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Letteratura scientifica selezionata sul tema "INCREASED TOUGHNESS"

Autore: Grafiati

Pubblicato: 11 settembre 2023

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Articoli di riviste sul tema "INCREASED TOUGHNESS"

Ruan, Shiling, John J. Lannutti, Stan Prybyla e Robert R. Seghi. "Increased fracture toughness in nanoporous silica–polyimide matrix composites". Journal of Materials Research 16, n. 7 (luglio 2001): 1975–81. http://dx.doi.org/10.1557/jmr.2001.0270.

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Silica–polyimide nanocomposites were prepared by hot-pressing mixtures of polyimide and highly porous silica powder. The silica powder was produced using a sol-gel process that generates pores as small as 15 Å. The effects of loading, cure, and post-cure temperature on fracture toughness were investigated. The addition of silica particles improved the fracture toughness from 0.5 to a maximum of 1.9 MPa m0.5. However, fracture toughness dropped at silica weight percentages ≥30%. The cure and post-curing temperatures have a strong influence on toughness; post-curing exposure ≥400 °C reduced toughness. Transmission electron microscopy examination of the fracture surfaces indicated that the toughness improvements may occur at the nanometer scale due to crack pinning and branching induced by the nanoporous silica particles.

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Lee, S. M., E. Pippel, U. Gosele, C. Dresbach, Y. Qin, C. V. Chandran, T. Brauniger, G. Hause e M. Knez. "Greatly Increased Toughness of Infiltrated Spider Silk". Science 324, n. 5926 (24 aprile 2009): 488–92. http://dx.doi.org/10.1126/science.1168162.

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Konrad, Jean-Marie, e Julie Cummings. "Fracture toughness of frozen base and subbase soils in pavement". Canadian Geotechnical Journal 38, n. 5 (1 ottobre 2001): 967–81. http://dx.doi.org/10.1139/t01-032.

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Temperature distribution in the pavement structure, moisture distribution in granular soils, modulus of the asphalt concrete, and fracture toughness of material in the pavement structure strongly influence the propagation and spacing of thermal contraction cracks. Fracture toughness was determined for frozen sand (subbase layer) and frozen crushed stone (base layer) by adapting established fracture mechanics test procedures recommended in American Society for Testing and Materials standard test method E399-83 for metals. It was established that fracture toughness increases with decreasing temperature and increasing volumetric ice content. For a temperature of 5°C, the fracture toughness of frozen crushed stone increased almost linearly from 0.05 to 0.40 MPa·m0.5 when the volumetric ice content increased from 6 to 14%. For frozen sand, the fracture toughness KIC in a wedge-opening mode increased from 0.04 to 0.70 MPa·m0.5 when the volumetric ice content increased from 8 to 28%. It was also established that the fracture toughness of frozen soil decreases with decreasing soil average grain size according to a logarithmic law.Key words: fracture, toughness, experimental, frozen, granular soil, pavement.

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Van Niekerk, Anna Maria Susanna, e Hester E. Roets. "The Psycho-Educational Practice of Mental Toughness in Dealing with Trauma". International Journal of Psychological Studies 9, n. 4 (20 novembre 2017): 83. http://dx.doi.org/10.5539/ijps.v9n4p83.

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This study investigated whether an intervention program, which was developed within the psycho-educational field, could support traumatized people to increase their mental toughness. This program is based on the four components of mental toughness, namely control, challenge, commitment and confidence. A valid and reliable psychometric instrument, the Mental Toughness Questionnaire 48 (MTQ48), has been successfully used in both the corporate and sports psychology world to determine people’s mental toughness but has never before been tested in supporting traumatised people. Many corresponding aspects between mental toughness and trauma were discovered and used to compile a psycho-educational intervention program to support traumatized persons to develop increased mental toughness. An action research design was employed, where both qualitative as well as quantitative methods were used. Eight traumatized people participated in the research. The results of the study indicated that seven of the eight participants’ overall mental toughness increased after the intervention program, and four of the eight participants’ mental toughness components increased. All respondents indicated that they could better deal and cope with their trauma. The conclusion could be drawn that the psycho-educational intervention program, which was based on enhancing mental toughness, was successful in supporting the traumatised participants to increase their mental toughness.

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Wang, Wenke, Yang Guo, Yuanbo Li e Zhengning Li. "Fracture Toughness of Different Region Materials from a Dissimilar Metal Welded Joint in Steam Turbine Rotor". Coatings 12, n. 2 (29 gennaio 2022): 174. http://dx.doi.org/10.3390/coatings12020174.

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This study systematically evaluated the fracture toughness of a CrMoV/NiCrMoV dissimilar metal welded joint (DMWJ) with buttering layer technology in a steam turbine rotor. The fracture resistance curves and parameters of base metals (BM-1 and BM-2), weld metal (WM), buttering layer (BL), and heat-affected zones (HAZ-1 and HAZ-2) in the welded joint were all obtained. The characteristic microstructures, carbides, and fracture surfaces were observed by optical microscopy (OM), scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The results revealed a different fracture toughness of each region in the DMWJ. The BM-1 showed a brittle fracture mode, mainly related to the directional needle-shaped carbide M3C. However, HAZ-1, BL, WM, HAZ-2, and BM-2 illustrated ductile fracture mode. The tempered microstructure and dispersed carbides increased the toughness of each material. Except for BM-1, the ductile fracture toughnesses of BL and WM were low in DMWJ due to coarse spherical carbide M7C3. The fracture toughness in the middle of HAZs was higher than that of the corresponding BMs owing to the fine tempered martensite and bainite. The fracture toughness along DMWJ appeared uneven. In sum, these findings look promising for the accurate integrity evaluation of DMWJs.

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Park, Sang Dae, Mitsugu Todo e Kazuo Arakawa. "Effect of Annealing on Fracture Mechanism of Biodegradable Poly(lactic acid)". Key Engineering Materials 261-263 (aprile 2004): 105–10. http://dx.doi.org/10.4028/www.scientific.net/kem.261-263.105.

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Effect of annealing on the fracture behavior of poly(lactic acid) (PLA) was investigated. Fracture toughness of PLA samples prepared under different annealing conditions was measured under static and dynamic loadings. Microstructure and crack growth behavior were characterized by polarizing microscopy (POM). Crystallinity was determined by DSC analysis. Fracture surface morphology was also studied by scanning electron microscopy. It was shown that the static fracture toughness increased with increase of crystallinity, while the dynamic toughness increased as crystallinity increased. POM exhibited that craze formation played an important role in the fracture mechanism of amorphous samples. Macroscopic fracture toughness and microscopic crack growth mechanism were correlated on the basis of these experimental results, and effect of annealing on the toughness and mechanism were discussed.

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Mutoh, Y., N. Miyahara, K. Yamaishi e T. Oikawa. "High Temperature Fracture Toughness in Silicon Nitride and Sialon". Journal of Engineering Materials and Technology 115, n. 3 (1 luglio 1993): 268–72. http://dx.doi.org/10.1115/1.2904217.

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Fracture Toughness of HIP-sintered silicon nitride decreased with increasing temperature up to 1200°C. The brittle-to-ductile transition was observed in the temperature range from 1200°C to 1275°C: the fracture toughness rapidly increased in the transition region. Above the transition temperature, the fracture toughness decreased with increasing temperature. Fracture toughness of sialon increased with increasing temperature. Transition of fracture mechanism was observed in sialon around 1300°C. The differences of temperature dependence of fracture toughness between two materials are interpreted in terms of the effects of grain-boundary glass phase on fracture.

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Yin, Hong Feng, e Lin Lin Lu. "Effect of Processing Condition on the Microstructure and Mechanical Properties of Ti₃SiC₂/SiC Composites". Materials Science Forum 658 (luglio 2010): 352–55. http://dx.doi.org/10.4028/www.scientific.net/msf.658.352.

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Ti3SiC2/SiC composites were fabricated by reactive hot pressing method. Effect of processing condition on the microstructure and mechanical properties of the composites were investigated. The results showed that: (1) Hot-pressing temperature influenced the phase constituent of Ti3SiC2/SiC composites. The flexural strength and fracture toughness of composites increased with hot pressing temperature. (2) The flexural strength and fracture toughness of composites increased when the content of SiC was increased. When the SiC content was 30wt% the flexural strength and fracture toughness of Ti3SiC2/SiC composite were 371MPa and 6.9MPa•m1/2 respectively. However, when the content of SiC reached 50wt%, the flexural strength and fracture toughness of composites decreased due to high porosity in the composites. (3) The flexural strength and fracture toughness of composites increased with the particle size of SiC added in composites. (4) Ti3SiC2/SiC composites were non-brittle at room temperature.

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Wang, Xiao Xiang, Wei Qi Wang, Wei Qing Li, Feng Li Li e Yu Lan Yang. "The Effect of Heat Treatment System on Mechanical Properties of Titanium Alloy BTi-6554". Materials Science Forum 618-619 (aprile 2009): 177–80. http://dx.doi.org/10.4028/www.scientific.net/msf.618-619.177.

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The effects of solution and aging treatment on the mechanical properties of BTi-6554 alloy titanium were investigated. The results showed: As to βsolution and aging treatment, the increase of fracture toughness is quite conspicuous as the solution temperature was raised, but the change of strength and plasticity is not obvious; As to (α+β) solution and aging treatment, the decline of fracture toughness and plasticity is quite conspicuous as the solution temperature increased, but the strength increased. The strength of (α+β) solution and aging treatment is higher than that of βsolution and aging treatment, but the fracture toughness is relatively lower. As the aging temperature increased, the strength of the alloy gradually decreased, but the plasticity and fracture toughness gradually improved and the improvement of fracture toughness is quite conspicuous. A better combination of strength-toughness-ductibility could be obtained under the heat treatment as solution at 900~930 oC and aging treatment at 560~590 oC.

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Bisht, Neeraj, e Prakash Chandra Gope. "Effect of rice husk (treated/untreated) and rice husk ash on fracture toughness of epoxy bio-composite". Journal of the Mechanical Behavior of Materials 29, n. 1 (1 gennaio 2020): 177–85. http://dx.doi.org/10.1515/jmbm-2020-0018.

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Abstract Present work studies the effect of particle reinforcement on fracture toughness of bio-composites. The filler used has been taken as rice husk. Epoxy resin has been taken as matrix material. Composites with varying filler loading of 10, 20, 30 and 40 wt.% were fabricated. The fracture toughness was seen to be increasing with increase in filler loading. However beyond 20% there was a decrease in fracture toughness with increase in filler loading. The effect of fibre treatment on toughness was also observed. Rice husk fibres pre-treated with NaOH were used. It was observed that fracture toughness further improved due to treatment. The increase in fracture toughness was significant. Fracture toughness increased from 1.072 to 2.7465 MPa√mm for 20% reinforcement and after treatment it increased to 2.876 MPa√mm. It was observed that concentration of treatment media also affects the fracture toughness. Further the effect of hybridization was observed by addition of rice husk ash as a secondary reinforcement. The fracture toughness of the resulting composites was remarkably higher than that of pure epoxy.

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Tesi sul tema "INCREASED TOUGHNESS"

Shea, Thomas Michael. "Localized Expansion of Pedicle Screws for Increased Stability and Safety in the Osteoporotic Spine". Scholar Commons, 2014. https://scholarcommons.usf.edu/etd/5308.

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When a patient is diagnosed with various spinal injuries, deformities, or advanced degeneration, it is commonly suggested that he/she undergoes surgery for spinal fusion. Most current procedures in spinal fusion restrict mobility in one or multiple levels of the spine so that, over time, new bone will grow between the levels creating a single motionless unit of bone. The bilateral pedicle screw system (BPSS) has long been considered to be the "gold standard" in spinal fusion. However, for patients with osteoporosis, adequate fixation within the bone-screw interface has continuously been difficult to achieve or has come with high risk of other forms of catastrophic damage. Reflecting this, a new pedicle screw design was developed and evaluated against current standard pedicle screws commonly used in spinal surgery. All screw designs were also tested with a common cement augmentation technique surrounding the circumference of the screw. All tests measured pullout strength, stiffness, energy to failure, toughness, and the amount of destruction to the surrounding synthetic bone. While the newly designed pedicle screw failed to produce significantly stronger pullout forces in comparison to the standard screws, it did show evidence of a longer lasting residual axial resistance and a safer mode of failure than the standard screw, hinting that the design may benefit individuals who experience screw pullout and are awaiting reinstrumentation.

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Mohr, Thomas Campion. "A study of the microstructural basis for the strength and toughness properties of water-quenched and air-cooled HSLA-100, HSLA-100 with increased copper, and a ULCB steel". Thesis, Monterey, California. Naval Postgraduate School, 1991. http://hdl.handle.net/10945/26797.

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PRASAD, SHRITI. "CORE SHELL POLY (DIMETHYLSILOXANA)--VINYL ESTER MICROSPHERE AS IMPACT MODIFIER FOR VINYL ESTER THERMOSETS". Thesis, 2015. http://dspace.dtu.ac.in:8080/jspui/handle/repository/15581.

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We report a two-step method for preparation of core shell elastomeric microspheres (CSR) using suspension polymerisation process and demonstrate its potential which proves it as an effective impact modifier for thermosetting vinyl ester resin. The first step involves suspension addition curing of siloxane macromonomer with platinum based hydrosilylation catalyst. The result of reaction parameters on the particle size distribution was decided and the elastomeric microspheres were eventually coated to prepare core-shell (PDMS-vinyl ester) microspheres. Vinyl ester composites were prepared by varying the amounts of microspheres (1-7 % w/w) and consequences of coating on the mechanical properties, that is quasi-static as well as dynamic properties were evaluated. The mechanical properties were found to improve at low loadings (≤ 3 % w/w), and the presence of an vinyl ester coating on the PDMS in the CSR led to improved dispersion, which was evident from its improved mechanical properties. The izod impact strength increased by 132 % on introduction of core shell PDMS – vinyl ester (3% w/w). Morphological studies revealed that the roughness of the fractured surface increased due to introduction of microspheres. In contrast to the PDMS containing composites, where the microspheres were removed entirely due to impact loading, the fractured surface of CSR containing composites revealed the presence of broken microspheres, which is a direct evidence of improved adhesion between elastomeric phase and the vinyl ester matrix.

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Libri sul tema "INCREASED TOUGHNESS"

Mohr, Thomas Campion. A study of the microstructural basis for the strength and toughness properties of water-quenched and air-cooled HSLA-100, HSLA-100 with increased copper, and a ULCB steel. Monterey, Calif: Naval Postgraduate School, 1991.

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Günther, Hans-Peter, a cura di. Use and Application of High-Performance Steels for Steel Structures. Zurich, Switzerland: International Association for Bridge and Structural Engineering (IABSE), 2005. http://dx.doi.org/10.2749/sed008.

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New steel production processes have led to a remarkable improvement in steel products within the last few years, and now allows steels to be produced according to the desired mechanical and chemical properties. High-Performance Steel (HPS) is the designation given to this new generation of steels that offer higher performance not only in terms of strength but also toughness, weldability, cold formability and corrosion resistance, compared to the traditionally used mild steel grades. The development of HPS goes with today's increased demand for slender lightweight structures, as for example in bridge design and the design of high-rise buildings, where there is a strong requirement to use high-strength materials in combination with good execution and fabrication properties. However, on the structural engineering side there is a need for knowledge on these new steel grades, and quite often design codes do not provide sufficient information to fully exploit the advantageous properties of HPS. The present volume provides an overview of the development and application of HPS on an international level. This is done by giving information on, for example, the production process, the chemical and mechanical properties, the relevant design and fabrication standards and on recent research results. Approximately fifteen included examples of realised applications aim to provide detailed information based on existing technical solutions, and to point out the major benefits when using HPS in comparison to mild steels. The document is thus not a monograph but an assembly of contributions from different countries. lt is separated into chapters related to different countries, namely the USA, Canada, Japan and Europe, all of them providing a state-of-the-art report on HPS.

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Sterling, Sam. Self Discipline: Increase Productivity and Mental Toughness. Independently Published, 2019.

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Bowen, David. Mental Toughness Training: How to Increase Your Mental Toughness and Set New Standards of Performance. Independently Published, 2022.

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Bowen, David. Mental Toughness Training: How to Increase Your Mental Toughness and Set New Standards of Performance. Independently Published, 2022.

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Selk, Jason. Executive toughness: The mental-training program to increase your leadership performance. 2018.

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Mental Toughness Training for Teenage Athletes: Increase Confidence, Improve Performance & Get Your Grades Up. Palmer Sage Publishing, 2022.

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Bain, Sandy. Mental Toughness Training for Teenage Athletes: Increase Confidence, Improve Performance & Get Your Grades Up. Palmer Sage Publishing, 2022.

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Bain, Sandy. Mental Toughness Training for Teenage Athletes: Increase Confidence, Improve Performance & Get Your Grades Up. Palmer Sage Publishing, 2022.

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Self-Discipline : Mental Toughness Mindset: Increase Your Grit and Focus to Become a Highly Productive Person. CreateSpace Independent Publishing Platform, 2017.

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Capitoli di libri sul tema "INCREASED TOUGHNESS"

Green, Suzy, Clive Leach e Daniela Falecki. "Approaches to Positive Education". In The Palgrave Handbook of Positive Education, 21–48. Cham: Springer International Publishing, 2021. http://dx.doi.org/10.1007/978-3-030-64537-3_2.

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AbstractWith the ongoing growth and development of positive education globally, there is increased interest and uptake in schools. Yet while there is considerable activity, there is little strategic orientation, with schools utilising a multitude of approaches, often with no overarching framework. There has also been a lack of guidance and implementation recommendations by key bodies, and a dearth of literature identifying and reviewing common approaches to the implementation of positive education, resulting in information overload and lack of clarity that may undermine the application and practice of positive education. This chapter first argues for the strategic integration of approaches and the need for cross-disciplinary collaboration. Second, we overview some of the current approaches to positive education, with a particular focus on social and emotional learning, character education, growth mindset, resilience and mental toughness, and coaching. Third, we provide a case study to highlight how the successful integration of these approaches can be implemented. Finally, practical recommendations are provided to inform the strategic implementation of positive education.

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Kotoul, M., A. R. Boccaccini e I. Dlouhy. "Quantification of Toughness Increase Due to Metal Particles in Glass Matrix Composites". In Fracture Mechanics of Ceramics, 245–61. Boston, MA: Springer US, 2005. http://dx.doi.org/10.1007/978-0-387-28920-5_19.

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Brackmann, Lukas, Arne Röttger, Hoang-Giang Bui, Sahir Butt, Golnaz Hoormazdi, Abdiel Ramon Leon Bal, Sebastian Priebe et al. "Excavation Simulations and Cutting Tool Wear". In Interaction Modeling in Mechanized Tunneling, 93–164. Cham: Springer Nature Switzerland, 2023. http://dx.doi.org/10.1007/978-3-031-24066-9_3.

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AbstractThe mechanized tunnel construction is carried out by tunnel boring machines, in which the soil in front of the working face is removed, and the tunnel lining is carried out with shotcrete or the setting of segments and their back injection. Advancements in this field aim towards increase of the excavation efficiency and increase of the tool lifetime, especially in rock-dominated grounds. The latter is achieved by understanding the wear mechanisms abrasion and surface-fatigue, and by knowledge of the microstructure-property relation of the utilized materials. Improvements for tool concepts are derived, based on experiments and simulations. A key parameter towards efficient rock excavation is the shape of the cutting edge of the utilized disc cutters. Sharp cutting edges have proven to generate higher rock excavation rates compared to blunt ones. The compressive strength of the utilized steel has to be high, to inhibit plastic deformation and thereby to maintain sharp cutting edges. This requirement competes with the demand for toughness, which is necessary to avoid crack-growth in the case of cyclic loading. Solutions for this contradiction lie in specially designed multiphase microstructures, containing both hard particles and ductile microstructural constituents. Besides adapting the alloying concept, these required microstructures and the associated properties can be adjusted by specific heat-treatments.

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"Corrosion of Martensitic Stainless Steel Weldments". In Corrosion of Weldments, 115–24. ASM International, 2006. http://dx.doi.org/10.31399/asm.tb.cw.t51820115.

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Abstract Martensitic stainless steels are essentially iron-chromium-carbon alloys that possess a body-centered tetragonal crystal structure (martensitic) in the hardened condition. Martensitic stainless steels are similar to plain carbon or low-alloy steels that are austenitized, hardened by quenching, and then tempered for increased ductility and toughness. This chapter provides a basic understanding of grade designations, properties, corrosion resistance, and general welding considerations of martensitic stainless steels. It also discusses the causes for hydrogen-induced cracking in martensitic stainless steels and describes sulfide stress corrosion resistance of type 410 weldments.

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Sharma, Pradeep. "Opportunity of Non-Wood Forest Products in Biocomposites". In Biocomposites [Working Title]. IntechOpen, 2021. http://dx.doi.org/10.5772/intechopen.97825.

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In recent years industries are attempting to decrease their dependency on petroleum-based fuels and products due to increased environmental issues. The tremendous increase in production and use of plastics in every sector of life has led to huge plastic waste disposal problems and also an environmental threat. In order to prevail over the present scenario, the viable and cost-effective approaches are to prepare eco-friendly bio-composites based on non-wood forest products (NWFP), a part of forest wealth of the globe, especially natural fibres, agricultural wastes and extractives. Natural fibres and extractives have many advantages viz. low density, low cost, considerable toughness properties, nontoxicity, sustainability and biodegradability. NWFP based composites may be utilized to produce non-structural parts for diverse applications in various industries as high-performance materials with interesting properties for specific applications viz. furniture, thermal, acoustic insulations and automotive industries etc. In the present chapter, opportunities of extractives, cellulosic and lignocellulosic fibres from non-wood forest products in Bio-composites will be discussed.

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Chopik, William J. "Modeling Growth and Resilience Among Military Personnel". In Redesigning Research on Post-Traumatic Growth, 167–85. Oxford University Press, 2021. http://dx.doi.org/10.1093/med-psych/9780197507407.003.0010.

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The prospect that people can be resilient to—or even grow from—a stressful experience is an alluring possibility—especially so for soldiers and veterans. Some have proposed that deploying and military experiences provide soldiers with enduring mental resources and toughness that are protective for the rest of their lives. However, definitive evidence for growth and resilience among military personnel has proved elusive. Part of the unknowns about growth and resilience can be attributable to how people think about and model questions related to growth and resilience. In this chapter, the author provides two empirical examples—changes in depressive symptoms among veterans and changes in character strengths among deploying soldiers—to illustrate how different conceptualizations, methods, and analyses can dramatically change the inferences we make about growth and resilience. The demonstrations provide an increased understanding about methodological flexibility in the study of growth and resilience and some expectations about how and why individuals might change in response to adversity.

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Li, Tianyu, Fangying Shi, Xiaoyan Liu, Xunhuan Lian, Jingying Zhang, Zheng Zhu, Yuhan Hu, Dezhi Wang e Tengfei Bao. "Evolution of Mechanical Property and Microstructure of Fibre-Reinforced Ultra High Strength Mortar with Desert Sand". In Advances in Transdisciplinary Engineering. IOS Press, 2022. http://dx.doi.org/10.3233/atde220375.

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Previous research showed that the concrete’s strength is obviously decreased when river sand was substituted by desert sand in abundance. In this paper, a new type of fibre-reinforced ultra high-strength desert sand mortar is studied. In the mix design of mortar, low W/B was used to save water. Also, fly ash and silica fume were adopted to partly replace cement, and desert sand was used to completely take the place of river sand. At the same time, steel fibre was used to improve the toughness. The pore structure changes of different desert sand ultra high strength mortar were studied by MIP. SEM and XRD were adopted to study the microstructure and hydration product changes. The results are as follows: the mortar’s mechanical properties are improved when the desert sand content rise. When desert sand was adopted to substitute river sand completely, the mortar’s compressive strength was increased by 36.91%, which reached 149.08 MPa. With the desert sand’s addition, the mortar’s porosity decreases and its pore structure is optimized. Desert sand played an active part in promoting the hydration of mortar, increasing hydration products, densifying the mortar structure and improving the mortar’s mechanical properties..The research in this paper solves the problem that the high-content desert sand mortar’s mechanical properties cannot meet the demand, and provides the actual application of desert sand in mortar a theoretical basis.

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Hong, Wang. "Finite Element Analysis of Fiber Pull-Out of Ceramic Matrix Composites". In Safety and Risk Assessment of Civil Aircraft during Operation. IntechOpen, 2020. http://dx.doi.org/10.5772/intechopen.93082.

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Ceramic matrix composites (CMCs) are widely used in aerospace, defense industry, and other fields because of their high strength, high toughness, and high temperature resistance. The interface phase with matching performance and structural coordination is the key element to improve the brittleness of CMCs and improve their strength and toughness. In this chapter, based on the fiber pull-out experiment, using the cohesive zone model as the interface element model, a two-dimensional axisymmetric fiber pull-out finite element model was established and simulated. The results show that within a certain range, higher interface bonding strength and interface fracture energy increase the maximum debonding load during fiber pull-out and enhance the material bearing capacity.

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Crepeau, Richard C. "The NFL Comes of Age". In NFL Football, 33–52. University of Illinois Press, 2020. http://dx.doi.org/10.5622/illinois/9780252043581.003.0003.

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The fifteen years following World War II were a period of prosperity and technological innovation on a scale that transformed American society and produced a consumer driven economy. The NFL rode this wave of change to unprecedented heights. As the war came to an end Arch Ward, Paul Brown and others founded the All-America Football Conference taking professional football to the West Coast and opening a battle with the National Football League. Brown’s success in Cleveland led Dan Reeves to move the Rams to Los Angles, and that move led to the desegregation of the NFL. Player salaries increased and the league became more competitive. The merger of the two leagues with the Browns, Colts, and Forty-Niners joining the NFL came in 1950. The professionalization of all facets of the game both on and off the field was led by Paul Brown, who transformed coaching techniques and dominated the AAFC and the NFL with such players as Otto Graham and Dante Lavelli, and by virtue of the desegregation of his team as he signed Marion Motley and Bill Willis. The New NFL caught the eye of the public and under the leadership of Bert Bell used, and then dominated, television to became a major force in American sport. The rise of television and the rise of the NFL went hand-in-hand and reached a crescendo when the large television audience watched the NFL Championship Game of 1958 go into “sudden death” overtime. The NFL’s growth also coincided with the start of Sports Illustrated and the magazine bet its future by focusing its coverage on the NFL. The other element of success was the NFL’s emphasis on a macho philosophy and the violence of the game. Players like Sam Huff and Bobby Lane were lauded in the media for their toughness and their off-field lifestyles.

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Gaona-Tiburcio, Citlalli, Alejandro Lira-Martínez, Marianggy Gomez-Avila, Jesús M. Jaquez-Muñoz, Miguel Angel Baltazar-Zamora, Laura Landa-Ruiz, Demetrio Nieves-Mendoza, Francisco Estupiñan-López e Facundo Almeraya-Calderón. "Delamination and Tensile Effect of Fine z-Binder Reinforced on Fiberglass/Polyester Composite for Aerospace Applications". In Next Generation Fiber-Reinforced Composites - New Insights [Working Title]. IntechOpen, 2022. http://dx.doi.org/10.5772/intechopen.106927.

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Delamination propagation in laminated composite materials is a common issue that always concerns us when we consider composites for structural purpose. Many possible solutions have been studied; the most famous is the three-dimensional (3D) woven composites materials, which have promising interlaminar fracture resistance but at the cost of increasing density, which for aerospace industry is very important. In this chapter, mode 1 double cantilever beam (DCB) interlaminar fracture toughness tests according to the American Society for Testing and Materials (ASTM) D5528 standard were performed on composite specimens made of E-Glass Saertex 830 g/m2 Biaxial (+/−45°) with Sypol 8086 CCP polyester resin with orthogonal z-axis oriented yarn woven of 0.22 mm diameter nylon monofilament. Four specimens were made with a longitudinal distance between the warp binders of 0.5, 1, 1.5, and 2 cm, respectively. A tensile test according to the ASTM D3039 standard was performed to study how z-binder may affect tensile resistance. The results show a considerable increase in interlaminar fracture toughness, several stress concentrators have been created because of the new yarn and premature failure in the matrix.

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Atti di convegni sul tema "INCREASED TOUGHNESS"

Kobrin, P. H., e A. B. Harker. "Compressive Thin Films For Increased Fracture Toughness". In 30th Annual Technical Symposium, a cura di Robert W. Schwartz. SPIE, 1986. http://dx.doi.org/10.1117/12.936429.

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Reed, R. P. "Low-Viscosity, Radiation-Resistant Resin System with Increased Toughness". In ADVANCES IN CRYOGENIC ENGINEERING: Transactions of the International Cryogenic Materials Conference - ICMC. AIP, 2004. http://dx.doi.org/10.1063/1.1774571.

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Alian, Helmy, Nukman, M. Badaruddin, Agung Mataram e Arief Mulya. "Increased toughness and low cycle fatigue in ASSAB 709 m steel through normalizing process". In TOWARD ADAPTIVE RESEARCH AND TECHNOLOGY DEVELOPMENT FOR FUTURE LIFE. AIP Publishing, 2023. http://dx.doi.org/10.1063/5.0130326.

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Baji, Avinash, Shing-Chung Wong, Todd Blackledge, Darrell Reneker e Sureeporn Tripatanasuwan. "Mechanical Behavior and Toughness of Electrospun Polycaprolactone Nanofibers". In ASME 2007 International Mechanical Engineering Congress and Exposition. ASMEDC, 2007. http://dx.doi.org/10.1115/imece2007-41248.

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This study examines the toughness and mechanical properties of biodegradable poly(ε-caprolactone) (PCL) with varying hydroxyapatite (HAP) content (0 – 30 wt%). Fracture toughness of HAP-filled PCL was also examined for the electrospun fibers using the essential work of fracture (EWF) concept. The electrospun fibers exhibited a diameter ranging from 200–500 nm and a combination of HAP particle sizes ranging from (50–100 nm) under the SEM. The tensile stress-strain behavior and fracture toughness of electrospun nanofibers were assessed using a nanoforce tensile tester. The electrospun system showed a substantial increase in plane-stress essential work of fracture in comparison to bulk specimens processed from pellets. Toughness decreased as HAP loading increased. The effect of simulated body fluid (SBF) on the mechanical properties was also studied. Mechanical properties including tensile strength and modulus were found to increase with HAP concentration in general. Compression molded electrospun nanofibers were spatially confined such that the tensile strength and stiffness of molded and spun fibers are remarkably higher than those from molded specimen of pellets.

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Mandell, John, Daniel Samborsky, Mei Li, Ricardo Orozco e Douglas Cairns. "Selection of fiberglass matrix resins for increased toughness and environmental resistance in wind turbine blades". In 2000 ASME Wind Energy Symposium. Reston, Virigina: American Institute of Aeronautics and Astronautics, 2000. http://dx.doi.org/10.2514/6.2000-57.

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McLaughlin, Adam, Je Kyun Lee, Sangyup Song e Byungki Kim. "Carbon Fiber Reinforced Graphene Nanocomposite to Enhance Fracture Toughness for Cryogenic Application". In ASME 2012 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2012. http://dx.doi.org/10.1115/imece2012-89566.

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This paper presents the fracture toughness, KIC, of a carbon fiber composite reinforced with the nanoparticle known as exfoliated graphite or graphene at room temperature and at cryogenic temperature. The measured KIC increased as mass fraction of graphene increase at room temperature and at cryogenic temperature for the composite with mass fraction of graphene of 0, 0.01, 0.1, 0.7, and 0.8.

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Bezensek, Bostjan, e John W. Hancock. "Increased Temperature Margins Due to Constraint Loss". In ASME 2003 Pressure Vessels and Piping Conference. ASMEDC, 2003. http://dx.doi.org/10.1115/pvp2003-2007.

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Enhanced levels of toughness associated with constraint loss are related to temperature shifts in the ductile-brittle transition curve. An argument to quantify the temperature shift is developed using self-similarity of near-tip stress fields under small-scale yielding combined with scaling techniques developed by Dodds and co-workers [1,2] for cleavage. The change in the yield stress and hence temperature that give the same stress field at failure in constrained and unconstrained fields has been determined. The procedure is illustrated using the data of Sherry et al [3] for A533B pressure vessel steel. The results are consistent with the empirical expressions proposed by Wallin [4], and enable a discussion of the physical implications for the micro-mechanics of cleavage.

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Zhang, Xiaoli, Yaorong Feng, Yinglai Liu e Chuanjing Zhuang. "The Toughness Index of X80 Mother Linepipe Steel and Its Optimum Microstructure". In ASME 2008 Pressure Vessels and Piping Conference. ASMEDC, 2008. http://dx.doi.org/10.1115/pvp2008-61062.

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Large amount of experimental data indicated, that the index of CVN toughness and shearing area of mother pipe of X80 are (200J, 90%). And the results showed that when charpy toughness was closing to 200J, the shearing area would reach to 90%; when the charpy toughness increased continuously, the shearing area would not increase further more. So the selection of charpy toughness value as 200J for pipeline steels is reasonable, and also its corresponding shearing area. To gain thus component index, the optimum microstructure of X80 steel should be strip-like ferrite mastered, small amount of granular bainite contained-acicular ferrite type steel, and, in which the size of MA island should be less than 1μm. This kinds of optimum microstructure of X80 pipeline steel will exert its softening role in improving toughness and simultaneity not decrease its strength.

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Gibson, Ronald F., e Hui Zhao. "Improvement of Vibration Damping Capacity and Fracture Toughness in Composite Laminates by the Use of Polymeric Interleaves". In ASME 1999 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 1999. http://dx.doi.org/10.1115/imece1999-0213.

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Abstract It is shown that simultaneous improvement of vibration damping capacity and interlaminar fracture toughness in composite laminates can be achieved by using polymeric interleaves between the composite laminae. The specific case of Mode II interlaminar fracture toughness and flexural damping capacity of interleaved composite laminates is studied. Graphite/epoxy, E-glass/epoxy and E-glass/polyetherimide composite laminates with polymeric interleaves of several different thicknesses and materials were tested using both the end notch flexure (ENF) test for Mode II fracture toughness and the impulse-frequency response test for flexural damping capacity. The Mode II energy release rate GIIc for all three composites increased linearly with increasing interleaf thickness up to a critical thickness, then dropped off with further increases in thickness. The damping loss factor η for all three composites increased linearly with increasing interleaf thickness up to the maximum thickness. Analytical models for predicting the influence of interleaves on GIIc and η are developed, along with a hypothesis for the critical thickness effect with regard to fracture toughness.

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Park, Dong-Yeob, Jean-Philippe Gravel e Da-Ming Duan. "Effects of Notch Acuity on Fracture Toughness Measurements". In ASME 2017 Pressure Vessels and Piping Conference. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/pvp2017-65177.

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Effects of initial crack-tip acuity on toughness measurements has been evaluated through extensive small-scale toughness testing — single-edge notched tension and bend (SE(T) and SE(B)) — at room temperature using two X70 pipeline steels and girth welds. In order to investigate effects of different crack tip radii on toughness, some specimens were notched to the target initial crack size using electrical discharge machining (EDM), and no further fatigue precracking was made. On the other hand, other specimens were EDM-notched and then fatigue-precracked to the target crack size according to the current practice of ASTM E1820. The results show that effects of crack tip acuity on toughness measurement are significant especially at the crack-tip blunting stage. The EDM precrack increased toughness measurements by a factor of up to 1.6 and 2 for SE(B) and SE(T), respectively, at 0.2 mm of crack extension, compared to the fatigue precrack.

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Rapporti di organizzazioni sul tema "INCREASED TOUGHNESS"

Leis. L51845 Database of Mechanical and Toughness Properties of Pipe. Chantilly, Virginia: Pipeline Research Council International, Inc. (PRCI), dicembre 2000. http://dx.doi.org/10.55274/r0010150.

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�The lower-strength grades of steel used for transmission pipelines into the 60s were much like those used in other steel construction in that era. These steels gained strength by traditional hardening mechanisms through chemistry changes, largely involving carbon and manganese additions. Improvement of these grades, primarily through control of ingot chemistry and steel processing, became necessary when running brittle fracture was identified as a failure mechanism in gas-transmission pipelines in the late 50s. Eventually, this avenue to increasing strength was exhausted for pipeline applications because this approach causes increased susceptibility to hydrogen-related cracking mechanisms as strength increases. For this reason, modern steels differ significantly from their predecessors in several ways, with the transition from traditional C-Mn ferrite-pearlite steels beginning in the mid 60s with the introduction of high-strength-low-alloy (HSLA) steels. This report presents the results of projects, PR-3-9606 and PR-3-9737, both of which were planned as multi-year projects. The first of these projects initially was conceived to provide broad evaluation of the fitness-for-service of wrinkle bends while the second was conceived to generate mechanical and fracture properties data for use in the integrity analysis of both the pipe body and weld seams in modern gas-transmission pipeline systems. As possible duplication between a joint industry project and the PRCI project became apparent, this project was scaled back to focus on properties of steels used in construction involving wrinkle bends. Consideration also was given to a more modern steel such as might be found in ripple bends, which are formed in bending machines that now have become widely used. The second project likewise was reduced in scope, with a focus on only the pipe body. Because both projects ended being centered on mechanical and fracture properties, both are presented in this combination report.

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Shen, Gianetto e Tyson. L52342 Development of Procedure for Low-Constraint Toughness Testing Using a Single-Specimen Technique. Chantilly, Virginia: Pipeline Research Council International, Inc. (PRCI), dicembre 2011. http://dx.doi.org/10.55274/r0010687.

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Pipelines from remote frontier regions are increasingly required to have adequate resistance to large deformations such as that caused by ground movement. In response to this, �strain-based design"� has been developed to enable assessment of imperfections at applied strains beyond yield. In addition, it is proposed to take advantage of the increased apparent toughness of pipe under low constraint, such as girth weld imperfections under axial tension, compared with the high-constraint toughness measured in conventional tests such as ASTM E1290 [1]. Application of low-constraint testing has been dvantageously applied in assessment of toughness for offshore pipeline projects. Also in the pipeline industry, demands on new pipeline projects include low design temperatures as well as high strain capacity. At the same time, increased strength is specified, which increases the level of required toughness. These factors make it increasingly important to assure weldment toughness, in particular to ensure that the failure mode remains ductile. It is well known that brittle cleavage is especially sensitive to constraint, and the availability of a toughness test that would reproduce field conditions would enable more rational development and acceptance of candidate welds and, in particular, enable more appropriate testing of weld heat-affected zones. This work was performed for specific application to surface circumferential cracks in pipe under strain-based design, for which the best constraint matching has been found to occur for clamped single-edge tension (SE(T)) specimens with H/W=10. For this geometry, a test procedure similar to that of ASTM E1820-06 for single-edge bend (SE(B)) and compact tension (C(T)) specimens was developed for J-resistance tests using a single-specimen technique. All the equations used in the procedure, including those for evaluation of J-integrals from the area under load/plastic crack mouth opening displacement (CMOD) curves, and evaluation of crack length from unloading compliance including rotation correction, were developed using finite element analysis (FEA) with a range of crack depths, focusing on a/W= 0.2 to 0.5 which is of most practical interest. The present procedure is compared with that of E1820 for SE(B) testing regarding evaluation of J-integral with crack growth correction, crack length evaluation, and correction of compliance for rotation.

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Malik. L51877 Crack Arrest Toughness to Avoid Dynamic Ductile Fracture in Gas Transmission Pipelines. Chantilly, Virginia: Pipeline Research Council International, Inc. (PRCI), marzo 2001. http://dx.doi.org/10.55274/r0010192.

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Design against long ductile fracture propagation in gas pipelines involves an analysis of the balance between driving force, derived from the gas pressure, and the fracture resistance of the material. Initially, the shelf energy in the Charpy test was successfully used as a measure of fracture propagation resistance. As material strength, pipe diameter and operating pressures increased and required greater fracture propagation resistance, the limitations of the Charpy energy approach became increasingly apparent. This limitation for modern steels is due to the fact that the Charpy test involves significant energy absorption contributions from processes not related to fracture propagation. If an energy-balance approach is to be maintained, and if material resistance is to be measured in a fairly simple laboratory notch bend test (e.g. Charpy or drop-weight tear), the problem reduces to the isolation of the propagation energy absorption per unit of crack advance. To resolve crack propagation energy, a novel modification was evaluated for both Charpy and DWTT specimens by employing a back-slot including a snug fitting shim to replace the removed material. In most cases, this modification was effective in curtailing the load-displacement trace when the propagating crack interacted with the slot on the backside of the specimen. It is also noted that this approach did not affect the initial portion of the load-displacement history and thus allowed crack propagation energies to be resolved.

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Leis, B. N., e N. D. Ghadiali. L51720 Pipe Axial Flaw Failure Criteria - PAFFC Version 1.0 Users Manual and Software. Chantilly, Virginia: Pipeline Research Council International, Inc. (PRCI), maggio 1994. http://dx.doi.org/10.55274/r0011357.

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In the early 1970's, the Pipeline Research Council International, Inc.(PRCI) developed a failure criterion for pipes that had a predominately empirical basis. This criterion was based on flaw sixes that existed prior to pressurization and did not address possible growth due to the pressure in service or in a hydrostatic test or during the hold time at pressure in a hydrotest. So long as that criterion was used within the scope of the underlying database and empirical calibration, the results of its predictions were reasonably accurate. However, with the advent of newer steels and the related increased toughness that supported significant stable flaw growth, it became evident that this criterion should be updated. This updating led to the PRCI ductile flaw growth model (DFGM) that specifically accounted for the stable growth observed at flaws controlled by the steel's toughness and a limit-states analysis that addressed plastic-collapse at the flaw. This capability provided an accurate basis to assess flaw criticality in pipelines and also the means to develop hydrotest plans on a pipeline specific basis. Unfortunately, this enhanced capability came at the expense of increased complexity that made this new capability difficult to use on a day-today basis. To counter this complexity, this capability has been recast in the form of a PC computer program. Benefit: This topical report contains the computer program and technical manual for a failure criterion that will predict the behavior of an axially oriented, partially through the wall flaw in a pipeline. The model has been given the acronym PAFFC which stands for Pipe Axial Flaw Failure Criteria. PAFFC is an extension of a previously developed ductile flaw growth model, L51543, and can account for both a flaw's time dependent growth under pressure as well as its unstable growth leading to failure. As part of the output, the user is presented with a graphical depiction of the flaw sizes in terms of combinations of flaw length and depth, that will fail (or survive) a given operating or test pressure. As compared to existing criteria, this model provides a more accurate prediction of flaw behavior for a broad range of pipeline conditions.

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Wang, Yong-Yi, Zhili Feng, Wentao Cheng e Sudarsanam Suresh Babu. L51939 Weldability of High-Strength Enhanced Hardenability Steels. Chantilly, Virginia: Pipeline Research Council International, Inc. (PRCI), settembre 2003. http://dx.doi.org/10.55274/r0010384.

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Since the 1970s, the development of high-strength pipeline steels has followed the route of progressively reduced harden ability through lower carbon and alloying element contents. Micro-alloying, controlled rolling (CR), and thermo-mechanical controlled processing (TMCP) have been used extensively to achieve the high-strength and other material property requirements despite the trend towards lower carbon content. The primary driving force behind the evolution of these alloying and processing strategies stems from the concerns over the weld ability, particularly the hydrogen induced cracking (HIC), at ever-increasing strength levels. Accompanying the extensive reliance on micro-alloying, CR, and TMCP, there has been a movement to tighter restrictions on micro-alloy variability, the increased use of heavy reduction at low inter-critical temperatures and, in some instances, the reliance on cold expansion. The objective of this project was to evaluate alternate steels with enhanced harden ability and identify those that would have a potential to (1) meet the high strength/high toughness requirement but without the adverse effects of the early trial heats of micro-alloyed TMCP X80 and X100 line pipe steels, and (2) exhibit sufficient resistance to hydrogen induced cracking (HIC) when welded with processes and consumables representative of state-of-the-art, low-hydrogen field girth welding practices. The focus of the project was on the weld ability and properties of the base metal and the heat-affected zone (HAZ). The selection and development of suitable weld consumables were not part of this project.

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Williams e Maxey. NR198709 Evaluation of a Heat-Treated X80 Grade Pipe. Chantilly, Virginia: Pipeline Research Council International, Inc. (PRCI), aprile 1987. http://dx.doi.org/10.55274/r0011140.

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Steel producers have developed in recent years a number of new types of line pipe to meet demand for high strength pipe with superior low temperature toughness and good field weldability. Obtaining independent evaluation of these new products is the objective, so that information on these pipes will be available when construction activities increase. Tests to determine the susceptibility of the pipe to hydrogen-induced stepwise cracking showed it to be susceptible; considerable cracking was observed after exposure to the NACE test solution. The pipe was not produced for use in the transport of sour gas, so a sulfide inclusion shape control addition had not been made. Presumably, resistance to hydrogen-induced stepwise cracking would have been significantly improved if such an addition had been made.

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Ragalwar, Ketan, William Heard, Brett Williams, Dhanendra Kumar e Ravi Ranade. On enhancing the mechanical behavior of ultra-high performance concrete through multi-scale fiber reinforcement. Engineer Research and Development Center (U.S.), settembre 2021. http://dx.doi.org/10.21079/11681/41940.

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Steel fibers are typically used in ultra-high performance concretes (UHPC) to impart flexural ductility and increase fracture toughness. However, the mechanical properties of the steel fibers are underutilized in UHPC, as evidenced by the fact that most of the steel fibers pull out of a UHPC matrix largely undamaged during tensile or flexural tests. This research aims to improve the bond between steel fibers and a UHPC matrix by using steel wool. The underlying mechanism for fiber-matrix bond improvement is the reinforcement of the matrix tunnel, surrounding the steel fibers, by steel wool. Single fiber pullout tests were performed to quantify the effect of steel wool content in UHPC on the fiber-matrix bond. Microscopic observations of pulled-out fibers were used to investigate the fiber-matrix interface. Compared to the control UHPC mixture with no steel wool, significant improvement in the flexural behavior was observed in the UHPC mixtures with steel wool. Thus, the addition of steel wool in steel fiber-reinforced UHPC provides multi-scale reinforcement that leads to significant improvement in fiber-matrix bond and mechanical properties of UHPC.

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Gill. L51675 Effects of Weldment Property Variations on the Behavior of Line Pipe. Chantilly, Virginia: Pipeline Research Council International, Inc. (PRCI), gennaio 1993. http://dx.doi.org/10.55274/r0010133.

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A steel weldment is a composite of zones or layers of different microstructures that possess different material properties. The zones include the base metal (or the sections of pipe), the weld metal, and a complex heat-affected zone (HAZ) of base metal that has been exposed to a variety of thermal cycles resulting in varying microstructures. The material properties of primary concern with respect to the mechanical behavior of the pipe are the stress-strain response (the constitutive properties) and the resistance to initiation and propagation of cracks or tears in the presence of a crack, notch, or other stress concentrator (the fracture toughness properties). Most of the experimental data on the behavior of welds with significant discontinuities were obtained from test specimens with surface or through-thickness notches or cracks. These data typically show an increase in load or nominal ductility for overmatched welds and a decrease in load or nominal ductility for undermatched welds. However, there are cases where the presence of a soft zone may enhance the nominal ductility and cases where overmatched welds will decrease the nominal ductility. The latter is especially likely in a girth weld with a circumferential crack in the HAZ.

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Patchett, B. M., e A. C. Bicknell. L51706 Higher-Strength SMAW Filler Metals. Chantilly, Virginia: Pipeline Research Council International, Inc. (PRCI), dicembre 1993. http://dx.doi.org/10.55274/r0010418.

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The welding of high strength steels in general, and for pipeline fabrication in particular, has shown that cracking due to hydrogen absorption during welding is more complex in these steels than in older, lower strength steels. In older steels, primary strengthening was accomplished with carbon, which caused hydrogen cracking in the base metal HAZ under reasonably predictable conditions involving microstructure, residual stress and hydrogen level. Pipeline steels were and are in the vanguard of change in strengthening philosophy. The change involves two areas of steel making, chemical composition and deformation processing. Pipeline steels now contain low carbon levels, in many cases less than 0.10%, and the resulting lack of strength is reclaimed by adding higher alloy levels to promote solution hardening (e.g. Mn), precipitation hardening (e.g. Cb, Cu) or transformation hardening (e.g. MO). In addition, alloy elements are added to improve toughness at high strength levels (e.g. Ni). At the same time, improvements have been made in reducing impurity and residual element levels, notably for S, P and O and N. Limitations on the effects of alloying additions on strength and toughness encouraged the use of deformation processing, primarily during rolling, to promote fine-grained microstructures to increase strength andtoughness simultaneously. Electrodes for the SMAW process have been developed for welding high-strength pipeline steels by using core wires made from high-strength microalloyed skelp extruded with cellulosic (Exx10) and low hydrogen (Exx16) flux coatings. The required alloy elements for high-strength deposits were therefore obtained from the core wire and not ferroalloy powders added to the flux, as is standard industrial practice. The idea behind this change was two fold: to avoid the possibility of introducing impurities from the varying sources of ferro alloy powders, including oxygen from the oxidized powder surfaces, and also to provide a closer match of the microalloy level to modern pipeline steel chemistries. The unknowns in this work were the effects of lower impurities/similar alloy content on the mechanical properties in the cast microstructure of a weld, compared to a pipe, and of the effect on electrode welding behaviour of a flux containing no ferro powders other than FeSi.

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L51634 Significance of Changes in Residual Stresses and Mechanical Properties due to SMAW Repair. Chantilly, Virginia: Pipeline Research Council International, Inc. (PRCI), ottobre 1990. http://dx.doi.org/10.55274/r0010104.

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There is a periodic requirement for immediate weld repairs during all pipe-laying operations. This need arises due to the occasional occurrence of girth weld flaws, which exceed specified defect tolerance levels. These defects are most commonly discovered by on-site radiographic inspection techniques and may be voids, inclusions and geometric irregularities. Repair welding may be required only over a limited portion of the pipe circumference and access for carrying out the repair may be restricted. Due to the range of types of repairs carried out and the limited time scales available, it is common for the weld repair procedures to be less well documented than the girth weld procedures. In particular, the welding procedure may not have been qualified with the same thoroughness and attention to detail as was the girth welding procedure.Weldments typically contain high residual stresses. The primary source of these residual stresses is the differential contraction, which occurs as a weldment cools. This contraction is restrained by the surrounding cooler material resulting in the weld metal being placed in tension with balancing areas of compression in the surrounding material. The input of additional thermal energy due to a repair in a highly restrained region may create a new residual stress pattern around the repair. Mechanical properties, especially toughness, may be adversely affected in the region near the repair. This program assessed the effects of SMAW repair welding on changes in surface residual stress distribution; fracture toughness and hardness around girth weld joints in line pipe. The following types of repair welds were studied: a part wall repair, a multiple part wall repair and full wall repair. The results were compared with a non-repaired weld sample. It was found that for the weld samples studied in this program, the full wall repair produced the most severe residual stress distribution followed by the multiple and single part wall repairs. The single repair only slightly increased the residual stress distribution when compared to the as-welded condition. Dramatic reductions in toughness were found in the multiple and full wall repairs due to coarse-grained regions produced during the repair operations. The single part wall repair exhibited an increase in toughness as a result of the addition of a cosmetic capping pass that resulted in greater grain refinement. This suggests that repair procedures utilizing a stringer or temper bead technique may reduce the effect of weld repairs on toughness.

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