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Articoli di riviste sul tema "Identification of mechanical wood properties"
1
Ruffinatto, Flavio, Gaetano Castro, Corrado Cremonini, Alan Crivellaro e Roberto Zanuttini. "A new atlas and macroscopic wood identification software package for Italian timber species". IAWA Journal 41, n. 4 (21 ottobre 2019): 393–411. http://dx.doi.org/10.1163/22941932-00002102.
Testo completoAbstract (sommario):
Abstract Wood identification has never been more important to serve the purpose of global forest protection, by controlling international illegal timber trade and enabling the enforcement of timber trade regulations. Macroscopic wood identification is the fastest method for the first identification of an unknown timber and, with proper training, it can be performed by operators in the timber industry, restorers and curators of cultural heritage, wood traders, designers, students and customs officers. Here we describe a wood atlas and accompanying software, SIR-Legno, developed for the identification of 48 Italian timber species based on a recently proposed list of macroscopic features for wood identification. For each species the atlas provides a complete macroscopic description plus information on natural durability, end-use class, physico-mechanical properties, conservation status, maximum diameter of the bole and most frequent uses. For each genus covered by the atlas, information about species number, CITES-listed species, main commercial timbers, similarly-named timbers from other genera, geographical distribution and notes on species or species group recognition at macroscopic and microscopic level are provided. SIR-Legno is an educational product, a handy identification key and a tool to search woods by their natural durability, end-use class and physico-mechanical properties. Both the atlas and the software can be freely downloaded from the web. Thanks to the adoption of a codified list of characters and a transferable design, SIR-Legno can be easily replicated or expanded to other databases in order to include new species. SIR-Legno is freeware and works on any version of Windows.
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Liu, Jiwei, Huifeng Yang, Yutao Zhou, Benkai Shi e Haotian Tao. "Parameter identification procedure for hysteretic shear-resistant properties of beech wood dowels". BioResources 19, n. 2 (22 aprile 2024): 3681–98. http://dx.doi.org/10.15376/biores.19.2.3681-3698.
Testo completoAbstract (sommario):
To evaluate the shear-resistant behavior of wooden dowels used in Blockhaus shear walls under cyclic load, 19 specimens under ten groups of conditions were prepared and tested. The failure modes, hysteresis curves, mechanical properties, stiffness degradations, and energy dissipation capacities of the specimens were studied. The test results showed that with the increase in the number of dowels, the initial stiffness and peak load of the specimens increased greatly. The diameter of the dowels had little influence on the mechanical properties of the specimens. Furthermore, the test findings demonstrated that the pretension load between the walls greatly enhanced the initial stiffness and energy dissipation capacity of specimens. A simplified finite element model was established in Opensees. Considering the effect of material variability, the parameters of single dowel shear spring and friction spring were identified by Genetic Algorithm with modified objective function in Matlab. The identified parameters were applied to the finite element model of the multi-dowel specimens. The simulation results were in good agreement with the test results, and the validity of the numerical model and parameter identification method was verified.
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Papandrea, Salvatore F., Maria F. Cataldo, Bruno Bernardi, Giuseppe Zimbalatti e Andrea R. Proto. "The Predictive Accuracy of Modulus of Elasticity (MOE) in the Wood of Standing Trees and Logs". Forests 13, n. 8 (11 agosto 2022): 1273. http://dx.doi.org/10.3390/f13081273.
Testo completoAbstract (sommario):
The characterization of poplar wood assumes a strategic position to increase the competitiveness of the entire forest wood supply chain. From this aspect, the identification of wood quality represents a primary objective for researchers and private landowners. The quality of wood can be defined via traditional visual methods based on the experience of technicians or using traditional tools, such as incremental drills and sound hammers. The traditional properties of these traits, based only on visual characteristics, can outline a classification based on the macroscopic properties of wood with the aim of defining the volume of recoverable wood. However, this approach does not provide a good indicator of the physical or mechanical properties of wood. Mechanical tests of wood require the felling of trees with the correlated preparation of the specimens. A different solution to determine wood quality is based on the application of non-destructive technology (NDT). In this context, the aim of the present study was to determine the predictive accuracy of non-destructive analysis of the MOEd in standing trees and logs of a 22-year-old poplar clone and to examine the relationship with MOEs in sawn specimens. This relationship was also studied at three different stem heights. We non-destructively measured poplar trees and green logs using TreeSonic and Resonance Log Grader and compared the results with those obtained via a destructive method using a universal testing machine. The results showed that for clone I-214 poplar trees, the dynamic elastic moduli of standing trees and logs were validly correlated with the static elastic modulus. These results suggest that it is possible to evaluate the mechanical properties of poplar wood directly from standing trees using non-destructive techniques (NDT) and that this tool can be easily used to presort material in the forest.
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Hounlonon, Montcho Crépin, Adéyèmi Clément Kouchadé, Alexis Enagnon MEDEHOUENOU, Vincent GOHOUNGO, Aristide Comlan HOUNGAN e Basile Bruno KOUNOUHEWA. "Physical, Mechanical and Acoustic Characteristics of Anogeissus leiocarpus, Manilkara multinervis and Cylicodiscus gabunen-sis Woods Marketed in Benin in West Africa". International Journal of Engineering & Technology 11, n. 2 (24 novembre 2022): 103–7. http://dx.doi.org/10.14419/ijet.v11i2.32049.
Testo completoAbstract (sommario):
Wood is a material used in construction, in instrument making, etc. In Benin, for heavy construction and construction on wetland, species with high technological characteristics are imported. But the performance of these imported species compared to local indigenous or exotic species remains to be verified. Thus, it is necessary to determine the basic technological properties of these species. It is within this framework that we have, on 500mm×20mm×20mm prismatic wood specimens of Anogeissus leiocarpus, Manilkara multinervis and Cylicodiscus gabunensis, used the acoustic method BING (Beam Identification by Non-destructive Grading) of CIRAD-Forest to determine the density Ï, the moduli of Young's modulus E, shear modulus G and the internal friction tan𛿠and then evaluated the modulus of specific stiffness E/Ï. On other 20 mm edge cubic specimens, we evaluated the reference physical properties of density, infradensity, total shrinkage, radial shrinkage, tangential shrinkage and shrinkage anisotropy. It appears that the wood of Anogeissus leiocarpus and Manilkara multinervis present better physico-mechanical characteristics than those of Cylicodiscus gabunensis. Anogeissus leiocarpus and Manilkara multinervis are very dense woods with physico-mechanical characteristics better than those of most Benin's popular species. The average modulus of elasticity in bending of these two species is higher than 12000 MPa while that of Cylicodiscus gabunensis is 10713 MPa. In compression all these species have an average modulus of elasticity above 14100 MPa. Cylicodiscus gabunensis wood tested is light with a lower shrinkage anisotropy than the other two species studied and have excellent acoustic properties. Its average specific stiffness (14 GPa) is higher than that of the other two species studied (12 GPa). The good physical-mechanical and acoustic properties of these species show that they are good structural timbers with also good potential for instrument making and acoustic insulation.Keywords: BING; Construction; Infradensity; Modulus of elasticity; Shrinkage anisotropy; Timber.
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Kojima, Yoichi, Naho Kato, Kazuaki Ota, Hikaru Kobori, Shigehiko Suzuki, Kenji Aoki e Hirokazu Ito. "Cellulose Nanofiber as Complete Natural Binder for Particleboard". Forest Products Journal 68, n. 3 (2018): 203–10. http://dx.doi.org/10.13073/fpj-d-18-00034.
Testo completoAbstract (sommario):
Abstract The demand for wood-based materials as an alternative to plywood is increasing, and a synthetic adhesive is typically used for the fabrication of such materials. The identification of replacements for standard adhesives poses a major challenge. In this study, we investigated the mechanical properties of particleboard bonded by cellulose nanofiber (CNF) and compared the mechanical properties of particleboard bonded by CNF with those of particleboard bonded by adhesive. CNF was added together with wood particles during the fabrication process. The target CNF addition amounts were 0, 3, 5, 10, and 20 weight percent. The bending and internal bond strengths of the particleboard with CNF increased, and its water absorption decreased as CNF content increased. The comparison between the boards prepared with adhesives and those with CNF showed that the properties of boards prepared with 20 weight percent CNF were comparable to those of boards prepared with 1 weight percent synthetic adhesive.
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Yang, Weiwei, Wanrong Ma e Xinyou Liu. "Evaluation of Deterioration Degree of Archaeological Wood from Luoyang Canal No. 1 Ancient Ship". Forests 15, n. 6 (31 maggio 2024): 963. http://dx.doi.org/10.3390/f15060963.
Testo completoAbstract (sommario):
This study provides a detailed investigation of archaeological wood samples from the Luoyang Canal No. 1 site, focusing on wood species identification, physical properties, mechanical property analyses, and morphological examination. The identified wood species, belonging to the Ulmus genus, exhibited a 43% decline in compressive strength in waterlogged environments. Further, the wood exhibited increased moisture content, higher porosity, reduced basic density, and elevated shrinkage rates, indicating a mild level of degradation. X-ray diffraction was employed for the observation of cellulose structure, and Fourier transform infrared spectroscopy (FT-IR) demonstrated significant removal of cellulose and hemicellulose components. These findings emphasize the importance of understanding wood degradation mechanisms to evaluate structural integrity and durability in guiding the development of effective preservation strategies for archaeological wood artifacts. Continued research and conservation are crucial to deepen our knowledge of wood deterioration processes and enhance the implementation of preservation techniques.
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Frodeson, Stefan, Anthony Ike Anukam, Jonas Berghel, Magnus Ståhl, Rasika Lasanthi Kudahettige Nilsson, Gunnar Henriksson e Elizabeth Bosede Aladejana. "Densification of Wood—Influence on Mechanical and Chemical Properties when 11 Naturally Occurring Substances in Wood Are Mixed with Beech and Pine". Energies 14, n. 18 (17 settembre 2021): 5895. http://dx.doi.org/10.3390/en14185895.
Testo completoAbstract (sommario):
The need to increase the use of renewable biomasses for energy supply, such as fuel pellets is significant. However, different types of biomasses have different mechanical properties to be pelletized, which entails a limitation in available raw materials for pellet producers. Within this study eleven different pure substances from biomasses were separately mixed with European beech and Scots pine, to identify its impact on the densification process. Beech and pine pellets were used as control materials against their corresponding pellets mixed with substances representing: cellulose, hemicelluloses, other polysaccharides, lignin, protein, and extractives. The mechanical properties were investigated as well as FT-IR and SEM analyses on the pellets. The results showed that the addition of the substances xylan and galactan created the hardest pellets for both pine and beech and that adding extractives to wood affects pine more than beech in relation to hardness. The FT-IR data could not provide clear explanations as to the variation in hardness and springback behavior through the identification of major functional groups in each pellet. It can be concluded that biomass residues rich in xylan and galactan increase pellet quality in terms of strength and durability without affecting the production process.
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Pan, Shen, e Zhanyuan Chang. "WD-1D-VGG19-FEA: An Efficient Wood Defect Elastic Modulus Predictive Model". Sensors 24, n. 17 (28 agosto 2024): 5572. http://dx.doi.org/10.3390/s24175572.
Testo completoAbstract (sommario):
As a mature non-destructive testing technology, near-infrared (NIR) spectroscopy can effectively identify and distinguish the structural characteristics of wood. The Wood Defect One-Dimensional Visual Geometry Group 19-Finite Element Analysis (WD-1D-VGG19-FEA) algorithm is used in this study. 1D-VGG19 classifies the near-infrared spectroscopy data to determine the knot area, fiber deviation area, transition area, and net wood area of the solid wood board surface and generates a two-dimensional image of the board surface through inversion. Then, the nonlinear three-dimensional model of wood with defects was established by using the inverse image, and the finite element analysis was carried out to predict the elastic modulus of wood. In the experiment, 270 points were selected from each of the four regions of the wood, totaling 1080 sets of near-infrared data, and the 1D-VGG19 model was used for classification. The results showed that the identification accuracy of the knot area was 95.1%, the fiber deviation area was 92.7%, the transition area was 90.2%, the net wood area was 100%, and the average accuracy was 94.5%. The error range of the elastic modulus prediction of the three-dimensional model established by the VGG19 classification model in the finite element analysis is between 2% and 10%, the root mean square error (RMSE) is about 598. 2, and the coefficient of determination (R2) is 0. 91. This study shows that the combination of the VGG19 algorithm and finite element analysis can accurately describe the nonlinear defect morphology of wood, thus establishing a more accurate prediction model of wood mechanical properties to maximize the use of wood mechanical properties.
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Kloiber, Michal, Mária Kotlínová e Jan Tippner. "Estimation of wood properties using pin pushing in method with various shapes of the penetration pin". Acta Universitatis Agriculturae et Silviculturae Mendelianae Brunensis 57, n. 2 (2009): 53–60. http://dx.doi.org/10.11118/actaun200957020053.
Testo completoAbstract (sommario):
The existing penetration methods for the identification of the density of wood that forms a part of structures do not make it possible to describe the density in the entire element profile but only on its surface. However, wood density changes throughout the profile which affects the accuracy of the density determination. The instruments used until now based on the principle of a pin shot into the material thus needed to be supplemented with a test during which the pin would be pushed at least to the centre of the measured element. Pins of 3 mm in diameter were manufactured with a special jig fastening them to a universal testing machine. Using the testing machine, the force required to push the pin in was measured at a constant travel speed. It has been found out that the mechanical work needed for the pin penetration correlates very well with the wood density determined in the surroundings of the place where the pin was pushed in.
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Mertz, Mechtild, Sangeeta Gupta, Yutaka Hirako, Pimpim de Azevedo e Junji Sugiyama. "WOOD SELECTION OF ANCIENT TEMPLES IN THE SIKKIM HIMALAYAS". IAWA Journal 35, n. 4 (6 dicembre 2014): 444–62. http://dx.doi.org/10.1163/22941932-00000077.
Testo completoAbstract (sommario):
Microscopic wood identifications were performed on five Buddhist temple structures and on one secular building located in Sikkim, an Indian state in the Eastern Himalayas. In all, twenty wood species were identified, two of which – Michelia (Magnolia) doltsopa and Picea cf. spinulosa – were considered in more detail. Building type, specific physical and mechanical properties of the wood species, local availability, and religious considerations were apparently the leading criteria for timber selection.
Tesi sul tema "Identification of mechanical wood properties"
1
Šećerović, Amra. "Identification and characterization of molecular players potentially responsible for the mechanical properties of tension wood". Thesis, Orléans, 2016. http://www.theses.fr/2016ORLE2066/document.
Testo completoAbstract (sommario):
Le but de cette thèse était d’identifier les mécanismes moléculaires responsables des propriétés particulières de la couche G et les propriétés mécaniques remarquables du bois de tension (BT). Trois acteurs moléculaires potentiels (des protéines à arabinogalactane avec domaine fasciclin-like (FLA), une protéine chitinase-like (CTL) et une β-galactosidase (BGAL)) ont été choisis et étudiés dans: analyse phylogénétique, analyses d'expression et caractérisation de peupliers transgéniques affectés dans l’expression de chacun de ces acteurs. La caractérisation fine de ce matériel a révélé que CTL2 et les FLA jouent un rôle dans la régulation de la cristallinité de la cellulose dans le BT. CTL2 apparaît également important dans l'organisation de la paroi cellulaire et des propriétés mécaniques des tiges. BGAL a été avant proposé pour une fonction dans modification de pectine RG-I potentiellement important pour des propriétés mécaniques de BT. Le bois de tension exhibe une activité BGAL plus élevée que dans le bois opposé. L’inhibition par RNAi de l’expression de BGAL7, spécifiquement exprimée dans le BT, n’est pas responsable à lui seul de la forte activité BGAL présente dans le BT. En contrepoint à l’étude menée sur le peuplier, nous avons également évalué la présence d’acteurs moléculaires potentiellement responsables des propriétés mécaniques du BT chez le simarouba qui développe dans leur BT des fibres ayant leurs sous-couches de la paroi intermédiaire entre la G et la S2. Des protéines à arabinogalactanes ainsi que des pectines du type RG-I sont présentes dans les fibres de BT de peuplier et de simarouba et pourraient avoir une fonction dans un mécanisme commun de génération des contraintes dans le BT. Finalement, un modèle est proposé sur le rôle présumé des différents acteurs moléculaires étudié dans la régulation des propriétés de la couche G et la génération des fortes contraintes du bois de tensionThe aim of this thesis was to approach the underlying molecular mechanisms responsible for the particular properties of the G-layer and the outstanding mechanical properties of tension wood (TW). Accordingly, three potential molecular players (fasciclin-like arabinogalactan protein (FLA), chitinase-like protein (CTL) and β-galactosidase (BGAL)) were chosen and studied through a phylogenetic analysis, expression analyses and most importantly characterization of RNAi transgenic poplars. This multilevel characterization revealed that CTL2 and FLAs have function in the regulation of cellulose crystallinity in TW. CTL2 was also shown to be important both for the cell wall organization and stem mechanical properties. BGAL was studied in a light of the previously reported modifications of RG-I pectin, potentially important for the mechanical properties of TW. Study of BGAL revealed that the enzyme has higher activity in TW than in opposite wood. BGAL7, whose gene was expressed specifically in TW, does not seem to be responsible for the higher BGAL activity in TW. In comparison to poplar, we analyzed the occurrence of molecular players potentially responsible for TW mechanical properties in simarouba, a tropical species, which develops different TW fiber. Arabinogalactan proteins and RG-I pectin potentially targeted by BGAL were localized in TW fibers both in poplar and simarouba and therefore may be involved in a common mechanism of tensile stress generation in different TW types. A model was finally proposed to elucidate a potential function of the studied molecular players in the regulation of G-layer properties and tensile stress generation
2
Broman, Olof. "Means to measure the aesthetic properties of wood". Doctoral thesis, Luleå tekniska universitet, Träteknologi, 2000. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-16967.
Testo completoAbstract (sommario):
Wood is a biological material with inherent aesthetic properties which can give the final product a competitive advantage over other materials. In this thesis, people’s feelings and preferences for Scots pine (Pinus sylvestris) wood surfaces have been examined. The main objectives of this thesis are to develop methods for measuring people’s preferences toward different looks of wood and to connect the subjective preference data with objective measurements of wood features. It comprises both qualitative and quantitative methods for collecting preference data. Two projection methods, PCA and PLS, were used to analyze the quantitative studies. Interviews made clear that people prefer different blends of wood features. There are two qualitative differences that are of importance for people's impressions and valuations of wood: The overall blend of wood features and divergent features that mismatch in a surface. It was found that divergent features are more important than the overall mixture of features. But if there are no defects that mismatch, the overall mixture will then be the key to a person's appreciation of a wood surface. Wood surfaces should stimulate people's interest and be fresh looking. A clear surface is naturally rather harmonious, elegant and easy to look at. On the other hand, a clear surface should be stimulating to look at, should be exciting and it should not look like an imitation. Knotty surfaces usually are less harmonious. Therefore, questions about harmony, easiness to look at and balance are of importance. Just as for clear surfaces, a knotty surface should also stimulate people's interest, have a fresh look, be exciting and stimulating to look at. The quantitative studies show that it is possible to measure people’s preferences toward wood by a questionnaire technique. The results also show that there are differences in people’s judgments for surfaces with knots and for those without knots. There are stronger connections between questions regarding the overall impression and the final assessment than there are for detailed questions regarding certain wood features. Thirteen questions were pointed out as relevant to use with interviews. Two interview methods were compared. The first method used wood surfaces and the second used computer images with the same wood surfaces applied to an example product, a kitchen cabinet. The results show that the two methods are comparable and useful. It was shown that it is possible to some extent to connect subjective preference data with objective wood feature measurements. Results show that a lot of wood feature measurements are needed and that it is a multivariate problem. Concerning the measurements, it seems easier to find features that negatively affect people’s liking than to find the opposite. Among the most important variables were those that detect different kinds of feature distribution over a wood surface, and especially those variables that detect a deviation in center of gravity. Increased knowledge about people’s preferences for the aesthetic properties of wood will lead to a better understanding of which wood features should be measured and controlled in the future.Godkänd; 2000; 20061116 (haneit)
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Oksman, Kristiina. "Improved properties of thermoplastic wood flour composites". Doctoral thesis, Luleå tekniska universitet, Materialvetenskap, 1997. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-26513.
Testo completoAbstract (sommario):
In this study the properties of composites made of wood flour and thermoplastics have been investigated. In order to improve the interfacial adhesion between hydrophobic and nonpolar thermoplastics and hydrophilic and polar wood flour different additives have been used as compatibilizers in composites systems. The interaction between a wood filler and thermoplastic matrix, with and without compatibilizers, has been studied using conventional mechanical testing, impact testing, dynamic mechanical thermal analysis (DMTA), electron microscopes and infrared spectroscopy. Tests of mechanical properties, such as maximum tensile strength, tensile modulus and impact strength have shown that maleic anhydride grafted styrene-ethylene/butylene-styrene triblock copolymer (SEBS-MA) acts as a compatibilizer in the composite system. The SEBS-MA improves the stress transfer from the matrix to the wood particles and forming an flexible interphase around the wood particle and therefore improves the impact properties. The DMTA measurements indicated that there is an interaction between the wood surfaces and the maleic anhydride part of the SEBS-MA copolymer, and also between PS and wood. Morphological studies with SEM and TEM showed that the addition of SEBS-MA improved the adhesion between the wood particles and polymer matrix and that the compatibilizer is located at the interphase region between them. An infrared spectroscopy study indicated that the MA in the SEBS may react with the wood by forming hydrogen- and esterbonds and also possibly interaction between PS and wood.Godkänd; 1997; 20061128 (haneit)
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Kirkpatrick, John Warren. "Mechanical and physical properties of preservative-treated strandboard". Master's thesis, Mississippi State : Mississippi State University, 2005. http://sun.library.msstate.edu/ETD-db/ETD-browse/browse.
Testo completo
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Noel, Matthieu. "Modélisation déterministe et probabiliste de la rupture par champ de phase et identification expérimentale pour la fissuration des structures en bois dans l’ameublement". Electronic Thesis or Diss., Université Gustave Eiffel, 2024. http://www.theses.fr/2024UEFL2061.
Testo completoAbstract (sommario):
Dans le domaine de l'ameublement, garantir la sécurité des structures conformément aux normes européennes représente un enjeu important pour les fabricants de meubles. Avant leur commercialisation, les meubles sont soumis à des tests de validation normalisés, qui ne permettent de connaître leur comportement mécanique qu'a posteriori. Cette thèse vise à développer des outils de modélisation et de simulation numérique pour prédire la rupture par fissuration au niveau des connexions entre les éléments de meuble. Pour atteindre cet objectif, l'approche méthodologique combine la modélisation et la simulation numérique avec des essais expérimentaux. Elle utilise la méthode des éléments finis couplée à des modèles de rupture/endommagement par champ de phase pour simuler la fissuration dans des matériaux élastiques linéaires isotropes et anisotropes, dans un cadre déterministe et probabiliste. Une campagne d'essais expérimentaux est menée sur des échantillons d'épicéa troués soumis en compression uniaxiale, afin de reproduire les mécanismes de fissuration observés dans des structures réelles, notamment dans les connexions de lits en hauteur. Une procédure d'identification est développée et mise en place pour caractériser les propriétés élastiques et d'endommagement de l'épicéa, en exploitant notamment des mesures expérimentales de champs de déplacement obtenues par corrélation d'images numériques. Une méthode d'accélération des simulations d'endommagement par champ de phase est proposée pour réduire leur coût élevé en temps de calcul. Cette approche permet de prédire, indépendamment du type de connexions, le déplacement ou la force critique précédant l'amorçage de la fissuration. Les résultats numériques indiquent que, sous réserve d'appliquer des conditions aux limites réalistes et d'avoir correctement identifié les propriétés du matériau, le critère d'amorçage de fissure s'avère utile pour prédire l'emplacement des zones potentiellement endommagées/fissurées et fournir un ordre de grandeur cohérent pour l'effort ou le déplacement nécessaire à l'initiation de la fissuration. Ce critère requiert seulement une unique simulation dans le domaine élastique linéaire, suivi d'un post-traitement avec un modèle d'endommagement par champ de phase, afin de faciliter son utilisation dans un contexte industriel, en particulier le secteur de l'ameublement. Les outils numériques développés, accessibles en open source, pourraient aider les industriels de l'ameublement à prédire la rupture fragile dans le bois et à optimiser la conception des meubles, tout en garantissant la conformité aux normes de sécuritéIn the furniture industry, ensuring the safety of structures in accordance with European standards presents a significant challenge for furniture manufacturers. Before commercialization, furniture are subjected to standardized validation tests, which only allow for a retrospective understanding of its mechanical behavior. This thesis aims to develop modeling and numerical simulation tools to predict the cracking failure mechanism at the connections between furniture elements. To achieve this objective, the methodological approach combines modeling and numerical simulation with experimental testing. It employs the finite element method coupled with phase-field fracture/damage models to simulate cracking in linear elastic isotropic and anisotropic materials within a deterministic and probabilistic framework. An experimental testing campaign is conducted on perforated spruce wood samples subjected to uniaxial compression to reproduce the cracking mechanisms observed in real structures, particularly in the connections of high loft beds. An identification procedure is developed and implemented to characterize the elastic and damage properties of spruce wood, in particular by exploiting experimental displacement field measurements obtained through digital image correlation. A method for accelerating phase-field damage simulations is proposed to reduce their high computational cost. This approach allows for the prediction, independently of the type of connections, of the displacement or critical force preceding crack initiation. The numerical results indicate that, provided realistic boundary conditions are applied and the material properties are correctly identified, the crack initiation criterion is useful for predicting the location of potentially damaged/cracked areas and providing a consistent order of magnitude of the force or displacement required to initiate cracking. This criterion only requires a single linear elastic simulation, followed by a post-processing with a phase-field damage model, to facilitate its use in an industrial context, in particular the furniture sector. The numerical tools developed, available in open source, could help furniture manufacturers to predict brittle fracture in wood and optimize furniture design, while guaranteeing compliance with safety standards
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Gade, Jan-Lucas. "Mechanical Properties of Arteries : Identification and Application". Licentiate thesis, Linköpings universitet, Mekanik och hållfasthetslära, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:liu:diva-159942.
Testo completoAbstract (sommario):
In this Licentiate of Engineering thesis, a method is proposed that identifies the mechanical properties of arteries in vivo. The mechanical properties of an artery are linked to the development of cardiovascular diseases. The possibility to identify the mechanical properties of an artery inside the human body could, thus, facilitate disease diagnostization, treatment and monitoring. Supplied with information obtainable in the clinic, typically limited to time- resolved pressure-radius measurement pairs, the proposed in vivo parameter identi- fication method calculates six representative parameters by solving a minimization problem. The artery is treated as a homogeneous, incompressible, residual stress- free, thin-walled tube consisting of an elastin dominated matrix with embedded collagen fibers referred to as the constitutive membrane model. To validate the in vivo parameter identification method, in silico arteries in the form of finite element models are created using published data for the human abdominal aorta. With these in silico arteries which serve as mock experiments with pre-defined material parameters and boundary conditions, in vivo-like pressure-radius data sets are generated. The mechanical properties of the in silico arteries are then determined using the proposed parameter identification method. By comparing the identified and the pre-defined parameters, the identification method is quantitatively validated. The parameters for the radius of the stress-free state and the material constant associated with elastin show high agreement in case of healthy arteries. Larger differences are obtained for the material constants associated with collagen, and the largest discrepancy occurs for the in situ axial prestretch. For arteries with a pathologically small elastin content, incorrect parameters are identified but the presence of a diseased artery is revealed by the parameter identification method. Furthermore, the identified parameters are used in the constitutive membrane model to predict the stress state of the artery in question. The stress state is thereby decomposed into an isotropic and an anisotropic component which are primarily associated with the elastin dominated matrix and the collagen fibers, respectively. In order to assess the accuracy of the predicted stress, it is compared to the known stress state of the in silico arteries. The comparison of the predicted and the in silico decomposed stress states show a close agreement for arteries exhibiting a low transmural stress gradient. With increasing transmural stress gradient the agreement deteriorates. The proposed in vivo parameter identification method is capable of identifying adequate parameters and predicting the decomposed stress state reasonably well for healthy human abdominal aortas from in vivo-like data.In diesem Lizentiat der Ingenieurwissenschaften wird eine Methode zur Identifikation der mechanischen Eigenschaften von Arterien in vivo vorgestellt. Die mechanischen Eigenschaften einer Arterie sind mit der Ausbildung kardiovaskulärer Krankheiten verknüpft und deren Identifikation hat daher das Potenzial die Diagnose, die Behandlung und die Überwachung dieser Krankheiten zu verbessern. Basierend auf klinisch möglichen Messungen, die üblicherweise auf ein zeitaufgelöstes Druck-Radiussignal limitiert sind, werden sechs repräsentative Parameter durch Lösen eines Minimierungsproblems berechnet. Die sechs Parameter sind dabei die Eingangsparameter des zur Hilfe gezogenen konstitutiven Schalenmodells welches eine Arterie als eine homogene, inkompressible, restspannungsfreie und dünnwandige Röhre beschreibt. Weiterhin wird angenommen, dass die Arterienwand aus einer elastindominierten Matrix mit eingebetteten Kollagenfasern besteht. Um die in vivo Parameteridentifikationsmethode zu validieren, werden in silico Arterien in Form von Finite Elemente Modellen erstellt. Diese in silico Arterien beruhen auf publizierten Materialparametern der menschlichen Abdominalaorta und dienen als Pseudoexperimente mit vordefinierten mechanischen Eigenschaften und Randbedingungen. Mit diesen Arterien werden in vivo-ähnliche Druck-Radiussignale erstellt und anschliesend werden ihre mechanischen Eigenschaften mit Hilfe der Parameteridentifikationsmethode bestimmt. Der Vergleich der identifizierten und der vordefinierten Parameter ermöglicht die quantitative Validierung der Methode. Die Parameter des spannungsfreien Radius und der Materialkonstanten für Elastin weisen hohe Übereinstummung im Falle gesunder Arterien auf. Die Abweichung der Materialkonstanten für Kollagen sind etwas gröser und der gröste Unterschied tritt beim axialen in situ Stretch auf. Für Arterien mit einem pathologisch geringen Elastinbestandteil werden falsche Parameter identifiziert, wobei die Parameteridentifikationsmethode eine krankhafte Arterie offenlegt. Weiterhin werden mit Hilfe der identifizierten Parameter und des konstitutiven Schalenmodells der Spannungszustand in der Arterienwand berechnet. Dieser ist dabei aufgeteilt in einen isotropen und einen anisotropen Anteil. Der isotrope Anteil wird mit der elastindomierten Matrix und der anisotrope Anteil mit den Kollagenfasern verknüpft. Um die Genauigkeit des berechneten Spannungszustandes beurteilen zu können, wird dieser mit dem Zustand in den in silico Arterien verglichen. Im Fall von Arterien, die einen geringen transmuralen Spannungsgradienten aufweisen, entspricht der berechnete Spannungszustand dem in silico Zustand. Mit zunehmendem transmuralen Spannungsgradienten lässt die Übereinstimmung nach. Für die gesunde menschliche Abdominalaorta ist die entwickelte in vivo Parameteridentifikationsmethode in der Lage, basierend auf in vivo-ähnlichen Messsignalen, adäquate Parameter zu identifizieren und einen zufriedenstellenden Spannungszustand zu berechnen.
I denna licentiatavhandling föreslås en metod för att identifiera mekaniska egenskaper hos artärer in vivo. De mekaniska egenskaperna är kopplade till utvecklingen av hjärt-kärlsjukdomar, och möjligheten att identifiera dessa egenskaper skulle således kunna underlätta diagnostisering, behandling och uppföljning av dessa sjukdomar. Den förslagna metoden använder kliniskt mätbara tryck-radie-signaler och löser ett minimeringsproblem för att bestämma sex parametrar som beskriver kärlets mekaniska egenskaper. Artären modelleras som ett homogent, inkompressibelt och spänningsfritt tunnväggigt rör där kärlväggen utgörs av en elastindominerad matris armerad med inbäddade kollagenfibrer. För att validera parameteridentifieringen skapas en uppsättning representativa, virtuella artärer med hjälp av finita element. Dessa in silico-artärer baseras på publicerade data för mänsklig bukaorta och används för att generera fiktiva tryckradie-signaler vilka sedan matas in i den förslagna modellen. Genom att parametrar och randvillkor för in silico-artärerna är kända fungerar dessa som en kontroll mot vilka resultatet från parameteridentifieringen kan jämföras. Parametrarna som beskriver den icke trycksatta radien och den elastindominerade matrisen visar god överensstämmelse med de in silico-artärerna för friska kärl. Större diskrepans erhålls för de parametrar som associeras med kollagenet, och den största avvikelsen erhålls för den parameter som beskriver den axiella försträckningen. För artärer med patologiskt lågt elastininnehåll identifieras felaktiga parametrar, men resultatet avslöjar ändå tydligt en sjuk artär. De identifierade parametrarna har också använts för att jämföra spänningstillst åndet i membranmodellen och in silico-artäreren. Spänningstillståndet har delats upp i en isotrop och en anisotrop komponent svarande mot, i huvudsak, den elastindominerade matrisen samt kollagenfibrerna. Resultatet visar en mycket god överensstämmelse för bägge komponenterna hos in silico-artärer med låg spänningsgradient genom väggen. Med ökande spänningsgradient försämras dock överensstämmelsen. Resultatet visar att den förslagna metoden är kapabel att identifiera adekvata parametrar och att förutsäga spänningskomponenterna i en frisk aorta.
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Ashaduzzaman, Md. "Physico-mechanical and decay resistance properties of bio-resin modified wood". Thesis, Bangor University, 2014. https://research.bangor.ac.uk/portal/en/theses/physicomechanical-and-decay-resistance-properties-of-bioresin-modified-wood(f4588ffc-250d-4f89-95f5-8f9ea381dba7).html.
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Huang, Sheng. "Experiment study of the mechanical properties of timber materials under various humidity condition". Thesis, University of Macau, 2018. http://umaclib3.umac.mo/record=b3950672.
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Ozden, Seray. "The relationship between the anatomy and mechanical properties of different green wood species". Thesis, University of Manchester, 2016. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.684776.
Testo completoAbstract (sommario):
Trees are exposed to many stresses over their lifetime and withstand them due to their woody skeleton which provides excellent mechanical support. Wood has therefore been one of the most used materials throughout the history of humanity. However, the mechanical properties of wood vary considerably depending on wood anatomy and also show significant differences between and within trees. Wood is a cellular solid, characterised by a high degree of anisotropy at all levels of organisation and is formed by cells which are oriented largely in the longitudinal and radial directions, making wood mechanics rather complicated. Therefore, there is a need for an understanding of the mechanical properties of wood in different species and in different parts of the tree and its relationship to wood anatomy. This study began with two investigations into the transverse toughness of green trunk wood in different tree species including both hardwood and conifers. Double-edge notched tensile tests were conducted on the specimens to quantify their specific fracture energies and evaluate their failure fashions. The influence of wood anatomy on the toughening mechanism of wood was observed using both electron microscopy and light microscopy. It was found that the fracture properties of woods were mainly affected by the wood density and anatomy. Hardwoods were found to have higher fracture energies than conifers due to their denser woods and higher volume fraction of rays. The results also found that the specific fracture energies of RL and RT systems were around 1.5-2 times greater than TL and TR systems. This difference was mainly explained by the presence of rays which provided toughness in the radial direction, at least in hardwoods, as breaking across rays resulted in spiral fractures of the cell walls. The mechanical properties of green branches and coppice shoots of three temperate tree species (chestnut, sycamore and ash), were then investigated at three distances from the tip. The study also investigated how bending failure was influenced by the morphology and anatomy of branches and coppice shoots. Coppice shoots were shown to be more likely to buckle in bending, whereas branches failed with a clean fracture. It was shown that ash and sycamore had greater properties in their coppice shoots than their branches, while chestnut showed better properties in their branches. It was suggested that this occurred because increasing the leaf node frequency resulted in a decrease in mechanical properties; ash and sycamore had more leaf nodes in their branches, thus lower properties in their branches, while chestnut had more leaf nodes in its coppices. The mechanical properties also decreased from base to tips of branches and coppice shoots because of falls in diameter of shoots and wood density. The results also suggested why coppice shoots can act as a useful structural material. Finally, this thesis investigated how and why the fracture properties vary around the structure of tree forks. The fracture properties of green hazel forks were examined using double-edge notched tensile tests in the RT and TR directions. The fracture surfaces were also observed using scanning electron microscopy in both fracture systems. The results showed that the central apex of forks were considerably tougher than other locations, suggesting they provide the load-bearing capacity of tree forks. It was shown that the increased toughness was related to both higher wood density and an interlocking wood grain pattern. Interestingly, the TR fracture system was found to be tougher than the RT fracture system at the central apex of forks, probably related to the orientation of the fibres. These results provide insight into the relationship between wood mechanics and anatomy, particularly showing the importance of rays. They can also help us understand how our ancestors shaped wood and designed tools and how we could design better structures.
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Anderson, Scott Powell. "Wood fiber reinforced bacterial biocomposites effects of interfacial modifers and processing on mechanical and physical properties /". Online access for everyone, 2007. http://www.dissertations.wsu.edu/Thesis/Fall2007/S_Anderson_100507.pdf.
Testo completoLibri sul tema "Identification of mechanical wood properties"
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Liu, Peng. Identification, properties and uses of some Southeast Asian woods. Yokohama, Japan: International Tropical Timber Organization, 1988.
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Bunster, Jaime H. 52 madeiras de Moçambique: Catálogo tecnológico. Maputo: Universidade Eduardo Mondlane, Faculdade de Agronomia e Engenharia Florestal, Departamento de Engenharia Florestal, 1995.
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European Mechanics Colloquium 269, "Experimental Identification of the Mechanical Characteristics of Composite Materials and Structures" (1990 Saint-Etienne, Loire, France). Mechanical identification of composites. London: Elsevier Applied Science, 1991.
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Kettunen, P. O. Wood structure and properties. Uetikon-Zuerich: Trans Tech Publications Ltd., 2006.
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Iqbal, Mahmood, AGA Khan Rural Support Programme. e Pakistan Forest Institute, a cura di. Mechanical properties of farmland trees of Northern ares. Gilgit: The AGA Khan Rural Support Programme, 2004.
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T. A. C. M. van der Put. A new fracture mechanics theory of wood. New York: Nova Science Publishers, 2011.
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Williams, Derek. Machining and related mechanical properties of 15 B.C. wood species. Vancouver, B.C: Forintek Canada Corp., Western Division, 1998.
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Parant, B. Timbers of Guadeloupe. Nogent-sur-Marne, France: Centre Technique Forestier Tropical, 1987.
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Instituto Forestal (Santiago, Chile). División Industrias. e Corporación de Fomento de la Producción (Chile). Gerencia de Desarrollo., a cura di. Clasificación estructural mecánica de la madera: Principios y aplicación. Santiago, Chile: Instituto Forestal, División Industrias, 1987.
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Park, Byung Dae. Effects of impact modifiers on the mechanical properties of wood-fibre polypropylene composites. Ottawa: National Library of Canada = Bibliothèque nationale du Canada, 1993.
Cerca il testo completoCapitoli di libri sul tema "Identification of mechanical wood properties"
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Prosvirnikov, D. B. "Modeling of the Properties of Wood Composite Materials by Parametric Identification". In Lecture Notes in Mechanical Engineering, 298–307. Cham: Springer International Publishing, 2022. http://dx.doi.org/10.1007/978-3-030-85230-6_35.
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Olorunnisola, Abel O. "Mechanical Properties of Wood". In Design of Structural Elements with Tropical Hardwoods, 31–47. Cham: Springer International Publishing, 2017. http://dx.doi.org/10.1007/978-3-319-65343-3_3.
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Schniewind, Arno P. "Physical and Mechanical Properties of Archaeological Wood". In Archaeological Wood, 87–109. Washington, DC: American Chemical Society, 1989. http://dx.doi.org/10.1021/ba-1990-0225.ch004.
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Gogoi, Rupam, e Gaurav Manik. "Mechanical Properties of Wood Polymer Composites". In Wood Polymer Composites, 113–36. Singapore: Springer Singapore, 2021. http://dx.doi.org/10.1007/978-981-16-1606-8_6.
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Björkman, A., e Helena Lassota. "Mechanical Properties of Chemically Treated Wood". In Viscoelasticity of Biomaterials, 65–81. Washington, DC: American Chemical Society, 1992. http://dx.doi.org/10.1021/bk-1992-0489.ch005.
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Clair, Bruno, e Bernard Thibaut. "Physical and Mechanical Properties of Reaction Wood". In The Biology of Reaction Wood, 171–200. Berlin, Heidelberg: Springer Berlin Heidelberg, 2013. http://dx.doi.org/10.1007/978-3-642-10814-3_6.
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Rouger, F., M. Khebibeche e C. Le Govic. "Non Determined Tests as a Way to Identify Wood Elastic Parameters the Finite Element Approach". In Mechanical Identification of Composites, 82–90. Dordrecht: Springer Netherlands, 1991. http://dx.doi.org/10.1007/978-94-011-3658-7_8.
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Dual, Jurg, e Mahir Sayir. "Dynamic Measurements of Elastic Properties of Filament — Wound Cylindrical Shells". In Mechanical Identification of Composites, 133–40. Dordrecht: Springer Netherlands, 1991. http://dx.doi.org/10.1007/978-94-011-3658-7_14.
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Milosavljevic, Dragan I. "Dynamic Properties of Layer Reinforced by Two Families of Fibres". In Mechanical Identification of Composites, 262–69. Dordrecht: Springer Netherlands, 1991. http://dx.doi.org/10.1007/978-94-011-3658-7_30.
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Rikards, Rolands. "Identification of Mechanical Properties of Laminates". In Modern Trends in Composite Laminates Mechanics, 181–225. Vienna: Springer Vienna, 2003. http://dx.doi.org/10.1007/978-3-7091-2544-1_4.
Testo completoAtti di convegni sul tema "Identification of mechanical wood properties"
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Yusuf, Uwaisu, Yakubu Musa, T. Musa, José Amir Gonzalez-Calderon, Ma Cristina Irma Peréz-Pérez, Ricardo López-Esparza, Luis O. Sanchez-Vargas, Bernardino I. Cerda-Cristerna, Agustin L. Herrera-May e Enrique Delgado-Alvarado. "Assessment of Thermal and Physico-Mechanical Properties in Recycled LDPE Composite Reinforced with Prosopis africana Wood Powder". In 2024 IEEE International Conference on Engineering Veracruz (ICEV), 1–7. IEEE, 2024. http://dx.doi.org/10.1109/icev63254.2024.10766031.
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Ferreira Pinto, Plinio, e Geoff Rideout. "Development and Validation of an In-Situ Utility Pole Simulation Model for Virtual Modal Testing". In ASME 2016 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2016. http://dx.doi.org/10.1115/imece2016-67463.
Testo completoAbstract (sommario):
Modal testing is being investigated as a non-destructive test (NDT) method for wood poles. Modal properties of the pole must be extracted from sensor data containing frequency content associated with the interaction of the pole with its conductors. A dynamic model of a utility pole with attached conductors has been developed and validated through experimentation. The model will allow controlled, repeatable simulations of modal hammer hits for preliminary verification of pole property identification methods. The cable is modeled as a series of point masses connected by translational springs. The pole is represented by a modal expansion based on separation of variables. To facilitate creating and connecting the pole and cable models, scaling the model to represent longer pole lines, and introducing modal hammer inputs; the bond graph formalism was employed. To validate the model, an instrumented reduced-scale pole and cable system was built and tested in the laboratory. Time series measurements of cable tension and transverse motion, along with frequency-domain accelerometer data, show that the simulation model has sufficient fidelity to predict the effect of conductors on a pole’s response spectrum over the frequency range of interest.
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Berzins, Andris, Andris Morozovs, Uldis Gross e Janis Iejavs. "Mechanical properties of wood-geopolymer composite". In 16th International Scientific Conference Engineering for Rural Development. Latvia University of Agriculture, 2017. http://dx.doi.org/10.22616/erdev2017.16.n251.
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Zaini, A. S. Syah M., Anika Zafiah M. Rus, Norherman Abdul Rahman, Farhana Hazwanee M. Jais, M. Zarif Fauzan e N. Afiqah Sufian. "Mechanical properties evaluation of extruded wood polymer composites". In INTERNATIONAL CONFERENCE “FUNCTIONAL ANALYSIS IN INTERDISCIPLINARY APPLICATIONS” (FAIA2017). Author(s), 2017. http://dx.doi.org/10.1063/1.4999884.
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Samuilova, Evgenia. "THERMAL AND MECHANICAL PROPERTIES OF WOOD-PVC COMPOSITES". In 19th SGEM International Multidisciplinary Scientific GeoConference EXPO Proceedings. STEF92 Technology, 2019. http://dx.doi.org/10.5593/sgem2019/4.1/s17.072.
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Mothilal, T., G. Ragothaman, D. Joseph Manuel, S. Socrates e S. Mathavan. "Analysis on mechanical properties of wood plastic composite". In PROCEEDINGS OF INTERNATIONAL CONFERENCE ON RECENT TRENDS IN MECHANICAL AND MATERIALS ENGINEERING: ICRTMME 2019. AIP Publishing, 2020. http://dx.doi.org/10.1063/5.0024893.
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Wehsener, Jörg, Martina Bremer e Peer Haller. "MECHANICAL PROPERTIES TESTS OF DELIGNIFIED AND DENSIFIED WOOD". In World Conference on Timber Engineering 2023 (WCTE2023). As, Norway: World Conference on Timber Engineering (WCTE 2023), 2023. http://dx.doi.org/10.52202/069179-0095.
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Román, Krisztina, Bence Szemán, Zita Szabó e Kálmán Marossy. "Mechanical properties and structural changes of PVC-wood composites". In MultiScience - XXXII. microCAD International Multidisciplinary Scientific Conference. University of Miskolc, 2018. http://dx.doi.org/10.26649/musci.2018.015.
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Zhu, Jin, Wen Lei, Lei Lei, Tian-qing Wang e Zhe-yu Qian. "Mechanical properties of nano montmorillonite modified wood-plastic composites". In 2011 International Conference on Consumer Electronics, Communications and Networks (CECNet). IEEE, 2011. http://dx.doi.org/10.1109/cecnet.2011.5769421.
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Cavallini Zotelle, Ayrton, Joao Henrique Sartori, Luciano Merlo, Matheus Alves Lima e Antônio Carlos Barbosa Zancanella. "EVALUATION OF THE MECHANICAL PROPERTIES OF BALSA WOOD AND COMPOSITE MATERIALS". In 25th International Congress of Mechanical Engineering. ABCM, 2019. http://dx.doi.org/10.26678/abcm.cobem2019.cob2019-0095.
Testo completoRapporti di organizzazioni sul tema "Identification of mechanical wood properties"
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Hodgdon, Taylor, Brendan West, Julie Parno, Theodore Letcher, Zoe Courville e Lauren Farnsworth. Extracting sintered snow properties from microCT imagery to initialize a discrete element method model. Engineer Research and Development Center (U.S.), settembre 2022. http://dx.doi.org/10.21079/11681/45305.
Testo completoAbstract (sommario):
Modeling snow’s mechanical behavior is important for many cold regions engineering problems. Because snow’s microstructure plays a significant role in its mechanical response, it is imperative to initialize models with accurate bond characteristics and realistic snow-grain geometries to precisely capture the microstructure interactions. Previous studies have processed microcomputed tomography scans of snow samples with a watershed method to extract grain geometries. This approach relies on identification of seed points to segment each grain. Our new methodology, called the “moving window method,” does not require prior knowledge of the snow-grain-size distribution to identify seed points. We use the interconnectivity of the segmented grains to identify bond characteristics. We compare the resultant grain-size and bond-size distributions to the known grain sizes of the laboratory-made snow samples. The grain-size distributions from the moving window method closely match the known grain sizes, while both results from the traditional method produce grains that are too large. We propose that the bond net-work identified using the traditional method underestimates the number of bonds and overestimates bond radii. Our method allows us to segment realistic snow grains and their associated bonds, without prior knowledge of the samples, from which we can initialize numerical models of the snow.
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Brust. L51576 Crack Growth Behavior and Modeling. Chantilly, Virginia: Pipeline Research Council International, Inc. (PRCI), marzo 1989. http://dx.doi.org/10.55274/r0010642.
Testo completoAbstract (sommario):
The objective of the Crack Growth/Modeling effort of the NG-18 Line Pipe Supervisory Committee's Stress-Corrosion Phase is to develop an understanding of the factors that control stress-corrosion crack growth. This information can be used to develop models for predicting crack growth and to mitigate crack growth through control of metallurgical parameters and operating conditions. This effort has been divided into the following four main tasks: (1) Characterization of crack shape,(2) Identification of a crack force driving parameter,(3) Determination of the effects of mechanical properties on crack growth and shape, and(4) Examination of the effects of crack interaction on overall crack growth. The background, procedures, and results of the work done in each of these tasks will be described separately.
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Gray. L51759 Centerline Segregation in Plate and Strip for Linepipe Produced from Continuously Cast Slabs. Chantilly, Virginia: Pipeline Research Council International, Inc. (PRCI), luglio 1996. http://dx.doi.org/10.55274/r0010370.
Testo completoAbstract (sommario):
Segregation in plate and linepipe can have an adverse effect on the mechanical properties, weldability and performance of plate and linepipe. The present study was initiated as a result of field reports concerning incidents of severe chemical segregation in linepipe intended for use offshore. This research was initiated to develop a better understanding of the extent of segregation-related problems and to develop methodologies or tests which could be imposed by purchasers to eliminate future occurrences. The research was undertaken in three separate tasks as follows: Task I Survey of pipeline industry experience, or incidents, involving segregation problems in continuously cast product. Task II Survey of available means for controlling and monitoring of segregation and identification of methods suitable for detailed evaluation. Task III Evaluation and technical assessment of promising segregation monitoring methods identified in Task II. �
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Engel, Bernard, Yael Edan, James Simon, Hanoch Pasternak e Shimon Edelman. Neural Networks for Quality Sorting of Agricultural Produce. United States Department of Agriculture, luglio 1996. http://dx.doi.org/10.32747/1996.7613033.bard.
Testo completoAbstract (sommario):
The objectives of this project were to develop procedures and models, based on neural networks, for quality sorting of agricultural produce. Two research teams, one in Purdue University and the other in Israel, coordinated their research efforts on different aspects of each objective utilizing both melons and tomatoes as case studies. At Purdue: An expert system was developed to measure variances in human grading. Data were acquired from eight sensors: vision, two firmness sensors (destructive and nondestructive), chlorophyll from fluorescence, color sensor, electronic sniffer for odor detection, refractometer and a scale (mass). Data were analyzed and provided input for five classification models. Chlorophyll from fluorescence was found to give the best estimation for ripeness stage while the combination of machine vision and firmness from impact performed best for quality sorting. A new algorithm was developed to estimate and minimize training size for supervised classification. A new criteria was established to choose a training set such that a recurrent auto-associative memory neural network is stabilized. Moreover, this method provides for rapid and accurate updating of the classifier over growing seasons, production environments and cultivars. Different classification approaches (parametric and non-parametric) for grading were examined. Statistical methods were found to be as accurate as neural networks in grading. Classification models by voting did not enhance the classification significantly. A hybrid model that incorporated heuristic rules and either a numerical classifier or neural network was found to be superior in classification accuracy with half the required processing of solely the numerical classifier or neural network. In Israel: A multi-sensing approach utilizing non-destructive sensors was developed. Shape, color, stem identification, surface defects and bruises were measured using a color image processing system. Flavor parameters (sugar, acidity, volatiles) and ripeness were measured using a near-infrared system and an electronic sniffer. Mechanical properties were measured using three sensors: drop impact, resonance frequency and cyclic deformation. Classification algorithms for quality sorting of fruit based on multi-sensory data were developed and implemented. The algorithms included a dynamic artificial neural network, a back propagation neural network and multiple linear regression. Results indicated that classification based on multiple sensors may be applied in real-time sorting and can improve overall classification. Advanced image processing algorithms were developed for shape determination, bruise and stem identification and general color and color homogeneity. An unsupervised method was developed to extract necessary vision features. The primary advantage of the algorithms developed is their ability to learn to determine the visual quality of almost any fruit or vegetable with no need for specific modification and no a-priori knowledge. Moreover, since there is no assumption as to the type of blemish to be characterized, the algorithm is capable of distinguishing between stems and bruises. This enables sorting of fruit without knowing the fruits' orientation. A new algorithm for on-line clustering of data was developed. The algorithm's adaptability is designed to overcome some of the difficulties encountered when incrementally clustering sparse data and preserves information even with memory constraints. Large quantities of data (many images) of high dimensionality (due to multiple sensors) and new information arriving incrementally (a function of the temporal dynamics of any natural process) can now be processed. Furhermore, since the learning is done on-line, it can be implemented in real-time. The methodology developed was tested to determine external quality of tomatoes based on visual information. An improved model for color sorting which is stable and does not require recalibration for each season was developed for color determination. Excellent classification results were obtained for both color and firmness classification. Results indicted that maturity classification can be obtained using a drop-impact and a vision sensor in order to predict the storability and marketing of harvested fruits. In conclusion: We have been able to define quantitatively the critical parameters in the quality sorting and grading of both fresh market cantaloupes and tomatoes. We have been able to accomplish this using nondestructive measurements and in a manner consistent with expert human grading and in accordance with market acceptance. This research constructed and used large databases of both commodities, for comparative evaluation and optimization of expert system, statistical and/or neural network models. The models developed in this research were successfully tested, and should be applicable to a wide range of other fruits and vegetables. These findings are valuable for the development of on-line grading and sorting of agricultural produce through the incorporation of multiple measurement inputs that rapidly define quality in an automated manner, and in a manner consistent with the human graders and inspectors.
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Galili, Naftali, Roger P. Rohrbach, Itzhak Shmulevich, Yoram Fuchs e Giora Zauberman. Non-Destructive Quality Sensing of High-Value Agricultural Commodities Through Response Analysis. United States Department of Agriculture, ottobre 1994. http://dx.doi.org/10.32747/1994.7570549.bard.
Testo completoAbstract (sommario):
The objectives of this project were to develop nondestructive methods for detection of internal properties and firmness of fruits and vegetables. One method was based on a soft piezoelectric film transducer developed in the Technion, for analysis of fruit response to low-energy excitation. The second method was a dot-matrix piezoelectric transducer of North Carolina State University, developed for contact-pressure analysis of fruit during impact. Two research teams, one in Israel and the other in North Carolina, coordinated their research effort according to the specific objectives of the project, to develop and apply the two complementary methods for quality control of agricultural commodities. In Israel: An improved firmness testing system was developed and tested with tropical fruits. The new system included an instrumented fruit-bed of three flexible piezoelectric sensors and miniature electromagnetic hammers, which served as fruit support and low-energy excitation device, respectively. Resonant frequencies were detected for determination of firmness index. Two new acoustic parameters were developed for evaluation of fruit firmness and maturity: a dumping-ratio and a centeroid of the frequency response. Experiments were performed with avocado and mango fruits. The internal damping ratio, which may indicate fruit ripeness, increased monotonically with time, while resonant frequencies and firmness indices decreased with time. Fruit samples were tested daily by destructive penetration test. A fairy high correlation was found in tropical fruits between the penetration force and the new acoustic parameters; a lower correlation was found between this parameter and the conventional firmness index. Improved table-top firmness testing units, Firmalon, with data-logging system and on-line data analysis capacity have been built. The new device was used for the full-scale experiments in the next two years, ahead of the original program and BARD timetable. Close cooperation was initiated with local industry for development of both off-line and on-line sorting and quality control of more agricultural commodities. Firmalon units were produced and operated in major packaging houses in Israel, Belgium and Washington State, on mango and avocado, apples, pears, tomatoes, melons and some other fruits, to gain field experience with the new method. The accumulated experimental data from all these activities is still analyzed, to improve firmness sorting criteria and shelf-life predicting curves for the different fruits. The test program in commercial CA storage facilities in Washington State included seven apple varieties: Fuji, Braeburn, Gala, Granny Smith, Jonagold, Red Delicious, Golden Delicious, and D'Anjou pear variety. FI master-curves could be developed for the Braeburn, Gala, Granny Smith and Jonagold apples. These fruits showed a steady ripening process during the test period. Yet, more work should be conducted to reduce scattering of the data and to determine the confidence limits of the method. Nearly constant FI in Red Delicious and the fluctuations of FI in the Fuji apples should be re-examined. Three sets of experiment were performed with Flandria tomatoes. Despite the complex structure of the tomatoes, the acoustic method could be used for firmness evaluation and to follow the ripening evolution with time. Close agreement was achieved between the auction expert evaluation and that of the nondestructive acoustic test, where firmness index of 4.0 and more indicated grade-A tomatoes. More work is performed to refine the sorting algorithm and to develop a general ripening scale for automatic grading of tomatoes for the fresh fruit market. Galia melons were tested in Israel, in simulated export conditions. It was concluded that the Firmalon is capable of detecting the ripening of melons nondestructively, and sorted out the defective fruits from the export shipment. The cooperation with local industry resulted in development of automatic on-line prototype of the acoustic sensor, that may be incorporated with the export quality control system for melons. More interesting is the development of the remote firmness sensing method for sealed CA cool-rooms, where most of the full-year fruit yield in stored for off-season consumption. Hundreds of ripening monitor systems have been installed in major fruit storage facilities, and being evaluated now by the consumers. If successful, the new method may cause a major change in long-term fruit storage technology. More uses of the acoustic test method have been considered, for monitoring fruit maturity and harvest time, testing fruit samples or each individual fruit when entering the storage facilities, packaging house and auction, and in the supermarket. This approach may result in a full line of equipment for nondestructive quality control of fruits and vegetables, from the orchard or the greenhouse, through the entire sorting, grading and storage process, up to the consumer table. The developed technology offers a tool to determine the maturity of the fruits nondestructively by monitoring their acoustic response to mechanical impulse on the tree. A special device was built and preliminary tested in mango fruit. More development is needed to develop a portable, hand operated sensing method for this purpose. In North Carolina: Analysis method based on an Auto-Regressive (AR) model was developed for detecting the first resonance of fruit from their response to mechanical impulse. The algorithm included a routine that detects the first resonant frequency from as many sensors as possible. Experiments on Red Delicious apples were performed and their firmness was determined. The AR method allowed the detection of the first resonance. The method could be fast enough to be utilized in a real time sorting machine. Yet, further study is needed to look for improvement of the search algorithm of the methods. An impact contact-pressure measurement system and Neural Network (NN) identification method were developed to investigate the relationships between surface pressure distributions on selected fruits and their respective internal textural qualities. A piezoelectric dot-matrix pressure transducer was developed for the purpose of acquiring time-sampled pressure profiles during impact. The acquired data was transferred into a personal computer and accurate visualization of animated data were presented. Preliminary test with 10 apples has been performed. Measurement were made by the contact-pressure transducer in two different positions. Complementary measurements were made on the same apples by using the Firmalon and Magness Taylor (MT) testers. Three-layer neural network was designed. 2/3 of the contact-pressure data were used as training input data and corresponding MT data as training target data. The remaining data were used as NN checking data. Six samples randomly chosen from the ten measured samples and their corresponding Firmalon values were used as the NN training and target data, respectively. The remaining four samples' data were input to the NN. The NN results consistent with the Firmness Tester values. So, if more training data would be obtained, the output should be more accurate. In addition, the Firmness Tester values do not consistent with MT firmness tester values. The NN method developed in this study appears to be a useful tool to emulate the MT Firmness test results without destroying the apple samples. To get more accurate estimation of MT firmness a much larger training data set is required. When the larger sensitive area of the pressure sensor being developed in this project becomes available, the entire contact 'shape' will provide additional information and the neural network results would be more accurate. It has been shown that the impact information can be utilized in the determination of internal quality factors of fruit. Until now,
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Noise Absorption Behavior of Aluminum Honeycomb Composite. SAE International, settembre 2020. http://dx.doi.org/10.4271/2020-28-0453.
Testo completoAbstract (sommario):
Natural fibers are one of the major ways to improve environmental pollution. In this study experimental investigation and simulation of honeycomb filled with cotton fabric, wood dust and polyurethane were carried out. This study determines the potential use of cotton fabric, wood dust as good sound absorbers. Automotive industries are looking forward to materials that have good acoustic properties, lightweight, strong and economical. This study provides a better understanding of sound-absorbing material with other mechanical properties. With simulation and experimental results, validation of works provides a wider industrial application for the interior of automotive industries including marine, aviation, railway industry and many more.