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Статті в журналах з теми "Bending Strain measurements"
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Leski, Andrzej, Wojciech Wronicz, Piotr Kowalczyk, Michał Szmidt, Robert Klewicki, Karol Włodarczyk, and Grzegorz Uliński. "Modular Test Stand for Fatigue Testing of Aeronautical Structures – Verification of Assumptions." Fatigue of Aircraft Structures 2020, no. 12 (December 1, 2020): 78–91. http://dx.doi.org/10.2478/fas-2020-0008.
Повний текст джерелаАнотація:
Abstract The Modular Test Stand was developed and manufactured to decrease the cost of fatigue testing and reduce the time of its completion as well as to enable testing specimens under more complex load conditions. The stand consists of three connected sections, similar to a wing box, all being loaded in the same way. Thanks to that, several specimens can be tested simultaneously. This configuration requires that stress and strain distribution should be reasonably uniform, as assumed in the design stage. The structure can be loaded with bending or torsion. A whole section, selected structural node or a specimen mounted in the structure as well as a repair or a sensor can be a test object. Two stands, one for bending and one for torsion were prepared. This paper presents the verification of the assumed strain and stress distributions on the skin panels. The measurements were performed with the use of Digital Image Correlation (DIC) as well as strain gauges. DIC measurements were performed on one skin panel of the central section. Five strain gauge rosettes were installed on both panels of the one section. In addition, one rosette was applied to one skin panel in each of two other sections. Measurements were performed on the stand for torsion as well as on the stand for bending. The results of DIC analysis and strain gauge measurement during torsion show uniform shearing strain distributions on the panels. During bending, on the tensioned side, the strains obtained indicate quite uniform strain distributions. On the compressed side, local buckling of the skin panels results in high strain gradients. Strain levels obtained with the use of a DIC analysis and strain gauge measurements were similar. Moreover, horizontal displacements of markers in the spar axis during bending was determined based on a series of photographic. The deflection line obtained in this way has a shape similar to arc, which is characteristic of the constant bending moment. The stand was tested with torsional and bending loads in order to verify the design assumptions. The results of strain distributions on the skin panels with the use of DIC and strain gauges as well as the deflection line of the spar axis indicate that the Modular Test Stand performs as assumed and can be used for tests.
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Ridge, I. M. L., J. Zheng, and C. R. Chaplin. "Measurement of cyclic bending strains in steel wire rope." Journal of Strain Analysis for Engineering Design 35, no. 6 (August 1, 2000): 545–58. http://dx.doi.org/10.1243/0309324001514288.
Повний текст джерелаАнотація:
This paper reports strain gauge measurements of cyclic bending strain in the wires of a six-strand right-handed Lang's lay steel wire rope running on and off a pulley. The paper describes the measurement procedures and presents the results for the two tests conducted which had different gauge configurations along and around the sample. It was found that the strain waveforms observed had some similarities with those reported elsewhere and the magnitudes of strains matched theoretical predictions. However, in contrast with behaviour reported for fluctuating tension, the initial differences between and along wires rapidly attenuated. This observation helps to explain reported similarities in bending fatigue performance of ropes from different sources which contrasts with the very significant differences in characteristics found in tensile fatigue. The dependence of wire strain amplitude on rope bending deformation further contrasts with tensile fatigue in which wire strain range is dependent on the local sharing of axial load.
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Liu, Shucong, Dezhi Zheng, Tianhao Wang, Mengxi Dai, Rui Li, and Qingshan Feng. "A novel algorithm for pipeline displacement and bending strain of in-line inspection based on inertia measurement technology." Advances in Mechanical Engineering 10, no. 12 (December 2018): 168781401881675. http://dx.doi.org/10.1177/1687814018816755.
Повний текст джерелаАнотація:
The in-line inspection tool with Inertial Measurement Unit tool is becoming a routine and important practice for many pipeline companies and is effective for whole-line bending strain measurement. However, the measurements of Inertial Measurement Unit tool are always affected by noises and errors, which are caused by inherent inaccuracies and deficiencies of the experimental techniques and measuring devices. For the calculations of the bending strain, the results are very sensitive to the noises and errors. A filtering algorithm based on cubic spline interpolation was proposed for Inertial Measurement Unit data processing to eliminate noises and errors for bending strain, and the effectiveness is validated through the pipeline field test. The results showed that the average pipeline displacement deviation declined 13.82% in the three tests, and the bending strain error reduced from 0.037% to 0.014%. The proposed method effectively improves the inspection accuracy and provides an effective method for pipeline displacement and strain inspection, which ensures the safe operation of the pipeline.
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Socha, Bernard J., Edward T. Bednarz, and Wei-Dong Zhu. "A combined loading transducer for calculating the bending moment and torque in a slender circular beam using the minimum numbers of strain gauges, strain grids, and measurement channels." International Journal of Distributed Sensor Networks 16, no. 6 (June 2020): 155014772092177. http://dx.doi.org/10.1177/1550147720921774.
Повний текст джерелаАнотація:
The purpose of this work is to develop a new methodology that uses the minimum numbers of strain gauges, strain grids, and measurement channels to calculate the bending moment and torque in a slender circular beam under combined loading from measured strains in it. In general, each independent variable requires a minimum of one independent measurement. Two grids of a single-rosette strain gauge located at 45° and −45° from the longitudinal axis of the beam are used in conjunction with two measurement channels to gather all measurements and form a combined loading transducer. A theoretical set of equations of the new methodology is developed to minimize numbers of strain grids and measurement channels, and an experimental configuration was tested in a variety of scenarios. Calibration factors were independently developed for the bending moment and torque of the beam by separately loading it in their respective directions. These calibration factors were applied to different combined loading scenarios, where errors were found to be on average 1.6% for moment comparison and 6.7% for torque comparison.
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Devivier, C., Daniel Thompson, Fabrice Pierron, and M. R. Wisnom. "Correlation between Full-Field Measurements and Numerical Simulation Results for Multiple Delamination Composite Specimens in Bending." Applied Mechanics and Materials 24-25 (June 2010): 109–14. http://dx.doi.org/10.4028/www.scientific.net/amm.24-25.109.
Повний текст джерелаАнотація:
This paper studies the effect of delaminations on strain maps for a simple cantilever beam. The aim is to build an experimental set-up which allows detecting very slight modifications in the strain maps. The case studied is a single delamination on the mid-plane. The measurement method is the deflectometry technique which enables direct slope measurements on a reflective specimen. The comparison with finite element models clearly indicated that the surface strains bear the information of the extent of the delamination. The second step is to use these surface strains to identify a stiffness reduction map for real impact damages.
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Yu, Feng, and Michael T. Hendry. "A new strain gauge configuration on the rail web to decouple the wheel–rail lateral contact force from wayside measurement." Proceedings of the Institution of Mechanical Engineers, Part F: Journal of Rail and Rapid Transit 233, no. 9 (January 13, 2019): 951–60. http://dx.doi.org/10.1177/0954409718822870.
Повний текст джерелаАнотація:
The simultaneous presence of bending moments and torques produced by the lateral and vertical contact forces between the wheel and the rail generates a complex strain state on the rail surface, which makes it difficult to identify the strain signals produced purely from the lateral contact force. In this study, a new strain gauge configuration is proposed to decouple strain signals of the wheel–rail lateral contact force from wayside measurements by analyzing the bending strains on the rail web using a full Wheatstone bridge. For this purpose, a finite element modeling of the wheel–rail contact is performed to analyze the bending strains on the rail web and to optimize two instrumented sections for eight electric resistance strain gauges. Laboratory testing is also used to examine the installation scheme of the strain gauges at the two optimal instrumented sections. A good agreement is observed between the experimental data and the simulation results. Strain signals are evenly distributed for about 10 cm in the middle region between the two optimal instrumented sections and only account for the lateral contact force.
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Arola, Anna Maija, Antti J. Kaijalainen, and Vili Kesti. "Evaluation of Bendability of Hot-Rolled S960 Grade Steel Using Optical Strain Measurements and FE-Modelling." Key Engineering Materials 651-653 (July 2015): 610–16. http://dx.doi.org/10.4028/www.scientific.net/kem.651-653.610.
Повний текст джерелаАнотація:
Bending is an important forming process for ultra-high strength steel (UHSS) because it is cost-effective, fast and in many cases it can be used to replace welding in a part manufacturing processes. One major challenge in air bending of UHSS is to predict the limits for bendability since the traditional methods for failure prediction, such as forming limit diagram (FLD), cannot generally be applied to bending process. In this paper, 3D FE-modelling coupled with a CDM-damage model is used to simulate the air bending process and to determine the bendability limits for a hot-rolled 960MPa grade. Damage parameters for the CDM-model are determined by using optical strain measurements and inverse modelling of the tensile test. Three point bending tests with optical strain measuring were carried out to determine the deformation field of the outer bend in different bending angles and the results of the bending simulation are compared with the strain measurements of the bending tests. The damage model is then calibrated using the experimental results of the bending tests to adjust the crack occurrence in the simulation. A good agreement was found between simulations and experimental measurements.
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Weisbrich, Martin, and Klaus Holschemacher. "Comparison between different fiber coatings and adhesives on steel surfaces for distributed optical strain measurements based on Rayleigh backscattering." Journal of Sensors and Sensor Systems 7, no. 2 (November 21, 2018): 601–8. http://dx.doi.org/10.5194/jsss-7-601-2018.
Повний текст джерелаАнотація:
Abstract. Optical fiber measurement systems have recently gained popularity following a multitude of intensive investigations. A new technique has been developed for these measurement systems that uses Rayleigh backscatter to determine the distributed strain measurement over the total length of a fiber. These measurement systems have great potential in civil engineering and structural health monitoring. This paper addresses some preliminary comparisons between three different fiber coatings and six different adhesives on steel structures. The results are based on a bending test with specimens made of precision flat steel; optical fiber strain measurements were compared with photogrammetric strain measurements. Analysis of the test data showed a strong correlation between the optical measurement system's results and the theoretical results up to the yielding point of the steel. Furthermore, the results indicate that fibers with the Ormocer® and polyimide coatings have almost the same strain values as the reference measurement method. The main results of this investigation are a guideline describing how to attach optical fibers to steel surfaces for distributed fiber optical strain measurements and recommendations for coatings to obtain realistic strain values. Additionally, the advantages of distributed strain measurements were revealed, which illustrates the potential of Rayleigh backscattering applications.
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Song, Xu, Solène Chardonnet, Giancarlo Savini, Shu Yan Zhang, Willem J. J. Vorster, and Alexander M. Korsunsky. "Experimental/Modelling Study of Residual Stress in Al/SiCp Bent Bars by Synchrotron XRD and Slitting Eigenstrain Methods." Materials Science Forum 571-572 (March 2008): 277–82. http://dx.doi.org/10.4028/www.scientific.net/msf.571-572.277.
Повний текст джерелаАнотація:
The aim of the study presented here was to evaluate the residual stresses present in a bar of aluminium alloy 2124-T1 matrix composite (MMC) reinforced with 25vol% particulate silicon carbide (SiCp) using X-ray diffraction and 3D profilometry (curvature measurement using Mitutoyo/Renishaw coordinate measurement machine) and comparing these results with numerical models of residual strain and stress profiles obtained by a simple inelastic bending model and Finite Element Analysis (FEA). The residual strain distribution was introduced into the test piece by plastic deformation in the 4-point bending configuration. At the first stage of this study the elasticplastic behaviour of the MMC was characterized under static and cyclic loading to obtain the material parameters, hardening proprieties and cyclic hysteresis loops. Subsequently, synchrotron Xray diffraction and CMM curvature measurements were performed to deduce the residual stress profile in the central section of the bar. The experimental data obtained from these measurements were used in the inelastic bending and FEA simulations. The specimens were then subjected to incremental slitting using EDM (electric discharge machining) with continuous back and front face strain gauge monitoring. The X-ray diffraction and incremental slitting results were then analysed using direct and inverse eigenstrain methods. Residual stresses plots obtained by different methods show good agreement with each other.
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Xu, Y., and R. N. Miles. "Experimental determination of bending strain power spectra from vibration measurements." Experimental Mechanics 36, no. 2 (June 1996): 166–72. http://dx.doi.org/10.1007/bf02328714.
Повний текст джерелаДисертації з теми "Bending Strain measurements"
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BEZZICCHERI, MATTEO. "Problems in measurement of mechanical loads in wind turbines: bending/torsional moments by strain gage bridges and torque by optical transducer." Doctoral thesis, Università Politecnica delle Marche, 2018. http://hdl.handle.net/11566/252847.
Повний текст джерелаАнотація:
Il lavoro tratta la complessità di misurare carichi meccanici su grandi turbine eoliche; parametri cruciali per la certificazione e il monitoraggio delle condizioni di funzionamento.
I carichi meccanici di maggior rilievo su una turbina eolica sono i momenti flettenti e torcenti che, in accordo con la normativa IEC 61400‐13, è consigliabile misurare attraverso ponti estensimetrici interi.
Questa tesi discute le linee guida per la progettazione della catena di misura estensimetrica e confronta le diverse possibili procedure di calibrazione: analitica, carichi esterni e squilibri propri. Il lavoro propone modelli di calibrazione che sfruttano squilibri di massa propri, commenta gli intervalli di calibrazione raggiungibili e presenta un’analisi di incertezza del processo di calibrazione.
La calibrazione dovrebbe avvenire in condizione isotermiche ma nella pratica questo requisito potrebbe non essere sempre verificato. Pertanto, la tesi esamina l’influenza del fenomeno termico sulla misura estensimetrica e le soluzioni tecniche adottabili per limitare il fenomeno.
Tra le misure estensimetriche, quella della coppia sull’albero è la più incerta. Tuttavia, studi dimostrano che il segnale di coppia fornisce informazioni sullo stato di salute della macchina quindi è necessario usare soluzioni più precise, come i torsiometri in linea, che risultano però essere invasive e inadeguate. L’alternativa viene proposta nella seconda parte della tesi, ovvero una tecnica di misura della coppia innovativa e senza contatto costituita da due nastri zebrati montati sull’albero e da due sonde ottiche su un supporto rigido non rotante.
Le prestazioni del sistema sono state analizzate in un banco prova. I risultati mostrano una buona corrispondenza con le misure di riferimento eseguite attraverso un torsiometro in linea con una incertezza del ± 0,3%. Infine, la tesi presenta un’analisi di fattibilità per due soluzioni reali di turbine eoliche e mostra come la tecnica di misura è meno incerta quando applicata su alberi lunghi e lenti.This thesis discusses the complexity of measuring mechanical loads on large wind turbines; parameters that play a crucial role in the certification and monitoring of wind turbines. The most important mechanical loads on a wind turbine are bending and torsional moments that are usually measured through full strain gage bridges, as recommended by the standard IEC 61400-13. This thesis discusses the guidelines to design the strain gage measurement chain and a comparison among the different calibration procedures: analytical, external loads and gravity. This work proposes static-dynamic models for a gravity calibration, comments on the attainable range of calibration and presents an uncertainty analysis of the calibration process. Even if measurement should take place in isothermal condition, this is not always the case in real world practice. Therefore, the thesis puts into evidence its influence on calibration and signal uncertainty and the technical solutions that can be adopted to limit the phenomenon. Among the strain gage measurements, the torque measurement on the shaft is the most uncertain. However, many studies have shown that an accurate torque measurement can provide much information about the WT’s health. Available solutions more accurate, like inline torque sensor, are invasive and inappropriate. This thesis, in its second part, analyses a novel, contactless torque measurement system consisting of two shaft-mounted zebra tapes and two optical sensors mounted on stationary rigid supports. The performance of the system has been analysed experimentally on a test bench. The results show good agreement with reference measurements from an in-line, invasive torque transducer with an uncertainty of ±0.3%. Finally, a feasibility analysis and a system scale-up design for two typical WTs with different shaft configurations has been performed and shows that the measurement technique is less uncertain when performed on long and slow shafts.
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TANAKA, Keisuke, Yoshiaki AKINIWA, Yoshihisa SAKAIDA, and Hirohisa KIMACHI. "Lattice Strain and Domain Switching Induced in Tetragonal PZT by Poling and Mechanical Loading." The Japan Society of Mechanical Engineers, 2000. http://hdl.handle.net/2237/9183.
Повний текст джерела
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Oscarsson, Jan. "Strength grading of structural timber and EWP laminations of Norway spruce : Development potentials." Licentiate thesis, SP Sveriges Tekniska Forskningsinstitut, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:lnu:diva-23757.
Повний текст джерелаАнотація:
Strength grading of structural timber is a process by which value is added to sawn products. It is to the greater part carried out using machine grading based on statistical relationships between so called indicating properties and bending strength. The most frequently applied indicating property (IP) on the European market is the stiffness in terms of average modulus of elasticity (MOE) of a timber piece, although MOE is a material property that varies within timber. A major limitation of today’s grading methods is that the described relationships are relatively poor, which means that there is a potential for more accurate techniques. The main purpose of this research has been to initiate development of more accurate and efficient machine grading methods. Strength of timber is dependent on the occurrence of knots. At the same time, knot measures applied as indicating properties until today have shown to be poor predictors of strength. However, results from this research, and from previous research, has shown that not only size and position of knots but also fibre deviations in surrounding clear wood are of great importance for local stiffness and development of fracture under loading. Thus, development of new indicating properties which take account of knots as well as properties of surrounding fibres, determined on a very local scale, was considered as a possible path towards better strength grading. In the research, results from contact-free deformation measurements were utilized for analysis of structural behaviour of timber on both local and global level. Laser scanning was used for detection of local fibre directions projected on surfaces of pieces. Scanned information, combined with measures of density and average axial dynamic MOE, was applied for calculation of the variation of local MOE in the longitudinal board direction. By integration over cross-sections along a piece, a stiffness profile in edgewise bending was determined and a new IP was defined as the lowest bending MOE along the piece. For a sample of Norway spruce planks, a coefficient of determination of 0.68 was achieved between the new IP and bending strength. For narrow side boards to be used as laminations in wet-glued glulam beams, the relationship between IP and tensile strength was as high as 0.77. Since the intended use of the narrow boards was as laminations in wet-glued beams, the possibility of grading them in a wet state was also investigated. Grading based on axial dynamic excitation and weighing gave just as good results in a wet state as when the same grading procedure was applied after drying. It was also found that the relationship between the new IP and strength was dependent on what scale the IP was determined. Optimum was reached for moving average MOE calculated over lengths corresponding with approximately half the width of investigated pieces. Implementation of the new IP will result in grading that is more accurate than what is achieved by the great majority of today’s grading machines. The new method will probably also be particularly favourable for development of engineered wood products made of narrow laminations.Hållfasthetssortering av konstruktionsvirke innebär att värdet på sågade produkter ökar. Sorteringen genomförs oftast med maskinella metoder baserade på statistiska samband mellan s.k. indikerande egenskaper och böjhållfasthet. Den indikerande egenskap (indicating property, IP) som är vanligast på den Europeiska marknaden är styvhet uttryckt som ett medelvärde för elasticitetsmodulen (modulus of elasticity, MOE) i ett virkesstycke, trots att MOE är en materialegenskap som varierar i virket. En betydande begränsning med dagens sorteringsmetoder är att de beskrivna sambanden är förhållandevis svaga, vilket innebär att det finns en potential för metoder med högre noggrannhet. Det huvudsakliga syftet med detta doktorandprojekt har varit att initiera en utveckling mot sådana metoder. Hållfasthet hos virke är beroende av förekomst av kvistar. Samtidigt har de kvistmått som fram till idag kommit till användning visat sig vara dåliga prediktorer av hållfasthet. Resultat från såväl denna som tidigare forskning har dock visat att inte bara kvistars storlek och läge, utan också variationen i fiberriktning i omgivande träfibrer, är av stor betydelse för lokal styvhet och brottförlopp under inverkan av last. Utveckling av nya IP som tar hänsyn till såväl kvistar som omgivande träfibrers egenskaper fastställda på mycket lokal nivå bedömdes vara en möjlig väg för att uppnå bättre hållfasthetssortering. I detta doktorandprojekt användes beröringsfri deformationsmätning för analys av det strukturella beteendet hos virkesstycken på såväl lokal som global nivå. Laserskanning utnyttjades för detektering av lokala fiberriktningar projicerade på virkesstyckenas ytor. Med utgångspunkt från skannad information, virkesdensitet och medelvärde för axiell dynamisk elasticitetsmodul kunde variationen i lokal elasticitetsmodul i virkesstyckenas längdriktning bestämmas. Genom integration över tvärsektioner längs ett virkesstycke kunde en profil över hur böjstyvheten i styva riktningen varierade i virkesstyckets längdriktning beräknas. En ny IP definierades som den lägsta elasticitetsmodulen i böjning utmed virkesstyckets längd. För ett urval av granplankor erhölls en förklaringsgrad på 0.68 mellan den nya indikerande egenskapen och böjhållfasthet. För smala sidobrädor avsedda att användas som lameller i våtlimmade limträbalkar var motsvarande förklaringsgrad mellan samma IP och draghållfasthet så hög som 0.77. Eftersom sidobrädorna var avsedda att användas som lameller i våtlimmade balkar genomfördes en studie avseende möjligheten att hållfasthetssortera i vått tillstånd med hjälp av axiell dynamisk excitering och vägning. Det visade sig att sådan sortering gav lika bra resultat som då samma metod användes efter torkning. Sambandet mellan den nya indikerande egenskapen och hållfasthet visade sig också vara beroende av på vilken lokal nivå som egenskapen beräknades. Optimum uppnåddes då den bestämdes som ett glidande medelvärde beräknat över en längd motsvarande ungefär halva virkesstyckets höjd. Implementering av den nya sorteringsmetoden kommer att resultera i sortering som är noggrannare än vad som kan erhållas med det stora flertalet av de sorteringsmetoder som finns idag. Den nya indikerande egenskapen kommer sannolikt att bli särskilt gynnsam att använda för utveckling av ingenjörsmässiga träprodukter bestående av smala lameller.
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Yarajena, Sai Saraswathi. "2D Piezotronics: Performance to Functionality." Thesis, 2023. https://etd.iisc.ac.in/handle/2005/6199.
Повний текст джерелаАнотація:
In the pursuit of interactive electronic devices, there is a need for smart materials which can serve multiple functionalities. 2D (two-dimensional) layered materials have gained attention in semiconductor technology because of their versatile electrical and optical properties. Furthermore, some materials exhibit piezoelectricity at 2D scale and can withstand enormous strain. These properties make them suitable as smart materials involving electromechanical signals. In the literature, materials which are semiconducting and piezoelectric are termed piezotronic (piezo+electronic) materials. Theoretical studies have indicated many materials as piezoelectric in 2D form. However, experimental tools to investigate the extent of piezoelectric coupling in 2D materials are limited, and their relevance for piezotronics has not been studied in detail. This dissertation presents some key aspects of 2D Piezotronics for improved performance and to achieve additional functionalities with heterojunctions. The work constitutes proposing a technique to estimate piezoelectric coupling coefficients, choice of flexible substrates for piezotronics, methods to reduce the charge screening effects, measurement strategies to extract the actual piezoelectric output from the bending measurements, and the study of heterojunctions for rectifying behaviour. In this work, Molybdenum disulfide (MoS2) is used as active piezoelectric material.
In the initial part of the work, I propose a technique to estimate in-plane piezoelectric coupling quantitatively for 2D materials. The method involves a novel approach for in-plane field excitation in lateral Piezo force microscopy (PFM). Contact resonance gain of the tip-sample system is leveraged to measure the piezoelectric coupling coefficients in a few pm/V to sub pm/V range. However, I have shown that operating PFM at contact resonance can cause pseudo piezoelectric signals. Therefore, a detailed methodology for signal calibration and electrostatic background subtraction is developed in this work. The technique is verified by estimating the in-plane piezoelectric coupling coefficients (d11) for freely suspended MoS2 of one to five atomic layers. The technique presented is useful in estimating the piezoelectric coupling strengths in emerging 2D materials.
Piezotronic devices are made on flexible substrates for practical applications. Fabrication on flexible substrates often poses great difficulties in handling them, depositing inorganic materials, and carrying out lithography processes. I propose the commercially available nano flex film as a prospective substrate for piezotronics. Carrying out fabrication on these substrates is as seamless as that on rigid substrates. Substrates such as PET, Nano flex and TPU can be used for low-temperature (<150 deg C) applications. Kapton is one of the flexible substrates that can handle higher temperatures(>200 deg C). However, they tend to twist when heated, making the fabrication difficult. I have proposed a gel-based bonding for the Kapton substrates wherein the debonding process is automatic. The method is helpful for the fabrication of 2D material devices on Kapton. Besides selecting the substrates, suitable base layers and passivation techniques are studied to reduce the charge screening effects and thus improve the performance of piezotronic devices. It is verified that open circuit voltages and strain gauge factors obtained for the current monolayer MoS2 device on SiO2 are three folds higher than those presented in the literature.
A simple measurement setup which does not require probe needles or wire bonding is developed for the bending strain measurements. The open circuit voltage and short circuit current signals obtained from a single 2D material device are very small. The noise signals that originate from various triboelectric and electrostatic sources of the measurement setup can be of similar magnitude. Consequently, the electrical outputs from these devices during bending measurements are often misinterpreted. Thus, it is essential to analyse various noise sources in bending measurements. I then discuss ways to reduce the background noise and identify the valid piezoelectric output.
Finally, I have studied some homogeneous and heterogeneous junctions of MoS2 to achieve good rectifying junction behaviour, which can add extra functionalities for piezotronics. The rectification ratio values as high as 5000 could be achieved at 1 V bias. Besides the rectifying ratio, I have observed that the heterojunctions of MoS2 and MoTe2 have superior piezoelectric behaviour compared to other 2D material junctions reported so far with open circuit voltages as high as ~1 V and peak power density of ~200 mW/m2 at 0.44% bending strain. Formation of the p-n and Schottky junction hybrid in MoS2-MoTe2 heterojunction could achieve high rectification ratios and open circuit voltages and is fascinating for further study.
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Feng, Chih-Min, and 馮智敏. "Digital Image Analysis for Strain Measurement of Flexible Substrate under Bending Test." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/35522950857470760578.
Повний текст джерелаАнотація:
碩士國立交通大學
機械工程系所
97
Flexible electronic is important development in modern technology. One of the most widespread applications is “flexible display”, which is mainly developed for the next generation monitor. Flexible display is thin and flexible, shock-resistant, and can serve in daily life as electronic paper and electronic books. Flexibility is one of major characteristics for flexible display. Therefore, how to measure the strain field of bending for flexible polymer substrate that constitute the flexible display is an important technique. In view of the fact that traditional devices such as strain gages and photoelasticity are not suitable for measure large deformation, this study develops noncontact measurement as the first choice. As a result of today's noncontact measurement technology is set up by complex structure of the optical path, and the environment of measurement is demanding. This study develops an imaging method less susceptible of light effect on the environment, rather than sets up complex devices of noncontact measurement. Using two CCD cameras constructs a three-dimensional computer vision system, which captures images of the sample before and after deformation in the bending test. Based on the digital image correlation, this study compares the displacement vector of any point on the display surface when deformation occurs. The deformation gradient of materials is calculated by the displacement vector, and we can obtain the strains of the bending test for flexible electronic. According to the bending test result of PEN substrate, the strain at the center of sample surface indeed increases with curvature increase.
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Wildy, Stuart James. "Scanning laser doppler vibrometry for strain measurement and damage detection." Thesis, 2012. http://hdl.handle.net/2440/93519.
Повний текст джерелаАнотація:
Numerous strain measurement and damage detection techniques have been developed over the last century. These techniques include strain gauges, digital image correlation, radiography and ultrasonic inspections. All have various advantages, as well as disadvantages, which make each suited to specific applications. With the development of laser Doppler vibrometry, a number of techniques have been established for non-destructive evaluation, such as the measurement of bending strain, as well as damage detection using kinematic parameters, including displacement and curvature. With recent advancements in laser Doppler vibrometry technology (such as 3D scanning laser Doppler vibrometry for three-dimensional displacement measurements, improved velocity decoders and increased spatial resolution) the door has been opened to develop techniques for measuring surface strain from in-plane displacements, as well as the development of new damage detection techniques based on the fundamental principle of deformation:- the governing differential equation of displacement. The extensive literature review contained in this thesis identified a number of gaps in the field, including the evaluation of the accuracy of quasi-static bending strain measurements using current 1D SLDV technology, the precision of full-field surface strain measurement techniques utilising 3D SLDV, and new detection techniques based on the violation of the governing differential equations of displacement. Thus, the research contained in this thesis focussed on these areas. The first part of this thesis presents an investigation into the use of 1D and 3D scanning laser Doppler vibrometry for non-contact measurement of quasi-static bending strain in beams and surface strain in plates, respectively. The second part presents a new damage detection technique based on the governing differential equations of displacement in beam and plate structures. Two algorithms are developed to determine a violation in the governing differential equations created by either a delamination in a composite beam with out-of-plane displacements, or by a crack in a plate with in-plane displacements.Thesis (Ph.D.) -- University of Adelaide, School of Mechanical Engineering, 2012
Книги з теми "Bending Strain measurements"
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F, Harrington, and United States. National Aeronautics and Space Administration., eds. Static test induced loads verification beyond elastic limit. [Washington, D.C: National Aeronautics and Space Administration, 1996.
Знайти повний текст джерелаЧастини книг з теми "Bending Strain measurements"
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Grediac, M., and A. Vautrin. "Measurement of Laminate Bending Elastic Parameters from Non-Uniform Strain Fields." In Mechanical Identification of Composites, 91–98. Dordrecht: Springer Netherlands, 1991. http://dx.doi.org/10.1007/978-94-011-3658-7_9.
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Hack, Erwin, and Ann Schumacher. "Espi-Measurement of Strain Components on a Cfrp-Reinforced Bending Beam." In Experimental Analysis of Nano and Engineering Materials and Structures, 723–24. Dordrecht: Springer Netherlands, 2007. http://dx.doi.org/10.1007/978-1-4020-6239-1_359.
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Bremand, F., and A. Lagarde. "Optical Method of Strain Measurement. Application to Study of Circular Bending of a Beam in the Large Strain Range." In Experimental Stress Analysis, 341–50. Dordrecht: Springer Netherlands, 1986. http://dx.doi.org/10.1007/978-94-009-4416-9_38.
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"Fatigue of Metals." In Fatigue and Fracture, 147–207. ASM International, 2012. http://dx.doi.org/10.31399/asm.tb.ffub.t53610147.
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Abstract This chapter discusses the factors that play a role in fatigue failures and how they affect the service life of metals and structures. It describes the stresses associated with high-cycle and low-cycle fatigue and how they differ from the loading profiles typically used to generate fatigue data. It compares the Gerber, Goodman, and Soderberg methods for predicting the effect of mean stress from bending data, describes the statistical nature of fatigue measurements, and explains how plastic strain causes cyclic hardening and softening. It discusses the work of Wohler, Basquin, and others and how it led to the development of a strain-based approach to fatigue and the use of fatigue strength and ductility coefficients. It reviews the three stages of fatigue, beginning with crack initiation followed by crack growth and final fracture. It explains how fracture mechanics can be applied to crack propagation and how stress concentrations affect fatigue life. It also discusses fatigue life improvement methods and design approaches.
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Kohzuki, Yohichi. "Study on Influence of a State of Dopants on Dislocation-Dopant Ions Interaction in Annealed Crystals." In Alkaline Chemistry and Applications [Working Title]. IntechOpen, 2021. http://dx.doi.org/10.5772/intechopen.96395.
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Combination method of strain-rate cycling tests and application of ultrasonic oscillations was conducted for KCl:Sr2+ (0.035, 0.050, 0.065 mol.% in the melt) single crystals at low temperatures. The measurement of strain-rate sensitivity (λ) of flow stress under the application of ultrasonic oscillatory stress provides useful information on the interaction between a mobile dislocation and impurities (Sr2+ ions) during plastic deformation and the variation of λ with stress decrement (Δτ) due to oscillation has stair-like shape: The first plateau place ranges below the first bending point (τp1) at low stress decrement and the second one extends from the second bending point (τp2) at high stress decrement. The value of λ decreases with the Δτ between the two bending points. The τp1 is considered to represent the effective stress due to impurities when a dislocation begins to break-away from the impurities with the help of thermal activation during plastic deformation. Annealing the impure crystal by heat treatment, τp1 decreases obviously at low temperature and the critical temperature Tc, at which τp1 is zero, also becomes slightly smaller. Furthermore, it was investigated whether a change in the state of a small amount of impurities has an influential factor of the flow parameters (e.g., the activation energy, the density of forest dislocations) from the data analyzed in terms of Δτ vs. λ curve.
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Zhao, Hongduo, Songyuan Gu, Jianming Ling, and Yizhou Peng. "Measurement of flexural displacement and strain in bending test based on digital image analysis." In Bituminous Mixtures and Pavements VI, 367–72. CRC Press, 2015. http://dx.doi.org/10.1201/b18538-53.
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"In Situ Curvature Measurements, Strains, and Stresses in the Case of Large Wafer Bending and Multilayer Systems." In III-V Compound Semiconductors, 375–410. CRC Press, 2016. http://dx.doi.org/10.1201/b10390-13.
Повний текст джерелаТези доповідей конференцій з теми "Bending Strain measurements"
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Marland, Chris, and Jeremy Greenwood. "Strain-Gauge Bending-Moment Measurements Used to Identify Wellbore Tortuosity." In SPE/IADC Drilling Conference and Exhibition. Society of Petroleum Engineers, 2015. http://dx.doi.org/10.2118/173039-ms.
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Feier, Ioan I., Brian N. Leis, Xian-Kui Zhu, Randall B. Stonesifer, John S. Stavrakas, and Daniel D’Eletto. "Experimental Strain Measurements on Large Diameter Mitered Pipe Joints." In 2010 8th International Pipeline Conference. ASMEDC, 2010. http://dx.doi.org/10.1115/ipc2010-31583.
Повний текст джерелаАнотація:
Historic pipeline construction utilized miter joints to enable small directional changes in pipeline routing, and this legacy construction remains in today’s pipelines. Current codes and regulations impose a limit on the maximum miter angle to less than three degrees of the total pipeline direction change, for pipeline operating with pressure over 30-percent SMYS (Specified Minimum Yield Stress). In anticipation of an operational pressure increase, an experimental and simulation effort was undertaken recently to determine the stress amplification due to miters in 30-inch diameter, 0.5-inch thick gas transmission pipelines. Experiments were conducted on six miter joints ranging in miter angle from 0° to 8° degrees of total pipeline direction change. Three of the miter joints were removed from the field (1950’s original installation), while the remaining three were specifically fabricated for the testing. All the miters considered were X42 pipeline steel. The miter pipe joint specimens were tested with pure pressurization, pure bending, and combined pressure and bending using a custom designed loading apparatus. Hoop and axial strains were measured using internally and externally mounted strain gauges. Pressure, as well as four point bending loads and deflections were recorded. One 3.8° field miter specimen was tested to burst. Experimental data, analytical solutions, and finite element results are compared at the miter joint section for the three loading cases. The study is limited to pipe radius to thickness ratio values of 30, and hence the results presented in this study are useful near this value. Results showed that miter joints increase stresses in the vicinity of the miter joint for pressure and/or bending loads. The peak stresses are on the exterior at the intrados. The pressure induced peak stress values increase proportional to the miter angle, and bending further increases the miter stress magnitudes. The ovalization effects significantly compromise the use of linear superposition of pressure and bending stresses even though material behavior remains elastic. Findings from this study demonstrate that in-situ miters on the pipeline in question do not compromise the integrity of the line, and stress additions for small angles over three degrees are comparable to stress risers occurring from normal pipeline features. The results of this work are important for performing structural integrity assessments and for making informed regulatory decisions for mitered pipeline operation.
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Sinotte, Tyler, and Olivier Bauchau. "Experimental Strain Measurements of Highly-Curved Blades." In Vertical Flight Society 75th Annual Forum & Technology Display. The Vertical Flight Society, 2019. http://dx.doi.org/10.4050/f-0075-2019-14576.
Повний текст джерелаАнотація:
This paper presents an experimental-numerical investigation on the axial strain of highly-curved blades. Models of the blades were analyzed using a 2-D finite element code, SectionBuilder, coupled with a comprehensive analysis code, Dymore, and first validated using strain measurements under a static tip load. Frequency responses were obtained under an impulsive load for each of the blades with multiple boundary conditions and compared with the numerical models. Experimental measurements under centrifugal loading from 0 up to 3300 RPM in a vacuum showed the effect of curvature on the axial strain, with significant bending strains observed in the responses for the curved blades that were also well captured by the numerical analysis. The present analysis shows that even moderate levels of out-of-plane curvature significantly increases the strain magnitudes, while higher levels of in-plane curvature have a much smaller impact.
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Konradsen, Bjørn. "Comparison of Bitumen’s Large Strain Viscoelastic Properties in Cables and Umbilicals to Small Strain Rheometer Measurements." In ASME 2016 35th International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2016. http://dx.doi.org/10.1115/omae2016-54091.
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When a steel wire armored cable or umbilical is bent, the armor wires will move relative to the underneath layer if the wires are free to move. If this movement is restricted by friction or stiff bitumen, the bending will result in shear stress in the armor wires. In the case of bitumen, the bitumen will behave as a viscoelastic material dependent on temperature, frequency, and strain. Comparison of measurements of bitumen with small and large strain shows that the viscoelastic properties of bitumen are highly affected by the size of the strain. Therefore, the small strain rheometer measurements are not suitable for describing the viscoelastic properties of bitumen in the case of repeated bending of the cable or umbilical to a certain curvature.
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Freitas, Rafael Luis, Celio Costa, Erica Chaves, and Sylvia Teixeira. "Environmental Stress Cracking on PVDF: ISO 22088-3 (Preliminary Data)." In ASME 2020 39th International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2020. http://dx.doi.org/10.1115/omae2020-18859.
Повний текст джерелаАнотація:
Abstract This study presents the effect of bending strain upon the structure and mechanical behavior of poly(vinylidene fluoride) (PVDF). Using the ISO 22088-3 Bent Strip Method, the PVDF samples were submitted to 3.5 % and 7.0 % strain in bending for 21 days. The unstrained and strained samples were characterized by Fourier Transformed Infrared Spectroscopy (FTIR), Differential Scanning Calorimetry (DSC) and Dynamic Mechanical Analysis (DMA) and tensile tests at 23 °C. The applied bending strain of 3.5% and 7.0 % resulted permanent deformation for both strains applied, which curvature was very close to 3.5% and 7%. The 7% strained samples showed stress-whitening, most likely due to the well-known cavitation phenomenon; while 3.5% strained samples no cavitation was seen. Infrared spectroscopy analysis indicates a mechanically induced α to β crystalline phase transition on the outer fibers as the bending strain increases. DSC measurements showed no change on crystallinity volume fraction and melting temperature as deformation increased. The DMA showed a shift on glass transition temperature (TG) to higher temperatures and the Elastic Modulus decreased as the bending strain increased for all temperatures. Reverse deformation had to be applied on the plastically deformed bending samples in order to straight them out to do the tensile tests. The tensile properties measured at room temperature showed the Young’s Modulus and Yield Stress decreasing as the applied bending strain increases. On the other hand, the yield strain rose as the bending strain increased.
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Laforte, Caroline, and Jean-Louis Laforte. "Tensile, Torsional and Bending Strain at the Adhesive Rupture of an Iced Substrate." In ASME 2009 28th International Conference on Ocean, Offshore and Arctic Engineering. ASMEDC, 2009. http://dx.doi.org/10.1115/omae2009-79458.
Повний текст джерелаАнотація:
In order to develop an effective deicing device using mechanical deformation of substrates, the adhesive and/or cohesive strains of ice at rupture were measured for three different modes of solicitation: tensile, twisting and bending. A total of 108 icing/deicing tests were conducted with aluminum and nylon samples covered with hard rime ice deposits 2, 5, and 10 mm thick strained at various strains rates in brittle regime at −10°C. Real time deformation was precisely monitored using a strain gage fixed to the A1 interface, and force by means of load cells and a torque-meter. Deicing strain was determined at the time of ice detachment, which corresponds to a visible, instant change in the slope of stress-strain curves. The mean values of deicing strains, ε %, measured in tensile, torsion and bending experiments are respectively, 0.037 ± 0.015%, 0.043 ± 0.023% and 0.004 ± 0.003% As for adhesion strength, the highest values were obtained in tension, 4 MPa ± 50%, and the lowest in bending, 0.014 MPa ± 36%. In torsion, the value was intermediary, at 1.26 MPa ± 67%. Measurements also showed that deicing stress and strain tended to increase with substrate roughness, whereas they decrease with increasing ice thicknesses. In summary, this work points out the effects of two major factors on ice adhesion strength, the solicitation mode and the ice thickness. Finally these results suggest that the first criteria for a mechanical deicing device has to satisfy to be effective is to have the capacity to generating a strain at around 0.04% ice/substrate interface.
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Ozkan, Istemi F., Daryl J. Bandstra, Chris M. J. Timms, and Arthur T. Zielinski. "Employing Visual Image Correlation for the Measurement of Compressive Strains for Arctic Onshore Pipelines." In ASME 2013 32nd International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/omae2013-10952.
Повний текст джерелаАнотація:
The Arctic onshore environment contains regions of discontinuous permafrost, where pipes may be subject to displacement-controlled bending in addition to high hoop stresses due to the pressurized fluids being transported. Considering the displacement-controlled nature of the deformations, strain-based design methodologies have been developed for permafrost pipelines when they are subject to bending and tension, which limit the longitudinal compressive and tensile strains. The widely accepted methodology in the industry to obtain the compressive strain capacity of line pipes subject to bending is to conduct Finite Element Analysis, incorporating material and geometrical nonlinearity calibrated against benchmark full-scale tests (bend tests) [1,2]. During these tests, compressive strains can be measured by various methods. The seemingly obvious choice is to apply strain gauges along the compression face of the specimen with respect to bending (intrados). This method will provide reasonable results until the compressive strain pattern begins to vary due to the initiation of buckle formation, which typically occurs shortly after yield. In order to measure average compressive strain beyond yield and up to buckling, the method used by C-FER Technologies (C-FER) involves using rotation measurement devices (inclinometers) to calculate the strain change between the most compressive and tensile fibres of the specimen (intrados and extrados, respectively) with respect to the bending direction. This value is then subtracted from the tensile strain gauge readings as measured by the strain gauge(s) located on the extrados of the specimen. The average compressive strain values derived from the inclinometer and extrados strain gauge measurements are based on the assumption that the plane sections remain plane. Recently, five large diameter pipes were bend-tested at C-FER’s testing facility in Edmonton, Alberta. In addition to the compressive strain measurement method used by C-FER described above (C-FER method), a visual image correlation (VIC) camera system was used to survey the strain distribution on the compressive face of the specimens. This paper gives a brief description of the test setup and instrumentation of this test program. The VIC camera setup and measurement technique are described and the overall strain distribution on the bending intrados as measured by the VIC cameras is presented. Strain measured by the VIC system is compared with gauge measurements at local points as well as the average compressive strain behaviour of the specimens obtained through the C-FER method described above. The results show that the VIC system can be a candidate to replace the conventional measurement techniques employed for compressive strain limit testing in support of strain-based design of arctic pipelines.
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Evans, Paul G., Paul P. Rugheimer, Michelle Roberts, Max G. Lagally, Chung-Hoon Lee, Yanan Xiao, Barry Lai, and Zhonghou Cai. "Direct Synchrotron X-Ray Microdiffraction Measurements of Strain and Bending in Micromachined Silicon Devices." In ASME 2004 International Mechanical Engineering Congress and Exposition. ASMEDC, 2004. http://dx.doi.org/10.1115/imece2004-62476.
Повний текст джерелаАнотація:
The manipulation of strain in micromachined silicon structures is an important aspect of the design of emerging mechanical and electronic devices. Strain also has a fundamental role in the formation of devices through its effects on surface processes in epitaxial growth including diffusion and can be an important tool for studying these processes. Microfabricated silicon structures offer the opportunity to control the strain at length scales of less than one micron to several hundred microns. Synchrotron x-ray microdiffraction allows simultaneous independent measurements of the strain and bending in these structures. Microdiffraction measurements show that bending is the dominant source of strain in a prototypical microfabricated Si bridge loaded at its ends by silicon nitride thin films. The total strain difference between the top and bottom of the bent bridge exceeds 0.1% in our prototype structures and can potentially be increased in optimized devices.
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Choquette, Jeremie J., Sylvain Cornu, Mohamed ElSeify, and Raymond Karé. "Understanding Pipeline Strain Conditions: Case Studies Between ILI Axial and ILI Bending Measurement Techniques." In 2018 12th International Pipeline Conference. American Society of Mechanical Engineers, 2018. http://dx.doi.org/10.1115/ipc2018-78577.
Повний текст джерелаАнотація:
In-Line inspection (ILI) tools consisting of combined sensor technologies provide a unique opportunity for operators to understand the conditions of pipelines. There is also an additional opportunity to contrast and validate individual sensing techniques against each other when their functionalities and purposes overlap. By using multi-technologies ILI measurements for strain, a pipeline operator can gain further insight into the pipeline strain behavior at any point along the length of the inspection. This paper establishes the relationship between ILI axial strain measurement tool data and conventional geometric strain data obtained from inertial measurement unit (IMU) based on data collected during in-service inspection of a 12″ liquid pipeline. Within any pipeline section, the tool configuration with circumferentially spaced strain sensors allows the use of appropriate analysis techniques to decompose the longitudinal strain into its primary components (axial, bending and out of roundness). The axial strain measurement tool sensing system provides an indirect measurement of bending strain that can be compared to the geometric measurement of bending strain determined from the pipeline trajectory as determined from the IMU analysis. Flexural bending strain resulting from horizontal directional drilling (HDD) is investigated in this paper. Convergences and divergences between the measurement techniques are presented. Data available from different strain technologies mounted on ILI tools offers an opportunity to conduct a comparative study and to provide a better understanding of a pipeline’s strain condition. This paper will present the framework for understanding the different strain measurement technologies and an investigation into the pipeline prior strain history (effects from fabrication, hydrostatic testing and external loads) and their corresponding impact on the material state at the time of inspection.
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Rogge, Renee D., Scott R. Small, Derek B. Archer, Michael E. Berend, and Merrill A. Ritter. "Validation of Digital Image Correlation Techniques for Strain Measurement in Biomechanical Test Models." In ASME 2013 Summer Bioengineering Conference. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/sbc2013-14540.
Повний текст джерелаАнотація:
Many previous biomechanical studies of bone and bone substitutes have estimated strains in these materials using strain gages. The purpose of this study was to compare digital image correlation (DIC) strain measurements to those obtained from strain gages in order to assess the applicability of DIC technology to common biomechanical testing scenarios. Compression and bending tests were conducted on aluminum alloy, polyurethane foam, and laminated polyurethane foam specimens. Results showed no significant differences in the principal strain values (or the variances) between strain gage and DIC measurements on the aluminum alloy and laminated polyurethane foam specimens. There were significance differences between the principal strain measurements of the non-laminated polyurethane foam specimens, but the deviation from the theoretical results was similar for both measurement techniques. In summary, DIC techniques provide similar results to those obtained from strain gages and also provide full field strain results.
Звіти організацій з теми "Bending Strain measurements"
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Holden, T., J. Root, and R. Hosbons. CWI1988-Andi-16 Neutron Diffraction of Axial Residual Strains Near a Crack in a Girth Weld. Chantilly, Virginia: Pipeline Research Council International, Inc. (PRCI), June 1988. http://dx.doi.org/10.55274/r0011389.
Повний текст джерелаАнотація:
The purpose of the present measurements was to measure the axial residual strains at the 6:00 position of a girth-weld in the presence of a crack which had been propagated a few millimeters from the inside diameter of the line pipe. Residual strains have been measured in the axial direction of a cracked girth weld in a line pipe. The crack was approximately 3 mm deep and ran 20 cm around the circumference near the mid weld. The residual strain distribution was compared to the distribution before the crack was introduced. The crack appears to introduce a large bending moment in the weld and the strain distribution shows that the tube is close to plastic collapse.
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Clapham, Lynann, and Vijay Babbar. PR-320-113706-R01 Neutron Diffraction Measurements of Residual Strain from Dents and Gouges in Pipelines. Chantilly, Virginia: Pipeline Research Council International, Inc. (PRCI), January 2020. http://dx.doi.org/10.55274/r0011643.
Повний текст джерелаАнотація:
Mechanical damage is one of the most prevalent causes of pipeline failure in North America and Europe. Gouged dents are much more likely to produce a failure than "plain" dents (i.e., a dent with no coincident metal loss or crack features), however the residual stresses around gouged dents are more difficult to model and predict. The Pipeline Aggression Rig (PAR) located in the St. Denis facility of GdF Suez was used to introduce backhoe-type gouging into pipe samples, which were nine pressurized pipe sections of varying grades. Five (5) samples were created using high-impact dynamic aggression (termed High Dynamic) and the other four (4) samples were created using lower impact energy and an axial-dragging mechanism (termed Low Dynamic). This project involved using neutron diffraction to measure the residual stresses in and around these gouged dents. Key findings are as follows: - In the undamaged regions of all samples, residual stresses were low (typically medium gouges were localized and residual stresses were largely bending-related: mild tensile at the outer wall/gouge base and compressive at the inner wall. - Residual stresses in and around one (1) High Dynamic severe gouge were tensile and critically high. - Residual stresses in and around Low Dynamic gouges had inconsistent and unpredictable residual stress magnitudes and distributions. PRCI members will find value in this information for understanding the severity of gouges in pipelines, for use in stress modelling verification, and, finally, for understanding characterizing MFL signals from ILI tools.
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Graville. L51764 Hydrogen Cracking in the Heat-Affected Zone of High-Strength Steels-Year 2. Chantilly, Virginia: Pipeline Research Council International, Inc. (PRCI), March 1997. http://dx.doi.org/10.55274/r0010170.
Повний текст джерелаАнотація:
During year 1 of this project a test to evaluate the sensitivity of the heat affected zone (HAZ) to hydrogen cracking was developed. This was in response to a need for a test which provided unambiguous results in contrast to existing test methods which often led to difficulties in interpretation. For example, WIC tests usually cracked in the weld metal rather than the HAZ and therefore did not produce a clear indication of the sensistivity of the HAZ. The new test involves a machined notch which can be placed in the HAZ thus forcing crack initiation to occur in the desired region. A further advantage of the new test is that it is quantitative with each test specimen providing a measure of the sensitivity of the HAZ in that test. Existing tests are usually of the crack/no-crack type requiring a series of tests at different preheats to be carried out in order to establish a critical value. This is an expensive, time-consuming approach. The new test measures the deflection to first load drop (normally the onset of significant cracking) when the welded specimen is loaded in bending. It was also shown during the first year of the project that the simple geometry of the test lends itself to easy analysis enabling the stress/strain distribution to be calculated by finite element analysis. The quantitative measurement of susceptibility in the test enabled the cracking of more complex welds to be predicted on the basis of a local critical hydrogen model. The objective of the work was to extend the notched bend test to the evaluation of weld metal sensitivity to hydrogen cracking. The experiments were designed to determine whether the test could discriminate between two different weld metals and to study the effects of reducing hydrogen content. In addition, finite element analysis of the weld metal test was carried out and finite difference analysis used to predict the local hydrogen concentration. This work modifies the notched bend test, developed for evaluating the sensitivity of the heat affected zone (HAZ), to allow the evaluation of weld metal. The results showed that weld metal could readily be evaluated, with the test discriminating among weld metals of different composition and hydrogen contact. Finite element analysis was undertaken and showed that for the two weld metals tested, cracking occurred at the same local stress when the hydrogen content was the same, despite differences in strength. A finite model was used to calculate the distribution of hydrogen as a function of aging time. Although the general trends were confirmed by the experimental measurements of hydrogen content, there was considerable scatter attributed to the small hydrogen volumes measured.