船舶“设备-基座”变参数系统复杂振动机理研究

Ship equipments commonly connect with ship hull basements through bolts or vibration isolators when rigidly or elastically fixed. If the vibration amplitude of the equipment is insignificant, the ship "equipment-base" system is regarded as a linear system. However, if the vibration of the equipment is great, bolts and the base will be pulled and compressed within periodical cycle when the equipment is rigidly fixed, or isolators will be periodically pulled and compressed within periodical cycle by the equipment if the equipment is elastically fixed. As the stiffness of bolts and the base is quite different, the extensive and compressive stiffness of vibration isolators are also varient, the stiffness of connection interface of the ship "equipment- base" system will change, and the "equipment- base" system will thus constitute a piecewise linear or a parameter variant system, which will cause the vibration spectrum of the equipment increased. The structural dynamic phenomena is highly related to the pre-tension of bolts、stiffness of bolts and the base, structural dynamics parameters of isolators, unbalanced force and momentum of the equipment. This research focuses on the study of the complex vibration situated that the unbalanced force and momentum of the equipment act on the base together. Starting from the motion differential equation of the ship "equipment-base" system, basing on the nonlinear vibration theory, combining numerical calculations and physical experiment, the complex vibration mechanism of the ship "equipment - base" system is thus fairly discussed. This study may provide theoretical reference for the vibration and noise reduction of ships and other relevant researches. The main research includes: 1) Modeling research of the complex vibration of a ship "equipment -base" system with variant parameters; 2) Influences of the system parameters to the complex vibration of a ship "equipment-base" system with variant parameters; 3) The nonlinear vibration conditions of a ship "equipment-base" system with variant parameters.

船舶设备多通过螺栓或隔振器、刚性或弹性与船体基座相连，设备微幅振动时，"设备-基座"系统可视为线性系统；设备振动较大时，设备将周期性拉伸螺栓、压缩基座，或周期性拉压隔振器，由于螺栓及基座刚度存在差异，隔振器拉压刚度也不相同，"设备-基座"系统连接界面刚度将发生改变，并构成分段线性或慢变参数系统，使设备振动线谱增加。该动力学现象与螺栓预紧力、螺栓及基座刚度、隔振器参数、设备激扰力与激扰力矩等密切相关。本研究拟针对设备不平衡激扰力与激扰力矩联合作用情况，从"设备-基座"系统微分运动方程入手，基于非线性振动理论，结合数值计算及物理试验验证，揭示船舶"设备-基座"系统复杂动力学机理，为船舶减振降噪及相关研究提供依据。主要研究包括: 1)船舶"设备-基座"变参数系统复杂振动模型研究；2)系统参数对船舶"设备-基座"变参数系统复杂振动的影响研究；3）船舶"设备-基座"变参数系统非线性振动产生条件。

船舶设备通过螺栓或隔振器、刚性或弹性与船体基座相连，其微幅振动时，“设备-基座”系统可视为线性系统；设备振动较大时，设备将周期性拉伸螺栓、压缩基座，或周期性拉压隔振器，由于螺栓及基座刚度存在差异，隔振器拉压刚度也不相同，“设备-基座”系统连接界面刚度将发生改变，并构成分段线性或慢变参数系统，使设备振动线谱增加。本研究拟针对设备不平衡激扰力与激扰力矩联合作用情况，从“设备-基座”系统微分运动方程入手，基于非线性振动理论，结合数值计算及物理试验验证，揭示船舶“设备-基座”系统复杂动力学规律，研究系统非线性振动条件。“设备—基座”变参数系统模型研究表明，设备弹性连接时，隔振器额定载荷范围内压缩迟滞效应不显著（刚度差异20%以内），加之隔振器的阻尼作用，设备非线性振动不显著；而当隔振器松动时，其运动与设备刚性安装动情况相似，将构成分段线性系统。设备刚性安装时，初始条件、设备不平衡激扰力等引起的设备振动位移大于螺栓预变形时，系统可能发生四种振动模式，从而产生多种形式的运动。在此基础上，分弹性安装及刚性安装两种形式开展了系统参数对船舶“设备-基座”变参数系统复杂振动的影响研究，分析了弹性安装时设备对船体的激励载荷特性规律，提出了基于源特性识别的设备激励载荷分析法、运动边界相似法，并进行了试验验证，验证了基于原特性识别的设备激励载荷一维、二维、三维分析模型的有效性；针对设备刚性安装情况，研究了设备不平衡激扰力、激扰力矩单独及联合作用下船舶“设备—基座”系统的非线性振动特性，系统讨论了螺栓预变形、初始条件、间隙、刚度比等对系统稳定性及共振曲线的影响规律，并开展了船舶“设备—基座”变参数系统复杂振动模型试验验证，验证了理论及数值分析的有效性，研究表明，系统非线性振动时设备将出现多频特征，并可能出现稳定性问题。最后，结合上述研究成果，给出了船舶“设备—基座”系统非线性振动条件，即不论初始条件、螺栓预紧力、还是设备不平衡激扰力与激扰力矩，当设备振动位移超过螺栓预变形时，系统将进入非线性振动状态。因此，从设备振动控制及船舶减振降噪角度，应合理选择螺栓预紧力，以避免设备出现非线性振动。

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