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991.
992.
指出了确定磨削能传入工件比例对研究GH4169合金磨削机理的必要性,分析了已有理论计算公式确定磨削GH4169合金过程中磨削能传入工件比例的局限性。设计和实施了试验与有限元分析相结合的方法,对单晶刚玉砂轮磨削GH4169合金过程中磨削能传入工件的比例进行了确定,并进一步对该比例与磨削工艺参数之间的关系进行了研究,拟合了关系方程。结果表明,在试验工艺条件下,磨削能传入工件比例在25%~62%之间,且该比例与工艺参数之间的关系可用指数函数形式的方程描述。 相似文献
993.
考虑激振频率的可倾瓦推力轴承动特性理论与试验研究 总被引:3,自引:0,他引:3
为了研究激振频率对可倾瓦推力轴承动特性的影响,提出考虑激振频率的动特性建模方法和试验方法。依据可倾瓦轴承刚度和阻尼定义,将激振频率引入可倾瓦推力轴承动特性计算过程,通过建立轴向扰动下的膜厚方程、雷诺方程及瓦块运动方程,推导出包含激振频率的可倾瓦推力轴承动特性数学模型,计算分析刚度和阻尼随扰动频率(激振频率与主轴转频的比值)、转速及载荷的变化规律;采用脉冲激振法在可倾瓦推力轴承试验台进行动特性试验,得到不同激振频率、转速及载荷条件下刚度、阻尼的试验结果,并和相应的理论计算值进行对比分析。结果表明:当扰动频率较小时,可倾瓦推力轴承刚度随其增加而逐步增大,阻尼随其增加而逐步减小;当扰动频率增加到一定程度后,其刚度和阻尼逐步趋于稳定。此外,转速和载荷对其刚度和阻尼随扰动频率的变化幅度基本无影响。 相似文献
994.
低速不可压绕流中,头部形状明显影响鱼雷或UUV的流体动力特性。针对头部平端面上装设小整流锥的钝头形状雷体,采用Fluent流体分析软件,数值模拟雷体低速绕流流场特性。在0°~5°迎角范围内计算获得雷体压强分布和速度分布及运动阻力和升力系数,讨论分析结果并给出了详细模拟计算过程。 相似文献
995.
《Measurement》2014
The de-noising performance and convergence behavior of the adaptive evolutionary digital filter (EDF) are restricted by the factors of constant evolutionary coefficients and taking the reciprocal of average energy of residual signal as the fitness function. In this paper, an improved adaptive evolutionary digital filter based on the simplex method (EDF-SM) is proposed to overcome the shortcomings of the original EDF. A new evolutionary rule was constructed by introducing the simplex-based mutating method and by then combining this with the original cloning and mating methods. The reciprocal of sample entropy was taken as the fitness function and variable evolutionary coefficients were employed. Numerical examples show that the proposed EDF-SM exhibits a higher convergence rate and a better de-noising behavior than the other EDFs. The effectiveness of the proposed method in discovering fault characteristics and detecting faults of rolling element bearings is supported using an experimental test. 相似文献
996.
TENG Xiaoyan KONG Fankai ZHANG Jiatai 《机械工程学报(英文版)》2008,21(2):65-71
To manage the complexities of hull module partitions, a new approach to the partitions of hierarchical modules for shipbuilding is proposed. Based on the assembly and manufacture process, the approach determines the hierarchy and basis of the module partition first, and then according to the type of connection between the parts of the block module, the degree of membership for the rational connection is gained and the fuzzy relation matrix between different parts is then established. The fuzzy clustering technique is used to partition the modules, and then the method of fuzzy comprehensive assessment is used to choose a relative reasonable scheme. A case study has been conducted, which proves that the approach is feasible and applicable; Especially it obtains the sub-module partition, which sets up the shipbuilding process at a higher-level assembly and has offered effective tools for the modular ship design. 相似文献
997.
Vehicle mass is an important parameter in vehicle dynamics control systems. Although many algorithms have been developed for the estimation of mass, none of them have yet taken into account the different types of resistance that occur under different conditions. This paper proposes a vehicle mass estimator. The estimator incorporates road gradient information in the longitudinal accelerometer signal, and it removes the road grade from the longitudinal dynamics of the vehicle. Then, two different recursive least square method (RLSM) schemes are proposed to estimate the driving resistance and the mass independently based on the acceleration partition under different conditions. A 6 DOF dynamic model of four In-wheel Motor Vehicle is built to assist in the design of the algorithm and in the setting of the parameters. The acceleration limits are determined to not only reduce the estimated error but also ensure enough data for the resistance estimation and mass estimation in some critical situations. The modification of the algorithm is also discussed to improve the result of the mass estimation. Experiment data on asphalt road, plastic runway, and gravel road and on sloping roads are used to validate the estimation algorithm. The adaptability of the algorithm is improved by using data collected under several critical operating conditions. The experimental results show the error of the estimation process to be within 2.6%, which indicates that the algorithm can estimate mass with great accuracy regardless of the road surface and gradient changes and that it may be valuable in engineering applications. This paper proposes a recursive least square vehicle mass estimation method based on acceleration partition. 相似文献
998.
999.
When calculating aberration coefficients of secondary and higher order, there is a danger of misinterpreting the result. An example is given for a homogenous magnetic field and the source of the difficulty is described. 相似文献
1000.