基于LabVIEW和单片机的切削温度数据采集系统

在切削加工过程中,切削温度是影响被加工工件的表面质量和刀具磨损的重要因素,因此对切削温度的研究有着重要意义.以人工热电偶为温度传感器,设计了热电偶的安装方法和以P87LPC768为核心,以串口为通讯方式的数据采集硬件电路,该电路对K型热电偶有冷端补偿功能.并利用LabVIEW提供的VISA接口,开发了用于实验室的切削温度实验数据采集的虚拟仪器,实现了对切削温度的在线测量和实时显示.     

切削SiCp/6005Al复合材料的PCD刀具磨损

为研究SiCp/6005Al切削时的刀具磨损机制及刀具磨损对切削力、切削温度、工件表面质量的影响，进行不同转速V和不同进给速度f下的切削试验，观察每组试验刀具切削后的磨损形貌，并通过监测动态切削力和切削温度来探究刀具的磨损机制。结果表明：工件转速提高使切削温度明显升高，但对切削力的影响很小；进给速度提高使切削力明显升高，而切削温度的变化范围较小。改变进给速度带来的力载荷变化是影响前刀面磨损的主要因素，改变工件转速带来的切削温度变化是影响后刀面磨损的主要因素。此外，刀具磨损是磨粒磨损、黏结磨损的综合作用结果，且刀具磨损会对切削力、切削温度和加工表面质量产生不利影响。     

钛合金铣削刀具的磨损对工件表面沿主轴方向粗糙度的影响

采用硬质合金立铣刀对Ti6Al4V进行高速铣削正交试验,将新刀具所加工的工件表面粗糙度和后刀面磨损至0.05 mm左右时的刀具所加工出来的工件表面粗糙度值进行对比分析,研究磨损后的刀具对工件表面粗糙度的影响。利用粗糙度仪对工件表面粗糙度进行测量,使用超景深显微镜对加工后的工件表面形貌以及刀具磨损情况进行观察,并利用测力仪测量铣削加工过程中刀具产生的铣削力。结果表明:当刀具后刀面磨损至0.05 mm时,其切削参数对工件表面的粗糙度影响大小与刀具崭新时的不一样,这是由于刀具的磨损导致在加工时刀具发生了振颤,从而影响到了工件沿机床主轴方向的粗糙度使其粗糙度增大。     

测量淬火冷却曲线几种热电偶的安装方法

为有效测量实际工件淬火冷却曲线,热电偶在工件上的安装必须满足温度响应快速,高稳定和牢固性等关键要求,为此设计了５种热电偶安装方法,应用高速测温系统测量了相应的冷却曲线,通过试验对比了不同安装方法的温度响应速度,重现性,牢固性,寿命和安装难易等特点。试验结果表明,将小直径的露端型铠装热电偶用钎焊法固定于小孔中的作法效果最好,为实际工件淬火冷却曲线测量提供了有效的方法。     

高速切削摩擦学研究

高速切削过程中的摩擦直接影响刀具失效(磨损和破损),刀具使用寿命、工件的加工精度以及已加工表面质量。文章综述了高速切削摩擦学研究进展,重点介绍了高速切削中刀-屑之间和刀-工之间的摩擦学特性,阐述了刀具前刀面与后刀面的磨损形态和磨损机理,以及高切削过程中的冷却/润滑条件和不同的切削环境对刀具和工件的影响。展望了高速切削摩擦学的发展方向。     

一种新型测温刀具的研制

采用磁控溅射法在PCBN刀具的前刀面上镀制NiCr和NiSi薄膜,形成一种新型的NiCr-NiSi薄膜热电偶测温刀具。详细阐述了薄膜热电偶的制作过程,结合WS-2005涂层附着力自动划痕仪和Jsm-5610扫描电子显微镜分别测试分析了NiCr和NiSi薄膜的附着力和成分。通过现场切削试验表明,制备的NiCr-NiSi薄膜热电偶测温刀具能够实时、快速、准确地测量切削温度。     

刀具材料与工件材料的元素扩散检测研究

高速切削加工已经成为切削加工的主流,但在高速切削加工时,刀具的扩散磨损加剧.由于在实际加工中很难对刀具的扩散磨损进行深入研究,文章采用刀具材料与工件的静态扩散实验装置,利用带能谱分析的扫描电子显微镜,对刀具材料(YG6)和钛合金工件(Ti-6Al-4V)的静态扩散试样进行了分析.分析表明,YG6和Ti-6Al-4V之间确实可以发生元素的相互扩散.分析的结果可以对切削加工过程中刀具的扩散磨损研究提供帮助.     

高速切削刀具系统的研究与试验分析

通过高速切削试验对切削刀具系统进行研究,特别是对刀具寿命和刀具动平衡的影响因素进行分析,得到切削速度、进给量等对刀具磨损的影响规律曲线以及基于切削用量的刀具耐用度数学预测模型,试验所得数据为高速切削加工切削用量的合理选择,特别是加工参数的优化问题提供了参考。     

铍铜合金断续切削后刀面磨损机理研究

目的研究断续切削过程温度变化对刀具粘结现象、涂层剥落和刀具磨损的影响。方法搭建了仿铣削加工的断续车削实验平台,采用热电偶法测量了断续切削过程中刀具后刀面在不同速度下的切削温度,利用带有能谱仪(EDS)的扫描电镜(SEM)观察后刀面随速度变化的磨损形貌并分析后刀面磨损区域的元素组成,阐述了后刀面温度和刀具磨损之间的联系,研究了Ti AlN涂层硬质合金刀具断续切削铍铜合金C17200时的后刀面磨损机理。结果随着切削速度的增加,刀具温度在v=500 m/min出现峰值,温度越高,后刀面的涂层剥落和粘结磨损现象越严重,涂层剥落和粘结磨损现象在切削速度为500 m/min时最严重,而后随着刀具温度的降低而减缓,切削速度600 m/min时的涂层剥落和粘结磨损现象相比500 m/min时有所减轻。结论断续切削过程中,刀具持续性地经受"负载-卸载"、"升温-降温"产生的高温、冲击和加工环境的不稳定性,是引起粘结现象、涂层剥落和刀具磨损的主要原因。涂层剥落和粘结磨损是导致铍铜合金断续切削刀具失效的主要磨损形式。     

模具高速切削数据库的研究与开发

采用结构化程序和规范化数据库技术开发了模具高速切削数据库系统，使用该系统可实现模具材料查询、刀具选择和切削用量查询。针对高速切削数据缺乏的问题，本系统采用了基于实例推理技术，实现为新工件材料、新刀具材料提供合理加工工艺和加工参数。     

Analytical modeling and experimental investigation of tool and workpiece temperatures for interrupted cutting 1045 steel by inverse heat conduction method

Cutting temperature is a key factor which directly affects tool wear, workpiece integrity, and machining precision in high speed machining process. The interrupted cutting process consists of several periodical characteristics, such as cutting force and time varying heat source. Induced cutting temperature models with time varying heat flux are developed in this paper to predict temperature distribution at tool inserts and workpiece during interrupted cutting process. A set of interrupted cutting experimental installation is designed to verify the proposed models. The comparison of predicted and measured results for 1045 steel in interrupted cutting processes shows reasonable agreement. The measured temperature of both the tool inserts and workpiece increase firstly and then decrease as the cutting speed increases. The peak temperature of the workpiece appears at 1500 m/min, while the peak tool inserts temperature appears at 1250 m/min approximately. Heat flux is calculated by the inverse heat conduction method. The applicability of Salomon's hypothesis to the temperature of tool inserts and workpiece is discussed during the interrupted cutting process. The dropped temperature at high cutting speed is mainly caused by that heat flux into tool inserts decreases and heat transfer time is not enough after the critical cutting speed.     

薄壁筒车削颤振稳定性预测

切削颤振是制约薄壁筒工件加工质量和效率的主要因素之一.采用半离散法对含有时滞项的动力学方程进行稳定性预测分析,结合薄壁筒工件切削振动试验,研究刀具、工件动力学参数匹配关系变化对切削加工稳定性的影响.通过仿真分析得出:随着刀具刚度或固有频率的提升,切削系统稳定性呈上升趋势,但过度提升刀具刚度并不会有效提升切削稳定性;在刀...     

Cooling approaches and cutting temperatures in cryogenic machining of Ti-6Al-4V

Cryogenic machining is an environmentally safe alternative to conventional emulsion cooling. In this study, liquid nitrogen (LN2) is applied to cutting Ti-6Al-4V, a difficult-to-machine but widely used material in aerospace industry. With the goal of identifying the cooling approach for most effectively and economically using cryogenic machining, this study evaluated cutting temperatures obtained under various cooling conditions. In addition to analyzing cooling approaches reported in previous cryogenic machining literatures (i.e., precooling the workpiece and conductive remote cooling), this paper introduces an innovative and economical dispensing method that directs LN2 through micro jets to the flank, the rake, or both near the cutting edge. The cutting temperatures were theoretically estimated by finite element method and the influence of cutting speed was analyzed. They were experimentally verified using the thermocouple imbedded at the carbide insert. Temperatures in cryogenic machining were compared with conventional dry cutting and emulsion cooling. Findings showed that a small amount of liquid nitrogen applied locally to the cutting edge is superior to emulsion cutting in lowering the cutting temperature. The study found that cooling approaches in order of effectiveness (worst to best) to be: dry cutting, cryogenic tool back cooling, emulsion cooling, precooling the workpiece, cryogenic flank cooling, cryogenic rake cooling, and simultaneous rake and flank cooling.     

Analysis of orthogonal finish machining using tungsten carbide and diamond tools of different heat transfer coefficients

An orthogonal cutting model for finish machining, using diamond and tungsten carbide tools which have different coeffficients of thermal conductivity, was simulated and analyzed. It was assumed that the tool had a minute amount of tool flank wear. The distribution of strain rate and stress within the machined workpiece and the determination of the cutting force were obtained after simulation. The generation and distribution of temperature and stress within the chip through cutting of the workpiece were also acquired. In addition, the temperature of the tool, the workpiece and the chip during finish machining by the two different tools, that show the effects of the different friction coefficients of the diamond tool and the tungsten carbide tool on cutting, were compared. Finally, the cutting forces predicted by the model for orthogonal finish machining were compared with those obtained by experiment, and it appears that the present orthogonal finish machining model is reasonable.     

The influence of tool flank wear on residual stresses induced by milling aluminum alloy

The machining processes could induce residual stresses that enhance or impair greatly the performance of the machined component. Machining residual stresses correlate very closely with the cutting parameters and the tool geometries. In this paper, the effect of the tool flank wear on residual stresses profiles in milling of aluminum alloy 7050-T7451 was investigated. In the experiments, the residual stresses on the surface of the workpiece and in-depth were measured by using X-ray diffraction technique in combination with electro-polishing technique. In order to correlate the residual stresses with the thermal and mechanical phenomena developed during milling, the orthogonal components of the cutting forces were measured using a Kistler 9257A type three-component piezoelectric dynamometer. The temperature field of the machined workpiece surface was obtained with the combination of infrared thermal imaging system and finite element method. The results show that the tool flank wear has a significant effect on residual stresses profiles, especially superficial residual stress. As the tool flank wear length increases, the residual stress on the machined surface shifts obviously to tensile range, the residual compressive stress beneath the machined surface increases and the thickness of the residual stresses layer also increases. The magnitude and distributions of the residual stresses are closely correlated with cutting forces and temperature field. The three orthogonal components of the peak cutting forces increase and the highest temperature of the machined workpiece surface also increases significantly with an increase in the flank wear. The results reveal that the thermal load plays a significant role in the formation of the superficial residual stress, while the dominative factor that affects thickness of residual stresses layer is the mechanical load in high-speed milling aluminum alloy using worn tool.     

整体硬质合金铣刀铣削热实验研究

本文通过建立一种整体硬质合金铣刀铣削热研究的实验方法,在相同的切削条件下,利用人工热电偶法和红外测温法对3种不同刃数的整体硬质合金铣刀的铣削温度进行了测量,并运用有限长移动线热源数学模型计算出不同刃数的铣刀在铣削过程中传入工件和切屑的热量值。研究结果表明:相同的切削条件下,刀刃数目越多,铣削温度越高,实验结果与实际加工一致。     

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 machining accuracy when dry turning via experiments and finite element simulations

Workpiece and tool are subjected to severe mechanical and thermal loads when turning. These loads cause thermal expansions and mechanically induced deflections of the tool and the workpiece. Such deformations induce deviations from the nominal workpiece geometry. In order to decrease these deviations, the cutting condition needs to be optimized prior to actual machining. In this paper, the accuracy of machining when dry turning aluminum is analyzed via experiments and finite element simulations. For this purpose, seven characteristic values were used: the forces, the deflection of the workpiece, the quantity of heat in the workpiece, the temperature distribution in the workpiece, the temperature of the tool, the temperature of the tool holder, and the actual dimension of the workpiece after turning. These experimentally determined results serve in addition as boundary conditions for a 3D finite element model of the workpiece, which calculates the deformations of the workpiece. The continuous removal of material affecting the temperature distribution in the workpiece is considered. The actual dimensions of the workpiece after turning revealed a remarkable influence of the cutting condition used on the accuracy of machining. Differences of up to 116 μm regarding the deviation from the nominal workpiece diameter of 30 mm were observed. The analysis of the machining accuracy reveals that particularly the use of both high cutting speeds and feeds enhances the accuracy of machining when dry turning aluminum.     

Thermoelectric signal characteristics and average interfacial temperatures in the machining of metals under geometrically defined conditions

The Herbert/Gottwein dynamic thermocouple method of temperature measurement was applied in order to experimentally evaluate the average interfacial temperatures arising in the external cylindrical turning of aluminium, brass, mild steel and stainless steel using high speed steel cutting tools. A detailed investigation of the EMF signal generated was undertaken for purposes of explanation of the DC and AC components which arise and of the influence of the cutting tool condition on the EMF signal generated. The thermoelectric characteristics of each material in conjunction with HSS were determined by means of the furnace method of calibration. A critical appraisal of each phase associated with the dynamic thermocouple method of cutting temperature measurement is undertaken in this paper and interfacial temperatures under a wide range of machine setting parameters for each workpiece material are presented and discussed.