Studies on effects of calibration methods and current lead position on the direct current potential drop method for crack length measurement

직류전압강하법에 의한 균열길이 측정에 미치는 도선의 위치 및 보정방법의 영향에 관한 연구

  • Received : 1997.01.10
  • Published : 1997.08.25

Abstract

The effective resolution of the direct current potential drop (DCPD) method for crack length determination is strongly affected by a number of factors including wire locations and calibration method. In the present study, the effects of wire locations, thermal EMF and reference probe locations on the accuracy of calibration methods, including Hicks-Pickard equation and Johnson's equation, were examined with the CT specimens which were nine times larger than the standard specimen. In light of experimental results, it was found that Hicks-Pickard equation can accurately represent the a/W-V/Vo relationship when current input wire is located at the load line. It was also found that the accuracy of DCPD method can be greatly improved with the thermal EMF calibration and the use of Vo value at a/W = 0.241. The use of reference potential was found to be impractical when current input wire is located at the load line.

Keywords

DCPD method;thermal EMF;reference voltage