Identification of dynamic structures with special attention to damping matrix representation /

"In finite element modeling, damping parameters, structural characteristics of joints, and boundary conditions are very difficult to estimate, causing discrepancy between analytic results and actual measured behavior. Various methods of structural identification were studied and compared in terms of their basic assumptions and advantages. A nonlinear optimization based method was thought to be promising for the identification of structures with highly uncertain structural parameters. An algorithm was developed to construct the damping matrix from experimental data. A computer program was developed for verification of this method. The method appeared to work well for lightly, viscously damped structures."--Report documentation page.Cover title."Final report for period: May 1991 - September 1991.""January 1992.""WL-TR-91-3101."Includes bibliographical references.Section 1. Introduction. -- Section 2. Basic theoretical background. -- Section 3. Review of previous works. -- Section 4. Identification of damping matrix. -- Section 5. Summary and conclusion."In finite element modeling, damping parameters, structural characteristics of joints, and boundary conditions are very difficult to estimate, causing discrepancy between analytic results and actual measured behavior. Various methods of structural identification were studied and compared in terms of their basic assumptions and advantages. A nonlinear optimization based method was thought to be promising for the identification of structures with highly uncertain structural parameters. An algorithm was developed to construct the damping matrix from experimental data. A computer program was developed for verification of this method. The method appeared to work well for lightly, viscously damped structures."--Report documentation page.Research supported by the United States Air Force Flight Dynamics Directorate, and performed CSA Engineering, Inc., Palo Alto, California, Funding numbersMode of access: Internet

Nonlinear thermoelastic effects on hypersonic stability and control.

"February 1965."Includes bibliograpical references (page 47).Air Force Contract No.Mode of access: Internet

Nonlinear thermoelastic effects on hypersonic stability and control.

Includes bibliograpical references (pages 71-72).Air Force Contract No.Mode of access: Internet

Aerodynamic testing in a free-flight spark range /

"Final report for the period June 1990-March 1997.""62602F-2502-67-03.""April 1997."Includes bibliographical references.Mode of access: Internet

STORESIM : an integrated system for multi-body cfd simulations using unstructured, adaptive grids /

"This report documents the effort conducted at the Computational Mechanics Company, Inc., Austin, Texas.""62201F-2404-10-B8.""Final Report for Period September 1990-August 1996.""December 1996."Includes bibliographical references (pages 77-78)Print reproduction.Air Force Contract No.Mode of access: Internet

In-flight investigation of the effects of higher-order control system dynamics on longitudinal handling qualities /

Includes bibliographicsl references (page 178).Print reproduction.Air Force Contract No.Mode of access: Internet

Horizontal shear testing of woven fiberglass/epoxy composites /

In this program horizontal (apparent) shear data from a number of quality control efforts were compiled and augmented by additional tests. The data were used to show the effects of test parameters, cure conditions, and material age on the apparent shear. Failure modes were recorded. Findings include: (1) Based on the horizontal shear test, CE 9000 (Ferro Corp.) should not be postcured above 370 F, and the desirability and effects of a postcure between 350F and 370F should be explored before committing to this postcure condition. (2) Autoclave cure of CE 9000 will increase its resin dominated shear properties 50% or more, compared to vacuum-bag, oven-cured parts. An appreciable drop in apparent shear using the short beam method occurs as S/t6 is increased. Data should be normalized to a consistent S/t for comparison. (3) The predominant damage pattern for woven glass coupons is related to S/t and the degree of cure. (4) Certain woven glass composites require an S/t well below 5 to achieve shear failure. (5) Short beam specimens of the type investigated should be fabricated with peel plies or porous release cloth on both sides.Research supported by the United States Air Force Wright Aeronautical Laboratories."Final Report for Period January 1979 - April 1982.""October 1983."Includes bibliographical references (page 42).In this program horizontal (apparent) shear data from a number of quality control efforts were compiled and augmented by additional tests. The data were used to show the effects of test parameters, cure conditions, and material age on the apparent shear. Failure modes were recorded. Findings include: (1) Based on the horizontal shear test, CE 9000 (Ferro Corp.) should not be postcured above 370 F, and the desirability and effects of a postcure between 350F and 370F should be explored before committing to this postcure condition. (2) Autoclave cure of CE 9000 will increase its resin dominated shear properties 50% or more, compared to vacuum-bag, oven-cured parts. An appreciable drop in apparent shear using the short beam method occurs as S/t6 is increased. Data should be normalized to a consistent S/t for comparison. (3) The predominant damage pattern for woven glass coupons is related to S/t and the degree of cure. (4) Certain woven glass composites require an S/t well below 5 to achieve shear failure. (5) Short beam specimens of the type investigated should be fabricated with peel plies or porous release cloth on both sides.Mode of access: Internet

Interactive graphics program for computing three-degree-of-freedom store separation trajectories at speeds up to the critical speed /

"This memorandum describes a computer program developed under Project 821902-036 between November 1971 and January 1972.""April 1972."Mode of access: Internet

Development and testing of a new optimum design code for hypersonic wind tunnel nozzles, including boundary layer, turbulence, and real gas effects /

"Final Report for 07/01/92--11/19/95.""October 1996."Includes bibliographical references (pages 161-166)Mode of access: Internet

FORMAT : Fortran matrix abstraction technique.

The FORMAT System has been augmented with highly efficient and reliable procedures for structural analysis via an alternate solution approach which combines the rigorous generation features of the existing force method with a few new equation solving process characteristic of the current displacement methods. As a result, a tenfold increase in potential problem size to in excess of 10000 elastic degrees of freedom is the minimum currently anticipated as attainable on present major digital computers, and the linear behavioral characteristics can take immediate advantage of any advance in hardware capabilities. In making these provisions considerable emphasis was placed on the control of both physical and numerical error throughout the total solution process. To actual aerospace structures with up to 6500 degrees of freedom have been successfully processed as single entities on a production basis, that is, within the confines of a production schedule with maximum reliability at minimum cost.Research supported by the Air Force Flight Dynamics Laboratory, Air Force Systems Command, United States Air Force, and performed by the Douglas Aircraft Company."April 1973."Includes bibliographical references (pages 131-132).The FORMAT System has been augmented with highly efficient and reliable procedures for structural analysis via an alternate solution approach which combines the rigorous generation features of the existing force method with a few new equation solving process characteristic of the current displacement methods. As a result, a tenfold increase in potential problem size to in excess of 10000 elastic degrees of freedom is the minimum currently anticipated as attainable on present major digital computers, and the linear behavioral characteristics can take immediate advantage of any advance in hardware capabilities. In making these provisions considerable emphasis was placed on the control of both physical and numerical error throughout the total solution process. To actual aerospace structures with up to 6500 degrees of freedom have been successfully processed as single entities on a production basis, that is, within the confines of a production schedule with maximum reliability at minimum cost.Air Force Contract No.Mode of access: Internet