The Naval Air Systems Command (NAVAIR) provides materiel support for aircraft and airborne weapon systems for the United States Navy. It is one of the Echelon II Navy systems commands (SYSCOM), and was established in 1966 as the successor to the Navy's Bureau of Naval Weapons.NAVAIR is headquartered in Naval Air Station Patuxent River in St. Mary's County, Maryland, with military and civilian personnel stationed at eight locations across the continental United States and one site overseas. The current commander as of September 2021 is Vice Admiral Carl P. Chebi, USN. The vice commander is Leslie Taylor, SES. The deputy commander is Mr. Theodore J. Short Jr., SES. The Command Master Chief is CMDCM Todd A. Anselm, USN.NAVAIR's mission is to provide full life-cycle support of naval aviation aircraft, weapons and systems operated by Sailors and Marines. This support includes research, design, development and systems engineering, acquisition, test and evaluation, training facilities and equipment, repair and modification, and in-service engineering and logistics support.NAVAIR is organized into eight "competencies" or communities of practice namely: program management, contracts, research and engineering, test and evaluation, logistics and industrial operations, corporate operations, comptroller and counsel.The competency alignment of the organization is changing to "mission alignment."NAVAIR provides support (through people, processes, tools, training, mission facilities, and core technologies) to Naval Aviation Program Executive Officers (PEOs) and their assigned program managers, who are responsible for meeting the cost, schedule, and performance requirements of their assigned programs.
The paper is the first to highlight what appears to be a unique and unusual failure mechanism that is associated with cracks that nucleated from corrosion pits in aluminium alloy (AA) 7085-T7452 specimens that were tested under a variable amplitude load spectrum. In this study, cracks initially nucleated at corrosion pits and first grew as would be expected, namely at ninety degrees to the surface and perpendicular to the applied load. However, after reaching a depth of approximately 2 mm, these various Mode I cracks transformed into what can be best described as interlayer cracks with their surfaces at an angle of approximately ninety degrees to the initial fatigue crack surface. Analysis of the failures revealed that the maximum value of the stress intensity factor at which this phenomenon occurred, which we have defined as KIL, was substantially less than the fracture toughness for this material. As such, failure was not due to classical Mode I failure, but rather due to K exceeding what we will term KIL. Despite the unusual failures, it was found that, up to the point where this phenomenon occurred, the crack growth versus cycles histories could be reasonably accurately predicted using the small crack growth equation developed by the authors in a prior study on AA 7085-T7452 specimens with a fastener hole.
This study investigates erosion behavior of oxide/oxide ceramic matrix composites (Ox/Ox CMCs) under varying thermomechanical conditions, including erosion-only, erosion-fatigue, and erosion-creep. Single and double-sided impacts were made at a temperature of 1200 degrees C, with particle velocity of 200 m/s. Optical microscopy with three-dimensional depth scanning was used to assess the extent of erosion damage, followed by room temperature tension tests to evaluate the remaining strength of eroded specimens. The objective was to assess the combined influence of stress, temperature, and velocity on erosion behavior and remaining strength of the Ox/Ox composites. The results showed linear increase in cumulative mass loss for all specimens. Specimens with erosion under stress exhibiting higher erosion rates compared to specimens with erosion only conditions. The combined influence of stress during erosion had a minimal effect on residual strength, as the erosion process itself was the primary driver of material degradation. On the other hand, double-sided impacts distributed damage more uniformly across the material, mitigating the effects of eccentricity and resulting in a slight increase in net-section stress. This suggests that erosion with stress has a limited direct impact on strength degradation and erosion by itself is the predominant factor influencing material degradation in high-temperature erosion conditions.
This study presents a comprehensive experimental and analytical investigation into the fretting fatigue behavior of cold-sprayed ZE41A-T5 cast magnesium alloy, with particular emphasis on the influence of contact pressure, displacement amplitude, loading frequency, and crack initiation modeling. A custom-designed fretting fatigue test rig enabled decoupled application of displacement amplitude and axial loading to replicate service-relevant multiaxial stress states. To interpret the test results, a life prediction methodology was developed by integrating finite element modeling, stress concentration analysis, and the critical-plane-based Fatemi-Socie parameter. The modeling framework offers a practical and efficient tool for life prediction, reducing reliance on computationally intensive nonlinear analyses for each test scenario. The predictions demonstrate strong correlation with experimental results, with all data points falling within a +/- 1.5x scatter bands on life. Fractographic analysis further validated the modeling approach, confirming crack initiation at the upper trailing edge of the contact zone.
