Tesi: "Strain" – Grafiati

1

Koob, Christopher E. "High temperature fiber optic strain sensing". Thesis, This resource online, 1991. http://scholar.lib.vt.edu/theses/available/etd-02132009-171339/.

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2

Chen, Yuejian. "High-strain, high-strain-rate deformation of tantalum /". Diss., Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 1998. http://wwwlib.umi.com/cr/ucsd/fullcit?p9828890.

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3

Gosling, T. J. "Strain relaxation via dislocation formation in strained semiconductor structures". Thesis, University of Bath, 1994. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.387390.

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4

Pani´c, Nebojsa. "High strain rate-induced failure in steels at high shear strains". Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1999. http://www.collectionscanada.ca/obj/s4/f2/dsk1/tape8/PQDD_0006/MQ45106.pdf.

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5

Julian, Michael Robert. "Material characterization of viscoelastic polymeric molding compounds". Connect to resource, 1994. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1137616726.

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Abstract (sommario):

Thesis (M.S.)--Ohio State University, 1994.
Advisors: Vernal H. Kenner and Carl H. Popelar, Dept. of Engineering Mechanics. Includes bibliographical references (leaf 106). Available online via OhioLINK's ETD Center

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6

Smith, Byron L. "Mean strain effects on the strain life fatigue curve". Thesis, Monterey, Calif. : Springfield, Va. : Naval Postgraduate School ; Available from National Technical Information Service, 1993. http://handle.dtic.mil/100.2/ADA267211.

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7

Larour, Patrick [Verfasser]. "Strain rate sensitivity of automotive sheet steels: influence of plastic strain, strain rate, temperature, microstructure, bake hardening and pre-strain / vorgelegt von Patrick Larour". Aachen : Shaker, 2010. http://d-nb.info/1007085649/34.

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8

Javornik, Ana. "Tissue velocity, strain und strain rate bei Hunden mit Mitralklappenendokardiose". Diss., [S.l.] : [s.n.], 2007. http://edoc.ub.uni-muenchen.de/archive/00007454.

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9

Barraclough, Thomas William. "Strain softening and strain localisation in irreversible deformation of snow". Thesis, University of Edinburgh, 2015. http://hdl.handle.net/1842/16218.

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The aim of this work was to visualise heterogeneous deformation in snow under controlled laboratory conditions. Heterogeneous deformation was observed for both homogenous and heterogeneous loading conditions. Understanding deformation of snow is important in many scientific fields including vehicle traction, avalanche forecasting, and winter sports. This thesis investigates the deformation behaviour of snow on the centimetre scale under moderate strain rates (0.005 to 0.1 s-1) when subject to one-dimensional compression or to indentation. In order to allow controlled and repeatable snow deformation experiments, a new type of artificial snow was developed. This snow type was examined by low temperature scanning electron microscopy and by traditional avalanche observer’s methodology. Penetrometer experiments were conducted on the artificial snow and on natural seasonal snow in Scotland. The two snow types were found to be similar: results obtained on artificial snow are thus applicable to natural snow. A reproducible technique of manufacture and a thorough characterisation of the artificial snow are presented. One-dimensional compression experiments were conducted on the artificial snow. The experiments were in confined compression in a specially constructed apparatus, designed to provide for back-lit photography. Images were taken at 0.25 second intervals and analysed using digital image correlation, thus providing 2D strain fields. With careful control of photographic parameters, it is demonstrated that process of applying tracer substances to the snow is not necessary, thus allowing an unprecedented resolution. Spontaneously-forming strain localisations were observed for the first time, indicating strain softening behaviour. Damage was observed to propagate through the specimen as a moving front, resembling a wave. The force required to propagate the front remained nearly constant until the whole specimen was compacted, at which point a new front formed and the process repeated. The experimental method was extended to 2D indention experiments with a range of sizes and shapes of indenter. Complex deformation fields were observed, extending up to 6 times the width of the indenter on each side. Observed deformation included tensile tearing as well as compression and shear. The maximum local strain achieved in the indentation experiments was similar to that achieved by the first compaction front in one-dimensional compression. The work here presented has implications for snow deformation generally: strain localisation introduces a characteristic length, which may prevent scaling of models or results. The indentation results are particularly relevant to snow penetrometry, where indentation experiments are used to try and extract microstructural information from buried snow layers for the purpose of avalanche prediction. The common assumption that the penetrometer interacts only with snow very close to its tip may need to be reconsidered.

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10

Magoda, Cletus Mathew. "High strain-rate compressive strain of welded 300W asteel joints". Thesis, Cape Peninsula University of Technology, 2011. http://hdl.handle.net/20.500.11838/1248.

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A Thesis Submitted Towards the Partial Fulfilment Degree of Master of Technology (M.Tech.) FACULTY OF ENGINEERING MECHANICAL ENGINEERING DEPARTMENT Cape Peninsula University of Technology 2011
The split Hopkinson pressure bar (SHPB) test is the most commonly used method for determining material properties at high rates of strain. The theory governing the specifics of Hopkinson bar testing has been around for decades; however, it has only been for the last decade or so that significant data processing advancements have been made. It is the intent of this thesis to offer the insight of application of SHPB to determine the compressive dynamic behaviour for welded low carbon steel (mild steel). It also focuses on the tensile behaviour for unheat-treated and heat-treated welded carbon steel. The split Hopkinson Pressure bar apparatus consists of two long slender bars that sandwich a short cylindrical specimen between them. By striking the end of a bar, a compressive stress wave is generated that immediately begins to traverse towards the specimen. Upon arrival at the specimen, the wave partially reflects back towards the impact end. The remainder of the wave transmits through the specimen and into the second bar, causing irreversible plastic deformation in the specimen. It is shown that the reflected and transmitted waves are proportional to the specimen's strain rate and stress, respectively. Specimen strain can be determined by integrating the strain rate. By monitoring the strains in the two bars and the specimen's material, stress-strain properties can be calculated. Several factors influence the accuracy of the results, including the size and type of the data logger, impedance mismatch of the bars with the specimens, the utilization of the appropriate strain gauges and the strain amplifier properties, among others. A particular area of advancement is a new technique to determine the wave's velocity in the specimen with respect to change in medium and mechanical properties, and hence increasing the range of application of SHPB. It is shown that by choosing specimen dimensions based on their impedance, the transmitted stress signal-to-noise ratio can be improved. An in depth discussion of realistic expectations of strain gages is presented, along with closed form solutions validating any claims. The thesis concludes with an analysis of experimental and predicted results. Several recommendations and conclusions are made with regard to the results obtained and areas of improvement are suggested in order to achieve accurate and more meaningful results.

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11

Yao, Shulong. "Highly Stretchable Miniature Strain Sensor for Large Dynamic Strain Measurement". Thesis, University of North Texas, 2016. https://digital.library.unt.edu/ark:/67531/metadc849674/.

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This thesis aims to develop a new type of highly stretchable strain sensor to measure large deformation of a specimen subjected to dynamic loading. The sensor was based on the piezo-resistive response of carbon nanotube(CNT)/polydimethysiloxane (PDMS) composites thin films, some nickel particles were added into the sensor composite to improve the sensor performance. The piezo-resistive response of CNT composite gives high frequency response in strain measurement, while the ultra-soft PDMS matrix provides high flexibility and ductility for large strain measuring large strain (up to 26%) with an excellent linearity and a fast frequency response under quasi-static test, the delay time for high strain rate test is just 30 μs. This stretchable strain sensor is also able to exhibit much higher sensitivities, with a gauge factor of as high as 80, than conventional foil strain gauges.

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12

Clark, Craig B. "Strain and strain rate regulation of skeletal muscle in vitro /". Diss., Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 2000. http://wwwlib.umi.com/cr/ucsd/fullcit?p9970679.

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13

Askling, Carl. "Hamstring muscle strain". Doctoral thesis, Swedish School of Sport and Health Sciences, GIH, Laboratory for Biomechanics and Motor Control, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:gih:diva-425.

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Background: Acute hamstring strains are common injuries in different sports. They are often serious, causing long rehabilitation times and a proneness for re-injury. Preliminary observations indicate that the injuries can be of at least two types, one occurring during high-speed running and the other during motions where the hamstring muscles reach extreme lengths.

Aims: To investigate the possible existence of different types of acute hamstring strains in two specific athletic groups, namely sprinters and dancers, as well as the generality of these findings in other sports.

Methods: In the first project, 18 sprinters and 15 dancers with acute first time hamstring strains were prospectively included. All subjects were examined, clinically and with magnetic resonance imaging (MRI), on 4 occasions after injury: at day 2-4, 10, 21 and 42. The follow-up period was 2 years. In the second project, 30 subjects from 21 different sports were prospectively included. All subjects were examined clinically and with MRI. The follow-up period lasted until the subjects returned to sport or finished their sport activity due to the injury.

Results: All sprinters sustained their injuries during competitive high-speed running. In contrast, all dancers encountered their injuries during slow-speed stretching type of exercises. The initial loss of strength and flexibility was significantly greater in sprinters than in dancers. At 42 days after injury, both groups could perform more than 90% of the test values of the uninjured leg. All the sprinters’ injuries were primarily located in biceps femoris long head, whereas the dancers’ injuries were mainly (87%) involving the proximal free tendon of semimembranosus. For the sprinters, involvement of the proximal free tendon, as estimated by MRI, and proximity to the ischial tuberosity, as estimated both by palpation and MRI, were associated with significantly longer time to return to pre-injury level. In the dancers, there were no significant correlations between clinical or MRI parameters and time to return to per-injury level. The time to pre-injury level was significantly longer (median 50 weeks, range 30-76) for the dancers compared to the sprinters (16, 6-50). In the second project, all injuries occurred during movements reaching a position with combined extensive hip flexion and knee extension. They were all located close to the ischial tuberosity and 83% involved the proximal free tendon of semimembranosus. Fourteen subjects (47%) decided to end their sport activity and for the remaining 16 subjects the median time back to sport was 31 (range 9-104) weeks. There were no significant correlations between clinical and MRI parameters and time to return to sport.

Conclusions: There seems to be a link between the injury situation and the two types of acute hamstring strain in sprinters and dancers with respect to clinical findings, injury location, muscles and tissues involved, and time to return to pre-injury level. Proximity of the injury to the ischial tuberosity, as estimated both by palpation and MRI, is associated with longer recovery time. Also in other sports, an injury situation where the hamstrings reach extensive lengths caused a specific injury to the proximal posterior thigh similar to that described in dancers. Due to the prolonged recovery time associated with this type of injury, correct diagnosis based on history, clinical and MRI investigation, and adequate information to the athletes are essential.

För att beställa tryckta exemplar av avhandlingen kontakta Carl Askling, carl.askling@gih.se

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14

Liu, Min. "A Three-Dimensional Hyper-Viscoelasticity Constitutive Model for the Dynamic Response of Rubber". University of Akron / OhioLINK, 2007. http://rave.ohiolink.edu/etdc/view?acc_num=akron1185546966.

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15

Ahmed, Shamheed. "Small strain behaviour of sand under triaxial and plane strain conditions". Thesis, University of Leeds, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.436380.

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16

Zhou, Qing 1964. "Analysis of plane strain necking and fracture in strain hardening materials". Thesis, Massachusetts Institute of Technology, 1994. http://hdl.handle.net/1721.1/11636.

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17

McKnight, Nathan L. "Strain and strain rate mechanotransduction in human vascular smooth muscle cells /". Diss., Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 2002. http://wwwlib.umi.com/cr/ucsd/fullcit?p3076345.

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18

Janezic, Sandra, Valerija Zidaric, Bart Pardon, Alexander Indra, Branko Kokotovic, Jose Blanco, Christian Seyboldt et al. "International Clostridium difficile animal strain collection and large diversity of animal associated strains". BioMed Central, 2014. http://hdl.handle.net/10150/610058.

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BACKGROUND:Clostridium difficile is an important cause of intestinal infections in some animal species and animals might be a reservoir for community associated human infections. Here we describe a collection of animal associated C. difficile strains from 12 countries based on inclusion criteria of one strain (PCR ribotype) per animal species per laboratory.RESULTS:Altogether 112 isolates were collected and distributed into 38 PCR ribotypes with agarose based approach and 50 PCR ribotypes with sequencer based approach. Four PCR ribotypes were most prevalent in terms of number of isolates as well as in terms of number of different host species: 078 (14.3% of isolates
4 hosts), 014/020 (11.6%
8 hosts)
002 (5.4%
4 hosts) and 012 (5.4%
5 hosts). Two animal hosts were best represented
cattle with 31 isolates (20 PCR ribotypes
7 countries) and pigs with 31 isolates (16 PCR ribotypes
10 countries).CONCLUSIONS:This results show that although PCR ribotype 078 is often reported as the major animal C. difficile type, especially in pigs, the variability of strains in pigs and other animal hosts is substantial. Most common human PCR ribotypes (014/020 and 002) are also among most prevalent animal associated C. difficile strains worldwide. The widespread dissemination of toxigenic C. difficile and the considerable overlap in strain distribution between species furthers concerns about interspecies, including zoonotic, transmission of this critically important pathogen.

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19

Cai, Jing. "Properties of heterogeneous energetic materials under high strain, high strain rate deformation". Connect to a 24 p. preview or request complete full text in PDF format. Access restricted to UC campuses, 2007. http://wwwlib.umi.com/cr/ucsd/fullcit?p3274695.

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Thesis (Ph. D.)--University of California, San Diego, 2007.
Title from first page of PDF file (viewed October 2, 2007). Available via ProQuest Digital Dissertations. Vita. Includes bibliographical references (p. 161-172).

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20

Alinaghian, Yaser. "The Effect of Pre-strain and Strain Path Changes on Ductile Fracture". Thèse, Université d'Ottawa / University of Ottawa, 2013. http://hdl.handle.net/10393/23917.

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Industrial metal forming operations generally require several deformation steps in order to create the final product. The mechanical behavior of materials undergoing strain path changes can be very different from those deformed in a given direction to fracture. The work presented here employed laser drilled model materials to better understand the effect of pre-strains and strain path changes on void growth and linkage leading to fracture is studied. The experimental results show that increasing pre-strain results in faster void growth which was justified in terms work hardening rate in the sample. Scanning electron microscope images revealed that the ductility of the sample decreased with increasing pre-strain but only slightly compared to the large decrease in far field strain at failure. This suggests that pre-strain affects strain localization significantly and to a lesser extent the ductility. Finally a finite element model has been built to predict the linkage between voids.

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21

Shim, JongMin 1975. "Finite strain behavior of polyurea for a wide range of strain rates". Thesis, Massachusetts Institute of Technology, 2009. http://hdl.handle.net/1721.1/58458.

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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Civil and Environmental Engineering, February 2010.
Cataloged from PDF version of thesis.
Includes bibliographical references (p. 101-112).
Polyurea is a special type of elastomer that features fast setting time as well as good chemical and fire resistance. It has also good mechanical properties such as its high toughness-to-density ratio and high strain rate-sensitivity, so its application is recently extended to structural purpose to form sandwich-type or multi-layered plates. Those structures can be used for retrofitting of military vehicles and historic buildings, absorbing energy during structural crash. In order to investigate its behavior of hysteresis as well as rate-sensitivity, three different testing systems are used to cover a wide range of strain rates up to strain of 100%. In view of impact and blast events, the virgin state of polyurea is considered throughout the experiments. First, a hydraulic universal testing machine is used to perform uniaxial compressive loading/unloading tests in order to investigate its hysteresis behavior at low strain rates (0.001/s to 10/s). Second, two distinct gas-gun split Hopkinson pressure bar [SHPB] systems are employed to cover high strain rates: a nylon bar system (700/s to 1200/s) and an aluminum bar system (2300/s to 3700/s). Lastly, the rate-sensitivity for intermediate strain rates (10/s to 1000/s) is characterized using a modified SHPB system.
(cont.) The device is composed of a hydraulic piston along with nylon input and output bars. A finite strain constitutive model of polyurea is presented in order to predict the hysteresis and rate-sensitivity behavior. The 1-D rheological concept of two Maxwell elements in parallel is employed within the framework of the multiplicative decomposition of the deformation gradient. Model parameters are calibrated based on the uniaxial compressive tests at various rates. The corresponding algorithms is implemented as a user-defined material subroutine VUMAT for ABAQUS/Explicit, and used to predict the response of polyurea. The proposed constitutive model reasonably captures the experimentally observed asymmetric rate-sensitivity and stress-relaxation behavior: strong rate-sensitivity and large amount of stress relaxation during loading phase, but weak rate-sensitivity and smaller amount of stress relaxation during unloading phase. In order to validate the proposed model, various dynamic punching tests are performed, and their results are well compared with the model predictions during loading although the prediction of unloading behavior can be further improved.
by Jongmin Shim.
Ph.D.

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22

Ouyang, Xin. "CONSTITUTIVE EQUATIONS OF RUBBER UNDER LARGE TENSILE STRAIN AND HIGH STRAIN RATES". University of Akron / OhioLINK, 2006. http://rave.ohiolink.edu/etdc/view?acc_num=akron1154146622.

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23

Episcopo, Val. "Strain and weight change". Related electronic resource: Current Research at SU : database of SU dissertations, recent titles available full text, 2009. http://wwwlib.umi.com/cr/syr/main.

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24

Valnes, Lars Magnus. "Accumulated Plastic Strain Program". Thesis, Norges teknisk-naturvitenskapelige universitet, Institutt for fysikk, 2014. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-26981.

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In this thesis we will look at the implementation and results of the APS program. The program computes the accumulated plastic strain in a umbilical tube for the deformations axial tension, bending and internal pressure. The computation is based on solving incremental problems with the finite element method and the return-mapping algorithm. The return-mapping algorithm encountered convergence failure for large strain increments, this was solved by using the strain increment of $1.0e\sp{-4}\%$.The implementation of axial tension and bending was consistent with the results provided by Nexans Norway.While the plastic behaviour of the internal pressure proved to be more complex, so the implementation requires improvement.

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25

Li, Wenbin Ph D. Massachusetts Institute of Technology. "High Deviatoric Strain Engineering/". Thesis, Massachusetts Institute of Technology, 2015. http://hdl.handle.net/1721.1/98734.

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Thesis: Ph. D., Massachusetts Institute of Technology, Department of Materials Science and Engineering, 2015.
Cataloged from PDF version of thesis.
Includes bibliographical references (pages 157-171).
The structure of a material can be tuned reversibly or irreversibly by imposing elastic or inelastic strain, leading to change of properties. This defines the concept of strain engineering, which includes both elastic strain engineering (ESE) and inelastic strain engineering (ISE). In this thesis, we study ESE and ISE by deviatoric (nonhydrostatic) strain. For ESE, we model how imposition of slowly-varying inhomogeneous elastic strain can induce the electronic structure changes of semiconductor crystals. The strain-dependent shift of valence and conduction band energy levels leads to the formation of electronic and hole bound states in in-homogeneously strained crystals, whose energy levels can be dynamically tuned by the strain field. We developed a new envelope function method with strain-parametrized basis set that can solve the electronic structure of such inhomogeneously strained crystals by incorporating the local electronic structure information obtained from unit-cell level first-principles calculation of homogeneously strained crystals. For ISE, we study the deviatoric strain induced phase transformation and internal structure evolution in soft matter systems. Using largescale molecular dynamics simulation, we demonstrate that controlled sintering of the nanocrystals in self-assembled superlattices of alkanethiol-passivated gold nanoparticles can happen at room temperature through deviatoric stress-induced displacement of the organic ligands. We find that combining a hydrostatic pressure of order several hundred megapascal and a critical deviatoric stress along the nearest-neighbor direction of gold nanoparticle superlattices leads to ordered sintering of gold nanocrystals and the formation of gold nanowire arrays. Similar phenomena can happen in binary superlattices of gold and silver nanoparticles, and we predict the formation of gold-silver multijunction nanowire arrays through deviatoric-stress driven sintering of nanoparticles. We also simulate the plastic flow of two dimensional amorphous granular pillars subjected to athermal, uniaxial and quasistatic deformation. We find that for the athermal granular pillars under inhomogeneous load, the cumulative local deviatoric strains of particles with respect to their neighbors play the role of time in thermal systems, and drive the crossover of non-affine particle displacements from ballistic motion to diffusion. The result suggests that in disordered solids, deviatoric strain alone can drive particle diffusion even at zero vibrational temperature.
by Wenbin Li.
Ph. D.

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26

Lin, Charrissa Y. "Strain actuated aeroelastic control". Thesis, Massachusetts Institute of Technology, 1993. http://hdl.handle.net/1721.1/47318.

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27

Breland, Adrienne E. "A supervised strain classifier". abstract and full text PDF (free order & download UNR users only), 2008. http://0-gateway.proquest.com.innopac.library.unr.edu/openurl?url_ver=Z39.88-2004&rft_val_fmt=info:ofi/fmt:kev:mtx:dissertation&res_dat=xri:pqdiss&rft_dat=xri:pqdiss:1453199.

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28

Smith, Daniel Henlee. "Imposing Cyclic Strain on Osteogenic Stem Cells: The Effects of Strain Levels and Repetition of Cyclic Strain in an Implant Environment". MSSTATE, 2004. http://sun.library.msstate.edu/ETD-db/theses/available/etd-11112004-132423/.

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Bone and bone cells have been shown to respond to mechanical forces placed upon them. Particularly, strain plays an important role in osteogenic differentiation of marrow cells around artificial implants in bone. These strains, depending on their magnitude, duration, and repetition, can alter the proliferation and matrix synthesis of osteoblasts. To test how strain parameters influence osteoblast behavior, a four-point bending apparatus was used to impose cyclic strain on osteogenic stem cells isolated from rats and seeded on titanium plates. Cells were stimulated at 1 Hz for 15 minutes daily and compared to an unstrained control. Stimulation occurred at two magnitudes: 400 and 1000 micro-strain, and three levels of repetition: one, three, and five consecutive days. DNA, protein, alkaline phosphatase, and calcium levels were measured to determine the proliferation and matrix synthesis activity of the cells. No statistically significant effect was found for the tested parameters under these conditions.

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Fernandez, Lorences Jose O. "Crystallinity changes in PET and Nylon 11 with strain, strain rate and temperature". Thesis, Loughborough University, 1999. https://dspace.lboro.ac.uk/2134/32894.

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The mechanical properties of PET (widely used in bottles and synthetic fibres) and Nylon 11 (also used in the fabrication of synthetic fibres) were studied over several decades of strain rate at different temperatures in an effort to provide a more complete description of these materials behaviour. Processing techniques can be improved if such information is available. Tests were carried out using a conventional Hounsfield machine and two in-house-developed dropweight and a cross bow systems from 10°C to 200°C. The three systems enable true stress vs. true strain curves to be calculated.

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30

Johnson, Timothy Michael. "Strain Monitoring of Carbon Fiber Composite with Embedded Nickel Nano-Composite Strain Gage". BYU ScholarsArchive, 2011. https://scholarsarchive.byu.edu/etd/2622.

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Carbon fiber reinforced plastic (CFRP) composites have extensive value in the aerospace, defense, sporting goods, and high performance automobile industries. These composites have huge benefits including high strength to weight ratios and the ability to tailor their properties. A significant issue with carbon fiber composites is the potential for catastrophic fatigue failure. To better understand this fatigue, there is first a huge push to measure strain accurately and in-situ to monitor carbon fiber composites. In this paper, piezoresistive nickel nanostrand (NiNs) nanocomposites were embedded in between layers of carbon fiber composite for real time, in situ strain monitoring. Several different embedding methods have been investigated. These include the direct embedding of a patch of dry NiNs and the embedding of NiNs-polymer matrix nanocomposite patches which are insulated from the surrounding carbon fiber. Also, two different polymer matrix materials were used in the nanocomposite to compare the piezoresistive signal. These nanocomposites are shown to display repeatable piezoresistivity, thus becoming a strain sensor capable of accurately measuring strain real time and in-situ. This patch has compatible mechanical properties to existing advanced composites and shows good resolution to small strain. This method of strain sensing in carbon fiber composites is more easily implemented and used than other strain measurement methods including fiber Bragg grating and acoustic emissions. To show that these embedded strain gages can be used in a variety of carbon fiber components, two different applications were also pursued.

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Zaroulis, John Spyros. "Temperature, strain rate and strain state dependence of evolution of mechanical behavior and structure of poly(ethylene-terephthalate) with finite strain deformation". Thesis, Massachusetts Institute of Technology, 1995. http://hdl.handle.net/1721.1/11251.

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32

Turner, Jody Lee. "The Effect of Strain Path on Strain Induced Precipitation in a Model Microalloyed Steel". Thesis, University of Sheffield, 2009. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.511959.

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33

Wu, Xingdong. "Onset, propagation, and evolution of strain localization in undrained plane strain experiments on clay". Thesis, Kansas State University, 2016. http://hdl.handle.net/2097/32548.

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Master of Science
Civil Engineering
Dunja Peric
The conventional triaxial test is the primary laboratory test for determining the shear strength of soils. Geotechnical field conditions such as long earth dams, long embankments, long retaining walls, strip foundations, tunnels, and buried pipelines often experience plane strain states of stress. However, stress strain and load deformation responses in plane strain loading differ considerably from responses observed in the conventional triaxial test. Research has shown that soils loaded in a plane strain state are far more sensitive to imperfections than soils tested in a conventional triaxial device. Plane strain loading leads to material instability manifested as sudden localized failure, resulting in decreased load-carrying capacity of the soil and compromised geotechnical and civil infrastructures. Although previous studies have mostly focused on granular materials, this research investigated the plane strain response of clay. An undrained plane strain compression test program was devised to investigate the effects of past stress history and strain rates on strain localization in kaolin clay. Experiments were carried out in a plane strain (or biaxial) device at Northwestern University, Evanston, Illinois. Because the device was heavily internally instrumented, strain localization progress was closely monitored throughout each biaxial test. Clay response in the biaxial test demonstrated three phases: (1) a homogenous response, (2) the onset and propagation of strain localization, and (3) the evolution of strain localization as a shear band. The duration of each phase was determined for each test, and a Lagrange strain tensor was used to obtain the evolution of volumetric and shear strains at the level of a shear band for three tests. Results revealed the development of large strains in these mesoscale structures. Furthermore, evolution of Mohr-Coulomb effective shear strength parameters was traced throughout the propagation and evolution phases by using two different methods. It showed that in clay samples, unlike in granular materials, the post-peak plateau, which is reached by deviatoric stress, corresponds to friction values that are significantly lower than the critical state values. Other researchers who used scanning electron microscope and anisotropy of magnetic susceptibility detected a significant reorientation of clay particles inside shear bands. Their findings combined with findings in this study lead to the conclusion that the sub-meso scale mechanism responsible for large shear strains and a severe reduction in effective friction is a significant reorientation of clay particles inside shear band.

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Trausch-Giudici, Jolanda Luisa. "Stress-strain characterisation of seebodenlehm /". Zürich : IGT, Division of Geotechnical Engineering : vdf, Hochschulverlag AG an der ETH Zürich, 2004. http://opac.nebis.ch/cgi-bin/showAbstract.pl?u20=3728130036.

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35

Bråmå, Erik. "Strain Energy of Bézier Surfaces". Thesis, Linköpings universitet, Matematik och tillämpad matematik, 2018. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-145645.

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Abstract (sommario):

Bézier curves and surfaces are used to great success in computer-aided design and finite element modelling, among other things, due to their tendency of being mathematically convenient to use. This thesis explores the different properties that make Bézier surfaces the strong tool that it is. This requires a closer look at Bernstein polynomials and the de Castiljau algorithm. To illustrate some of these properties, the strain energy of a Bézier surface is calculated. This demands an understanding of what a surface is, which is why this thesis also covers some elementary theory regarding parametrized curves and surface geometry, including the first and second fundamental forms.

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36

Colson, Harry George. "Strain relaxation in semiconductor heterostructures". Thesis, University of Surrey, 1997. http://epubs.surrey.ac.uk/843607/.

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Abstract (sommario):

The strain relaxation behaviour of and oriented InxGa1-xAs layers grown on GaAs substrates has been investigated using surface profilometry and high resolution X-ray diffraction. The strain relaxation behaviour of single InxGa1-xAs layers (grown by various methods) has been studied using double crystal X-ray diffraction. The layer strain has been shown to be predictable, following the empirical relaxation law given by epsilonr = k/d where epsilonr is the residual strain, d is the layer thickness and k is a constant (= 0.84 nm +/- 0.18 nm). In addition, it is shown, using previously published data, that this law is applicable to other semiconductor alloy systems. Results show that the relaxation behaviour of oriented material is very similar to that of oriented material. However, the critical thickness is 1.23 times that for material in agreement with theory. It is shown that plastic relaxation of good quality epitaxially strained layers is accompanied by roughening of the surface in the form of striations and that the maximum striation height is always less than 20 nm regardless of layer thickness. Measurements of strain relaxation in multi-quantum well type samples show good agreement with a simple geometric theory in which the minimum barrier thickness needed to decouple strained layers of thickness hw is given as 0.62hw.

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37

Blackman, Lois. "Strain differentiation of Yersinia pestis". Thesis, University of Leicester, 2001. http://hdl.handle.net/2381/29822.

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Abstract (sommario):

Verification procedures are required to ensure compliance with the Biological and Toxins Weapons Convention (BTWC). Strain differentiation analysis may need to be performed on samples that do not harbour live bacteria and may contain other microorganisms. Thus the method employed must be non-culture based and specific to the bacterial species. Three Polymerase Chain Reaction (PCR) based assays were evaluated for their potential to specifically differentiate strains of Yersinia pestis. Two of the techniques, Insertion Sequence - Flanking Region Amplification PCR (IS-FRAP) and Variable Number of Tandem Repeats - PCR (VNTR-PCR), demonstrated specific and reproducible differentiation of a test panel of 84 Y. pestis isolates. These isolates included biotyped and/or ribotyped strains, previously untyped isolates and repetitive subcultures of Y. pestis CO92. Sites of chromosomal and plasmid insertion of the IS100 element were analysed by IS-FRAP. The amplification profiles divided the test panel isolates into 16 types. Two octonucleotide VNTR sequences were identified in the proximity of the same IS100 element. The observation of 11 alleles of VNTR-8A upstream of 4 alleles of VNTR-8B enabled the differentiation of the test panel isolates into 19 VNTR-PCR types. Strains isolated from similar geographical locations often displayed the same VNTR-PCR type. These PCR techniques were developed into prototype assays that may be suitable for the analysis of BTWC samples. Homologous sequences to the Y. pestis VNTR regions were analysed in Y. pseudotuberculosis strains. The octonucleotide sequence of VNTR-8A was not repeated in Y. pseudotuberculosis and was flanked by 361bp of DNA not identified in Y. pestis strains. Recombination events leading to the formation of the VNTR are hypothesised.

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38

Wan, Margaret. "Assessment of occupational heat strain". [Tampa, Fla] : University of South Florida, 2006. http://purl.fcla.edu/usf/dc/et/SFE0001661.

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39

Kageson-Loe, Nils Michael. "The strain behaviour of chalk". Thesis, Imperial College London, 1993. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.309215.

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40

Downes, James R. "Strain relaxation in semiconductor devices". Thesis, University of Surrey, 1995. http://epubs.surrey.ac.uk/773021/.

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Abstract (sommario):

Strained layers are incorporated into many electronic devices and particularly into semiconductor lasers. These strained layers can relax, both elastically and plastically, which often impairs the performance of the device. This thesis presents several methods for calculating elastic strain relaxation: a Fourierseries method for stresses imposed on the surfaces of a rectangular block; a Fourier-integral for stress imposed on the surfaces of an infinite layer; and a Green-function method for the stress field about buried inclusions. The methods are used to calculate the strain distributions in a transmission electron microscopy sample, the relaxation at the end facet of a strained-layer laser, and the strain field about a rectangular buried layer. The effects of the strain relaxation on the optical absorption of the laser facet and the zone-centre band structure of the buried layer are discussed. The equilibrium theory of critical thickness is examined in detail and is shown to make unreasonable predictions for highly strained layers; a modification which corrects this behaviour is suggested. The equilibrium theory equates the line tension of a strain relieving dislocation to the strain energy it relieves in the layer. The additional energy corrections which can be included in the line tension are discussed, together with the failure of the equilibrium theories to reliably predict plastic relaxation in all situations.

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41

Allsop, Thomas David Paul. "A fibre optical strain sensor". Thesis, University of Plymouth, 1999. http://hdl.handle.net/10026.1/2779.

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Abstract (sommario):

Strain-sensing elements, fabricated in standard communications-grade single mode optical fibre, are increasingly being considered for application in structural health monitoring. The reason for this is the numerous advantages demonstrated by these devices compared with traditional indicators. This thesis describes work carried out on optical sensors at the University of Plymouth. The aim of this work was to achieve an optical fibre strain sensing system capable of measuring absolute strain with good resolution and having wide dynamic range, without bulky optical equipment and not susceptible to misalignment due to handling. Earlier work was devoted to study on an intrinsic Fabry-Perot interferometric sensor and an optical phase-shift detection technique. The sensing element investigated relied on the end face of an optical fibre as one mirror and the second mirror being a layer of Titanium Dioxide (TO2). Although some results are included, it was soon realised that this sensor had a number of problems, particularly with fabrication. As no simple solution presented itself, consideration was given to a sensor that made use of the change in reflectance of an intra-core fibre Bragg grating when the grating was subjected to strain. The bulk of work described in this thesis is concerned with this type of sensing element. The grating structure is inherently flexible and a number of structural formats were studied and investigated. The first and simplest grating considered was two linearly chirped Bragg gratings used in a Fabry-Perot configuration (a grating resonator). The sensor was tested using the sensing detection system and although the fabrication problems were overcome absolute strain measurement was unattainable. To achieve this end, a theoretical study of a number of grating structures was carried out using the T-matrix Formalism. Confidence in using this approach was gained by comparing the spectral behaviour of a proposed grating with results, which were given by another theoretical model for the same proposed grating. The outcome of this study was that two structures in particular showed promise with regard to absolutism (the measure of true strain) and linearity. Discussions held with the department of Applied Physics at Aston University about fabrication resulted in one of the proposed designs being abandoned due to difficulties of fabrication. The second structure showed more promise and fabrication attempts were put in hand. This grating is linearly-chirped with a Top-hat function and a sinusoidal perturbation as a taper function of the refractive index modulation. Experiments were performed, data were acquired and system performance for this sensor is presented. The thesis concludes that using such a fibre Bragg grating as the sensing element of a strain sensing system enables it to measure absolute strain without using bulky optical equipment. At present, the resolution of strain is limited by the quality of the grating being fabricated (anomalies on profile), this should improve once the fabrication technique is refined.

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42

Wang, Duan Qiang. "Strain measurement using neutron diffraction". Thesis, Open University, 1996. http://oro.open.ac.uk/57651/.

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Abstract (sommario):

This thesis contains a study of improvement and application of strain measurement technique using neutron diffraction. A dedicated neutron strain scanner - ENGIN, funded by Ee. has been developed at ISIS. It has two radial collimators, allowing for the first time, measurements taken simultaneously at two orthogonal directions; uses Pawley refinement permitting both whole pattern and individual peak profile analysis and its positioner allow's specimens weighing 250 kg to be placed with an accuracy of 100 um. Strain measurement using neutron diffraction has been investigated under two extreme circumstances: very shallow (within 1 mm near surface) and very deep in materials (hundred of mm). Near-surface measurement requires both the accurate determination of the effective measurement position associated with precise location of specimen, calculation of centroid and correction for an anomalous near-surface effect. The strain measurements on a shot-peened surface in titanium alloy were carried out using the methodology mentioned above. The result is comparable to that obtained from X-ray diffraction. The latter was exploited by studying the effect of wavelength-dependent attenuation in materials. Experiments and theoretical analysis on aluminium and iron show that the effect is small for a strain scanner using radial collimator and time-of-flight technique. However, the reduction of the diffraction peak intensity, as a function of the amount of material in the beam path, reveals that great care should be taken when measuring texture as a function of depth in materials. The neutron diffraction technique was applied to several sets of engineering strain measurements. Firstly, 3-D residual stresses surrounding a cold expanded hole in a high strength aluminium alloy plate were measured. The result agrees well with that from modified Sachs' method after taking the effect of gauge volume averaging into account. Second, measurements of strain distributions in a Q-joint under zero and 30 kN load have been carried out, which provides a confirmation of the excellence of the joint design as the fastener system has completely shielded the fastener hole from deleterious tensile strains under operational loading. Finally, calibration strain measurement for an energy dispersive neutron transmission spectrometer was performed for the first time and it is found that the transmission spectrometer is feasible for strain and phase transformation measurement.

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43

Gough, Julia. "Stress-strain behaviour of rubber". Thesis, Queen Mary, University of London, 2000. http://qmro.qmul.ac.uk/xmlui/handle/123456789/28819.

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Abstract (sommario):

Several aspects of the stress-strain behaviour of rubber, important for evaluating its properties for finite element analysis and engineering applications, are investigated. Measurements of the deformation behaviour of an elastomer containing a compressible filler are used to assess theoretical equations for the compression modulus of rubber pads bonded to rigid endplates. The volume fraction of filler is estimated from a simple model. The first cycle stress-strain behaviour of filled and unfilled rubbers is characterised from uniaxial tests and by measuring both non-zero principal stresses with a novel pure shear technique. Various theoretical forms for the strain energy density function are assessed. The results support the assumption that the strain energy of filled natural rubber is a function only of the first strain invariant. Finite element modelling of the behaviour of a hyperelastic material in simple shear reveals that the proximity of the free edges in conventional simple shear testpieces strongly influences the stresses and deflections in the thickness direction. These finding are qualitatively supported by experiment. The effect of free edges on the shear modulus is also assessed. Deviations from hyperelastic behaviour are investigated through experimental studies of stress relaxation, cyclic stress softening and the superposition of a torsion on a uniaxial extension. Anisotropic deformations can result in corresponding differences in the amounts of stress relaxation or stress softening in different directions. Isotropic models cannot model these features but may be adequate for most practical applications. The relationship between the modulus and crystallinity of partially crystalline rubber is determined experimentally. The reinforcing effect of the crystals is found to be approximately independent of their morphology and of the modulus of the amorphous rubber. Studies of yielding of partially crystalline rubber show that the yield stress increases with increasing amounts of crystallization whereas the yield strain remains roughly constant.

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44

Wang, Yao. "MOSFET strain sensor for microcantilevers". Thesis, Queen's University Belfast, 2014. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.675436.

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Abstract (sommario):

Microcantilever structure was used to design and fabricate strain sensors. P-channel MOSFETs were designed and fabricated for strain sensors as hole mobility under uniaxial stress has higher mobility enhancement than that of electron mobility under either uniaxial stress or biaxial stress. For MOSFET sensors on microcantilevers, anchor area is the traditional position for sensors due to its highest stress. The aim of this research is to investigate the assumption of biaxial stress at the anchor area which makes the anchor location less sensitive. COMSOL software was employed to simulate stress profiles in silicon beams. Four-pointbending provides almost uniaxial stress at the surface, but cantilever bending generates biaxial stress at the anchor region but uniaxial stress away from anchor. The transverse stress at the anchor region increases with the bending and is depends on the longitudinal stress. In this research, the sensitivity of the sensor at the cantilever anchor was lower than that under uniaxial stress from four-point-bending measurement. It is suggested that the transverse stress at the anchor region will degrade the sensitivity compared to that under uniaxial stress. Although narrower cantilever provides higher longitudinal stress at the anchor, it brings higher transverse stress at the anchor as well. Possible solutions such as employing stressed layer, holes and slots were proposed to reduce the transverse stress without impact on the longitudinal stress, thus to increase the sensitivity. In comparison, employing slots is recommended as the transverse stress can be concentrated to nearly zero at the slot region with enhanced and elongated longitudinal stress.

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45

Gard, Gunvor. "Physical and psychosocial occupational strain". Doctoral thesis, Luleå tekniska universitet, Hälsa och rehabilitering, 1990. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-17034.

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Abstract (sommario):

This monography thesis is based on five empirical studies of physical and psychosocial occupational strain in working life. The first three studies concern the working environment of crane couplers. The first study, a questionnaire study, showed that monotonous postures and movements, heavy lifting and long walking distances were common reasons for regarding crane coupling as a physically strenuous work. The second study, a medical study, showed that clinical findings were more prevalent in the right neck- and shoulder region. The third study, an electromyographic study showed that the physical strain in crane coupling can be reduced by using wooden or other light weight spacers, to rearrange the layout so that slinging is always possible or by using slings mode of fibre or other light weight material. This study also indicated that crane coupling work may cause harmful effects to the shoulder- or neck region. The fourth study examined psychosocial strain and qualification in administrative computer work by using questionnaires, interviews and physiological measurements at repeated occasions. The results indicated a good agreement between level of qualification, psychosocial work load and job satisfaction. Computerisation lead to increased qualifications at work. This improved job satisfaction but at the same time resulted in an increased workload. The fifth study concerns how patients visiting primary health care perceive physical and psychosocial occupational strain. It could be shown that the patients perceived physical as well as psychosocial strain as important working environment problems
Godkänd; 1990; 20060928 (andbra)

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46

Aoki, Yohko. "Strain transducers for active control". Thesis, University of Southampton, 2008. https://eprints.soton.ac.uk/66297/.

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Abstract (sommario):

This thesis presents the results of a theoretical and experimental study of active vibration control using velocity feedback with piezoceramic actuator(s) and closely located velocity sensor(s). The first part of the thesis presents modeling and design studies for a square piezoceramic actuator used to implement a single channel velocity feedback control with a velocity sensor at its center. A fully coupled mobility model of the panel with a square piezoceramic patch actuator is introduced and experimentally validated in order to predict the sensor-actuator open loop response over much wider frequency range than is commonly used, so that the stability of the feedback control loop can be properly assessed using the Nyquist criterion. These simulations suggest that increasing the width and reducing the thickness of the square actuator improves the control performance of a single channel velocity feedback control loop in the case considered. The second part of this thesis investigates a new configuration of the velocity feedback control system, which is composed of a piezoceramic actuator shaped as isosceles triangle with a velocity sensor at its tip. A fully coupled mobility model has been developed, which predicts the response of the sensor-actuator pair more accurately than the conventional modeling method. The implementation of a 16 channel decentralized control system using triangular actuator has been experimentally demonstrated. Significant levels of attenuation, up to 20 dB, are achieved at the first few resonant peaks in term of both structural vibration and sound radiation. Closed loop measurements have highlighted that the control performance are significantly improved by increasing the base length and/or the height of the triangle actuators, with the limitation that the increase of the height reduces the usable frequency range of the control system.

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47

Andrews, Jeffrey Pratt. "Longitudinal misalignment based strain sensor". Thesis, Virginia Tech, 1989. http://hdl.handle.net/10919/43283.

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Abstract (sommario):

A practical fiber optic strain sensor has been developed to measure strains in the range of 0.0 to 2.0 percent strain with a resolution ranging between 10 and 100 microstrain depending on sensor design choices. This intensity based sensor measures strain by monitoring strain induced longitudinal misalignment in a novel fiber interconnection. This interconnection is created by aligning fibers within a segment of hollow core fiber. Related splice loss mechanisms are investigated for their effect on resolution. The effect of gauge length and launch conditions are also investigated.

Master of Science

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48

Guo, Jun. "Mechanical Amplified Capacitive Strain Sensor". Case Western Reserve University School of Graduate Studies / OhioLINK, 2007. http://rave.ohiolink.edu/etdc/view?acc_num=case1175876717.

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49

Raynolds, James E. "Strain-induced birefringence in GaAs /". The Ohio State University, 1994. http://rave.ohiolink.edu/etdc/view?acc_num=osu1487859879941051.

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50

Fallon, Richard W. "Fibre Bragg grating strain sensors". Thesis, Aston University, 2000. http://publications.aston.ac.uk/15304/.

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Abstract (sommario):

The fabrication of in-fibre Bragg gratings (FBGs) and their application as sensors is reported. The strain and temperature characteristic results for a number of chirped and uniform gratings written into three different host fibres are presented. The static and dynamic temperature response of a commercially available temperature compensated grating is reported. A five sensor wavelength division multiplexed fibre Bragg grating strain measurement system with an interrogation rate of 25 Hz and resolution of 10 was constructed. The results from this system are presented. A novel chirped FBG interrogation method was implemented in both the 1.3 and 1.5 m telecommunication windows. Several single and dual strain sensor systems, employing this method, were constructed and the results obtained from each are reported and discussed. These systems are particularly suitable for the measurement of large strain. The results from a system measuring up to 12 m and with a potential measurement range of 30 m are reported. This technique is also shown to give an obtainable resolution of 20 over a measurement range of 5 000 for a dual sensor system. These systems are simple, robust, passive and easy to implement. They offer low cost, high speed and, in the case of multiple sensors, truly simultaneous interrogation. These advantages make this technique ideal for strain sensing in SMART structures. Systems based on this method have been installed in the masts of four superyachts. A system, based on this technique, is currently being developed for the measurement of acoustic waves in carbon composite panels. The results from an alternative method for interrogating uniform FBG sensors are also discussed. Interrogation of the gratings was facilitated by a specifically written asymmetric grating which had a 15 nm long linearly sloped spectral edge. This technique was employed to interrogate a single sensor over a measurement range of 6 m and two sensors over a range of 4.5 me. The results obtained indicated achievable resolutions of 47 and 38 respectively.

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Tesi sul tema "Strain"

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