CFRP复合材料超声振动套孔分层抑制机理分析

针对碳纤维增强复合材料在传统钻孔过程易出现分层缺陷,采用金刚石空心套刀和超声振动加工技术进行了CFRP超声振动套孔分层抑制机理分析。理论分析了传统麻花钻钻孔与金刚石套刀普通套孔过程的分层机理及评价,超声振动套孔对分层抑制的机理,并且进行了实验验证。结果表明:相比于CFRP普通套孔,超声振动套孔能够有效提高套刀切削性能和排屑效果,降低钻削力12.5%～19.2%,抑制切屑粉尘黏附套刀和料芯堵塞套刀,抑制CFRP分层缺陷形成,改善孔表面质量。     

4J29可伐合金超声振动辅助钻削试验研究

4J29可伐合金由于具有和奥氏体不锈钢相近的难切削特点,传统钻削制孔质量较差,为了研究4J29可伐合金制孔质量的影响因素,提高制孔质量,对4J29合金进行了不同加工参数下的普通钻削和超声振动辅助钻削试验并对钻削轴向力、孔径误差、孔壁粗糙度进行了测量。试验发现:4J29可伐合金在不同加工参数下(切削速度v=0.314～0.942m/s,进给速度f=10～30mm/min),超声振动辅助钻削可降低钻削轴向力,轴向力平均降低35.37N,降幅为18.45%;超声振动辅助钻削可提高制孔精度,孔径误差平均减小17.9μm,降幅为31.5%;超声振动辅助钻削可提高表面质量,对于轮廓算术平均偏差Ra,超声振动辅助钻削使其平均降低了0.4862μm,降幅为28.4%,微观不平度十点高度Rz平均降低了2.4940μm,降幅为20.0%。试验表明超声振动钻削4J29可伐合金比传统钻削加工更具优势,可获得质量更高的加工孔。     

镁合金铰孔收缩量的初步探讨

镁合金在航空工业中早已得到广泛的应用。但在加工过程中却存在着温差变形、弹性变形等特殊问题。本文仅对镁合金铰孔中的弹性变形做以下初步探讨。某材料为ZM5T_4的一个零件,要求在φ9.8的底孔中铰削φ10D(~( 0.03))孔。所选用铰刀的实际尺寸为φ10.005,但铰削后,铰刀却不易退出,10D塞规的通端也无法塞入。显而易见,铰削后的孔径小于铰刀实际尺寸,未能达到图纸要求。我们认为这是由于镁合金材料在内孔铰削时因弹性变形引起孔径收缩所致。为解决这个问题,我们做了一些试验,并初步探讨了孔径收缩量和铰削余量间的函数关     

TC4钛合金深孔钻削试验研究与机理分析

TC4钛合金深孔钻削过程中钻削温度高、排屑路径长,加剧刀具磨损,影响深孔加工质量和精度。为制定可用于实际生产的钛合金深孔钻削加工参数,开展TC4钛合金深孔枪钻加工试验。试验结果表明,钻削温度受钻削速度影响较大,进给量的影响不显著;孔径和圆度随着钻削速度的增加而增大,同轴度随着切削速度增加而先增大后减小;孔的表面粗糙度随着钻削参数的增加而增大,且大参数下深孔表面质量进一步恶化;各组试验加工硬化层在30μm左右,且随着钻削速度增加,切屑挤压变形严重。综合分析后制定的干切削条件下TC4钛合金深孔枪钻的钻削速度为20m/min,进给量为0.08mm/r。     

机夹钻头的应用解决方案

PerfoMAX钻入过程可靠,钻杆、钻头和刀片的寿命长,钻削表面质量高,排屑得到明显改善;新一代的PerfoMAX机夹钻削系统提高了硬质合金材质,采用了新型的刀体镀层,保证了最佳的钻削效果     

超声波激振铰刀铰孔的研究

介绍了将超声波能量施予刀具，使其产生一定振幅的超声频振动铰孔系统，进行了铰孔精度、表面粗糙度的试验，归纳了振动铰孔的规律，对试验结果进行了讨论。     

钛合金铰削

和其他切削加工一样,钛合金铰削也要考虑生产率、经济性以及铰刀耐用度等问题,但铰削表面粗糙度和孔的精度显得更为重要。在造成钛合金切削加工性差难切削的诸因素中,弹性模量小,屈强比大和热扩散率小这三者对属于精加工的铰削工作影响较大。针对以上情况,可在刀具、切削条件等方面采取适当的措施,钛合金的铰削同样也能获得满意的效果。     

孔冷挤压有限元仿真中的铰削分界面位置确定方法

开展孔冷挤压过程有限元仿真计算是残余应力分布获取和疲劳寿命预测的前提。在有限元建模阶段,设置铰削层单元与基体材料单元之间的分界面,是模拟铰制终孔工艺过程的关键。通过弹塑性力学分析,建立了挤压强化过程芯棒、衬套和被挤压强化连接孔的应力分析方法;基于分析中得到的不同位置处微单元的径向位移量,建立了铰削分界面相对位置计算模型。并开展了关键参数的敏感性分析,定量研究了关键参数变化对残余应力分布和径向位移量的影响程度。本工作为孔冷挤压强化有限元模型建立中,铰削层单元与基体材料单元分界面相对位置确定,提供了便捷可靠的方法。     

孔强化对7050铝合金残余应力分布的影响

采用开缝衬套冷挤压工艺对飞机用7050铝合金进行挤压强化,针对不同挤压量及铰削量对孔边残余应力分布的影响进行对比,分析得到挤压量及铰削量与残余应力分布的关系.研究表明:采用冷挤压孔强化技术可以改善孔边应力分布,形成有利的残余压应力层.强化后铰孔会减弱残余压应力,对于φ6mm孔铰削量应控制在0.16mm范围内.残余压应力随强化量的增加而增大,5％的挤压量残余压应力值最大达到-276MPa.     

小口径火炮身管的振动钻削试验研究

针对小口径火炮身管钻削加工时存在的切屑堵塞和内膛质量问题,设计了一套低频振动装置。通过振动钻削和普通钻削的对比试验,该装置能有效地解决堵屑难题,并提高身管的内膛钻削质量。     

超声波激振铰刀铰孔的研究

本文研究了将超声波能量施予刀具，使其产生一定振幅的超频振动铰孔的工艺方法。进行了铰孔精度、表面粗糙度及其铰孔规律的试验，也探讨了振铰孔的机理。     

航空发动机机匣同轴度的测量与调整

为排除航空发动机振动故障,从某型航空发动机机匣同轴度检测原理入手,研究机匣同轴度的检测机理,针对机匣同轴度不合格故障提出调整与解决措施。制定出选配偏心环、机匣安装边位移铰孔及车削机匣安装边等多种故障修复方法,通过机匣位移铰孔、调整选配偏心环、增设自动化电动测具等改进措施,达到提高机匣同轴度测量精度,保证发动机装配质量要求。     

Research on Ultrasonic Vibration Grinding of the Hard and Brittle Materials

It is well known that grinding techniques are main methods to machine hard and brittle materials such as engineering ceramics. But the conventional grinding has many shortcomings such as poorer surface finish,quicker wear and tear of grinding tools,lower effi-ciency and so on. Ultrasonic vibration grinding (UVG) which combines ultrasonic machining and grinding emerged as a developing and promising technique in recent years. In this paper,experimental studies on UVG were conducted on several kinds of hard and brittle material by altering processing parameters such as vibration frequency and its amplitude,diamond abrasive grit size,cutting depth,feeding speed and rotary speed of tools. The experimental results show that alteration in any of above mentioned parameters will bring effects on the processed surface finish of these materials. Of them,the diamond abrasive grit size has the greatest. Moreover,conven-tional grinding experiments were also carried out on these materials. By comparison,it was found that the UVG is superior to the con-ventional method in terms of the ground surface quality,the working efficiency and the wear rate of tools.     

Improvement of machining accuracy in EDCM by enhanced electrochemical reaming based on a non-metallic backing layer

Electrochemical Discharge Machining (ECDM) is potentially applicable for the fabrication of film-cooling holes. However, It is extremely difficult for the holes to achieve higher precision and machining quality owing to the working liquid diminish in the lateral machining gap. In this study, a non-metallic backing layer was proposed to overcome the diminish of working liquid, and the electrochemical reaming, as a post-processing method for ECDM, was used to further improve the machining accuracy and quality of the holes. First, the three-dimensional morphology of the melted pit of a paraffin backing layer was scanned to obtain the geometric parameters. Then, simulation analysis and experimental verification of auxiliary flushing by using the non-metallic backing layer were performed. The machining performance of the holes machined with electrochemical reaming based on non-metallic backing layer was confirmed by the observations of the surface topography of the hole wall and orifice, measurement of the orifice precision, and analysis of the element composition on the surface of the orifice wall. Finally, an optimum combination of machining parameters for electrochemical reaming is obtained through a process parameter optimization experiment.     

某型发动机压气机第1级整流叶片疲劳试验研究

对某型发动机压气机第1级整流叶片进行了疲劳试验研究.确定了圆柱形榫头叶片的试验装夹方式,进行了2种工艺叶片振动疲劳强度试验的对比,根据对比结果,优化了加工工艺,进行了首批研制检验.对计算和试验结果进行了分析.     

GH4169孔挤压强化工艺过程数值模拟

在验证镍基高温合金GH4169中心孔挤压(CE)三维有限元模型正确性的基础上,利用单元删除法研究倒角、孔挤压-倒角顺序和铰削量3种具体工艺过程对孔边周向残余应力分布的影响。结果表明:孔边小于芯棒过盈量的初始倒角可以减小孔挤压后残余压应力;采用孔挤压-倒角的工艺顺序可以在孔边获得更小的残余压应力。铰孔可增大孔边入口处残余压应力,去除残余压应力极小值部分的材料。因此,在挤压强化后应尽量避免铰孔。     

机床切削稳定性研究

自激振动,或称颤振是机床切削加工时,在没有周期性外力作用下,刀具和工件之间产生的振动.它不仅降低了机床的加工质量和切削效率,而且对机床和刀具的使用寿命产生不利的影响.从理论上推导产生自激振动的条件,并且通过实验进行验证,从而找出避免产生自激振动的措施.通过改变主振系统的刚度方向以及改变k1与k2的差值,就可以提高机床抵抗颤振能力.     

A pre-generated matrix-based method for real-time robotic drilling chatter monitoring

Currently, due to the detrimental effects on surface finish and machining system, chatter has been one crucial factor restricting robotic drilling operations, which improve both quality and efficiency of aviation manufacturing. Based on the matrix notch filter and fast wavelet packet decomposition, this paper presents a novel pre-generated matrix-based real-time chatter monitoring method for robotic drilling. Taking vibration characteristics of robotic drilling into account, the matrix notch filter is designed to eliminate the interference of spindle-related components on the measured vibration signal. Then, the fast wavelet packet decomposition is presented to decompose the filtered signal into several equidistant frequency bands, and the energy of each sub-band is obtained. Finally, the energy entropy which characterizes inhomogeneity of energy distribution is utilized as the feature to recognize chatter on-line, and the effectiveness of the presented algorithm is validated by extensive experimental data. The results show that the proposed algorithm can effectively detect chatter before it is fully developed. Moreover, since both filtering and decomposition of signal are implemented by the pre-generated matrices, calculation for an energy entropy of vibration signal with 512 samples takes only about 0.690 ms. Consequently, the proposed method achieves real-time chatter monitoring for robotic drilling, which is essential for subsequent chatter suppression.     

Influence of alumina abrasive tool wear on ground surface characteristics and corrosion properties of K444 nickel-based superalloy

K444 nickel-based superalloy is an important material to manufacture the gas turbine due to its excellent mechanical properties at high temperatures and corrosion resistance. Currently,grinding is the mostly used method for the surface finish of the K444 alloy components. However,few studies worked on the effects of the abrasive tool wear on the ground surface characteristics and corrosion properties of K444 alloy. This study uses two different-type alumina abrasive tools, i.e.,white alumina(WA)...