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Technical Paper

A Comparison of Fatigue Test Techniques for Gas Turbine Oils - (Report of the CRC-Aviation Bearing Fatigue Panel of the Group on Gas Turbine Lubrication)

1968-02-01
680322
A number of specimen life performance tests were conducted on three test lubricants selected to demonstrate their gross ranking capabilities. The results indicated that the test rigs should be used only for gross ranking. A large difference in magnitude of life values were obtained even though agreement in gross ranking was obtained by three out of the five participating laboratories. Further testing is recommended under preselected test conditions and lubricants.
Technical Paper

A Computer Program for Predicting Fatigue Crack Propagation

1981-02-01
810594
A general computer program has been developed for analytic fatigue crack growth. It is designed so that the user does not need to have an extensive background in Fracture Mechanics Theory. This FORTRAN program can analyze the growth of most common types of cracks and accounts for the transition from part-thru to completely thru-the-thickness crack. The input loading may be a mission profile or arbitrary cyclic stresses with or without concentrated loads and may be repeated a number of times. There are built-in corrections for geometry, plastic-zone size, plane-stress vs. plane-strain and applicability of Linear-Elastic-Fracture-Mechanics, and there are options available for crack growth rate calculations, retardation models and plastic zone corrections.
Technical Paper

A Fastener Analysis Addressing Various Types of Misfit and an Innovative Simple Design Solution

2010-09-28
2010-01-1833
The fastener analysis for an airframe panels under random cyclic loading conditions were analyzed with various elaborate solutions. But here a simple technique is proposed to analyze the problem and prove the necessity for a design solution. It is shown that the misfit in the fastener system reduces the load capacity of the joint due to the lack of contact or reduced contact. This reduced contact also produces various stress concentration at the contact zones. In the cyclic loading environment this reduced load capacity and increased stress concentration produces elastic plastic deformation around the contact locations and at the same time a crack develops and propagates beyond the fastener system. This creates a load leak transparent to the fastener system. Thus the misfit fastener systems have a higher probability of aging than the fit fasteners. With the proof in hand various design patterns were proposed to improve the fatigue characters under varying types of loading conditions.
Technical Paper

A Human Factors Evaluation of Extravehicular Activity Gloves

1989-07-01
891472
One of the major problems faced in Extravehicular Activity (EVA) glove development has been the absence of concise and reliable methods to measure the effects of EVA gloves on human-hand capabilities. NASA has sponsored a program to develop a standardized set of tests designed to assess EVA-gloved hand capabilities in six performance domains: Range of Motion. Strength, Tactile Perception, Dexterity, Fatigue, and Comfort, Based upon an assessment of general human-hand functioning and EVA task requirements, several tests within each performance domain were developed to provide a comprehensive evaluation. All tests were designed to be conducted in a glove box with the bare hand, an EVA glove without pressure, an EVA glove at operation pressure. Thus, the differential effect on performance of the glove with and without pressure was tested. Bare hand performance was used to “calibrate” the effects. Ten subjects participated in the test setup as a repeated-measures experimental design.
Technical Paper

A Linear Approach in Sonic Fatigue Analysis and Calculations

1963-01-01
630240
The problems involved in resonance response of structual elements are examined in a somewhat different perspective. Important basic principles are briefly stated and supported with experimental data. Fundamental conditions delineated by a simple elastic system in one degree of freedom are found to be applicable with due modifications to an apparently nonlinear behavior. The use of a “Duffing’s curve” is established with adaptations to random responses.
Technical Paper

A Prescreening Methodology for Proactively Reducing Human Error Proneness

2004-07-19
2004-01-2486
Human performance deterioration in extreme conditions challenges the viability of critical scenarios during a space mission. Exposure to space flight environment, including microgravity appears to increase the stress on the sensory-motor controls regulatory system in the brain because it is calibrated to operate under gravity. Any pre-existing central dysfunction can allow an input overload which can cascade to and alter other related functions down the functional hierarchy, such as physical (fine postural control, coordination and dexterity, strength, reaction time, fatigue, space perception/orientation) cognitive(trajectory control, attention and vigilance, time awareness, decision making, concentration, and memory), and emotional (motivation, self-control, calmness/aggressiveness). This phenomenon has direct influence on an individual’s tendency for “error proneness”.
Technical Paper

A Prototype Power Assist EVA Glove

1991-07-01
911384
The most recent generation of space suit EVA gloves has addressed the problem of loose fit and stiffness in the fingers, but it remains difficult to build a glove assembly with low metacarpophalangeal joint stiffness. Fatigue due to constantly displacing the glove from a neutral position has been reported as the limiting factor in some EVA activities. This paper outlines an actuation system that uses gas filled bladders attached to the back of the EVA glove to provide the necessary force to bend the glove at the metacarpal joint, thus providing greater endurance during finger grasping tasks. A simple on-off controller senses hand movement through small pressure sensors between the finger and the glove restraint. The controller then fills or exhausts the bladders on the back of the glove to effectively move the neutral position of the glove as the hand inside moves.
Journal Article

A Sequence Retainable Iterative Algorithm for Rainflow Cycle Counting

2014-01-15
2013-01-9091
To get a sequence retainable rainflow cycle counting algorithm for fatigue analysis, an alternate equivalent explanation to rainflow cycle counting is introduced, based on which an iterative rainflow counting algorithm is proposed. The algorithm decomposes any given load-time history with more than one crest into three sub-histories by two troughs; each sub-history with more than one crest is iteratively decomposed into three shorter sub-histories, till each sub-history obtained contains only one single or no crest. Every sub-history that contains a single crest corresponds to a local closed (full) cycle. The mean load and alternate load component of the local cycle are calculated in parallel with the iterative procedure.
Journal Article

A Stress-Based Non-Proportionality Parameter for Considering the Resistance of Slip Systems of Shear Failure Mode Materials

2016-04-11
2016-01-9081
Multiaxial loading on mechanical products is very common in the automotive industry, and how to design and analyze these products for durability becomes an important, urgent task for the engineering community. Due to the complex nature of the fatigue damage mechanism for a product under multiaxial state of stresses/strains which are dependent upon the modes of loading, materials, and life, modeling this behavior has always been a challenging task for fatigue scientists and engineers around the world. As a result, many multiaxial fatigue theories have been developed. Among all the theories, an existing equivalent stress theory is considered for use for the automotive components that are typically designed to prevent Case B cracks in the high cycle fatigue regime.
Technical Paper

A Study of the Influence of Drilling Method and Hole quality on Static Strength and Fatigue Life of Carbon Fiber Reinforced Plastic Aircraft Material

2002-10-01
2002-01-2650
This paper describes ongoing research on the effects of hole quality on basic material properties / allowables of carbon fibre composite material. Using a novel test programme, the benefits of orbital drilling over traditional (or conventional) methods have been compared. Static (compression and tension) and dynamic (fatigue) tests have been performed on standard aerospace industry coupons. In order to identify the influence of the drilling method on the fracture behavior and fatigue properties of the material, acoustic emission has been performed during the testing. Roundness and surface replica studies have enabled the geometrical properties of the holes to be defined at different stages of the test. These measurement techniques were performed in order to correlate and understand the preliminary results of the tests.
Technical Paper

A Study of the Influence of WC-10Co-4Cr HVOF Coating on Mechanical Properties of AISI 4340 Steel

2001-03-05
2001-01-4066
Aircraft landing gear manufacturers are considering WC thermal spray coatings applied by the high-velocity oxygen-fuel (HVOF) process as an alternative to hard chrome plating. The question to be answered is if the performance of the alternative candidate is at least comparable to results obtained for hard chrome plating. The objective of this research is to compare the influence of the WC-10Co-4Cr coating applied by HVOF process and hard-chromium electroplating on the fatigue strength of AISI 4340 steel with and without shot peening. S-N curves were obtained in axial fatigue tests for the base material, chromium plated and tungsten carbide coated specimens.
Technical Paper

A Study on Effects of Aircraft Noise Environment on its Structure

1987-11-13
872450
In this paper are reported some measurements of the noise environment of the aircraft, discussed the obtained noise load distribution and frequency spectra of the structure, preliminarily analysed the factors affecting the magnitude of parameters concerned and response characteristics of acoustic vibration of the structure, briefly summarized the noise load spectra and the method of drawing up them, the method of acoustic fatigue test and principles for selecting the parameters” through practical example. Some methods and results of analysing and remedying the troubles caused by the acoustic fatigue are also dealt with in the paper.
Technical Paper

A Superior Method of Installing Aircraft Fittings and Hardware

2006-09-12
2006-01-3120
Typical aerospace hardware and fittings; especially those that penetrate bulkheads, are usually large and heavily flanged, requiring a thick or large diameter pad-up around the penetration hole. The assembly is often complex with multiple holes to accept satellite fasteners to attach the fitting to the structure. This process adds weight to the structure, limits design flexibility, is labor intensive and often time consuming to install. This paper introduces an innovative method of installing aerospace fittings and hardware using proven cold expansion technology. This advanced bulkhead fitting system provides a fast and robust installation process that reduces both cost and assembly complexity compared to traditional methods, while providing a lighter weight installation, increased structural design options and improved fatigue life.
Standard

AEROSPACE HYDRAULICS AND ACTUATION LESSONS LEARNED

1992-01-13
HISTORICAL
AIR4543
This Aerospace Information Report (AIR) contains technical information on aerospace hydraulic and actuation technologies lessons learned. The lessons learned were prepared by system designers and hydraulic engineers from the aerospace industry and government services as part of SAE Committee A-6, Aerospace Fluid Power, Actuation, and Control Technologies, and were presented at three Lessons Learned Symposia in 1989 and 1990 held during A-6 Committee meetings. The technical topics represent many years of design experience in hydraulics and actuation, which it is felt is a resource for learning that should be documented and made available to current and future aerospace hydraulic engineers and designers. The document is organized into two sections; systems and components, with further categories within the components section.
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