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表面微沟槽等结构能够限制航空器壁面低速区小涡流生成和猝发的相关雷诺应力,从而降低摩擦阻力,而且该方法简单易行、不需额外增加重量,成为航空器减阻的主要途径之一。概述了表面微结构减阻性能尺度效应的研究进展,表明微结构无量纲尺寸在15左右时减阻性能最佳,减阻率为8%左右;着重综述了简单形状微结构、仿生微结构以及大面积微结构等减阻微结构去除、压印以及滚压等制造技术的研究现状,简析了目前仿生减阻微结构制造技术存在的不足;在此基础上,对仿生减阻微结构制造技术的未来发展和应用进行了展望。 相似文献
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沟槽微结构减阻与疏水表面减阻是两种有效的水下减阻技术。将两种典型的减阻技术进行联合协同,在聚对苯二甲酸乙二醇酯-1,4-环己烷二甲醇酯(PETG)基底表面采用激光微刻方法构筑微米级沟槽结构,采用二步喷涂法先后在微沟槽表面覆盖环氧树脂层与改性的纳米SiO2颗粒,从而实现沟槽型微纳复合结构表面的制备。利用接触角测量仪、体视显微镜、拖曳式摩擦阻力测试设备对复合结构表面的润湿性、水下气膜状态及水下减阻性能进行表征。结果表明,沟槽型微纳复合结构表面为超疏水表面,液滴在该表面处于“Cassie-Baxter”润湿状态;在水下,复合结构表面具有束缚大尺寸气膜的能力,气膜驻留于表面沟槽之中且促使了表面的水下减阻效果的产生;对比单纯的沟槽微结构表面与喷涂SiO2颗粒光滑表面,制得的沟槽型复合结构表面在沿垂直于沟槽方向运动时最大减阻率可达20.82%,同时表面气膜的稳定性也最佳。 相似文献
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鲨鱼、海豚等海洋生物的表皮结构具有防污功能,猪笼草的口缘区具有液膜单向传递特征,这些表面结构形貌可为船舶涂层的防污和减阻设计提供重要依据。根据鲨鱼皮表面肋条状结构、猪笼草口缘区单向沟槽和弧形结构,设计简化单向V型沟槽微结构形貌,并结合CFD模拟计算分析V型沟槽减阻性能,确定了仿生微结构的形貌及尺寸。利用皮秒激光刻蚀技术,在铝合金基材表面刻蚀微结构形貌模板,然后在未完全固化的防污涂层表面压印,通过对软/硬模板、固化时间、压印压强等工艺条件参数的考察及优化,制备出较大尺寸的仿生微结构表面涂层。使用三维形貌测试仪、接触角测试仪等表征仿生微结构涂层表面,并进行多海域实海浸泡性能实验。结果显示,该仿生涂层表面微沟槽间距为90.8 μm,深度为60.3 μm,其表面接触角为121.7°,微结构形貌均匀,具有良好的实海防污性能。 相似文献
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高殿荣|赵建华|张作超 《工程力学》2013,30(4):423-428
目前液体静压导轨的导轨面内一般设计成对称单行、若干列油腔。油腔的数目(即列数)是液体静压导轨设计中的关键,对导轨的动态、静态性能都有着较大的影响。以液体静压导轨的单一导轨面为研究对象,分别作用垂直和倾覆载荷,推导了导轨的承载能力、静刚度与油腔数目的数学关系式,并进行了相应的分析。以工程中的滑板系统为例,滑板导轨面内分别对称设计单行,2列~6列油腔的五种方案。以滑板的承载能力、静刚度为性能依据,对五种方案进行对比分析,结果发现设计成单行、3列油腔时滑板的性能最佳。 相似文献
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《中国新技术新产品》2020,(5)
在对零件加工进行研究的过程中,机床的动静态分析是主要的分析对象,机床的切削能力反应了机床的加工能力,不同的误差对机床的影响也不同,产生的精度影响也不同,误差仿真技术可以有效发现机床的误差源。动态性能会影响高精密机床的制造加工精度。该文分析了五轴精密加工机床的动态性能、机床的RTCP功能、影响机床加工精度的因素和机床误差的产生,同时对误差的影响因素进行了分析,通过减小机床的误差,保证机床的动态性能能够满足加工需求。 相似文献
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提出了从改善结构设计,采用新材料的角度出发解决困扰我国数控机床加工精度的难题。在对纤维增强树脂混凝土作为机床基础件的国内外研究现状分析的基础上,提出基于拓扑优化的方法、结合数控机床工作的环境条件,并考虑材料自身力学本构关系来对纤维增强树脂混凝土机床基础件进行优化设计。最后给出了具体解决策略和思路。 相似文献
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Small machine tools have the inevitable drawback of low structural stiffness caused by a low load-carrying capacity of bearing components. Therefore, mass reduction of the components is advantageous to ensure high performance of the machine tools. In this study, a small table-top machine tool structure was designed and fabricated by using carbon/epoxy composites and resin concrete to reduce the weight of the structure, and enhance the structural stiffness and damping capacity. To determine the specifications of the composite materials finite element analyses and vibration tests were carried out. Several machine tool components were fabricated and assembled using mechanical joining and adhesive bonding. Our results showed that the re-designed structure was 36.8% lighter, and the structural stiffness was increased by 16% with higher loss factors (2.82–3.64%). 相似文献
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切削性能是评价数控机床好坏的重要指标之一,在结构设计阶段必须加以考虑。以提高实验室自主研发的立卧转换四轴联动数控机床的切削性能为目的,研究基于动力学特性与切削特性耦合的机床结构设计优化方法。首先结合切削加工中的颤振稳定域理论,通过实验获取机床刀尖频响函数和切削力系数,预测切削加工时的三维颤振稳定域图(主轴转速-切宽-切深)及颤振频率图(主轴转速-切宽-频率)。其次采用实验模态技术对整机进行结构动力学测试及分析,在获取可视化振型的基础上,分析引起机床发生颤振,并导致切削性能降低的结构设计上的缺陷。在此基础上,改进主轴头结构并比较刀尖频响函数,结果表明系统动刚度约增加28.2%,机床抵抗切削颤振的能力得到明显加强。 相似文献
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In this paper, sandwich structures for micro-EDM machines are optimized by using parametric study varying composite geometries and parameters like stacking sequence, thickness and rib geometry. The structures are composed of fibre reinforced composites for skin material and resin concrete and PVC foam (Closed cell, Divinycell) for core materials. Column structure was designed by a beam with cruciform rib and performance indices such as static bending stiffness (EI) and specific bending stiffness (EI/ρ) for dynamic stability are examined by controlling the thickness and stacking sequence of composites. For the machine tool bed, which usually has a plate shape, was designed to have high stiffness in two directions at the same time controlling stacking sequence and rib geometry; that is, rib thickness and number of ribs. The sensitivity of design parameters like rib thickness and composite skin thickness was examined and the optimal condition for high stiffness structure was suggested. Finite element analysis was also performed to verify the static and dynamic robustness of the machine structure. L-shaped joint for combining bed and column of the micro-EDM machine was proposed and fabricated using adhesive bonding. The dynamic performance such as damping characteristics was investigated by vibration tests. From the results optimal configuration and materials for high precision micro-EDM machines are proposed. 相似文献
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介绍了大力值标准测力机中使用的一种新型静压润滑原理的工作缸塞系统。由于油缸不转动,其有效长度得以减少,从而使工作油缸和活塞的超精加工成为现实。这种带有高压密封和零压槽的缸塞结构,还有助于消除工作油压控制的波动而造成的力值波动,从而可以改善液压式标准测力机的计量性能。实验表明,使用静压缸塞系统的20MN基准测力机,其力值不确定度优于0.01%,而灵敏阀优于0.001%。 相似文献
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S. Jesudass Thomas 《Materials and Manufacturing Processes》2018,33(6):683-694
Recent researches in the field of dry machining have indicated that surface texture has the potential to influence tribological conditions. Researchers have studied the application of controlled surface microtextures on cutting tool surfaces to improve machining performance by changing the tribological conditions at the interfaces of tool–chip and tool–work piece. An experiment to study the performance of the microtextured high-speed steel cutting implement within the machining of steel and aluminum samples was performed. Surface textures were introduced using Rockwell hardness tester, Vickers hardness tester, and by scratching with diamond dresser on the face of single point cutting tool. Machining in dry conditions was applied on mild steel (EN3B) and aluminum (AA 6351) samples using lathe machine with microtextured and traditional cutting tool for the constant range of feed, depth of cut, and for varying range of cutting speeds. Measurement of cutting force, cutting temperature, and surface roughness of the work surfaces after machining were made. The results showed reduction in cutting forces and cutting temperature with textured tools in comparison with those of the untextured tool. Chips collected from different samples were studied under a microscope and the results showed that textures created on the tool surface by various methods exhibited variations in chip formation. Cutting tools without texture and with texture were comparatively studied and the outcomes of the experimental study are presented in this paper. 相似文献
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Arunramnath R Thyla P.R Mahendrakumar N Ramesh M Aravind Siddeshwaran 《Materials and Manufacturing Processes》2019,34(5):530-543
Epoxy granite composites are identified and recognized as better materials for machine tool applications due to inherent damping properties. However, end milling of these composites has not been explored much. Milling of epoxy granite composites presents a number of problems, namely, cutting forces and surface roughness appear during machining. This research work focuses on end milling of epoxy granite composite specimens using high-speed steel end mill cutter by varying the cutting conditions such as spindle speed and feed with a uniform depth of cut and selection of optimal machining parameters. The experimental runs of 27 different trials were carried out and three different attributes such as thrust force, tangential force, and surface roughness were analyzed. This research work presents a sequential procedure for machining parameters selection. Selection of optimal machining parameters is done on the basis of Technique for Order Preference by Similarity to Ideal Solution (TOPSIS) method. 相似文献
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Jung Do Suh Dai Gil Lee 《International Journal of Mechanics and Materials in Design》2008,4(2):113-121
To maximize the productivity of precision products such as molds and dies, machine tools should be operated at high speeds
without vibration. As the operation speeds of machine tools are increased, the vibration problem has become a major constraint
of manufacturing of precision products. The two important functional requirements of machine tool bed for precision machine
tools are high structural stiffness and high damping, which cannot be satisfied simultaneously if conventional metallic materials
are used for bed structure because conventional high stiffness metals have low damping and vice versa. This paper presents
the application of hybrid polymer concrete for precision machine tool beds. The hybrid polymer concrete bed composed of welded
steel structure faces and polymer concrete core was designed and manufactured for a high-speed gantry type milling machine
through static and dynamic analyses using finite element method. The developed hybrid machine tool bed showed good damping
characteristics over wide range of frequency (η = 2.93–5.69%) and was stable during high speed machining process when the spindle angular speed and acceleration of slide
were 35,000 rpm and 30 m/s2, respectively. 相似文献
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伺服进给系统的机电耦合特性直接影响数控机床的加工精度,单独针对伺服系统或机械系统建立的模型不足以准确分析系统参数对机床整机加工精度的影响。因此,综合考虑机床伺服系统与机械结构之间的耦合关系,建立伺服进给系统机电耦合动力学模型具有重要意义。首先,为保证伺服进给系统建模精度,利用状态空间法建立了机床机电耦合状态空间方程。其次,建立了伺服进给系统机电耦合Simulink模型,在此基础上采用复合控制提高系统的响应速度和加工精度。随后,利用多体动力学软件建立机床进给系统的刚柔耦合动力学模型,添加摩擦、阻尼等非线性因素,并导入Simulink与伺服系统建立耦合关系。最终,建立了卧式加工中心伺服进给系统的刚柔-机电耦合仿真加工平台,通过模拟机床加工轨迹以验证机电耦合状态空间模型的可靠性。结果表明:该状态空间模型能准确描述系统内部参数和系统输入输出的耦合关系;采用复合控制结构能有效提高系统的响应速度和加工精度。研究结果为数控机床的仿真建模和提高加工精度提供理论依据,为机床机电系统的设计提供有效指导。 相似文献
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采用雷诺平均N—S方程和RNG κ-ε湍流模型计算V型沟槽面的湍流边界层流动和黏性阻力,通过改变来流速度大小和沟槽面布置位置,研究了雷诺数对沟槽减阻特性的影响规律。计算结果表明,来流速度对沟槽减阻率的影响很大,对于一种尺度的V型沟槽,存在着一个具有较好减阻效果的来流速度范围,最大减阻率可迭8.6%;沟槽面在沿来流方向上的布置位置对其减阻效果的影响则非常小。 相似文献