Kevin D. Smith

Model‐Assisted Probability of Detection Validation for Immersion Ultrasonic Application

Model assisted probability of detection (MAPOD) is a method of calculating probability of detection versus flaws size curves which utilize physics‐based models to reduce the time, cost, and complexity of POD studies with respect to those conducted by purely empirical approaches. An approach to utilizing models combined with empirical data in calculating POD curves based on immersion ultrasonics as the example case is described. Before MAPOD calculations can be performed, the applicable physics‐based model must be validated to accuracy consistent with the desired accuracy of the resulting POD curve. In this case, the Thompson‐Gray ultrasonic measurement model was used. For the purposes of validating the MAPOD approach, a specimen was configured that would allow empirical data to be collected that would serve the dual purpose of providing input to the MAPOD calculation as well as providing input to empirical POD calculations (MIL‐HDBK‐1823). Validation of the MAPOD approach consisted of directly comparing t...

Technology enablers for improved aerospace x-ray NDE

In the current climate of reduced Military spending and lower commercial demand for aerospace products, it is of critical importance to allocate scarce technology development resources to meet projected needs. During the past decade, dramatic advances in x-ray nondestructive evaluation (NDE) technology have results in commercially viable digital radiography (DR) and computed tomography (CT) systems. X-ray CT has become an important NDE technique that not only provides data about material integrity, but also valuable volumetric data which is finding applications in reverse engineering, rapid prototyping, process control and 3D metrology. Industrial DR and CT systems have been available for almost 10 years, but are very costly, generally designed for specific applications and have well known limitations for both process development and final inspection. They have inadequate energy/flux to penetrate many large components and structures. In order to support the US Aerospace Industry in its drive towards global competitiveness, it is imperative that key enabling tools such as DR and CT be improved, made affordable, and implemented to meet the anticipated needs of the next decade of aerospace applications. This paper describes a strategy for a consortium of suppliers and users of x-ray NDE systems, academia and national laboratories to work together to attain this goal.

Economical approach to automated eddy current inspection

Eddy current inspection has long been recognized as a very sensitive and highly reliable means of detecting surface cracks in aerospace components, especially gas turbine engines. A number of factors such as equipment cost, false rejections, and throughput impacts have limited its application in the industry. All of these factors ultimately relate to the cost associated with the inspection. In the Air Force products produced to the ENSIP or PPSIP criteria, fracture critical components with relatively small flaw sizes are typically inspected as part of the production process and at their predetermined overhaul interval. The use of a hard inspection interval that requires the engine be disassembled and inspected at predetermined points in its life is fundamental for Air Force engines. In both the production and overhaul environment, dedicated facilities that utilize fully automated systems have become the norm. Fully automated systems utilize as many as seven axes and typically cost well over 1 million dollars per system require highly trained individual s to program them for new inspections. Typically, these systems are housed in their own facility which also adversely affects cost effectiveness. Once in operation, these systems can achieve crack sensitivities as small as 0.005 inches deep. To use these systems, the parts must be fully disassembled and cleaned prior to inspection. In the case of very small flaw size requirements, the parts are frequently polished to achieve an acceptable surface condition. These systems have been used very effectively in the maintenance of modern fighter engines.