电镀金刚石钻头钻削碳纤维复合材料研究

碳纤维复合材料钻孔加工时极易产生分层、毛刺、撕裂等缺陷,是典型的难加工材料。针对碳纤维复合材料特点,以电镀金刚石钻头为研究对象,从钻削轴向力、钻孔出口质量等方面分析电镀金刚石钻头钻孔特点,并与硬质合金麻花钻进行对比,得出结论：电镀金刚石钻头钻削碳纤维复合材料时钻削轴向力较小,钻削质量较好,更适合于碳纤维复合材料的加工;钻头转速提高有利于减小钻孔缺陷的产生,钻削轴向力随钻头转速的升高而降低,随钻头直径的增大而增大;最后,通过多元线形回归方法得出电镀金刚石钻头钻削力经验公式。     

制孔分层损伤对CF/PEEK复合材料拉伸性能和表面应变分布的影响

目的 研究钻削制孔表面分层损伤与拉伸载荷下开孔碳纤维增强聚醚醚酮（CF/PEEK）复合材料表面应变分布的相关性。方法 通过对CF/PEEK复合材料层合板进行钻削制孔实验,分析不同进给速度对钻削温度、钻削轴向力、制孔出口表面分层和孔壁表面损伤的影响。采用数字图像相关技术（DIC）和力学实验相结合的方法,研究分层损伤程度对开孔CF/PEEK复合材料层合板拉伸性能和表面应变分布的影响。使用扫描电镜观测开孔试件的断裂形貌,分析开孔试件受拉伸载荷时的破坏模式。结果 随着进给速度的增加,钻削温度降低,钻削轴向力提高,出口表面分层和孔壁损伤程度加剧。随着分层损伤程度的增加,层合板的拉伸强度呈现出降低的趋势,试件的拉伸强度从558.4 MPa降低到525.63 MPa,降低了5.87%。在中应力和高应力状态下,试件x方向的最大负应变随着分层损伤程度的增加而增加。在高应力状态下,试件y方向的最大正应变随着分层损伤程度的增加而增加。试件的断裂方式主要是基体开裂、分层和纤维撕裂,断口有纤维脱落和纤维拔出,垂直于载荷方向的纤维破坏模式为剥离破坏,与载荷方向一致的纤维破坏模式为拉伸破坏。结论 钻削制孔表面分层损...     

钻削参数对碳纤维复合材料孔加工质量的影响

本研究通过单因素试验方法,开展钻削碳纤维复合材料的试验研究。采用KISTALER公司9265B型测力仪测钻削轴向力,并采用撕裂因子评价孔形貌质量,对钻削碳纤维复合材料的过程进行分析,研究不同钻削参数对钻削碳纤维复合材料的轴向力和孔加工质量的影响。试验结果表明:随着进给量的增大,轴向力逐渐增大,孔退钻口撕裂因子呈现先减小再增大的趋势,孔进钻口撕裂因子则呈现逐步小幅增大的趋势。随着转速的增大,轴向力逐步小幅减小,孔退钻口撕裂因子随之减小。并且,进给量对轴向力和孔加工质量的影响远大于转速对轴向力和孔加工质量的影响。在相同条件下,孔进钻口的毛刺、撕裂等缺陷明显少于退钻口的缺陷。     

钛合金/铝合金叠层低温与干式钻削实验研究

钛合金/铝合金是飞机装配制孔中的典型叠层结构,目前多采用干式钻削,存在刀具磨损严重、孔加工质量难以保证的问题。为了探寻更有效的冷却润滑方式,研究利用超临界二氧化碳作为冷却介质,采用内冷的方式对切削区域进行快速冷却,进行低温叠层钻削实验,分析总结了低温钻削性能规律,并通过对比实验与干式钻削作比较。通过冷却介质出口温度梯度实验,研究了出口温度对钻削的影响。结果表明,相比于干式钻削,低温钻削能降低轴向力,降低表面粗糙度值,减小钛合金的出口毛刺高度,获得更好的孔径一致性。     

刀具类型对CFRP制孔缺陷及孔壁质量的影响研究

使用不同类型刀具对碳纤维复合材料(CFRP)制孔过程中的缺陷和孔壁质量进行研究,设计了单因子实验,通过选取制孔刀具传统麻花钻、螺旋铣刀、台阶钻、烛心钻,对CFRP进行了切削制孔实验,利用超景深电子显微镜观测加工缺陷,使用表面粗糙度测量仪测量孔壁粗糙度。结果表明,与传统麻花钻制孔相比,采用螺旋铣工艺、台阶钻或烛心钻制孔能够减小孔口处的分层缺陷,有效提高孔表面质量。     

切削参数对碳纤维复合材料制孔质量的影响

高效、高质量的制孔是航空航天用碳纤维复合材料机械加工的基本要求。本文采用直径为3 mm的纳米金刚石涂层硬质合金钻头钻削T300碳纤维复合材料,研究切削参数(切削速度v=20,40,60,100,150 m/min;进给量f=0.01,0.018,0.03,0.045,0.06mm/r)对轴向力和制孔质量的影响规律。结果表明,轴向力随着进给量的增大而增大,随着切削速度的增大而减小,并建立轴向力Fz与切削速度v和进给量f之间的关系式:F_z=117.5·v~(-0.151)·f~(0.224)。在不同的切削参数下,孔入口处均未出现撕裂和毛刺,表现出良好的加工质量。随着进给量的增大,孔出口区质量在低速条件下由分层和撕裂变为毛刺,在高速条件下没有毛刺,出口区完整。总之,在高速和高进给条件下可以获得相对较好的制孔质量。     

CFRP/Al叠层材料变进给钻削表面质量分析

为了降低碳纤维增强复合材料(CFRP)/铝合金(Al)叠层制孔产生的纤维撕裂和毛刺高度,提出了一种基于几何函数设定进给量的方法,即当刀具位于叠层材料钻入区、叠层区、钻出区时,主轴进给量按正弦曲线的变化规律进行设定。在相同的加工效率下,将该方法同定进给钻削进行实验对比,分析了变进给钻削对轴向力、复合材料撕裂损伤以及金属孔的毛刺高度的影响。结果表明:相比于定进给钻削,变进给钻削降低了相同切削位置处的轴向力,并使出口处的撕裂因子以及金属毛刺高度分别减少了3.28%、31.65%,对入口处的表面质量则影响不大。     

钛合金对CFRP/Ti叠层构件螺旋铣孔表面质量的影响

为研究CFRP/Ti叠层构件螺旋铣孔时钛合金对复合材料孔表面质量的影响,通过对比复合材料孔下方有无钛合金支撑,对复合材料加工过程中的加工损伤进行分析。结果表明,无钛合金支撑的复合材料孔在稳定加工阶段轴向切削力及波动幅度较大;两种加工方式下复合材料孔入口处无明显缺陷,孔出口处存在毛刺现象;无钛合金支撑的复合材料的孔壁存在加工损伤,且出口侧存在纤维拔出。因此在CFRP/Ti叠层构件螺旋铣孔时,复合材料孔下方有钛合金支撑能有效降低复合材料在稳定加工阶段的轴向切削力及其波动幅度,还能提高复合材料孔出口质量及孔壁质量。     

大厚径碳纤维复合材料三维钻削有限元仿真及试验研究

针对CR929远程宽体客机承力构件制孔出口分层缺陷预测难、制孔载荷预测试验成本高等问题，开展大孔径碳纤维增强树脂基复合材料(CFRP)三维钻削仿真及试验研究。首先基于ABAQUS用户自定义子程序接口，利用Fortran语言编写CFRP宏观力学本构模型；随后建立大孔径CFRP三维钻削仿真过程有限元模型，并验证其正确性；最后利用有限元模型预测不同加工参数下的制孔轴向力、扭矩及出口分层损伤。研究结果表明:基于三维实体单元建模的复合材料，三维钻削有限元仿真模型可以可靠地预测制孔过程中的轴向力、扭矩。在CFRP出口处嵌入黏结单元可以预测制孔出口分层的形状。在相同工艺参数条件下, 制孔的轴向力、扭矩、出口分层的仿真预测与试验结果最大相对误差分别为15.0%、19.0%、12.4%。      

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。     

Characterization of the dry high speed drilling process of woven composites using Machinability Maps approach

Damage to woven carbon fiber composites and high tool wear are the main challenges in drilling processes. The effect of speeds and feed rates on the damage mechanisms, namely, delamination, surface roughness, fiber pullout, thermal damage, hole circularity and hole diameter error were established using a newly introduced concept of Machinability Maps. Using an instrumented tool, the cutting temperature was measured. The results showed that the effect of tool wear on the quality maps can be established through the changes in the thrust and cutting forces.     

Drilling delamination and thermal damage of carbon nanotube/carbon fiber reinforced epoxy composites processed by microwave curing

The drilling-induced delamination and thermal damage of carbon fiber reinforced epoxy composite materials are serious problems especially for high value components of the aviation industry. To suppress the delamination and drilling ablation, an innovative approach was employed in this study. The multiwalled carbon nanotubes (MWCNTs) were introduced to the matrix resin to improve the interlaminar strength and thermal conductivity. The as-prepared composite was processed by microwave curing to enhance the interface strength between carbon fiber and the carbon nanotubes modified matrix. During the drilling processes, optical fiber Bragg grating sensors were utilized to precisely measure the drilling temperature. Experimental results indicated that the interlaminar fracture toughness was increased by more than 66% compared to that of the traditional thermal cured samples without MWCNTs. And the delamination factor was decreased by 16% according to the computerized tomography scanning results. The maximum drilling temperature of the MWCNTs reinforced composite was below the glass transition temperature of the matrix resin and declined by 23 °C compared to traditional composites. With this novel method of carbon nanotube modification and microwave curing, we provide the capability of reducing the drilling delamination and thermal damage of carbon fiber composites simultaneously, and explored the possibility of manufacturing and machining integration.     

基于MQL的碳纤维复合材料制孔表面质量及切削力试验

目的 减少碳纤维增强复合材料(CFRP)制孔表面毛刺及边缘凸起等缺陷。方法 对比研究在干切削和微量润滑(MQL)2种加工条件下碳纤维增强复合材料(CFRP)的制孔,在切削速度一定时,探究切削方式、进给速度对制孔尺寸精度、表面质量、切削力的影响。采用方差分析对各影响因素及其权重进行分析。结果 得出了切削方式和工艺参数对制孔尺寸精度、切削力、表面质量的影响规律。试验结果表明,在微量润滑条件下,由于润滑和降温的影响,表面毛刺得到有效去除,纤维断面平整,剪切作用明显,抑制了由温升所引起的边缘隆起膨胀现象,试样的表面质量得到显著提高,切削力整体降低。在干切削和微量润滑条件下对制孔尺寸精度影响最大的是切削方式。对于切削力,在干切削时受到切削方式的影响最大,在微量润滑条件下受到进给速度的影响最大,随着进给速度的增大而增大。结论 在现有试验条件下,微量润滑的加工质量总体上优于干切削的加工质量,其制孔尺寸的精度整体更高,其切削力最大降低了84.26%。     

Characterization and optimization of orbital drilling of woven carbon fiber reinforced epoxy laminates

The emerging process of orbital drilling (OD) can greatly reduce or eliminate the defects associated with the drilling of composites; e.g., delamination, and thermal damage. The effects of the OD process parameters on the hole quality attributes were established in the form of machinability maps; an aspect that has not been reported before. The results showed significant enhancement in the hole quality compared to conventional drilling, due to the reduced axial force and cutting temperature, resulting from the redistribution of the load exerted by cutting edges and the cooling effect of the unstable rotational air flow in the tool-workpiece annular gap.     

深冷处理对440C马氏体不锈钢组织和耐蚀性的影响

研究了深冷处理对440C马氏体不锈钢组织和耐蚀性的影响。研究表明,液氮深冷处理后440C不锈钢硬度可提高2.3 HRC,残留奥氏体含量降低了11.7%,72 h中性盐雾试验表面无明显点蚀。440C不锈钢淬火后室温停留2 h以上残留奥氏体含量明显增加,硬度值、耐蚀性下降。实际生产中,淬火与液氮深冷处理时间间隔应不超过2 h。     

钎焊金刚石磨粒钻钻削C/SiC陶瓷基复合材料孔时切屑对钻削过程的影响

钎焊金刚石磨粒钻适合钻削碳纤维增强碳化硅陶瓷基复合材料孔,但大量切屑会对孔的钻削过程产生不利影响。为此,针对切屑排出过程,分析切屑形貌,研究钻削时切屑对轴向钻削力、孔加工质量、钻头磨损的影响。结果表明:切屑对轴向钻削力有影响,尤其钻削深孔时影响显著。切屑对孔进口的加工质量几乎没有影响,只表现为孔进口处的轻微崩边;切屑对孔出口的加工质量影响显著,可引起严重的纤维断裂、撕裂缺陷以及基体的大区域脱落。同时,切屑加剧钻头磨损,使钻头不仅出现崩刃、微裂纹等轻微磨损,而且还产生基体剥落、金刚石剥落等严重磨损行为。      

芳纶纤维复合材料制孔表面缺陷机理及工艺试验研究

目的 减少芳纶纤维复合材料制孔的表面缺陷.方法 通过对芳纶纤维复合材料进行钻削试验,研究钻削过程中刀具的作用机理.通过不同切削速度和进给速度对制孔入口表面缺陷和孔内壁表面粗糙度的影响,研究制孔过程中的缺陷损伤,并进行相关评定.通过改变装夹工艺方式,研究装夹工艺系统的刚度对制孔表面缺陷的影响.结果 切削速度与进给速度对制...     

Effects of exit back-up on delamination in drilling composite materials using a saw drill and a core drill

Machining of composites has caught greater attention in manufacturing of structural parts in aerospace, automobile and sporting goods. Composite materials have advantageous features in strength and stiffness coupled with lightweight compared to the conventional metallic materials. Amongst all machining operations, drilling is the most commonly applied method for generating holes for riveting and fastening the structural assembly. Delamination is one of the serious concerns in drilling holes in composite materials at the bottom surface of the workpiece (drill exit). Quite a few references of the drilling of fiber-reinforced plastics report that the quality of cut is strongly dependent on drilling parameter as well as the drill geometry. Saw drills and core drills produce less delamination than twist drills by distributing the drilling thrust toward the hole periphery. Delamination can be effectively reduced or eliminated by slowing down the feed rate when approaching the exit and by using back-up plates to support and counteract the deflection of the composite laminate leading to exit side delaminations. The use of the back-up does reduce the delamination in practice, which its effects have not been well explained in analytical fashion. This paper predicts the effects of backup plate on delamination in drilling composite materials using saw drill and core drill. The critical drilling thrust force at the onset of delamination is calculated and compared with that without backup. The well known advantage of industrial use of backup can be understood fundamentally by the fact that the threshold thrust force at the onset of delamination is increased making the delamination less induced.     

Feasibility study of the rotary ultrasonic elliptical machining of carbon fiber reinforced plastics (CFRP)

Carbon fiber reinforced plastics (CFRP) are used for various aircraft structural components because of their superior mechanical and physical properties such as high specific strength, high specific stiffness, etc. However, when CFRP are machined, rapid tool wear and delamination are troublesome. Therefore, cost effective and excellent quality machining of CFRP remains a challenge. In this paper, the rotary ultrasonic elliptical machining (RUEM) using core drill is proposed for drilling of holes on CFRP panels. This method combines advantages of core-drill and elliptical tool vibration towards achieving better quality, delamination free holes. The cutting force model and chip-removal phenomenon in ultrasonic elliptical vibration cutting are introduced and analyzed. The feasibility to machine CFRP for RUEM is verified experimentally. The results demonstrate that compared to conventional drilling (CD), the chip-removal rate has been improved, tool wear is reduced, precision and surface quality around holes is enhanced, delamination at hole exits has been prevented and significant reduction in cutting force has been achieved.