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采用Archard磨损公式作为压水堆燃料棒包壳的磨损理论模型,预测燃料棒包壳与格架之间的微振磨损,其中关键的物理量是磨损系数、燃料棒与格架之间的接触力以及滑动距离。磨损系数一般通过试验确定。随着燃耗加深,燃料棒与格架之间的接触力是时变函数,燃料棒夹持力随燃耗的变化曲线可采用试验或经验公式确定。由格架刚凸的刚度、包壳与格架的接触力以及它们之间的摩擦系数确定滑动阈值,将最大湍流激励的振动响应与滑动阈值进行比较,确定燃料棒包壳相对于格架是否存在滑动,计算燃料棒包壳在微小时间间隔内的滑移距离。几个物理量确定后,对磨损公式时间积分得到燃料棒包壳的微振磨损量。根据圆柱和表面的磨损几何关系,理论推导磨损量与磨损深度的关系,确定磨损深度,将磨损深度与相关准则进行比较,评估燃料棒包壳是否满足机械完整性的要求。
Archard abrasion formula is used as the wear theoretical model of PWR fuel rod cladding to predict the fretting wear between the fuel rod cladding and the grid. The key physical quantities are the wear coefficient, the contact force between the fuel rod and the grid As well as the sliding distance. Wear coefficient is generally determined by testing. With the deepening of fuel consumption, the contact force between the fuel rod and the grid is a time-varying function, and the variation curve of the fuel rod holding force with the fuel consumption can be determined by experiment or empirical formula. The sliding threshold is determined by the stiffness of the rigid frame, the contact force between the cladding and the grid and the friction coefficient between them. The vibration response of the maximum turbulence excitation is compared with the sliding threshold to determine whether the fuel rod cladding relative to the grid Slides exist to calculate the slippage distance of the fuel rod cladding over a small time interval. After several physical quantities are determined, the fretting wear of the fuel rod cladding is obtained by integrating the wear formula time. According to the geometrical relationship between the cylinder and the surface, the relation between the amount of wear and the wear depth is deduced theoretically, the wear depth is determined, and the wear depth is compared with the relevant criteria to evaluate whether the fuel rod cladding meets the requirements of mechanical integrity.