Aircraft Response Transfer Functions Referred to Aircraft Body Axes

2013 ◽  
pp. 523-528
Keyword(s):  
Transfer Functions ◽  
Response Transfer

Calculating the response of waveguides to base excitation using the wave and finite element method

2021 ◽  
pp. 107754632098131
Author(s):  
Jamil Renno ◽  
Sadok Sassi ◽  
Wael I Alnahhal
Keyword(s):  
Finite Element Method ◽  
Finite Element ◽  
Transfer Functions ◽  
Travelling Waves ◽  
Model Free ◽  
Time Harmonic ◽  
Element Approach ◽  
Response Transfer ◽  
Free Wave Propagation ◽  
Element Method

The prediction of the response of waveguides to time-harmonic base excitations has many applications in mechanical, aerospace and civil engineering. The response to base excitations can be obtained analytically for simple waveguides only. For general waveguides, the response to time-harmonic base excitations can be obtained using the finite element method. In this study, we present a wave and finite element approach to calculate the response of waveguides to time-harmonic base excitations. The wave and finite element method is used to model free wave propagation in the waveguide, and these characteristics are then used to find the amplitude of excited waves in the waveguide. Reflection matrices at the boundaries of the waveguide are then used to find the amplitude of the travelling waves in the waveguide and subsequently the response of the waveguide. This includes the displacement and stress frequency response transfer functions. Numerical examples are presented to demonstrate the approach and to discuss the numerical efficiency of the proposed method.

Excitation Force Identification of Rotating Machines Using Operational Rotor/Stator Amplitude Data and Analytical Synthesized Transfer Functions

1988 ◽  
Vol 110 (3) ◽  
pp. 307-314 ◽  
Author(s):  
J. Verhoeven
Keyword(s):  
Transfer Function ◽  
Transfer Functions ◽  
Measurement Techniques ◽  
Error Sources ◽  
Typical Application ◽  
Vibration Data ◽  
Amplitude Data ◽  
Error Sensitivity Analysis ◽  
Excitation Techniques ◽  
Response Transfer

Hydraulic excitation forces of rotating machinery are normally determined by direct measurement techniques like strain gages, load cells, etc. This paper presents an indirect method, in which frequency response transfer functions are analytically generated, using linear rotor/stator models. Inverse transfer function matrices are multiplied with operational vibration data to yield fourier transformed operational excitation forces. Analytical excitation techniques and numerical inversion methods of the system transfer function matrix are evaluated. External error sources and guidelines for an error sensitivity analysis of the predicted forces are described. Experimental verification is presented on a large horizontal centrifugal pump, with reasonable results. Typical application is shown on multistage hydro carbon and boilerfeed pumps.

Spectral Analysis of Freight Car Truck Lateral Response

1982 ◽  
Vol 104 (4) ◽  
pp. 297-304
Author(s):  
L. M. Sweet ◽  
A. Karmel
Keyword(s):  
Spectral Analysis ◽  
Transfer Functions ◽  
Scale Model ◽  
Lateral Response ◽  
Series Of Experiments ◽  
Freight Car ◽  
Track Irregularity ◽  
Low Levels ◽  
Response Modes ◽  
Response Transfer

This paper summarizes methods used to quantify the lateral response of freight car trucks to random track irregularity inputs. Spectral analysis is applied to the results of an extensive series of experiments using a one-fifth scale model of a truck and half carbody, in which all inertial, friction, creep, and stiffness forces are dynamically scaled. The repeatability and confidence limits for estimates of the spectral densities of track inputs and truck response variables are determined. The influence of forward velocity, truck internal friction, and axle load on the dominant truck response modes is presented. Cross spectral methods are used to reference signals to the true track centerline, and to compute lateral response transfer functions and coherence levels. The low levels of coherence between track inputs and freight car truck/carbody response indicate that linear transfer functions do not represent the response adequately, and that measured output spectra are superior to transfer functions for comparison of truck configurations.

A simple way for producing holographic filters suitable for image improvement

1978 ◽  
Vol 36 (1) ◽  
pp. 226-227
Author(s):  
K.-H. Herrmann ◽  
E. Reuber ◽  
P. Schiske
Keyword(s):  
Transfer Functions ◽  
Diffraction Order ◽  
Lateral Position ◽  
Simple Method ◽  
Spatial Frequencies ◽  
Resolution Electron ◽  
Wiener Filters ◽  
Image Improvement ◽  
Optical Reconstruction ◽  
Set Up

Aposteriori deblurring of high resolution electron micrographs of weak phase objects can be performed by holographic filters [1,2] which are arranged in the Fourier domain of a light-optical reconstruction set-up. According to the diffraction efficiency and the lateral position of the grating structure, the filters permit adjustment of the amplitudes and phases of the spatial frequencies in the image which is obtained in the first diffraction order.In the case of bright field imaging with axial illumination, the Contrast Transfer Functions (CTF) are oscillating, but real. For different imageforming conditions and several signal-to-noise ratios an extensive set of Wiener-filters should be available. A simple method of producing such filters by only photographic and mechanical means will be described here.A transparent master grating with 6.25 lines/mm and 160 mm diameter was produced by a high precision computer plotter. It is photographed through a rotating mask, plotted by a standard plotter.

Analytic integration of contrast transfer functions

1988 ◽  
Vol 46 ◽  
pp. 822-823
Author(s):  
Peter Rez
Keyword(s):  
Wave Function ◽  
Transfer Function ◽  
Transfer Functions ◽  
Spherical Aberration ◽  
Continuous Distribution ◽  
Objective Lens ◽  
Direction Parallel ◽  
Scattering Angle ◽  
Analytic Integration ◽  
Image Position

In high resolution microscopy the image amplitude is given by the convolution of the specimen exit surface wave function and the microscope objective lens transfer function. This is usually done by multiplying the wave function and the transfer function in reciprocal space and integrating over the effective aperture. For very thin specimens the scattering can be represented by a weak phase object and the amplitude observed in the image plane is1where fe (Θ) is the electron scattering factor, r is a postition variable, Θ a scattering angle and x(Θ) the lens transfer function. x(Θ) is given by2where Cs is the objective lens spherical aberration coefficient, the wavelength, and f the defocus.We shall consider one dimensional scattering that might arise from a cross sectional specimen containing disordered planes of a heavy element stacked in a regular sequence among planes of lighter elements. In a direction parallel to the disordered planes there will be a continuous distribution of scattering angle.

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