新型微坑车刀切削304不锈钢降温机理分析研究

切削304不锈钢时,刀具温度高达750℃,高温集中在刀具切削刃近域,这加速了刀具的磨损,缩短了刀具的寿命。为了减小该区域的摩擦状况,降低该区域切削过程的温度,在刀具切削刃近域进行微坑结构设计。应用微坑车刀和原车刀切削304不锈钢,经仿真分析和切削实验,发现微坑车刀较原车刀,切削力降低,切削温度降低。通过切削力学模型分析、刀屑摩擦模型的研究和刀具磨损的对比,得出微坑车刀切削温度降低的形成机理。     

复合织构刀具切削铝合金的性能∗

基于铝合金材料切削的现状和需求,针对单一织构刀具存在的抗黏减摩性能不足的问题,将不同织构应用于刀-屑接触区域,提出刀具前刀面分区异构的思想。利用皮秒激光在刀具黏结区与滑移区分别加工凹坑和沟槽,并调整沟槽的取向(平行 / 垂直于主切削刃),得到上下型(SXDV 和 SXDP)和左右型(ZYDV 和 ZYDP)四种复合织构刀具。对 6061 铝合金进行湿切削试验,研究不同区域内添加不同织构对刀-屑接触表面摩擦状态的影响。研究结果表明,对比无织构和单一织构刀具, ZYDP 复合织构刀具展现了更好的切削性能。具体表现如下：与无织构刀具相比,ZYDP 刀具的主切削力降低 30.7%,刀面黏结面积减少 63.9%,切屑卷曲半径减少 27.4%。合理的复合织构方案可以明显改善刀具切削过程中的黏结磨损问题,延长了刀具寿命。复合织构方案的提出以及相应的激光加工过程可为织构刀具的设计及实际应用提供新思路。     

基于Workbench的微织构刀具对铝合金切屑影响

针对6061铝合金切削过程中加工表面质量较差、切屑缠绕的实际情况,以仿生摩擦学理论为基础,利用ANSYS Workbench仿真软件,重点研究了刀-屑之间摩擦应力状况;同时,借助微织构硬质合金(WC-Co,YG8)刀具进行铝合金切削实验,研究不同尺寸和结构特征的微织构对铝合金切屑形貌的影响。研究结果表明:梯状微织构刀具尺寸为直径d=65μm、深度h=15μm时,刀屑之间最大摩擦应力下降21.8%,锯齿状切屑控制良好,齿高降幅52.5%,剪切角降幅31.6%,锯齿角降幅9.5%;存在细长型和粗壮型两种树杈状切屑,并得到良好控制,细长型切屑降幅达到95%,粗壮型切屑降幅87.5%,抑制效果明显。同时研究发现:微织构刀具下,切屑形貌严重影响加工表面质量,良好的切屑形貌,能够降低刀-屑之间镶嵌粘焊概率,减小加工过程中振幅和频率,使加工更加流畅,得到良好的加工表面质量。     

微织构铣刀干铣削RuT500切削性能研究北大核心

为探究微织构对刀具加工蠕墨铸铁RuT500切削性能的影响,改善RuT500的可加工性,利用激光技术在刀具前刀面制备了3种形式的微织构并通过单因素试验方法,在不同切削速度下将微织构刀具和无织构刀具对RuT500进行铣削加工,对比分析了微织构的方向和类型在加工中切削性能的差异。结果表明,表面微织构可以有效降低切削力,改善切屑形态和工件表面质量,在一定程度上降低了前刀面磨损;3种微织构在部分相同切削速度下对切削性能的影响有较大差别;切削速度较大时,微织构更有利于RuT500的切削加工。在3种微织构中,以平行于主切削刃的沟槽织构刀具切削性能最优。     

涂层硬质合金刀片微槽微织构复合设计

文章在涂层硬质合金刀片前刀面切屑刃近域微槽设计基础上,为了更好的降低刀片的切削温度,设计了(条纹型、波纹型、梳齿形)三种微织构形式,并将之与微槽复合形成刀具前刀面微结构造型,通过DEFORM3D仿真实验,研究了三种微织构参数对降温效果的影响,分别优选出三种微槽微织构复合刀具,并对比分析所优选出的三种微槽微织构复合刀具与原刀具及微槽刀具切削力及已加工表面残余应力。研究表明:新的微槽微织构复合设计均具有一定的降温效果,梳齿形微槽微织构降温效果最好;波纹型微织构的置入能够有效减低刀具的切削力,减少切削热的产生,而条纹型微织构的置入可以有效减少切削热向刀具的传递,从而降低刀具切削温度;与原刀相比,优选出的三种微槽微织构刀具能够有效增大工件表层的残余压应力。     

切削速度对微织构刀具切削力的影响

目的 研究微织构刀具在不同切削速度下切削力的变化规律,从而改善刀具的切削性能。方法 利用激光技术在PCBN刀具前刀面进行微织构处理,加工微槽宽度分别为30、40 μm的垂直微槽和平行微槽,并选择60、72、85 m/min三种不同的切削速度,分别用微织构PCBN刀具干式切削AISI 52100材料,使用测力仪收集切削过程产生的主切削力、径向力和轴向力。结合有限元仿真技术,设置与实际切削试验相同的切削用量、微织构刀具材料和工件材料等切削条件,从刀具表面应力角度分析微织构刀具在不同切削速度下的切削力变化,并与切削试验结果进行对比。结果 在不同的切削速度条件下,不同微织构刀具产生的切削力受切削速度的影响程度不同。30 μm垂直微槽和40 μm平行微槽PCBN刀具在较高的切削速度下均能取得较小的切削力,切削速度的变化对主切削力、径向力和轴向力的影响均较大。结论 随着切削速度的增大,垂直微槽和平行微槽可有效减小主切削力和径向力。在相同的切削速度下,垂直微槽比与平行微槽更有利于获得较小的切削力。试验结果对微织构PCBN刀具切削淬硬钢材料奠定了基础。     

表面微织构在切削过程中的研究进展

在切削过程中,临近切削刃的刀具前刀面与切屑、刀具后刀面与已加工表面接触区存在的高温高压情况严重影响了刀具服役寿命和工件表面完整性。表面微织构技术是一种先进的表面改性技术,在刀具表面制备不同尺寸参数、形状参数、分布参数的表面织构能够显著影响刀具的切削性能。当刀具表面微织构制备方法不同时,微织构所呈现的性能也不同。首先从制备技术的原理、制备过程、制备技术特点等方面对当前最先进的刀具表面微织构制备技术进行了综述。然后从切削力、切削温度、刀具磨损、切屑形成、工件表面完整性等角度分析了微织构对刀具切削性能的影响规律与机理。在分析切削力、切削温度、刀具磨损、切屑形成等4个指标时重点关注了刀具前刀面微织构所起的作用,在分析工件表面质量时,同时考虑了刀具后刀面微织构、前刀面微织构的影响。最后,介绍了当前微织构的研究热点,主要包括微织构技术与钝化刃口、润滑剂的协同作用对切削性能的影响,以及微织构刀具在切削过程中发生的衍生切削行为。通过对文献的归纳、总结与深入分析,给出了表面微织构未来的研究方向,为刀具进一步优化提供设计参考。     

微织构刀具DEFORM-3D切削性能仿真分析及实验研究

运用DEFORM-3D仿真软件对YG8硬质合金微织构刀具的切削性能进行仿真分析,研究了YG8硬质合金刀具在沟槽微织构、凹坑微织构和无微织构3种表面微织构下的切削温度和切削应力.利用激光加工技术对YG8硬质合金刀具表面进行沟槽微织构的加工,运用该刀具对铝合金进行切削实验,分析微织构对刀具切削性能的影响.结果表明:微织构刀具产生的切削热更少,与切屑间的摩擦力更低.在一定的润滑条件下,微织构刀具具有更好的切削性能.     

YG8硬质合金微织构刀片的切削性能研究

通过摩擦磨损试验初定表面微织构参数,在此基础上制备了沟槽型微织构,并对TC4钛合金进行了正交切削试验,优化了微织构参数,研究了微织构深度、宽度与间距在有切削液润滑下对YG8刀具切削性能的影响。试验结果表明:表面微织构对于切削力影响不大,但可明显减小进给抗力,因而降低摩擦因数,改善刀屑间的摩擦状况,减缓刀片表面磨损。最多可降低19. 20%的摩擦因数并降低31. 8%的后刀面磨损。后刀面加工表面微织构会降低刀刃附近强度,造成更大的磨损。     

基于ANSYS/Workbench不同微织构刀具强度有限元分析

仿生摩擦学研究表明在刀具表面置入微织构纹理可以改善外圆车刀在切削时的摩擦状况,但是置入的微织构纹理会对刀具的结构强度产生一定的影响。针对微坑织构、凸包织构和条纹织构纹理进行了刀具的建模并利用 ANSYS ／Workbench 对不同微织构纹理刀具进行有限元分析。结果表明：在微织构的深度、间距尺寸一致的情况下,微坑织构纹理对刀具的应力影响程度较大,条纹织构纹理的影响程度较小,3种织构纹理对刀具的变形影响相差不大,综合比较条纹织构对刀具强度影响较小。     

微织构刀具切削性能及减摩效果的仿真分析

目的研究3种不同类型微织构在钛合金(TC4)切削过程中对刀具切削性能的影响。方法基于有限元分析软件,在硬质合金刀具的前刀面上设计半圆凹型微织构、半圆凸型微织构以及梯形槽微织构3种不同类型的微织构,通过改变微织构直径或宽度、微织构间距和微织构覆盖长度,研究微织构刀具对背向力、切削温度以及摩擦力的影响。结果对背向力而言,半圆凹型微织构刀具、半圆凸型微织构刀具、梯型槽微织构刀具在最佳微织构参数下可分别降低14.0%、13.9%、18.6%;但半圆凸型微织构直径大于8μm时,背向力超过了无织构刀具。对切削温度而言,3种微织构刀具在最佳微织构参数下可分别降低5.9%、10.7%、9.6%。对刀具所受摩擦力而言,3种微织构刀具在最佳微织构参数下可分别降低23.0%、27.7%、21.9%。结论合理的表面微织构能够改善刀具的切削性能。梯型槽微织构刀具降低背向力效果最佳;半圆凸型微织构刀具降温和减摩效果最佳。刀具切削性能随微织构直径和微织构间距的增加呈先减小后增大的趋势,且存在最优的微织构参数。在刀-屑接触长度范围内,微织构覆盖长度越长,减摩效果越好。     

基于微磨削方法的微织构刀具制备与切削性能研究

目的研究表面微织构对硬质合金刀具切削性能的影响。方法采用微磨削方法在硬质合金刀具前刀面加工出具有不同结构参数的横向、纵向和交叉微织构,通过AL6061切削试验和有限元切削仿真,研究表面微织构对硬质合金刀具的切削温度及刀具磨损的影响。结果采用V形金刚石砂轮微磨削方法能够加工出几何形状规则且表面质量良好的表面微织构。与无织构刀具相比,微织构刀具的切削温度明显降低,高温区域明显减少,其中横向织构刀具降温效果最为显著。微织构刀具的切削温度随沟槽间距的增大而升高,沟槽间距为150μm时,切削温度最低。表面微织构能够有效减轻刀具前刀面的粘结磨损,横向织构刀具减摩抗粘效果最好,且采用较小的沟槽间距更利于减轻刀具的粘结磨损。随着切削速度的增加,表面微织构的抗粘结作用更加明显,当切削速度为150 m/min时,沟槽间距为150μm的横向织构刀具的切屑粘结面积最小。结论在横向、纵向和交叉织构刀具中,沟槽间距为150μm的横向织构刀具切削性能最好,即降温效果、抗粘结性能最为显著。     

Analysis of a new Segmentation Intensity Ratio “SIR” to characterize the chip segmentation process in machining ductile metals

In machining, chip morphology has an important effect on several cutting parameters such as tool wear, chip flow, vibration, etc. This research work aims to analyse the chip segmentation phenomenon for ductile metals. The aeronautical aluminium alloy A2024-T351 has been selected for the study. Using Finite Element modelling, segmentation process has been analysed and quantified with a new physical parameter called “Segmentation Intensity Ratio”. The SIR parameter which leads to a better analysis of the chip morphology is defined as a ratio between the equivalent plastic strain inside and outside shear bands within the chip. Using this parameter the effect of cutting conditions and tool geometry on the chip segmentation can be clearly shown. Also the fluctuation of the contact length, the tool-chip interface temperature as well as the cutting force oscillations with respect to cutting speed are carefully discussed when segmentation occurs. A correlation between chip formation process and cutting force oscillation is established as well as a correlation between average cutting force reduction and segmentation intensity when cutting speed increases. Finally, a parametric analysis was conducted to highlight the effect of the friction on the chip segmentation intensity.     

An analytical model for the optimized design of micro-textured cutting tools

Proper design of micro-textured cutting tools is an effective strategy to improve the machining performance by reducing the tool-chip contact length and the resultant friction and thus improving tool life and workpiece surface integrity. In this paper, an Oxely-based analytical model is developed to optimize micro-textured cutting tool design(s) which eliminate the occurrence of derivative cutting. The model accommodates any workpiece material, tool geometry, and machining parameter. The model was validated by orthogonal cutting of AISI 1045 steel tubes. The results show that the optimum micro-texture design eliminates derivative cutting and lowers forces compared to the non-textured cutting tool.     

A finite element analysis of temperature in accelerated cutting

Temperature attained during machining has significant effects on the properties of tool, chip and workpiece. It governs the parameters like shear angle, cutting force, tool wear, surface finish etc. Review of literature reveals that hardly any information is available about the analytical determination of the tool-chip interface temperature and the temperature distribution during the accelerated cutting.

This paper presents the temperature analysis of accelerated cutting (i.e. taper turning and facing) as well as longitudinal turning, using the finite element technique. It has been concluded that the temperature distribution within the tool-chip-work system and the average tool-chip interface temperature for the two classes of machining (viz longitudinal turning and accelerated cutting) are not the same, even though the conditions of machining are identical. Further, the average tool-chip interface temperature is lowest in case of facing and highest in case of longitudinal turning.     

微织构刀具对工件表面残余应力影响有限元分析

针对微织构刀具对切削工件表面残余应力的影响,设计不同尺寸的垂直槽和平行槽微织构,利用有限元仿真技术,模拟不同类型、不同尺寸微织构PCBN刀具干式车削GCr15试验。通过对有限元结果进行研究分析,得到已加工表面残余应力分布情况,并与无织构PCBN刀具对比,分析微织构对已加工表面残余应力的影响。有限元仿真结果表明:与无织构刀具切削工件表面获得拉应力相比,槽型织构刀具切削后的工件已加工表面呈现压应力,提高工件表层的耐磨损和耐疲劳性能;宽度50μm垂直槽和宽度40μm平行槽刀具切削得到的工件表面压应力最大,对工件表面应力分布影响最显著。     

Advanced Tool Edge Geometry for High Precision Hard Turning

The hard turning process has been attracting interest in different industrial sectors for finishing operations of hard materials. However, it still presents disadvantages with respect to process capability and reliability. In this paper the impact of PcBN tool edge geometry is investigated based on a modelling as well as an experimental approach. The hard turning process is described by means of a 3D simulation of the tool engagement based on the Finite Element Method. The simulation results indicate force and temperature distribution in the tool-chip contact zone for different designs of PcBN tool cutting edge, thus allowing the derivation of criteria for an advanced tool edge design.The recommendations for tool edge geometry modification are experimentally verified. The results suggest that the use of the proposed new tool edge geometry is an effective way to significantly increase tool performance with respect to tool life, material removal rate and part surface quality in high precision hard turning.     

Fabrication techniques and cutting performance of micro-textured self-lubricating ceramic cutting tools by in-situ forming of Al2O3-TiC

In this study, different geometric micro-textured ceramic tools (MST-0, MST-1, MST-2) are designed using the software AdvantEdge (AE). The designed tools are used to perform FEM (finite element modelling) simulation of the cutting process. The simulation results show that, compared with the traditional non-texture tool (MST-0), applying the appropriate shape and size of micro-texture to ceramic cutting tools can significantly reduce the cutting force, decrease the cutting temperature and improve the cutting performance of the tool. Additionally, an experimental study was conducted that involved the fabrication of hot-pressing sintered micro-textured self-lubricating ceramic tools (MST-1, MST-2) by means of in-situ forming method. Furthermore, cutting tests to compare the cutting performance of the micro-textured self-lubricating ceramic tools with the traditional non-textured tool (MST-0) were performed. The results indicate that the in-situ formed micro-textured ceramic cutting tools can effectively reduce the cutting force, the cutting temperature, and the rake face wear. During the cutting process, the abrasive grain of graphite that is placed into the micro-texture by in-situ forming is squeezed into the microstructure. Thus, the graphite overflows from the microstructure under abrasive grains and covers the rake face. This helps to reduce the friction between the chip and the rake face, which further reduces the cutting force and temperature, and improves the cutting performance of the tools. The texture pattern orientation of the micro-texture also affects the cutting performance of the tool. It is found that the best cutting performance is obtained by the transverse micro-texture tool.