WorldCat Identities

United States Army Aviation Research and Technology Activity

Overview
Works: 179 works in 231 publications in 1 language and 14,337 library holdings
Genres: Conference papers and proceedings 
Classifications: TJ184, 621.833
Publication Timeline
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Most widely held works by United States
The effects of structural flap-lag and pitch-lag coupling on soft inplane hingeless rotor stability in hover by William G Bousman( Book )

3 editions published in 1990 in English and held by 184 WorldCat member libraries worldwide

Performance data from a wind-tunnel test of two main-rotor blade designs for a utility-class helicopter by Jeffrey D Singleton( Book )

1 edition published in 1990 in English and held by 182 WorldCat member libraries worldwide

Matrix density effects on the mechanical properties of SiC/RBSN composites by Ramakrishna T Bhatt( Book )

1 edition published in 1990 in English and held by 180 WorldCat member libraries worldwide

The room temperature mechanical properties were measured for SiC fiber-reinforced reaction-bonded silicon nitride composites (SiC/RBSN) of different densities. The composites consisted of approx. 30 vol % uniaxially aligned 142 um diameter SiC fibers (Textron SCS-6) in a reaction-bonded Si3N4 matrix. The composite density was varied by changing the consolidation pressure during RBSN processing and by hot isostatically pressing the SiC/RBSN composites. Results indicate that as the consolidation pressure during RBSN processing and by hot isostatically pressing the SiC/RBSN composites. Results indicate that as the consolidation pressure was increased from 27 to 138 MPa, the average pore size of the nitrided composites decreased from 0.04 to 0.02 um and the composite density increased from 2.07 to 2.45 gm/cc. Nonetheless, these improvements resulted in only small increases in the first matrix cracking stress, primary elastic modulus, and ultimate tensile strength values of the composites. In contrast, HIP consolidation of SiC/RBSN resulted in a fully dense material whose first matrix cracking stress and elastic modulus values were approx. 15 and approx. 50 percent higher, respectively, the ultimate tensile strength values were approx. 40 percent lower than those for unHIPed SiC/RBSN composites. The modulus behavior for all specimens can be explained by simple rule-of-mixture theory. Also, the loss in ultimate strength for the HIP temperature. (SDW)
Local delamination in laminates with angle ply matrix cracks by T. Kevin O'Brien( Book )

3 editions published in 1991 in English and held by 169 WorldCat member libraries worldwide

Identification of XV-15 aeroelastic modes using frequency-domain methods by C. W Acree( Book )

1 edition published in 1989 in English and held by 168 WorldCat member libraries worldwide

A flight-dynamic helicopter mathematical model with a single flap-lag-torsion main rotor by Marc D Takahashi( Book )

1 edition published in 1990 in English and held by 166 WorldCat member libraries worldwide

Correlation of Puma airloads lifting-line and wake calculation( Book )

1 edition published in 1989 in English and held by 164 WorldCat member libraries worldwide

A cooperative program, undertaken by organizations in the United States, England, France, and Australia, assessed the strengths and weaknesses of four lifting-line/wake methods and three CFD methods by comparing their predictions with the data obtained in flight trials of a research Puma. The Puma has been tested in two configurations: a mixed-bladed rotor with instrumented rectangular-tip and swept-tip blades, and a configuration with four identical swept-tip blades. The present paper examines the results of the lifting-line predictions. The better lifting-line methods show good agreement with lift at the blade tip for the configuration with four swept tips; the moment is well- predicted at 0.92 R, but deteriorates outboard. The predictions for the mixed- bladed rotor configuration range from fair to good. The lift prediction is better for the swept-tip blade than for rectangular-tip blade, but the reasons for this cannot be determined because of the unmodeled effects of the mixed- bladed rotor. Keywords: Helicopter flight test; Computational fluid dynamics; Helicopter airloads correlation; Helicopter rotors; Rotor blades rotary wings. (edc)
Review and analysis of the DNW/model 360 rotor acoustic data base by R. A Zinner( Book )

1 edition published in 1989 in English and held by 158 WorldCat member libraries worldwide

Applications of flight control system methods to an advanced combat rotorcraft( Book )

1 edition published in 1989 in English and held by 158 WorldCat member libraries worldwide

Stability of a rigid rotor supported on oil-film journal bearings under dynamic load by Bankim C Majumdar( Book )

3 editions published in 1987 in English and held by 149 WorldCat member libraries worldwide

Most published work relating to dynamically loaded journal bearings are directed to determining the minimum film thickness from the predicted journal trajectories. These do not give any information about the subsynchronous whirl stability of journal bearing systems since they do not consider the equations of motion. It is, however, necessary to know whether the bearing system operation is stable or not under such an operating condition. The purpose of the present paper is to analyze the stability characteristics of the system. A linearized perturbation theory about the equilibrium point can predict the threshold of stability; however it does not indicate postwhirl orbit detail. The linearized method may indicate that a bearing is unstable for a given operating condition whereas the nonlinear analysis may indicate that if forms a stable limit cycle. For this reason, a nonlinear transient analysis of a rigid rotor supported on oil journal bearings under (1) a unidirectional constant load, (2) a unidirectional periodic load, and (3) variable rotating load are performed. In this paper, the hydrodynamic forces are calculated after solving the time- dependent Reynolds equation by a finite difference method with a successive overrelaxation scheme. Using these forces, equations of motion are solved by the fourth-order Runge-Kutta method to predict the transient behavior of the rotor. With the aid of a high-speed digital computer and graphics, the journal trajectories are obtained for several different operating conditions. Keywords: Journal bearings; Stability; Dynamic loads; Bearings; Dynamics
Five year ground exposure of composite materials used on the Bell model 206L flight service evaluation by Donald J Baker( Book )

2 editions published in 1989 in English and held by 144 WorldCat member libraries worldwide

During the past ten years, NASA has sponsored programs to build a data base and establish confidence in the long-term durability of advanced composite materials. Flight service experience is being obtained on primary and secondary structural components installed on commercial aircraft and from material specimens exposed at different locations. Although commercial aircraft and helicopters may fly in the same environment the behavior of composite materials on each vehicle may differ substantially. Most of the projected usage for composites in helicopter fuselage is Kevlar-49/epoxy with selective reinforcement of graphite/epoxy using 250 F curing epoxies. Most commercial aircraft are using 350 F cure graphite/epoxy systems with very little use of Kevlar/epoxy. Considering only the effects of moisture, materials in the minimum gage structure in most helicopter fuselage would reach equilibrium moisture content in a short time whereas the heavier gage structure on a commercial aircraft could take months to reach an equilibrium condition
Acoustic measurements from a rotor blade-vortex interaction noise experiment in the German-Dutch wind tunnel (DNW) by R. M Martin( Book )

3 editions published in 1988 in English and held by 104 WorldCat member libraries worldwide

Integrated Technology Rotor Methodology Assessment Workshop proceedings of a workshop by Integrated Technology Rotor Methodology Assessment Workshop( Book )

1 edition published in 1988 in English and held by 95 WorldCat member libraries worldwide

Theory of gearing by F. L Litvin( Book )

1 edition published in 1989 in English and held by 92 WorldCat member libraries worldwide

The author has significantly contributed to the goals of the NASA/ army transmission program by his accomplishments in the science of gearing and his authorship of this book. His work has provided a mathematical basis which improves our understanding of bevel gear geometry and the manufacturing procedure. His work has provided solutions to reduce gear noise and to enable a smoother transfer of power in helicopters. In summary, he has directly contributed to advance the state of the art in helicopter power transmission technology, and has made a significant contribution to NASA's research projects and to the public good. This book explains the most general problems of the theory of gearing, but it represents only a part of Dr. Litvins's accomplishments. His research contributions have improved (1) almost all types of gearing including spur, helical, hypoid, bevel, worm, and noncircular gears; (2) tools for gear manufacture; and (3) computer programs for simulation of meshing and contact. His theorems, methods for gear synthesis, and methods for gear generation represent a very significant contribution to the science of gearing
Inflow measurements made with a laser velocimeter on a helicopter model in forward flight( Book )

4 editions published in 1990 in English and held by 90 WorldCat member libraries worldwide

Correlation of puma airloads evaluation of CFD prediction methods( Book )

2 editions published in 1989 in English and held by 89 WorldCat member libraries worldwide

Results of inphase axial-torsional fatigue experiments on 304 stainless steel by Peter J Bonacuse( Book )

1 edition published in 1989 in English and held by 89 WorldCat member libraries worldwide

A series of axial-torsional, inphase, strain-controlled, low-cycle fatigue tests were performed at room temperature on tubular specimens of 304 stainless steel. The objective was to quantify the variability in multiaxial test results among several laboratories. This report includes only data generated at the NASA Lewis Research Center's High Temperature Fatigue and Structures Laboratory. The experimental equipment and procedures used are described. The tubular specimens were polished on the outer surface to aid in the use of a cellulose film surface replication technique for detection of crack propagation. However, cracking initiated predominantly on the internal surface for all specimens. Honing of the bore of the tubular specimens lessened but did not entirely eliminate this problem. The observed fatigue lives are compared with lives calculated from three multiaxial life models. Constants for the life prediction models were obtained from uniaxial and torsion tests performed on the same heat of material. The observed fatigue lives agreed with calculated lives to within a factor of two for all but one of the life prediction models
Scaling effects in the static large defelction [i.e. deflection] response of graphite-epoxy composite beams by Karen E Jackson( Book )

2 editions published in 1989 in English and held by 89 WorldCat member libraries worldwide

Reduction of blade-vortex interaction noise using higher harmonic pitch control( Book )

2 editions published in 1989 in English and held by 88 WorldCat member libraries worldwide

Aircraft crash survival design guide by Simula Inc( )

in English and held by 0 WorldCat member libraries worldwide

 
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Alternative Names

controlled identityUnited States. Army Aviation Research and Development Command

United States. Army Aviation Research & Technology Activity

United States. Army Aviation Systems Command. Aviation Research and Technology Activity

US Army Aviation Research and Technology Activity

Languages
English (35)