Statistical Evaluation of NDE Reliability in the Aerospace Industry

The goal of this paper is to review the statistical methods used in the aerospace industries to evaluate NDE reliability. The techniques presented are consistent with the damage tolerant design and structural maintenance philosophies of the aerospace industry. The first part of this paper establishes the evaluation criteria and discusses the history of NDE reliability evaluations. The second part describes the state-of-the-art analysis methods through examples from the retirement for cause (RFC) inspection system evaluation. The last part of the paper discusses some techniques used to rate operator performance and deal with false calls

Modelling the steady state deformation stress under various deformation conditions using a single irreversible thermodynamics based formulation

A new unified description for the steady state deformation stress in single and polycrystalline metals and for various deformation conditions is presented. The new formulation for dislocation controlled deformation stems from the field of irreversible thermodynamics. The model applies to conditions of dynamic recovery as well as dynamic recrystallization and has been validated for constant strain rate and creep loading conditions. Unlike existing approaches, the new model captures transitions between deformation mechanisms within a single formulation. For conditions of dynamic recrystallization, the average dislocation density is found to be a function of the shear strain rate and a term combining the dislocation climb velocity and the grain boundary velocity. © 2009 Acta Materialia Inc.link_to_subscribed_fulltex

Estimating contour laser transmission welding start-up conditions using a novel non-contact method

This study presents a simple technique that can be used to estimate the power and speed required for optimal contour laser transmission welding as a function of material, part and laser characteristics. The technique involves rapidly scanning across a pair of laser transparent and absorbent parts in close proximity using a range of scan speeds and powers. The power and scan speed required to initiate visual degradation in the absorbent part are closely related to the conditions required for maximum shear strength. The technique has been tested successfully on four different polymers over a range of part thicknesses and carbon black levels.link_to_subscribed_fulltex