共查询到20条相似文献，搜索用时 31 毫秒
1.
LIU Jiao-min WANG Jing-hong 《浙江大学学报(A卷英文版)》2007,8(3):469-474
The switching arc that occurs in contact gap when contact of low voltage apparatus closes or breaks in electric circuit is harmful to the contacts, insulation, and reliability of electrical gear because of its very high temperature. As arcing time is very short in switching gear, it is very difficult to observe arc phenomena directly for researchers. Therefore, visualization of switching arc is important for understanding arc phenomena, to analyze the arc features, and to improve the design and reliability of switching gear. Based on analyzing the visualization methods proposed by researchers, a new switching arc capturing approach is introduced in this paper. Arc image acquisition, and image processing techniques were studied. A switching arc image acquisition and visual simulation software based on high speed CCD camera hard ware system was designed and implemented to yield en- hanced arc image with good visual effect. 相似文献
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REN Wan-bin CUI Li LUO Fu-biao ZHAI Guo-fu 《浙江大学学报(A卷英文版)》2007,8(3):434-438
Published research is minimal on vibration characteristics of hermetically sealed electromagnetic relay (EMR) ex- posed to mechanical environment. The vibration characteristics of armature system, link contact system with electromagnetic system will cause EMR malfunction. The nonlinear dynamics model of armature systems was studied by considering electro- magnetic attraction force and opposite mechanical force in this paper. Angular displacements of armature under different sinu- soidal vibration conditions are solved in order to obtain the failure mode result from armature system. Vibration tests showed the presented analyzing method is suitable for EMR. The conclusions are instructive for increasing vibration resistance of armature systems of EMR, and are significant for reliability design of switch apparatus. 相似文献
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设计开发了一种垂直提拉机,该装置采用液压传动系统以液体静压力进行动力传递和控制,并采用了与振动源柔性连接的隔离技术以达到运行时振动小、低速且稳定的效果。研究表明,装置的主要构件———液压系统各元件的正确选用决定了装置的性能,对液压缸行程及最小速度、液压泵流量、电磁换向阀和溢流调节阀等的型号和要求等进行了讨论。为薄膜制备领域的教学科研和应用技术研究提供了一种高品质的薄膜制备设备。 相似文献
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针对不同悬架的性能特点,分别建立了被动悬架、主动悬架的车身与车轮两自由度振动模型,基于Matlab软件用白噪声法模拟了路面不平度随机输入,在此基础上,对被动悬架与主动悬架的性能进行了仿真对比.仿真结果表明:主动悬架能更好地衰减振动,因此具有更佳的平顺性. 相似文献
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莫文辉 《十堰职业技术学院学报》2013,26(1):97-99
随机因素对振动的影响不可忽略。本文将质量刚度、阻尼系数看作随机变量,研究了单自由度强迫振动的共振频率的可靠性。对随机变量进行计算机模拟,产生大量样本。应用Monte Carlo模拟研究了振动位移的可靠性。模拟次数越多,求得的可靠度精度越高。算例表明本文方法是正确的。 相似文献
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The current method to solve the problem of active suspension control for a vehicle is often dealt with a quarter-car or half-car model.But it is not enough to use this kind of model for practical applications.In this paper,based on considering the influence of factors such as,seat and passengers a MDOF(multi-degree-of-freedom)model describing the vehicle motion is set up.The MODF model,which is 8DOF of four independent suspensions and four wheel tracks,is more applicable by comparison of its analysis result with some conventional vehicle models.Therefore,it is more suitable to use the 8DOF full-car model than a conventional 4DOF half-car model in the active control design for car vibration.Based on the derived 8DOF odel,a controller is designed by using LQ(linear quadratic)control theory,and the appropriate control scheme is selected by testing various performance indexes.Computer simulation 8is carried out for a passenger car running on a road with step disturbance and random road disturbance expressed by Power Spectral Density(PSD).Vibrations corresponding to ride comfort are derived under the foregoing road disturbances.The response results for uncontrolled and controlled system are compared.The response of vehicle vibration is greatly suppressed and quickly damped.which testifies the effect of the active suspenson.The results achieved for various controllers are compared to invesigate the influence of different control schemes on the control effect. 相似文献
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This study presents the random-effects rating scale model (RE-RSM) which takes into account randomness in the thresholds over persons by treating them as random-effects and adding a random variable for each threshold in the rating scale model (RSM) ( Andrich, 1978 ). The RE-RSM turns out to be a special case of the multidimensional random coefficients multinomial logit model (MRCMLM) ( Adams, Wilson, & Wang, 1997 ) so that the estimation procedures for the MRCMLM can be directly applied. The results of the simulation indicated that when the data were generated from the RSM, using the RSM and the RE-RSM to fit the data made little difference: both resulting in accurate parameter recovery. When the data were generated from the RE-RSM, using the RE-RSM to fit the data resulted in unbiased estimates, whereas using the RSM resulted in biased estimates, large fit statistics for the thresholds, and inflated test reliability. An empirical example of 10 items with four-point rating scales was illustrated in which four models were compared: the RSM, the RE-RSM, the partial credit model ( Masters, 1982 ), and the constrained random-effects partial credit model. In this real data set, the need for a random-effects formulation becomes clear. 相似文献
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ZHANG Hui ZHOU Chang-lei WANG Shu-juan ZHAI Guo-fu 《浙江大学学报(A卷英文版)》2007,8(3):444-448
Particle Impact Noise Detection (PIND) test is a reliability screening technique for hermetic device that is prescribed by MIL-PRF-39016E. Some test conditions are specified, although MIL-PRF-39016E did not specify how to obtain these condi- tions. This paper establishes the dynamics model of vibration process based on first order mass-spring system. The corresponding Simulink model is also established to simulate vibration process in optional input excitations. The response equations are derived in sinusoidal excitations and the required electromagnetic force waves are computed in order to obtain a given vibration and shock accelerations. Last, some simulation results are given. 相似文献
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设计了一种半主动力跟踪PI控制器，对由磁流液(MR)阻尼器作为悬架阻尼器的汽车模型进行控制分析．MR阻尼器的2种不同模型在闭环的汽车悬架控制系统模型中得到了应用．2种模型是基于均值阻尼力对速度(f-v)特性的均值F-v模型，和描述阻尼力非光滑滞环和饱和特性的滞环f-v模型．汽车模型用来研究力跟踪PI控制算法和MR阻尼器对车辆的振动抑制性能．仿真分析还指出了MR阻尼器的非线性，特别是滞环特性对汽车悬架系统的性能影响．结果表明所提出的控制方法对由MR阻尼器驱动的汽车悬架系统能产生很好的减振效果，不仅体现在对悬架弹簧支撑车厢的共振抑制和对驾乘人员舒适性敏感频域的振动抑制，还体现在对汽车轮胎共振频率周围的振动抑制．结果还进一步说明了MR阻尼器所存在的滞环特性对汽车悬架性能的不良影响． 相似文献
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Giuseppe Carlo Marano 《浙江大学学报(A卷英文版)》2008,9(1):15-25
Based on a multiobjective approach whose objective function （OF） vector collects stochastic reliability performance and structural cost indices, a structural optimization criterion for mechanical systems subject to random vibrations is presented for supporting engineer＇s design. This criterion differs from the most commonly used conventional optimum design criterion for random vibrating structure, which is based on minimizing displacement or acceleration variance of main structure responses, without considering explicitly required performances against failure. The proposed criterion can properly take into account the design-reliability required performances, and it becomes a more efficient support for structural engineering decision making. The multiobjective optimum （MOO） design of a tuned mass damper （TMD） has been developed in a typical seismic design problem, to control structural vibration induced on a multi-storey building structure excited by nonstationary base acceleration random process A numerical example for a three-storey building is developed and a sensitivity analysis is carried out. The results are shown in a useful manner for TMD design decision support. 相似文献
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A general procedure is proposed to estimate the reliability of a dual-span rotor based on nonparametric modeling on random uncertainty. First, the vibration equation of the rotor with random uncertainty is constructed based on random matrices through the nonparametric modeling approach. Second, the reliability estimation is then performed by response spectral analysis and the moment method. By making full use of the advantages of nonparametric method and response spectral analysis, not only is the requirement on probability density function (PDF) avoided, but also the first and second moments are no longer needed to be estimated or assumed for calculating the reliability. Finally, the statistical index Z*-value based on short-term predictability is introduced to investigate the influence of random uncertainties on the reliability of the dual-span rotor. Illustrating examples show that the results obtained from the proposed procedure are consistent with those from short-term predictability, such that dangerous ranges can be well identified during the start-up process of the rotor. 相似文献
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理论分析发动机转矩波动产生机理,通过有限元分析得到离散化曲轴模型,建立了滑动轴承动态接触数学模型;协同各子部件间动力学关系,考虑燃气压力、变惯性力等激励载荷,在ADAMS中建立发动机曲轴连杆机构多体动力学模型,仿真计算发动机不同稳态工况下动态转矩,研究曲轴弹性、滑动轴承弹性支承、输出转速等对发动机输出动态转矩的影响。通过试验对比和简谐分析,表明了仿真方法的可行性和准确性,为车辆动力传动系统的扭振分析提供激励条件。 相似文献
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刘景军 《武汉工程职业技术学院学报》2002,14(2):1-3,8
根据齿轮动力学原理，在武钢调车用内燃机车中间齿轮箱全传动系统两种动力学模型（即扭转、横向振动模型）的基础上建立弯扭耦合振动模型。 相似文献
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A good mechanical model of magnetorheological damper (MRD) is essential to predict the shock isolation performance of MRD in numerical simulation. But at present, the mechanical models of MRD were all derived from the experiment subjected to harmonic vibration loads. In this paper, a commercial MRD (type RD-1005-3) manufactured by Lord Corporation was studied ex-perimentally in order to investigate its isolation performance under the impact loads. A new me-chanical model of MRD was proposed according to the data obtained by impact test. A good agreement between the numerical results and test data was observed, which showed that the model was good to simulate the dynamic properties of MRD under impact loads. It is also demon-strated that MRD can improve the acceleration and displacement response of the structure obvi-ously under impact loads. 相似文献
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本文运用Bayes及多层Bayes方法对具有冷贮备部件串联系统的失效率,可靠度与平均失效时间进行了估计,最后通过随机模拟对这两种估计进行了比较分析. 相似文献
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A good mechanical model of magnetorheological damper (MRD) is essential to predict the shock isolation performance of MRD in numerical simulation.But at present,the mechanical models of MRD were all derived from the experiment subjected to harmonic vibration loads.In this paper,a commercial MRD (type RD-1005-3) manufactured by Lord Corporation was studied experimentally in order to investigate its isolation performance under the impact loads.A new mechanical model of MRD was proposed according to the data obtained by impact test.A good agreement between the numerical results and test data was observed,which showed that the model was good to simulate the dynamic properties of MRD under impact loads.It is also demonstrated that MRD can improve the acceleration and displacement response of the structure obviously under impact loads. 相似文献
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Chromatograms of tocopherol homologues were obtained by a column of analytical size （inner diameter （ID） 0.46 cm cm×10 cm） packed with silica gel. Adsorption isotherms and film mass-transfer coefficient were estimated from the chromatograms by using a general rate model, which considers axial dispersion, external mass-transfer and intraparticle diffusion. Based on the obtained isotherms and mass-transfer coefficient, the separation process of tocopherol homologues on simulated moving bed （SMB） was simulated using the same model. According to the simulated results, a mixture of α-, γ-, δ-tocopherols and other impurities was separated on an SMB equipment. The SMB equipment was composed of 8 columns of ID 2 cm× 1 0 cm, with 2 columns in each section. The solid phase was silica gel, and the mobile phase was n-hexane/2-propanol （99/1 by volume）. γ- and δ-tocopherols of purity greater than 98% were obtained with recovery greater than 98%. The effects of operating conditions （flow rates and switching time） on the performance of SMB were studied by both simulation and experiments. It was found that all the simulation results were quite close to the experimental results. We conclude that process development and optimization of operating conditions of SMB by simulation are feasible. 相似文献