力工工艺对7075铝合金紧固孔表面形貌和组织的影响

为研究加工工艺对7075-T7351铝合金飞机装配紧固孔表面质量的影响,通过扫描电子显微镜和光学显微镜,分别对5种不同制孔工艺所产生的表面微观形貌和表层组织变化进行了观察和分析.结果表明,钻扩铰多步慢进给工艺和一步复合制孔工艺所加工出的表面,平整、光滑、加工缺陷少、晶格变形小、变质层薄;而其它工艺条件下,孔表面微观形貌复杂、加工纹路紊乱、表面缺陷多、晶格畸变大,变质层厚,这些加工状况,对紧固孔的装配性能和疲劳寿命都有很大的影响.     

放电加工对模具寿命的影响

放电加工工艺作为模具加工的主工工艺手段，对模具寿命的影响已受到人们的普遍关注，通过对放电加工表面热变质层微观特性的分析，论述了造成模具早期失效的原因和机理，介绍了预防模具人效电加工工艺的措施。     

镍基高温合金脉冲电弧加工表面完整性研究

研究脉冲电弧加工镍基高温合金表面微观形貌,包括变质层厚度及特征、加工表面粗糙度、显微硬度,综合考虑以上各方面,研究脉冲电弧工作时,脉冲频率、占空比两种加工参数对表面变质层完整性的影响规律,得出频率和占空比较高时更容易产生裂纹,较低的频率和占空比会使熔化凝固层的厚度提高。     

电解研磨扩孔新技术研究

电解研磨扩孔是在吸收电解磨削、电解珩磨和金刚石类磨具研磨等技术优点的基础上开发的一种能浮动定心的高效、低成本的孔后处理加工技术。对该技术的工艺原理、表面粗糙度的影响因素、加工精度及磨具电极的使用寿命等方面进行了研究分析。试验结果和初步应用表明，该技术能有效去除孔加工后的变质层(如再铸层等)，改善表面粗糙度，降低或消除残余应力，提高表面质量。     

电解研磨复合加工技术在孔后处理中的应用

电解研磨复合加工方法是把电解加工和研磨加工结合起来，利用中性电解液通以适当的电流，在磨料研磨和电解溶解共同作用下，对零件进行快速、高效的精密加工。把这一加工技术运用于孔后处理中，对该技术的工艺原理、表面粗糙度的影响因素、加工精度及金刚石磨头的使用寿命等方面进行了研究分析。试验结果表明，该技术能有效去除孔加工后的变质层（如再铸层等），降低表面粗糙度值，降低或消除残余应力，提高表面质量。     

电火花加工变质层对模具成型表面的影响

电火花加工是模具成型零件的主要加工手段之一，其物理本质决定了用该手段加工的模具成型表面存在表面变质层，文章对表面变质层的形成机理、变质层对模具质量和寿命的影响进行了分析，并提出了对策。     

铝合金研磨加工表面自相关性分析

研磨加工是重要零件在磨削后进行去除表面缺陷层、降低粗糙度和波纹度为目的的光整加工工艺。试验在UNIPOL-802型精密研磨抛光机上完成,加工试样为磨削加工后粗糙度为0.6μm的2A12铝合金,加工表面形貌和微观几何参数用M ICROMESURE2和TR200表面轮廓仪测量。应用随机过程中的自相关性对磨削表面和研磨加工表面进行研究。分析结果表明,该加工方法明显提高了工件的表面质量,降低了工件的表面粗糙度并均化了波纹度。     

磁力研磨工艺提高叶片表面质量的试验研究

目的 提高航空发动机涡轮叶片的服役年限。方法 应用磁力研磨工艺提高涡轮叶片表面质量,包括降低叶片表面粗糙度、去除飞秒激光制孔过程中产生的棱边毛刺以及降低叶片表面残余应力,建立神经网络模型确定最佳工艺参数,在最佳工艺参数下对叶片进行研磨加工。使用JB-8E触针式表面粗糙度测量仪、超景深显微镜和X''Pert Powder残余应力测试分析系统,分别对叶片表面粗糙度、孔口形貌以及叶片表面残余应力进行分析。结果 叶片在最佳工艺参数下完成研磨加工,叶片表面粗糙度从3.08 μm下降到0.19 μm,叶片气膜孔棱边毛刺基本去除,且存在倒圆迹象,研磨后叶片晶格更加致密,受力状态从残余拉应力(324.7 MPa)转变为残余压应力(132.8 MPa)。结论 应用磁力研磨工艺可以有效降低叶片表面粗糙度,去除叶片气膜孔的棱边毛刺,对气膜孔的棱边进行倒圆加工,提高飞秒激光制气膜孔的表面质量,同时还可以将叶片的残余拉应力转化为残余压应力,使得叶片晶格排布更加紧密,在提高叶片强度和耐磨性的同时不会引入新的缺陷,增加叶片的服役寿命。     

聚晶立方氮化硼刀具刃口放电加工工艺研究

通过调整电火花加工的主要放电参数（脉冲宽度和加工电流）,对聚晶立方氮化硼（PCBN）4~进行放电加工,进而对样刀刃口表面进行x射线衍射分析,并在扫描电子显微镜下观察其表层结构及能谱分析。通过对加工后样刀表面变质层主要成分及产生原因的分析,总结了脉冲宽度和加工电流对样刀表面变质层厚度、刃口表面粗糙度影响的关系曲线,为制定精密快速放电加工PCBN刀具的工艺提供了重要依据。     

模具零件线切割加工电参数优化及变质层研究

为提高精冲模使用寿命,对线切割加工参数和线切割零件加工面变质层进行研究。采用正交试验的方法优化线切割加工电参数,提高综合考虑多项工艺指标后的零件加工质量。观察分析了模具零件线切割典型变质层的微观形貌和显微组织;利用X射线衍射仪测量加工零件的变质层残留应力,通过比较得到合适的方法降低残留应力,可为提高精冲模的使用寿命提供理论依据和方法。     

Analytical model to determine the critical feed per edge for ductile-brittle transition in milling process of brittle materials

Brittle materials like glass are considered difficult-to-machine because of their high tendency towards brittle fracture during machining. The technological challenge in machining such brittle materials is to achieve material removal by plastic deformation rather than characteristic brittle fracture. In ductile mode machining, the material is removed predominantly by plastic deformation and any cracks produced due to possible fracture in the cutting zone are prevented from extending into the machined surface. This is achieved by selecting an appropriate cutting tool and suitable machining parameters. In ductile machining by milling process, fracture induced cracks are diverted away from final machined surface by selecting a suitable feed per edge less than a critical threshold value. Hence determination of critical feed per edge is of paramount importance to achieve ductile mode machining by milling process. This paper presents an analytical model based on fracture mechanics principles to predict the critical feed per edge in milling process of glass. The size and orientation of cracks originating from brittle fracture during machining have been quantified by using indentation test results and the critical value of feed per edge has been determined analytically as a function of intrinsic materials properties governing brittle fracture and plastic deformation. Furthermore, an equivalent tool included angle has been suggested for machining operation as against the indenter included angle to correlate the indentation and machining test results with improved degree of accuracy. Experimental results validated the proposed model fairly accurately. It has been established that if the longest cracks oriented in radial direction to the cutting edge trajectory are prevented from reaching the final machined surface by selecting a feed per edge less than or equal to a critical value, a crack-free machined surface can be achieved.     

陶瓷复合装甲的台阶孔及槽加工试验研究

针对陶瓷复合装甲的台阶孔及开槽加工的技术难题,根据其组成材料特性设计了专用烧结金刚石工具,并对其进行了加工试验研究.分析了加工过程中出现的各种表面质量缺陷,并给出了改善表面加工质量的有效方法,确定了合理的工艺流程及工艺参数.试验表明,台阶孔及开槽的加工质量完全满足复合装甲的装配技术要求.     

Precision machining of small holes by the hybrid process of electrochemical removal and grinding

This paper presents a hybrid process of grinding and electrochemical removal for machining of precision small holes with hard-to-machine materials. In the process, a metal rod with coated abrasives as cathode tool rotates at high speed and removes material electrochemically and mechanically for a pre-machined pilot hole. The effects of process parameters on the hole surface quality and dimensional accuracy were demonstrated experimentally. Material removals on grinding and electrochemical machining are well balanced by rationally determining machining voltage, tool rotation speed and feed rate. Precision holes of diameters down to 0.6 mm with sharp edges and without burrs have been produced.     

Punching in industrial wood machining: an alternative production process to drilling

Drilling of wood is besides milling, sawing and grinding one of the most important production processes in industrial furniture manufacturing. For the body assembly and the fixing of fittings, boreholes are essential. They have immediate effect on quality and production costs. The process step drilling limits the output of stationary and throughfeed machines, because the workpieces have to be stopped to create the drillings at a relatively low feed speed. An essentially increased performance cannot be reached by the improvement of conventional drilling devices. The aim of the work presented in this paper is the development of an alternative production process in which blind holes can be punched. Thereby thin-walled, cylinder-shaped tools are pressed into different solid and derived timber workpieces by a simple translative movement. For it special experimental setups have been designed. The new production process opens possibilities for an optimization and acceleration of process cycles in industrial wood machining.     

ATOMISTIC SIMULATION OF NANOSTRUCTURE FOR MACHINING-TENSION PROCESS

利用分子动力学在原子尺度模拟了单晶Cu (111)面纳构件的纳米加工过程和加工后纳构件的拉 伸过程, 分析了纳刻划过程的缺陷行为及加工缺陷对纳构件力学特性的影响. 结 果表明: 在纳刻划过程中, 在针尖的前方和下方形成加工变形区; 当刻划深度 较浅时, 位错仅在表面与亚表面繁殖; 随着刻划深度的增加, 加工后残留的缺 陷数量增加, 纳构件的有序度及首次屈服应力下降; 加工后的纳构件内部, 尤其在针尖退出处有较高的残余应力. 对加工后的纳构件施加拉伸载荷, 由于 存在残留加工缺陷和较高残余应力, 其应力--应变曲线在弹性上升阶段有局部下降; 在塑性阶段, 由于位错繁殖及位错塞积和中间部分原子的迁移重构使应力--应变曲 线呈锯齿状逐渐下降. 纳构件断裂失效前表现为单原子相连的纳 链. 纳构件的有序度随着刻划深度的增加而下降. 在应变为0.8处, 刻划较浅的 纳构件的有序度较首次屈服处的有序度略好.     

小孔内表面磁力研磨加工技术研究进展

磁力研磨加工是提高小孔内表面质量的一种重要光整技术,利用该技术能高效提升小孔类零部件在极端环境下的使役性能。针对小孔内表面的磁力研磨光整加工,按其发展历程对磁力研磨加工技术进行总结,归纳了磁性磨粒研磨、磁针磁力研磨、液体磁性磨具研磨、超声辅助磁力研磨和电解磁力复合研磨等加工方法的技术特点,并分析评述了其局限性。对磁力研磨加工过程中材料去除机理进行了研究,材料主要以微量切削与挤压、塑性变形磨损、腐蚀磨损、电化学磨损等方式去除,材料种类不同,去除机理也不同。其中,硬脆性材料主要以脆性断裂、塑性变形和粉末化的形式去除;塑性材料在经历滑擦阶段、耕犁阶段和材料去除阶段后主要以切屑的形式去除。此外,还对磁力研磨加工过程中的材料去除模型进行了研究,对单颗磁性磨粒材料去除模型和“磁力刷”材料去除模型进行了分析讨论。最后,对磁力研磨加工技术今后的研究发展给出了建议并进行了展望。     

低盐溶液电火花-电解复合加工微小方孔试验

综合电火花加工快速蚀除材料与电解加工溶解重铸层的优势,提出了在低电导率的NaNO3溶液中使用电极逐层往复式铣削加工微小方孔的电火花-电解复合加工方法,并研究了电解液浓度、电压和电容参数对微小方孔加工质量的影响。结果表明:电解液浓度与加工电压对微小方孔加工质量影响较大,电容影响相对较小。选用最优加工参数在100μm厚的321不锈钢片上加工微小方孔,得到的方孔加工质量好、侧壁表面无重铸层,且工具电极相对损耗仅0.05%。     

Tube electrode high-speed electrochemical discharge drilling using low-conductivity salt solution

Film cooling holes are widely used in the aerospace industry, and their fabrication requires high machining speed and accuracy, as well as good surface quality. Tube electrode high-speed electrochemical discharge drilling (TSECDD) is a promising hybrid machining method for the fabrication of film cooling holes in difficult-to-machine superalloys. An electrochemical reaction can occur if a low-conductivity salt solution is used in the drilling. Materials can also be removed at a high speed using electrical discharge machining (EDM). Thus, TSECDD and electrochemical machining (ECM) can be combined into a unique machining process using a low-conductivity salt solution. This machining process achieves both a high machining speed and good surface finish. In this study, the material removal mechanism of TSECDD was studied using a low-conductivity salt solution, and comparisons with high-speed electrical discharge drilling were made. The performance of the process was investigated using salt solutions of various conductivities. The results show that there are different material removal mechanisms in the frontal gap and the lateral gap and that, in the latter, there is a transition from EDM to ECM. Experiments conducted using TSECDD confirm that the use of this process with a low-conductivity salt solution can improve the machining surface and machining efficiency achieved. The results also show that the use of a low-conductivity solution improves the material removal rate, the hole diameter, and the taper angle.