Life extension of structural components via an improved nondestructive testing methodology

Abstract

An experimental study was performed to determine the flaw detection sensitivity of advanced nondestructive testing (NDT) techniques with respect to structural applications. The techniques analyzed exemplify the incorporation of digital technology into NDT and includes the following: meandering winding magnetometer array (MWM-array@) eddy current, phased-array ultrasonic (PA-UT), three dimensional computed tomography (3DCT), and digital radiography (DR). The three classes of samples inspected with these techniques consisted of alloy block specimens containing flat bottom hole (FBH) arrays, probability of detection (POD) wedding cake samples, and actual airplane engine components. Results from the sensitivity analyses were compared to current NDT techniques used industrially. An image analysis program called Cellprofiler was used to optimize the threshold correction factor for selected results. The Cellprofiler output was analyzed in conjunction with POD software, and the integration of digitally advanced NDT techniques with image analysis software resulted in approximately a threefold improvement in the minimum detectable flaw size at the 90/95 POD/CL level. An improved inspection methodology was presented which incorporated redundancy in the in-service inspection plan with the use of Bayesian updating techniques to forecast remnant life. Reliability block diagrams for structural disk and blade aircraft engine components were presented as examples of the methodology. Implementation of the proposed NDT methodology significantly increases the feasibility of a retirement-forcause (RFC) approach to be applied to aging structural components in a cost-effective manner.