Dynamic Tests of Cracked Pipe Components

Dynamic tests were conducted involving notched sections of 4-in. (10-cm) stainless steel and Inconel-600 pipe. The specimen was a four-point bending beam with end masses sized to give an elastic first-mode frequency near that of typical field-installed piping systems (15 Hz). Specimens were loaded using sinewave excitation at this first mode natural frequency. Specimen response was compared to predictions from an elastic-plastic dynamic analysis previously developed on this program. In addition, specimen loads at failure were compared to those predicted from a net section collapse failure criterion. The results confirmed that the elastic-plastic dynamic analysis adequately predicted the dynamic response of flawed pipes under seismic-type excitation. Furthermore, net section collapse does not occur under dynamic loading conditions which simulate natural frequencies of as-installed light water reactor piping systems. Finally, a net section collapse criterion yields conservative estimates of the load capacity of flawed pipe sections provided crack growth is properly accounted for.