scholarly journals Modal analysis of an underwing search-light fairing

2019 ◽  
Vol 20 (1-2) ◽  
pp. 147-150
Author(s):  
Jarosław Bednarz ◽  
Wojciech Lisowski
Keyword(s):  
Numerical Analysis ◽  
Modal Analysis ◽  
Mass Distribution ◽  
Structural Dynamics ◽  
Experimental Modal Analysis ◽  
Flight Tests ◽  
Analysis Techniques ◽  
Aerodynamic Properties ◽  
Local Stiffness ◽  
Attachment Place

Many applications of aircraft require using dedicated elements of equipment attached to the fuselage or wings. These elements change aerodynamic properties of the aircraft. They modify spatial mass distribution and local stiffness in the attachment place. Structural dynamics of the modified airframe is usually investigated with use of the numerical analysis techniques. Verification of results of such the analysis is carried out experimentally. The basic method of testing is the experimental modal analysis. In the paper, there is presented an exemplary application of the experimental modal analysis to testing of a modified airplane structure with a search-light covered by its fairing attached under a wing. The described experiments consisted of the ground as well as the in-flight tests. The paper reports description and results of the experiments.

Experimental Modal Analysis of the Advanced Combat Helmet

2011 ◽  
Author(s):  
Alessio Medda ◽  
Jay Shridharani ◽  
Cameron D. Bass ◽  
Valeta Carol Chancey
Keyword(s):  
Modal Analysis ◽  
Experimental Modal Analysis ◽  
Measurement Noise ◽  
Local Models ◽  
Frequency Model ◽  
Analysis Techniques ◽  
Input And Output ◽  
Specific Input ◽  
Least Squares Techniques

In this work we present a study of the characterization of an Advanced Combat Helmet (ACH) using experimental modal analysis techniques. A medium-sized helmet was impacted at different location and the vibration response was used to estimate a global frequency model. This was achieved using the modal parameters of the local models obtained for a specific input-output location and combining them in a global model. The estimation of the frequency model was done using well-established least squares techniques, while the contribution of measurement noise in input and output was considered.

scholarly journals Influence of Crack on Modal Parameters of Cantilever Beam Using Experimental Modal Analysis

2018 ◽  
Vol 1 (1) ◽  
pp. 16-23 ◽  
Author(s):  
Siva Sankara Babu Chinka ◽  
Balakrishna Adavi ◽  
Srinivasa Rao Putti
Keyword(s):  
Numerical Analysis ◽  
Modal Analysis ◽  
Natural Frequency ◽  
Cantilever Beam ◽  
Damping Ratio ◽  
Crack Depth ◽  
Experimental Modal Analysis ◽  
Mode Shapes ◽  
Modal Parameters ◽  
Crack Location

In this paper, the dynamic behavior of a cantilever beam without and with crack is observed. An elastic Aluminum cantilever beams having surface crack at various crack positions are considered to analyze dynamically. Crack depth, crack length and crack location are the foremost parameters for describing the health condition of beam in terms of modal parameters such as natural frequency, mode shape and damping ratio. It is crucial to study the influence of crack depth and crack location on modal parameters of the beam for the decent performance and its safety. Crack or damage of structure causes a reduction in stiffness, an intrinsic reduction in resonant frequencies, variation of damping ratios and mode shapes. The broad examination of cantilever beam without crack and with crack has been done using Numerical analysis (Ansys18.0) and experimental modal analysis. To observe the exact higher modes of beam, discretize the beam into small elements. An experimental set up was established for cantilever beam having crack and it was excited by an impact hammer and finally the response was obtained using PCB accelerometer with the help sound and vibration toolkit of NI Lab-view. After obtaining the Frequency response functions (FRFs), the natural frequencies of beam are estimated using peak search method. The effectiveness of experimental modal analysis in terms of natural frequency is validated with numerical analysis results. This paper contains the study of free vibration analysis under the influence of crack at different points along the length of the beam.

Full-Scale Gate Measurements

2017 ◽  
pp. 593-625
Keyword(s):  
Modal Analysis ◽  
Structural Dynamics ◽  
Fem Analysis ◽  
Field Measurements ◽  
Full Scale ◽  
Experimental Modal Analysis ◽  
Experimental Results ◽  
Physical Measurement ◽  
Theoretical Predictions ◽  
The Stability

In this chapter, dynamic field measurements of three full-scale operational Tainter gates are documented. Measurements of the in-air gate structural dynamics were made when feasible or were simulated using FEM analysis when physical measurement was not possible. In-water structural dynamics were documented using experimental modal analysis with gate excitation supplied by the sudden tension failure of a carefully machined steel rod. The field measurements permitted assessments of the stability of each gate and these assessments are compared with theoretical predictions. Two gates were found to be stable and one was determined to have a potential instability. Theoretical predictions are shown to agree with the experimental results from field measurements.

Effect of Bass Bar Tension on Modal Parameters of a Violin's Top Plate

2015 ◽  
Vol 39 (1) ◽  
pp. 145-149 ◽  
Author(s):  
Ewa B. Skrodzka ◽  
Bogumił B.J. Linde ◽  
Antoni Krupa
Keyword(s):  
Modal Analysis ◽  
Experimental Modal Analysis ◽  
Mode Shapes ◽  
Modal Parameters ◽  
Normal Value ◽  
Modal Damping

Abstract Experimental modal analysis of a violin with three different tensions of a bass bar has been performed. The bass bar tension is the only intentionally introduced modification of the instrument. The aim of the study was to find differences and similarities between top plate modal parameters determined by a bass bar perfectly fitting the shape of the top plate, the bass bar with a tension usually applied by luthiers (normal), and the tension higher than the normal value. In the modal analysis four signature modes are taken into account. Bass bar tension does not change the sequence of mode shapes. Changes in modal damping are insignificant. An increase in bass bar tension causes an increase in modal frequencies A0 and B(1+) and does not change the frequencies of modes CBR and B(1-).

The Use of Modan 3D in Experimental Modal Analysis

2013 ◽  
Vol 486 ◽  
pp. 36-41 ◽  
Author(s):  
Róbert Huňady ◽  
František Trebuňa ◽  
Martin Hagara ◽  
Martin Schrötter
Keyword(s):  
Modal Analysis ◽  
Vibration Analysis ◽  
High Speed ◽  
Mechanical Vibration ◽  
Steel Sample ◽  
Experimental Modal Analysis ◽  
Image Correlation ◽  
Optical Methods ◽  
Mode Shapes ◽  
Vibration Modes

Experimental modal analysis is a relatively young part of dynamics, which deals with the vibration modes identification of machines or their parts. Its development has started since the beginning of the eighties, when the computers hardware equipment has improved and the fast Fourier transform (FFT) could be used for the results determination. Nowadays it provides an uncountable set of vibration analysis possibilities starting with conventional contact transducers of acceleration and ending with modern noncontact optical methods. In this contribution we mention the use of high-speed digital image correlation by experimental determination of mode shapes and modal frequencies. The aim of our work is to create a program application called Modan 3D enabling the performing of experimental modal analysis and operational modal analysis. In this paper the experimental modal analysis of a thin steel sample performed with Q-450 Dantec Dynamics is described. In Modan 3D the experiment data were processed and the vibration modes were determined. The reached results were verified by PULSE modulus specialized for mechanical vibration analysis.

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