共查询到20条相似文献,搜索用时 78 毫秒
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用切削力的频数差对切削颤振进行早期预报 总被引:3,自引:1,他引:2
本文提出一种预报切削颤振的新方法,它利用切削力在幅值域内的频数差作预报参数,可以在颤振孕育过程的初期进行预报,预报的及时性好,它对切削过程中力的随机波动不敏感,且切削条件变化对控制门限值无影响,预报的准确性高。 相似文献
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分析和比较磨削与切削过程中颤振孕育的不同特征,提出一种具有自学习的颤振预报方法,以适应各种磨削的工况,通过实验证明这种预报方法能满足磨削颤振预报的及时性和准确性。 相似文献
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在线自寻优控制机床主轴转速的研究 总被引:2,自引:0,他引:2
以机床主轴前后两转切削振动的相位差ψ为寻优参数,对机床主轴转速进行在线自寻优控制,使切削过程总能在稳定区进行。试验结果表明,本文提出的在线自寻优控制机床主轴转速的方法对切削颤振有很好的控制作用,具有良好的生产应用前景。 相似文献
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变速切削系统振动频率的变化特征 总被引:1,自引:0,他引:1
本文主要讨论变速切削系统中颤振频率随机床主轴转速变化的规律。理论分析和试验结果都证明在变速切削中颤振频率随转速呈分段线性锯齿状变化。试验在立式铣床和普通车床上进行。 相似文献
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本文讨论了利用微机对机床颤振进行在线预报控制的机理。介绍了用DDS(Dynamic Data System)方法,在时域内分析机床系统的动态特性。文中重点讨论了通过拾取机床的颤振信号,建立DDS模型(AR或ARMA),进而利用DDS模型判别机床动态稳定性,预测颤振的方法,指出机床发生颤振的条件,根据颤振的条件,用微机对机床进行预报控制。从而实现无颤械切削控制。 相似文献
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切削加工系统的稳定性分析 总被引:3,自引:0,他引:3
本文根据一台数控车床的实际加工过程,建立了切削系统的动力学模型,并导出了切削过程闭环系统的传递函数。这一动力学模型,概括了再生型颤振和振型耦合颤振原理。稳定性分析所用的结构传递函数和动态切削力系数,是根据切削系统解耦的条件,在切削过程中辩识和测量得到的。稳定性分析得到的极限切削宽度值与切削颤振试驻的实验值,可良好地吻合。稳定性极限值的大小与左刃或者右刃切削方式,走刀量以及切削速度等因素有关。文中建立的切削过程动力学模型和稳定性分析方法,可用于预测加工过程的稳定性。 相似文献
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本文研究了切削加工稳定图中相邻两个不稳定叶瓣之间的控制规律。经理论和实验分析给出的规律表明,颤振振幅和切宽的关系在切宽较大时,由右边不稳定叶瓣的左侧控制;而在切宽较小时,由左边不稳定叶瓣的右侧控制。该规律能全面描述机床双频颤振现象和颤振过程主频带移动的原因。 相似文献
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《International journal for numerical methods in engineering》2018,113(9):1488-1506
In this paper, we present a new method for inserting several triangulated surfaces into an existing tetrahedral mesh generated by the meccano method. The result is a conformal mesh where each inserted surface is approximated by a set of faces of the final tetrahedral mesh. First, the tetrahedral mesh is refined around the inserted surfaces to capture their geometric features. Second, each immersed surface is approximated by a set of faces from the tetrahedral mesh. Third, following a novel approach, the nodes of the approximated surfaces are mapped to the corresponding immersed surface. Fourth, we untangle and smooth the mesh by optimizing a regularized shape distortion measure for tetrahedral elements in which we move all the nodes of the mesh, restricting the movement of the edge and surface nodes along the corresponding entity they belong to. The refining process allows approximating the immersed surface for any initial meccano tetrahedral mesh. Moreover, the proposed projection method avoids computational expensive geometric projections. Finally, the applied simultaneous untangling and smoothing process delivers a high‐quality mesh and ensures that the immersed surfaces are interpolated. Several examples are presented to assess the properties of the proposed method. 相似文献
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Standards are the basis for production enterprises to organize production ex-factory inspection trade 《中国标准化(英文版)》2008,25(1):24-25
Standards are the basis for production enterprises to organize production, ex-factory inspection, trade (delivery) and technical exchanges, product certification, quality arbitration and supervision.…… 相似文献
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Steffen Müller-Probandt 《材料科学与工程:中英文B版...》2018,(4):161-177
We associate a variety of innovations with the term "Industry 4.0". The pioneer of many 4.0 modifications forms the basisfor the trend towards the integrated di... 相似文献
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A flow calorimeter for enthalpy increment measurements on condensed gases is presented. A better knowledge of the properties of the liquefied natural gas is needed, and therefore a liquid loop has been designed for our flow calorimeter. The fluid loop in the calorimeter is designed in order to avoid the two-phase region, since two phases would give compositional disturbances in the measurements. The avoidance of the two-phase region is made possible by increasing the pressure of the test fluid after the measurement section, then heating the fluid at super-critical pressure past the critical point. Finally, the fluid is throttled to the low-pressure gas state at the inlet condition of the compressor that circulates the fluid. To perform the pressure increase, a new cryogenic pump has been designed. To evaluate the new equipment, measurements were taken on liquid ethane over the temperature range 146–256 K at pressure between 0.9 and 5.1 MPa. 相似文献
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On November 30, 2007, the China Association for Standardization (CAS) held a press conference at Beijing Diaoyutai State Guest House. Leaders from the China Household Electric Appliance Research Institute, the China Household Electric Appliance Association, and the China Consumers' Association attended and made speeches.…… 相似文献
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Zusammenfassung Bei der Gestaltung von Ernteprozessen — beispielsweise des Prozesses Mähdrusch, Körnertransport und -abnahme — als transportverbundene Fließarbeitsverfahren mit mindestens zwei verschiedenen Arbeitsmitteln gibt es einen großen Optimierungsspielraum. Solche Prozesse sind mehrstufige Bedienungsprozesse mit gemischter Anordnung der Bedienungseinrichtungen. Außerdem besitzen sie stark ausgeprägte räumliche Aspekte. Es wird vor allem gezeigt, welche Merkmale solcher Prozesse in Simulationsmodellen abgebildet sein müssen, welche Zielgrößen in Abhängigkeit von welchen Einflußgrößen unter Berücksichtigung welcher Prozeßbedingungen ermittelt werden sollten und wie der Bewertungsprozeß zur Ermittlung der gewünschten Informationen gestaltet werden muß. 相似文献
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Janet Lang 《Materials and Manufacturing Processes》2017,32(7-8):857-866
ABSTRACTThe production of ferrous metal increased during the Roman Late Republican period, Principate and Empire. The direct bloomery process was used to extract the metal from its ores using slag-tapping and slag-pit furnaces. The fuel was charcoal and an air blast was introduced by bellows-operated tuyères. Iron formed as a bloom, often as a spongy mass of metal, which contained impurities from the smelting process, including unreacted ore, fuel, slag and fragments from the furnace walls, while the metal was often inhomogeneous with varied carbon contents. Blooms were either smithed directly into bars or ingots or they were broken up, which also allowed the removal of gross impurities and a selection of pieces with similar properties to be made. These could then be forge-welded together and formed into characteristically shaped ingots. Making steel in the furnace seems to have been achieved: it depended on the ore and the furnace and conditions within it. Surface carburization was also carried out. Iron and steel were used extensively in construction and for tools and weapons. Fire welding was often used to add pieces of steel to make the edges of tools and weapons, which could be heat-treated by quenching to harden them. 相似文献
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C. Qihong W. Zhan‐Wen J. Yi J. Yehua L. Fei F. Hanguang 《Materialwissenschaft und Werkstofftechnik》2014,45(7):582-590
In the present study a high‐boron high speed steel (HSS) roll material was designed. Many expensive alloy elements have been substituted by cheap boron alloy, and high‐boron high speed steel roll has been manufactured by centrifugal casting method. The microstructures, mechanical properties and wear resistance of centrifugal casting high‐boron high speed steel roll have been investigated by optical microscopy (OM), scanning electron microscopy (SEM), and X‐ray diffraction (XRD) analysis, hardness test, impact test and wear test. The results indicated that the solidification microstructures of high‐boron high speed steel roll consisted of M2(B,C), (W,Mo)2(B,C), M3(B,C), M23(B,C)6 type borocarbides and martensite, a small amount of retained austenite. Borocarbides were continuously distributed over the grain boundary. After quenching from 1050 °C, local broken network appeared in partial borocarbides, and fine secondary borocarbide precipitated from the matrix. After tempering from 525 °C, the amount of precipitated borocarbide increased significantly. After heat treatment, the hardness of high‐boron high speed steel roll excelled 60 HRC, and its impact toughness excelled 8.0 J/cm2. The single groove steel rolling amount of high‐boron high speed steel rolls increases by 500% than that of bainite cast iron roll, when the rolls are used in K1 mill housing of bar mill. 相似文献
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Dimiter Hadjistamov 《材料科学与工程:中英文B版...》2019,(2):56-65
The definition of the thixotropy is a decrease in viscosity with time in shear and a subsequent recovery of viscosity after the shear deformation is removed.We ... 相似文献