Mechanical Impedance Measurement on Thin Layer Surface With Impedance Hammer Device

2012 ◽  
Vol 40 (5) ◽  
pp. 20120089 ◽  
Author(s):  
Mingliang Li ◽  
A. A. A. Molenaar ◽  
M. F. C. van de Ven ◽  
Wim van Keulen
Keyword(s):  
Thin Layer ◽  
Impedance Measurement ◽  
Mechanical Impedance ◽  
Layer Surface

The Effect of a Thin Layer Surface Inhomogeneity on Dynamic Surface Response

1978 ◽  
Vol 45 (1) ◽  
pp. 95-99 ◽  
Author(s):  
L. M. Brock
Keyword(s):  
Thin Layer ◽  
Half Space ◽  
Critical Parameter ◽  
Rigid Bodies ◽  
Layer Surface ◽  
Noticeable Effect ◽  
Dynamic Surface ◽  
Surface Inhomogeneity ◽  
Interface Waves ◽  
Surface Response

A thin layer surface inhomogeneity consisting of small, evenly distributed rigid bodies is perfectly bonded to an elastic half space. Constant normal and shear line loads are applied to the layer and the dynamic surface response is calculated by Laplace transform techniques. The product of the layer thickness and the rigid body/half-space mass densities proves to be a critical parameter in determining the response. It is found that the layer has a noticeable effect on the half-space surface response in relation to the free-surface behavior. In particular, while no standard surface-interface waves exist, evidence for small values of the critical parameter indicates the presence of pseudo-Rayleigh waves similar to those found in fluid-solid interface analyses.

Damage Detection Using Impedance Measurement With Magnetic Transducer

2009 ◽  
Author(s):  
X. Wang ◽  
J. Tang
Keyword(s):  
Damage Detection ◽  
Experimental Studies ◽  
Impedance Measurement ◽  
Mechanical Impedance ◽  
Design Guidelines ◽  
Impedance Method ◽  
Negative Effects ◽  
Mechanical Coupling ◽  
Magnetic Impedance ◽  
Magnetic Transducer

Impedance method has been explored for damage detection and identification. Typically, when the impedance sensor is integrated onto the mechanical structure to be monitored, its electrical impedance is directly related to the mechanical impedance of the host structure. Thus the change of impedance measurement before and after damage occurrence can be used as the damage indicator. Since the impedance information may be measured at relatively high frequency range, the impedance method could be sensitive to small-sized damage. Generally, piezoelectric transducers are employed in the impedance approach, which can serve as actuator and sensor simultaneously. In this research, a magnetic transducer approach is investigated for impedance based damage detection. To provide design guidelines, the analytical model of the resistive magnetic impedance measurement circuit is formulated. During the formulation, the two-way magneto-mechanical coupling between the transducer and the structure is systematically studied by using the Maxwell’s equations. The preliminary sensor enhancement is achieved by selecting the number of turns of wire in the electrical coil. Moreover, in order to reduce the negative effects of the high inherent inductance and large parasitic resistance of the coil with a large number of turns of wire, a new measurement circuitry is proposed, in which a negative resistive element and a capacitor are introduced to be serially connected with the original resistive circuit. Correlated numerical and experimental studies are carried out to validate the magnetic transducer in impedance based damage detection.

Measurement of loudspeaker mechanical impedance by changing the sound load at the throat of loudspeaker

2021 ◽  
Vol 263 (1) ◽  
pp. 5457-5466
Author(s):  
Shichun Huang ◽  
Liang Yu ◽  
Weikang Jiang
Keyword(s):  
Measurement System ◽  
Electrical Impedance ◽  
Structural Parameters ◽  
Impedance Measurement ◽  
Mechanical Impedance ◽  
Coupling Model ◽  
Acoustic Energy ◽  
Mathematical Relationship ◽  
Radiation Impedance ◽  
Acoustic Coupling

A loudspeaker is a device that converts electrical energy into acoustic energy by coupling between electrical impedance, mechanical impedance, and radiation impedance. The loudspeaker electro-mechanical-acoustic coupling model provides the experimental feasibility to measure the characteristic parameters. In this paper, an economical and practical measurement method of loudspeaker mechanical impedance is proposed. First, the mathematical relationship between loudspeaker electrical impedance and mechanical impedance is obtained based on the loudspeaker electro-mechanical-acoustic coupling model. Second, two electrical impedances with different known radiation impedance are measured by using a developed measurement system. Finally, the real and imaginary parts of the mechanical impedance are obtained according to the mathematical relationship. This method neither assumes that the loudspeaker mechanical impedance is constant in a frequency band nor does it build FEM models based on structural parameters. A loudspeaker is measured by using a developed measurement system. The result shows that the mechanical impedance and the force factor are functions of frequency. Moreover, a radiation impedance measurement is performed to verify the feasibility and accuracy of the proposed method.

Immunoisolation of pancreatic islets via thin-layer surface modification

2019 ◽  
Vol 305 ◽  
pp. 176-193 ◽  
Author(s):  
Shiva Pathak ◽  
Tung Thanh Pham ◽  
Jee-Heon Jeong ◽  
Youngro Byun
Keyword(s):  
Surface Modification ◽  
Thin Layer ◽  
Pancreatic Islets ◽  
Layer Surface

Mechanical impedance measurement and damage detection using noncontact laser ultrasound

2014 ◽  
Vol 39 (11) ◽  
pp. 3130 ◽  
Author(s):  
Hyeonseok Lee ◽  
Hyeong Uk Lim ◽  
Jung-Wuk Hong ◽  
Hoon Sohn
Keyword(s):  
Damage Detection ◽  
Impedance Measurement ◽  
Mechanical Impedance ◽  
Laser Ultrasound

Mechanical impedance of a thin layer in asymmetric elasticity

2018 ◽  
Vol 316 ◽  
pp. 467-479 ◽  
Author(s):  
Athmane Abdallaoui ◽  
Keddour Lemrabet
Keyword(s):  
Thin Layer ◽  
Mechanical Impedance ◽  
Asymmetric Elasticity
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