Nontraditional energy-assisted mechanical machining of difficult-to-cut materials and components in aerospace community:a comparative analysis

The aerospace community widely uses difficult-to-cut materials,such as titanium alloys,high-temperature alloys,metal/ceramic/polymer matrix composites,hard and brittle materials,and geometrically complex components,such as thin-walled structures,microchannels,and complex surfaces.Mechanical machining is the main material removal process for the vast majority of aerospace components.However,many problems exist,including severe and rapid tool wear,low machining efficiency,and poor surface integrity.Nontraditional energy-assisted mechanical machining is a hybrid process that uses nontraditional energies(vibration,laser,electricity,etc)to improve the machinability of local materials and decrease the burden of mechanical machining.This provides a feasible and promising method to improve the material removal rate and surface quality,reduce process forces,and prolong tool life.However,systematic reviews of this technology are lacking with respect to the current research status and development direction.This paper reviews the recent progress in the nontraditional energy-assisted mechanical machining of difficult-to-cut materials and components in the aerospace community.In addition,this paper focuses on the processing principles,material responses under nontraditional energy,resultant forces and temperatures,material removal mechanisms,and applications of these processes,including vibration-,laser-,electric-,magnetic-,chemical-,advanced coolant-,and hybrid nontraditional energy-assisted mechanical machining.Finally,a comprehensive summary of the principles,advantages,and limitations of each hybrid process is provided,and future perspectives on forward design,device development,and sustainability of nontraditional energy-assisted mechanical machining processes are discussed.

Field-assisted machining of difficult-to-machine materials

Difficult-to-machine materials (DMMs) are extensively applied in critical fields such as aviation,semiconductor,biomedicine,and other key fields due to their excellent material properties.However,traditional machining technologies often struggle to achieve ultra-precision with DMMs resulting from poor surface quality and low processing efficiency.In recent years,field-assisted machining (FAM) technology has emerged as a new generation of machining technology based on innovative principles such as laser heating,tool vibration,magnetic magnetization,and plasma modification,providing a new solution for improving the machinability of DMMs.This technology not only addresses these limitations of traditional machining methods,but also has become a hot topic of research in the domain of ultra-precision machining of DMMs.Many new methods and principles have been introduced and investigated one after another,yet few studies have presented a comprehensive analysis and summarization.To fill this gap and understand the development trend of FAM,this study provides an important overview of FAM,covering different assisted machining methods,application effects,mechanism analysis,and equipment design.The current deficiencies and future challenges of FAM are summarized to lay the foundation for the further development of multi-field hybrid assisted and intelligent FAM technologies.

Effect of tool geometry on ultraprecision machining of soft-brittle materials:a comprehensive review

Brittle materials are widely used for producing important components in the industry of optics,optoelectronics,and semiconductors.Ultraprecision machining of brittle materials with high surface quality and surface integrity helps improve the functional performance and lifespan of the components.According to their hardness,brittle materials can be roughly divided into hard-brittle and soft-brittle.Although there have been some literature reviews for ultraprecision machining of hard-brittle materials,up to date,very few review papers are available that focus on the processing of soft-brittle materials.Due to the‘soft’and‘brittle’properties,this group of materials has unique machining characteristics.This paper presents a comprehensive overview of recent advances in ultraprecision machining of soft-brittle materials.Critical aspects of machining mechanisms,such as chip formation,surface topography,and subsurface damage for different machining methods,including diamond turning,micro end milling,ultraprecision grinding,and micro/nano burnishing,are compared in terms of tool-workpiece interaction.The effects of tool geometries on the machining characteristics of soft-brittle materials are systematically analyzed,and dominating factors are sorted out.Problems and challenges in the engineering applications are identified,and solutions/guidelines for future R&D are provided.

Combined method of plastic work piece machining based on a pretreatment mechanical down

An analysis of polymer materials behavior under cutting forces load was presented.The analysis was accomplished taking into account the existence and interaction of micro cracks in material.On the basis of modeling representations of a polymeric material behavior at cutting the method of preliminary mechanical destruction a superficial layer of polymeric material was developed.The essence of the method consists in producing micro-cracks in form of blind holes on the upper layer of blanks before turning.The aim of this method is a plastic deformation zones creation under stresses interaction occurring at the adjacent crack apexes.Results of experimental researches of fabric-based laminate turning processing according to the offered method were submitted.The analysis of the received results confirms expediency of application of the given combined method and the decrease of a roughness on the processed surface of fabric-based laminate is testifying about it.

Plasma-enabled electrochemical jet micromachining of chemically inert and passivating material

Electrochemical jet machining(EJM)encounters significant challenges in the microstructuring of chemically inert and passivating materials because an oxide layer is easily formed on the material surface,preventing the progress of electrochemical dissolution.This research demonstrates for the first time a jet-electrolytic plasma micromachining(Jet-EPM)method to overcome this problem.Specifically,an electrolytic plasma is intentionally induced at the jet-material contact area by applying a potential high enough to surmount the surface boundary layer(such as a passive film or gas bubble)and enable material removal.Compared to traditional EJM,introducing plasma in the electrochemical jet system leads to considerable differences in machining performance due to the inclusion of plasma reactions.In this work,the implementation of Jet-EPM for fabricating microstructures in the semiconductor material 4H-SiC is demonstrated,and the machining principle and characteristics of Jet-EPM,including critical parameters and process windows,are comprehensively investigated.Theoretical modeling and experiments have elucidated the mechanisms of plasma ignition/evolution and the corresponding material removal,showing the strong potential of Jet-EPM for micromachining chemically resistant materials.The present study considerably augments the range of materials available for processing by the electrochemical jet technique.

Advances in molecular dynamics simulation of ultra-precision machining of hard and brittle materials

Hard and brittle materials, such as silicon, SiC, and optical glasses, are widely used in aerospace, military, integrated circuit, and other fields because of their excellent physical and chemical properties. However, these materials display poor machinability because of their hard and brittle properties. Damages such as surface micro-crack and subsurface damage often occur during machining of hard and brittle materials. Ultra-precision machining is widely used in processing hard and brittle materials to obtain nanoscale machining quality. However, the theoretical mechanism underlying this method remains unclear. This paper provides a review of present research on the molecular dynamics simulation of ultra-precision machining of hard and brittle materials. The future trends in this field are also discussed.

Experimental Study on Thermal Stress of Concrete with Different Expansive Minerals Using a Temperature Stress Testing Machine

In order to compare the compensation effect of expansive materials with different mineral sources on the temperature stress of concrete,we investigated the temperature stress of concrete when adding calcium sulfoaluminate type expansive materials(CSA)or CaO and calcium sulfoaluminate mixed type expansive materials(HCSA)at different temperatures by temperature-stress testing machine(TSTM)considering the influence of temperature history on the expansion.The experimental results show that the expansion characteristics of the two kinds of expansive materials with different mineral sources significantly vary.When adding expansive materials,the growth rate of compressive stress during the heating stage increases obviously,the maximum compressive stress is higher,while the decline rate of tensile stress in the late cooling stage becomes slow,and finally cracking temperature decreases.It is proved that concrete with HCSA has lower cracking temperatures and better temperature shrinkage compensation effect.Therefore,it is rational to choose HCSA when preparing concrete with high expansion energy to reduce thermal cracking.

Physics-informed deep learning for digital materials

In this work,a physics-informed neural network(PINN)designed specifically for analyzing digital mate-rials is introduced.This proposed machine learning(ML)model can be trained free of ground truth data by adopting the minimum energy criteria as its loss function.Results show that our energy-based PINN reaches similar accuracy as supervised ML models.Adding a hinge loss on the Jacobian can constrain the model to avoid erroneous deformation gradient caused by the nonlinear logarithmic strain.Lastly,we discuss how the strain energy of each material element at each numerical integration point can be calculated parallelly on a GPU.The algorithm is tested on different mesh densities to evaluate its com-putational efficiency which scales linearly with respect to the number of nodes in the system.This work provides a foundation for encoding physical behaviors of digital materials directly into neural networks,enabling label-free learning for the design of next-generation composites.

冻结立井井筒机械化掘进现状及发展趋势

针对我国“富煤贫油少气”的能源赋存结构及煤炭未来一段时间将长期占据能源消耗主导地位的特点,回顾了我国煤炭井工开采领域冻结立井井筒机械化掘进发展历程。钻爆法凿井作为我国立井井筒施工的主要工法,炸药的应用大幅提高了冻结井筒的掘进效率,配套的伞钻打孔、抓岩机装岩、大型井架及设备提升、大模板砌壁等大型机械化设备的应用,大幅提高了井筒成井速度;竖井钻机、反井钻机及竖井掘进机作为特殊地层条件下立井井筒特殊凿井方式,也有各自应用范围。面对我国西部富水弱胶结地层特点及智慧矿山发展趋势,采用冻结+钻爆法施工难以满足千米级弱胶结岩层立井井筒智能化无人化的建设需求,而采用冻结+竖井掘进机钻井是未来超深立井井筒技术发展方向之一。结合国外冻结+竖井掘进机凿井工程案例,针对我国西部富水弱胶结岩层立井井筒建设,提出了冻结+竖井掘进机凿井在冻结壁厚度和强度设计理论、双层钢筋混凝土井壁永久支护、低温环境下竖井掘进机掘进破岩形式以及分级上排渣方式等冻-掘-支-运协同作业方面提出了合理化建议;明确了井壁结构与弱胶结围岩相互作用机理,优化双层井壁结构方法,构建竖井掘进机掘-支-运同步作业模式等,提升井筒建设综合效率,提高信息化水平,推动立井井筒向机械化、绿色化和智能化发展。

偏心拉伸实验的理论分析与实验研究

偏心拉伸实验是一种综合性、研究性的材料力学实验项目。为了增加材料力学实验课程的难度和深度,通过理论分析推导偏心拉伸应力公式,并指出偏心拉伸试样的实际中性层并不再是几何中性层;利用ABAQUS软件模拟了偏心拉伸试样的应力分布;通过自制的一种可以在电子万能试验机上进行偏心拉伸实验的装置并利用电测法测试了试样横截面上各点的应变。结果表明:偏心拉伸实验的理论计算结果、实验结果和模拟结果基本吻合,3种数据之间的偏差较小;而且,应力在试样横截面上几乎呈线性分布,左边受压缩,右边受拉伸,左边的应力最小,右边的应力最大。

金属钼圆基片平面研磨及其表面创成机理研究

目的实现金属钼圆基片高效平坦化加工,获得超光滑表面。方法采用游离磨料对钼圆基片进行平面研磨加工,研究磨料种类及研磨盘转速、研磨压力、研磨时间等工艺参数对研磨效果的影响规律,通过材料去除率(MRR)与表面粗糙度(Ra)的建模分析,对比钼材与高硬脆和高塑性材料,揭示其研磨工艺特性、探究其表面创成机理。结果钼圆基片材料去除快慢和表面形貌受各因素作用的综合影响。CeO_(2)磨料适合钼圆基片的研磨加工,材料去除方式为二体、三体摩擦塑性去除;在研磨过程中,MRR随研磨盘转速、研磨压力的递增而先增大后减小,在研磨盘转速为60 r/min、研磨压力为0.026 MPa条件下MRR达到最大;除磨料因素外,其他工艺因素对表面粗糙度的影响较小;MRR和Ra随加工时间的延长而趋于稳定;使用粒径W1 CeO_(2)磨料在研磨盘转速为60 r/min、研磨压力为0.026 MPa下研磨40 min后,表面粗糙度Ra由46 nm降至9.53 nm,MRR达1.16 mg/min。结论采用游离磨料研磨方法在优化工艺条件下可以有效降低表面粗糙度,获得良好表面。

数控加工机械零件中的专用夹具设计

科技快速发展背景下,数控技术以其诸多优势和特点,被广泛应用于机械零件生产中。不仅优化了传统机械零件设计精度和加工质量,也进一步推动了机械零件数控加工作业发展进程。专用夹具作为数控加工机械零件中的重要组成部分,合理设计专用夹具是实现精细加工的关键所在。主要围绕数控加工机械零件中专用夹具的设计问题进行了一系列讨论。先后概述了数控加工的概念、特点、基本流程以及基本原则,分析了数控加工机械零件中专用夹具设计要点和选择要点,进而以锁芯零件专用夹具设计为例进行了具体案例分析。

微磨料气射流加工技术研究现状与展望

微磨料射流加工技术是一种基于高能流体的磨粒冲蚀磨损加工技术,已广泛应用于难加工材料、复杂三维型面、光滑表面的加工。为进一步提高磨料射流加工过程中的精准控形控性能力,国内外学者开展了诸多基础加工理论与工艺探索等方面的研究工作。本文在概述磨料射流加工技术发展的基础上,全面总结了国内外学者在微磨料气射流加工(MAJM)技术中的微磨料气射流束发散效应及其抑制策略、材料力学性能对材料冲蚀去除模式的影响、材料冲蚀加工过程磨料嵌入抑制策略、微结构冲蚀加工几何特征等方面的主要研究成果,并对微磨料射流加工技术的难点与发展趋势进行了展望。

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。

表面织构电解加工技术研究进展

表面织构在能源、光学、电子、信息技术、生物和摩擦学等领域具有重要应用,其加工工艺是制造技术研究的重要内容。由于所加工表面织构具有无毛刺、翻边等优点,电解加工成为表面织构的重要制造技术方法和技术研究热点,故详细介绍了五种典型表面织构电解加工技术在方法创新、材料去除机制、加工过程建模及加工工艺等方面的研究进展,给出了电解加工表面织构的典型结构和材料,指出提高加工效率和加工自动化程度是未来表面织构电解加工技术的发展趋势。

矿用平车机执行机构的参数化结构优化研究

矿用平车机是在装载机平台上开发的一款新兴机械设备。该设备用于平整火车车厢内堆积的煤炭,有降低人工成本、提高作业效率的作用。为减少矿用平车机执行机构的制造成本,在对其参数化模型进行模拟实际工况下有限元分析的基础上,利用MATLAB结合导重法做轻量化设计。结果表明:轻量化后的执行机构在不超过许用应力的情况下可减重33.19%,可为执行机构的轻量化设计提供参考。

三维编织技术发展现状及其复合材料的应用

为促进三维编织技术的发展,拓宽三维编织复合材料的应用,介绍三维编织成型设备类型并分析不同三维编织机的优缺点,详细阐述三维编织的四向、五向、六向、七向等结构并对比不同编织机的优缺点;从力学性能、损伤机理等方面分析三维编织复合材料的性能,总结三维编织复合材料的应用方向,并展望三维编织技术的发展趋势。指出:选择三维编织机及三维编织结构,需综合考量生产需求、具体应用场景、成本预算和技术能力等因素;三维编织复合材料未来将向技术革新与设备升级、编织结构创新与优化、复合材料性能提升与应用拓展、可持续发展与环境友好性、跨学科合作与创新等方向发展,具有较大的发展潜力与应用前景。

再生纤维原料纺纱相关装备及其技术特点

总结加工再生纤维原料的纺纱装备及其技术特点。简述了废旧纺织品的概况。对废旧纺织品再利用的相关技术进行了梳理,包括物理回收法、化学回收法、热能回收法和机械开松法。重点总结了瑞士立达公司和卓郎公司在2022中国国际纺织机械展览会暨ITMA亚洲展览会上展出的关于加工再生纤维原料的纺纱系统、纺纱装备及其技术特点。认为:科学有序地引导和发展废旧纺织品再利用符合我国法律、法规和发展规划;经机械开松后的废旧纺织品可再次进入纺纱流程,实现其高值化利用。

基于改进YOLOv4的铝材表面缺陷检测方法

针对铝材表面缺陷检测精度不高,容易漏检的问题,提出基于改进YOLOv4的缺陷检测方法。在CSPResblock模块中引入注意力机制SE模块,赋予各个通道相应的权重,加强网络对于重要信息的训练,提升网络的特征提取能力;改进SPP模块,使用不同宽高比的池化核,有利于保留更多的短边信息,提高网络对大宽高比缺陷的检测能力;对PANet结构进行改进,在对应特征层级上拼接输入信息,主要融合主干网络的三层输出,获得更多较浅的特征信息,提升对小目标的检测能力;实验结果表明,改进后的YOLOv4算法在铝材表面缺陷数据集上的精度(mAP)达79.27%,优于其他常见目标检测算法。

磨料流光整加工理论与技术研究进展

在简要阐述挤压磨料流加工技术、磨料水射流抛光技术及软性磨料流加工技术材料去除机理的基础上,介绍了磨料流加工方法的研究进展,总结了上述3种磨料在流光整加工技术抛光过程中,磨粒种类/浓度/粒度、磨料黏度与黏温特性、挤压压力、喷射角度及喷射距离等关键工艺参数对被加工工件材料去除率(材料去除量)和表面粗糙度(表面粗糙度变化)的影响规律,分析了磨料流应用过程中存在的加工均匀性、力学性能及加工精度等技术难题。同时,针对所述技术难题,不仅探讨了相关试验研究,而且提出了一种磨料流与管材液力成形技术相结合的复合工艺,为实现增材制造零件短流程、低排放、低成本的低碳制造目标提供了有效方法。最后,综合归纳了磨料流加工技术在各领域的具体应用,并展望了磨料流光整加工的发展方向。