AP/ES' focus is on aircraft structures and mechanical systems, but applications can extend to any structural component subject to varied environments, stresses, and stress spectra.

Select Past and Present Technical Activities

Corrosion & Damage Tolerance Assessment

Developed the processes and procedures for performing assessments on aircraft structures that include effects of corrosion degradation with cyclic fatigue. The integration is directly compatible and complimentary to FAA and military criteria and concepts. Applications offer maintenance organizations the means to continue safety success, improve readiness, and optimize allocation of assets in support.

Corrosion Fatigue Model Development and Application

Integrated the damage mechanisms and the characteristic features of multiple types of age degradation into a holistic structural integrity process (HOLSIP) for assessing impact of the degradation on structural integrity. Conducted 'blind' predictions of experimental results that correlated very well with actual test results. Applied model to existing aircraft field problems and provided solutions for specific airframe components.

Wing Spar Cap Failure Analysis

Provided analytical failure analysis for cracking in a ground attack aircraft. Investigated several crack driving forces, recommended actions to resolve the problem.

Aircraft Fleet Tracking

Developed improved algorithms for Fatigue Life Expended (FLE) in a USN aircraft fleet. Monitor individual aircraft usage and FLE based on flight data recorder information.

AFGROW External Plug-in Model Development

Developed the infrastructure for and several examples of custom models (integral structure, multi-site damage, etc.) for the Air Force Crack Growth Code, AFGROW.

Fretting Model Development

Utilized sophisticated analytical and experimental techniques to characterize complex stress fields due to contact and other forces, integrated results into HOLSIP.

Specialized Stress Analysis and Stress Intensity Solutions

Developed detailed finite element models and parametric stress intensity solutions for numerous classes of 2-D and 3-D problems.

Spectrum Truncation Studies

Conducted crack nucleation and crack growth comparative analyses of a FSFT spectrum and several truncated spectra. Characterized the most and least damaging cycles in order to optimize the test spectrum for a low cost yet accurate representation of the design spectrum.

Microscopy of Initial Discontinuity State (IDS) and Damage Progression (2002-2006)

Characterized intrinsic material discontinuities and modified discontinuities such as corrosion pitting and fretting fatigue. Utilize marker band techniques to experimentally validate related analytical stress intensity solutions.

ASM Handbook Chapter

Provided a chapter on "Predictive Modeling of Structure Service Life" for ASM Handbook Volume 13A, Corrosion: Fundamental, Testing and Protection.