Speed of Sound Measurement in Solids Using Polyvinylidene Fluoride (PVDF) Sensors

2013 ◽  
Author(s):  
Leon M. Headings ◽  
Kunal Kotian ◽  
Marcelo J. Dapino
Keyword(s):  
Finite Element ◽  
Stress Wave ◽  
Speed Of Sound ◽  
Polyvinylidene Fluoride ◽  
Response Times ◽  
High Sensitivity ◽  
Fast Response ◽  
Load Path ◽  
Straightforward Method ◽  
The Impact

Piezoelectric film sensors such as polyvinylidene flouride (PVDF) generate an electrical voltage in response to an applied mechanical stress with a remarkably high sensitivity. They provide very fast response times and do not require extensive signal conditioning. This paper presents a straightforward method of measuring the speed of sound in solid materials and structures using commercial PVDF sensors. PVDF sensors are most commonly used to measure stresses applied in the sensors’ thickness direction. However, this requires that the sensors be located in the load path, which may result in damage to the sensor or affect the response of the system. In this paper, two PVDF sensors are bonded to the side of a structure and a small impact is applied to one end. The sensors are used to measure the time for the impact-induced plane stress wave to travel between the sensors. The observed speed of the propagating stress wave is shown to be in good agreement with the theoretical speed of sound for the material and finite element calculations. In addition, the finite element simulations confirm the validity of the plane wave assumption for non-ideal and non-uniform impact inputs.

Investigation of Stress Wave Propagation in Brain Tissues Through the Use of Finite Element Method

2010 ◽  
Author(s):  
Biaobiao Zhang ◽  
W. Steve Shepard ◽  
Candace L. Floyd
Keyword(s):  
Finite Element ◽  
Wave Propagation ◽  
Brain Injury ◽  
Stress Wave ◽  
Brain Research ◽  
Complex Structure ◽  
Stress Wave Propagation ◽  
Wave Loads ◽  
The Impact ◽  
The Brain

Because axons serve as the conduit for signal transmission within the brain, research related to axon damage during brain injury has received much attention in recent years. Although myelinated axons appear as a uniform white matter, the complex structure of axons has not been thoroughly considered in the study of fundamental structural injury mechanisms. Most axons are surrounded by an insulating sheath of myelin. Furthermore, hollow tube-like microtubules provide a form of structural support as well as a means for transport within the axon. In this work, the effects of microtubule and its surrounding protein mediums inside the axon structure are considered in order to obtain a better understanding of wave propagation within the axon in an attempt to make progress in this area of brain injury modeling. By examining axial wave propagation using a simplified finite element model to represent microtubule and its surrounding proteins assembly, the impact caused by stress wave loads within the brain axon structure can be better understood. Through conducting a transient analysis as the wave propagates, some important characteristics relative to brain tissue injuries are studied.

A Self-Locking Technique With Fast Response and High Sensitivity for Micro-Cantilever Based Sensing of Analytes

2002 ◽  
Vol 723 ◽  
Author(s):  
A. Mehta ◽  
G. Muralidharan ◽  
A. Passian ◽  
S. Cherian ◽  
T.L. Ferrell ◽  
...  
Keyword(s):  
Response Times ◽  
High Sensitivity ◽  
Fast Response ◽  
Q Factor ◽  
Ambient Conditions ◽  
Sensor Applications ◽  
Feedback Scheme ◽  
Micro Cantilever ◽  
Lock In ◽  
Thermal Oscillations

AbstractMEMS based microcantilevers have been employed as sensors in both liquid and ambient conditions. One scheme for detection is based upon monitoring the change in microcantilever resonant frequency as a function of the adsorbed analyte concentration. However, the sensitivity is limited by the accuracy of the frequency measurements, which is a function of the Q-factor of the vibrating element and the measurement bandwidth. In this paper, we present a feedback scheme for self-locking amplification of the small-amplitude thermal oscillations of the microcantilever. Using this approach, we demonstrate an improvement in the Q-factor by two to three orders of magnitude as compared to that of the undriven microcantilever. Use of this technique eliminates the need for lock-in detection and results in improved response times for sensor applications. Experiments using the proposed feedback amplification technique show improved sensitivity for the detection of biological molecules in liquids, and for adsorbed vapors under ambient conditions.

Finite Element Stress Analysis and Strength Evaluation of Bonded Shrink Fitted Joints Under Impact Push-Off Loads

2010 ◽  
Author(s):  
Lijuan Liao ◽  
Toshiyuki Sawa
Keyword(s):  
Finite Element ◽  
Hollow Cylinder ◽  
Stress Wave ◽  
Adhesive Layer ◽  
Middle Part ◽  
Impact Loads ◽  
Stress Distributions ◽  
Static Loads ◽  
The Impact ◽  
Outside Diameter

Joints combining shrink fittings with anaerobic adhesives (bonded shrink fitted joints) have been appeared with advantages compared with those with shrink fittings only in light weight and high strength. This paper deals with the stress wave propagations and stress distributions of bonded shrink fitted joint in which a hollow cylinder is fitted at the middle part of a solid cylinder subjected to impact push-off loads with small strain rate. The stress stress wave propagations and stress distributions in bonded shrink fitted joint are analyzed in elastic and elasto-plastic deformation ranges using finite element method (FEM) as a four-body contact problem. The impact loads are applied to the joint by dropping a weight-hammer. The FEM code employed is ANSYS/LS-DYNA. The effects of the stiffness, the outside diameter and the height of hollow cylinder on the stress wave propagations at the interfaces are examined. The strength of the joint is clarified using the stress distributions obtained from numerical calculations. The normal stress near the upper edge of the outside interface of the adhesive layer increases as the rigidity and the outside diameter of the hollow cylinder decrease and the height of the hollow cylinder increases. The shear stress near the upper edge of the outside surface of the adhesive layer increases as the outside diameter and the height of the hollow cylinder increase; while it decreases as the rigidity of the hollow cylinder increases. The strength of bonded shrink fitted joint increases as the rigidity and the height of the hollow cylinder increase and the outside diameter of the hollow cylinder decreases. In addition, the characteristics of the joints subjected to impact loads are compared with those of the joints under static loads. It is observed that the characteristics of the joints subjected to impact loads are opposite to those subjected to static loads. Besides that, the attributes of the contact interface of shrink fitted joint under impact loads are compared with those of bonded shrink fitted joint under same external loads. It is found that opposite properties exist between of them. Furthermore, experiments are carried out to measure the strain response of bonded shrink fitted joints subjected to impact push-off loads. The numerical results are in a fairly good agreement with the experimental results and FEM results.

Robust Direct Hydrocarbon Sensor Based on Novel Carbon Nanotube Nanocomposites for Leakage Detection

2016 ◽  
Author(s):  
Kaushik Parmar ◽  
Chaneel Park ◽  
Simon Park
Keyword(s):  
Carbon Nanotube ◽  
Oil And Gas ◽  
Direct Detection ◽  
Detection System ◽  
High Sensitivity ◽  
Fast Response ◽  
Outdoor Environment ◽  
Sensor Technology ◽  
Leakage Detection ◽  
The Impact

Leakage in oil and gas infrastructure, often cause significant financial losses, severe damage to the environment and raises public concern. In order to minimize the impact of spills, quick detection of a leak and a rapid response are needed. The systems currently employed to detect pipeline leakage range from simple visual checking to complex hardware and software systems such as mass balance, pressure point analysis, flow deviation, acoustic emission systems, and fibre-optic-based sensing technologies. These methods are useful, but there are certain limitations. The main drawback of the majority of these leak detection technologies is that they detect leakage indirectly, often unable to detect the leakage until the major spill. The preventive monitoring system and direct detection of hydrocarbon leakage are urgently needed to enable fast response and timely repairs with less deleterious effects. Research is being conducted for the development of a functional prototype and environmental testing of in-situ carbon nanotube (CNT) nanocomposite based sensors for hydrocarbon leakage detection. The CNT nanocomposite offers a unique approach to the direct hydrocarbon leakage detection in pipelines and aboveground storage tanks (ASTs). Expanding the study from the previous report of sensor characteristics under the optimal ambient condition, it was further investigated to identify the sensor performance under harsh conditions such as the underground (exposed to the soil) with compost and moisture, high pressure, changing temperature and long-term exposure to the outdoor environment. Investigation of the sensor behavior is studied, and a performance matrix is developed that accounts for the change in sensor response to various environmental conditions. Results showed that the proposed CNT nanocomposite sensor was applicable under given conditions with immediate responses while maintaining high sensitivity to the hydrocarbon leakage. Once a list of sensor detection specifications is defined, it is anticipated that the CNT sensor technology is applicable as part of a robust, reliable and accurate early detection system for the pipeline industry.

scholarly journals Recent Progress in Microfiber-Optic Sensors

2021 ◽  
Vol 11 (1) ◽  
pp. 45-68
Author(s):  
Wei Luo ◽  
Ye Chen ◽  
Fei Xu
Keyword(s):  
Fiber Optics ◽  
Recent Progress ◽  
Response Times ◽  
Functional Materials ◽  
High Sensitivity ◽  
Fast Response ◽  
Basic Principles ◽  
Area Of Interest ◽  
Compact Size ◽  
Optical Microfiber

AbstractRecently, microfiber-optic sensors with high sensitivity, fast response times, and a compact size have become an area of interest that integrates fiber optics and nanotechnology. Distinct advantages of optical microfiber, such as large accessible evanescent fields and convenient configurability, provide attractive benefits for micro- and nano-scale optical sensing. Here, we review the basic principles of microfiber-optic sensors based on a broad range of microstructures, nanostructures, and functional materials. We also introduce the recent progress and state-of-the-art in this field and discuss the limitations and opportunities for future development.

scholarly journals On the Use of Dynamic Calibration to Correct Drop Counter Rain Gauge Measurements

Sensors ◽  
2021 ◽  
Vol 21 (18) ◽  
pp. 6321
Author(s):  
Mattia Stagnaro ◽  
Arianna Cauteruccio ◽  
Luca G. Lanza ◽  
Pak-Wai Chan
Keyword(s):  
Rainfall Intensity ◽  
High Sensitivity ◽  
Fast Response ◽  
Rain Gauge ◽  
Dynamic Calibration ◽  
Event Scale ◽  
Rain Gauges ◽  
Intensity Measurements ◽  
The One ◽  
The Impact

Dynamic calibration was performed in the laboratory on two catching-type drop counter rain gauges manufactured as high-sensitivity and fast response instruments by Ogawa Seiki Co. Ltd. (Japan) and the Chilbolton Rutherford Appleton Laboratory (UK). Adjustment procedures were developed to meet the recommendations of the World Meteorological Organization (WMO) for rainfall intensity measurements at the one-minute time resolution. A dynamic calibration curve was derived for each instrument to provide the drop volume variation as a function of the measured drop releasing frequency. The trueness of measurements was improved using a post-processing adjustment algorithm and made compatible with the WMO recommended maximum admissible error. The impact of dynamic calibration on the rainfall amount measured in the field at the annual and the event scale was calculated for instruments operating at two experimental sites. The rainfall climatology at the site is found to be crucial in determining the magnitude of the measurement bias, with a predominant overestimation at the low to intermediate rainfall intensity range.

Effects of Sensor Geometry on the Stress-Averaged Output of PVDF Sensors in Tires

2014 ◽  
Author(s):  
Leon M. Headings ◽  
Jungkyu Park ◽  
Marcelo J. Dapino
Keyword(s):  
Polyvinylidene Fluoride ◽  
Numerical Models ◽  
Low Cost ◽  
High Sensitivity ◽  
Fast Response ◽  
Voltage Output ◽  
Electrode Shape ◽  
Significant Difference ◽  
Sensor Geometry ◽  
Processing Techniques

Polyvinylidene fluoride (PVDF) sensors are attractive for use in tires due to their high sensitivity, fast response time, low cost, and ability to operate without power supplies or signal amplification. Based on sensor design, placement, and signal processing techniques, they may be used to determine tire parameters such as tire revolutions, footprint size, and cornering and traction conditions. PVDF sensors generate a voltage output that is related to the average stress acting on the sensor. For non-uniform distributions of stress over the sensor area, there can be a significant difference between the stress at a point and the average sensor stress calculated from the measured voltage. Understanding the effects of sensor geometry on sensor output is important for designing sensors for specific applications, such as tires. This paper presents analytical and numerical models for PVDF voltage output that are developed from the linear piezoelectric constitutive equations, with the average sensor stress modeled using a convolution of the stress input and the PVDF electrode shape. Parametric studies on rectangular, stepped, and triangular sensor shapes show the effects of sensor geometry on voltage output for PVDF sensors under sinusoidal and tire stress inputs.

scholarly journals Improved Sensing Capability of Integrated Semiconducting Metal Oxide Gas Sensor Devices

Sensors ◽  
2019 ◽  
Vol 19 (2) ◽  
pp. 374 ◽  
Author(s):  
Ayoub Lahlalia ◽  
Olivier Le Neel ◽  
Ravi Shankar ◽  
Siegfried Selberherr ◽  
Lado Filipovic
Keyword(s):  
Metal Oxide ◽  
Power Consumption ◽  
Low Power ◽  
Gas Sensor ◽  
High Sensitivity ◽  
Fast Response ◽  
Low Power Consumption ◽  
Response Characteristics ◽  
The Impact ◽  
Semiconducting Metal Oxide

Semiconducting metal oxide (SMO) gas sensors were designed, fabricated, and characterized in terms of their sensing capability and the thermo-mechanical behavior of the micro-hotplate. The sensors demonstrate high sensitivity at low concentrations of volatile organic compounds (VOCs) at a low power consumption of 10.5 mW. In addition, the sensors realize fast response and recovery times of 20 s and 2.3 min, respectively. To further improve the baseline stability and sensing response characteristics at low power consumption, a novel sensor is conceived of and proposed. Tantalum aluminum (TaAl) is used as a microheater, whereas Pt-doped SnO2 is used as a thin film sensing layer. Both layers were deposited on top of a porous silicon nitride membrane. In this paper, two designs are characterized by simulations and experimental measurements, and the results are comparatively reported. Simultaneously, the impact of a heat pulsing mode and rubber smartphone cases on the sensing performance of the gas sensor are highlighted.

Electrospun Electroactive Polymer and Metal Oxide Nanofibers for Chemical Sensor Applications

2010 ◽  
Author(s):  
Jonas Flueckiger ◽  
Frank K. Ko ◽  
Karen C. Cheung
Keyword(s):  
Metal Oxide ◽  
Chemical Sensor ◽  
Response Times ◽  
Electrical Characterization ◽  
Volume Ratio ◽  
High Sensitivity ◽  
Fast Response ◽  
Sensor Applications ◽  
Tio2 Nanofiber ◽  
Good Signal

We present the fabrication of a polymer blend PANi/PEO nanofiber based sensor as well as a metal oxide TiO2 nanofiber based sensor. Electrospinning was used for the fabrication of the electroactive nanofibers. The conductivity of those fibers is highly sensitive to the chemical environment and is modified through the adsorption of different species. Used as a chemiresistor the nanofibers offer a higher sensitivity than thin films due to the increased surface to volume ratio. Impedance spectroscopy was used for electrical characterization of the fibers showing high sensitivity. Preliminary measurements of the sensors dynamic response when exposed to alternating chemical environments showed fast response times and good signal stability.

Dynamic Buckling of Single-Walled Carbon Nanotubes under Axial Impact Loading

2013 ◽  
Vol 444-445 ◽  
pp. 178-182
Author(s):  
Chuan An Xiong ◽  
Wu Gui Jiang
Keyword(s):  
Carbon Nanotubes ◽  
Finite Element ◽  
Stress Wave ◽  
Single Walled Carbon Nanotubes ◽  
Stress Wave Propagation ◽  
Buckling Mode ◽  
Single Walled Carbon ◽  
Finite Element Software ◽  
Walled Carbon Nanotubes ◽  
The Impact

Based on the Budiansky-Roth motion criterion, a thin cylinder shell finite element model is established using the finite element software (ABAQUS) to systemically investigate the dynamic bucking behavior of single-walled carbon nanotubes, which is validated by the molecular dynamic model. It is shown that both the magnitude and duration of the impact load have a great influence on the critical buckling load. By comparing the buckling modes, it can be found that the stress wave propagation plays an important role on the buckling deformation. A local axisymmetrical buckling mode is observed at the beginning and then an asymmetrical buckling mode occurs because of the stress wave superposition.

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