Дисертації з теми "Cohesive-frictional"
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Addetta, Gian Antonio d'. "Discrete models for cohesive frictional materials." Stuttgart Inst. für Baustatik, 2004. http://deposit.d-nb.de/cgi-bin/dokserv?idn=972184996.
Повний текст джерелаBeadle, Michael E. "Settlement induced by tunnelling in cohesive-frictional soils." Thesis, National Library of Canada = Bibliothèque nationale du Canada, 1997. http://www.collectionscanada.ca/obj/s4/f2/dsk2/ftp04/mq21081.pdf.
Повний текст джерелаBard, Romain (Romain M. ). "Analysis of the scratch test for cohesive-frictional materials." Thesis, Massachusetts Institute of Technology, 2010. http://hdl.handle.net/1721.1/61521.
Повний текст джерелаThis electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.
Cataloged from student-submitted PDF version of thesis.
Includes bibliographical references (p. 143-148).
In this thesis we develop analytical solutions for the relations between scratch hardness and strength properties of cohesive-frictional materials of the Mohr-Coulomb and Drucker-Prager type. Based on the lower-bound yield design approach, closed form solutions are derived for frictionless scratch devices, and validated against computational upper bound and elastoplastic Finite Element solutions. The influence of friction at the blade{material interface is also investigated, for which a simple computational optimization is proposed. The model is extended to porous cohesive-frictional materials through the use of a homogenized strength criterion based on the Linear Comparison Composite theory. Relations between scratch hardness, porosity and strength properties are proposed in the form of fitted functions. Illustrated for scratch tests on cement paste, we show that the proposed solutions provide a convenient way to determine estimates of cohesion and friction parameters from scratch data, and may serve as a benchmark to identify the relevance of strength models for scratch test analysis.
by Romain Bard.
S.M.
Kwok, Leung Cheung. "A study of cohesive-frictional soils under dynamic loading." Thesis, University of Aberdeen, 2013. http://digitool.abdn.ac.uk:80/webclient/DeliveryManager?pid=201916.
Повний текст джерелаGanneau, Francois P. 1979. "From nanohardness to strength properties of cohesive-frictional materials : application to shale materials." Thesis, Massachusetts Institute of Technology, 2004. http://hdl.handle.net/1721.1/28626.
Повний текст джерелаIncludes bibliographical references (p. 213-221).
Advanced experimental and theoretical micromechanics such as nanoindentation makes it possible today to break down highly heterogeneous materials to the scale where physical chemistry meets (continuum) mechanics, to extract intrinsic material properties that do not change from one material to another, and to upscale the intrinsic material behavior from the sub-microscale to the macroscale. While well established for elastic properties, the extraction of strength properties of cohesive-frictional materials from nanoindentation tests has not been investigated in the same depth. The focus of this thesis is to investigate in depth the link between nanohardness of cohesive-frictional materials and strength properties. To address our objectives, we develop a rational methodology based on limit analysis theorems and implement this methodology in a finite element, based computational environment. By applying this technique to indentation analysis, we show that it is possible to extract the cohesion and the friction angle from two conical indentation tests having different apex angles. The methodology is validated on a model cohesive-frictional material, bulk metallic glass, and a first application to a highly heterogeneous natural composite material, shale materials, is shown. The results are important in particular for the Oil and Gas industry, for which the reduced strength properties (cohesion and friction angle) are critical for the success of drilling operations.
by Francois P. Ganneau.
S.M.
Cariou, Sophie S. M. Massachusetts Institute of Technology. "The effect of the packing density on the indentation hardness of cohesive-frictional porous materials." Thesis, Massachusetts Institute of Technology, 2006. http://hdl.handle.net/1721.1/35494.
Повний текст джерелаIncludes bibliographical references (p. 170-178).
Natural composites in general and sedimentary rocks in particular are highly heterogeneous materials which defy a straightforward implementation of the materials science paradigm of microstructure-properties-performance correlation. The application of nanoindentation to natural composites has provided the geomechanics community with a new versatile tool to test in situ phase properties and structures of geomaterials that cannot be recapitulated ex situ in bulk form. But it requires a rigorous indentation analysis to translate indentation data into meaningful mechanical properties. The development and implementation of such an indentation analysis for the strength properties of cohesive-frictional porous materials is the focus of this thesis. We report the development and implementation of a multi-scale indentation analysis based on limit analysis, which makes it possible to infer from an experimental hardness value and the solid's packing density the strength properties of the cohesive-frictional porous material.
(cont.) Making use of most recent advances in non-linear strength homogenization theory, we implement a homogenized cohesive Cam-Clay type elliptical strength criterion which takes into account the strength properties of the constituents (cohesion and friction), the porosity and the microstructure, into a yield design approach to indentation analysis. Making use of the strong duality of the lower and upper bound theorem, we identify the resulting upper bound problem as a Second-Order Conical optimization problem, for which advanced solvers such as MOSEK became recently available. The originality of our approach lies in the combination of finite element discretization and advanced optimization techniques, which is readily implemented in standard tools of computational mechanics, such as MATLAB. The upper bound yield design solutions are benchmarked against solutions from comprehensive elastoplastic contact mechanics finite element solutions and compared with lower bound solutions, which all show an excellent agreement.
(cont.) Furthermore, from a detailed parameter study based on intensive computational simulations, we show that it is possible to condense the indentation hardness-material properties relation of cohesive-frictional porous materials into a single hardness-packing density scaling relation. On this basis, it is possible to use the hardness-packing density scaling relation for reverse analysis of the strength parameters of cohesive-frictional solids from indentation. The procedure is illustrated for shale materials. From hardness values of six shale materials of different packing density and mineralogy, we deduce that the clay fabric in highly compacted shales is most likely a purely cohesive (friction-less) nano-granular material, having a uniaxial strength of roughly 440 MPa.
by Sophie Cariou.
S.M.
Addetta, Gian Antonio d' [Verfasser]. "Discrete models for cohesive frictional materials / Institut für Baustatik der Universität Stuttgart. Von Gian Antonio D'Addetta." Stuttgart : Inst. für Baustatik, 2004. http://d-nb.info/972184996/34.
Повний текст джерелаSfantos, Georgios. "Boundary element methods for cohesive-frictional non linear problems : applications to wear, contact and multi-scale damage modelling." Thesis, Imperial College London, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.439265.
Повний текст джерелаKim, Sungchul. "On the mechanics of strain localization in plasticity : isotropic and orthotropic, cohesive and frictional, associated and non-associated models." Doctoral thesis, Universitat Politècnica de Catalunya, 2021. http://hdl.handle.net/10803/672321.
Повний текст джерелаEn esta tesis trata dos temas principales: la mecánica de la localización de deformaciones en plasticidad y el funcionamiento de varios elementos finitos mixtos sometidos a la localización de deformaciones plásticas. A lo largo de la tesis, se estudian sólidos incompresibles y cohesivo-friccionales, isotrópos y ortótropos, elasto- y rígidos-plásticos, utilizando reglas de flujo asociadas o no asociadas, tanto a en formato continuo como discreto. En un análisis detallado del proceso de localización de la deformación, se identifican los puntos de plastificación, bifurcación y localización de la deformación. Se presentan los mecanismos de la localización de deformaciones a nivel continuo y discreto, incluyendo las relaciones constitutivas, la cinemática de las discontinuidades fuertes y débiles y las condiciones de localización de la deformación. Se explican la condición cinemática de Maxwell, la condición de continuidad del incremento de tracción y la condición acotabilidad del incremento de la tensión, su relevancia en la bifurcación de la deformación y las condiciones de localización de la deformación. Se propone y se verifica numéricamente mediante simulaciones independientes la predicción analítica de la localización de la deformación a partir de la condición de acotabilidad de la tensión. A diferencia de lo que predice en el análisis clásico de localización de deformaciones, ésta es independiente del comportamiento elástico y está únicamente relacionada con el flujo plástico. Específicamente, el ángulo de localización de la deformación depende del estado de la tensión y del potencial plástico, pero no de las constantes elásticas ni de la superficie de fluencia. Se realizan experimentos computacionales en placas sometidas a tracción y compresión uniaxial en tensión y deformación plana para evaluar el análisis teórico, así como en tests de punzonamiento de Prandtl. Los resultados numéricos con plasticidad incompresible y cohesivo-friccional, isotrópa y ortotrópica, asociada y no asociada, con o sin ángulos de inclinación entre los ejes locales materiales y los ejes globales proporcionan evidencias convincentes para el marco teórico propuesto. En esta tesis se utilizan varios elementos finitos mixtos. Al comparar los resultados numéricos, se muestran las ventajas y desventajas del funcionamiento de varios elementos finitos mixtos con respecto a su precisión, la eficiencia computacional, la sensibilidad respecto a la alineación de la malla y el bloqueo de tensiones.
Enginyeria civil
Socié, Adrien. "Modélisation chimio-mécanique de la fissuration de matériaux cimentaires : vieillissement et tenue des enceintes de confinement des centrales nucléaires." Thesis, Montpellier, 2019. http://www.theses.fr/2019MONTS102.
Повний текст джерелаThe French "Institut de Radioprotection et de Sûreté Nucléaire" (IRSN) conducts researches on the impact of internal swellings reactions on concrete, such as Sulfate Reactions. Such reactions are characterized by the precipitation of ettringite which induces swellings and cracks by differential strain. These cracks are preferential location for ions diffusion and further ettringite precipitations.The aim of the study is to model the degradation of a mature material by ettringite pressure at the aggregate scale.A chemo-mechanical model based on a coupling between reactive transport (species diffusion and chemical reactions) and mechanics in cracked porous medium is developed and is solved with a generic staggered approach.The initial microstructure and poro-mechanical and diffusion parameters are estimated by hydration computing and analytical homogenization.The coupled chemo-mechanical model is validated and then applied to Sulfate External and Internal Attack.The impact of the concrete composition and the chemical environments on the swelling kinetics and crack path is taken into account. Furthermore, our simulations highlight the influences of inclusions and cracks on the inhomogeneous spatial distribution of precipitation areas of ettringite and associated swelling stress
Venzal, Vincent. "Modélisation discrète du comportement mécanique desouvrages maçonnés en pierre. Aspects expérimentaux - Analyse énergétique." Thesis, Bordeaux, 2020. http://www.theses.fr/2020BORD0017.
Повний текст джерелаThis work aims to develop a design code suitable for structural masonry design. Discrete element code LMGC90 is chosen as basis of the design code for its capacity to consider masonry discontinuities. A general frictional cohesive zone model (FCZM) is proposed to describe the progressive damage and the release of energy due to the quasi-brittle behavior of materials and to the friction of the interface stone-mortar. Under combined traction and shear loadings, a mixed-mode response based on pure Mode I and Mode II cohesive behaviors is proposed. Under combined compression and shear loadings, a coupling between Mode II cohesive behavior and frictional behavior based on the damage level is proposed and leads to a progressive rising of the frictional stress associated with the softening part of the cohesive behavior of the interface. On this basis, cohesive and frictional parameters of the FCZM are estimated from two characterization tests (direct tensile and direct shear) carried out on samples of limestone blocks assembled by lime mortar joint. A general validation is proposed at the scale of a masonry wall submitted to a shear fracture test under constant vertical load. The confrontation of experimental and simulated responses provides a large validation basis because all the loading modes considered in FCZM are present in the wall during the shear test. If the static of the experimental responses is well described by the model using the parameters resulting from the characterization tests, the kinematic of the responses needs calibrating the elastic properties of the stone blocks and degrading the cohesive properties of the interfaces through a uniform initial damage field. On this basis, the use of a nonuniform initial damage field allows matching the experimental variability observed in the location and chronology of the fracture mechanisms of tested walls
Wallin, Harald. "An investigation of friction graphs ranking ability regarding the galling phenomenon in dry SOFS contact : (Adhesive material transfere and friction)." Thesis, Karlstad University, Faculty of Technology and Science, 2008. http://urn.kb.se/resolve?urn=urn:nbn:se:kau:diva-2790.
Повний текст джерелаThe main purpose of this project is to investigate different tool steels in terms of their ability to withstand material transfer buildup, so-called galling, occurring in SMF (sheet metal forming) operations. The ability to withstand galling is vital to optimize cost-effectiveness and increase the work tool’s effective operational time. This investigation studies four different tool steels, including a TiN-coating, with the intention of evaluating the microstructures, chemical composition and hardness effect on galling resistance in dry conditions using a slider-on-flatsurface (SOFS) tribo-tester which measures the coefficient of friction during sliding.
An OP (optical profilometer) was used to measure the size and geometry of lump growth on the tool and damage on the work sheet. A scanning electron microscope (SEM) was used to identify the interacting tribological mechanisms exhibited at different stages during the slide. The SEM figures confirmed three different types of characteristic patterns exhibited in the tracks after tribo- testing which were categorized as mild adhesive, abrasive and severe adhesive damage.
A SEM figure that illustrates a ragged contact surface and an obvious change in the sheet materials plastic behavior is in this report regarded as a sign of severe adhesive contact, the characteristics could possibly be explained by local high temperature and high pressure followed by a sudden pressure drop and creation of hardened welds or solders between the two surfaces which increase the frictional input needed for further advancement. Friction coefficients observed in the initial 100% mild adhesive stage were, μ=0,22-0,26 succeeded by abrasive SEM characteristics often in association with mild adhesive contact and friction values between μ=0,25-0,4 which where sometimes followed by severe adhesive SEM characteristics in 100% of the contact zone with friction values between μ=0,34- 0,9 respectively. The tool material that performed best according to the friction detection criteria was Sv21 closely followed by Sleipner (TiN coated) and Va40 (HRC 63.3). Unfortunately was the friction criteria, a significant raise in friction for defining a sliding length to galling, not adequate for dry conditions due to immediate material transfer succeeded by cyclic changes between partial or 100% abrasive+mild adhesive and severe adhesive contact. The mechanism that change abrasive wear in association with mild adhesive contact, (moderate friction input), to sever adhesive wear, (higher friction input), is dependent on lump shape (lump geometry) and can appear at comparably low speeds 0,04-0,08 [m/s] and low friction energy input (μ=0,34), the magnitude of the change in friction is therefore not always significant and hardly detectable on the friction graph. This was quite unexpected but could be explained by concentration of friction energy rater than the absolute amount. The problem with using friction graphs for galling evaluation was increased even further when a very small lump size and low corresponding rate of material transfer to the tool surface caused a sustainable high raise in friction (μ≈0,3→0,6) on a TiN-coated tool steel called Sleipner.
A hardly detectable or similar friction raise for Sv21 and Va40 showed much larger corresponding lump size and rate of material transfer. This means that friction graphs demonstrate a clear problem with quantifying lump size [m3] and rate of material transfer [m3/s]. Another phenomenon called stick slip behavior, material transfer and lump growth followed by a sudden decrease in lump size and transfer of material back to the work sheet, is also not possible to detect on a friction graph. Because a drop in friction can easily be a change in contact temperature and lump attack angle due to a growing lump and not a decreasing lump.
The conclusion, a friction graph is not suited for galling evaluation and ranking in dry SOFS conditions. A ranking should primarily be based on dimensional OP measurements of the cross section of formed tracks and scratches or preferably by repeated OP measurements of the tool surface during a single test, the last revel the exact lump growth history and true lump growth even in the sliding direction.
civilingenjörsexamen
Shing, Liao Shin, and 廖新興. "Frictional Properties of Drilled Pile in Cohesive Soil." Thesis, 1995. http://ndltd.ncl.edu.tw/handle/16478092678343944398.
Повний текст джерела國立中央大學
土木工程研究所
83
This study carried out direct shear tests and simple shear tests to investigate the frictional properties of the pile-soil interface and to obtain the relationships among the shear stress, the sliding displacement at interface and the shear strain in soil. The theory of nonlinear elasticity was used to analyze the shear deformation of the soil around pile shaft. The proposed the method based on these tests and the theoretical analysis is used to predict the frictional behavior of pile shaft. The results of the analysis show that the relationship between the displacement and the frictional force predicted by the proposed method is consistence with those obtained from the triaxial model pile tests, the tank model pile tests and the pile load test. The results of frictional test show that the total displacement in prefailure stage includes the sliding displacement at interface and the shear deformation in soil. After the failure of the pile-soil interface, the variation of total displacement is come from sliding displacement. Before the failure, the dependency of the shear strain in soil on the friction ratio at the interface is the same as the one on the friction ratio in the soil. It can be find that there is little influence of the diameter of pile on the frictional resistance of shaft in triaxial and tank model tests. Howere, the displacement of pile at failure is increase with the increase of the diameter.
Kandasami, Ramesh Kannan. "Experimental Studies on The Mechanical Behaviour of Cohesive Frictional Granular Materials." Thesis, 2016. http://etd.iisc.ernet.in/handle/2005/2680.
Повний текст джерелаWulandari, Safitri Nur, and Safitri Nur Wulandari. "Stability Charts for Footing on Cohesive-Frictional Slopes Subjected to Pore-Water Pressure by Limit Analysis Method." Thesis, 2019. http://ndltd.ncl.edu.tw/handle/n89fpm.
Повний текст джерела國立臺灣科技大學
營建工程系
107
In the region there was generally influenced by seasonal weather such as highly rainfall intensity, increasing or decreasing water levels may trigger the changing of failure surface and factor of safety on slopes. Reducing the factor of safety causes the slope failure potential increases. It was indicated by the increase of pore water pressure, therefore the shear strength reduced and shear stress enhanced. The uncertain intensity in every rainfall period causes the water level change needs to be evaluated conscientiously to prevent the slope failures. This study primarily aims to investigate the failure mechanisms and factor of safety that are resulted as an impact of pore-water pressure differences by varying the water level, slope angle, soil strength parameters, and slope height with footing and without footing. In addition, cohesive-frictional soils are concerned in this study because this soil condition is commonly found in practice. Limit analysis as one of the rigorous stability analysis methods is used in this study to predict the slope failure mechanism and factor of safety by using two dimensional (2D) numerical approach. The plastic zone will be observed as well in this study as none studies explained it clearly. Latter, the stability charts are also produced for preliminary assessment by practical engineers
Le, Linh Anh. "A Mechanism-based Approach to Constitutive Modelling of Quasi-Brittle Geomaterials with and without Fibre Reinforcement." Thesis, 2019. http://hdl.handle.net/2440/119898.
Повний текст джерелаThesis (Ph.D.) -- University of Adelaide, School of Civil, Environmental and Mining Engineering, 2019
Karparov, Krassimir Nikolov. "Slope stability analyses in complex Geotechnical conditions – Thurst failure mechanism." Thesis, 2007. http://hdl.handle.net/2263/23040.
Повний текст джерелаThesis (PhD(Mining Engineering))--University of Pretoria, 2007.
Mining Engineering
unrestricted