CUTTING FORCES FOR HIGH-SPEED DRILLING OF COMPOSITES

The thrust and the torque of various carbide drills are studied for the high-speed drilling of fiber reinforced epoxy composites. The orthogonal experiment is carried out with different feed speeds at high rotation speed. Experimental results show that the spindle rotation speed is the most influential factor. The thrust andthe torque decrease under the condition of high rotation rate. With the decrease of the feed speed, the thrust and the torque decrease. But the effect of the feed speed is less than that of the spindle rotation rate. Moreover, the effect of drill materials on the thrust and the torque is more notable than that of the drill geometries and the feed speed. The thrust is greatly affected by the feed speed while the torque is obviously affected by drill geometries.

Computer Aided Design of Grinding Wheel for Drill Flute Production

Twist drill flute profile design is necessary in order to determine the required grinding wheel profile for a flute production. An accurate drill flute profile design is generated for two-flute conical twist drills using analytical equations to generate a drill flute profile design needed for the production of twist drills with straight lips. The required grinding wheel profile for a flute production was expressed in digitized form as well as in terms of two curve-fitted circular arcs. The drill flute profile geometry can never be precisely generated when required grinding wheel profile is represented by two circular arcs and the generated flute profile is just a very good approximation of the design flute profile. A CAD （computer aided design） software has been developed using MATLAB to determine the required grinding wheel profile for generating a given drill flute profile design.

Evaluation of the local inflammatory stress response and pain mediator secretion after impacted wisdom tooth extraction with high-speed turbine drill combined with original luxator

Objective: To study the local inflammatory stress response and pain mediator secretion after impacted wisdom tooth extraction with high-speed turbine drill combined with original luxator. Methods: Patients who received impacted wisdom tooth extraction in the First People's Hospital ofYunnan Province between March 2014 and June 2017 were selected as the research objects and randomly divided into the observation group who accepted impacted wisdom tooth extraction with high-speed turbine drill combined with original luxator and the control group who accepted impacted wisdom tooth extraction with traditional chisel. The contents of inflammatory mediators, stress mediators and pain mediators in gingival crevicular fluid were measured before surgery and 3 days after surgery. Results: Three days after surgery, PTX3, ICAM1, MPO, PGE2, PPARγ, ROS, MDA, 5-HT, CGRP, SP, Gal and ATP contents in gingival crevicular fluid of both groups were higher than those before surgery whereas GPx and T-AOC contents were significantly lower than those before surgery, and PTX3, ICAM1, MPO, PGE2, PPARγ, ROS, MDA, 5-HT, CGRP, SP, Gal and ATP contents in gingival crevicular fluid of observation group were lower than those of control group whereas GPx and T-AOC contents were significantly higher than those of control group. Conclusions: The impacted wisdom tooth extraction with high-speed turbine drill combined with original luxator can reduce the local inflammatory stress response and inhibit the secretion of pain mediators.

Determination of amphetamines,ketamine and their metabolites in hair with high-speed grinding and solid-phase microextraction followed by LC-MS

A novel hair sample pre-treatment method based on high-speed grinding and solid-phase microextraction(SPME)had been applied for the determination of amphetamines,ketamine and their metabolites in hair samples by liquid chromatography mass spectrometry(LC-MS).A 20mg sample of hair was ground with 2 mL of saturated sodium carbonate solution using a high-efficiency hair grinder with 70 Hz osillation for 2min at 4℃.After centrifuging,1.5mL of the supernatant was transferred and treated with SPME by direct immersion(DI-SPME).The target analytes extracted by fibre were desorbed and analysed using LC-MS.Under the optimum conditions,a recovery of 90.2%-95.8%was obtained for all analytes.The analytical method was linear for all analytes in the range from 0.2 to 10 ng/mg with the correlation coefficient ranging from 0.9985 to 0.9993.The detection limits for all analytes were estimated to be 0.067 ng/mg.The accuracy(mean relative error)was within±6.9%and the precision(relative standard error)was less than 6.8%.The combination of high-speed grinding of hair and SPME had the advantages of being easy to perform,environment-friendly and high in detection sensitivity.The proposed method offered an altermative ana lytical approach for the sensitive detection of drugs in hair samples for forensic purposes.

MATHEMATICAL MODEL AND CALCULATING METHOD OF PARAMETERS FOR TWIST DRILL HYPERBOL

Mathematical model for hyperboloid grinding of twist drill and relationships between drill design and grinding parameters are introduced.Point angles at outer corner and chisel edge corner are proposed to be used as the drill design parameters to determine the type uniquely and the relicf andgle is used as a supplement parameter.Function relations between the twist drill design and the grinding parameters are derived.Hence a theeoretical basis is estab-lised for design and grinding of the hyperboloid twist drill.

DESIGN AND CAD SYSTEM OF THE TOOL FOR DRILL FLUTE

Based on the principles of differential geometry and kinematics, a mathematical model is developed to describe the grinding wheel axial cross-section with the radial cross-section of the flute in a given drill under the basic engagement condition between the generating flute and the generated grinding wheel （or disk milling tool）. The mathematical model is good for the flute in the radial cross-section consisting of three arcs. Furthermore, a CAD system is also developed to represent the axial cross-section of the grinding wheel （or disk milling tool）. With the system, the grinding wheel （or disk milling tool） axial cross-section that corresponds to the three-arc flute cross section can be conveniently simulated. Through the grinding experiment of drill flutes, the method and the CAD system are proved to be feasible and reasonable.

Comparative investigation on high-speed grinding of TiCp/Ti–6Al–4V particulate reinforced titanium matrix composites with single-layer electroplated and brazed CBN wheels

In order to develop the high-efficiency and precision machining technique of TiCp/Ti - 6Al-4V particulate reinforced titanium matrix composites （PTMCs）, high-speed grinding experiments were conducted using the single-layer electroplated cubic boron nitride （CBN） wheel and brazed CBN wheel, respectively. The comparative grinding performance was studied in terms of grinding force, grinding temperature, grinding-induced surface features and defects. The results display that the grinding forces and grinding temperature obtained with the brazed CBN wheel are always lower than those with the electroplated CBN wheel. Though the voids and microcracks are the dominant grinding-induced surface defects, the brazed CBN wheel produces less surface defects compared to the electroplated wheel according to the statistical analysis results. The max mum materials removal rate with the brazed CBN wheel is much higher than that with the electroplated one. All above indicate that the single-layer brazed CBN super-abrasive wheel is more suitable for high-speed grinding of PTMCs than the electroplated counterpart.

机器人技术在复合材料修复中的应用

复合材料修复目前主要依赖于人工,存在效率低、准确度低、经验无法移植等问题,而机器人具有高自由度、高灵活性和操作标准化等特点。修复工艺与机器人技术相结合可以实现复合材料修复工艺的自动化,并大幅提高修复效率和标准化。目前,已有学者结合复合材料修复工艺的实际需求,开发了适用于钻孔、打磨、自动铺带和监测的末端执行器和机器人自动化修复系统,一定程度上解决了人工修复存在的精度低、修复质量不稳定等问题,为实现复合材料结构的高质量修复奠定技术基础。根据目前复合材料机器人修复技术的研究现状,深入介绍了复合材料修复中的机器人钻孔、机器人打磨、机器人自动铺带和机器人检测工艺的国内外研究现状及关键技术问题,分析了机器人技术在复合材料修复领域的应用,最后对复合材料机器人修复技术未来发展进行了展望。

高速机械粉磨对油基钻屑灰渣活性的影响

对油基钻屑灰渣进行了高速机械粉磨处理,研究了粉磨时间(0~7 min)对灰渣粒径分布和比表面积的影响,分析了掺灰渣胶砂试件的力学性能,并进行了XRD、SEM、FTIR微观分析。结果表明:与未粉磨处理的灰渣相比,粉磨3 min灰渣的粒径分布范围缩小至1.220~40.100μm,D50降低了60.9%,比表面积增大了27.6%;与其他粉磨时间的灰渣相比,用粉磨3 min的灰渣等质量取代30%水泥所制备的胶砂试件的28 d抗压强度最高,28 d抗折强度也较高;适宜的粉磨时间能够促进灰渣中的活性Si O2、Al2O3等与水泥水化产物Ca(OH)2发生二次水化反应,生成C-S-H凝胶和AFt,提高胶砂结构的密实度。

样本获取方法对混凝土中氯离子质量分数测定的影响

通过设计混凝土内掺氯离子的试验来消除不同深度处氯离子质量分数差异对测试结果的影响,分析了研磨法、钻孔法以及钻头直径对氯离子质量分数测定结果的影响,并基于假设检验和相对误差分析确定其在混凝土氯离子质量分数测定中的准确度。研究结果表明:虽然研磨法测定的氯离子质量分数结果较为稳定,但是与钻孔法的测定结果相比无显著性差异,为减少对既有结构造成损伤,推荐使用钻孔法进行取样;钻孔法钻头直径对氯离子质量分数测试结果影响很小,在满足相应置信度的推定区间要求下,6,10 mm钻孔直径下推荐的取样数量分别为23个和32个。

甘肃杨岭铁矿区复杂地层岩心钻探技术

甘肃杨岭铁矿区的铁矿体赋矿层位为蓟县系平头山组第四岩性段浅变质碎屑岩夹泥质大理岩岩层,地层上部完整、研磨性较强,下部破碎、漏失严重,且表现出较强的铁磁性。针对上述复杂地层导致的钻头寿命低、孔内事故频发、磁干扰严重等施工难题,通过采取优化钻孔结构、合理选择钻探设备、改进冲洗液使用工艺等措施,有效解决了上述问题,同时对加快施工进度、提高钻探效率、节约施工成本也起到了积极的促进作用。该钻探技术经验对其他强磁性矿区的钻孔施工具有一定的借鉴意义。

高速磨钻在侵袭性骨肿瘤治疗中的应用效果

目的:探讨高速磨钻在侵袭性骨肿瘤治疗中的应用效果。方法:选取2019年3月—2023年5月北京朝阳中西医结合急诊抢救医院收治的66例侵袭性骨肿瘤患者作为研究对象,根据随机数字表法分为研究组与常规组,各33例。常规组接受常规刮除术治疗,研究组采用高速磨钻刮除治疗。比较两组疾病复发情况、肿瘤转移情况、术后感染率、骨关节功能、骨愈合时间。结果:研究组疾病复发率、肿瘤转移率低于常规组,差异有统计学意义(P<0.05)。研究组术后总感染率低于常规组,差异有统计学意义(P=0.039)。术前,两组Lysholm评分比较,差异无统计学意义(P>0.05);术后1个月,两组Lysholm评分高于术前,且研究组高于对照组,差异有统计学意义(P<0.05)。研究组骨愈合时间短于常规组,差异有统计学意义(P<0.001)。结论:高速磨钻在侵袭性骨肿瘤治疗中的应用效果较好,能够降低疾病复发率、肿瘤转移率、术后感染率,改善骨关节功能,促进骨愈合。

某页岩气井连续油管震击器断裂案例分析

某页岩气井连续油管钻磨桥塞过程中发生一起震击器芯轴断裂事故,通过对工具断裂情况进行宏观分析,初步判断为弯扭断裂。结合震击器使用工况和受载特点,利用泵压数据进行傅里叶变换并得到泵压变化频谱,分析并认定是由于使用偏心磨鞋造成了泵压振动频率明显增大,泵压的高频波动增加了震击器芯轴的应力疲劳程度,最终造成了芯轴的断裂,并提出了改进建议。

反循环磨盘钻机成孔施工基坑内低净空灌注桩关键技术

灌注桩施工成孔常用的工艺方案有,旋挖机成孔、冲孔机成孔、人工挖孔等;但是,在基坑支护设计为内支撑、工程桩设计为灌注桩的项目施工中,考虑支撑结构影响,大型设备施工需要的净空不够,冲孔会产生震动,人工挖孔受安全问题制约,给灌注桩成孔工艺选择带来很大的难题。本文针对上述难题提出采用反循环磨盘钻机成孔的解决方案,为类似工程施工提供相应的措施方案。

小断面深竖井开挖技术

目前水利工程隧道优先规划深埋深隧洞,通风竖井同步加深,致使竖井开挖安全质量风险管控难度增大。相较与常规钻爆法施工,该文基于小断面竖井硬岩段的开挖,展开工艺操作要点、相关管控措施等技术研究,经过对比分析,采用水磨钻工艺确保进度受控前提下,安全风险更低、质量成型效果更佳,且操作简单。

单向C/E复合材料磨削制孔温度场模型的研究

碳纤维/树脂(Carbon/epoxy,C/E)复合材料制孔过程中,利用'以磨代钻'刀具的制孔质量较高,但由于树脂基体的热力学性能较差,温度场的分布对加工质量具有较大的影响。为研究磨削制孔过程中切削温度场的分布,在对材料热物理特性均匀化处理的基础上,利用有限差分法建立了三维制孔温度场模型,并利用试验对模型进行了试验验证。结果表明,利用所建模型计算所得加工过程中材料的温升情况、制孔出口温度的最大值以及出口温度场的分布均与实际情况具有较高的一致性,所建模型具有较高的精度及可信性。同时,出口温度场的分布呈椭圆形且椭圆的长轴与纤维方向一致。磨削制孔过程中温度场的研究,对确定磨削制孔过程中切削温度对加工缺陷的影响因素具有一定的指导作用,并为C/E复合材料'以磨代钻'制孔新工艺提供了理论依据。

C/E复合材料“以磨代钻”制孔工艺

为了提高C/E复合材料构件制孔加工质量,以C/E复合材料为研究对象,提出"以磨代钻"制孔新工艺,并研制了电镀金刚石刀具。与传统硬质合金刀具钻孔工艺进行对比试验,结果表明:金刚石刀具钻削轴向力降低30%-50%、刀具耐用度提高3-5倍、缺陷显著减少,更适合C/E复合材料钻孔加工。

基于数字钻进技术的岩石强度参数测定试验研究

快速准确地超前获取岩体力学参数是指导岩体工程安全施工的重要前提。利用自主研发的多功能数字钻进测试系统,进行了不同强度等级完整试样的室内数字钻进试验及单轴压缩试验研究。根据试验分析结果,基于岩石研磨钻进过程中金刚石钻头的受力特点,利用力学极限平衡与能量守恒原理,定义并推导出了岩石单位体积研磨能的理论解,获得了数字钻进参数与岩石单位体积研磨能的数学方程式,进而建立了岩石数字钻进参数与单轴抗压强度的定量关系,即RDP-Rc预测模型,并进一步验证了该模型的可行性与有效性。研究方法与结果可以为工程岩体强度参数的实时原位测定提供一种新的途径。

双曲面麻花钻数学模型及刃磨方法研究

提出了具有非直线刃的回转双曲面麻花钻数学模型的简化计算方法及钻头锋角合理定义点的选取 ,给出了双曲面钻型刃磨时其设计参数与刃磨参数的相互关系 ,并对此类二次回转曲面钻头提出了与传统的刃磨方法有根本区别的分层磨削插补成形的点磨削成形刃磨新方法。

一种新型螺旋面钻尖数学模型

利用面包络方法 ,建立了一种新型的螺旋面钻尖数学模型。该模型具有六个刃磨参数 ,综合了锥面刃磨方法和螺旋面刃磨方法的刃磨特点。为了与钻尖的四个结构参数 :半顶角、横刃余角、结构圆周后角和尾隙角 ,建立一一对应关系 ,从简化机床结构和控制的角度出发 ,两个刃磨参数被设定为常数。在此基础上 ,分析了刃磨参数对结构参数的影响。最后 ,分析了该刃磨方法对钻尖主刃和横刃形状的影响。