微织构刀具连续磨损建模与仿真研究

建立切削过程中的微织构刀具连续磨损有限元模型一直是难点。为分析微织构刀具连续磨损问题,基于能量损失法,在有限元分析软件中建立了硬质合金刀具微切削Ti6Al4V钛合金材料过程中的微织构刀具连续磨损模型,并在刀具前刀面不同位置分别设计单个和多个微织构模型,分析微织构对刀具前刀面月牙洼磨损和后刀面磨损的影响。有限元分析结果表明,前刀面的微织构数量和位置对刀具的磨损程度有严重影响;刀具表面温度是影响月牙洼磨损深度的关键因素;而月牙洼磨损中心到切削刃刀尖的磨损与刀具的Mises应力有直接关系;影响刀具的后刀面磨损主要因素是刀具压力。     

冷却方式对H13A硬质合金切削性能试验分析

在MAZARK车铣加工中心和高速铣床上选用切削速度150m/min和200m/min进行顺铣干/湿切削加工,采用H13A硬质合金刀具对TC4钛合金进行高速车铣和高速铣削加工试验。分别对比分析两种加工方式下冷却方式不同时的刀具磨损形态,结果表明:干切削时,无论正交车铣或高速铣削,刀具都是以粘结磨损为主;正交车铣干切削时,刀具表面有较多的切屑粘结物,易形成积屑瘤;切削液条件下,刀面粘结物相对减少,切屑粘走刀具材料,形成较多的粘结凹坑;铣削干切削时,粘结到刀面的切屑较正交车铣少,但切屑粘走刀具材料更为严重,前刀面出现较深的月牙洼,采用切削液时前刀面出现层状剥落。试验表明,当金属切除率一定时,正交车铣干切削金属切出总量最大,刀具寿命最长,湿切削加工时刀具寿命较短,切削液对刀具磨损形态和刀具寿命影响较大,可能与热交变应力和Co元素流失有关。试验结果表明,H13A刀具正交车铣钛合金干切削时切削性能较好。     

基于高斯过程回归方法的钛合金铣削刀具磨损预测

通过钛合金材料切削试验,对铣削加工中切削参数对高进给铣刀刀齿后刀面最大磨损量的影响规律进行分析。采用高斯过程回归法建立了刀齿后刀面最大磨损宽度的预测模型,并进行试验验证。预测结果与试验结果吻合程度较高,验证了预测模型的有效性,为钛合金铣削刀具的磨损预测提供了理论方法和试验依据。     

金属切削中刀具月牙洼磨损模型的研究

刀具的前刀面月牙洼磨损和后刀面磨损在刀具磨损的研究中占据同等地位,但月牙洼磨损轮廓和刀屑交界面上的切削过程变量不易测量等因素,导致真正依据月牙洼磨损测试获取月牙洼磨损模型的研究非常少。基于硬质合金刀具切削低碳钢的月牙洼磨损实验,提出了一个经验磨损模型。该模型综合了黏结磨损和扩散磨损,考虑了刀屑交界面温度和压力对月牙洼磨损的影响。研究结果表明,该模型能够分析并预测相似切削条件下的月牙洼磨损轮廓。     

TC4钛合金切削刀具磨损对切削过程影响的研究

通过建立的钛合金切削加工仿真数值模型,研究了刀具磨损对钛合金切削过程中切削力、切削温度及切屑形态的影响规律,并对这些影响的产生机理进行了讨论。结果表明:随着磨损程度的增大,切削力及切削温度会迅速增加;月牙洼磨损会引起切削力的剧烈震荡且振幅随磨损的增大而增大,后刀面磨损将增大切削力;锯齿形切屑的变形程度在加大,但是锯齿产生的频率在降低。     

高速铣削Ti-10V-2Fe-3Al的刀具磨损试验研究

针对切削加工Ti-10V-2Fe-3Al钛合金时刀具磨损迅速、加工效率低的问题,开展硬质合金刀具高速铣削Ti-10V-2Fe-3Al的刀具寿命试验,以研究刀具的磨损机理,分析刀面磨损的发展以及对切削力的影响。利用扫描电子显微镜观察了后刀面磨损区域的微观形貌并对元素成分进行了能谱分析。实验结果表明：高速铣削Ti-10V-2Fe-3Al时硬质合金刀具的磨损形式为后刀面带状磨损与局部崩刃,伴有明显的切屑黏附与热裂纹;磨损区域有工件材料的元素向硬质合金内扩散的迹象出现;切屑流的黏附与撕扯导致硬质合金的颗粒脱落,切削刃逐步退化为洼形区域,其与后刀面交界的棱边代替原切削刃进行切削直至剥落。     

陶瓷刀具车削TC4钛合金磨损特性的研究

为研究陶瓷刀具切削钛合金的磨损机理,采用CC6060陶瓷刀片对TC4钛合金进行了干式车削试验。结果表明:陶瓷刀具干式切削TC4钛合金时,磨损形貌以前刀面月牙洼磨损、后刀面沟槽磨损和刀尖破损为主,磨损机理主要是粘结磨损和氧化磨损。随着切削速度的增加,刀具磨损加剧,刀具寿命降低。CC6060陶瓷刀片干式切削钛合金时的使用寿命很低,不适于干式切削钛合金。     

硬质合金刀具高速车铣和铣削TC4钛合金磨损试验对比

采用H13A未涂层硬质合金刀具对TC4钛合金进行高速正交车铣和铣削试验,并从刀具磨损破损形态、磨损机理及其寿命等方面进行对比分析。研究表明:高速正交车铣和铣削钛合金时,前、后刀面主要以粘结磨损为主,车铣加工时在切削刃口易形成积屑瘤及连续切屑,但对刀具材料粘结较轻;高速铣削时,对刀具材料粘接较重,在前刀面刃口附近形成凹坑及崩刃;后刀面最大磨损的位置不相同。试验对比了相同切削条件时刀具使用寿命,结果表明采用正交车铣加工可以获得更长的刀具使用寿命。     

TiAlN涂层硬质合金可转位刀具快速铣削钛合金刀片磨损研究

快速铣是一种新兴的粗加工方法,研究它的刀具磨损机理对提高刀具寿命和加工效率有着重要的作用。采用硬质合金快速铣刀片在工件上进行了钛合金TC17铣削实验,研究了不同切削参数对切削力的影响,采用多元线性回归建立了切削力数学预测模型,分析了各铣削参数对切削力的影响规律,通过对后刀面的检测,分析了刀具磨损形貌和磨损机理。结果表明:每齿进给量、切削深度对切削力的大小影响显著,切削宽度和主轴转速影响很小,在试验参数范围内,选用切削参数组合为:f_z=0.8 mm/z、a_p=0.5 mm、a_e=20 mm、s=600 r/min进行可转位刀片的磨损试验,快速铣可转位刀片的主要磨损形貌为后刀面磨损、材料剥落,后刀面主要磨损机理为黏结磨损,同时会产生一定程度的扩散磨损。     

钛合金高速旋转超声椭圆振动侧铣削切屑特征和刀具磨损研究

难加工材料钛合金在采用传统铣削方式时,随着切削速度的增加,切削力和切削温度都迅速增加,使得切削条件恶化并加速刀具磨损,从而导致刀具过早失效。将超声椭圆振动加工技术引入到高速铣削中,进行了钛合金高速旋转超声椭圆振动侧铣削试验。从切屑特征以及刀具后刀面磨损两个方面研究了高速超声椭圆振动铣削参数匹配对钛合金加工的影响。首先基于高速超声椭圆振动铣削过程中刀具-工件的运动学特点推导出高速超声椭圆振动铣削加工参数与振动参数间的匹配关系,然后利用本实验室自行研制的超声椭圆振动铣削装置进行了不同参数匹配关系下的验证性切削试验。试验结果表明：合理的参数匹配使得超声椭圆振动铣削在高速条件下依然能够实现分离型断续切削加工。相比普通铣削加工,分离型的高速超声椭圆振动铣削能够获得更加微细的切屑,切削热能够被及时地带走;良好的切削条件使得刀具的后刀面磨损均匀而缓慢,从而延长刀具的使用寿命;高速超声椭圆振动铣削能够有效地提高生产效率。     

Investigation on diffusion wear during high-speed machining Ti-6Al-4V alloy with straight tungsten carbide tools

During high-speed machining Ti-6Al-4V alloy, high-temperature at the tool–chip interface and the concentration gradient of chemical species between tool material and workpiece material support the activation of diffusion process, and therefore the crater wear forms on the rake surface of the cutting tool at a short distance from the cutting edge. In this paper, the diffusion analysis was theoretically proposed. The constituent diffusion at the contact interface between tool material and Ti-6Al-4V alloy at high-temperature environment, the crater wear on the rake surface of the tool, and the chips collected from high-speed milling Ti-6Al-4V alloy with straight tungsten carbide tools were analyzed by the scanning electron microscope with energy dispersive X-ray spectroscopy. The constituents inside the tool could diffuse into the workpiece and the diffusion layer was very thin and close to the interface. Compared with the diffusion of tungsten and carbon atoms, the pulling out and removing of the tungsten carbide (WC) particles due to cobalt diffusion dominated the crater wear mechanism on the rake surface of the cutting tool.     

Experimental Study on Wear Characteristics of PCBN Tool with Variable Chamfered Edge

Owing to heavy dynamic and thermal loads, PCBN tools are seriously worn during hard cutting, which largely constrains the improvement of their machining performance. Therein, the chamfered structure of a cutting edge has a notable influence on the tool wear. Thus, a comparative study was carried out on the wear morphology and wear mechanism of PCBN tools with either a variable chamfered edge or an invariable chamfered edge. The results indicate that, for a PCBN tool with a variable chamfered edge, the rake wear area is far from the cutting edge and slowly extends toward it. A shallow large-area crater wear occurs on the rake face, and the flank wear area has a long triangular shape with a smaller wear area and width, and the cutting edge remains in a good state during the cutting process. In contrast, for a PCBN tool with an invariable chamfered edge, a deep small-area crater appears on the rake face,and the wear area is close to the cutting edge and quickly extends toward it. Thus, it is easy for chips to accumulate in the crater, resulting in large-area and high-speed wear on the flank face. In addition, the tool shows a weak wear resistance. In the initial wear stage, the rake wear mechanism of the two cutting tools is a mixture of abrasive, oxidation, and other types of wear, whereas their flank wear mechanism is dominated by abrasive wear. With an aggravation of the tool wear, the oxidation and di usion wear mechanism are both increasingly strengthened. The rake wear of the cutter with a variable chamfered edge showed an obvious increase in the oxidation and di usion wear, as did the flank wear of the cutter with an invariable chamfered edge. This study revealed the wear mechanism of the PCBN tool with a variable chamfered edge and provided theoretical and technological support for its popularization and application in the machining of high-hardness materials.     

The effects of progressive tool wear and tool restricted contact on chip breakability in machining

Chip breakability plays an essential role in automated machining systems. This paper presents an experimental investigation of the effects of progressive tool wear and the resulting formation of the tool restricted contact on chip breakability in a turning operation. Six parameters of tool wear, namely, major flank wear (VB), crater wear depth (KT), crater wear length (KK), crater wear width (KB), wear retract of cutting edge (KS) and nose wear (N), are shown to contribute to the variations of chip breakability with tool wear progression. The results show that the chip breakability varies significantly with tool wear progression, especially with the combined crater and flank wear progression, and contributes to the development of a restricted rake face land, making the tool behave like a restricted contact grooved tool. The chip curling and breaking action is largely influenced by the nature and magnitude of the restricted contact and the groove profile being developed on the tool face. The results presented in this paper are also intended to provide guidelines for designing effective chip grooves on the tool face.     

Crater and flank wear resistance of cutting tools having micro textured surfaces

We have proposed cutting tools with various textured surfaces to increase cutting tool life. Our previous studies have developed cutting tools having periodical stripe-grooved surfaces on their rake face formed using femtosecond laser technology, which displayed high crater wear resistance in cutting of steel materials. In this study, the mechanism for suppressing the crater wear on the tool surface and the relationship between texture dimensions and wear resistance were investigated to provide a guideline for developing tools with textured surfaces. Furthermore, we newly introduced the textured surfaces into a flank face of cutting tools to improve flank wear resistance. Face milling experiments on steel materials exhibited that the newly developed tool having the textured flank face significantly reduced the flank wear. Moreover, the influences of texture dimensions and cutting conditions on the flank wear resistance were also discussed.     

铁基粉末冶金材料的高速干切削试验研究

用陶瓷刀具、涂层刀具和硬质合金刀具进行了铁基粉末冶金零件的干切削对比试验,研究了切削速度、切削深度以及进给速度与刀具耐用度和加工表面粗糙度的关系,分析了陶瓷刀具的磨损机理。结果表明所选用陶瓷刀具的切削性能明显优于涂层刀具和硬质合金刀具;陶瓷刀具前刀面主要磨损形式为月牙洼磨损与剥落,后刀面的主要磨损原因为磨粒磨损;认为陶瓷刀具更适合用于粉末冶金零件的切削加工。     

TC4钛合金深槽插铣加工

针对钛合金深槽开槽加工效率较低的问题,对TC4钛合金深槽进行插铣开槽试验研究,并对其已加工表面形貌、切屑形态、刀具磨损及切削效率进行了分析。结果表明:插铣加工表面粗糙度较大,铣刀的端面刃为主切削刃,刀具磨损主要发生在铣刀的端面刃。对于钛合金深槽的开槽加工,插铣加工切削过程平稳,具有比层铣更高的切削效率。     

基于“差分”磨损模型的车削刀具磨损仿真预测研究

研究表明,切削过程中的刀具磨损与刀面温度、刀/屑和刀/工界面的接触压力及相对滑动速度等切削过程变量有关,借助于有限元分析法可对这些切削过程变量进行仿真预测。基于“差分”磨损模型,提出了一种对切削过程中刀具轮廓磨损变化的预测方法,以硬质合金刀具切削AISI1045材料为例,介绍了该方法的原理和实施步骤,并对刀具前后刀面磨损的预测结果进行了试验验证,分析了预测结果与试验结果存在误差的原因。     

高速干切削铁基粉末冶金零件时细晶粒硬质合金刀具的切削性能研究

用细晶粒硬质合金刀具进行了铁基粉末冶金零件的高速干切削试验。研究了切削参数与刀具耐用度以及加工表面粗糙度的关系,给出了刀具的主要磨损形态,通过能谱分析研究了刀具的磨损机理。结果表明:所选用细晶粒硬质合金刀具具有较高的刀具耐用度和较好的加工表面粗糙度,适合于铁基粉末冶金的加工;细晶粒硬质合金的主要磨损形态是前刀面的月牙洼磨损;主要磨损机理是扩散磨损、粘结磨损。     

A FINITE ELEMENT ANALYSIS OF BURR FORMATION IN FACE MILLING OF A CAST ALUMINUM ALLOY

The research discussed in this article focuses on the effects of tool geometry (i.e., rake angle and cutting edge radius) and flank wear upon burr formation in face milling of a cast aluminum alloy. As to tool edge preparation, the use of a tool with variable cutting edge radius was investigated using FEM, and compared for its cutting performance (i.e., burr reduction and tool life) with a conventional tool with uniform cutting edge radius. In order to evaluate 3D face milling through 2D orthogonal cutting simulations, the cross-sections that consist in the cutting speed direction and chip flow direction were selected at different locations along the tool rounded corner. At these cross-sections, the local value of cutting edge radius and their associated tool rake angles as well as the effective uncut chip thickness were determined for 2D cutting simulations. In addition, 3D face milling simulations were conducted to investigate more realistic chip flow and burr generation. Comparisons were made for burrs produced from 3D simulations with a sharp tool, 3D simulations with a worn tool and face milling experiments. Finally, recommendations for cutting tool design are made to reduce burr formation in face milling.