Literatura científica selecionada sobre o tema "Plastic disintegration"
Crie uma referência precisa em APA, MLA, Chicago, Harvard, e outros estilos
Consulte a lista de atuais artigos, livros, teses, anais de congressos e outras fontes científicas relevantes para o tema "Plastic disintegration".
Ao lado de cada fonte na lista de referências, há um botão "Adicionar à bibliografia". Clique e geraremos automaticamente a citação bibliográfica do trabalho escolhido no estilo de citação de que você precisa: APA, MLA, Harvard, Chicago, Vancouver, etc.
Você também pode baixar o texto completo da publicação científica em formato .pdf e ler o resumo do trabalho online se estiver presente nos metadados.
Artigos de revistas sobre o assunto "Plastic disintegration"
1
Intaraksa, Parichat, Yositar Rudeekit, Pongsaks Siriyota e Thanawadee Leejarkpai. "Comparative Study of the Bio-Disintegration Behavior of Polylactic Acid under Laboratory and Pilot-Scale Composting Conditions". Advanced Materials Research 747 (agosto de 2013): 678–81. http://dx.doi.org/10.4028/www.scientific.net/amr.747.678.
Texto completo da fonteResumo:
In recent years, compostable plastics have gained a great attention as green materials due to the problems of more plastic waste generated each year over the world. One attractive of compostable plastics is that after use they can be biodegraded by natural microorganisms in the composting process within a specified period of time. Degree and rate of disintegration during composting is an important requirement that is used to determine the compostability of these plastics. This research work studied and compared the disintegration behaviors of PLA laboratory and pilot-scale composting conditions according to ISO 20200:2004 and ISO 16929:2002. Finally, the results from the disintegration testing could be used to evaluate the compostability, biological properties and impacted of a plastic material on the fermentation of organic waste in the composting plant.
2
Ferrero, Pablo. "Plastic waste to sustainable solutions: accelerating the biodegradation of syn-thetic plastics". Project Repository Journal 18, n.º 1 (23 de novembro de 2023): 60–62. http://dx.doi.org/10.54050/prj1820693.
Texto completo da fonteResumo:
Plastic waste to sustainable solutions: accelerating the biodegradation of syn-thetic plastics BioICEP combines chemical and biological methods to turn fossil-based plastic waste into natural, biodegradable substitutes for the packaging and pharma industries. It combines three technologies that enhance, accelerate and increase the degradation of plastics to levels far beyond what is currently possible. A triple-action depolymerization system breaks down plastic waste through chemical disintegration processes, biocatalytic digestion and microbial consortia.
3
Peng, Liang, Wenxue Du, Ganggang Bai, Lahuancairang, Shixiang Yuan, Juntao Li e Peng Feng. "Investigation of the Disintegration Characteristics of Neogene Mudstone at Different Burial Depths". Buildings 14, n.º 1 (15 de janeiro de 2024): 227. http://dx.doi.org/10.3390/buildings14010227.
Texto completo da fonteResumo:
The complex structure of Neogene mudstone plays an important role in geological disasters. A close relationship exists between the mechanisms of mudstone landslides and the disintegration characteristics of rocks. Therefore, understanding the disintegration characteristics of Neogene mudstone at different depths is crucial for enhancing engineering safety and assessing landslide stability. This study employed Neogene mudstone from different depths to perform disintegration and plastic limit experiments and revealed the sliding mechanisms of landslides involving Neogene mudstone, providing theoretical support for mitigating mudstone geological disasters. Our results demonstrate that Neogene mudstone from different depths experiences varied stress conditions and pore water pressure due to geological actions, significantly affecting the disintegration characteristics. By ignoring the factors of the slip surface, the slake durability index of mudstone decreases with increasing burial depth, while the plasticity limit index tends to rise. The influence of groundwater, geo-stress, and pore structure on Neogene mudstones at different depths results in overall weak stability and disintegration. Landslide occurrences are likely connected to the mechanical properties of mudstones at the slip surface, where a low slake durability index and higher plasticity index make the mudstones prone to fracturing, breaking, and disintegrating once in contact with water.
4
Zhu, Lei, Xin Jiang Song e Bao Ning Hong. "Analysis of Shallow Landslides Stability of Coal Measure Soil through Contact Elastic-Plastic FEM". Advanced Materials Research 243-249 (maio de 2011): 2076–83. http://dx.doi.org/10.4028/www.scientific.net/amr.243-249.2076.
Texto completo da fonteResumo:
In order to reveal the mechanism of deformation, disintegration and failure of shallow landslides of coal measure soil, through contact elastic-plastic FEM with shear strength reduction, the paper analyzes shallow landslides stability, calculates shallow landslides safety factors, and reveals the mechanism of deformation, disintegration and failure of shallow landslide of coal measure soil. The results are shown as follows: during shallow landslides of coal measure soil, the displacement of sliding mass sliding along sliding surface, the plastic strain of sliding mass and sliding mass sliding state along sliding surface don’t change simultaneously; adopting contact elastic-plastic FEM algorithm may better reflect the actual state and sliding process of shallow landslides of coal measure soil. It can help faithfully reflect real situations of shallow landslides like deformation, disintegration and failure of shallow landslide of coal measure soil, and it may afford one method that can be used as a reference of the stability analysis, accurate evaluation and forecast of this type of landslide.
5
Vaverková, Magdalena, František Toman, Dana Adamcová e Jana Kotovicová. "Study of the Biodegrability of Degradable/Biodegradable Plastic Material in a Controlled Composting Environment". Ecological Chemistry and Engineering S 19, n.º 3 (1 de janeiro de 2012): 347–58. http://dx.doi.org/10.2478/v10216-011-0025-8.
Texto completo da fonteResumo:
Study of the Biodegrability of Degradable/Biodegradable Plastic Material in a Controlled Composting EnvironmentThe objective of this study was to determine the degrability/biodegradability of disposable plastic bags available on the market that are labeled as degradable/biodegradable and those certified as compost. The investigated materials were obtained from chain stores in the Czech Republic and Poland. Seven kinds of bags (commercially available) were used in this study. One of them was a disposable bag made of HDPE and mixed with totally degradable plastic additive (TDPA additive). Another was a disposable made of polyethylene with the addition of pro-oxidant additive (d2w additive). One was labeled as 100% degradable within various periods of time, from three months up to three years, and four were certified as compostable. The test was carried out in a controlled composting environment. The biodisintegration degree of the obtained pieces was evaluated following a modified version of ČSN EN 14806 Norm "Packaging - Preliminary evaluation of the disintegration of the packaging materials under simulated composting conditions in a laboratory scale test" and a modified version of ČSN EN ISO 20200 "Plastics - Determination of the degree of disintegration of plastic materials under simulated composting conditions in laboratory-scale test" (ISO 20200:2004). The emphasis was put on determination whether the bags are degradable/biodegradable or not.
6
Eich, Andreas, Miriam Weber e Christian Lott. "Disintegration half-life of biodegradable plastic films on different marine beach sediments". PeerJ 9 (10 de agosto de 2021): e11981. http://dx.doi.org/10.7717/peerj.11981.
Texto completo da fonteResumo:
The seafloor is considered the major sink for plastic debris in the world’s oceans. Biodegradable polymers are available on the market as a substitute for conventional plastic and could potentially end up in the same environment. To gain more insight into the effects of different sediments on the degradation rate of biodegradable plastic we performed two iterative seawater tank experiments. First, to test the effect of sediment grain size, film of Mater-Bi HF03V, a blend of thermoplastic starch and biodegradable polyesters, was placed on the surface of mud as well as on four different grain size fractions of beach sand. Disintegration half-life was shortest on mud (139 days) and increased with the grain size of the beach sediment fractions (63–250 µm: 296 days; 250–500 µm: 310 days; 500–1,000 µm: 438 days; >1,000 µm: 428 days). We assume that the higher surface-to-volume ratio in fine sediment compared to coarse sediment led to a higher bacterial abundance and thus to faster disintegration rates. In a follow-up experiment, the <500 µm fraction of sediment from four different beaches around Isola d’Elba, Italy, was used to test plastic disintegration as above. Additionally, polyhydroxybutyrate (PHB, MIREL P5001) was used as a positive control and high-density polyethylene (HD-PE) as a negative control. No disintegration was observed for HD-PE. Mater-Bi HF03V and PHB disintegrated significantly differently on sediment from different sites, with half-lives of Mater-Bi HF03V ranging from 72 to 368 days and of PHB from 112 to 215 days. Here, the half-life was shortest on slightly coarser sediment and at potentially anthropogenically impacted sites. We assume that the effect of the grain size on the disintegration rate was masked by other parameters influencing the microbial community and activity. Understanding the parameters driving biodegradation is key to reliably report the range of disintegration rates occurring under the various conditions in different ecosystems.
7
Chong, Zhi Kai, Alexander Hofmann, Marie Haye, Sharon Wilson, Ihsanullah Sohoo e Kerstin Kuchta. "Lab-scale and on-field industrial composting of biodegradable plastic blends for packaging". Open Research Europe 2 (23 de agosto de 2022): 101. http://dx.doi.org/10.12688/openreseurope.14893.1.
Texto completo da fonteResumo:
Background: The acceptance of compostable plastic packaging in industrial composting plants is not universal despite available certification for compostability due to the persistence of compostable plastic residues reported by some industrial plants. This study aims to better understand this discrepancy by comparing the disintegration rate of two compostable plastic blends designed for rigid packaging (polylactic acid based) and soft packaging (polybutylene succinate based) between a controlled lab-scale test and an on-field test in an industrial composting plant. Methods: The thermophilic lab-scale disintegration test was conducted according to ISO 20200 in triplicates for 4, 8 and 12 weeks while the on-field test was conducted by exposing duplicate test material in the compost pile of an industrial composting plant in northern Germany, for three weeks. The mass change of the remaining test material >2mm was used as an indicator of disintegration. Results: The rigid packaging blend (1 mm thickness) retained on average 76.4%, 59.0% and 55.7% of its mass after 4, 8 and 12 weeks respectively in the lab-scale test. After exposure to industrial composting on-field, the remaining mass was 97.2% and 99.5%. The soft packaging blend (109±9 µm sample thickness) retained on average 45.4%, 10.9% and 0.3% of its mass after 4, 8 and 12 weeks respectively and 94.0% and 93.8% after exposure to industrial composting on-field. Conclusions: The results show a substantial difference in disintegration rates between the lab-scale and the on-field test after three to four weeks. The difference between the tests that might contribute significantly to the differing disintegration rates is the composition of the composting substrate. Besides the design and characteristics of the packaging itself, the composting substrate and thermophilic composting duration of individual plants are important to determine the suitability of treating compostable plastic packaging in industrial composting plants as well as inform potential solutions.
8
Mikhailov, S. V., e S. N. Danilov. "Helical-chip disintegration in the turning of plastic materials". Russian Engineering Research 33, n.º 3 (março de 2013): 176–78. http://dx.doi.org/10.3103/s1068798x13030131.
Texto completo da fonte
9
Mukri, A. K., J. H. Tan, S. M. Tahir, M. S. Anuar e S. M. Yusoff. "Compaction behaviour of mannitol-cocoa powder mixtures and their resulting tablet strength and disintegration characteristics". Food Research 5, S1 (3 de janeiro de 2021): 182–87. http://dx.doi.org/10.26656/fr.2017.5(s1).038.
Texto completo da fonteResumo:
Cocoa powder is an important ingredient in the confectionery industry and, mannitol is an alternative sugar alcohol. In this work, mannitol powder was mixed with cocoa powder and compacted into tablet form via the uniaxial die compaction process. The frictional, compaction, tablet mechanical and disintegration properties were studied due to their importance in characterizing the behaviour of the tablets during processing and its final product characteristics at varying mannitol contents. The composition of mannitol in the mannitol-cocoa tablet varied at 95% w/w, 50% w/w and 5% w/w, while pure 100% w/w mannitol and cocoa tablets were set as controls. The compaction pressures used in making the tablets varied at 37.67 MPa, 75.34 MPa, 113.01 MPa, 150.68 MPa and 188.35 MPa. The compaction behaviour of the powder during the compaction process was evaluated using the plastic work and the maximum ejection stress values. The tablet strength was determined using the tensile strength method and tablet disintegration study was also conducted. The results showed that the increase in the compaction pressures increased the plastic work, maximum ejection pressure, tablet strength and also its disintegration time. The tablet formed having 95% w/w mannitol composition exhibited the highest plastic work value of 10.32±0.01 J, highest maximum ejection pressure value of 4.4±0.06 MPa, highest tensile strength value of 1.06±0.04 MPa and shortest disintegration time of 171±51 s amongst the three different mannitol compositions studied. Meanwhile, the effects of mannitol composition in the tablet on these observed responses were also dependent upon the compaction pressures used during tablet formation. In conclusion, the addition of mannitol improved the tablet strength and shorten the disintegration time in the experimental range employed in this study.
10
Tuong, Thi Nguyet Anh, Thi Thuy Le, Hoang Linh Doan, Tien Dat Nguyen, Ngoc Diep Nguyen, Xuan Quang Chu, Hung Thuan Tran e hao Yen Linh Dang. "Evaluation of the disintegrability of eco-friendly packaging under laboratory and pilot-scale composting conditions". Ministry of Science and Technology, Vietnam 65, n.º 10DB (25 de outubro de 2023): 67–72. http://dx.doi.org/10.31276/vjst.65(10db).67-72.
Texto completo da fonteResumo:
The growing production demand and promising applications of biodegradable plastic have spurred interest in assessing the biodegradability of this material. Disintegration is the first stage of the biodegradation process and therefore it affects the most important on the biodegradability of materials. This research focuses on evaluating and comparing the disintegration ability of eco-friendly packaging, which is being produced and commonly consumed in Vietnam, under industrial composting conditions at laboratory scale according to TCVN 12409:2020 standard and pilot scale according to TCVN 12408:2020 standard. The variations in temperature, humidity, pH, and visual appearance were monitored during the composting process. The results showed that the disintegration behaviours of eco-friendly packaging are similar at both scales. The disintegration rate of eco-friendly packaging at both testing scales reached over 90% after 84 days.
Teses / dissertações sobre o assunto "Plastic disintegration"
1
Wroe, Sarah. "The recycling of resorcinol formaldehyde latex coated nylon 66". Thesis, University of Manchester, 2013. https://www.research.manchester.ac.uk/portal/en/theses/the-recycling-of-resorcinol-formaldehyde-latex-coated-nylon-66(6b849427-03d1-4b81-b50a-df9d45f45e04).html.
Texto completo da fonteResumo:
The Waste (England and Wales) Regulations encourage business to recycle their waste, as an alternative to landfill. This study has evaluated a number of processing techniques with respect to a difficult to recycle, technical textile, in order to develop recycling opportunities. Resorcinol formaldehyde latex (RFL) coated nylon 66 is a high performance fabric used as an interface to reinforce rubber products such as timing belts. The characteristics of the RFL coated woven fabric, assessed in comparison to equivalent uncoated fabrics, showed increased stiffness and decreased tear resistance. This was followed by the evaluation of three reduction processes:1) The Laroche Cadette shredder;2) The Hollander beater;3) The Intimus disintegrator. The fibre length, coating integrity and degradation properties were assessed for each of the reduction techniques. The longest fibres were produced by the Laroche Cadette shredder, this method proved most suitable for textile processing. The coating was unaffected and little degradation occurred. The Hollander beater produced mid-length fibres; however, fibres as short as 2mm could also be achieved. The material did not degrade, as water used within the process reduced heat build up, the coating remained adhered to the fibre. The Intimus Disintegrator produced the smallest fibre length and produced the greatest processing problem due to heat build up and degradation. Particles in addition to fibres were formed but were not crystalline in nature, and were difficult to process further. Processing using paper, textile, plastic and rubber technology were trialled with varying success. The recommended recycling route was found to be through reduction using the Hollander beater followed by incorporation of the waste as filler in rubber composites. RFL coated fibres gave additional strength to the rubber at high filler contents of 37.5% in comparison to uncoated waste filler also trialled. This was due to the surface chemistry of the RFL coated nylon fibre. The RFL coated nylon 66 filler also enabled the composites to exceed tear specifications required for hardwearing footwear. Fibres were effectively separated by length using forward flow and reverse flow hydrocyclones, separating 10mm and 3mm length fibres, which would prove useful for obtaining optimum particle size for reinforcement during the reduction process. Alternate processed trialled enabled the RFL fibres to be formed into a paper sheet using 50% cellulose pulp but textile processes proved unsuccessful. Moulded pieces formed though compression moulding were able to be produced from coated and uncoated fabric pieces, however many voids were present, limiting the usability.
2
Giordano, Jacin. "Disintegrating Loops of Uprooted Plastic". 2018. https://scholarworks.umass.edu/masters_theses_2/644.
Texto completo da fonteResumo:
I’m interested in paint’s malleability. In my work, I transform the physical possibilities of paint in a literal way, using it as a tactile material to be cut apart, reassembled, or simply exposed for what it is. My paintings are labor-intensive. They are not predetermined, they meticulously evolve; crafted rather than executed. Remnant material from one painting, the result of a working process of cutting, gouging, or sanding, leads directly to the production of a new piece. In my work there is no illusion, material is meant to reiterate itself. Unlike abstract painters of the early 20th century, who hoped their work could aspire to spiritual harmony. My paintings are much more pragmatic, every day, present, and real.
Livros sobre o assunto "Plastic disintegration"
1
Manuscript Paper for Writing Music 11 Staves 120 Pages,, Empty Old Brick Wall Texture Walls Disintegration See Red Brick Building Facade with Damaged Plaster Cover. Independently Published, 2021.
Encontre o texto completo da fonteCapítulos de livros sobre o assunto "Plastic disintegration"
1
Shri Kaushal, Gyan, e Rajiv Umrao. "Agroforestry". In Environmental Sciences. IntechOpen, 2023. http://dx.doi.org/10.5772/intechopen.106432.
Texto completo da fonteResumo:
Agroforestry has the double benefit of making grain and wood from bushes alongside crop advent from a solitary actual property parcel. It is beneficial to broaden teak, crease, sesame, and eucalyptus for wood, lumber for apparatuses, crease, bamboo and teak, bamboo for paper and mash, and karanj for biofuel. Manure bushes are for land recovery, soil wellbeing, and food security; herbal product bushes for sustenance and pay; feed bushes that in addition broaden smallholder domesticated animals’ advent; lumber and gasoline wooden bushes for secure residence and energy; healing bushes to war infection, especially in which there’s no drug store; and bushes that produce gums, tars, or plastic items. Ranchers having substantial land maintenance commonly take in this path of motion of tree planting. Significant tree species for block planting are poplar, eucalyptus, and deck. This vegetable offers a top-notch wellspring of high-protein dairy farm animal grain. The range is separated from the leaves, blossoms, bark, seeds, and so on from palas blossoms to orange, from one purple to any other, from one blue to any other, and so forth getting colors. If you are taking a gander on the historic backdrop of horticultural ranger carrier in India, we are those with the maximum profile of rehearsing rural ranger carrier. This assists with saving the dampness withinside the dust for pretty a while. So, we ought to make use of strategies like ranger carrier, and natural product cultivation. Raising animals at the homestead, cows, bison, goats, and hens bring fulfilment to the ranch. The agroforestry framework has the selection to study munching with the aid of using the reception of feed tree species with suitable grasses. Safeguarding systems and streets from floating snow, funding price range in domesticated animals’ advent with the aid of using lessening wind chills, safeguarding crops, giving untamed existence territory, disposing of climatic carbon dioxide and handing over oxygen, lowering breeze pace, and as a consequence proscribing breeze disintegration and particulate depend withinside the air, diminishing commotion contamination, and moderating heady fragrance from focused domesticated animals’ activities.
2
Kulu, Priit, e Dmitri Goljandin. "Retreatment of Polymer Wastes by Disintegrator Milling". In Current Topics in Recycling [Working Title]. IntechOpen, 2021. http://dx.doi.org/10.5772/intechopen.99715.
Texto completo da fonteResumo:
Global introduction of waste utilization techniques to the polymer market is currently not fully developed but has enormous potential. Before reintegration of used material into a new product, it normally requires grinding, that is shredding, crushing, or milling. In traditional grinders, the generated stresses in the material to be ground are equal to or less than the strength of the material. If by traditional methods, the stresses generated are compressive + shift, so by milling based on collision are tension + shift. Due to the high stress-material strength ratio at collision, it is possible to crush not only brittle materials but also ductile materials. This process allows easily combining the grinding of composite materials with their separation into individual constituents. In the current study, the mechanical recycling of the following groups of polymer materials was studied: pure brittle and soft polymers (PMMA, HDPE and IER), blends of plastics (ABS+PMMA, PC + ABS), reinforced plastics (PMMA+GFP); elastomers (rubber and tyres), and printed circuit boards (PCB).
3
Kumar, Dheeraj, Nadeem Faisal, Ramit Choudhury e Swarup S. Deshmukh. "Experimental Investigation of the Mechanical and Thermal Properties of Natural Green Fibres". In Optimum Composite Structures - Recent Advances, New Perspectives and Applications [Working Title]. IntechOpen, 2022. http://dx.doi.org/10.5772/intechopen.102453.
Texto completo da fonteResumo:
Biomaterials and green products rely heavily on natural lignocellulosic fibres. They have a wide variety of potential capabilities and characteristics, making them suitable for many applications. These fibres offer all the components required for renewable energy deployment. Fibre polymers from Jharkhand such as palm, datura, lemon, and mustard were studied for their thermal, mechanical, and interfacial adhesion properties. There were also tests on tensile strength, elongation to break, and thermogravimetric analyses (TGA). The effects of heating on weight loss, water loss, and disintegration have also been studied. A comparison was made between frequently used global fibres and the fibres analysed in this research article. Jharkhand’s fibres are shown to be more compromising than worldwide fibres. Palm fibres have excellent tensile strength (160 MPa) and modulus of elasticity (5 GPa). The thermal behaviour of lemon and datura fibres is the most similar. Palm and mustard fibres respond similarly in warm temperatures. At 140°C and 240°C, mass loss was 18.8 and 24.3%, respectively. TGA shows that the studied fibres are more suited for industrial applications owing to their stable thermal behaviour. Plastics, textiles, packaging, and papers may all use palm fibres in insulators, circuit boards, switches, and terminals, as well as in furniture and window frames.
4
Hough, Susan Elizabeth, e Roger G. Bilham. "The 1923 Kanto Earthquake: Surviving Doomsday". In After the Earth Quakes. Oxford University Press, 2005. http://dx.doi.org/10.1093/oso/9780195179132.003.0010.
Texto completo da fonteResumo:
Citizens of Yokohama and Tokyo were just sitting down to their Saturday noonday meal on the morning of September 1, 1923, when the great Kanto earthquake struck. The time, 11:58:44, was precisely documented by seismometers, which were by this time commonplace. In 1923, Tokyo was already a bustling urban center and port city, home to over 2 million people. Yokohama was an important port and industrial center as well, with a population of more than 400,000. As had been the case in Charleston, observers gave differing descriptions of the initial shaking; some witnesses described the same gradual onset that residents of Somerville, South Carolina, had experienced. In Yokohama, however, Otis Manchester Poole wrote that, in contrast to other temblors that allowed time for contemplative speculation (“How bad is this one going to be?”), . . . This time . . . there was never more than a few moment’s doubt; after the first seven seconds of subterranean thunder and creaking spasms, we shot right over the border line. The ground could scarcely be said to shake; it heaved, tossed and leapt under one. The walls bulged as if made of cardboard and the din became awful. . . . For perhaps half a minute the fabric of our surroundings held; then came disintegration. Slabs of plaster left the ceilings and fell about our ears, filling the air with a blinding, smothering fog of dust. Walls bulged, spread and sagged, pictures danced on their wires, flew out and crashed to splinters. Desks slid about, cabinets, safes and furniture toppled, spun a moment and fell on their sides. It felt as if the floor were rising and falling beneath one’s feet in billows knee high. . . . Poole could not gauge how much time elapsed during the tumult but cited an official record of four minutes. Although the earthquake damaged all of the seismographs operated by the seismological station at Tokyo University, Professor Akitsune Imamura and his staff were at work within minutes of the earthquake, analyzing the seismograms.
Trabalhos de conferências sobre o assunto "Plastic disintegration"
1
Marriott, Douglas L., Herbert E. Stumph, Arun Sreeranganathan e Christopher J. Matice. "Simplified Computation of Creep Damage Propagation". In ASME 2016 Pressure Vessels and Piping Conference. American Society of Mechanical Engineers, 2016. http://dx.doi.org/10.1115/pvp2016-63781.
Texto completo da fonteResumo:
The commonly accepted approach to dealing with material damage as the cause of structural failure is to treat the most highly distressed location in the structure as an equivalent simple test and to define failure of the structure as a whole as being failure at that point location. The exception to this rule is plastic deformation. Yielding at a point was recognized several decades ago as being an excessively conservative definition of component failure and it is now standard design practice to accept failure as being the limit load, which is only reached, sometimes after extensive propagation of a plastic zone. Other material failure mechanisms also occur after a finite period of damage propagation, but this additional strength, or life, is not usually taken into account, partly because the damage mechanisms themselves are not always well defined, and partly because of the computational difficulty involved in assessing the propagation of damage. Creep rupture falls into the category of a mechanism which can enjoy an extensive period of damage propagation before structural failure occurs, but the difficulty of evaluating it quantitatively has meant that it continues to be dealt with as essentially a point failure phenomenon. Relatively recently, many of the problems associated with assessing creep damage have been resolved, on the material side by increased use of so-called “continuum damage mechanics” based models such as Kachanov and Omega and, on the computational side, by the exponential growth in the capabilities of advanced Finite Element Analysis. It is now possible in principle to trace the entire life of a complex component, down to final disintegration. However, this capability still comes at a significant cost, and there is still room for simplification in order to bring this capability to a wider range of potential users. This paper describes a process for evaluating the propagation of creep damage, down to the point of total disintegration, using approximations which exist within the standard capabilities of a typical FE design package. This innovation does not do anything that cannot be done today using the full repertoire of computational tools that exist, notably user subroutines, but provides a simpler platform which can be used to push damage evaluation further into the activities of day-to-day design with a significant reduction in the resource allocation currently required to do the job. Results are compared with creep experiments on notched bars.
2
Bumanis, Girts, Jelizaveta Zorica, Ina Pundienė e Diana Bajare. "The workability kinetics of phosphogypsum binder". In The 13th international scientific conference “Modern Building Materials, Structures and Techniques”. Vilnius Gediminas Technical University, 2019. http://dx.doi.org/10.3846/mbmst.2019.103.
Texto completo da fonteResumo:
The dihydrate phosphogypsum (PG) based binder workability kinetics were investigated regarding to waterbinder ratio (W/B) and chemical admixtures added to the composition of PG paste. PG was dried at 60 °C and homogenized to powder like particles with collision milling in disintegrator and calcium sulphate hemihydrate was obtained by heating PG at 180 °C. The obtained binder chemical, mineralogical and technological properties were tested and compared to commercial gypsum plaster. Early age (2 h) and 14 d compression strength was determined. The workability and setting time of both – PG and commercial gypsum was investigated with viscosimeter, ultrasonic pulse velocity and Vicat apparatus and correlation between testing methods was obtained. Results indicate that binder based on PG has slightly lower pH (pH 6.3) than commercial binder (pH 6.8) and finer particle size grading leading to increased W/B ratio and more rapid initial setting time. The set retarder could efficiently increase the setting time of PG binder giving extra workability time which is positive factor for prolonged treatment of binder slurry, i.e. to prepare porous gypsum binder. Such approach would give a safer alternative to PG disposal, closing the materials loop and enhancing the circularity of this material.
3
Peng, S. Y., X. B. Li, G. Q. Chen e Y. Mitani. "Unloading Response of Tunnels in Deep Brittle Rock Mass Considering Ubiquitous Minor Joints". In 57th U.S. Rock Mechanics/Geomechanics Symposium. ARMA, 2023. http://dx.doi.org/10.56952/arma-2023-0360.
Texto completo da fonteResumo:
ABSTRACT Minor joints exist ubiquitously in deep-buried brittle rock masses subjected to high in-situ stress. These joints affect the strength and deformation properties and lead to the concentration and dissipation of stress wave propagation. Through modeling and verification, the rock mass model in the study with closable minor joints can perform the plasto-elastic behavior under static compression, and the increase of wave velocity with confining stress under dynamic load. The unloading response of tunnels is analyzed in two influencing factors: unloading rate and lateral stress coefficient. According to the results, the increase of unloading rate will intensify stress oscillation and increase additional dynamic stress disturbance of the joint rock mass near the tunnel boundary. As the vibration dissipates kinetic energy, the additional dynamic stress disturbance farther away from the tunnel boundary is decreased. Additionally, the minor joints can open or close in particular directions depending on the complex in-situ stress and the stress distribution of the surrounding rock mass. At the location along the direction of open joints and close to the stress release source, the joint rock mass may have a higher additional stress concentration than in the elastic model. INTRODUCTION The scarcity of shallow mineral resources and construction space has substantially escalated the depth of tunnel excavation (Li et al., 2017; Xie et al., 2015). Deep rock mass subjected to gravitational and tectonic stress reserves enormous strain energy and exhibits evident fracture development. Deep tunnel excavation is typically a dynamic unloading process (Cai, 2008; Lu et al., 2012). In particular, the strain energy will be immediately released within several milliseconds and induce a pulse load when the tunnel is excavated utilizing drilling and blasting (Yang et al., 2013). This process may lead to various observed hazard phenomena, such as spalling (Jiang et al., 2013), rock burst (Ortlepp & Stacey, 1994), large deformation (He et al., 2005), and zonal disintegration (Jia & Zhu, 2015). Meanwhile, the intensity and frequency of disasters escalate as excavation depth increases, threatening construction and operation safety (Cai, 2016). Therefore, the mechanism of unloading failure of deep tunnels in rock mass has always attracted the attention of many researchers.