scholarly journals A Comparative Study of Laser Doppler Vibrometers for Vibration Measurements on Pavement Materials

2018 ◽  
Vol 3 (4) ◽  
pp. 47 ◽  
Author(s):  
Navid Hasheminejad ◽  
Cedric Vuye ◽  
Wim Van den bergh ◽  
Joris Dirckx ◽  
Steve Vanlanduit
Keyword(s):  
Modal Analysis ◽  
Asphalt Concrete ◽  
Optical Measurement ◽  
Signal To Noise Ratio ◽  
Laser Doppler Vibrometer ◽  
Laser Doppler ◽  
Noise Floor ◽  
Surface Conditions ◽  
Pavement Materials

A laser Doppler vibrometer (LDV) is a noncontact optical measurement device to measure the vibration velocities of particular points on the surface of an object. Even though LDV has become more popular in road engineering in recent years, their signal-to-noise ratio (SNR) is strongly dependent on light scattering properties of the surface which, in some cases, needs to be properly conditioned. SNR is the main limitation in LDV instrumentation when measuring on low diffusive surfaces like pavements; therefore, an investigation on the SNR of different LDV devices on different surface conditions is of great importance. The objective of this research is to investigate the quality of two types of commercially available LDV systems—helium–neon (He–Ne)-based vibrometers and recently developed infrared vibrometers—on different surface conditions, i.e., retroreflective tape, white tape, black tape, and asphalt concrete. Both noise floor and modal analysis experiments are carried out on these surface conditions. It is shown that the noise floor of the He–Ne LDV is higher when dealing with a noncooperative dark surface, such as asphalt concrete, and it can be improved by improving the surface quality or by using an infrared LDV, which consequently improves the modal analysis experiments performed on pavement materials.

scholarly journals Characterizing the Complex Modulus of Asphalt Concrete Using a Scanning Laser Doppler Vibrometer

Materials ◽  
2019 ◽  
Vol 12 (21) ◽  
pp. 3542
Author(s):  
Navid Hasheminejad ◽  
Cedric Vuye ◽  
Alexandros Margaritis ◽  
Wim Van den bergh ◽  
Joris Dirckx ◽  
...  
Keyword(s):  
Asphalt Concrete ◽  
Master Curve ◽  
Complex Modulus ◽  
Optical Measurement ◽  
Laser Doppler Vibrometer ◽  
Beam Theory ◽  
Asphalt Mixtures ◽  
Laser Doppler ◽  
Bending Test ◽  
High Frequencies

Asphalt mixtures are the most common types of pavement material used in the world. Characterizing the mechanical behavior of these complex materials is essential in durable, cost-effective, and sustainable pavement design. One of the important properties of asphalt mixtures is the complex modulus of elasticity. This parameter can be determined using different standardized methods, which are often expensive, complex to perform, and sensitive to the experimental setup. Therefore, recently, there has been considerable interest in developing new, easier, and more comprehensive techniques to investigate the mechanical properties of asphalt. The main objective of this research is to develop an alternative method based on an optical measurement technique (laser Doppler vibrometry). To do this, a frequency domain system identification technique based on analytical formulas (Timoshenko’s beam theory) is used to determine the complex modulus of asphalt concrete at its natural frequencies and to form their master curve. The master curve plotted by this method is compared with the master curve obtained from the standard four-point bending test, and it is concluded that the proposed method is able to produce a master curve similar to the master curve of the standard method. Therefore, the proposed method has the potential to replace the standard stiffness tests. Furthermore, the standard stiffness methods usually conduct experiments up to the maximum frequency of 30 Hz. However, the proposed method can provide accurate complex modulus at high frequencies. This makes an accurate comparison between the properties of the asphalt mixtures in high frequencies and the development of more accurate theoretical models for simulation of specimens possible.

scholarly journals Parameter estimation of butyl rubber aided with dynamic mechanical analysis for numerical modelling of an air-inflated torus and experimental validation using 3D-laser Doppler vibrometer

2019 ◽  
Vol 38 (2) ◽  
pp. 296-311 ◽  
Author(s):  
Arun K Sharma ◽  
Bishakh Bhattacharya
Keyword(s):  
Modal Analysis ◽  
Complex Modulus ◽  
Mechanical Vibration ◽  
Laser Doppler Vibrometer ◽  
Mechanical Analysis ◽  
Mechanical Tests ◽  
Butyl Rubber ◽  
Laser Doppler ◽  
Inflatable Structures ◽  
Close Proximity

Over the few decades, there has been an exponential growth in the application of inflated torus system in the field of space deployable antenna design, solar propulsion, and aerodynamic deceleration system. However, such a system is inherently susceptible to mechanical vibration and hence requires precise modal analysis to produce stable inflatable structures. This paper summarizes all the necessary steps to be followed for dynamic analysis of inflatable structures. With this objective, a butyl rubber-based inflated torus system with dynamic material properties has been considered in this work. On performing mechanical tests of the rubber sample, properties like Prony series parameters, complex modulus, and damping values were obtained. Using laser Doppler vibrometry, the modal behavior of a butyl rubber-based air-inflated torus with free–free boundary condition was studied. The results achieved from experimental modal analysis and simulation involving fluid–structure interaction were found to be in close proximity. It is envisaged that the test template integrated with numerical validation can lay the foundation for designing complex inflatable torus structures.

scholarly journals Experimental Modal Analysis of Violins Made from Composites

Proceedings ◽  
2018 ◽  
Vol 2 (8) ◽  
pp. 535 ◽  
Author(s):  
Tim Duerinck ◽  
Mathias Kersemans ◽  
Ewa Skrodzka ◽  
Marc Leman ◽  
Geerten Verberkmoes ◽  
...  
Keyword(s):  
Composite Materials ◽  
Modal Analysis ◽  
Small Difference ◽  
Laser Doppler Vibrometer ◽  
Experimental Modal Analysis ◽  
Laser Doppler ◽  
Breathing Mode ◽  
Vibrational Response

Six prototype violins made from composite materials are made and investigated using experimental modal analysis with the roving hammer method. The average FRF’s obtained show an influence of the materials on the vibrational response up to 2200 Hz. The A0 breathing mode and B1- mode are identified and are found to be significantly lower than in classical wooden violins. Additional measurements with a Laser Doppler Vibrometer and shaker found the same modes with a small difference in frequency (3–8 Hz).

scholarly journals Implementation of the Scanning Laser Doppler Vibrometer Combined with a Light-Weight Pneumatic Artificial Muscle Actuator for the Modal Analysis of a Civil Structure

2012 ◽  
Vol 19 (3) ◽  
pp. 421-431 ◽  
Author(s):  
K. Deckers ◽  
P. Guillaume ◽  
C. Vuye ◽  
D. Lefeber
Keyword(s):  
Modal Analysis ◽  
Laser Doppler Vibrometer ◽  
Artificial Muscle ◽  
High Sensitivity ◽  
Setup Time ◽  
Laser Doppler ◽  
Scanning Laser ◽  
Artificial Muscles ◽  
Scanning Laser Doppler Vibrometer ◽  
Pneumatic Artificial Muscles

The identification of the modal parameters of bridges and other large civil constructions has become an important research issue. Different approaches have been proposed depending on the excitation used: ambient excitations (due to wind, traffic, …) or artificial excitations (e.g. impact test with heavy drop weights). In practice it turns out that not all modes are well excited by the ambient forces. Hence the application of an artificial actuator is advisable. The problem is that larger constructions often require large and heavy excitation devices, which are hard to manipulate. Another difficulty encountered in performing a modal analysis on large civil constructions is the necessity for a large number of high sensitivity sensors. Consequently a large number of cables has to be installed resulting in a large setup time.This paper is a proof-of-concept which demonstrates the possibility of using lightweight Pneumatic Artificial Muscles combined with the scanning laser Doppler vibrometer to perform a modal analysis on a civil structure. This combination allows for an important reduction in setup time and allows for sine testing as well as the application of broadband signals such as periodic chirps, true noise or multisines.

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