三切削刃BTA深孔钻钻削过程研究

通过试验对3个切削刃BTA深孔钻削过程进行了研究,主要分析了在特定的深孔条件下切屑变形和钻削力的情况.通过对测试系统所得到的试验数据进行评估和证实,阐述了BTA深孔钻轴向力的组成和切屑变形、刀具磨损以及钻削力之间的关系.研究结果表明,钻头的内刃在切削过程中产生的切屑变形最大,3个切削刃(内刃、中间刃、外刃)的切削力和切屑变形的总体变化趋势是相同的.     

三切削刃BTA深孔钴钴削过程研究

通过试验对3个切削刃BTA深孔钻削过程进行了研究,主要分析了在特定的深孔奈件下切屑变形和钻削力的情况。通过对测试系统所得到的试验数据进行评估和证实,阐述了BTA深孔钻轴向力的组成和切屑变形、刀具磨损以及钻削力之间的关系。研究结果表明,钻头的内刃在切削过程中产生的切屑变形最大,3个切削刃（内刃、中间刃、外刃）的切削力和切屑变形的总体变化趋势是相同的。     

微切削加工的切屑变形及切削力

本文从分析微切削加工表面的形成机理入手,在考虑刀具钝圆半径存在的条件下,分析了切削表面的形成过程和微切削加工中切削变形系数,在理论上阐明了微切削加工中的切屑变形及切削力情况。在进一步实验的基础上,探明了微切削加工中,切削速度、进给量、切削深度、刀具材料及工件材料等影响切屑变形及切削力的因素。得出了微切削加工中的切屑变形系数要大于常规切削加工的切屑变形系数,减小刀具钝圆半径会减小刀具后刀面与工件的接触长度,并且会减小切削刃以下部分金属的变形,有利于获得高质量的加工表面的结论。     

镍基高温合金管板深孔加工试验

针对镍基高温合金材料切削变形大、加工硬化严重,材料强度高、切削力大,导热系数小、切削温度高等加工特点,开展BTA深孔加工工艺试验,从钻头直径、切削转速、进给速度三方面分析了对孔加工质量的影响,并试验分析了BTA钻头的使用寿命。     

微细切削中侧刃的切削影响研究

尺度效应是微切削工艺中的一种特殊现象,通常用最小未变形切屑厚度来判定尺度效应发生的临界点。为了更好地理解微细铣削的切削机理,对铣刀钝圆半径与尺度效应之间的关系进行深入研究是有必要的。由于在铣削加工过程中,刀具大多数为径向进给,侧刃为主要切削刃,因此这里对仅有侧刃参与切削的情况进行了仿真与试验研究。通过对仿真中切屑形貌与试验中表面粗糙度的分析,分别确定了仿真与试验的最小未变形切屑厚度值。仿真与试验结果表明,微细铣削的两种工艺方式对最小未变形切屑厚度的影响有限,最小未变形切屑厚度为（0.28～0.40）倍的铣刀钝圆半径。同时,工件的材料属性对刀具侧刃的最小未变形切屑厚度有一定的影响。本研究可以用于指导微细铣削加工中对于不同刀具钝圆半径及工件材料加工参数的选择和量化,提高工件加工质量具有重要参考价值。     

难加工材料枪钻加工技术研究

深孔加工是机械加工领域的重要分支,在钛合金、沉淀硬化不锈钢等难加工材料的深孔加工过程中,存在加工表面质量差、刀具崩刃、磨损严重和断屑排屑困难等问题。枪钻是深孔加工领域发展最早、应用范围最广的深孔加工刀具之一,其几何结构特殊,在深孔加工中具有加工质量好、效率高、直线度好等特点。本文介绍了枪钻的主要结构及受力情况,分析了枪钻的切削加工过程及其断屑条件,通过对切屑、切削力和切削温度的研究,得到了刀具、工艺参数以及切屑对加工质量和刀具磨损的影响规律。最后以两种典型的难加工材料为代表,分析了难加工材料深孔加工的特点。研究结果对难加工材料的枪钻深孔加工具有重要的指导意义。     

BTA深孔钻的合理使用

BTA深孔钻是内排屑深孔钻的典型结构,是在单刃内排屑深孔钻的基础上改进而成。切削刃呈双面错齿状,使切削力分布均匀,钻削平稳可靠,所钻削的深孔具有良好的直线性,切屑从双面切下,并从双面排屑孔中进入钻杆,将切屑排出孔外,较单刃内排屑深孔钻,切削力分布合理,更易于使切屑分开和折断。     

基于自导向机理的深孔轴线偏斜分析

基于自导向机理,研究了BTA深孔刀具导向条的受力状态。借助Hertz接触理论,弹塑性接触变形理论,建立了导向副的接触变形模型。分析不同载荷形式下导向副的接触状态,建立了研究深孔轴线偏斜的数学模型,最后通过切削加工试验进行验证,结果表明:孔轴线理论偏斜情况与实际切削相一致,单位偏斜量的理论值与实际测量值基本吻合。     

基于DEFORM-3D的深孔枪钻切屑成形机理分析

切屑形态对枪钻深孔加工中孔成型精度影响较大,利用DEFORM-3D有限元仿真软件模拟深孔加工中切屑的形成过程、形态和断屑方式,准确复现切屑的形成过程及形态,并计算切屑的曲率与厚度。模拟分析与记录轴向力、扭矩和切削过程温度等参数,揭示出力与扭矩的全过程变化规律,分析得出切削刃温度最高区域、相邻区域的温度分布规律,为切削过程工艺参数的控制提供理论依据。试验与仿真数据对比分析表明,采用有限元分析方法可为枪钻深孔切削过程工艺参数选取和优化提供基本可信的依据,并有效缩减切削试验次数。     

下排屑精扩孔钻

下排屑精扩孔钻,是在粗加工通孔后,留较少切削余量,用扩孔办法加工精孔的一种钻头。它改变了标准麻花钻的切削角度,在外刃和修光刃上磨出前角,形成了正的端面刃倾角,控制了切屑流出的方向。在钻头对通孔进行扩孔时,切屑离开刃口,也就是切屑被切削刃切去后,立即向已加工孔的下面排出,而不是靠切屑的重量压下去,使     

Thermal stress developed during the laser cutting process: consideration of different materials

The laser cutting of metallic substrates results in the development of thermal stresses around the cut edges. Depending on the cutting speed, laser power intensity, and material properties, stress levels reaching and exceeding the yielding limit of the substrate material can result. In the present study, the laser cutting situation is simulated and temperature as well as thermal stress fields are computed for steel, Inconel 625, and Ti-6Al-4V alloy. The cutting speed of the laser is considered to be constant and a constant temperature heat source with a focused spot diameter is assumed along the kerf surface at the cut edge, resembling the laser heat source. The equations for energy and thermal stresses are solved numerically using the finite element method (FEM). It is found that the temperature decays sharply in the vicinity of the cut edges and that the equivalent stress attains high values in this region. Inconel 625 results in the highest thermal stress levels in the vicinity of the cut edges and is then followed by steel and titanium alloy.     

正交切削高强耐磨铝青铜的有限元分析

采用热力耦合、平面应变、连续带状切屑的切削模型模拟了高强耐磨铝青铜的正交切削加工过程。采用增量步移动刀具的方法,结合有限元分析软件Marc的网格重划分功能,模拟了刀具从初始切入到切削力和切削温度达到稳态的切削加工过程,获得了不同切削深度和切削速度下的切屑形态、温度、应力、应变和应变速率的分布。并将模拟计算得到的切削力和切削温度与试验结果进行了比较,两者具有较好的一致性。     

高速硬态切削工件表层显微硬度与白层研究

高速和硬态切削使得工件已加工表面及其表层中出现特有的现象.研究结果表明,切削速度和材料硬度是决定高速和硬态切削工件已加工表面及其表层结构形成的主要影响因素,切削热使被切削材料产生高温软化,刀具挤压摩擦使被切削材料变形加剧,工件表层材料显微硬度分布发生改变,出现了硬脆的白层组织,白层组织的出现将对零件的使用将造成不利影响.随着切削用量和材料硬度增大,切削变形增大,切削温度升高,白层厚度增大,工件表层材料显微硬度提高.抑制白层组织产生的措施是对工件降温.     

Fundamental investigation on partially overlapped nano-cutting of monocrystalline germanium

Molecular dynamics simulations on partially overlapped nano-cutting of monocrystalline germanium with different feeds are carried out to investigate the surface topography, cutting force and subsurface deformation. The results indicate that the side-flow material piling up on the edges of tool marks is a decisive factor for the surface topography with the machining parameters in this study, ignoring the tool wear and machining vibration. In the partially overlapped nano-cutting, the lateral force is more affected by nominal depth of cut than by pitch feed with the value of feed being in some range. The atomic sights on the subsurface deformation show that the thickness of deformed layer after machining is much thinner than that after single cut with the same nominal depth of cut. Laser micro-Raman spectroscopy and cross-sectional transmission electron microscopy are used to detect the subsurface deformation of monocrystalline germanium after eccentric turning. The crystalline structure with defects rather than the amorphous germanium is observed in many areas of machined surface. Both molecular dynamics simulation and experimental results indicate that the amorphous-damage-less and even amorphous-damage-free machined surface can be achieved by partially overlapped nano-cutting.     

EXPERIMENTAL RESEARCH OF NANO-CUTTING BY USING SCANNIN G PROBE MICROCOPE

0 INTRODUCTIONNanotechnolOgy becomes particularly interestingnowadays, because the increasing needs of itsapplications are demanded with the development ofhish technology, not only in scientific but also inengineering field, esPecialy in electronic and opticalindustries. As long as nanotechnology is mentioned, itwill be concerned that machining at nanometer scale,which is sometimes called "nanomachining". Thereare two similar ultra-precision machining inconventional method, i. e. ultrapre…     

刚性的球头铣刀切削力模型

基于切削力与切屑负载之间的经验关系,通过对球头铣刀的微分化方法,建立了球头铣刀基本切削力模型,并着重研究刀具的径向跳动对径向未变形切屑厚度的影响,提出了刚性的球刀铣刀切削力模型,最后用切槽实验对模型进行了验证。     

Study on Cutting Force,Cutting Temperature and Machining Residual Stress in Precision Turning of Pure Iron with Different Grain Sizes

Pure iron is one of the di cult-to-machine materials due to its large chip deformation, adhesion, work-hardening, and built-up edges formation during machining. This leads to a large workpiece deformation and challenge to meet the required technical indicators. Therefore, under varying the grain size of pure iron, the influence of cutting speed, feed, and depth of cut on the cutting force, heat generation, and machining residual stresses were explored in the turning process to improve the machinability without compromising the mechanical properties of the material. The experimental findings have depicted that the influence of grain size on cutting force in the precision turning process is not apparent. However, the cutting temperature and residual stress of machining fine-grain iron were much smaller than the coarse grain at all levels of cutting parameters.     

Force Modelling for Cylindrical Plunge Cutting

This paper described the development of an analytical model for the cutting forces in multiblade plunge cutting of cylindrical parts. The development uses the relationship between the instantaneous chip area and the local cutting forces at each individual blade to formulate the total resultant forces via kinematic integration along the cutting edges. The model expresses the cutting forces in explicit terms of part material properties, cutter geometry, part geometry, and cutting conditions. Experiments were performed under various cutting conditions to verify the fidelity of the model at different stages of cutter-part engagement. The waveform and amplitude characteristics of the model-predicted forces agree closely with the measurement. The model can facilitate tool geometry design and cutting condition planning in light of the optimisation of cutting forces.     

基于滑—停—滑机理的锯齿形切屑高速成形分析

高速车削时被切削材料以极高的应变速率产生连续的塑性变形,产生大量的切削热,在出现集中剪切滑移的情况下,产生了连续型带状锯齿形切屑。根据高速外圆车削中碳淬硬钢切屑试样的SEM照片和金相显微组织照片分析了锯齿形切屑周期性形成的变形机理。被切削材料的变形过程由普通的剪切滑移变形和集中剪切滑移变形组成,切屑沿前刀面的流出可细分为“滑—停—(再)滑”三个阶段。切削速度和材料硬度是决定切屑变形的两个主要影响因素。只要能够使材料应变率增加、致使切削温度升高的因素改变达到某种临界状态都能促成锯齿形切屑的形成,锯齿形切屑的形态随着切削用量的改变而变化。     

Orthogonal cutting of polyurethane foam

This study describes orthogonal cutting experiments performed on rigid polyurethane foams of various densities and cell sizes, to investigate chip formation and surface finish. An optical arrangement was used to visually record the cutting process, while horizontal and vertical cutting forces were measured. A total of 239 measurements were performed with tool rake angles of 23, 45 and 60, and depths of cut in the range of 0.1–3 mm. Continuous and various modes of discontinuous chip formation were identified. While continuous chip formation resulted in smooth surfaces, discontinuous chip formation was often associated with surface damage in the form of cratering, as a result of crack propagation. Results from experiments and modelling suggest that the transition between chip types was dependent on depth of cut, rake angle and cell size. It is concluded, that surface finish is primarily dependent on cell size and depth of cut. Continuous chip formation developed with a depth of cut between one and two times the cell diameter resulted in the lowest surface roughness.