芳纶纤维复合材料高速钻削刀具磨损机理研究

目的 研究高转速条件下芳纶纤维复合材料（AFRP）钻削过程中刀具的摩擦学行为。方法 采用TiAlN涂层超细微碳化钨晶粒麻花钻对芳纶纤维复合材料进行高速钻削试验。首先,研究整个寿命阶段刀具后刀面磨损规律。其次,观察分析刀具磨损处的微观形貌,深入研究刀具的失效形式与磨损机理。结果 刀具磨损可分为3个阶段,分别为初期磨合阶段、稳定磨损阶段、急剧磨损阶段,各阶段磨损速率各不相同,稳定磨损阶段最小,急剧磨损阶段最大。涂层刀具的失效形式为涂层与基体材料剥落以及后刀面磨损,磨粒磨损为主要的磨损形式,同时伴随着不同程度的粘结磨损和氧化磨损,使后刀面形成诸多凹坑和划痕。结论 丰富了复合材料高速钻削中的刀具磨损机理,并为钻削刀具的选用及性能优化提供理论与试验依据。     

冷却空气流向对CFRP制孔刀具磨损及孔质量的影响

在加工碳纤维增强树脂基复合材料（CFRP）时多用冷却工艺来提升加工质量。其中,空气冷却工艺因其方便性被广泛用于实际加工中。然而,目前尚缺少空气冷却方向对刀具磨损和加工质量的研究。文章通过控制冷却空气的方向,开展了干式切削、正向喷气和逆向吸气冷却条件下钻削CFRP材料的研究。获得了上述冷却条件对双顶角刀具第二主切削刃末端磨损的影响规律,发现气体冷却都能有效抑制刀具磨损,且在对出口温度影响相近的条件下,逆向冷却比正向冷却能够更好地抑制磨损。进而分析了冷却条件对钻削出口损伤的抑制效果,发现冷却、冷却方式对孔出口撕裂深度的抑制作用都较小,但逆向吸气冷却能够有效减小出口的毛刺高度,是一种有效提高制孔质量的冷却工艺。      

超细颗粒增强铝复合材料钻削特性研究

通过超细颗粒增强铝复合材料钻孔试验，找出了钻削用量等因素对钻削力的影响规律，并用轴向力与扭矩之比值来表示铝复合材料的钻削特性；从钻削力考虑，高速钢钻头完全能满足超细颗粒（＜0．5μm)增强铝复合材料的钻孔要求。     

双顶角钻头钻削CFRP复合材料的刀具磨损机制

为了研究碳纤维增强树脂基(CFRP)复合材料切削中刀具在不同部位的磨损机制和规律,以典型的硬质合金双顶角钻头作为研究对象,主要研究对出口分层影响较大的横刃和对最终制孔成型影响较大的第二主切削刃的磨损机制及规律。通过减小磨损测量间隔,并引入切削刃钝圆半径以及后刀面磨损带宽度,表征了横刃和第二主切削刃在加工中的衰变过程。基于显微刃口观测和钝圆半径变化,揭示横刃易崩刃和第二主切削刃磨损后又受到重新刃磨的磨损机制,获得了此类型钻头不同部位的磨损规律。同时,基于上述的磨损表征,研究不同切削部位磨损量对钻削轴向力和力矩的影响,横刃轴向力与横刃钝圆半径变化相关性较小,而钻削最大力矩与第二主切削刃后刀面磨损变化规律相一致。     

CFRP管面钻削缺陷形成机制

碳纤维增强复合材料(CFRP)传动轴因性能优越广泛应用于汽车、航空航天、船舶、冷却塔风机等轻量化领域,但其钻削过程中容易出现毛刺、分层等缺陷。为了揭示CFRP管面钻削缺陷形成机制,选择双锋角钻头和三尖二刃钻对CFRP管面钻孔,利用分步钻削盲孔和通孔的方法,分析了损伤部位的受力情况,揭示了入口撕裂、出口毛刺和分层产生原因。根据实验结果,发现双锋角钻头钻孔时入口撕裂损伤较大,损伤位置在钻头与管面接触最低点,且主要是那部分水平缠绕CFRP管的纤维,原因是水平缠绕的纤维屈曲变形最大,对切削力更加敏感。双锋角钻头和三尖二刃钻的横刃对孔最终出口分层没有影响,主切削刃的切削行为决定孔最终出口分层。相同钻头钻孔时,轴向力不是唯一影响分层因子的因素,还需考虑切削热。相比双锋角钻头,三尖二刃钻因锋利的外缘尖角能有效划断纤维,使出口分层较小。     

硬质合金台阶钻结构参数及钻削工艺参数对CFRP开孔性能的影响

基于VMC850B立式加工中心和UltraPAC超声C-扫描仪,搭建了碳纤维增强树脂基复合材料(CFRP)钻削试验平台,探讨了台阶钻结构参数及钻削工艺参数对CFRP钻削过程中的钻削轴向力和分层因子的影响。结果表明,钻削工艺参数对第一段钻削轴向力影响较大,台阶钻结构参数对第二段钻削轴向力的影响较大;分层因子的大小与第一段钻削轴向力和第二段钻削轴向力有关,当第一段和第二段直径比d/D0.5时,分层因子主要与第一段钻削轴向力有关;减小分层的优水平组合为第一段直径2.8mm,第二段锋角95°,主轴转速7000r/min,进给速度2.5mm/s。     

Al2O3f＋Cr／ZL109混杂复合材料的复合振动钻削加工

用挤压铸造法制备了三氧化二铝短纤维和碳短纤维混杂增强ZL109合金复合材料、并采用永磁复合激振方式进行了轴向与扭转复合振动钻削加工，研究了该材料的钻削加工性及振幅和振动频率对钻削力、钻头磨损和孔精度的影响。结果表明。采用这种复合振动钻削方式．可更明显降低钻削力和提高加工精度。选择合理的振动参数。也可以减轻刀具磨损，因而可改善Al2I3f Cf／ZL109混杂复合材料的钻削加工性。     

基于CFRP层合板钻削轴向力时变曲线的钻头几何形状分析

为探索能够实现碳纤维增强复合材料（CFRP）层合板低损制孔的钻头几何形状,采用4种不同几何形状的钻头,对T800级CFRP层合板进行钻孔实验研究,分析了钻头几何形状对钻削轴向力的影响,探讨了钻削轴向力与分层损伤之间的关系。结果表明:轴向力归零速度与出口分层因子有较好的正相关性,可采用钻削轴向力归零速度来表征钻头几何形状对CFRP层合板钻孔的适用性能。同时,实验发现切削区域具有多阶段几何特征的钻头,在钻出工件底部时轴向力是分阶段缓慢归零,出口分层因子较小。      

一种超声超低温冰层支撑辅助CFRP钻削方法

提出一种超声振动+超低温液氮+由超低温环境形成的冰冻支撑层(Ultrasonic vibration+Cryogenic liquid nitrogen+Frozen support layer,UCF)来辅助碳纤维增强树脂基复合材料(Carbon fiber reinforced poly-mer,CFRP)钻削制孔...     

Numerical prediction of the thrust force responsible of delamination during the drilling of the long-fibre composite structures

In this paper, a numerical FE analysis is proposed to calculate the thrust forces responsible for the defect at the exit of the hole during the drilling phase of long-fibre composite structures, within a quasi-static framework. This numerical model – compared with the analytical models studied in the literature – takes into account the tool point geometry as well as the shear force effects in the laminate. The validation of this numerical model is carried out thanks to punching tests conducted at low speed on two types of semi products in carbon/epoxy long fibre manufactured by Hexcel composites. The numerical results provide the right correlation with the experimental values. Moreover, the comparison between the numerical thrust forces and those provided by the analytical models of the literature is called into question.     

Critical thrust force at delamination propagation during drilling of angle-ply laminates

A new formulation for the critical thrust force necessary to propagate the delamination generated during the drilling operation of an antisymmetric angle-ply laminate is proposed by modeling the delamination zone as an elliptical shape. The critical thrust force is analytically derived with the consideration of bending, twisting and mid-plane extension of the delamination zone. And then to maximize the critical thrust force, the optimal design of an angle-ply laminate is performed to find the optimal number of fiber per millimeter, optimum diameter of fiber and optimum lamination angle using ADS (Automated Design Synthesis).     

碳纤维增强复合材料螺旋铣孔切削力及加工质量研究

针对传统钻孔方法加工复合材料时易导致分层、撕裂等缺陷的问题,采用螺旋铣作为新的制孔技术,根据飞机装配现场的实际加工条件,构建以机器人为移动载体、螺旋铣孔终端执行器为加工单元、螺旋铣孔专用刀具为切削工具的加工系统,采用该加工系统对碳纤维增强复合材料(CFRP)螺旋铣孔关键工艺参数进行正交试验,并讨论了刀具主轴转速、每齿进给量和轴向切削深度等工艺参数对切削力的影响规律;通过对加工缺陷的监测,探讨了切削力与CFRP分层、撕裂等缺陷之间的关系;最后对工艺参数进行优化,经试验验证,优化后轴向切削力较优化前降低26%以上,孔入口及出口处均无撕裂、毛刺,加工质量最优。     

Tool geometry based prediction of critical thrust force while drilling carbon fiber reinforced polymers

Carbon fiber reinforced polymers(CFRPs) are known to be difficult to cut due to the abrasive nature of carbon fibers and the low thermal conductivity of the polymer matrix.Polycrystalline diamond(PCD) drills are commonly employed in CFRP drilling to satisfy hole quality conditions with an acceptable tool life.Drill geometry is known to be influential on the hole quality and productivity of the process.Considering the variety of CFRP laminates and available PCD drills on the market,selecting the suitable drill design and process parameters for the CFRP material being machined is usually performed through trial and error.In this study,machining performances of four different PCD drills are investigated.A mechanistic model of drilling is used to reveal trade-offs in drill designs and it is shown that it can be used to select suitable feed rate for a given CFRP drilling process.     

基于径向基函数神经网络的CFRP切削力预测

碳纤维增强树脂基复合材料(CFRP)加工中基体相极易因切削力过大而破坏,并迅速扩展至加工表面以下而形成损伤。为了准确预测其切削力并加以控制,基于实验切削力数据建立了人工神经网络切削力模型,预测了不同纤维角度、切削深度和刀具角度下加工CFRP的切削力变化规律,并完成了不同刀具角度及切削参数下典型纤维角度CFRP单向板的直角切削实验,对预测模型进行验证,其预测精度可达85%以上。结合成屑过程在线显微观测结果可知:纤维角度是影响CFRP切削力的主要因素, 0°~135°范围内,切屑形成方式为切断型和开裂后弯断型;切削力随纤维角度增大呈先减小后增大的趋势, 135°时最大,随切削深度增加,切削力总体呈增大趋势。      

Critical thrust force at propagation of delamination zone due to drilling of FRP/metallic strips

A critical thrust force at propagation of delamination zone due to drilling of an infinite FRP/metallic strip is obtained by the definition of energy release rate.The critical thrust force is derived in terms of the size of the delamination zone. The differences of the results by the previous and present methods are discussed.     

Influence of machining parameters and new nano-coated tool on drilling performance of CFRP/Aluminium sandwich

Drilling and fastening of hybrid materials in one-shot operation reduces cycle time of assembly of aerospace structures. One of the most common problems encountered in automatic drilling and riveting of multimaterial is that the continuous chips curl up on the body of the tool. Drilling of carbon fiber reinforced plastic (CFRP) is manageable, but when the minute drill hits the aluminium (Al) or titanium (Ti), the hot and continuous chips produced during machining considerably damage the CFRP hole. This study aims to solve this problem by employing nano-coated drills on multimaterial made of CFRP and aluminium alloy. The influence of cutting parameters on the quality of the holes, chip formation and tool wear were also analyzed. Two types of tungsten carbide drills were used for the present study, one with nano-coating and the other, without nano coating. The experimental results indicated that the shape and the size of the chips are strongly influenced by feed rate. The thrust force generated during drilling of the composite plate with coated drills was 10–15% lesser when compared to that generated during drilling with uncoated drills; similarly, the thrust force in the aluminium alloy was 50% lesser with coated drills when compared to thrust force generated without coated drills. Thus, the use of nano-coated drills significantly reduced the surface roughness and thrust force when compared with uncoated tools.     

Prediction of quench in cable-in-conduit conductors considering current-sharing effect of copper

A simple 0D analytical model for the prediction of the quench point has been presented by Anghel [Anghel A. A simple model for the prediction of quench point in cable-in-conduit conductors. Cryogenics 2003;43:225–32]. The model offered a straightforward approach to estimate the quench behavior of cable-in-conduit-conductor (CICC) and provided a clear view of the relationships between conductor parameters and its quench properties. However, this 0D model did not address the current-sharing effect of copper. In this paper, it was considered by approximation that superconductor and copper form two resistors in parallel, the redistribution of current due to the copper was taken into account. The result of the new model was compared with that of a previous model. The 0D model predicts the quench with a higher accuracy.