scholarly journals Microscale local strain gauges based on visible micro-disk lasers embedded in a flexible substrate

2018 ◽  
Vol 26 (13) ◽  
pp. 16797 ◽  
Author(s):  
Taojie Zhou ◽  
Jie Zhou ◽  
Yuzhou Cui ◽  
Xiu Liu ◽  
Jiagen Li ◽  
...  
Keyword(s):  
Flexible Substrate ◽  
Local Strain ◽  
Strain Gauges

Enhanced Instruction of Engineering Mechanics Using Curvature Experiments

2009 ◽  
Author(s):  
Byron L. Newberry
Keyword(s):  
Low Cost ◽  
Structural Response ◽  
Local Strain ◽  
Strain Gauges ◽  
Local Curvature ◽  
Post Process ◽  
Single Use ◽  
Strain Stress ◽  
Engineering Mechanics ◽  
Point Data

Resistive strain gauges are the most commonly used experimental devices for stress analysis. Their versatility stems from their ability to directly measure local strain on the surface of a structure, almost regardless of geometry. This strength can represent an educational limitation, however. Measurements made using strain gauges tend to provide results without students assessing or understanding the global structural response; limiting the insight gained and the instructional value of the experiment. Herein a low-cost device is presented that allows accurate measurement of local curvature in a beam. Once the local curvature is known, the elastic equations governing the beam may be used to calculate the local strain, stress, and deflection. The educational strength of the device is that students are forced to understand the interrelation of stress, strain, and deflection to post-process the experimental results. The device, though limited to beam geometries, has proven effective in helping students master engineering mechanics. It also allows investigation of the entire beam without added expense; as the device is not permanently affixed to one location. This is a significant advantage compared to strain gauges that provide only point data and are single-use. Details of the device itself, how it has been incorporated into the curriculum, and data assessing its effectiveness within a junior-level course are presented.

scholarly journals Use of Particle Image Velocimetry (PIV) technique to measure strains in geogrids

2019 ◽  
Vol 92 ◽  
pp. 12007
Author(s):  
Chaminda Gallage ◽  
Chamara Jayalath
Keyword(s):  
Tensile Strength ◽  
Retaining Wall ◽  
Local Strain ◽  
Tensile Tests ◽  
Experimental Program ◽  
Strain Gauges ◽  
Data Logging ◽  
Piv Technique ◽  
Image Velocimetry ◽  
Secant Stiffness

Geosynthetics are widely used in Geotechnical Engineering to reinforce soil/gravel in pavements, retaining wall backfills, and embankments. It is important to measure strains in geogrids in the determination of their strength parameters such as tensile strength and secant stiffness, and in evaluating their performances in geogrid-reinforced structures. Strain gauges are commonly used in measuring strains in geogrids. However, it is important to verify the strains measured by strain gauges as these strains are affected by the data logging device, gauge factors, quality of bonding between grain gauge and geogrid, and temperature. Therefore, this study was conducted to verify the performance of strain gauges attached to Geogrids and also to investigate the possibility of using PIV technique and GeoPIV-RG software to measure the local strains developed in a geogrid specimen under tensile testing in the laboratory. In the experimental program of this study, six composite geogrid specimens were tested for tensile strength (wide-width tensile tests) while measuring/calculating its tensile strain by using strain gauges attached to the specimens, Geo-PIV-RG analysis and crosshead movements of Instron apparatus. Good agreement between the strains obtained from strain gauges and geoPIV-RG analysis was observed for all the tests conducted. These results suggest that the PIV technique along with geoPIV-RG program can effectively be used to measure the local strain of geogrids in the laboratory tests. It was also able to verify that properly installed strain gauges are able to measure strain in the geogrids which are used in the field applications.

Differences between static and dynamic elastic moduli: Importance of experimental methods

2020 ◽  
Author(s):  
Elisabeth Bemer ◽  
Noalwenn Dubos-Sallée ◽  
Patrick N. J. Rasolofosaon
Keyword(s):  
Bulk Modulus ◽  
Young’S Modulus ◽  
Elastic Moduli ◽  
Young's Modulus ◽  
Local Strain ◽  
Experimental Methods ◽  
Triaxial Tests ◽  
Strain Gauges ◽  
Strain Measurements ◽  
Dynamic Elastic Moduli

<p>The differences between static and dynamic elastic moduli remain a controversial issue in rock physics. Various empirical correlations can be found in the literature. However, the experimental methods used to derive the static and dynamic elastic moduli differ and may entail substantial part of the discrepancies observed at the laboratory scale. The representativeness and bias of these methods should be fully assessed before applying big data analytics to the numerous datasets available in the literature.</p><p>We will illustrate, discuss and analyze the differences inherent to static and dynamic measurements through a series of triaxial and petroacoustic tests performed on an outcrop carbonate. The studied rock formation is Euville limestone, which is a crinoidal grainstone composed of roughly 99% calcite and coming from Meuse department located in Paris Basin. Sister plugs have been cored from the same quarry block and observed under CT-scanner to check their homogeneity levels.</p><p>The triaxial device is equipped with an internal stress sensor and provides axial strain measurements both from strain gauges glued to the samples and LVDTs placed inside the confinement chamber. Two measures of the static Young's modulus can thus be derived: the first one from the local strain measurements provided by the strain gauges and the second one from the semi-local strain measurements provided by the LVDTs. The P- and S-wave velocities are measured both through first break picking and the phase spectral ratio method, providing also two different measures of the dynamic Young's modulus.</p><p>The triaxial tests have been performed in drained conditions and the measured static elastic moduli correspond to drained elastic moduli. The petroacoustic tests have been performed using the fluid substitution method, which consists in measuring the acoustic velocities for various saturating fluids of different bulk modulus. No weakening or dispersion effects have been observed. Gassmann's equation can then be used to derive the dynamic drained elastic moduli and the solid matrix bulk modulus, which is otherwise either taken from the literature for pure calcite or dolomite samples, or computed using Voigt-Reuss-Hill or Hashin-Shtrikman averaging of the mineral constituents.</p><p>For the studied carbonate formation, we obtain similar values for static and dynamic elastic moduli when derived from careful lab experiments. Based on the obtained results, we will finally make recommendations, emphasizing the necessity of using relevant experimental techniques for a consistent characterization of the relation between static and dynamic elastic moduli.</p>

Nanoscale strain gauges composed of microdisk lasers embedded in a flexible substrate

2018 ◽  
Author(s):  
Taojie Zhou ◽  
Jie Zhou ◽  
Yuzhou Cui ◽  
Xiu Liu ◽  
Zhaoyu Zhang
Keyword(s):  
Flexible Substrate ◽  
Strain Gauges ◽  
Microdisk Lasers

scholarly journals The Behavior of a Thread-Bar Grouted Anchor in Soils from Local Strain Monitoring

2020 ◽  
Vol 10 (20) ◽  
pp. 7194
Author(s):  
Paolo Ruggeri ◽  
Viviene M. E. Fruzzetti ◽  
Giuseppe Scarpelli
Keyword(s):  
Shear Strength ◽  
Load Capacity ◽  
Poor Performance ◽  
Local Strain ◽  
International Standards ◽  
Strain Gauges ◽  
Fixed Length ◽  
Strain Monitoring ◽  
Sand Deposit ◽  
Low Shear

International standards discourage the use of grouted anchors with a fixed length exceeding 10 m. However, grouted anchors with a fixed length between 10 and 20 m are frequently used in Italy to transfer high loads to ground with poor geotechnical properties. This paper presents the results of investigation tests on an anchor with a length of 36 m, of which 18 m is fixed, sloping 40° from the horizontal; the anchor is comprised of a reinforced thread-bar which was instrumented with strain gauges and founded in nonhomogeneous ground, a sand deposit followed by marly clay. The test aimed at investigating the progressive mobilization of the shear strength along the foundation. The results indicate a very low shear strength offered by the sand, probably disturbed by the drilling, and an unusually fast mobilization of the shear strength in the marly clay at the deep end of the anchor. The results are particularly useful to identify the reasons for the observed poor performance of the grouted anchor. In particular, the study once again made it clear how important the influence of the execution details on reaching the expected load capacity may be, and likewise the practice of investigation tests on suitably instrumented test anchors.

scholarly journals Nanowire Ring Embedded in a Flexible Substrate for Local Strain Detection

Materials ◽  
2020 ◽  
Vol 13 (2) ◽  
pp. 347
Author(s):  
Shengkun Li ◽  
Yue Qin ◽  
Xin Li ◽  
Yuejin Zhao
Keyword(s):  
Detection System ◽  
Structural Parameters ◽  
Flexible Substrate ◽  
Ring Cavity ◽  
Local Strain ◽  
Strain Sensors ◽  
Resonant Wavelength ◽  
Gauge Factor ◽  
Light Sources ◽  
End To End

Optical sensing has attracted more and more attention in recent years with the advance in planar waveguide fabrication processes. The photon, as a carrier of information in sensing areas, could have a better performance than electrons. We propose a novel end-to-end ring cavity to fabricate sensitive units of a strain sensor. We then propose a method of combining a flexible substrate with an end-to-end semiconductor nanowire ring cavity to fabricate novel strain sensors. We used a tuning resonant wavelength detected by a homebuilt excitation and detection system to measure applied strain. The resonant wavelength of the strain gauge was red-shift and linear tuned with increasing strain. The gauge factor was about 50, calculated through experiments and theory, and Q was 1938, with structural parameters L = 70 µm and d = 1 µm. The high sensitivity makes it possible to measure micro deformation more accurately. End-to-end coupling active nanowire waveguides eliminate the shortcomings of side by side coupling structures, which have the phasing shift with no minor optical density loss. This resonator in flexible substrates could be used not only as on-chip strain sensors for micro or nano deformation detecting but also as tunable light sources for photonic integrated circuits.

scholarly journals Rock Triaxial Tests: Global Deformation vs Local Strain Measurements—Implications

2021 ◽  
Author(s):  
A. Perbawa ◽  
E. Gramajo ◽  
T. Finkbeiner ◽  
J. C. Santamarina
Keyword(s):  
Wave Propagation ◽  
Local Strain ◽  
Confining Pressure ◽  
Hysteretic Behavior ◽  
Triaxial Tests ◽  
Strain Gauges ◽  
Eagle Ford Shale ◽  
Strain Measurements ◽  
Lower Strain ◽  
Global Deformation

AbstractAccurate stress–strain measurements in triaxial tests are critical to compute reliable mechanical parameters. We focus on compliance at the interfaces between the specimen and endcaps, and test specimens under various triaxial conditions using different instrumentation protocols. The tested materials include aluminum, Eagle Ford shale, Berea sandstone, and Jubaila carbonate. Results obtained following common practice reveal that surface roughness at the specimen-endcap interfaces leads to marked seating effects, affects all cap-to-cap based measurements and hinders ultrasonic energy transmission. In particular, cap-to-cap deformation measurements accentuate hysteretic behavior, magnify biases caused by bending and tilting (triggered by uneven surfaces and misalignment), and affect the estimation of all rock parameters, from stiffness to Biot’s α-parameter. Higher confining pressure diminishes seating effects. Local measurements using specimen-bonded strain gauges are preferred (Note: mounting strain gauges on sleeves is ill-advised). We confirm that elastic moduli derived from wave propagation measurements are higher than quasi-static moduli determined from local strain measurements using specimen-bonded strain gauges, probably due to the lower strain level in wave propagation and preferential high-velocity travel path for first arrivals.

scholarly journals Cantilever-based microring lasers embedded in a deformable substrate for local strain gauges

AIP Advances ◽  
2018 ◽  
Vol 8 (7) ◽  
pp. 075306 ◽  
Author(s):  
Taojie Zhou ◽  
Xiu Liu ◽  
Yuzhou Cui ◽  
Yuansen Cheng ◽  
Xuan Fang ◽  
...  
Keyword(s):  
Local Strain ◽  
Strain Gauges

scholarly journals Local strain gauge based on the nanowires ring resonator embedded in a flexible substrate

2020 ◽  
Vol 15 (14) ◽  
pp. 1028-1032
Author(s):  
Shengkun Li ◽  
Xin Li ◽  
Yue Qin ◽  
Yuejin Zhao
Keyword(s):  
Strain Gauge ◽  
Ring Resonator ◽  
Flexible Substrate ◽  
Local Strain

scholarly journals Concentric Array of Printed Strain Sensors for Structural Health Monitoring

Sensors ◽  
2020 ◽  
Vol 20 (7) ◽  
pp. 1997 ◽  
Author(s):  
Daniel Zymelka ◽  
Kazuyoshi Togashi ◽  
Takeshi Kobayashi
Keyword(s):  
Sensor Array ◽  
Crack Formation ◽  
Flexible Substrate ◽  
Local Strain ◽  
Strain Sensors ◽  
Civil Infrastructure ◽  
Civil Structures ◽  
Sensing Systems ◽  
Potential Applications ◽  
Crack Tips

Civil infrastructure is expanding around the world. The ever-growing trend toward urbanization drives the demand for new investments. However, the new constructions and gradual deterioration of those already existing, especially bridges, give rise to concerns about their proper maintenance. To improve safety and drive down maintenance costs of civil structures, there is a need for inexpensive sensing systems capable of reliable and automated monitoring. In this study, we present a new concept of thin-film strain sensors arranged in an array with a concentric layout that is incorporated into a flexible substrate sheet. The designed sensor array is intended to analyze strains in the proximity of round holes made at the crack tips, found in the investigated construction elements of civil structures. In this study, the performance of the sensor array was demonstrated using measurements taken on a highway bridge in one of the largest cities in Japan. We show that it can measure local strain distribution and indicate a region with risk for crack formation. The demonstrated results show new area of potential applications for the printed strain sensors in monitoring civil structures.

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