卧式摆头加工中心动横梁热固耦合特性研究

以五轴加工中心为代表的高端数控机床是国家重要战略物资,具有很高的综合性能需求。基于热固耦合分析方法,针对卧式加工中心中承载摆角铣头的动横梁进行结构特性研究。建立焊接式动横梁的实体单元热固耦合有限元模型并进行仿真,分析动横梁在结构静力载荷和热载荷综合作用下的变形和应力。采用多元回归拟合方法,研究不同结构参数对动横梁结构特性的影响规律,并根据影响规律对结构参数进行优化调整。在质量基本不变的情况下,优化后的动横梁焊接结构的Y轴最大位移减少了10.489%,最大应力减少了41.06%。

关节角参数化结合接近矢量可行方向的五自由度机械臂逆运动学求解

五自由度的机械臂无法达到任意位姿,采用传统的位姿描述方式进行逆运动学求解时,极易产生无解的情况。文中以一种适用于清洁、喷涂、焊接等作业的、由4个旋转关节和1个移动关节构成的五自由度机械臂为例,建立运动学模型并进行逆运动学分析,在此基础上,提出一种关节角参数化结合接近矢量可行方向的逆运动学求解方法。该方法基于自由度约束的末端位姿描述,先通过关节角参数化将末端执行器的运动空间由三维降为二维,再采用几何法分析末端执行器在不同目标位置(远端、中间端、近端)时的接近矢量的可行方向,从而避免参数盲目取值,确保运动学逆解的存在,然后根据运动连续性和各关节的运动范围从中筛选出最优解。路径规划仿真结果表明,实际路径与规划路径非常吻合,关节运动平稳,证明了所提方法的可行性和准确性。文中研究的五自由度机械臂具有一定的代表性,逆运动学求解方法计算复杂度低,求解过程较为简便,求解思路可为欠自由度机械臂的逆运动学求解提供借鉴。

基于回差优化的RV减速器摆线轮齿廓修形

针对RV减速器回差的优化问题,基于RV减速器的二级结构和扭矩传递路径,从零件误差角度对回差影响因素进行分类.以工业机器人用RV-40E型减速器为实例,计算了各回差因素的敏感度和权重.其中,摆线轮齿廓修形具有较大的敏感度.为减小摆线轮修形引起的齿侧间隙,提出了基于形变量补偿的摆线轮齿廓修形方法,该方法在等距-移距组合修形基础上,将针齿在额定负载下的接触形变量补偿回摆线轮的齿廓中,在不改变摆线针轮径向间隙的基础上实现RV减速器回差的优化.对RV减速器样机进行虚拟样机仿真和试验验证.结果表明:回差优化RV的回差值为0. 66',传统修形RV的回差值为1. 3',与虚拟样机仿真结果基本一致,该基于回差优化的摆线轮修形方法可显著降低RV减速器回差.

基于优化承载能力的RV减速器摆线齿轮齿廓的等距-移距修形

结合传统等距修形方法和移距修形方法,提出了一种基于优化承载能力的摆线轮齿廓的新型等距移距组合修形方法。以工业机器人RV-40E减速器的摆线针轮为例,对其传动进行了力学分析,以最优承载能力为目标建立了摆线轮修形量搜寻数学模型,并采用格点法进行了优化,最终通过数值求解获得了等距移距修形的摆线轮齿廓曲线。设计了摆线轮加工工艺,分别加工制造了等距移距修形的摆线轮和作为对比验证的传统拟合转角修形摆线轮,并分别组装出RV减速器样机进行性能测试。试验结果表明:装有该等距移距修形摆线轮的RV减速器的传动效率高达85%,相比于装有传统拟合转角修形摆线轮的RV减速器,该新型RV减速器在重载情况下的噪声和温升均显著降低,承载能力得到了明显提高。

碳纤维锻造复合材料的摩擦行为

采用模压成型工艺制备了环氧树脂基碳纤维锻造复合材料,测试了该材料在干摩擦和水润滑摩擦条件下的不同摩擦行为,研究了两种摩擦条件下摩擦系数的变化特性差异,并进一步分析了微观磨损机理.结果表明:两种不同摩擦条件下锻造复合材料的摩擦系数展现出不同的变化趋势,干摩擦条件下摩擦系数经历了初始稳定期、转移膜形成期和稳定期3个阶段,期间形成的含铁转移膜具有自润滑效应;水润滑摩擦条件下由水润滑膜主导复合材料的摩擦行为,摩擦过程能快速进入稳定期,摩擦系数和磨损率较小,磨损率保持较为稳定;锻造复合材料在两种摩擦条件下的摩擦系数减少率基本相同.

Characteristics and Formation Mechanism for Stainless Steel Fiber with Periodic Micro-fins

Metal fibers have been widely used in many industrial applications due to their unique advantages. In certain applications, such as catalyst supports or orthopedic implants, a rough surface or tiny outshoots on the surface of metal fibers to increase surface area are needed. However, it has not been concerned about the surface morphologies of metal fiber in the current research of metal fiber manufacturing. In this paper, a special multi-tooth tool composed of a row of triangular tiny teeth is designed. The entire cutting layer of multi-tooth tool bifurcates into several thin cutting layers due to tiny teeth involved in cutting. As a result, several stainless steel fibers with periodic micro-fins are produced simultaneously. Morphology of periodic micro-fins is found to be diverse and can be classified into three categories： unilateral plane, unilateral tapering and bilateral. There are two forming mechanisms for the micro-fins. One is that periodic burrs remained on the free side of cutting layer of a tiny tooth create micro-fins of stainless steel fiber produced by the next neighboring tiny tooth; the other is that the connections between two fibers stuck together come to be micro-fins if the two fibers are finally detached. Influence of cutting conditions on formation of micro-fins is investigated. Experimental results show that cutting depth has no significant effect on micro-fin formation, high cutting speed is conducive to micro-fin formation, and feed should be between 0.12 mm/r and 0.2 mm/r to reliably obtain stainless steel fiber with micro-fins. This research presents a new pattern of stainless steel fiber characterized by periodic micro-fins formed on the edge of fiber and its manufacturing method.

激光加工平面型微超级电容器的研究进展与发展趋势

可穿戴和便携式电子设备朝"轻薄化"与"小型化"方向的快速发展,极大地刺激了现代社会对高能量/功率密度、轻量便携化、柔性化储能器件的强烈需求。平面型微超级电容器(In-plane micro-supercapacitors, IPMSC)作为一种新型的微电源储能器件,以其超薄厚度、高功率密度和长循环寿命等优点被认为是集成电子器件重要的储能器件而备受关注。但是,随着IPMSC加工技术不断朝着高效、高精度和低成本等方向发展,常用的加工技术已难以满足其要求,操作更易、可扩展性更强、精度较高和成本更低的激光加工技术成为了目前IPMSC加工技术的研究热点。基于此,对不同类型IPMSC的工作原理及其电化学性能进行了总结,从激光还原、激光诱导、激光刻蚀和激光烧结四方面着手详细介绍了激光加工IPMSC的类型及加工工艺,重点综述了目前国内外关于激光加工IPMSC在机械性能和电化学性能等方面的研究进展情况,概括了用于IPMSC电解质的特性及其挑战,并在综合探讨激光加工IPMSC所面临的技术挑战基础上,对其在可穿戴和便携式电子设备中的应用前景进行了展望。

脱附性医用高频电刀的研究现状及发展趋势

医用高频电刀通过刀头尖端电弧放电并产生热量完成组织的切割和止血工作,是外科手术中的重要工具。在手术过程中,高频电刀温度过高会使血液和软组织脱水结痂甚至炭化,粘连并包覆刀头,进而对手术过程和医疗效果产生严重影响。为能够有效解决医用高频电刀表面的生物组织粘连问题,国内外诸多学者开展了电刀表面的脱附性研究,具有明显疏血、散热降温、抗组织粘附等效果的仿生脱附性医用高频电刀已成为该领域的研究热点和重要发展方向。按照现有脱附性医用高频电刀的结构特点进行归纳分类并详细介绍其研究和应用现状,着重介绍和分析仿生高频电刀的动植物脱附模型,总结国内外关于高频电刀表面脱附结构或涂层的制造方法,分析讨论目前脱附性医用高频电刀所存在的问题,最后对其未来的发展趋势进行展望。

激光直写制造石墨烯基柔性电子器件的研究进展

柔性电子器件相对于传统电子器件,拥有独特的柔性和延展性,能够在一定程度上适应不同的工作环境,满足设备的形变需求。石墨烯是开发柔性电子器件的理想材料。然而,传统的石墨烯加工技术大多涉及高温和化学溶剂,存在着成本高,工艺线路复杂和环境污染等问题,并不适合未来产业发展。激光直写(Laser direct writing,LDW)技术具有加工速度快,扫描面积大和空间分辨率高等优点,且无需掩模和后处理,在现代工业中广泛应用。最新研究表明,激光直写技术可以从氧化石墨烯、多种聚合物甚至天然材料中衍生出石墨烯,这无疑进一步提升了石墨烯基柔性电子器件的应用潜力。本文对现有激光直写技术制备石墨烯的前驱体进行了归纳分类,并详细介绍了相应的演变过程、加工原理及辅助加工设备,总结了基底转印、表面应变结构、剪纸拓扑结构这三种常见的柔性化制造策略,并重点阐述了其在超级电容器、传感器、纳米发电机和致动器等石墨烯基柔性电子器件中的最新应用,最后对其发展趋势及挑战进行讨论。

平板铝热管微沟槽吸液芯的制备及毛细性能研究

采用犁切-挤压(P-E)和表面化学加工相结合的方法制备出一种新型的铝沟槽吸液芯结构,通过毛细上升红外测试方法对其毛细性能进行测试表征,研究不同的CuCl_2溶液浓度和浸泡时间对吸液芯结构毛细性能的影响。研究结果表明,化学加工后的铝沟槽吸液芯的毛细性能显著提高,其最大毛细上升高度可达49.3 mm,相比于未经化学加工的犁切沟槽,其毛细上升高度提高约79.3%;当CuCl_2溶液浓度超过1mol/L时,浸泡时间和溶液浓度对铝沟槽吸液芯的毛细压力影响较小。该方法能够简单、有效的提高铝沟槽吸液芯的毛细性能,为平板铝热管吸液芯的制备提供了一种新手段。

One-step laser induced conversion of a gelatin-coated polyimide film into graphene:Tunable morphology,surface wettability and microsupercapacitor applications

Latest advances have witnessed the laser induction process on polyimide(PI)films for the formation of porous graphene.Herein,a fully converted graphene film was prepared by Nd:YAG laser scribing a gelatin coated PI film.It was found that the gelatin played the role of"shield"well in absorbing intense laser impact and benefit for the surface morphology modulation.Laser treatment lower than a critical fluence point of~4.00 J mm^(-2) contributed to a crater-like surface morphology due to the dispersed nature of Nd:YAG laser beam.By tuning laser fluence above the threshold,carbonized surface turned into continuous morphology.A fluid dynamics process accompanied by outgassing occurred during the carbonization,and the surface morphology gradually varied from stretched droplets to porous strips and finally to amorphous porous structures.The morphology evolution in combination with surface chemistry is responsible for the significant wettability transition from superhydrophobic to superhydrophilic,and a Janus superhydrophobic/superhydrophilic surface wettability was achieved under a laser fluence of~8.00 J mm^(-2).Eventually,microsupercapacitors(MSCs)were fabricated to show the great potential of our prepared graphene in flexible electronics.

Controlling the laser induction and cutting process on polyimide films for kirigami-inspired supercapacitor applications

The recently emerging laser-induced graphene(LIG)technology,with one-step processing and designable features,has been widely used in the fabrication of wearable/portable electronics.Herein,by taking inspiration from kirigami,we designed a stretchable supercapacitor(SC)step by step through controlling laser induction and cutting process on the polyimide(PI)film,with the use of one single CO_(2) laser source.Firstly,the carbonized basic geometric units of lines were produced on PI films to investigate the processing-structure relationships.Then,the complex photothermal conversion and heat transfer progress involved in the carbonized process were simulated by a photothermal model.Both experimental and theoretical results suggested that the laser power,scan rate and focus condition have great influence on the size,shape and morphology of the carbonized lines.Finally,we optimized the parameters of laser induction and cutting process to fabricate the kirigami-inspired SCs with reliable electrochemical properties and editable mechanical flexibility,showing great potential in the field of flexible electronics.

An easy-to-implement method for fabricating superhydrophobic surfaces inspired by taro leaf

An easy-to-implement method by which to fabricate superhydrophobic surfaces inspired taro leaf was successfully applied on316 L stainless steel via combining nanosecond laser(NL)processing and spin-coating techniques.The laser-textured surface composed of microscale frameworks and central bumps was fabricated by NL processing based on properly designed biomimetic patterns,and a layer of nanoscale carbon black/polydimethylsiloxane(CB/PDMS)particles was covered on it by spin-coating.The effect of pattern parameters(i.e.,the inscribed circle radius of framework and the radius of central bump)on wettability of biomimetic surface was investigated.All as-prepared biomimetic surfaces with micro-nano hierarchical structures showed excellent superhydrophobicity with the water contact angle of~155°and contact angle hysteresis of~2°.By comparing the untreated surface,the wetting behavior and evaporation mode of the biomimetic surface occurred an obvious transformation.Meanwhile,experiments indicated that the biomimetic surface not only had liquid-repelling and self-cleaning functions,but also maintained remarkable mechanical robustness and superhydrophobic durability.The method is efficient for fabricating biomimetic superhydrophobic surfaces applied to liquid-repelling,evaporation-transforming and self-cleaning fields.

Investigation on forward and backward transfer process during carbon fiber/epoxy composites dry-sliding against iron alloy

Carbon fiber reinforced polymer(CFRP)composites with high load-bearing capacity are currently ideal materials in tribological load systems.One of the unique features during the friction process of CFRP/metal is the in-situ formation of an ultrathin and uniform transfer film on the metal surface,and the related initial/transfer mechanism is very important but still unclear.Recent studies mainly focus on the one-way transfer process of CFRP to the metal surface,that is,forward transfer;whereas another easily overlooked issue is that the metal material also transfers backward to the CFRP surface.Herein,we firstly prepared carbon fiber/epoxy resin composites(CF/EP)by the hot-pressing method and then carried out friction tests with iron alloy as the control material.The underlying mechanism of the forward/backward transfer process is revealed by controlling the morphological evolution and iron content of the transfer film on worn CF/EP.According to the variation law of friction coefficient with time,the interfacial friction is divided into three different stages,among which the behaviours of“micro-convex contact”and“epoxy exfoliation”occur throughout the whole procedure.We believe this work could provide a meaningful reference for studying the friction behaviour and mechanism,especially the forward and backward transfer between composites/metals,and further broaden its emerging applications in future energy,aerospace and rail transportation.

Fabrication of electrospun bilayer separators for lithium-sulfur batteries:A surface and structure dual modification strategy

The severe shuttle effect problem of soluble polysulfides greatly hinders the development of long-life lithium-sulfur(Li-S)batteries,which can be improved by separator modification.This study develops a bilayer separator based on an effective surface and structure dual modification strategy.This bilayer separator(named as TCNFs/SPNFs)is constructed by the integration of a carbon-based nanofiber layer(surface modification layer)with a polymer-based nanofiber layer(structure modification layer)through a facile electrospinning process.The excellent electrolyte wettability of the nanofibers accelerates lithium-ion migration,while the good electronic conductivity of the carbon layer facilitates fast electron conduction.The TiO_(2)and SiO_(2)nanoparticles embedded in the separator provide abundant active sites for immobilizing the polysulfides.Owing to these synergistic effects,this multi-functional separator helps inhibit the shuttling problem and thus enhances the active sulfur utilization.The as-prepared battery with the TCNFs/SPNFs separator delivers significantly enhanced the electrochemical performances,producing a low capacity decay rate of 0.061%per cycle at 1 C over 1000 cycles and an admirable rate capacity of 886.7 mAh g^(-1)at 2 C.Even with a high sulfur loading of 4.8 mg cm^(-2),a remarkable areal capacity of 6.0 mAh cm^(-2)is attained.This work is believed to provide a promising strategy to develop novel separators for high-performance Li-S batteries.