水下方盒结构振动与声辐射相关性研究

针对水下结构振动与声辐射的耦合问题,重点研究了水下方盒结构在简谐激励作用下结构振动和声辐射间的相关性.在计算结构声振响应时,采用有限元结合边界元的算法,即在考虑流固耦合影响下采用有限元法计算结构的振动响应,在此基础上采用边界元法求解无限介质中的Helmhohz方程,从而求得结构的辐射声场.在结构振动和声辐射响应的基础上,计算了几个典型位置声辐射与激励点振动间的关联系数,讨论了它们的关联性.最后得出结论:除了激励源附近位置外,声辐射与结构振动间的关联性是很强的.     

Assessment of wheel loader vibration on the riding comfort according to ISO standards

Vibration accelerations were measured on a compact wheel loader during 11 operations with two drivers and with/without the activated boom suspension system (BSS). Two standards, ISO 2631-1 (1985) and ISO 2631-1 (1997), were used to assess the effect of wheel loader vibration on comfort. The assessment results of ISO 2631-1 (1985) showed that vibration in the frequency range from 4 to 20 Hz in the vertical direction and in the frequency range from 1.6 to 3.15 Hz in the vertical and driving directions plays an important role in comfort assessment. The overall total values of vibration measured on the wheel loader in all operations exceeded the ‘uncomfortable’ boundary specified in ISO 2631-1 (1997). The speed had a larger influence on the vibration intensity than the bucket load, the BSS or the driver biodynamic response during driving. During driving and V-cycle, the difference of vibration intensity with two drivers in the z-direction is larger than that in the x- and y-direction.     

柔性基座上隔振系统的能量分析

针对船用基座特点,建立起柔性基座上隔振系统的数学模型,利用该模型并采用振动功率流法对隔振系统进行计算,得到振动流规律.     

复杂悬跨条件下的管线涡激振动分析(英文)

Spans occur when a pipeline is laid on a rough undulating seabed or when upheaval buckling occurs due to constrained thermal expansion. This not only results in static and dynamic loads on the flowline at span sections, but also generates vortex induced vibration (VIV), which can lead to fatigue issues. The phenomenon, if not predicted and controlled properly, will negatively affect pipeline integrity, leading to expensive remediation and intervention work. Span analysis can be complicated by: long span lengths, a large number of spans caused by a rough seabed, and multi-span interactions. In addition, the complexity can be more onerous and challenging when soil uncertainty, concrete degradation and unknown residual lay tension are considered in the analysis. This paper describes the latest developments and a .state-of-the-art. finite element analysis program that has been developed to simulate the span response of a flowline under complex boundary and loading conditions. Both VIV and direct wave loading are captured in the analysis and the results are sequentially used for the ultimate limit state (ULS) check and fatigue life calculation.     

基于MR阻尼器的船用隔离器系统试验研究

随着船舶技术的发展，现代船舶对船用隔离器系统提出了越来越高的要求，即船用隔离器系统应同时具备低频减振和高频抗冲击的能力，这是传统的船用减振器系统所无法做到的．为了解决此问题，本文提出了一种新的船用隔离器系统，该系统由钢丝绳弹簧和磁流变阻尼器相并联组成．文中对该船用隔离器系统的减振和抗冲击性能进行了模型试验研究。减振试验的激振力频率为1-15Hz，力幅为2．94．11．76kN；冲击试验的最大冲击输入加速度为20g，脉宽为10ms，减振试验和冲击试验均采用MTS液压加载系统来进行．试验结果表明，该船用隔离器系统具有较好的减振效果，使用了MR阻尼器后系统得共振峰值被明显的削弱；在冲击试验中，冲击响应的衰减速度随着MR阻尼器的阻尼增加而明显加快，但是MR阻尼器再冲击瞬间的出力特性明显与低频振动情况下不同，MR阻尼器的出力表现为受控制电流强度影响不大．     

汽轮发电机异常振动原因分析

汽轮发电机的异常振动是发电厂最为常见故障。分析由于汽轮发电机转子不对称及热效应导致汽轮发电机产生振动的原因，并对发电机转子工作异常现象进行分析。最后，结合工程实例对某电厂大修后开机过程中异常振动故障进行分析，为发电机工频振动诊断提供分析判断的思路和方法。     

基于人工神经网络的快艇总振动预报

快艇因其重量轻、航速高，因而振动比较难控制，且一旦船体结构基本确定之后，要改善其总振动状况将更加困难。由于目前的规范计算法和有限元法需进行大量计算，费时费力，这对快艇设计的初期阶段很不利，因而在已有的设计经验的基础上，建立了快艇总振动预报的人工神经网络模型，为快艇设计的初期阶段提供参考。样本检验表明，该网络能较好地预报快艇的总振动。     

轨道不平顺导致的车桥耦合振动分析

研究目的：轨道不平顺常常是激起车桥系统耦合振动的主要因素之一，通过研究轨道不平顺导致的车桥耦合振动规律，为铁路桥梁精确设计提供理论依据。 研究方法：以H．Hamid等人提出的轨道不平顺功率谱密度为例，构造了时域内的轨道随机不平顺函数。以轨道不平顺样本函数为激振源，通过求解车桥系统耦合振动微分方程，分析铁路桥梁在列车荷载作用下的动力响应规律。 研究结果：计算了广西红水河铁路斜拉桥在列车通过时的动力响应，给出了不同车速及不同不平顺样本函数情况下桥梁主跨中点横向位移时程曲线。 研究结论：桥梁结构动力响应主要随车速及不平顺样本函数的不同而变化，且有较大的随机性。对于广西红水河铁路斜拉桥，桥梁主跨中点的最大横向位移一般在车速为75～95km／h时达到最大。     

Effects of the guideway's vibrational characteristics on the dynamics of a Maglev vehicle

The levitation control system in an electromagnetically levitated vehicle controls the voltage in its winding to maintain the air gap, which is the clearance between the electromagnet and the guideway, within an allowable range of variation, while strongly interacting with the flexible guideway. Thus, the vibrational characteristics of the guideway play an important role in the dynamics of Maglev (magnetically levitated) vehicles that utilise an active electromagnetic suspension system. In this study, the effects of the guideway's vibrational characteristics, such as natural frequency and damping, on the dynamics of the Maglev vehicle UTM-02 are numerically and experimentally analysed. From these analyses, the coupled equations of motion of the simplified vehicle–guideway model with three degrees of freedom are derived. Eigenvalues are calculated and frequency response analysis is also performed, in order to obtain a clear understanding of the dynamic characteristics resulting from the guideway's vibrational characteristics. To verify the numerical results, air gap tests of the urban Maglev vehicle UTM-02 are also carried out. These results lead us to recommend that the natural frequency of the guideway be decreased by increasing mass density rather than by decreasing rigidity, and that its damping ratio be increased in the Maglev vehicle UTM-02 employing a five-state feedback control law as a levitation control law.     

1600TEU集装箱船侧斜桨设计及首制船的试航分析

介绍一艘1600TEU集装箱船的侧斜桨设计及包括4只不同设计的侧斜桨模型比测试验。还给出两艘该首制船的试航结果及相关分析。到目前为止已有5搜1600TEU集装箱船投入国际航线参加航运。该船是目前全部由国内设计和制造的最大全集装箱船，其线型和螺旋桨设计之经中用于其他大型集装箱船的设计。