The Development of Quantitative NDI for Retirement-for-Cause.

Abstract : To investigate the viability of quantifying NDI signals, relationships between eddy current signals and flaw dimensions were examined. The prime emphasis of this report is exploring these relationships and the difficulties encountered in establishing them. A fracture mechanics/NDI-based disk rejection criteria, retirement-for-cause, which required quantitative NDI, is also described. The case of radially cracked bolt holes in a turbine disk inspected by a semiautomatic eddy current technique is used to illustrate the procedures. Monotonically increasing relationships, primarily logrithmic in nature, were observedd between signal characteristics and the dimensions of EDM notches which were used to model actual cracks. Sensitivity level and eddy current system choice were observed to significantly affect the eddy current/flaw dimension relationships. (Author)