Engineering topics

Chiang, C. K.

Publications and source records attributed to Chiang, C. K..

12 records

NASA NTRS1993

Nonlinear random response prediction using MSC/NASTRAN

An equivalent linearization technique was incorporated into MSC/NASTRAN to predict the nonlinear random response of structures by means of Direct Matrix Abstract Programming (DMAP) modifications and inclusion of the nonlinear differential stiffness module inside the iteration loop. An iterative process was used to determine the rms displacements. Numerical results obtained for validation on simple plates and beams are in good agreement with existing solutions in both the linear and linearized regions. The versatility of the implementation will enable the analyst to determine the nonlinear random responses for complex structures under combined loads. The thermo-acoustic response of a hexagonal thermal protection system panel is used to highlight some of the features of the program.

Robinson, J. H.↗

NASA NTRS1993

Nonlinear vibrations of thin arbitrarily laminated composite plates subjected to harmonic excitations using DKT elements

A finite element formulation is presented for determining the large-amplitude free and steady-state forced vibration response of arbitrarily laminated anisotropic composite thin plates using the Discrete Kirchhoff Theory (DKT) triangular elements. The nonlinear stiffness and harmonic force matrices of an arbitrarily laminated composite triangular plate element are developed for nonlinear free and forced vibration analyses. The linearized updated-mode method with nonlinear time function approximation is employed for the solution of the system nonlinear eigenvalue equations. The amplitude-frequency relations for convergence with gridwork refinement, triangular plates, different boundary conditions, lamination angles, number of plies, and uniform versus concentrated loads are presented.

Chiang, C. K.↗

NASA NTRS1992

Dynamic response and sonic fatigue analysis at NASA Langley for hypersonic vehicle structures

This paper presents an overview of three research topics being pursued at the NASA Langley Research Center for dynamic response prediction and sonic fatigue analysis of hypersonic vehicle structures. The first is the development of a numerical simulation procedure within the framework of a finite element analysis for the prediction of the large deflection random response of simple panels. The second topic is an implementation of the equivalent linearization technique in a commercial finite element code for the prediction of large deflection random response of complicated panels. The last area is the calculation of a dynamic stress intensity factor in the frequency domain for use in sonic fatigue crack growth prediction.

Rizzi, Stephen A.↗

NASA NTRS1991

A finite element random response analysis of a complex panel with fluid-conveying pipes

A finite element approach is developed for a complex panel with fluid-conveying pipes undergoing large deflections subjected to random loadings. The influence of fluid velocity on the random response is investigated. The root-mean-square (rms) deflections and frequencies for different sound spectrum level value are studied. All four edges of the panel are considered to have the same conditions and restrictions. Either simply supported of clamped boundary condition with respect to the transverse deflection of the panel is considered. The prediction of fatigue life is then based on obtained rms stress. This analytical investigation will help to broaden the basic understanding of the role of fluid flow within structures subjected to acoustic loading.

Chiang, C. K.↗

NASA NTRS1991

Processing Bi-Pb-Sr-Ca-Cu-O superconductors from amorphous state

The bismuth based high T sub c superconductors can be processed via an amorphous Bi-Pb-Sr-Ca-Cu oxide. The amorphous oxides were prepared by melting the constituent powders in an alumina crucible at 1200 C in air followed by pouring the liquid onto an aluminum plate, and rapidly pressing with a second plate. In the amorphous state, no crystalline phase was identified in the powder x ray diffraction pattern of the quenched materials. After heat treatment at high temperature the amorphous materials crystallized into a glass ceramic containing a large fraction of the Bi2Sr2Ca2Cu3O(x) phase T sub c = 110 K. The processing method, crystallization, and results of dc electrical resistivity and ac magnetic susceptibility measurements are discussed.

Chiang, C. K.↗

NASA NTRS1991

Levitation of superconducting composites

The inverse levitation of a high temperature superconductor polymer composite consisting of powdered quench melt growth Ba2YCu3O(7-delta) and cyanoacrylate is reported. Magnetic hysteresis loop measurements for the composite are compared to those measured for the bulk material prior to powdering. Differences in the flux pining capability between the two material forms are small but significant.

Chiang, C. K.↗

NASA NTRS1991

A finite element large deflection random response of a pipe containing fluid flow

A finite element approach is developed for beam type pipes undergoing large deflections subjected to random loadings. The influence of fluid velocity on the random response is investigated. The root-mean-square (rms) deflections and frequencies for different sound spectrum level values are determined for pipes with both ends either simply supported or clamped. The required number of modes to achieve accurate rms deflections is studied. The prediction of fatigue life is then based on the maximum rms stress. This analytical investigation will help to broaden the basic understanding of the role of fluid flow within structures subjected to random excitations.

Chiang, C. K.↗

NASA NTRS1990

Large deflection random response of a pipe containing fluid flow subjected to random loading

An analytic approach is developed for beam type pipes undergoing large deflections subjected to random loadings. The influence of fluid velocity on the random response is investigated. The root-mean-square (rms) deflections and frequencies for different sound spectrum level values are determined for pipes with both ends either simply supported or clamped. The required number of modes to achieve accurate rms deflections and strains is also studied. The prediction of fatigue life is then based on obtained rms maximum stress. This analytical investigation will help to broaden the basic understanding of the role of fluid flow within structures subjected to acoustic loading.

Chiang, C. K.↗

NASA NTRS1990

Processing Bi-Pb-Sr-Ca-Cu-O superconductors from amorphous state

Researchers produced superconducting ceramics of the Bi-Pb-Sr-Ca-Cu-O system started from a glass. To form the glass, the mixed oxide powder was melted at 1200 C in air. The liquid was quenched rapidly by pouring it onto an aluminum plate and rapidly pressing with another plate. The quenched compound was in the form of black amorphous solid, whose x-ray powder pattern has no crystalline peaks. After heat treatment at high temperatures, the glass crystallized into a superconductor. The crystalline phases in the superconductor identified using x-ray diffraction patterns. These phases were that associated with the superconducting phases of T(sub c) = 80 K (Bi2Ca1Sr2Cu2Ox) and of T(sub c) = 110 K (Bi2Ca2Sr2Cu3Ox). The dc resistivity and the ac susceptibility of these superconductors were studied.

Chiang, C. K.↗

NASA NTRS1990

Random response of a pipe containing fluid flow subjected to acoustic loading

An analytic approach is developed for beam type pipes subjected to random loadings. The influence of fluid velocity on the random response is investigated. The root-mean-square (rms) deflections and frequencies for different sound spectrum level values with both ends, either simply supported or clamped are considered. The required number of modes to achieve reasonable accuracy to evaluate rms deflections and strains is also studied. The prediction of fatigue life is then based on obtained rms stress. This analytical investigation will help to broaden the basic understanding of the role of fluid flow within structures subjected to acoustic loading.

Chiang, C. K.↗

NASA NTRS1989

Finite element large-amplitude free and forced vibrations of rectangular thin composite plates

A finite element formulation is presented for determining the large-amplitude free and steady-state forced vibration response of arbitrarily laminated anisotropic composite rectangular thin plates. The nonlinear stiffness and harmonic force matrices of an arbitrarily laminated composite rectangular plate element are developed for nonlinear free and forced vibration analyses. The linearized updated-mode method with nonlinear time function approximation is employed for the solution of the system nonlinear eigenvalue equations. The amplitude-frequency relations for convergence with gridwork refinement, different boundary conditions, aspect ratios, lamination angles and number of plies are presented. The finite element results are compared with available approximate continuum solutions.

Chiang, C. K.↗

NASA NTRS1987

A finite element large deflection random response analysis of beams and plates subjected to acoustic loading

A finite element formulation is presented for the analysis of beams and rectangular plates undergoing large deflections subjected to Gaussian white noise excitations. Single-mode response is assumed in the present formulation. Root-mean-square (RMS) maximum deflections for simply supported and clamped beams and plates at various sound spectrum levels are obtained and compared with solutions using the Fokker-Planck-Kolmogorov equation and the equivalent linearization methods. RMS maximum stains and equivalent linear frequencies are compared with the equivalent linearization results for assessment of the accuracy of the finite element method.

Mei, Chuh↗