is equal to the cutting force that acts on a single tooth at the swept angle of cut and can be obtained from the cutting force signal in feed and cross-feed directions. The ratio of cutting forces in feed and cross-feed directions acting on the single tooth at the immersion angle is a function of the immersion angle and the ratio of radial-to-tangential cutting force. In this study, it is found that the ratio of radial-to-tangential cutting force is not affected by cutting conditions and axial rake angle. Therefore, the ratio of radial-to-tangential cutting force determined by just one preliminary experiment can be used regardless of the cutting conditions for a given tool and workpiece material. Using the measured cutting force during machining and a predetermined ratio, the radial immersion ratio is estimated in the process. Various experiments show that the radial immersion ratio and instantaneous ratio of the radial to tangential direction cutting force can be estimated very well by the proposed method.     

Finite element modelling of shear angle and cutting force variation induced by material anisotropy in ultra-precision diamond turning

This paper addresses a key theoretical problem in the mechanics of ultra-precision machining – shear angle prediction and cutting force variation induced by crystallographic anisotropy. The constitutive equation of crystal plasticity is implemented in the finite element modelling of the chip formation at micro-scale to take into account the effect of crystallographic orientations of the work piece to be cut. The theoretical prediction of shear angle and cutting force variation reveals two distinguished phases of pre-compression and steady-state cutting in ultra-precision diamond turning. The predicted patterns of cutting force variation are in good agreement with published experimental results.     

Investigation of the effect of rake angle on main cutting force

This paper presents a study of comparison of empirical and experimental results for main cutting force during machining rotational parts by unworn cutting tools. A dynamometer was designed and produced for measuring the forces. Two strain gauges were placed at the correct position on the machine tool and cutting tool at the design stage. Correct gauge positioning sensed displacements of the tool caused by cutting forces. AISI 1040 was used as the workpiece material. Main cutting force (F_c) was measured for eight different rake angles changing from negative to positive values at five different cutting speeds. The depth of cut and feed rate were kept throughout the experiments. Empirical results according to Kienzle approach were compared with experimental results. Main cutting force was observed to have a decreasing trend as the rake angle increased from negative to positive values. The deviation between empirical approach and experiments was in the order of 10–15%.     

Cutting force model of orbital single-point micromachining tool

This paper presents an analytical, ductile cutting force model of a novel micromachining tool that is based on micro-orbital motion of a single-point tool tip. The single-point tool tip used in this study is a single crystal diamond stylus that consists of a cone section of 50° and a spherical tip with radius less than 1 μm. The tool is actuated by a piezo tube that generates a high frequency micro-orbital motion of a single-point tool tip in a circular trajectory. Unlike conventional micromilling, where the cutting occurs at the edges of the tool flutes, a single-point tool may utilize any point on the circumference surface of the tool tip. Also, due to its extreme negative rake angle at small depths of cut, the technique can machine brittle materials such as silicon in the ductile regime. Experiments were performed on an aluminum alloy (AL2024) to obtain the specific cutting force and the coefficient of friction in order to calculate the cutting forces in all 3 axes and to verify the model.     

刀具磨损对单晶铝纳米切削过程的影响

基于分子动力学的理论建立了单晶铝的纳米切削仿真模型,比较研究了在刀具未磨损和刀具磨损条件下对切削过程的影响。研究表明：相比于刀具未磨损,在刀具磨损的情况下,已加工表面质量有所下降,基体上出现了大量的位错等缺陷;切削力也全部有所升高,其中刃口半径磨损对切削力影响最为显著,在相同的切削条件,相比于刀具未磨损升高约为17.78%,后刀面磨损和前刀面磨损对切削力的影响基本相同,提高了约7.98%;刀具温度和工件的温度也都有不同程度的升高,其中,工件的温升更高。刀具刃口半径磨损对温升影响最大,达到稳定切削时,刀具的平均温度相比于刀具未磨损升高约为7.2%。     

Prediction of cutting force distribution and its influence on dimensional accuracy in peripheral milling

Cutting force has a significant influence on the dimensional accuracy due to tool and workpiece deflection in peripheral milling. In this paper, the authors present an improved theoretical dynamic cutting force model for peripheral milling, which includes the size effect of undeformed chip thickness, the influence of the effective rake angle and the chip flow angle. The cutting force coefficients in the model were calibrated with the cutting forces measured by Yucesan [18] in tests on a titanium alloy, and the model was proved to be more accurate than the previous models. Based on the model, a few case studies are presented to investigate the cutting force distribution in cutting tests of the titanium alloy. The simulation results indicate that the cutting force distribution in the cut-in process has a significant influence on the dimensional accuracy of the finished part. Suggestions about how to select the cutter and the cutting parameters were given to get an ideal cutting force distribution, so as to reduce the machining error, meanwhile keeping a high productivity.     

PCD刀具加工氮化硅陶瓷孔的试验研究

使用PCD刀具对氮化硅陶瓷内孔进行切削试验,首先研究氮化硅陶瓷材料的去除机理,主要包括脆性去除和塑性去除,且以脆性去除为主。其次,研究刀具前角、切削速度、背吃刀量和进给量对切削力的影响。结果表明:刀具前角对切削力的影响不明显;随切削速度、背吃刀量和进给量的增加,切削力均增大,且背向力大于进给力和主切削力。最后,重点研究各参数对内孔侧壁表面粗糙度的影响。结果表明:进给量对表面粗糙度的影响最显著,其次是背吃刀量和切削速度,刀具前角几乎没有影响,且当刀具前角为-5°,切削速度为32.97m/min,背吃刀量为0.10mm,进给量为0.08mm/r时,可以得到较好的表面粗糙度和刀具寿命的综合效益。      

光学微结构超精密多轴铣削加工技术

采用单点金刚石飞刀加工可以直接加工出具有纳米级的表面粗糙度和亚微米级形状精度的光学微结构元件而不需要后续处理。通过超精密飞刀加工微V沟槽的实验,分析了主轴转速、进给速度、切削深度和切削行间距对微V沟槽加工精度的影响,并对切削参数进行优化。最后,利用优化后的切削参数加工出微V沟槽结构。实验结果显示,超精密飞刀加工微V沟槽可达到满足光学微结构加工精度的要求。     

Statistical analysis of surface roughness and cutting forces using response surface methodology in hard turning of AISI 52100 bearing steel with CBN tool

The present work concerns an experimental study of hard turning with CBN tool of AISI 52100 bearing steel, hardened at 64 HRC. The main objectives are firstly focused on delimiting the hard turning domain and investigating tool wear and forces behaviour evolution versus variations of workpiece hardness and cutting speed. Secondly, the relationship between cutting parameters (cutting speed, feed rate and depth of cut) and machining output variables (surface roughness, cutting forces) through the response surface methodology (RSM) are analysed and modeled. The combined effects of the cutting parameters on machining output variables are investigated while employing the analysis of variance (ANOVA). The quadratic model of RSM associated with response optimization technique and composite desirability was used to find optimum values of machining parameters with respect to objectives (surface roughness and cutting force values). Results show how much surface roughness is mainly influenced by feed rate and cutting speed. Also, it is underlined that the thrust force is the highest of cutting force components, and it is highly sensitive to workpiece hardness, negative rake angle and tool wear evolution. Finally, the depth of cut exhibits maximum influence on cutting forces as compared to the feed rate and cutting speed.