Academic literature on the topic 'FBG fatigue performance'
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Journal articles on the topic "FBG fatigue performance"
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Zhang, Naizhong, Suzana Turk, Claire Davis, Wing K. Chiu, Tommy Boilard, and Martin Bernier. "Fatigue Performance of Type I and Type II Fibre Bragg Gratings Fabricated by Femtosecond Laser Inscription through the Coating." Sensors 22, no. 22 (November 15, 2022): 8812. http://dx.doi.org/10.3390/s22228812.
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Strain sensing technology using fibre Bragg grating (FBG) sensors is an attractive capability for aerospace structural health monitoring (SHM) and assessment because they offer resistance to harsh environments, low maintenance, and potential for high density and high strain sensing. The development of FBG inscription techniques through the fibre polymer coating using infrared (IR) lasers has overcome the mechanical weaknesses introduced by removal of the fibre coating, which is typically required for conventional UV laser inscription of FBGs. Type I and Type II femtosecond gratings are fabricated using through-coating inscription techniques, but the higher laser energy used for Type II gratings damages the glass fibre core, impacting mechanical performance. This paper investigates the fatigue performance of Type I and Type II through-coating FBG sensors with different fibre geometries and photosensitisation approaches to evaluate their overall reliability and durability, with a view to assess their performance for potential use in civil and defence SHM applications. The fatigue performance of FBG sensors was assessed under high-strain and high-frequency mechanical loading conditions by using a custom-designed electro-dynamically actuated loading assembly. In addition, pre- and post-fatigue microscopic analyses and high-resolution reflection spectrum characterisation were conducted to investigate the failure regions of the fibres and the effect of fatigue loading on reflection spectrum features. As expected, Type I gratings had a significantly higher fatigue life compared to Type II gratings. However, Type II gratings performed significantly better than conventional UV laser-inscribed FBGs and electrical foil strain gauges. Type II gratings withstand higher temperatures, and are therefore more suitable for application in harsh environments.
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Zhang, Naizhong, Claire Davis, Wing K. Chiu, Tommy Boilard, and Martin Bernier. "Fatigue Performance of Type I Fibre Bragg Grating Strain Sensors." Sensors 19, no. 16 (August 12, 2019): 3524. http://dx.doi.org/10.3390/s19163524.
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Although fibre Bragg gratings (FBGs) offer obvious potential for use in high-density, high-strain sensing applications, the adoption of this technology in the historically conservative aerospace industry has been slow. There are several contributing factors, one of which is variability in the reported performance of these sensors in harsh and fatigue prone environments. This paper reports on a comparative evaluation of the fatigue performance of FBG sensors written according to the same specifications using three different grating manufacturing processes: sensors written in stripped and re-coated fibres, sensors written during the fibre draw process and sensors written through fibre coating. Fatigue cycling of the fibres is provided by a customized electro-dynamically actuated loading assembly designed to provide high frequency and amplitude loading. Pre- and post-fatigue microscopic analysis and high-resolution transmission and reflection spectra scanning are conducted to investigate the fatigue performance of FBGs, the failure regions of fibres as well as any fatigue-related effects on the spectral profiles. It was found that because of the unique fabrication method, the sensors written through the fibre coating, also known as trans-jacket FBGs, show better fatigue performance than stripped and re-coated FBGs with greater control possible to tailor the optical reflection properties compared to gratings written in the draw tower. This emerging method for inscription of Type I gratings opens up the potential for mass production of higher reflectivity, apodised sensors with dense or complex array architectures which can be adopted as sensors for harsh environments such as in defence and aerospace industries.
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Fan, Guo-Xi, Fan-Tong Lin, Peng Li, Ji-Gang Han, Huai-Shuai Shang, Ye Wang, and Han Zheng. "Strain Conditions Monitoring on Corroded Prestressed Steel Strands in Beams Based on Fiber Bragg Grating Sensors." Sensors 20, no. 8 (April 17, 2020): 2288. http://dx.doi.org/10.3390/s20082288.
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Fiber Bragg Grating (FBG) sensors, with excellent properties, have been widely adopted to monitor the mechanical parameters in civil engineering in recent years. On the other hand, the current study on fatigue performance of corroded prestressed steel strands is still limited, and this is mainly because the long-term strain conditions monitoring is difficult to conduct. Based on the aforementioned considerations, a total of six beam specimens were fabricated in this study. The loading mode of four points bending was adopted in the form of sinusoidal waves in the experiments. On basis of the experimental results, it can be concluded that the fatigue life of the beam decreases sharply with the increase of the corrosion rate of steel strands. Besides, with the increase of the maximum fatigue load, the fatigue life of the beam will decrease significantly. Furthermore, the existing fatigue damage of steel strand inside the beam before corrosion may further accelerate its fatigue failure. As a result, the fatigue life of the beam is reduced because of the stress concentration. Under the same external load, the strain increment and the residual strain of steel strands in the stages of loading and unloading after corrosion increase significantly compared with other stages, while the existing residual strain always shows an increasing trend at various static loading stages. Therefore, the corrosion of steel strand seriously affects not only its mechanical properties, but also its fatigue performance. Finally, the FBG sensors are capable of measuring the steel strand strain, as well as the long-term strain conditions.
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Wang, Licheng, Jigang Han, and Yupu Song. "Fatigue performance monitoring of full-scale PPC beams by using the FBG sensors." Smart Structures and Systems 13, no. 6 (June 25, 2014): 943–57. http://dx.doi.org/10.12989/sss.2014.13.6.943.
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Zhang, Meng, Weifang Zhang, Xiaobei Liang, Yan Zhao, and Wei Dai. "Detection of fatigue crack propagation through damage characteristic FWHM using FBG sensors." Sensor Review 40, no. 6 (October 26, 2020): 665–73. http://dx.doi.org/10.1108/sr-03-2020-0056.
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Purpose Crack damage detection for aluminum alloy materials using fiber Bragg Grating (FBG) sensor is a kind of structure health monitoring. In this paper, the damage index of full width at half maximum (FWHM) was extracted from the distorted reflection spectra caused by the crack-tip inhomogeneous strain field, so as to explain the crack propagation behaviors. Design/methodology/approach The FWHM variations were also investigated through combining the theoretical calculations with simulation and experimental analyses. The transfer matrix algorithm was developed to explore the mechanism by which FWHM changed with the linear and quadratic strain. Moreover, the crack-tip inhomogeneous strain field on the specimen surface was computed according to the digital image correlation measurement during the experiments. Findings The experimental results demonstrated that the saltation points in FWHM curve accorded with the moments of crack propagation to FBG sensors. Originality/value The interpretation of reflected spectrum deformation mechanism with crack propagation was analyzed based on both simulations and experiments, and then the performance of potential damage features – FWHM were proposed and evaluated. According to the correlation between the damage characteristic and the crack-tip location, the crack-tip of the specimen could be measured rapidly and accurately with this technique.
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Wei, Guoqian, Shanshan Li, Yongxing Guo, and Zhang Dang. "Fiber Bragg Gratings Based Cyclic Strain Measuring of Weld Toes of Cruciform Joints." Applied Sciences 9, no. 14 (July 23, 2019): 2939. http://dx.doi.org/10.3390/app9142939.
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The real weld toe geometry is generally not mathematically perfect, resulting in obvious stress concentration effects, both on the weld section and along the longitudinal direction of the weld toe. The true stress-strain state at the local weld toe directly affects the fatigue performance and behavior of the welded structure. Therefore, a Fiber Bragg Grating (FBG) sensor based method for testing the cyclic strain at the weld toe was proposed. Cruciform welded joints were fabricated as specimens on which FBG sensors were arranged at several characteristic points along the weld toe curve. Strains at all the characteristic points under cyclic tensile load were measured and recorded, which showed the proposed measuring method could accurately obtain the complete local strain time histories along the weld toe. The strain time histories clearly reflected the cyclic hardening phenomenon in the early stage and the plastic yielding phenomenon in the final stage. Furthermore, based on the cyclic stress-strain constitutive model of the weld material, the stress-strain response curves of all the characteristic points were drawn. Combined with the fatigue fracture morphology, the mechanism of the unsynchronized initiation of the multiple cracks in the weld toe was investigated.
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Choi, Mi Jin, Jin Seong Kim, Young Kyu Kim, Jong Hoon Kim, Ko Woon Choi, Chan Yik Park, and Jong Heon Kim. "Development of Sensor Integrated Composite Wing Structure." Advanced Materials Research 123-125 (August 2010): 903–6. http://dx.doi.org/10.4028/www.scientific.net/amr.123-125.903.
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Demands for improved aerial vehicle performance have led to the increasing use of composite materials. However, the mechanical behavior and failure modes of composites are not characterized as well as metals, and damages may be more difficult to detect. To overcome this, there is a demand to develop a structural health monitoring (SHM) system for composite aerial vehicles. This paper presents the development of sensor integrated composite wing structure, which is an essential part of SHM system. The composite wing structure was manufactured using an autoclave process, and Fiber Bragg Grating (FBG) optical sensor and piezoelectric (PZT) sensor were installed. The optimal number and location of each sensor system are determined based on the experimental results and Finite Element Analysis (FEA). Installation procedures for FBG and PZT sensor system are developed and validated using tension-tension fatigue tests over 106 cycles.
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Meng, Lijun, Xinyu Li, and Xin Tan. "Magnetic suction compression-type gap sensor based on fiber Bragg grating sensing." Sensor Review 41, no. 2 (February 26, 2021): 144–52. http://dx.doi.org/10.1108/sr-11-2020-0267.
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Purpose A fiber Bragg grating (FBG) sensor was designed to measure the door gap of automobile bodies. Design/methodology/approach The gap sensor was designed through a combination of the sliding wedge and cantilever beam, involving a magnetic force installation and arc structure of the force transmission point. Moreover, the sliding block adopted an anti-magnetic and wear-resistant material and the temperature compensation of the two FBGs was conducted. The magnetic force and contact stress of the sensor were examined to ensure that the sensor exhibited a certain magnetic attraction force and fatigue life. The performance of the gap sensor was examined experimentally. Findings The sensor could measure gaps with dimensions of 5 mm to 11 mm, with a sensitivity and measurement accuracy of 150.9 pm/mm and 0.0063% F.S., respectively. Moreover, the sensor exhibited a small gap sensitivity, with a repeatability error of 0.15%, anti-creep properties and magnetic interference abilities. Originality/value The sensor is compact and easy to install, as well as use for multiple sensor locations, with a maximum size of 43 mm, a mass of 26 g and installation type of magnetic suction. It can be used for high-precision static and dynamic measurements of the door inner clearance with a resolution of 0.013 mm to improve the efficiency of internal clearance on-line analysis and assembly quality inspection.
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Hureau, Thomas J., Joshua C. Weavil, Taylor S. Thurston, Hsuan-Yu Wan, Jayson R. Gifford, Jacob E. Jessop, Michael J. Buys, Russell S. Richardson, and Markus Amann. "Pharmacological attenuation of group III/IV muscle afferents improves endurance performance when oxygen delivery to locomotor muscles is preserved." Journal of Applied Physiology 127, no. 5 (November 1, 2019): 1257–66. http://dx.doi.org/10.1152/japplphysiol.00490.2019.
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We sought to investigate the role of group III/IV muscle afferents in limiting endurance exercise performance, independently of their role in optimizing locomotor muscle O2 delivery. While breathing 100% O2 to ensure a similar arterial O2 content ([Formula: see text]) in both trials, eight male cyclists performed 5-km time trials under control conditions (HCTRL) and with lumbar intrathecal fentanyl (HFENT) impairing neural feedback from the lower limbs. After each time trial, common femoral artery blood flow (FBF) was quantified (Doppler ultrasound) during constant-load cycling performed at the average power of the preceding time trial. The assessment of end-tidal gases, hemoglobin content and saturation, and FBF facilitated the calculation of leg O2 delivery. Locomotor muscle activation during cycling was estimated from vastus lateralis EMG. With electrical femoral nerve stimulation, peripheral and central fatigue were quantified by pre- to postexercise decreases in quadriceps twitch torque (ΔQtw) and voluntary activation (ΔVA), respectively. FBF (~16 mL·min−1·W−1; P = 0.6), [Formula: see text] (~24 mL O2/dL; P = 0.9), and leg O2 delivery (~0.38 mL O2·min−1·W−1; P = 0.9) were not different during HCTRL and HFENT. Mean power output and time to completion were significantly improved by 9% (~310 W vs. ~288 W) and 3% (~479 s vs. ~463 s), respectively, during HFENT compared with HCTRL. Quadriceps muscle activation was 9 ± 7% higher during HFENT compared with HCTRL ( P < 0.05). ΔQtw was significantly greater in HFENT compared with HCTRL (54 ± 8% vs. 39 ± 9%), whereas ΔVA was not different (~5%; P = 0.3) in both trials. These findings reveal that group III/IV muscle afferent feedback limits whole body endurance exercise performance and peripheral fatigue by restricting neural activation of locomotor muscle. NEW & NOTEWORTHY Group III/IV muscle afferent feedback facilitates endurance performance by optimizing locomotor muscle O2 delivery but also limits performance by restricting neural drive to locomotor muscle. To isolate the performance-limiting effect of these sensory neurons, we pharmacologically attenuated their central projection during a cycling time trial while controlling for locomotor muscle O2 delivery. With no difference in leg O2 delivery, afferent blockade attenuated the centrally mediated restriction in motoneuronal output and improved cycling performance.
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Laginestra, Fabio Giuseppe, Markus Amann, Emine Kirmizi, Gaia Giuriato, Federico Ruzzante, Anna Pedrinolla, Camilla Martignon, Cantor Tarperi, Federico Schena, and Massimo Venturelli. "Electrical Stimulation-induced Fatigue In The Contralateral Leg Impairs Endurance Exercise Performance." Medicine & Science in Sports & Exercise 52, no. 7S (July 2020): 933. http://dx.doi.org/10.1249/01.mss.0000685696.07316.fb.
Full textConference papers on the topic "FBG fatigue performance"
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RAHMATIAN, ARASH, ASHUTOSH BAGCHI, and MICHELLE NOKKEN. "Performance Evaluation of FBG Sensors under Fatigue and Weathering." In Structural Health Monitoring 2015. Destech Publications, 2015. http://dx.doi.org/10.12783/shm2015/129.
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"Trans-Jacket Fibre Bragg Gratings for In-Situ Health Monitoring of Defence Platforms in Harsh Environments." In Structural Health Monitoring. Materials Research Forum LLC, 2021. http://dx.doi.org/10.21741/9781644901311-6.
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Abstract. Packaged optical fibre sensors offer excellent strength and resistance to environmental degradation, but the reported reliability and durability of fibres containing fibre Bragg gratings (FBGs) varies greatly. This is partly due to the fabrication methodologies used to create the sensors. The trans-jacket grating inscription technique uses an infrared laser to write gratings into the fibre core through the polymer coating. This method eliminates the need for harsh coating removal processes and exposure of the glass fibre core and thus dramatically reduces fibre damage during grating fabrication. In addition, the automated trans-jacket inscription process introduces greater flexibility to control the writing parameters, facilitating a consistent process for producing robust, fatigue resistant distributed FBG sensing arrays with reliable and repeatable performance that could revolutionise their application in structural health monitoring (SHM). This paper reports on the durability and reliability of Bragg gratings with different fibre geometries, dopants, and photo-sensitising approaches to compare the overall fatigue performance of trans-jacket FBG sensors. Both type I gratings which are inscribed using a laser power intensity below the damage threshold of the glass core, and type II gratings which are inscribed exceeding this threshold, are considered. The fatigue performance of these FBG sensors was assessed using a custom designed electro-dynamically actuated loading assembly. It is concluded that type I trans-jacket gratings have a significantly higher fatigue life compared to type II gratings for the same fatigue loading regime. Despite the lower fatigue life, type II trans-jacket gratings are found to perform significantly better than conventional electrical foil gauges. Therefore, trans-jacket gratings have significant potential for application as dense sensing arrays in harsh operational environments in defence and aerospace industries.
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Eaton, Ammon N., Seyed Mostafa Safdarnejad, John D. Hedengren, Kristie Moffat, Casey B. Hubbell, David V. Brower, and Alexis D. Brower. "Post-Installed Fiber Optic Pressure Sensors on Subsea Production Risers for Severe Slugging Control." In ASME 2015 34th International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2015. http://dx.doi.org/10.1115/omae2015-42196.
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Fiber optic sensors have gained increasing use in monitoring offshore structures. The sensors have successfully monitored flowlines, umbilicals, wells, Tension Leg Platform (TLP) tendons, production and drilling risers, and mooring lines. Fiber optic sensors are capable of monitoring strain, temperature, pressure, and vibration. While the success of fiber optic monitoring has been clearly demonstrated, the sensors are now under consideration for automation applications. This paper details the plausibility of using pressure measurements from post-installed fiber Bragg grating (FBG) sensors with Model Predictive Control (MPC) to suppress severe slugging in subsea risers. Prior control schemes demonstrate that slugging is mitigated using a topside choke valve. The most effective methods use a pressure measurement immediately upstream of the touchdown zone of the riser; however, the majority of production risers do not have pressure sensing at that location. With advances in subsea clamp design and bonding it is now possible to install a non-penetrating FBG sensor to monitor pressure near the touchdown zone without shutting down production. Stabilizing the two phase flow both reduces vibration-induced fatigue and has the potential to allow increased throughput with relaxed topside processing constraints. MPC predicts and adjusts for disturbances to avoid pressure and flow instability. The performance of the controller is influenced by sensor location, choke valve response time, and riser geometry. This study demonstrates that severe riser slugging is effectively controlled with MPC and a post-installed, non-penetrating FBG sensor.
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Gui, Feng, Colum Holtam, Brandon Gerst, and Ramgopal Thodla. "Fatigue Crack Growth Behavior of Embedded Flaws in Sour Pipelines." In ASME 2016 35th International Conference on Ocean, Offshore and Arctic Engineering. American Society of Mechanical Engineers, 2016. http://dx.doi.org/10.1115/omae2016-54384.
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DNV-OS-F101 Appendix A provides procedures for the assessment of circumferential flaws located in subsea pipe girth welds using fracture mechanics methods, commonly referred to as engineering critical assessment (ECA). The purpose of the ECA approach is to provide critical flaw dimensions for given material properties and loading conditions in a conservative way. The results of the assessment are used to derive weld flaw acceptance (or weld repair) criteria to be used during pipeline installation. An ECA will typically consider flaws under installation and operation loading conditions, including fracture and fatigue crack growth (FCG) calculations. Internal and external surface-breaking flaws are assessed, along with embedded flaws. DNV-OS-F101 provides guidance on the appropriate FCG law to be used for the assessment of each flaw type under operational loading. For internal surface flaws exposed to sour production fluids (i.e. containing H2S) FCG rates (FCGRs) are known to be significantly higher than in air and, in the absence of relevant published data, project-specific testing is commonly performed to quantify fatigue performance. The recommendation for the assessment of embedded flaws is to use an air curve, as long as it can be substantiated that the fatigue performance is not reduced due to the environment. It has been demonstrated that the FCG behavior of C-Mn pipeline steels exposed to sour environments is dominated by bulk hydrogen charging effects, i.e. hydrogen charging by absorption from the exposed surfaces rather than the corrosion process at the crack tip. Therefore, it is expected that an embedded (or external) flaw in a sour pipeline will be located in steel containing absorbed hydrogen. This paper describes the results of an investigation aimed at understanding and quantifying the FCG behavior of embedded flaws in sour pipelines. For the purposes of this work, an embedded flaw refers to a crack propagating in hydrogen charged material but whose crack tip is not directly exposed to the sour environment. Hydrogen diffusion modelling and simulation studies were performed to predict the through wall hydrogen concentration in standard fracture mechanics specimens based on sour environmental conditions. Two novel test methods were developed to accurately measure FCGRs in hydrogen charged steel, one for single edge notched bend (SENB) specimens and one for compact tension (CT) specimens. FCGR tests were carried out using both methods. The FCGRs measured in hydrogen charged API 5L grade X65 pipeline steel were significantly higher than in air. In some cases, the observed FCGRs in hydrogen charged steel were higher than for specimens fully immersed in the sour environment. This is believed to be due to reduced environmental crack closure/blunting effects; the steel is charged with hydrogen, but there is no active corrosion process occurring inside the crack. The results of the present study indicate that the use of an air FCG curve for embedded (or external) flaws located in hydrogen charged steel may be non-conservative. Further work is required to establish the relationship between FCGR and hydrogen concentration in steel and to evaluate the implications for pipeline ECA calculations.
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Billiar, Kristen L., and Michael S. Sacks. "Long-Term Mechanical Fatigue Response of Porcine Bioprosthetic Heart Valves." In ASME 1998 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 1998. http://dx.doi.org/10.1115/imece1998-0165.
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Abstract Porcine bioprosthetic heart valves (PBHVs) have excellent short-term durability, but have generally poor long-term performance. Although the exact mechanism is still unknown, it is almost certain that mechanical factors play a significant role in PBHV failure. Aortic valve cusps are highly anisotropic with a complex, non-uniform structure (Fig. 1, top). It is therefore understandable that to date there have been no quantitative studies to determine how mechanical behavior is altered by mechanical fatigue. In this study we performed biaxial mechanical tests and uniaxial failure tests on cusps harvested from 4mmHg glutaraldehyde treated PBHVs loaded intact up to 300 × 106 cycles.
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Mann, Jonathan, Chris Currie, Jennifer Borg, and Norman Platts. "Further Development of Fatigue Crack Growth Expressions for Austenitic Stainless Steels in PWR Water and Additional Validation of the WTKR Method." In ASME 2020 Pressure Vessels & Piping Conference. American Society of Mechanical Engineers, 2020. http://dx.doi.org/10.1115/pvp2020-21585.
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Abstract The primary water environment in a Pressurised Water Reactor (PWR) can have a significantly detrimental effect on the Fatigue Crack Growth (FCG) rates of Austenitic Stainless Steels. Expressions to describe FCG in these materials are provided in ASME Code Case N-809, which was based on results from tests performed under isothermal, simple waveform loading. A previous re-analysis of a much larger database of FCG results highlighted improvements to the N-809 model for nominally low carbon material grades. For non-isothermal and/or complex mechanical loading conditions, further improvements of the prediction of FCG rates were demonstrated by using the Weighted Temperature and K-Rate (WTKR) method. The combined use of improved FCG expressions and the WTKR method is expected to provide significant reductions in over-conservatism when used to assess plant-realistic loading transients. This paper describes the further development of revised expressions to describe the effect of PWR environments on FCG in austenitic stainless steels. The analysis is extended to a wider range of different types of stainless steel, including nominally high carbon 304 variants and 316-type materials. The analysis highlights that previously specified differences in FCG behaviour between nominally low and high carbon materials are minimal, and that 316-type materials exhibit improved performance in these environments. Further testing has also been performed using non-isothermal and complex waveform loading conditions, and these results are used as additional validation of the WTKR methodology.
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Birenis, Domas, Yuhei Ogawa, Hisao Matsunaga, Osamu Takakuwa, Junichiro Yamabe, Øystein Prytz, and Annett Thøgersen. "Hydrogen-Assisted Fatigue Crack Propagation in a Commercially Pure BCC Iron." In ASME 2018 Pressure Vessels and Piping Conference. American Society of Mechanical Engineers, 2018. http://dx.doi.org/10.1115/pvp2018-84783.
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Hydrogen effect on fatigue performance of commercially pure BCC iron has been studied with a combination of various electron microscopy techniques. The fatigue crack growth (FCG) in gaseous hydrogen was found to consist of two regimes corresponding to a slightly accelerated regime at relatively low stress intensity factor range, ΔK, (Stage I) and the highly accelerated regime at relatively high ΔK (Stage II). These regimes were manifested by the intergranular and quasicleavage types of fractures respectively. Scanning electron microscopy (SEM) observations demonstrated an increase in plastic deformation around the crack wake in the Stage I, but considerably lower amount of plasticity around the crack path in the Stage II. Transmission electron microscopy (TEM) results identified dislocation cell structure immediately beneath the fracture surface of the Stage I sample, and dislocation tangles in the Stage II sample corresponding to fracture at high and low plastic strain amplitudes respectively.
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Guillemette, R. "The Development and Implementation of Thermal Spray Coatings for Helicopter Components." In ITSC 1998, edited by Christian Coddet. ASM International, 1998. http://dx.doi.org/10.31399/asm.cp.itsc1998p1033.
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Abstract Many components in helicopter dynamics systems depend on hard, wear resistant coatings for reliable performance. Component replacement times are currently limited by performance of these coatings in many cases. Thermal spray coatings have been evaluated for these applications to replace nickel and chromium electroplate. The effect of coatings on fatigue strength is quantified by a strain limit concept to reduce test requirements during development phase. Full scale bench testing and coupon wear testing were conducted to reveal large improvement in sliding and fretting wear resistance. A fine porosity network in thermal spray coatings, high hardness and high fatigue strength are shown to be the main contributors to improved wear performance. Thermal spray coatings also exhibited enhanced corrosion resistance in salt fog and crevice corrosion conditions. These data permitted implementation on several critical helicopter components.
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Ogawa, Yuhei, Dain Kim, Hisao Matsunaga, and Saburo Matsuoka. "Evaluation of the Compatibility of High-Strength Aluminum Alloy 7075-T6 to High-Pressure Gaseous Hydrogen Environments." In ASME 2018 Pressure Vessels and Piping Conference. American Society of Mechanical Engineers, 2018. http://dx.doi.org/10.1115/pvp2018-84321.
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To develop safer and more cost-effective high-pressure hydrogen tanks used in fuel cell vehicles (FCVs), the metallic materials with the following three key properties, i.e. lightweight, high strength and excellent resistance to hydrogen embrittlement should be explored. In this study, the compatibility of high-strength, precipitation-hardened aluminum alloy 7075-T6 was evaluated according to the four types of mechanical testing including slow-strain rate tensile (SSRT), fatigue life, fatigue crack growth (FCG) and fracture toughness tests in high-pressure gaseous hydrogen environments (95 ∼ 115 MPa) at room temperature. Even though numerous publications have previously reported significant degradation of the mechanical properties of 7075-T6 in some hydrogenating environments, such as moist atmosphere, the understanding with regards to the performance of this alloy in high-pressure gaseous hydrogen environments is still lacking. In SSRT tests, the alloy showed no degradation of tensile strength and ductility. Furthermore, fatigue life, fatigue crack growth and fracture toughness properties were also not degraded in hydrogen gas. Namely, it was first demonstrated that the material has big potential to be used for hydrogen storage tanks for FCVs, according to its excellent resistance to high-pressure gaseous hydrogen.
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Malyukova, Margarita G., Sviatoslav A. Timashev, and Igor L. Maltsev. "Practical Method of Updating Stochastic Remaining Life of Pipelines Using ILI Data." In 2004 International Pipeline Conference. ASMEDC, 2004. http://dx.doi.org/10.1115/ipc2004-0295.
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The paper describes a new practical method of updating the stochastic remnant life of pipelines with defects using ILI data. The paper describes a comprehensive algorithm for assessing pipeline remnant life taking into account the stochastic results of in-line inspection (ILI). It is assumed that the pipeline segment wall has a longitudinal external crack of semi-elliptical form and is described by the J-integral. The limit state function (LSF) is described as the difference of the critical and current value of the J-integral. The latter is calculated for the current time of pipe performance and is assumed known due to monitoring of the pumping equipment. The critical crack depth is defined using the notion of fracture toughness and the J-integral approach. The algorithm contains solutions of three sequentially interconnected problems. First, the deterministic problem of fatigue crack growth (FCG) is analyzed. Then the stochastic FCG is analyzed. The probability of failure assessment algorithm is designed on the basis of the authors’ version of the adaptive important sampling (AIS) procedure. The main steps of the AIS algorithm are described in detail. The samples are generated in such a way, that at all times a majority of samples belong to the fracture region. Finally, the results of the latest ILI are fused into the algorithm, providing best possible assessment of pipeline remnant life as a random variable. The remnant life update for pipeline segment with crack-like defects using ILI data takes into account three possible outcomes: defect not discovered: defect is discovered but not measured; defect is discovered and measured. This result permits solving most important problems of pipeline maintenance: prioritization of pipeline segments for repair/rehabilitation; optimization of the time between ILI; minimization of pipe operational risk. Two real cases are described of assessing the probability of fracture/leak of a pipeline section with an external crack at different periods of its performance. The described approach currently is being generalized for the case of multiple stress corrosion SC cracks.