硬质合金可转位车刀片UG型断屑槽断屑机理的研究

本文采用接触图形法对硬质合金可转位车刀片UG型断屑槽的断屑机理进行了实验研究．结果表明：由于采用了根据不同切削深度和进给量巧妙改变有效槽宽、使切屑横截面弯曲呈拱形、弹形挡屑筹措施，UG型断屑槽具有断屑范围较宽、在进给量较大时不易出现过分断屑等特点．此外，文中还对化学气相涂层刀片的UG型断屑槽在切削速度明显提高以后断屑范围的变化进行了研究．文中给出的UG型断屑槽的断屑范围图可供实际选用．     

磨削工艺对硬质合金切槽刀片刃口质量的影响

本文采用树脂结合剂金刚石砂轮磨削硬质合金切槽刀片的断屑槽和周边,形成刀片的切削刃口。采用D46和D64两种不同粒度的砂轮分别制备了5°、10°、15°前角的切槽刀片。在断屑槽的磨削过程中,采用了一次磨削和两次磨削两种方式。通过表面粗糙度仪测量了断屑槽和周边的粗糙度值,通过SEM测量了刀片的刃口缺陷。结果表明:砂轮粒度磨削周边对表面粗糙度的影响不大,断屑槽磨削的表面粗糙度受粒度影响较大;刀片前角越大,刃口完整性保持越差;相同条件下断屑槽采用两次磨削能获得更好的刃口质量。通过此试验,明确了生产现场磨削此类刀片的磨削工艺:磨削周边选用D64砂轮以提高加工效率,磨削断屑槽选用D46砂轮两刀磨削以提高表面质量,最终在兼顾磨削效率和质量的条件下可获得较好的刃口质量。     

PCD刀具断屑槽参数仿生群算法优化北大核心

为提高PCD刀具使用寿命和Ti6Al4V钛合金工件表面质量,改善断屑效果,建立直线圆弧形断屑槽PCD刀具车削仿真模型,通过响应面法研究断屑槽参数(前角α、棱带长度L、曲率半径R)对切削力、刀尖温度和工件表面残余应力的影响,建立切削性能随断屑槽参数变化的二次多项式回归模型,应用方差分析和显著性检验验证模型的准确性。根据线性加权法,构建以切削力、刀尖温度和残余应力为目标的多目标优化模型,通过仿生群算法进行断屑槽参数优化。实验结果表明,PCD刀具断屑槽最优参数为前角α=30°、棱带长度L=0.1 mm、曲率半径R=0.42 mm。优化断屑槽参数后的PCD刀具能够有效降低切削力、刀尖温度和工件表面残余应力,改善断屑性能,形成规则的螺卷屑或长紧卷屑。     

具有间断工作面的电镀磨刀砂轮

焊接硬质合金刀片的车刀在一般工厂中使用已很普遍了,但是它的刃磨还存在着不少问题。用绿色碳化硅砂轮磨削时效率低,磨屑多,操作条件差。由于砂轮比较容易磨损,刃磨刀具前面和断屑槽往往很困难。并且磨出的刀片刃口易产生裂缝和缺口,会影响刀具的切削性能和使用寿命。机夹不重磨刀具是近年来国内各工厂重点推广的先进刀具。对于这种刀具所用的刀片来说,虽然它的名称是“不重磨”,但通过实践证明对它进行重磨使用才是比较经济的。并且     

槽型几何参数对C型刀片切削45钢切削力和断屑性能的影响

45号钢是一种优质的碳素结构钢,因其具有良好的物理化学性能,成为了各行各业应用最广泛的工程材料之一。本文以调质45钢为工件材料,采用干式切削实验研究不同槽型几何参数对半精加工C型刀片切削调质45钢时的切削力和断屑性能的影响规律。结果显示:刀片的第一前角与反屑角都会影响切削力的大小,但第一前角的影响更为显著,适当地增加第一前角,有利于减少切削力,并求出不同切深下,切削力与第一前角的线性方程;刀片的断屑能力主要与反屑角的大小有关,适当地增大反屑角,有利于提高刀片的断屑性能;对于45号钢材料的半精加工,将刀片的第一前角控制在10°~15°,同时,本文获得了切削速度为200 m/s时,正常断屑范围的刀片反屑角与切深和进给率的量化关系,在不引起切削力显著增大的前提下,将反屑角提升至30°以上,可以获得良好的断屑性能。     

叉型叶根槽铣刀的重磨与检测探讨

大型汽轮机末级长叶根一般为七叉型叶根,为保证其严格的型线与尺寸精度要求,叶根槽铣刀一般要采用8片组合式正前角尖齿成型铣刀,但刀具用钝以后必须使用专用装置或设备修磨后刀面,由此带来了重磨和检测的难度。本文对叉型叶根槽铣刀的重磨与检测装置的原理、刃磨方法、检测手段进行了探讨。     

便于刃磨的曲面冲切模设计

介绍了一种便于刃磨的曲面冲切模 ,利用该模具结构可以改进某些传统的冲压工艺过程 ,并更好的保证某些成形零件的形状和尺寸精度     

可转位刀片复杂断屑槽断屑机理探讨

本文采用接触图形法和切屑折断性模糊估计等方法，对国外流行的可转位刀片复杂断屑槽的断屑机理进行了实验研究。研究结果表明：为了扩大断屑范围、改善断屑性能，这些断屑槽均采取了根据不同吃刀量和进给量改变有效槽宽，使切屑横截面弯曲、弹性挡屑、断屑槽形状、棱带宽度和刀尖圆弧半径的有机结合等措施。这些对于新型断屑槽型的开发具有重要意义。     

硬质合金微槽车刀切削刃近域热力强度分析

车刀前刀面切削刃近域作为金属切削过程高温高压的集中作用区域,其热力强度对刀具切削性能有重要影响。文章以前期工作所获得的切削过程刀屑接触界面平均切削温度和平均切削力作为热载荷和机械载荷,确定出刀屑接触区域范围,合理施加约束和边界条件。将稳态热分析和静力学结构分析相关联,对车刀进行热力耦合分析,根据在热载荷和机械载荷综合作用下主切刃近域的应力分布,对该微槽车刀切刃近域热力强度进行分析评价。研究结果表明,该硬质合金微槽车刀切削刃近域的最大等效应力小于刀具材料的许用强度,即该硬质合金微槽车刀在给定切削工况下进行切削时,刀具切削刃近域强度足够,不会因为强度问题影响切削过程的正常进行。     

硬质合金可转拉车刀片UG型断屑槽断屑机理的研究

本文采用接触图形法对硬质合金可转位车刀片ＵＧ型断屑槽的断屑机理进行了实验研究。结果表明：由于采用了根据不同切削深度和进给量巧妙改变有效槽宽、使切屑横截面弯曲呈拱形、弹形挡屑等措施，ＵＧ型断屑槽具有断屑范围较宽、在进给量较大时不易出现过分断屑等特点。此外，文中还对化学气相涂层刀片的ＵＧ型断屑槽在切削速度明显提高以后断屑范围的变化进行了研究。文中给出的ＵＧ型断屑槽的断屑范围图可供实际选用。     

不同冷却喷雾场下硬质涂层刀具切削蠕墨铸铁性能研究

研究在复合喷雾油膜附水滴冷却时,3种不同结构喷嘴的喷雾场及在硬质涂层刀具切削蠕墨铸铁过程中的切屑流向,并分析刀具和喷射位置对切削力的影响。研究表明:与普通圆柱型和扁平型喷嘴相比,尖嘴型喷嘴的雾化效果更佳,无大液滴现象,喷雾集中,连续雾化稳定。在硬质涂层刀具切削加工蠕墨铸铁过程中,当喷雾场只作用于刀具前刀面时,普通圆柱型喷嘴和尖嘴型喷嘴有良好的断屑作用;而尖嘴型喷嘴和扁平型喷嘴对切屑流具有更好的导向性。相对干切削和冷风辅助切削,尖嘴型喷嘴与外冷复合喷雾条件下切削蠕墨铸铁时,切削力可减小30～60 N,其中喷雾场喷射在刀具前刀面时的切削力最低。不同硬质涂层刀具需要与外冷复合喷雾的喷射位置相互匹配以达到最小的切削力。      

New cooling approach and tool life improvement in cryogenic machining of titanium alloy Ti-6Al-4V

Titanium alloy Ti-6Al-4V, a difficult-to-machine material because of its extremely short tool life, has been a major subject for cryogenic machining research. However, the approaches reported in past publications are inherently flawed. This study reviews how the temperature affects Ti-6Al-4V properties, and compares different cryogenic cooling strategies. Based on these findings, a new economical cryogenic cooling approach is proposed. Using a minimum amount of liquid nitrogen (LN2), this innovation features a specially designed micro-nozzle. Formed between the chip breaker and the tool rake face, the nozzle lifts the chip and injects focused LN2 into the chip–tool interface at the point of highest temperature. As the nitrogen evaporates, a nitrogen cushion formed by evaporating nitrogen lowers the coefficient of friction between the chip and the tool. An auxiliary mini-nozzle that sprays LN2 onto the flank at the cutting edge further reduces the cutting temperature. The study finds that the combination of these two micro-nozzles provides the most effective cooling while using the lowest LN2 flow rate. Improving the position of the nozzle/chip breaker further enhances the performance. Our cryogenic machining tests show that tool life increases up to five times the state-of the-art emulsion cooling, outperforming other machining approaches.     

In-situ measurement of rake face temperatures in orthogonal cutting

In machining, the thermal load significantly influences the tool wear and the workpiece quality, thus limiting the productivity. Therefore, a new experimental setup for the high-speed measurement of the rake face temperature in orthogonal cutting without substantially affecting the chip formation was developed. The investigations focus on the influence of different rake face preparation methods and cutting parameters on the temperature of the rake face, measured in the immediate vicinity of the cutting edge. The presented results significantly improve the understanding of the process and provide new insights for the tool development and the validation of cutting models.     

Analysis of the influence of tool type, coatings, and machinability on the thermal fields in orthogonal machining of AISI 4140 steels

Micro-thermal imaging was used to determine the amount of heat flowing into the tool, chip and workpiece during orthogonal cutting at speeds up to 400 m min⁻¹. Two AISI 4140 steels with different machinability ratings and three types of tools were compared: (i) uncoated with 0° rake angle, (ii) coated with −6° rake angle and (iii) coated with chip breaker. A control volume approach was used to estimate the energy partition from thermal images and energy outflow was compared to direct measurement of the cutting power. This provides a new physical tool for examining machinability, tool wear and subsurface damage.     

Influence of the direction and flow rate of the cutting fluid on tool life in turning process of AISI 1045 steel

High-pressure coolant (HPC) delivery is an emerging technology that delivers a high-pressure fluid to the tool and machined material. The high fluid pressure allows a better penetration of the fluid into the tool–workpiece and tool–chip contact regions, thus providing a better cooling effect and decreasing tool wear through lubrication of the contact areas.The main objective of this work is to understand how the tool wear mechanisms are influenced by fluid pressure, flow rate and direction of application in finish turning of AISI 1045 steel using coated carbide tools.The main finding was that when cutting fluid was applied to the tool rake face, the adhesion between chip and tool was very strong, causing the removal of tool particles and large crater wear when the adhered chip material was removed from the tool by the chip flow. When cutting fluid was not applied to the rake face, adhesion of chip material to the face did occur, but was not strong enough to remove tool particles as it moved across the face, and therefore crater wear did not increase.     

Performance of carbide tools with textured rake-face filled with solid lubricants in dry cutting processes

Surface texturing with different geometrical characteristics was made on the rake face of the WC/Co carbide tools, molybdenum disulfide (MoS₂) solid lubricants were filled into the textured rake-face. Dry cutting tests were carried out with these rake-face textured tools and a conventional tool. The effect of the texture shape on the cutting performance of these rake-face textured tools was investigated. Results show that the cutting forces, cutting temperature, and the friction coefficient at the tool-chip interface of the rake-face textured tools were significantly reduced compared with that of the conventional one. The rake-face textured tool with elliptical grooves on its rake face had the most improved cutting performance. Two mechanisms responsible were found, the first one is explained as the formation of a lubricating film with low shear strength at the tool-chip interface, which was released from the texturing and smeared on the rake face, and served as lubricating additive during dry cutting processes; the other one was explained by the reduced contact length at the tool-chip interface of the rake-face textured tools, which contributes to the decrease of the direct contact area between the chip and rake face.     

Characteristics of uncurled and reversely curled chip during orthogonal cutting

It has long been recognized that initially continuous chips are born curled. In this paper a new pattern of chip curl—reverse chip curl, named as chip down-curl, is observed during manufacturing of staggered integral high-finned tube using orthogonal planing with tools with flat rake face when rake angle is large enough and cutting thickness is small. With the increase of cutting thickness or decrease of rake angle, chips become uncurled and further increase of cutting thickness or decrease of rake angle leads to chip up-curl. The variations of chip curvature and conditions under which chips do not curl are obtained by experiments. The mechanisms of uncurled and reversely curled chip formation are investigated by analyzing microstructure of chip root. It is found that the uneven deformation that occurs on cross-section of chip results in reversely curled chip formation and no visible shear deformation that occurs on the primary shear zone of chip leads to uncurled chip formation.     

FEA modeling and simulation of shear localized chip formation in metal cutting

The finite element analysis (FEA) has been applied to model and simulate the chip formation and the shear localization phenomena in the metal cutting process. The updated Lagrangian formulation of plane strain condition is used in this study. A strain-hardening thermal-softening material model is used to simulate shear localized chip formation. Chip formation, shear banding, cutting forces, effects of tool rake angle on both shear angle and cutting forces, maximum shear stress and plastic strain fields, and distribution of effective stress on tool rake face are predicted by the finite element model. The initiation and extension of shear banding due to material's shear instability are also simulated. FEA was also used to predict and compare materials behaviors and chip formations of different workpiece materials in metal cutting. The predictions of the finite element analysis agreed well with the experimental measurements.     

An upper-bound cutting model for oblique cutting tools with a nose radius

The geometry of practical cutting tools is complex, and usually involves both non straight cutting edges and obliquity. It is of great practical importance to be able to predict cutting forces and chip flow directions for such tools. The authors demonstrate the use of a simplified geometry together with an upper bound model to predict the direction of chip flow. The model proposed includes a requirement for approximate force equilibrium as a method of estimating rake face contact area. A comparison of the results with those from earlier models and with experimental data is provided. Finally a proof of the Stabler chip flow hypothesis is given: it is shown that the hypothesis is only valid for the case of zero rake face friction.