GFRP旋转超声振动套孔加工仿真及工艺研究

玻璃纤维增强树脂基复合材料(Glass fiber reinforced plastic,GFRP)具有比强度高和比模量大等特点,广泛应用于航空航天、船舶军工和汽车制造等领域。针对GFRP复合材料制孔加工中容易出现分层、撕裂等缺陷,采用旋转超声振动套孔加工方法对其进行磨削制孔的理论和试验研究。分析了旋转超声振动套孔加工中单颗磨粒的运动学特性,基于Hashin失效准则,对GFRP复合材料最具代表性的0°和90°角度铺层玻璃纤维进行磨削常规和旋转超声振动套孔加工有限元仿真研究。相较于常规加工,超声振动加工使磨粒具有周期性动态冲击磨削效果,改变了材料的去除方式,降低了磨削力,结果表明：超声振动加工的轴向力最大降幅可达20.1%,同时有效抑制了出口分层缺陷,孔壁表面的纤维断口光滑平整,制孔质量得到有效改善。     

复合材料超声振动低损伤制孔技术研究

为了研究碳纤维复合材料超声振动加工机理,本文提出了直角切削三维细观有限元方法并开展了手持式超声制孔实验。首先,基于直角-斜角切削转换关系构建热力耦合有限元模型进行普通和超声振动直角切削仿真,实现对制孔损伤如纤维断裂、基体破坏及纤维-基体界面脱粘的预测,研究了振动频率如幅值和频率对切削力的影响规律;然后,基于四组特殊纤维方向角的有限元仿真结果,进行了能量分析以量化不同能量耗散机制在普通和超声振动直角切削下的百分比,结合切屑形貌对比,针对为何超声振动能减小钻削力及提高制孔质量进行了剖析。最后,基于仿真获取的振动参数影响规律开展了普通钻削及超声振动钻削的对比实验,并对钻削力与亚表面损伤情况进行了对比。结果表明,基于有限元仿真获取合理的振动参数,有助于实际加工应用中减小钻削力及提高加工质量。     

超声振动辅助钻削BK7的试验研究

针对BK7光学玻璃在传统制孔过程中出现的入孔边缘质量差和轴向力大的问题,提出了采用50kHz超声波辅助加工装置,开展超声振动辅助钻削BK7的对比实验和加工参数单因素实验。从普通加工和超声振动辅助加工基本运动学角度深入分析了加入超声振动后轴向力减小的原因,以及不同振幅、转速对轴向力减小幅度的影响。研究结果表明：与传统钻削相比,金刚石套料钻超声振动辅助钻削不仅可以获得更小的轴向力,还可以有效提高入孔边缘质量,当振幅增大、转速降低时,增大了轴向力的减小幅度。     

基于超声振动的硬脆性材料磨削加工入孔崩边研究

针对陶瓷等硬脆材料磨削加工中出现的崩边问题,对氧化锆陶瓷孔加工过程中出现的入孔崩边情况进行了研究。使用有限元软件ABAQUS,对超声振动辅助磨削氧化锆陶瓷孔加工进行了仿真,建立了氧化锆陶瓷JH2本构模型;研究了入孔崩边的形成机理,结合有限元仿真结果,设计了超声振动辅助磨削氧化锆陶瓷孔加工实验;通过建立入孔崩边的评价指标,分析了主轴转速、进给速度和超声功率对入孔崩边的影响规律,并对仿真结果进行了验证。研究结果表明:和实验相比,仿真得出的崩边面积平均误差在10%以内;随着主轴转速和超声功率的增加,入孔崩边情况得到明显的改善,在100%超声功率条件下崩边面积减少了38%以上,随着进给速度的增加入孔崩边面积明显增大。     

GFRP旋转超声套孔加工轴向力试验研究

轴向力是反映孔加工过程和状态的最重要参数之一,对纤维增强复合材料的制孔质量有直接影响.为分析旋转超声套孔加工中轴向力随工艺参数的变化规律,基于旋转超声套孔加工中磨粒的运动学特性,建立钻削力数学预测模型,并对玻璃纤维增强复合材料进行孔加工试验研究.试验结果表明:轴向力随着主轴转速提升或进给速度降低呈现减小趋势,与钻削力数...     

旋转超声磨削加工中刀具结合剂类型与加工性能的关系

实验分析了硬脆材料旋转超声磨削过程中刀具结合剂类型对加工性能的影响以便提高加工精度和加工表面的完整性.首先,采用能谱分析研究了铁基、陶瓷基和青铜基3种超声振动刀具中结合剂与金刚石颗粒的把持形式,并根据相同加工工艺条件下刀具磨损形式确定了把持力大小.然后,结合超声振动刀具特性,通过旋转超声磨削加工实验研究刀具结合剂类型与切削力、刀具磨损量、加工表面完整性的关系,并对实验结果进行了分析.实验结果表明:相对于陶瓷基和青铜基结合剂超声振动刀具,铁基结合剂超声振动刀具把持力最大,Z轴切削力平均值最小(为46.8 N);加工18 000 mm3材料后,刀具轴向磨损量最小(为0.1 mm);而陶瓷基结合剂超声振动刀具加工表面质量最好,表面粗糙度最大值为21.79 μm.结果证实铁基超声振动刀具适用于粗加工,陶瓷基超声振动刀具则适用于精加工.     

调幅式振动刀柄的设计与有限元仿真分析

设计了一种调幅式轴向低频振动刀柄,分析了振动刀柄的整体结构布局及其工作原理.采用机床主轴旋转运动作为动力输入,带动正弦曲面旋转以实现振幅输出,基于两组正弦曲面相位差实现刀柄振幅调节.基于GH4169高温合金材料,运用ABAQUS有限元软件进行了三维钻削仿真试验,对比分析了GH4169高温合金在普通钻削和轴向低频振动钻削下轴向力和钻削扭矩之间的差异.结果 表明:GH4169高温合金轴向低频振动钻削可以降低最大轴向力约46％,降低最大钻削扭矩约73％,可显著改善钻削条件,提高孔加工质量.     

旋转超声磨边机床设计与实验研究

为探究旋转超声磨边在瓷砖加工中的应用,使用ANSYS软件对旋转超声磨边机床的超声振子进行模态分析,发现谐振时工具头把纵向振动分解为纵向和径向振动.搭建了旋转超声磨边机床,包括旋转超声磨边主轴和四轴运动测试平台.并且使用机床研究了有无超声情况下主轴转速和进给速度对轴向磨削力的影响.结果表明:在瓷砖磨边过程中,低主轴转速下添加超声振动可减小轴向磨削力;不同进给速度下,旋转超声磨边的轴向磨削力比传统磨边小.     

超声振动切削加工机理及切削性能分析

针对氧化铝陶瓷材料切削加工,分别采用传统切削和超声振动切削加工氧化铝陶瓷工件,使用ABAQUS有限元软件进行建模仿真,分析工程陶瓷在两种切削情况下的切削性能。对实验结果数据进行对比分析得出:超声振动切削工件过程中所产生的应力要小于传统切削;超声振动切削工件过程中所产生的最大温度要远远小于传统切削;传统切削加工产生的切屑和超声振动切削加工产生的切屑形态不同;超声振动车削力远小于传统加工。     

SiC颗粒增强铝基复合材料的超声振动钻削试验研究

在分析振动切削基本原理的基础上,采用了超声振动钻削的方法对金属基复合材料进行孔加工。借助自行研制的超声钻削设备,通过使用不同材质的硬质合金麻花钻,对两种不同含量的SiC颗粒增强铝基复合材料进行了普通钻削与超声振动钻削的对比试验。从复合材料的破碎形式、超声振动钻削力、钻头磨损以及孔的加工质量等4个方面对超声振动钻削复合材料的特性进行了研究。结果表明,轴向超声振动钻削能够提高入钻的定位精度及孔的表面质量,有效地改善钻头横刃的磨损,同时,钻削扭矩较普通钻削降低约30%。     

Chipping minimization in drilling ceramic materials with rotary ultrasonic machining

Ultrasonic machining (USM) has been considered as a new cutting technology that does not rely on the conductance of the workpiece. USM presents no heating or electrochemical effects, with low surface damage and small residual stresses on workpiece material, such as glass, ceramics, and others; therefore, it is used to drill microholes in brittle materials. However, this process is very slow and tool wear dependent, so the entire process has low efficiency. Therefore, to increase microhole drilling productivity or hole quality, rotary ultrasonic machining (RUM) is considered as a strong alternative to USM. RUM, which presents ultrasonic axial vibration with tool rotation, is an effective solution for improving cutting speed, precision, tool wear, and other machining responses beyond those of the USM. This study aims to reduce the microchipping or cracking at the exit of the hole, which inevitably occurs when brittle materials are drilled, with consideration of tool wear. To this end, response surface analysis and desirability functions are used for experimental optimization. The experimental results showed that the proposed RUM scheme is suitable for microhole drilling.     

Experimental study on trepanning drilling of the ceramic composite armor using a sintering diamond tool

Laminated ceramic composite armors made of engineering ceramics, fiber-enforced composite, and lightweight alloy are expected to be used widely in armor protection area. However, secondary machining is still a problem for the distinct properties of composing materials, and up to now, few reports can be found out about machining technology. In this work, an experimental study on drilling a typical laminated ceramic composite armor by using a special sintering diamond thinwall trepanning tool has been carried out deeply. To improve the machining efficiency, process parameters including the spindle speed and the axial force have been optimized through drilling experiments. Moreover, the three phases of the whole drilling process of the typical ceramic composite armor is proposed, and the machining mechanism and chip forms in each phase have been analyzed. Also, diamond tool skidding phenomena whether at hole exit or during drilling middle engineering ceramics have been explored, and the skidding mechanisms are presented. In addition, the surface quality of a hole wall machined has been studied, and an advisable measure is given. Results achieved in this paper can provide a technical base for diamond trepanning tool drilling similar laminated ceramic composite armors.     

TC4钛合金纵扭超声磨削力热耦合模型及其试验研究

为探究TC4钛合金纵扭超声磨削过程中的力热耦合机理,基于TC4钛合金纵扭超声磨削的磨削力模型、工件表面平均温度模型、质量热容计算表达式建立了其力热耦合模型,并对力热耦合作用下TC4钛合金纵扭超声单颗磨粒去除过程进行有限元仿真,分析磨削力、磨削温度的相互影响特性。理论与仿真研究发现,磨削区剧烈的温升会降低钛合金抵抗塑性变形的能力,抑制磨削力的增长速率。最后通过TC4钛合金纵扭超声磨削试验进行验证,结果表明,纵扭超声的引入能明显降低磨削力和磨削温度,磨削力和磨削温度的降低幅度分别达到19.39%和12.41%;磨削温度随着磨削深度、砂轮转速和工件进给速度的增大而升高,且随着磨削温度的升高磨削力增长趋势变缓;磨削力和磨削热的减小使工件表面塑性变形和犁沟两侧的塑性隆起高度减小;与普通CBN磨削相比,纵扭超声的引入对表面粗糙度的降低幅度可达到31.21%,在一定范围内增大超声振幅能显著提高加工表面的质量。     

超声振动铣削加工参数对切削力的影响

为了改善传统铣削钛合金的加工条件,研究了进给方向超声振动辅助铣削对切削力的影响。定值计算了不同振动频率、振幅、铣削速度时的净切削时间比,建立了对工件施加超声振动的铣削加工三维有限元模型,根据仿真结果讨论了加工参数对进给方向切削力瞬时值的影响,并结合净切削时间比分析了加工参数对三个方向切削力平均值的影响。研究表明:施加超声振动后切削力明显减小;振动频率小于40kHz和振幅小于30μm时切削力平均值同净切削时间比变化趋势一致,当频率或振幅超过上述值时,刀具、工件间的摩擦力对切削力平均值的影响显著。     

超声振动钻削SiC颗粒增强铝基复合材料时的切削力研究

采用超声振动钻削的方法对金属基复合材料进行孔加工。在自行研制的超声钻削设备的基础上使用不同材质的硬质合金麻花钻,对不同含量的SiC颗粒增强铝基复合材料(SiCp/Al)进行了普通钻削与超声振动钻削的对比试验,并分析比较了加工中切削力的变化规律。试验表明,超声振动钻削可以降低切削力,在一定程度上改善钻削机理。     

CFRP/TC4叠层材料低频振动钻削试验研究

低频振动辅助切削技术是基于传统切削给刀具加上有规律并可控的振动,从而达到减小切削力、提高加工精度和延长刀具寿命的目的。将低频振动辅助切削技术应用到CFRP/钛合金叠层材料制孔中,在孔径、孔壁粗糙度和入口质量等制孔质量方面与传统钻削进行对比试验研究。结果表明,振动钻削在制孔质量上具有明显的优势。     

组合式负荷传感器旋转效应的研究

针对寄生分量会引起非完全轴对称结构的负荷传感器发生旋转效应,采用有限元模拟和试验分析,研究了有、无均力结构的组合式负荷传感器在不同寄生分量下力传感器所受附加侧向力的变化规律与旋转效应的关系.研究结果表明:均力结构能使组合式负荷传感器的力传感器所受附加侧向力明显下降并趋于平均,从而有效地降低了旋转效应;力传感器所受附加侧向力的波动量可用于预测同一试验力级下组合式负荷传感器旋转效应的大小,为提高测量准确度提供评定依据;试验数据验证了有限元模型的可靠性.     

钛合金高速旋转超声椭圆振动侧铣削切屑特征和刀具磨损研究

难加工材料钛合金在采用传统铣削方式时,随着切削速度的增加,切削力和切削温度都迅速增加,使得切削条件恶化并加速刀具磨损,从而导致刀具过早失效。将超声椭圆振动加工技术引入到高速铣削中,进行了钛合金高速旋转超声椭圆振动侧铣削试验。从切屑特征以及刀具后刀面磨损两个方面研究了高速超声椭圆振动铣削参数匹配对钛合金加工的影响。首先基于高速超声椭圆振动铣削过程中刀具-工件的运动学特点推导出高速超声椭圆振动铣削加工参数与振动参数间的匹配关系,然后利用本实验室自行研制的超声椭圆振动铣削装置进行了不同参数匹配关系下的验证性切削试验。试验结果表明：合理的参数匹配使得超声椭圆振动铣削在高速条件下依然能够实现分离型断续切削加工。相比普通铣削加工,分离型的高速超声椭圆振动铣削能够获得更加微细的切屑,切削热能够被及时地带走;良好的切削条件使得刀具的后刀面磨损均匀而缓慢,从而延长刀具的使用寿命;高速超声椭圆振动铣削能够有效地提高生产效率。     

Theoretical model for cutting force in rotary ultrasonic milling of dental zirconia ceramics

Rotary ultrasonic machining or ultrasonic vibration assisted grinding has superior performance in machining hard and brittle materials, such as dental zirconia ceramics. However, there are few reports about cutting force modeling of rotary ultrasonic milling (RUM) for dental ceramics, especially for cutting force model in feed direction. In this study, the theoretical model of cutting force both in axial direction and feed direction is proposed under the assumption that brittle fracture is the primary mechanism of material removal in RUM of dental ceramics. The effective cutting time and material removal volume have been analyzed to develop the cutting force model. Besides, the number of active abrasive particles has been calculated for the first time during the modeling. The effect of overlapping and intersection of fracture zone in peripheral direction on material removal volume has also been considered via the parameters K ₁ and K ₂. In addition, the relationships between the cutting force and input variables are revealed through the theoretical model. Finally, pilot experiments of RUM on dental zirconia ceramics are conducted to verify the theoretical model. The experimental results are consistent well with the model predictions. Therefore, the theoretical model can be applied to evaluate the cutting force in RUM of dental ceramics.     

Optimum design of cam-roller follower mechanism using a new evolutionary algorithm

Selection of tooling to perform specific operations like drilling and milling on ceramic materials using rotary ultrasonic machining process is an important aspect to meet stringent dimensions on workpiece as well as intended performance of tool. This phenomenon is more critical for micro rotary ultrasonic machining. In the present study, an effort was made to do micro drilling operation of Ø0.3 mm tool with varying geometry, having different wall thicknesses and abrasive grain sizes using design of experiments. The effect of tool-based parameters like grain size and wall thickness has been studied on axial cutting force, radial cutting force, tool wear, edge chipping area and taper. After examining axial and radial cutting forces, it has been concluded that lower wall thickness (80 μm) tool is good for drilling operation; and higher wall thickness (100 μm) tool is good for milling operation under same material removal rate conditions. It has been also investigated that lower wall thickness (80 μm) tool has less edge chipping area and less taper and can impart high drilling depth as compared to higher wall thickness (100 and 150 μm) tool. It is also concluded that lesser grain size (15 μm) tools are advantageous in terms of edge chipping area and cutting force for drilling and milling operations as compared to higher grain size (30, 35 and 45 μm) tool at constant material removal rate. Higher grain size tools have been broken at 1.13 mm³/h material removal rate conditions due to bad profile accuracy. But higher grain size tools have worked fairly well at less material removal rate condition. Higher grain size tools produced less wear. Tool wear was found minimum in higher wall thickness (100 μm) tool having higher abrasive grain size (30 μm). Using inferred results, Ø0.3 mm drilling experiments have been carried out on six aerospace ceramic materials. Also, groove of 0.5 mm size using Ø0.3 mm optimised tool has been successfully carried out in sintered SiC.