SiC_p/Al复合材料薄壁圆弧板钻削变形研究

为了研究SiC_p/Al复合材料薄壁圆弧板钻孔时的变形特征及钻削参数对变形的影响规律。利用实验和仿真的方法对体积分数为56%的SiC_p/Al复合材料进行钻削研究,分析了钻削过程中工件的变形过程,研究了切削参数、工件约束方式、外径和壁厚对薄壁圆弧件的变形影响规律。结果表明:钻削过程中,工件的变形过程分为三个阶段,每个阶段有不同的变化特征;在其他条件一致的情况下,薄壁件的外径越大、壁厚越小、约束越少、进给量越大,则薄壁件的变形越大;切削速度对薄壁件的变形影响不大。     

钛合金Ti6Al4V与铝合金Al7075-T651钻削性能仿真对比分析

为了探究不同材料的钻削加工机理，对比分析了钛合金Ti6Al4V和铝合金Al7075-T651的钻削加工。通过有限元软件ABAQUS对钻削过程进行仿真研究，在有/无热力耦合工况下对工件应力应变、钻削力、摩擦力及能量等方面分析Ti6Al4V和Al7075-T651的差异。仿真结果表明，在非热力耦合模型中，铝合金出口处切屑以帽盖的形式去除，而钛合金则以C形切屑去除；在热力耦合的模型中，钛合金和铝合金的工件最大应力首先位于钻头横刃挤压处，随着钻头的深入，工件最大应力位于钻头主切削刃处；对比有/无热力耦合模型，发现钻削力受温度的影响最显著，其次为摩擦力，最后为塑性能，且铝合金比钛合金更容易受热软化效应的影响。     

钻尖结构对碳纤维复合材料制孔质量的影响

碳纤维复合材料在钻削加工中,容易产生毛刺、撕裂等缺陷。本文采用直径为6 mm的硬质合金钻头开展T300及T700碳纤维复合材料的钻削试验,研究钻头螺旋角、刃形和横刃结构对制孔质量的影响。研究结果表明:采用小进给量时,对孔出口质量影响程度最大的是刃型,而螺旋角和横刃的影响很小;采用大进给量时,对孔出口质量影响最大的是螺旋角,其次是刃型,横刃影响最小;直刃口钻头加工的孔出口质量明显优于凸刃口钻头;大螺旋角略优于小螺旋角;有无横刃的孔出口质量对比差异不显著。     

摩擦对高温合金复杂截面圆环多道次滚压成形不均匀变形作用

在高温合金复杂截面薄壁圆环多道次滚压成形过程中,板料要经历多场多因素偶合作用下复杂的不均匀塑性变形和组织演化历程,特别是不均匀塑性变形通常是导致薄壁件成形起皱、椭圆和开裂等缺陷产生的主要因素。摩擦是描述环件与辊轮接触作用的主要参数,很大程度上决定着该环件多道次滚压成形过程中塑性变形的不均匀性,严重的影响着其滚压成形质量。为此,本文以有限元仿真为主并结合实验和理论方法,对高温合金GH4169薄壁w形圆环多道次滚压成形进行了系统的分析;进而提出了不均匀变形度的表征方法,研究获得了摩擦对高温合金复杂截面薄壁圆环多道次滚压成形不均匀变形的影响规律。结果表明：随着滚压成形的进行等效应力极值逐渐增大,且从动辊进给时环件弯曲部分材料变形量较大;随着驱动、从动辊与环件之间摩擦系数的增加,不均匀变形程度先减小,后逐渐增大;导向辊与环件之间的摩擦对不均匀变形度的影响不大。     

夹层结构复合材料钻削试验研究

选用φ12mm高速钢麻花钻,在干切削条件下对夹层结构复合材料进行单因素钻削试验,研究钻削参数的变化对钻削轴向力的影响规律以及出口垫板对分层的影响;选用聚晶金刚石钻头,通过与高速钢麻花钻比较,研究横刃对轴向力以及分层的影响。结果表明:小进给量情况下,选择横刃小的钻头进行钻削,可以提高孔出口的加工质量。     

GH4169高温合金轴向超声振动钻削加工实验研究

针对GH4169高温合金材料钻削加工困难、表面质量和加工精度要求高等难题,基于在普通车床上实现超声振动钻削加工的思想,设计了一套轴向超声振动钻削加工系统。利用该系统对GH4169高温合金材料做了轴向超声振动钻削与普通钻削的对比实验。结果表明:在不同的转速和振幅下,轴向超声振动钻削相对于同一实验条件下的普通钻削,可明显提高孔的加工质量,且在切屑形态和孔表面形貌等方面均有较大改善。     

用整体硬质合金钻头加工深孔

越来越多的加工车间正用整体硬质合金钻头取代枪钻加工深孔。 在过去枪钻占主导地位的深孔加工刀具市场中,能钻削深度达16—40倍孔径深孔的新一代整体硬质合金麻花钻正占有越来越大的份额。为了提高加工精度和排屑性能,这种整体硬质合金钻头采用了横刃和螺旋槽,并采用高密度硬质合金材料以提高硬度,从而使其能以比枪钻快5—10倍的速度进行钻削加工。     

GH783/GH4169环件异种金属焊接热-力过程的有限元分析

针对低膨胀高温合金GH783与普通GH4169合金的环件异种金属氩弧焊,建立了热-力过程有限元数值分析模型.通过模拟揭示了GH783/GH4169异种金属焊接过程的应力-应变演变特点,预测了环件焊后的残余应力和变形分布.结果表明,合金的线膨胀系数差异造成了焊接应力-应变的非对称分布,线膨胀系数大的GH4169侧的焊接应变、应力以及最终的焊接变形均大于低膨胀GH783合金侧.模拟预测的环件轴向收缩量与实测结果吻合.     

单晶Cu材料纳米切削特性的分子动力学模拟

建立了单晶Cu纳米切削的三维分子动力学模型,研究了不同切削厚度下纳米切削过程中工件缺陷结构和应力分布的规律.纳米切削过程中,在刀具的前方和下方形成变形区并伴随缺陷的产生,缺陷以堆垛层错和部分位错为主.在纳米尺度下,工件存在很大的表面应力,随着切削的进行,工件变形区主要受压应力作用,已加工表面主要受拉应力作用.随着位错在晶体中产生、繁殖及相互作用,工件先后经过弹性变形——塑性变形——加工硬化——完全屈服4个变形阶段,随后进入新的循环变形.结果表明:工件应力-位移曲线呈周期性变化;切削厚度较小时,工件内部没有明显的层错产生,随着切削厚度的增大,工件表面和亚表层缺陷增加;切削厚度越大,对应应力分量值越小.     

多场耦合作用下GH4169合金变形行为与强韧化机制

研究了脉冲电流/温度/应力多场耦合作用下,镍基GH4169合金的变形行为与强韧化机理。结果表明,GH4169合金在脉冲电流/温度/应力作用下,GH4169合金变形抗力降低、塑性变形能力提高,在高温下脉冲电流的引入加剧了原子热振动、金属晶格Pereils力下降,由此降低了合金变形抗力,增强了合金塑性变形协调能力。而当GH4169合金经脉冲电流/温度场耦合时效处理,则可以显著提高合金的高温强度和韧性,脉冲电流/温度耦合作用提高了合金基体空位缺陷密度,促进了其在随后高温变形过程中析出大量数纳米级新γ"相强化相,而脉冲电流/温度场耦合时效处理过程中析出、粗化的γ"相以及其与合金高温变形中新析出数纳米级γ"相的协同作用,使合金实现了强韧化。     

Drilling of carbon composites using a one shot drill bit. Part I: Five stage representation of drilling and factors affecting maximum force and torque

The thrust force and torque produced during drilling contain important information related to the quality of the hole and the wear of the drill bit [1]. In this paper, the force and torque produced during drilling of carbon fibre using a ‘one shot’ drill bit is investigated. The signals in the time domain were divided into stages and common problems and defects associated with each stage discussed. It is also shown how tool wear and thickness of the workpiece affect the thrust force and torque throughout the drilling process. The findings of this paper are used to develop a mathematical model of the maximum thrust force and torque as described on Part II of this paper and are a valuable reference for future optimisation of drilling carbon composites with a ‘oneshot’ drill bit.     

Wear characteristics of the cemented carbide blades in drilling limestone with water jet

Drilling hard rock with water jet is considered to be an efficient way to improve the work life of the cemented carbide blade. In this paper, cemented carbide material YG-6 is used on the drill bit in limestone drilling with water jet. Wear characteristics of the cemented carbide blades in drilling limestone with water jet is studied. Experiment results showed that the water jet pressure and nozzle diameter played an important influence on the wear rates of the cemented carbide blades in the drill bits. The wear rates of YG-6 blades decreased when the jet pressure increased. But the decline speed of wear rates was not even, it declined more and more slowly when the jet pressure upon 10 MPa. It was also showed that wear rates decrease with the increase of the nozzle diameter in the drill bit, for the bigger nozzle diameter could provide more impact force which could reduce the mechanical force on the YG-6 blades. SEM photographs were taken to characterize the wear mechanism of the cemented carbide blades in limestone drilling with water jet. Surface analysis demonstrated that cemented carbide blades in limestone drilling with water jet showed circular action of brittle fracture, grain pullout and polishing, which induced material removal process.     

TC4钛合金深孔钻削方式和轴向力研究

针对钛合金钻削过程中的轴线偏斜问题,基于Abaqus对钛合金两种不同的钻削过程进行仿真,建立钻杆的有限元模型、数学模型,并将轴线的偏斜问题转化为两种不同钻削方式的轴向力大小问题。得出结论：在工件速度为180～900 r/min时,钻头与工件同时反向旋转时,轴向力随着工件速度的增大而减小。并对该方式进行工件转速为900 r/min的不同钻头转速、进给量的16组试验,结果表明：在钻头转速为900～1 800 r/min之间、进给量为0.02～0.08 mm/r时,平均轴向力减小了33.4%。因此,可以采用该钻削方式减小偏斜量。     

基于枪钻的薄壁深孔加工工艺设计

在分析热交换板的深孔特点和枪钻加工工艺的基础上,提出了通过减小刀具径向切削力、增加导向条长度和增大薄壁处强度来改善薄壁深孔加工中孔轴线偏斜问题的加工方法,依此设计了4种枪钻加工工艺方法,并通过试验进行了对比,获得了理想的加工效果。     

小孔导电加热钻削钻头后刀面磨损及孔表面质量研究

难加工材料的小孔钻削加工严重地磨损钻头的后刀面,而后刀面的磨损是麻花钻磨损的主要形式。针对难加工材料不锈钢板采用导电加热钻削小孔进行试验,定量地分析了进给量、加热电流以及切削速度等参数与麻花钻后刀面磨损程度之间的关系,并研究了该磨损量对孔壁表面粗糙度的影响趋势。     

Drilling of carbon composites using a one shot drill bit. Part II: empirical modeling of maximum thrust force

In order to extend tool life and improve quality of hole drilling in carbon composite materials, a better understanding of ‘one shot’ hole drilling is required. This paper describes the development of an empirical model of the maximum thrust force and torque produced during drilling of carbon fiber with a ‘one shot’ drill bit. Shaw's simplified equations are adapted in order to accommodate for tool wear and used to predict maximum thrust force and torque in the drilling of carbon composite with a ‘one shot’ drill bit. The mathematical model is dependent on the number of holes drilled previously, the geometry of the drill bit, the feed used and the thickness of the workpiece. The model presented here is verified by extensive experimental data.     

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。     

基于回归正交试验的浅孔钻钻削的有限元仿真

基于回归正交试验法设计钻削模拟方案,利用最小二乘法原理得到钻削力的经验公式;基于有限元软件Deform3D平台,建立了用浅孔钻钻削加工45钢的有限元模型,动态模拟浅孔钻钻削过程,获得了浅孔钻钻削加工过程中工件的等效应力和温度,分析预测了加工过程中硬质合金刀具所受的主切削力、径向力以及两刀片所受的扭矩,并评估刀片的磨损情况。     

Friction drilling of austenitic stainless steel by uncoated and PVD AlCrN- and TiAlN-coated tungsten carbide tools

Friction drilling utilizes the heat generated from the friction between the tool and the thin workpiece to form a bush for fixtures such as screw threads in plastic deformation process. This process produces no chip, shortens the time required for hole-making and incurs less tool wear, thus lengthening the service life of the drill. In this study, tungsten carbide drills with and without coating were employed to make holes in AISI 304 stainless steel, which is known to have high ductility, low thermal conductivity and great hardness. TiAIN and AlCrN were coated onto the drill surface by physical vapor deposition (PVD). Performance of coated and uncoated cutting tools was examined for drillings made under different spindle speeds. Changes in relationship between drill surface temperature, tool wear and axial thrust force during machining were also explored. Experimental results reveal that lubricating effect of the coating and low thermal conductivity of AlCrN caused AlCrN-coated drill to produce the highest surface temperature but the lowest axial thrust force with the least tool wear. However, the difference in performance between coated and uncoated drills diminished with increase in number of holes drilled.