scholarly journals Comparison of Transmission Measurement Methods of Elastic Waves in Phononic Band Gap Materials

Materials ◽  
2021 ◽  
Vol 14 (5) ◽  
pp. 1133
Author(s):  
Maximilian Wormser ◽  
Daniel A. Kiefer ◽  
Stefan J. Rupitsch ◽  
Carolin Körner
Keyword(s):  
Wave Attenuation ◽  
Three Dimensional ◽  
Laser Doppler Vibrometer ◽  
Piezoelectric Transducers ◽  
Cellular Structures ◽  
Transmission Factor ◽  
Transmission Measurement ◽  
Quadratic Mean ◽  
Transmitted Waves ◽  
Phononic Band Gaps

Periodic cellular structures can exhibit metamaterial properties, such as phononic band gaps. In order to detect these frequency bands of strong wave attenuation experimentally, several devices for wave excitation and measurement can be applied. In this work, piezoelectric transducers are utilized to excite two additively manufactured three-dimensional cellular structures. For the measurement of the transmission factor, we compare two methods. First, the transmitted waves are measured with the same kind of piezoelectric transducer. Second, a laser Doppler vibrometer is employed to scan the mechanical vibrations of the sample on both the emitting and receiving surfaces. The additional comparison of two different methods of spatial averaging of the vibrometer data, that is, the quadratic mean and arithmetic mean, provides insight into the way the piezoelectric transducers convert the transmitted signal. Experimental results are supported by numerical simulations of the dispersion relation and a simplified transmission simulation.

Robot Assisted Modal Analysis on a Stationary Bladed Wheel

2014 ◽  
Author(s):  
L. Bertini ◽  
B. Monelli ◽  
P. Neri ◽  
C. Santus ◽  
A. Guglielmo
Keyword(s):  
Three Dimensional ◽  
Laser Doppler Vibrometer ◽  
Testing Time ◽  
Real Representation ◽  
The Real ◽  
Complex Formulation ◽  
Frequency Matching ◽  
Input Multiple Output ◽  
Multiple Measurements ◽  
Single Input

This paper shows an automated procedure to experimentally find the eigenmodes of a bladed wheel with highly three-dimensional geometry. The stationary wheel is supported in free-free conditions, neglecting stress-stiffening effects. The single input / multiple output approach was followed. The vibration speed was measured by means of a laser-Doppler vibrometer, and an anthropomorphic robot was used for accurate orientation and positioning of the measuring laser beam, allowing multiple measurements during a limited testing time. The vibration at corresponding points on each blade was measured and the data elaborated in order to find the initial (lower frequency) modes. These modal shapes were then compared to finite element simulations and accurate frequency matching and exact number of nodal diameters obtained. Being the modes cyclically harmonic, the complex formulation could be attractive, being not affected by the angular phase of the mode representation. Nevertheless, stationary modes were experimentally detected, rather than rotating, and then the real representation was necessary. The discrete Fourier transform of the blade displacements easily allowed to find both the angular phase and the correct number of nodal diameters. Successful MAC experimental to analytical comparison was finally obtained with the real representation after introducing the proper angular phase for each mode.

scholarly journals Multiscale, thermomechanical topology optimization of self-supporting cellular structures for porous injection molds

2019 ◽  
Vol 25 (9) ◽  
pp. 1482-1492
Author(s):  
Tong Wu ◽  
Andres Tovar
Keyword(s):  
Topology Optimization ◽  
Mechanical Performance ◽  
Mechanical Load ◽  
Design Method ◽  
Three Dimensional ◽  
Optimization Method ◽  
Cellular Structures ◽  
Injection Mold ◽  
Computationally Efficient ◽  
Content Type

Purpose This paper aims to establish a multiscale topology optimization method for the optimal design of non-periodic, self-supporting cellular structures subjected to thermo-mechanical loads. The result is a hierarchically complex design that is thermally efficient, mechanically stable and suitable for additive manufacturing (AM). Design/methodology/approach The proposed method seeks to maximize thermo-mechanical performance at the macroscale in a conceptual design while obtaining maximum shear modulus for each unit cell at the mesoscale. Then, the macroscale performance is re-estimated, and the mesoscale design is updated until the macroscale performance is satisfied. Findings A two-dimensional Messerschmitt Bolkow Bolhm (MBB) beam withstanding thermo-mechanical load is presented to illustrate the proposed design method. Furthermore, the method is implemented to optimize a three-dimensional injection mold, which is successfully prototyped using 420 stainless steel infiltrated with bronze. Originality/value By developing a computationally efficient and manufacturing friendly inverse homogenization approach, the novel multiscale design could generate porous molds which can save up to 30 per cent material compared to their solid counterpart without decreasing thermo-mechanical performance. Practical implications This study is a useful tool for the designer in molding industries to reduce the cost of the injection mold and take full advantage of AM.

scholarly journals Three-dimensional detonation cellular structures in rectangular ducts using an improved CESE scheme

2016 ◽  
Vol 25 (11) ◽  
pp. 114702
Author(s):  
Yang Shen ◽  
Hua Shen ◽  
Kai-Xin Liu ◽  
Pu Chen ◽  
De-Liang Zhang
Keyword(s):  
Three Dimensional ◽  
Cellular Structures

Assessment of digital image correlation vibrometry in the presence of thermal flow disturbance

2021 ◽  
Vol 263 (3) ◽  
pp. 3861-3870
Author(s):  
Kenji Homma ◽  
Paul R. Braunwart ◽  
Patrick L. Clavette
Keyword(s):  
Digital Image Correlation ◽  
Digital Image ◽  
Air Flow ◽  
Three Dimensional ◽  
Laser Doppler Vibrometer ◽  
Image Correlation ◽  
Stereo Pair ◽  
Structural Vibrations ◽  
Heated Air ◽  
Extraneous Noise

Digital Image Correlation (DIC) is an image-based method for measuring displacement and/or stain on the surface of a structure. When coupled with a stereo pair of highspeed cameras, DIC can also capture three-dimensional dynamic deformation of a structure under vibratory loading. However, high frequency and small amplitude displacement typically associated with structural vibrations mean that extra care is required during measurement and data processing. It becomes more challenging when thermal disturbances are present in the optical path, for example from a heated air flow, which introduces extraneous noise due to disturbances in the refractive index. In the present study, a simple composite plate was vibrated under a shaker excitation and stereo DIC measurements were performed. The obtained vibratory displacement results were compared against accelerometers and a laser Doppler vibrometer. Heated air flow was introduced in front of the plate to observe the effects of thermal disturbances on the DIC measurements. Although the contributions from the thermal disturbances were clearly visible in the DIC displacement data, it was shown that the vibratory deflections of the structure could still be extracted by post processing of the DIC data.

Scanning Laser Doppler Vibrometry of the Middle Ear Ossicles

1997 ◽  
Vol 76 (4) ◽  
pp. 213-222 ◽  
Author(s):  
Geoffrey R. Ball ◽  
Alex Huber ◽  
Richard L. Goode
Keyword(s):  
Middle Ear ◽  
Single Point ◽  
Three Dimensional ◽  
Laser Doppler Vibrometer ◽  
Ossicular Chain ◽  
Laser Doppler ◽  
Scanning Laser ◽  
Scanning Laser Doppler Vibrometer ◽  
Point Analysis ◽  
Ear Ossicles

This paper describes measurements of the vibratory modes of the middle ear ossicles made with a scanning laser Doppler vibrometer. Previous studies of the middle ear ossicles with single-point laser Doppler measurements have raised questions regarding the vibrational modes of the ossicular chain. Single-point analysis methods do not have the ability to measure multiple points on the ossicles and, consequently, have limited ability to simultaneously record relative phase information at these points. Using a Polytec Model PSV-100, detailed measurements of the ossicular chain have been completed in the human temporal bone model. This model, when driven with a middle ear transducer, provides detailed three-dimensional data of the vibrational patterns of the middle ear ossicles. Implications for middle ear implantable devices are discussed.

scholarly journals Cryoelectron Tomography

2003 ◽  
Vol 11 (3) ◽  
pp. 3-4
Author(s):  
Stephen W. Carmichael
Keyword(s):  
Electron Micrographs ◽  
Molecular Level ◽  
Three Dimensional ◽  
Two Dimensions ◽  
Cellular Structures ◽  
Molecular Models ◽  
3D Images

We have all seen beautiful three-dimensional (3D) renderings of molecular models, complete with helices and pleated sheets. And for more than half a century we have also seen electron micrographs of cellular structures, although usually in two dimensions. There has been a gap between these two sets of images. By developing a technique that promises 3D images at resolutions approaching the molecular level, Ohad Medalia, Igor Weber, Achilleas Frangakis, Daniela Nicastro Günther Gerisch, and Wolfgang Baumeister have bridged that gap.

scholarly journals Application of Impact-Echo Method to 3D SIBIE Procedure for Damage Detection in Concrete

2020 ◽  
Vol 10 (8) ◽  
pp. 2729
Author(s):  
Katsufumi Hashimoto ◽  
Tomoki Shiotani ◽  
Masayasu Ohtsu
Keyword(s):  
Elastic Wave ◽  
Three Dimensional ◽  
Laser Doppler Vibrometer ◽  
Concrete Specimen ◽  
Resonant Frequencies ◽  
Impact Echo ◽  
Propagation Behavior ◽  
Reinforced Concrete Slabs ◽  
Reflection Intensity

In this study, to visualize damage and defects, such as cracks and voids in concrete, the SIBIE (stack imaging of spectral amplitudes based on impact echo) procedure is applied and numerically improved to construct a three-dimensional (3D) model of elastic wave propagation behavior. A unit of arrayed accelerometers is installed to detect multi-channel signal waveforms in the frequency domain. The resonant frequencies due to reflections at each node in 3D lattice nodes are computed by using the distances from elastic wave input to multiple output locations. The amplitudes corresponding to the resonant frequencies in the spectrum are summed up as the reflection intensity of elastic wave at each node. The reflection intensity distribution is visualized finally in the targeted area three-dimensionally. Case studies are carried out on the proposal of the improved 3D-SIBIE procedure, applied to a concrete specimen with simulated-damage as well as in-situ highway RC (Reinforced Concrete) slabs in service. As for the signal detection, a non-contact elastic wave detecting system using a laser doppler vibrometer is also introduced to consider and validate the promising remote sensing and inspection technique for damage evaluation in concrete with the 3D SIBIE procedure.

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