高锰钢钻削用机夹式硬质合金刀具研究

为克服传统的焊接固定式钻头的不易更换、工艺性差的缺点,设计开发了机械夹持式的硬质合金钻削群钻。利用遗传算法给出了基于最大生产率的钻削参数优化结果,并进行新型机夹式刀具的钻削高锰钢的试验研究,得出了机夹式刀具的设计是可行的结论。同时,采用新型刀具加工,切削力和扭矩都相应的有所下降,其中轴向力下降了20%左右,扭矩下降了15%左右,切削效率也就得到了提高。     

基于新型改进钻尖的高锰钢钻削功率的实验研究

高锰钢在加工过程中,塑性变形大,加工硬化现象严重,因此钻削加工高锰钢一直是机械加工行业中的难点。在钻削高锰钢的过程中,会产生极大的切削力,会大大消耗机床的功率。通过对钻削加工用硬质合金钻头的几何参数进行改进,主要是对主切削刃前角、外缘转点以及横刃进行改进,达到降低钻削功率的目的,同时,利用多元线性回归理论,得出基于实验数据的多元回归钻削功率的数学模型,从理论上证明此次刀具改进的有效性。     

基于回归正交试验的皮质骨钻削力试验研究

骨钻过程中,钻削力的变化规律对优化刀具参数和测量骨损伤至关重要,为获得皮质骨的钻削力变化情况,采用正交试验方法对皮质骨进行钻削试验,并用多元线性回归法对试验结果进行处理,建立了皮质骨钻削力的预报模型。结果表明:对钻削力影响最大的是钻头直径d,进给量f次之,切削速度v的影响最小。在实际操作中选择合适的钻削参数可提高加工效率,通过控制切削用量可以获取最优的切削力。     

基于传递函数辨识的超声辅助微钻削轴向力动态模型

超声辅助微钻削过程中的动态钻削力严重影响刀具磨损以及微孔质量。通过建立动态钻削力模型,对超声辅助微钻削过程中的钻削力进行预测与控制,以达到提高刀具寿命以及微孔质量的目的。提出一种基于传递函数辨识的轴向力动态模型建立方法。在UAMD中,根据不同进给量时的钻削参数得到轴向力时间响应参数;通过系统辨识的方法对钻削系统进行建模,得到轴向力的原始传递函数模型;根据初步验证的结果和对传递函数频域的分析,采用多项式拟合的方法对模型的极点和增益进行修正;将优化后的数学模型转化为状态空间,得到超声辅助微钻削的轴向力动态响应模型。实验结果表明：优化后的动态模型与实验轴向力的时域响应吻合程度高。     

钎焊金刚石套料钻钻削CFRP的孔质量研究

采用钎焊金刚石套料钻进行了钻削碳纤维增强树脂基复合材料(CFRP)试验,使用测力仪与三维视频显微镜对钻削过程中的钻削力以及孔出、入口缺陷进行了测试与观察.实验结果表明:钎焊金刚石套料钻钻削CFRP时,相同转速下,钻削力随进给量的增大而增大;相同进给量下,钻削力随转速的增大而增大,且进给量对钻削力的影响大于转速的影响;已...     

GFRP低频轴向振动制孔的钻削力特性和套料钻磨损分析

GFRP的套孔钻削过程中极易产生分层、撕裂等加工损伤,其与轴向钻削力直接相关。为提高GFRP的制孔质量,采用新型金刚石薄壁套料钻,结合低频轴向振动加工技术,建立单颗磨粒的运动学模型和动力学模型,试验研究GFRP制孔中的轴向力变化规律,并对套料钻的烧焦概率、自动落料率进行分析。结果表明：对比常规钻削,低频振动钻削时的瞬时进给量和轴向力比常规钻削时的大,且随着振幅的增加,轴向力也随之增大;低频振动钻削和常规钻削时的轴向力皆随进给速度的增加而增大,随主轴转速的升高而降低。同时,低频振动钻削时磨粒间断性地参与钻削,大大降低了套料钻的烧焦概率,提高了其自动落料率,自动落料率高达88.24%,可实现GFRP的连续批量制孔。     

进给量对超声振动钻削力的影响研究

在振动钻削加工原理的基础上建立了振动钻削过程中平均钻削力的数学模型,在超声轴向振动钻削试验装置上进行了0Cr17Ni4Cu4Nb不锈钢的普通钻削和振动钻削的钻削力测量试验,通过试验分析了进给量对钻削力和钻头磨损的影响规律。试验结果表明,振动钻削过程中的钻削力明显减小,钻削力曲线更加平缓;振动钻削过程中,随着钻头进给量的增大钻削力逐渐增大,钻头磨损加剧。     

TC4钛合金钻削力和钻削温度仿真研究

为了提高TC4钛合金的可钻削性,采用有限元分析软件AdvantEdge建立TC4钛合金铣削加工有限元模型,分析工件和刀具上的温度分布规律,获得了钻削加工过程中钻削参数对钻削力和钻削温度的影响规律。结果表明：钻削TC4钛合金时最高温度出现在切屑上;钻削力随着主轴转速和进给量的增加而增大,随着钻头直径的增大而减小;钻削温度随着主轴转速、进给量和钻头直径的增加而增大。     

深小孔超声振动钻削轴向力的仿真与实验研究

建立深小孔轴向振动钻削加工仿真分析模型,针对轴向力通过DEFORM-3D有限元软件进行了超声振动钻削与普通钻削仿真,对两组仿真结果进行分析比较,并在超声轴向振动钻削装置上对不锈钢板进行了深小孔振动钻削和普通钻削实验,利用压电传感器测量了振动钻削和普通钻削加工的轴向力。实验结果与仿真结果对比表明:仿真结果与实验结果偏差低于8%,超声振动钻削的平均轴向力小于普通钻削的平均轴向力,钻削过程平稳。     

0Cr17Ni4Cu4Nb超声振动钻削的钻削力和切屑研究

针对深小孔钻削过程中存在轴向力和扭矩较大、断屑排屑效果差、刀具易磨损等问题,通过建立轴向振动钻削运动数学模型,分析了超声振动钻削的钻削力和断屑机制。在设计的超声轴向振动钻削试验装置上对0Cr17Ni4Cu4Nb不锈钢材料进行了普通钻削和超声振动钻削深小孔加工试验,对比分析了轴向力、扭矩和切屑形状。实验结果表明:与普通钻削相比,超声振动钻削降低了轴向力和扭矩,获得了良好的断屑和排屑效果,提高了钻削过程的稳定性,延长了刀具的使用寿命。     

Thrust force, torque, and tool wear in drilling the bulk metallic glass

The thrust force, torque, and tool wear in drilling of Zr-based bulk metallic glass (BMG) material are investigated. Drilling the BMG at high speed generates the chip light emission, high tool temperature, and severe tool wear. At low spindle speed, the BMG work-material builds up at the major and margin cutting edges and may break the drill. A range of feasible spindle speed and feed rate for the efficient drilling of BMG without the detrimental chip light emission and cutting edge work-material build-up has been identified in this study. Under the same drilling condition, the WC-Co tool generally requires less thrust force and about the same torque than the high-speed steel tool. The progressive wear of the major and margin cutting edges for BMG drilling is examined. Severe drill wear is associated with the bright BMG chip light emission. Without chip light emission, the drill wear is visible but not severe. This study concluded that precision holes in BMG could be generated with proper selection of tooling and process parameters.     

Response surface methodology-based approach to CNC drilling operations

Drilling operation is fundamental in the manufacturing industry to drill holes especially in sheet metal parts. This paper presents a mathematical model for correlating the interactions of some drilling control parameters such as speed, feed rate and drill diameter and their effects on some responses such as axial force and torque acting on the cutting tool during drilling by means of response surface methodology. For this exercise, a three-level full factorial design was chosen for experimentation using a PC-based computer numerically controlled drilling machine built in-house. The significance of the mathematical model developed was ascertained using Microsoft Excel^® regression analysis module. The results obtained show that the mathematical model is useful not only for predicting optimum process parameters for achieving the desired quality but for process optimization. Using the optimal combination of these parameters is useful in minimizing the axial force and torque of drilling operations; by extension, other drilling parameters such as cutting pressure, material removal rate, and power could be optimized since they depend on the combination of drilling parameters which affect the axial force and torque.     

The performance of hydrogenated and non-hydrogenated diamond-like carbon tool coatings during the dry drilling of 319 Al

Aluminium alloys, though widely used in the automotive industry, are difficult to machine, particularly by drilling and tapping without the use of metal removal fluids, because of aluminium's strong tendency to adhere to the cutting tool. Tribological tests have revealed that carbon-based tool coatings, such as diamond-like carbon (DLC), promise an improved performance due to their low friction and adhesion. However, the tribological performance of DLC coatings depends on both their hydrogen content and the testing environments. Hence the experimental approach taken in this study was designed to understand the cutting performance of hydrogenated DLC (H-DLC) and non-hydrogenated DLC (NH-DLC) tool coatings during the dry drilling of a 319 Al (Al–6%Si) alloy. An experimental drilling station was built to measure torque and thrust force changes using a cutting speed of 2500 rpm and a feed rate of 0.25 mm/rev. The cutting performance was assessed by measuring the torques and thrust forces generated during the drilling of the first 150 holes or by drill failure—depending on which occurred first. The results indicated that superior cutting performance was achieved, in both torque and thrust force responses, using DLC-coated drills rather than uncoated high-speed steel (HSS) drills. The uncoated HSS drills failed after drilling only 49 holes as a result of excessive aluminium adhesion. At least 150 holes could be drilled using the DLC-coated drills, and both the torque and thrust forces generated during drilling were lower than those with uncoated HSS drills. In addition, a smaller proportion of holes exhibited abrupt increases in torque (at the end of the drilling cycle) during drilling with the DLC-coated drills. Scanning electron microscopy (SEM) investigations showed that the H-DLC drill flutes displayed minimal aluminium clogging—resulting in lower torque. H-DLC coating also diminished metal transfer and buildup edge formation on the drill's flank face and cutting edge. Thus, torque and thrust force measurements, supported by metallographic data, indicated that H-DLC-coated drills provided better dry drilling performance than NH-DLC.     

Experimental studies of step drills and establishment of empirical equations for the drilling process

Various sizes of step drills were manufactured by a CNC grinder machine and used in the drilling process with different speeds and feed rates to produce single step holes in S1214 free machining steel. The performance of step drills was compared with that of conventional twist drills in the drilling of the free machining steel for the same task. The influences of drill size, feed rate and cutting speed on the performance of step drills were studied. Experimental results show that for better cutting performance, the small diameter should not be less than 60% of the large diameter. Also, most of the changes in the characteristics of the thrust force were influenced by the smaller drill of the step drill. On the other hand, the small diameter part of the step drill only contributed about 30% of the torque. From the experimental results, empirical equations for drilling thrust force and torque have been established for step drills.     

The effects of liquid-CO2 cooling,MQL and cutting parameters on drilling performance

An investigation is made into the effects of liquid carbon dioxide (LCO₂) cooling, minimum-quantity lubrication (MQL) and cutting speed in drilling. Experimental measurements of torque, thrust force and temperature are made over a wide range of process and operating conditions. The resulting empirical models are used to quantify the individual contributions of the controlled parameters on drilling performance, and to facilitate temperature-based process optimization. Of particular interest is the need to carefully adjust the LCO₂ flow rate for any combination of MQL flow rate and cutting speed. The optimization is validated both in simulation and actual drilling tests.     

An analytical finite element technique for predicting thrust force and torque in drilling

An analytical finite element technique was developed for predicting the thrust force and torque in drilling with twist drills. The approach was based on representing the cutting forces along the cutting lips as a series of oblique sections. Similarly, cutting in the chisel region was treated as orthogonal cutting with different cutting speeds depending on the radial location. For each section, an Eulerian finite element model was used to simulate the cutting forces. The section forces were combined to determine the overall thrust force and drilling torque. Good agreement between the predicted and measured forces and torques was found in orthogonal and oblique cutting and in drilling tests. The drilling tests were performed on AISI 1020 for several drill diameters, spindle speeds, and feed rates. An extension of the technique for predicting drill temperatures has also been described.     

Mechanistic modeling of bone-drilling process with experimental validation

In this paper, an improved mechanistic model is developed to predict the thrust force and torque for bone-drilling operation. The cutting action at the drill point is divided into three regions: the cutting lips, outer portion of the chisel edge (the secondary cutting edges), and inner portion of the chisel edge (the indentation zone). Models that account for the unique mechanics of the cutting process for each of the three regions are formulated. The models are calibrated to bovine cortical bone material using specific cutting pressure equations with modification to take advantage of the characteristics of the drill point geometry. The models are validated for the cutting lips, the chisel edge, and entire drill point for a wide range of spindle speed and feed rate. The predicted results agree well with experimental results. Only the predictions for the drilling torque on the chisel edge are lower than the experimental results under some drilling conditions. The model can assist in the selection of favorable drilling conditions and drill-bit geometries for bone-drilling operations.     

High-throughput drilling of titanium alloys

Experiments of high-throughput drilling of Ti–6Al–4V at 183 m/min cutting speed and 156 mm³/s material removal rate (MRR) using a 4 mm diameter WC–Co spiral point drill were conducted. The tool material and geometry and drilling process parameters, including cutting speed, feed, and fluid supply, were studied to evaluate the effect on drill life, thrust force, torque, energy, and burr formation. The tool wear mechanism, hole surface roughness, and chip light emission and morphology for high-throughput drilling were investigated. Supplying the cutting fluid via through-the-drill holes has proven to be a critical factor for drill life, which can be increased by 10 times compared to that of dry drilling at 183 m/min cutting speed and 0.051 mm/rev feed. Under the same MRR of 156 mm³/s with a doubled feed of 0.102 mm/rev (91 m/min cutting speed), over 200 holes can be drilled. The balance of cutting speed and feed is essential to achieve long drill life and good hole surface roughness. This study demonstrates that, using proper drilling process parameters, spiral point drill geometry, and fine-grained WC–Co tool material, the high-throughput drilling of Ti alloy is technically feasible.     

改性氧化铝陶瓷的微孔超声钻磨特性研究

本文研究了改性氧化铝陶瓷的微孔超声钻磨特性，与普通钻磨进行了比较研究，在不同的加工条件下对轴向平均切削力和扭矩进行了定量分析，并对陶瓷表面微结构进行了分析。得出普通钻磨时的轴向平均切削力和平均扭矩均远大于超声钻磨加工时的轴向平均切削力和平均扭矩；当机床主轴转速与发生器输入功率保持不变时，轴向切削力和平均扭矩随着进给量的增大而增大；当保持机床主轴转速不变且进给量比较接近时，在一定的输入功率范围内，轴向平均切削力和平均扭矩随着输入功率(相当于振幅)的增大而增大。超声加工下，磨针磨损较小；超声加工后的孔壁表面光滑。     

Mechanical model for predicting thrust and torque in vibration drilling fibre-reinforced composite materials

Delamination is a dramatic problem associated with drilling fibre-reinforced composite materials (FRCMs), which, in addition to reducing the structural integrity of the material, also results in poor assembly tolerance and has the potential for long-term performance deterioration. The key to solving the problem lies in reducing the thrust force of drilling. In this paper, a theoretical analysis for predicting mean values of thrust and torque in vibration drilling FRCMs is presented. The model is based on mechanics of vibration cutting analysis and the continuous distributions of thrust and torque along the lip and the chisel edge of a twist drill. The result of a simulation study has shown a very good agreement between the theoretical predictions and the experimental evidence. On the same cutting conditions, the thrust and the torque by the vibration drilling method are reduced by 20–30 percent, compared with conventional drilling.