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《振动与冲击》2020,(18)
针对大型吊装多体系统在回转作业时的刚柔耦合动力学行为,开展了简化模型构建和动态响应分析。利用等效弹簧质量阻尼系统描述吊臂臂头弹性振动,利用空间悬吊系统模拟吊物空间摆动;以浮动坐标系对系统各部件开展运动学描述,基于拉格朗日方程,采用递推列式推导并建立了吊装多体系统的等效简化分析模型,并给出相应数值计算方法。针对某大型轮式起重机开展了仿真分析,通过与实测数据对比分析表明,简化模型能较好地评价柔性吊装多体系统的非线性动力学行为;对柔性臂架振动频谱分析表明,在轻载长绳状态下,吊臂振动幅值受吊物偏摆激励和自身惯性激励的共同影响,但在重载短绳状态下,响应幅值主要取决于吊物偏摆激励,且系统刚柔耦合效应明显增强。 相似文献
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为了解决船舶耦合激励下船用起重机柔性减摆控制效果差的问题,优化设计了一款新型伸缩套管式刚性减摆装置,并研究吊重的低频振动特性,建立了船舶-起重机-伸缩套管防摆装置的三维动力学模型,并通过试验验证了该模型的准确性。通过动力学仿真分析得出套管伸缩量、阻尼器参数及船舶激励对吊重摆动的影响规律,仿真结果表明该三维动力学模型能真实模拟防摆装置的减摆特性,吊重摆动的面内角和面外角分别减小了70%和90%,研究结果对进一步探究机械式防摆装置的防摆机理和结构设计具有重要意义。 相似文献
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为了抵消伴随型非线性系统中的非线性项,可以设计控制器对非线性系统精确线性化.通常由于系统中存在外界不确定性因素导致系统模型的不确定,而不能直接设计控制器.利用"RBF神经网络能以任意精度逼近连续函数"的原理,对系统模型中的不确定项进行自适应辨识,并将辨识结果提供给控制器,从而实现伴随型非线性系统的神经网络自适应补偿控制.将控制器应用于起重机吊重摆角子系统,对摆角进行控制.实验结果表明:吊重摆角及其角速度约在5s后,得到了很好的控制,并且控制器对系统模型的不确定项的逼近误差约在5s时达到0;控制器对系统的不确定性因素和系统参数变化均具有很强的鲁棒性. 相似文献
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针对起重机吊重摆动问题,着重探讨了吊重垂直运动对摆振的影响,在允许的假设条件下建立了起重机吊重摆动的数学模型,用坐标变换把起重机微分方程转化为Hill方程标准形式,通过研究Hill方程找出起重机吊重做减幅摆动的条件。最后引入参数平面,绘制Hill方程稳定图,即起重机吊重做减幅摆动的图示。结果表明:通过控制摆长实现起重机吊重的消摆需要综合考虑初始摆长、摆长的变化幅度和变化周期这三个参数,由这三个参数结合引入的参数平面求得一个坐标点,当这个点落在参数平面的减幅振动区域就可以实现吊重的消摆。 相似文献
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汽车起重机回转系统使用最频繁,作业时产生的压力冲击会影响相关液压元件工作寿命,制约回转系统的工作性能,所以如何减轻回转制动时的晃动是回转系统设计的核心。本文介绍了汽车起重机回转系统设计的要点,针对不同吨位的汽车起重机给出了一些设计方法。 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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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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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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《中国标准化(英文版)》2014,(4)
正Responding to ISO’s appeal for survey for the to-be-developed ISO Strategy Plan for 2016-2020,SAC hosted a special workshop over the needs and comments of various fi elds on June 8 in Beijing.The workshop was attended by ISO President-elect and Ansteel General Manager Zhang Xiaogang,SAC Vice-Administrator Yu Xinli,and 30 experts from 相似文献
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《中国标准化(英文版)》2014,(5)
正The review group of Asia Pacific Laboratory Accreditation Cooperation(APLAC)carried out a 4-day peer review of the proficiency testing provider(PTP)for China National Accreditation Service for Conformity Assessment(CNAS)from July 28 to 31,2014.CNAS passed the PTP review with excellent performance.Two senior peer reviewers of APLAC made a comprehensive,rigorous and detailed review of CNAS’s PTP accreditation activities,and made the on-spot inspection of the review groups in Shanghai and Shenzhen respectively. 相似文献
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《中国标准化(英文版)》2014,(4)
正China and Greece Sign the Standardization Cooperation Agreement Witnessed by Chinese Premier Li Keqiang and Greek Prime Minister Antonis Samaras,AQSIQ Minister Zhi Shuping and ELOT Chairman and Executive Director Angelos Tolkas signed the SAC-ELOT Standardization Cooperation Agreement.The Agreement is one of the critical cooperation documents signed during Li Keqiang’s visit in Greece,encouraging China and Greece to 相似文献