考虑转速的舰船推进轴系抗冲击计算和分析

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舰船推进轴系的抗冲击性能是舰船生命力的主要影响因素之一。为了分析推进轴系在转动状态下的抗冲击性能，将其视为一个低速的转子系统，采用有限元法建立推进轴系受横向冲击载荷的计算模型，并用Newmark法对模型进行数值求解。通过实例仿真计算，研究推进轴系冲击响应特征及转速的影响。计算结果表明，转轴的回转效应使其在垂直和水平方向的弯曲振动相互耦合，其影响等效为阻尼效应，与静态轴系冲击响应相比，当系统阻尼较小时，转速对大转动惯量部件附近位置的响应影响较大，不可忽略；但当系统阻尼较大时，转速的影响较小。轴系的最大冲击位移出现在距离较远的相邻两轴承间的轴中部；轴的弯曲变形能有效地吸收冲击能量，故螺旋桨的冲击加速度响应不大。 The anti-shock performance of the propulsion shafting is one of the decisive factors for the survival of warships. In this paper, the rotating propulsion shafting is treated as a low-speed rotor dynamic system. Based on the rotor dynamics theory, a finite element model of the rotating propulsion shafting is developed for analyzing its dynamic response under shock load. The differential equation of the presented model is solved by using the Newmark method. The characteristic of the dynamic response of the propulsion shafting under lateral shock load and the effects of rotation speed on the response is investigated through numerical simulations. It is found that the gyroscopic effect of the rotating shafting makes the bending vibrations in horizontal and vertical direction coupled, and the gyroscopic effect can be equivalent to a system＇ s damping effect. It is found that when the damping of shafting is smaller, the gyroscopic effect on the dynamic response is relatively larger. The maximum shafting deflection under lateral shock occurs at the middle of a segment of the shaft between two neighbouring bearings with larger spacing. Since the bending deflection of the shaft can absorb the shock energy effectively, the acceleration of propeller is greatly attenuated.