The Effect of Prestress on Vibration Behavior of Structures in Impedance Method Damage Detection

2008 ◽  
Vol 41-42 ◽  
pp. 401-406 ◽  
Author(s):  
Xian Hua Liu ◽  
Roshun Paurobally ◽  
Jie Pan
Keyword(s):  
Damage Detection ◽  
Temperature Change ◽  
Impedance Measurement ◽  
Economic Benefits ◽  
Structural Vibration ◽  
Impedance Method ◽  
Local Vibration ◽  
Vibration Behavior ◽  
Excited Vibration ◽  
Measurement Results

Structural health monitoring or damage detection has long been a research interest for its great potential for life safety and economic benefits to the industrialized world. Structural vibration behavior is an essential signature of the integrity of structures and hence has been used for damage detection. Structural vibration impedance by way of piezoceramic patch excitation offers a local damage detection technique. It has been known that temperature change has adverse effects on the measured impedance result and can complicate the damage analysis. It is believed that one way of temperature influence on vibration is through adding thermal prestress to the structure. Prestress affects vibration in different ways on different structures and application problems. For the impedance method, prestress comes not only from temperature change but also from other sources such as wind, gravity and working load. This paper deals with prestress effects in the context of local vibration behavior of structures. A theoretical analysis is given on how prestress affects the vibration. Experimental impedance measurement results for piezoceramic patch excited vibration of simple structures such as plates under prestress are presented.

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.

scholarly journals Design of a Microcontroller Based System to Implement 4-Electode Focused Impedance Method (FIM)

2013 ◽  
Vol 4 (1) ◽  
pp. 75-79
Author(s):  
Dr Aktharuzzaman ◽  
Tanvir N Baig ◽  
K Siddique-e Rabbani
Keyword(s):  
Measurement System ◽  
Medical Physics ◽  
Impedance Measurement ◽  
Simulation Software ◽  
Signal Generator ◽  
Constant Current ◽  
Impedance Method ◽  
Electronic Circuitry ◽  
Measuring Unit

Designing of electronic circuitry and development of necessary software has been performed in the present work for a microcontroller based 4-electrode Focused Impedance measurement system. This needs a complex sequential analog switching of constant current ac signal generator and a potential measuring unit to 4 electrodes on the object under study. The performances of the designed system and the developed microcontroller software have been studied using a commercially available simulation software, ‘Proteus-7’, and the results are very satisfactory. DOI: http://dx.doi.org/10.3329/bjmp.v4i1.14690 Bangladesh Journal of Medical Physics Vol.4 No.1 2011 75-79

L1 Regularized Model Updating for Structural Damage Detection

2018 ◽  
Vol 18 (12) ◽  
pp. 1850157 ◽  
Author(s):  
Yu-Han Wu ◽  
Xiao-Qing Zhou
Keyword(s):  
Damage Detection ◽  
Structural Damage ◽  
Model Updating ◽  
Regularization Parameter ◽  
Structural Vibration ◽  
Mode Shapes ◽  
Modal Data ◽  
Vibration Data ◽  
Stiffness Reduction ◽  
Regularized Model

Model updating methods based on structural vibration data have been developed and applied to detecting structural damages in civil engineering. Compared with the large number of elements in the entire structure of interest, the number of damaged elements which are represented by the stiffness reduction is usually small. However, the widely used [Formula: see text] regularized model updating is unable to detect the sparse feature of the damage in a structure. In this paper, the [Formula: see text] regularized model updating based on the sparse recovery theory is developed to detect structural damage. Two different criteria are considered, namely, the frequencies and the combination of frequencies and mode shapes. In addition, a one-step model updating approach is used in which the measured modal data before and after the occurrence of damage will be compared directly and an accurate analytical model is not needed. A selection method for the [Formula: see text] regularization parameter is also developed. An experimental cantilever beam is used to demonstrate the effectiveness of the proposed method. The results show that the [Formula: see text] regularization approach can be successfully used to detect the sparse damaged elements using the first six modal data, whereas the [Formula: see text] counterpart cannot. The influence of the measurement quantity on the damage detection results is also studied.

Impedance Measurement as an Alternative to the Plate Count Method for Estimating the Total Count of Bacteria in Raw Milk

1987 ◽  
Vol 50 (8) ◽  
pp. 665-668 ◽  
Author(s):  
F. F. J. NIEUWENHOF ◽  
J. D. HOOLWERF
Keyword(s):  
Standard Deviation ◽  
Microbiological Quality ◽  
Impedance Measurement ◽  
Raw Milk ◽  
Plate Count ◽  
Impedance Method ◽  
Count Method ◽  
Plate Counts ◽  
Plate Count Method

An improved impedance method is described with a good standard deviation of repeatability (sm = 0.05 log unit) and a fair standard deviation of the estimate of the plate count from the detection time [(sy)x = 0.33 log unit]. Compared with the standard deviation of repeatability of the plate count method (0.07 log unit), the standard deviation of repeatability of the impedance method described is a significant improvement. The impedimetric experiments were done with a Bactometer M123. The detection times as measured by this instrument were compared with the plate counts at 30°C for samples of raw refrigerated farm milk. With this technique a good indication of the microbiological quality of raw milk can be obtained within 15 h.

scholarly journals Detection of Pin Failure in Carbon Fiber Composites Using the Electro-Mechanical Impedance Method

Sensors ◽  
2020 ◽  
Vol 20 (13) ◽  
pp. 3732
Author(s):  
Jochen Moll ◽  
Matthias Schmidt ◽  
Johannes Käsgen ◽  
Jörg Mehldau ◽  
Marcel Bücker ◽  
...  
Keyword(s):  
Carbon Fiber ◽  
Damage Detection ◽  
Fiber Composite ◽  
Mechanical Impedance ◽  
Impedance Method ◽  
Carbon Fiber Composites ◽  
Carbon Fiber Composite ◽  
Bending Loads ◽  
Metallic Parts ◽  
Hybrid Carbon

This paper presents a proof of concept for simultaneous load and structural health monitoring of a hybrid carbon fiber rudder stock sample consisting of carbon fiber composite and metallic parts in order to demonstrate smart sensors in the context of maritime systems. Therefore, a strain gauge is used to assess bending loads during quasi-static laboratory testing. In addition, six piezoelectric transducers are placed around the circumference of the tubular structure for damage detection based on the electro-mechanical impedance (EMI) method. A damage indicator has been defined that exploits the real and imaginary parts of the admittance for the detection of pin failure in the rudder stock. In particular, higher frequencies in the EMI spectrum contain valuable information about damage. Finally, the information about damage and load are merged in a cluster analysis enabling damage detection under load.

GROUND AND AIRBORNE RESISTIVITY SURVEYS OF PERMAFROST NEAR FAIRBANKS, ALASKA

Geophysics ◽  
1975 ◽  
Vol 40 (4) ◽  
pp. 641-656 ◽  
Author(s):  
P. Hoekstra ◽  
P. V. Sellmann ◽  
A. Delaney
Keyword(s):  
Surface Impedance ◽  
Apparent Resistivity ◽  
Surface Sediments ◽  
Impedance Measurement ◽  
Impedance Method ◽  
Frozen Ground ◽  
Near Surface ◽  
Fine Grained ◽  
Ground Conditions ◽  
Geotechnical Information

In permafrost regions investigations for such geotechnical endeavors as route selection for roads and pipelines and site investigations for buildings and dam construction often require that a careful assessment be made of the presence or absence of frozen ground, of the ice content of frozen ground, and of the depth of frozen ground. In the vicinity of Fairbanks, Alaska, where the permafrost is discontinuous, ground and airborne methods of mapping electrical resistivity using radiowaves were tested as means of delineating permafrost. When the resistivity maps are compared with surficial geological data, the following conclusions are reached: (1) In areas of fine‐grained sediments, where the near surface sediments are relatively uniform, VLF resistivity delineates permafrost. (2) In areas where surface sediments vary widely (flood plains), VLF resistivity shows little information on permafrost conditions but can provide other important geotechnical information, such as, depth to bedrock, surface soil type, and layering. Comparison of the apparent resistivity derived from a surface impedance measurement at VLF on the ground with the apparent resistivity derived from an airborne measurement of wavetilt shows that the regional trends in the data agree, but the surface impedance measurements show much more local detail in ground conditions. When the surface layers are also frozen, the surface impedance method of measuring ground resistivity was found to have distinct advantages over conventional galvanic methods in terms of production and problems associated with probe contact resistance.

Long-term impedance measurement results of single HeLa cell based on three-pillars structure

2013 ◽  
Author(s):  
Yi-Ling Lin ◽  
Ming-Kun Chen ◽  
Sung-Lin Tsai ◽  
Ling-Sheng Jang ◽  
Min-Haw Wang
Keyword(s):  
Hela Cell ◽  
Impedance Measurement ◽  
Measurement Results

P006 Statistical damage detection of CFRP using electrical resistance changes due to temperature change

2007 ◽  
Vol 2007 (0) ◽  
pp. 609-610
Author(s):  
Kosuke TAKAHASHI ◽  
Akira TODOROKI ◽  
Yoshinobu SHIMAMURA ◽  
Atsushi IWASAKI ◽  
Ryosuke MATSUZAKI
Keyword(s):  
Damage Detection ◽  
Temperature Change ◽  
Electrical Resistance ◽  
Statistical Damage
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