Natural frequencies extraction of a radar target from a measured response using the Prony method

2002 ◽  
Author(s):  
N.H. Younan ◽  
C.M. Shearin ◽  
T.F. Nash
Keyword(s):  
Natural Frequencies ◽  
Radar Target ◽  
Prony Method ◽  
Measured Response

A Vibrational Technique for Stress Measurement in Films

1990 ◽  
Vol 188 ◽  
Author(s):  
A. Jagota ◽  
S. Mazur ◽  
R. J. Farrisf
Keyword(s):  
Material Parameter ◽  
Natural Frequencies ◽  
Stress Measurement ◽  
Random Noise ◽  
Vibrational Analysis ◽  
Silver Films ◽  
State Of Stress ◽  
A New Technique ◽  
Membrane Vibrations ◽  
Measured Response

ABSTRACTThis paper presents a new technique for the measument of stress in films based on the classical theory of membrane vibrations. The specimens for vibrational analysis are prepared by removing a circular or square piece of the substrate far from any edge of the film (this operation preserves the state of stress in the film). The specimen is mechanically excited by random noise and its natural frequencies are peaks in the measured response of the membrane. The natural frequencies increase as the square root of stress in the film. The only material parameter needed to determine stress from the natural frequency is the density of the film. The technique has been used to measure stress in two different systems: urethane cured epoxies and silver films under different environmental conditions (temperature and humidity).

scholarly journals Changes in the Dynamic Characteristics of a Small-Scale Gymnasium Model Due to Simulated Earthquake Damage

2021 ◽  
Vol 16 (7) ◽  
pp. 1074-1085
Author(s):  
Jun Fujiwara ◽  
Akiko Kishida ◽  
Takashi Aoki ◽  
Ryuta Enokida ◽  
Koichi Kajiwara ◽  
...  
Keyword(s):  
Structural Damage ◽  
Natural Frequencies ◽  
Mode Shapes ◽  
Modal Parameters ◽  
Small Scale ◽  
Building Structures ◽  
Shake Table Tests ◽  
Large Span ◽  
Similarity Rule ◽  
Measured Response

In this study, the authors used shake-table tests to assess the modal parameters of a small-scale gymnasium model with simulated damage, the feasibility of estimating the damage to large-span building structures was studied. In Japan, large-span structures, such as gymnasiums, are expected to be used as evacuation shelters when a natural disaster occurs. As the shelter itself may be damaged in case of an earthquake, it is critical to determine whether damage has occurred, where it occurred, and how serious it is, before the shelter is used. The small-scale gymnasium was designed based on the similarity rule. Observed earthquake ground motions scaled to aftershock levels were applied to the model. The natural frequencies and mode shapes were obtained from the measured response accelerations. To study the influence of structural damage on the modal parameters, a gymnasium model with simulated damage was also tested. The results indicate that the modal parameters, e.g., natural frequencies and mode shapes, can be obtained from the response accelerations, and the damage patterns can be estimated from the changes in these modal parameters.

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