基于改进脉冲-空间叠加法的LNG运输船围护系统晃荡载荷反演及应力监测

Sloshing load inversion and stress monitoring of LNG carrier cargo containment system based on improved impulse-space superposition method

  • 摘要: 摘 要:【目的】晃荡载荷是围护系统最重要且最复杂的载荷之一,却由于数值模拟和模型试验的简化不能够被准确的计算或测量。为了获得准确的晃荡载荷时程特征以及实现围护系统健康实时监测,采用改进逆脉冲-空间叠加法,测量部分结构响应推导出晃荡载荷以及高应力区域(热点)响应。【方法】建立测点位置和晃荡载荷作用位置的反演数学模型,预测多区域载荷;建立晃荡载荷作用位置和热点位置的响应预测数学模型,预测多热点应力。依据杜哈梅积分建立载荷-响应方程,采用Tikhonov正则化方法求解晃荡载荷,根据L曲线法选取目标函数最优正则化参数进而得到晃荡载荷稳定正则解,并对晃荡载荷预测步长展开研究。【结果】晃荡载荷预测精度随载荷复杂度增加而降低,随载荷预测步长减小而增加。所有工况下载荷及热点应力时程曲线与真实值变化趋势一致。通过控制载荷预测步长,能够保证晃荡载荷和热点应力峰值误差分别小于10%和1%。【结论】相较于试验测量和数值模拟的正方法,载荷反演的逆方法为围护系统晃荡载荷获取提供新思路。改进逆脉冲-空间叠加法成功用于LNG运输船围护系统晃荡载荷反演以及热点应力预测,验证了该方法应用于复合材料组合结构的可行性,提供了该方法应用于其他船海结构物的参考。

     

    Abstract: Abstract:Objectives The sloshing load is one of the most important and complicated loads in the cargo containment system, but it is difficult to calculate or measure accurately due to the simplification of numerical simulation and model experiments. To obtain accurate time history characteristics of the sloshing load and realize real-time health monitoring of the cargo containment system, the inverse impulse-space superposition method was used to measure the local response of the structure and deduce the sloshing load and the response of the high-stress region (hotspot). Methods The inverse mathematical model of measuring point position and sloshing load position is established to predict multi-region load. The response prediction mathematical model of sloshing load positions and hotspot positions is established to predict the multi-hotspot stress. Load inversion is carried out according to the Duhame integral and the Tikhonov regularization method, and then the L-curve method is used to select regularization parameters. The step length for load prediction is studied. Results The prediction accuracy of sloshing load decreases with the increase of load complexity and increases with the decrease of load prediction step size. The time history curve of load and hotspot stress under all cases is consistent with the real value. By controlling the load prediction step size, the peak error of sloshing load and hotspot stress can be kept below 10% and 1%, respectively. Conclusions Compared with the positive method of experimental measurement and numerical simulation, the method of load inversion provides a new way to obtain the sloshing load of the cargo containment system. The improved inverse impulse-space superposition method has been successfully applied to the inversion of the sloshing load and the prediction of the hotspot stress of the cargo containment system of the LNG carrier, which verifies the feasibility of applying this method to the composite structure, and provides a reference for the application of this method to other ships and marine structures.

     

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