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Results for “anisotropic materials”

Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 289 records · Page 16
All sourcesNASA NTRSDOE OSTI
NASA NTRS1982

Hybrid state vector methods for structural dynamic and aeroelastic boundary value problems

A computational technique is developed that is suitable for performing preliminary design aeroelastic and structural dynamic analyses of large aspect ratio lifting surfaces. The method proves to be quite general and can be adapted to solving various two point boundary value problems. The solution method, which is applicable to both fixed and rotating wing configurations, is based upon a formulation of the structural equilibrium equations in terms of a hybrid state vector containing generalized force and displacement variables. A mixed variational formulation is presented that conveniently yields a useful form for these state vector differential equations. Solutions to these equations are obtained by employing an integrating matrix method. The application of an integrating matrix provides a discretization of the differential equations that only requires solutions of standard linear matrix systems. It is demonstrated that matrix partitioning can be used to reduce the order of the required solutions. Results are presented for several example problems in structural dynamics and aeroelasticity to verify the technique and to demonstrate its use. These problems examine various types of loading and boundary conditions and include aeroelastic analyses of lifting surfaces constructed from anisotropic composite materials.

Lehman, L. L.↗
NASA NTRS1987

Deformation and fatigue behavior of SSME turbopump blade materials

Directionally solidified and single crystal superalloys which are intended for use as turbopump blade materials are anisotropic both elastically and plastically. Therefore, isotropic constitutive models must be modified. Several models which are now being developed are based on metallurgical theories of deformation in these types of alloys. However, these theories have not been fully justified, and the temperature and strain regimes over which they may be valid are poorly defined. The objective of this work is to study the deformation behavior of the alloys, in order to determine the validity of these models and to thereby support the ongoing research efforts in solid mechanics.

Milligan, Walter W.↗
NASA NTRS1988

Micromechanics of cyclic deformation in SSME turbopump blade materials

Current and candidate Space Shuttle Main Engine (SSME) turbopump blade materials are anisotropic, both in their elastic and plastic response. The major objective is to characterize the plastic deformation behavior of a typical single crystal nickel-base superalloy, PWA 1480, and to use this information to help guide the development of anisotropic constitutive models.

Milligan, Walter W.↗
NASA NTRS1992

Composite-Blade Structural Analyzer

COBSTRAN (COmposite Blade STRuctural ANalyzer) computer program is preprocessor and postprocessor facilitating design and analysis of composite turbofan and turboprop blades, and of composite wind-turbine blades. Combines theories of mechanics of composites and of laminates with data base of fiber and matrix properties. Designed to carry out linear analyses required for efficient mathematical modeling and analysis of bladelike structural components made of multilayered angle-plied fiber composites. Components made from isotropic or anisotropic homogeneous materials also modeled. Written in FORTRAN 77.

Aiello, R. A.↗
NASA NTRS1998

Finite Element and Plate Theory Modeling of Acoustic Emission Waveforms

A comparison was made between two approaches to predict acoustic emission waveforms in thin plates. A normal mode solution method for Mindlin plate theory was used to predict the response of the flexural plate mode to a point source, step-function load, applied on the plate surface. The second approach used a dynamic finite element method to model the problem using equations of motion based on exact linear elasticity. Calculations were made using properties for both isotropic (aluminum) and anisotropic (unidirectional graphite/epoxy composite) materials. For simulations of anisotropic plates, propagation along multiple directions was evaluated. In general, agreement between the two theoretical approaches was good. Discrepancies in the waveforms at longer times were caused by differences in reflections from the lateral plate boundaries. These differences resulted from the fact that the two methods used different boundary conditions. At shorter times in the signals, before reflections, the slight discrepancies in the waveforms were attributed to limitations of Mindlin plate theory, which is an approximate plate theory. The advantages of the finite element method are that it used the exact linear elasticity solutions, and that it can be used to model real source conditions and complicated, finite specimen geometries as well as thick plates. These advantages come at a cost of increased computational difficulty, requiring lengthy calculations on workstations or supercomputers. The Mindlin plate theory solutions, meanwhile, can be quickly generated on personal computers. Specimens with finite geometry can also be modeled. However, only limited simple geometries such as circular or rectangular plates can easily be accommodated with the normal mode solution technique. Likewise, very limited source configurations can be modeled and plate theory is applicable only to thin plates.

Prosser, W. H.↗
NASA NTRS2006

Two-axis magnetic field sensor

A ferromagnetic thin-film based magnetic field sensor with first and second sensitive direction sensing structures each having a nonmagnetic intermediate layer with two major surfaces on opposite sides thereof having a magnetization reference layer on one and an anisotropic ferromagnetic material sensing layer on the other having a length in a selected length direction and a smaller width perpendicular thereto and parallel to the relatively fixed magnetization direction. The relatively fixed magnetization direction of said magnetization reference layer in each is oriented in substantially parallel to the substrate but substantially perpendicular to that of the other. An annealing process is used to form the desired magnetization directions.

Jander, Albrecht↗