金刚石孕镶钻头的面形状

本文对金刚石孕镶钻头磨损机理进行了分析。讨论了目前钻探领域广泛使用的几种典型的金刚石孕镶钻头唇面形状的优缺点。最后从理论的角度改进了金刚石钻头的唇面形状。并阐述了制造该形状钻头的方法及该钻头的优越性。     

金刚石孕镶钻头的唇面形状

本文对金刚石孕锒钻头磨损机理进行了分析。讨论了目前钻探领域广泛使用的几种典型的金刚石孕锒钻头唇面形状的优缺点。最后从理论的角度改进了金刚石钻头的唇面形状。并阐述了制造该形状钻头的方法及该钻头的优越性。     

圆杯——多边形杆复合挤压的上限研究

此文采用三次多项式表示的流线速度场和基元圆环技术相结合的混合流动模型对圆杯－多边形截面杆型复合挤压进行了上限分析，得到挤压力的上限解，分析了杆部截面形状对复合挤压分流点位置及变形力的影响规律并对理论计算进行了实验验证。     

PDC钻头磨损过程中的应力分析

为了更加准确地计算PDC钻头在钻进过程中所受的力,需要模拟钻头使用一段时间后的磨损情况.运用空间几何和数值计算理论,对PDC钻头的结构和受力重新进行分析.描述了PDC钻头在不同磨损情况下应力改变情况,推导出了PDC钻头磨损时受力方程.综合考虑了钻头冠部形状、切削齿的布置、切削齿的工作角、切削齿的形状及尺寸、切削齿的相互作用的影响,提出了磨损过程中切削齿的切削面积、切削体积、切削弧弧长等切削参数与磨损程度的关系的数值计算方法,为精确估算PDC钻头的工作时间提供了一种更为科学的手段.     

沟球环件冷辗扩过程中截面变化规律

在沟球环件冷辗扩过程中,环件外径的增长预测和导向辊的位置确定是确保平稳辗扩的条件之一,而这两者的决定因素在于辗扩过程中截面形状变化。采用商业软件ABAQUS/Explicit对冷辗扩过程进行三维建模,预测沟球截面环件的直径增长和截面形状变化过程。在D56G90型冷辗环机上进行实验,测量了不同阶段的环件直径和沟球截面形状。将实验测量结果分别与解析计算结果和有限元计算结果进行比较,得出三者之间的差别,从而发现误差。利用解析结果和实验结果来修正三维有限元模型,以便更加精确地利用有限元模型来预测环件直径的增长规律和截面变化规律。模拟结果可以用于指导环件冷辗扩的工艺制定和生产,以期提高环件的质量。     

基于离散单元法(DEM)研究镀桶截面形状对机械镀过程物料运动的影响EI北大核心CSCD

镀桶的截面形状对机械镀过程的影响受限于机械镀设备等原因,相关研究较少。为研究不同截面形状的镀桶对机械镀过程中桶内物料运动规律的影响,采用离散元模拟软件EDEM建立不同形状(四边形、六边形、八边形、圆形)下镀桶内物料的运动模型,并从碰撞区域、碰撞频率、碰撞接触力和碰撞能量四个方面对桶内物料间的碰撞情况进行研究。结果表明:镀桶的截面形状对机械镀过程中桶内物料的碰撞和运动规律产生很大影响,在相同模拟条件下,八边形镀桶内物料运动的惰性区域最小;通过对不同形状镀桶内物料间碰撞频率、碰撞接触力和碰撞能量的对比分析,八边形镀桶中的物料运动规律最有利于机械镀工艺过程中镀层的形成和增厚,八边形为最优镀桶截面形状。另外,通过计算机数值模拟的方法探讨镀桶截面形状对机械镀过程中物料运动规律的影响规律,为机械镀设备发展和工艺优化提供理论依据。     

汽车覆盖件冲压方向的优化

本文分析了冲压方向在汽车覆盖件工艺设计中的作用，总结了影响冲压方向选择的诸多因素，通过将空间问题转化为平面问题，导出了以评价函数法为基础的冲压方向优化模型。该模型对拉延件截面形状进行分析，以冲压过程中不得存在死角为约束条件计算单截面的可行域，由此推出了轴向转角的公共可行域，并建立了一组目标函数做为优化对象。利用遍历法在截面转角的公共可行域内进行搜索，求出各个截面的最优值，最后加权平均便可得到目标函数值。文中给出了程序框图和计算实例。     

不同唇面形状金刚石钻头对钻进效率的影响

针对金刚石钻进中钻头唇面形状的选形问题,从岩石破碎机理入手,分析了岩石在不同形状压头作用下的破碎过程。对平底型、高低交错型及同心圆尖齿型三种不同唇面形状钻头进行现场实验比较,得出同心圆尖齿型的综合效果最好的结论。在实际钻探生产中,可依此选择相应形状的底唇面钻头来提高钻进效率。     

低速大扭矩水压马达配流副仿生凹坑形非光滑表面流场分析

通过在低速大扭矩水压马达配流盘上设计了不同凹坑形仿生非光滑表面,并建立配流副的全水动压润滑模型,采用CFD方法研究了凹坑的不同开口形状和截面形状对内部液体流动的影响及其对流体动压润滑性能的影响规律。结果表明:在凹坑截面形状、开口尺寸及凹坑深度相同的情况下,开口形状为圆形的凹坑形仿生非光滑表面的液膜表面压力分布情况要略好于开口形状为正方形和三角形的凹坑形仿生非光滑表面的液膜表面压力分布情况;凹坑开口形状都为圆形时,截面形状为半圆形的半球坑与截面形状为矩形的圆形柱坑、截面形状为三角形的圆形锥坑相比,其液膜表面压力分布情况较好,液膜表面承载力略大,流体动压润滑性能较好。     

涂层硬质合金内冷式高效深孔钻

日本OSG公司开发的FTOGKXC涂层硬质合金内冷式深孔钻能在加工中心上实现深孔的高效加工。其结构特点为：带内冷却液孔，能确保钻头在充分冷却润滑条件下工作；钻尖形状断屑性能良好，钻沟截面形状排屑顺畅，有助于提高加工效率和加工质量。钻头基体材质采用强度、韧性和硬度兼优的超细颗粒硬质合金，基体表面涂覆耐热性、     

Simulation-based twist drill design and geometry optimization

Designing a high-performance twist drill is difficult due to the complex relationship between drill geometry and numerous and conflicting design goals. Earlier approaches of computer-aided twist drill design are limited to only few design aspects. This article presents a new holistic method of using computing power for twist drill design and optimization. A complete drill geometry model is used to obtain drill performance characteristics and to ensure functional capability. Numerical simulation models calculate structural stiffness and strength, torque and thrust force, coolant flow resistance, chip evacuation capability and chip flute grindability. A multi-objective geometry optimization is realized by implementing metaheuristic optimization algorithms. As a result, a numerical overall optimization of twist drill performance is possible.     

Some aspects of twist drill design

A mathematical approach to the flute disposal capacity based on the diameter of the circle which could be inscribed in the flute space is presented. It is important to know what order of drill rigidity is required for good performance when drilling various work materials. The main features of the cross-section profile which could affect the stiffness of a twist drill are the cross-sectional area and the second moment of area. The relationship between the various drill parameters and these features is one aspect to be investigated in this paper. Empirical equations based on the results obtained from this investigation are presented.     

Comprehensive analysis of delamination in drilling of composite materials with various drill bits

Beside the twist drill, the effects of various drill geometries were rarely discussed in analytical fashion. This study presents a comprehensive analysis of delamination in use of various drill types, such as saw drill, candle stick drill, core drill and step drill. In this analysis, the critical thrust force at the onset of delamination is predicted and compared with the twist drill.     

加工不同材料时高速钢麻花钻的刃磨

高速钢麻花钻在加工不同材料时，客观上具有不同的加工条件，并且对钻头产生不同的影响，本文对此提出了在加工不同材料时，对钻尖部分要进行不同的刃磨，以提高钻头使用性能及孔加工质量；同时，从实用的角度提出其它一些方法和措施以保证钻头真正发挥其应有的效能。     

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.     

麻花钻几何参数对不锈钢钻削性能影响的研究

采用ProE和Deform-3D软件分析了影响麻花钻钻411性能关健的几何参数,主要研究麻花钻横刃和顶角对不锈钢钻削过程中切削力、扭矩、刀具磨损的影响.介绍了缩短横刃长度和采用S形横刃螺旋面钻尖对不锈钢钻削力和扭矩的影响.重点分析了顶角影响主切削刃的长度、单位刃长的切削负荷、切削层中切削宽度与切削厚度的比例、切削中轴向力与扭矩、切屑形成与排屑情况.对于在钻削中,如何提高钻头的寿命,提高钻削加工的生产率和孔的加工质量具有重要的指导意义.     

管状扭力梁液压成形有限元仿真分析及试验

相比板状扭力梁,采用液压成形工艺加工管状扭力梁能够减轻零件重量,提升零件强度、刚度和疲劳性能。分析了管状扭力梁零件的典型截面形状,指出了零件加工难点和成形过程中的主要缺陷。利用有限元仿真分析方法对管状扭力梁成形过程进行数值模拟,分析了成形过程中典型截面的壁厚变化规律,即过渡区域壁厚变化较大,中间区域壁厚变化不明显。在此基础上进行工艺试验。研究结果表明,管状扭力梁液压成形有限元仿真结果与试验结果吻合性好,零件的实际形状与理论设计形状基本一致。     

Tool condition monitoring in drilling using vibration signature analysis

This paper presents a study on monitoring tool wear and failure in drilling using vibration signature analysis techniques. Discriminant features, which are sensitive to drill wear and breakage, were developed in both time and frequency domains. These features were found to be relatively insensitive to cutting conditions, and sensor location. In the time domain, a monitoring feature based on calculating the kurtosis value of both the transverse and thrust vibrations, was found to be rather effective for on-line detection of drill breakage. On the other hand, in the frequency domain, a cepstrum ratio, derived from the spectra of the vibrations monitored in both directions, was also found effective in detecting breakage events. The effect of different types of wear on the vibration power spectra, in both the transverse and the thrust directions, was also investigated. A signature feature, namely the instantaneous ratio of the absolute mean value (RAMV_i), was developed in this study and used as a threshold for controlled capture of the vibration signal. The ability of the monitoring features to detect drill wear and breakage was verified experimentally. The drilling tests were performed using 3 and 6 mm diameter high speed steel twist drills, and cast iron workpieces. The results confirmed the effectiveness and robustness of the proposed monitoring features.     

Performance evaluation of endrills

This paper evaluates the performance of a relatively new type of drill called an endrill which is a cross between a drill and an endmill. Investigations into the effects of its cutting conditions on the drilling forces, surface finish, drill wear and hole oversize were carried out. It was found that endrills produced better quality holes than conventional twist drills, better surface finish and less oversize of the holes. Hence, with proper feed, speed and flow rate of the pressurized flushing coolant, a good finish of about R_a = 1 μm can be attained without reaming. Thus, the productivity of finished holes can be remarkably improved. Compared to twist drills, lower torque and thrust were observed which yielded improved tool life and reduced power consumption. No “walking phenomenon” was observed when this kind of drill was used and the amount of hole oversize was found to average about 0.7% of the drill diameter as compared to 1.6% when twist drills were used. Finally, general equations for the drill torque and thrust were derived from the experimental results.     

A new methodology for designing a curve-edged twist drill with an arbitrarily given distribution of the cutting angles along the tool cutting edge

The present study aims at the development of a new methodology for designing a curve-edged twist drill with an arbitrarily given distribution of the cutting angles along the tool cutting edge. The new methodology consists of 81 major mathematical equations and is developed using a method of mapping relevant planes and straight lines of a cutting tool (such as the cutting plane and the cutting edge) as corresponding image points and image lines on a projection plane. The developed methodology is used to intuitively and graphically analyze and determine the relationship between the orientation of the cutting edge and the cutting angles at each point on the cutting edge. A set of image points and image lines is established to calculate the cutting angles on the cutting edge of a twist drill, including the working tool rake angle, the working tool inclination angle, the working cutting edge angle, and the working normal rake angle. Three computer case studies are provided to show curved cutting edges that correspond, respectively, to a linear distribution of the working tool rake angle, a combined linear and uniform distribution of the working tool rake angle, and a linear distribution of the working tool inclination angle along the tool cutting edge. Finally, a set of metal drilling experiments is performed to compare the drilling torque and the thrust force between a conventional straight-edged twist drill and a new curve-edged twist drill that has a combined linear and uniform distribution of the working tool rake angle along the tool cutting edge. The experimental results show that the new curve-edged drill reduces the drilling torque by 28.5% and the thrust force by 24.6% on average.