动态回路电阻是一种免拆卸的触头烧蚀情况诊断方法,在不同幅值的回路电流下测得的动态回路电阻差异很大。为了研究试验电流对动态回路电阻的影响,分别测量了两套电磨损程度不同的触头系统在不同试验电流下的动态回路电阻信号,分析了动...动态回路电阻是一种免拆卸的触头烧蚀情况诊断方法,在不同幅值的回路电流下测得的动态回路电阻差异很大。为了研究试验电流对动态回路电阻的影响,分别测量了两套电磨损程度不同的触头系统在不同试验电流下的动态回路电阻信号,分析了动态回路电阻特征量的变化规律,研究了试验电流对动态回路电阻的影响原理。研究表明提高测量电流不仅有利于弧触头行程的确定,减小动态主回路电阻与弧触头电阻,还可以减小电阻曲线的波动,减小特征量的分散度。上述现象主要是由试验电流引起的触点温度升高造成。当试验电流范围为0.7~1 k A,试验结果比较稳定,且不会烧蚀触头。展开更多
Heterogeneous brittle geomaterials are highly susceptible to cyclic loads.They contain inherent flaws and cracks that grow under fatigue loads and lead to failure.This study presents a numerical model for analyzing fa...Heterogeneous brittle geomaterials are highly susceptible to cyclic loads.They contain inherent flaws and cracks that grow under fatigue loads and lead to failure.This study presents a numerical model for analyzing fatigue in these materials based on the two-dimensional(2D)boundary element method and linear elastic fracture mechanics.The process is formulated by coupling the displacement discontinuity method with the incorporation technique of dissimilar regions and the governing equations of fatigue.The heterogeneous media are assumed to consist of materials with different properties,and the interfaces are assumed to be completely bonded.In addition,the domains include multiple cracks exposed to constant and variable amplitude cyclic loads.The stress intensity factor is a crucial parameter in fatigue analysis,which is determined using the displacement field around crack tips.An incremental crack growth scheme is applied to calculating the fatigue life.The growth rate values are employed to estimate the length of crack extension when there are multiple cracks.The interaction between cracks is considered,which also includes the coalescence phenomenon.Finally,various structures under different cyclic loads are examined to evaluate the accuracy of this method.The results demonstrate the efficiency of the proposed approach in modeling fatigue crack growth and life estimation.The behavior of life curves for the heterogeneous domain was as expected.These curves illustrate the breakpoints caused by utilizing discrete incremental life equations.At these points,the trend of the curves changed with the material properties and fatigue characteristics of the new material around the crack tips.展开更多
文摘动态回路电阻是一种免拆卸的触头烧蚀情况诊断方法,在不同幅值的回路电流下测得的动态回路电阻差异很大。为了研究试验电流对动态回路电阻的影响,分别测量了两套电磨损程度不同的触头系统在不同试验电流下的动态回路电阻信号,分析了动态回路电阻特征量的变化规律,研究了试验电流对动态回路电阻的影响原理。研究表明提高测量电流不仅有利于弧触头行程的确定,减小动态主回路电阻与弧触头电阻,还可以减小电阻曲线的波动,减小特征量的分散度。上述现象主要是由试验电流引起的触点温度升高造成。当试验电流范围为0.7~1 k A,试验结果比较稳定,且不会烧蚀触头。
文摘Heterogeneous brittle geomaterials are highly susceptible to cyclic loads.They contain inherent flaws and cracks that grow under fatigue loads and lead to failure.This study presents a numerical model for analyzing fatigue in these materials based on the two-dimensional(2D)boundary element method and linear elastic fracture mechanics.The process is formulated by coupling the displacement discontinuity method with the incorporation technique of dissimilar regions and the governing equations of fatigue.The heterogeneous media are assumed to consist of materials with different properties,and the interfaces are assumed to be completely bonded.In addition,the domains include multiple cracks exposed to constant and variable amplitude cyclic loads.The stress intensity factor is a crucial parameter in fatigue analysis,which is determined using the displacement field around crack tips.An incremental crack growth scheme is applied to calculating the fatigue life.The growth rate values are employed to estimate the length of crack extension when there are multiple cracks.The interaction between cracks is considered,which also includes the coalescence phenomenon.Finally,various structures under different cyclic loads are examined to evaluate the accuracy of this method.The results demonstrate the efficiency of the proposed approach in modeling fatigue crack growth and life estimation.The behavior of life curves for the heterogeneous domain was as expected.These curves illustrate the breakpoints caused by utilizing discrete incremental life equations.At these points,the trend of the curves changed with the material properties and fatigue characteristics of the new material around the crack tips.
