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Дисертації з теми "Thin-walled element of detail"

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Автор: Grafiati
Опубліковано: 30 травня 2022
Оновлено: 31 травня 2022

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1

Козлова, Елена Борисовна. "Подавление регенеративных автоколебаний при фрезеровании тонкостенного элемента детали концевыми цилиндрическими фрезами". Thesis, Запорожский национальный технический университет, 2016. http://repository.kpi.kharkov.ua/handle/KhPI-Press/25652.

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Анотація:
Диссертация на соискание ученой степени кандидата технических наук по специальности 05.03.01 – процессы механической обработки, станки и инструменты. Национальный технический университет "Харьковский политехнический институт", Харьков, 2016. Диссертационная работа посвящена выявлению основных закономерностей влияния косоугольности и разнонаклонности зубьев концевой цилиндрической фрезы на повышение ее виброустойчивости и качество обработанной поверхности при фрезеровании тонкостенного элемента детали. Показано, что при изучении динамики процессов резания необходимо учитывать не только силы резания, но и силы упругости, демпфирования и инерционные силы, а также собственные частоты колебаний как инструмента, так и обрабатываемой детали. Конструкция измерительного стенда и система оценивания результатов позволяют определять закон движения тонкостенного элемента детали под действием всех видов сил. Разработанная конструкция 4–зубой экспериментальной концевой цилиндрической фрезы с регулируемым углом наклона каждого зуба позволила определить влияние косоугольности и разнонаклонности зубьев на вибрационные процессы, возбуждаемые при фрезеровании. Проведены исследования по определению влияния цилиндрической и плоской ленточки на задней поверхности зуба на подавление регенеративных автоколебаний. Установлено, что плоская ленточка на задней поверхности оказывает существенное положительное влияние на снижение параметра размаха автоколебаний R2. Механизм подавления автоколебаний в данном случае связан с изменением условий трения между задней поверхностью зуба фрезы и поверхностью резания. В работе приведены результаты сравнительных исследований по одновременному влиянию на подавление автоколебаний применения фрез с разнонаклонными режущими зубьями, у которых на задней поверхности заточена плоская ленточка. Заточка ленточки на задней поверхности разнонаклонных зубьев позволяет дополнительно уменьшить размах автоколебаний. При высоких скоростях фрезерования, когда автоколебания вырождаются, применение фрез с разнонаклонными зубьями не эффективно.
The thesis for the degree of candidate of technical sciences, specialty 05.03.01 – machining processes, machines and tools. National Technical University "Kharkiv Polytechnic Institute", Kharkiv, 2016. The thesis is sanctified to the exposure of basic conformities to law of influence of oblique–angledness and differently inclined points of end–capping cylindrical milling cutter on the increase of her vibration stability and quality of a treat surface at milling of the thin–walled element of detail. Construction of measuring stand and system of evaluation of results, and also the worked out construction of experimental end–capping cylindrical milling cutter with the managed angle of slope of every tooth allowed to define influence of oblique–angledness and differently inclined points on the oscillation processes excited at milling. On results the conducted experiments qualificatory correlation is set forth distinguished speed zones of vibrations of the thin–walled element of detail. It is set that increase of angle of slope of cutting edge w from 30° to 45° promotes vibrofirmness of process of the cylindrical milling. The turn of axis of rotation of milling cutter positively influences on the regenerative oscillation damping and reduces the parameter Ra of rejection of profile of a treat surface. A flat ribbon on a back surface renders substantial influence on the decline of parameter of scope of self–excited oscillations R2. Sharpening of ribbon on the back surface of differently inclined points allows additionally to decrease the scope of self–excited oscillations. At high–speeds of milling, when self–excited oscillations degenerate, application of milling cutters with differently inclined points is not effective.
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2

Козлова, Олена Борисівна. "Пригнічення регенеративних автоколивань при фрезеруванні тонкостінного елемента деталі кінцевими циліндричними фрезами". Thesis, НТУ "ХПІ", 2016. http://repository.kpi.kharkov.ua/handle/KhPI-Press/25648.

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Анотація:
Дисертація на здобуття наукового ступеня кандидата технічних наук за спеціальністю 05.03.01 – процеси механічної обробки, верстати та інструменти. Національний технічний університет "Харківський політехнічний інститут", Харків, 2016. Дисертаційну роботу присвячено виявленню основних закономірностей впливу косокутності і різнонахиленості зубів кінцевої циліндричної фрези на підвищення її вібростійкості і якість обробленої поверхні при фрезеруванні тонкостінного елемента деталі. Конструкція вимірювального стенду та система оцінювання результатів, а також розроблена конструкція 4–зубої експериментальної кінцевої циліндричної фрези з можливістю регулювання кута нахилу кожного зуба, дозволили визначити вплив косокутності і різнонахиленості зубів на вібраційні процеси, які збуджуються при фрезеруванні. За результатами проведених експериментів сформульовано визначальне співвідношення і виділені IV швидкісні зони коливань тонкостінного елемента деталі. Встановлено, що кут нахилу ріжучої кромки w від 30° до 45° найбільше підвищує вібростійкість процесу циліндричного фрезерування. Поворот осі обертання фрези позитивно впливає на демпфування регенеративних втоколивань і знижує параметр Ra відхилення профілю обробленої поверхні. Експериментально підтверджено, що максимальний ефект від різнонахиленості сусідніх зубів досягається при невеликих кутах Dw від 3° до 6° в умовах порушення регенеративних автоколивань. Плоска стрічка на задній поверхні має суттєвий позитивний вплив на зниження параметра розмаху автоколивань R2. Заточування стрічки на задній поверхні різнонахилених зубів дозволяє додатково зменшити розмах автоколивань. При високих швидкостях фрезерування, коли автоколивання вироджуються, застосування фрез з різнонахиленими зубами неефективне.
The thesis for the degree of candidate of technical sciences, specialty 05.03.01 – machining processes, machines and tools. National Technical University "Kharkiv Polytechnic Institute", Kharkiv, 2016. The thesis is sanctified to the exposure of basic conformities to law of influence of oblique–angledness and differently inclined points of end–capping cylindrical milling cutter on the increase of her vibration stability and quality of a treat surface at milling of the thin–walled element of detail. Construction of measuring stand and system of evaluation of results, and also the worked out construction of experimental end–capping cylindrical milling cutter with the managed angle of slope of every tooth allowed to define influence of oblique–angledness and differently inclined points on the oscillation processes excited at milling. On results the conducted experiments qualificatory correlation is set forth distinguished speed zones of vibrations of the thin–walled element of detail. It is set that increase of angle of slope of cutting edge w from 30° to 45° promotes vibrofirmness of process of the cylindrical milling. The turn of axis of rotation of milling cutter positively influences on the regenerative oscillation damping and reduces the parameter Ra of rejection of profile of a treat surface. A flat ribbon on a back surface renders substantial influence on the decline of parameter of scope of self–excited oscillations R2. Sharpening of ribbon on the back surface of differently inclined points allows additionally to decrease the scope of self–excited oscillations. At high–speeds of milling, when self–excited oscillations degenerate, application of milling cutters with differently inclined points is not effective.
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3

Nemir, M. T. M. "Finite element stability analysis of thin-walled steel structures." Thesis, University of Salford, 1985. http://usir.salford.ac.uk/2219/.

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Анотація:
Recent applications in the use of light gauge steel members have been concerned with developing large scale systems built entirely from cold-formed steel members. An explicit analysis of such structures is complicated by the different phenomena that the structure may be prone to during loading. In particular, elastic buckling phenomena is an important consideration in the design of such structures since the load at which buckling occurs often provides a close upper bound to the carrying capacity of the structure. The first part of this two-part thesis (Part I, Chaptersl-8) has been devoted to general methods of analysis of the torsional-flexural buckling of thin-walled structures. A review of previous investigations and the available methods of solution is presented. A general finite element formulation of the torsional-flexural buckling of thin-walled structures has been derived. The resulting elastic geometric matrix can be used to analyse structures with monosymmetrical members. It also includes the effect of sectorial-monosymmetry for cross-sections without any axis of symmetry. A general transformation matrix has been developed to allow for the application of the finite element method to the three-dimensional elastic stability analysis of space and portal frames. The validity and accuracy of the new finite element formulation have been checked by analysing a number of different elastic lateral buckling problems for which exact or highly accurate solutions by other techniques are available. An experimental program was carried out on simply supported cold-formed steel z-beams. The first part of this program was undertaken to check the validity of the finite element calculations of the bimoments caused by nonuniform torsion. The second part was devoted to elastic lateral buckling of z-beams under combined bending and torsion. The second part of this thesis (Part II, Chapter 9) deals with the analysis of hipped roof structures with corrugated steel roof sheeting. A simple theoretical model has been suggested. The model has been used to perform an elastic linear analysis of the behaviour of two types of the hipped roof structures. The theoretical results are compared with previous experimental results for these two structures.
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4

Lentz, W. Karl. "Optimum coupling in thin-walled, closed section composite beams." Diss., Georgia Institute of Technology, 1997. http://hdl.handle.net/1853/12018.

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5

Liang, Ce. "Analysis of crashworthiness of the dimpled thin-walled structures." Thesis, University of Sussex, 2018. http://sro.sussex.ac.uk/id/eprint/78870/.

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Thin-walled structures are often used as kinetic energy absorbers in vehicular systems and infrastructure designs. In such applications, high specific energy absorption is usually desirable, because it is beneficial for weight reduction. The dimpling cold-roll metal forming process introduces dimpled geometry and increases the strength of sheet metal. This thesis aims to investigate the energy absorption characteristics of the dimpled thin-walled structures. A finite element (FE) modelling analysis was performed using ANSYS Explicit Dynamics solver, to predict the response of dimpled structures to dynamic and quasi-static loads. A series of experimental tests were conducted and the FE method was validated through comparing the numerical and experimental results. To understand the response of the dimpled structural components to axial crushing loads, numerical simulations were performed. A parametric study on a key cold-roll forming parameter “forming depth” was carried out to evaluate its effects on the dimpled geometry and material properties. Through the parametric study, manufacturing parameters for the cold-roll forming process were suggested to improve yield strength and energy absorption performance of dimpled steel components. It was shown that the specific energy absorption can be increased by up to 16% after optimizing the forming depth. To take the most advantage of the dimpled geometry, multi-layer dimpled thin-walled columns were analysed. The interlocking mechanism of dimpled plates were investigated and an empirical model was proposed to describe the interaction between dimpled plates. It was shown that a considerable amount of energy can be absorbed through the interaction between dimpled walls. The behaviour of dimpled columns under lateral impact loads was also investigated. It was revealed that the introduced dimpled geometry contributes to reducing the peak impact force without sacrificing the energy absorption capacity. However, this is only valid when at least one end of the dimpled thin-walled column is fully restrained.
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6

Oldenburg, Mats. "Finite element analysis of thin-walled structures subjected to impact loading." Doctoral thesis, Luleå, 1988. http://epubl.luth.se/avslutade/0348-8373/69/index.html.

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7

Li, F. "Impact of thin walled shell structures using a simplified finite element model." Thesis, Imperial College London, 1987. http://hdl.handle.net/10044/1/47104.

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8

Harursampath, Dineshkumar. "Non-classical non-linear effects in thin-walled composite beams." Diss., Georgia Institute of Technology, 1998. http://hdl.handle.net/1853/12501.

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9

Mohammed, Ali Hjaji. "Steady State Response of Thin-walled Members Under Harmonic Forces." Thèse, Université d'Ottawa / University of Ottawa, 2013. http://hdl.handle.net/10393/24013.

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The steady state response of thin-walled members subjected to harmonic forces is investigated in the present study. The governing differential equations of motion and associated boundary conditions are derived from the Hamilton variational principle. The harmonic form of the applied forces is exploited to eliminate the need to discretize the problem in the time domain, resulting in computational efficiency. The formulation is based on a generalization of the Timoshenko-Vlasov beam theory and accounts for warping effects, shear deformation effects due to bending and non-uniform warping, translational and rotary inertial effects and captures flexural-torsional coupling arising in asymmetric cross-sections. Six of the resulting seven field equations are observed to be fully coupled for asymmetric cross-sections while the equation of longitudinal motion is observed to be uncoupled. Separate closed form solutions are provided for the cases of (i) doubly symmetric cross sections, (ii) monosymmetric cross-sections, and (iii) asymmetric cross-sections. The closed-form solutions are provided for cantilever and simply-supported boundary conditions. A family of shape functions is then developed based on the exact solution of the homogeneous field equations and then used to formulate a series of super-convergent finite beam elements. The resulting two-noded beam elements are shown to successfully capture the static and dynamic responses of thin-walled members. The finite elements developed involve no special discretization errors normally encountered in other finite element formulations and provide results in excellent agreement with those based on other established finite elements with a minimal number of degrees of freedom. The formulation is also capable to predict the natural frequencies and mode-shapes of the structural members. Comparisons with non-shear deformable beam solutions demonstrate the importance of shear deformation effects within short-span members subjected to harmonic loads with higher exciting frequencies. Comparisons with shell element solution results demonstrate that distortional effects are more pronounced in cantilevers with short spans. A generalized stress extraction scheme from the finite element formulation is then developed. Also, a generalization of the analysis procedure to accommodate multiple loads with distinct exciting frequencies is established. The study is concluded with design examples which illustrate the applicability of the formulation, in conjunction with established principles of fatigue design, in determining the fatigue life of steel members subjected to multiple harmonic forces.
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10

Akman, Mehmet Nazim. "Analysis Of Thin Walled Open Section Tapered Beams Using Hybrid Stress Finite Element Method." Master's thesis, METU, 2008. http://etd.lib.metu.edu.tr/upload/2/12609246/index.pdf.

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In this thesis, hybrid stress finite element is formulated for the analysis of the isotropic, thin walled, open section beams with variable cross sections. The beam element has two nodes each having seven degrees of freedom. Assumption of stress field is sufficient to determine the element stiffness matrix. Axial, flexural and torsional effects are taken into account in the analysis. The methodology can be applied both to the tapered and the uniform beams. Throughout this study, firstly element cross-sectional properties are computed using the flow analogy of the inter-connected elements which may have different thicknesses. Then another computer program calculates the displacements and stresses at the nodes along the beam. The results obtained are compared to the results taken from literature and commercial FEM program Nastran.
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11

Dempsey, James F. "The finite element analysis of apex thin and thick walled hexagonal drive tool sockets." Ohio : Ohio University, 1992. http://www.ohiolink.edu/etd/view.cgi?ohiou1172248289.

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12

Ghose, Dhrubajyoti. "Finite element formulation of a thin-walled beam with improved response to warping restraint." Thesis, This resource online, 1991. http://scholar.lib.vt.edu/theses/available/etd-12052009-020042/.

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13

Johansson, Robert. "Finite element modeling of straightening of thin-walled seamless tubes of austenitic stainless steel." Thesis, Högskolan Dalarna, Materialteknik, 2016. http://urn.kb.se/resolve?urn=urn:nbn:se:du-21463.

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During this thesis work a coupled thermo-mechanical finite element model (FEM) was builtto simulate hot rolling in the blooming mill at Sandvik Materials Technology (SMT) inSandviken. The blooming mill is the first in a long line of processes that continuously or ingotcast ingots are subjected to before becoming finished products. The aim of this thesis work was twofold. The first was to create a parameterized finiteelement (FE) model of the blooming mill. The commercial FE software package MSCMarc/Mentat was used to create this model and the programing language Python was used toparameterize it. Second, two different pass schedules (A and B) were studied and comparedusing the model. The two pass series were evaluated with focus on their ability to healcentreline porosity, i.e. to close voids in the centre of the ingot. This evaluation was made by studying the hydrostatic stress (σm), the von Mises stress (σeq)and the plastic strain (εp) in the centre of the ingot. From these parameters the stress triaxiality(Tx) and the hydrostatic integration parameter (Gm) were calculated for each pass in bothseries using two different transportation times (30 and 150 s) from the furnace. The relationbetween Gm and an analytical parameter (Δ) was also studied. This parameter is the ratiobetween the mean height of the ingot and the contact length between the rolls and the ingot,which is useful as a rule of thumb to determine the homogeneity or penetration of strain for aspecific pass. The pass series designed with fewer passes (B), many with greater reduction, was shown toachieve better void closure theoretically. It was also shown that a temperature gradient, whichis the result of a longer holding time between the furnace and the blooming mill leads toimproved void closure.
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14

Saadé, Katy. "Finite element modeling of shear in thin walled beams with a single warping function." Doctoral thesis, Universite Libre de Bruxelles, 2005. http://hdl.handle.net/2013/ULB-DIPOT:oai:dipot.ulb.ac.be:2013/211043.

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Анотація:
The considerable progress in the research and development of thin-walled beam structures responds to their growing use in engineering construction and to their increased need for efficiency in strength and cost. The result is a structure that exhibits large shear strains and important non uniform warping under different loadings, such as non uniform torsion, shear bending and distortion.

A unified approach is formulated in this thesis for 3D thin walled beam structures with arbitrary profile geometries, loading cases and boundary conditions. A single warping function, defined by a linear combination of longitudinal displacements at cross sectional nodes (derived from Prokic work), is enhanced and adapted in order to qualitatively and quantitatively reflect and capture the nature of a widest possible range of behaviors. Constraints are prescribed at the kinematics level in order to enable the study of arbitrary cross sections for general loading. This approach, differing from most published theories, has the advantage of enabling the study of arbitrary cross sections (closed/opened or mixed) without any restrictions or distinctions related to the geometry of the profile. It generates automatic data and characteristic computations from a kinematical discretization prescribed by the profile geometry. The amount of shear bending, torsional and distortional warping and the magnitude of the shear correction factor is computed for arbitrary profile geometries with this single formulation.

The proposed formulation is compared to existing theories with respect to the main assumptions and restrictions. The variation of the location of the torsional center, distortional centers and distortional rotational ratio of a profile is discussed in terms of their dependency on the loading cases and on the boundary conditions.

A 3D beam finite element model is developed and validated with several numerical applications. The displacements, rotations, amount of warping, normal and shear stresses are compared with reference solutions for general loading cases involving stretching, bending, torsion and/or distortion. Some examples concern the case of beam assemblies with different shaped profiles where the connection type determines the nature of the warping transmission. Other analyses –for which the straightness assumption of Timoshenko theory is relaxed– investigate shear deformation effects on the deflection of short and thin beams by varying the aspect ratio of the beam. Further applications identify the cross sectional distortion and highlight the importance of the distortion on the stresses when compared to bending and torsion even in simple loading cases.

Finally, a non linear finite element based on the updated lagrangian formulation is developed by including torsional warping degrees of freedom. An incremental iterative method using the arc length and the Newton-Raphson methods is used to solve the non linear problem. Examples are given to study the flexural, torsional, flexural torsional and lateral torsional buckling problems for which a coupling between the variables describing the flexural and the torsional degrees of freedom occurs. The finite element results are compared to analytical solutions based on different warping functions and commonly used in linear stability for elastic structures having insufficient lateral or torsional stiffnesses that cause an out of plane buckling.


Doctorat en sciences appliquées
info:eu-repo/semantics/nonPublished

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15

Ba-abbad, Mazen. "Reliability-based Design Optimization of a Nonlinear Elastic Plastic Thin-Walled T-Section Beam." Diss., Virginia Tech, 2004. http://hdl.handle.net/10919/27895.

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A two part study is performed to investigate the application of reliability-based design optimization (RBDO) approach to design elastic-plastic stiffener beams with Tsection. The objectives of this study are to evaluate the benefits of reliability-based optimization over deterministic optimization, and to illustrate through a practical design example some of the difficulties that a design engineer may encounter while performing reliability-based optimization. Other objectives are to search for a computationally economic RBDO method and to utilize that method to perform RBDO to design an elastic-plastic T-stiffener under combined loads and with flexural-torsional buckling and local buckling failure modes. First, a nonlinear elastic-plastic T-beam was modeled using a simple 6 degree-of-freedom non-linear beam element. To address the problems of RBDO, such as the high non-linearity and derivative discontinuity of the reliability function, and to illustrate a situation where RBDO fails to produce a significant improvement over the deterministic optimization, a graphical method was developed. The method started by obtaining a deterministic optimum design that has the lowest possible weight for a prescribed safety factor (SF), and based on that design, the method obtains an improved optimum design that has either a higher reliability or a lower weight or cost for the same level of reliability as the deterministic design. Three failure modes were considered for an elastic-plastic beam of T cross-section under combined axial and bending loads. The failure modes are based on the total plastic failure in a beam section, buckling, and maximum allowable deflection. The results of the first part show that it is possible to get improved optimum designs (more reliable or lighter weight) using reliability-based optimization as compared to the design given by deterministic optimization. Also, the results show that the reliability function can be highly non-linear with respect to the design variables and with discontinuous derivatives. Subsequently, a more elaborate 14-degrees-of-freedom beam element was developed and used to model the global failure modes, which include the flexural-torsional and the out-of-plane buckling modes, in addition to local buckling modes. For this subsequent study, four failure modes were specified for an elasticplastic beam of T-cross-section under combined axial, bending, torsional and shear loads. These failure modes were based on the maximum allowable in-plane, out-ofplane and axial rotational deflections, in addition, to the web-tripping local buckling. Finally, the beam was optimized using the sequential optimization with reliabilitybased factors of safety (SORFS) RBDO technique, which was computationally very economic as compared to the widely used nested optimization loop techniques. At the same time, the SOPSF was successful in obtaining superior designs than the deterministic optimum designs (either up to12% weight savings for the same level of safety, or up to six digits improvement in the reliability for the same weight for a design with Safety Factor 2.50).
Ph. D.
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16

高學常 and Hok-sheung Go. "Lateral and torsional analysis of shear cores by semi-analytical formulation." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 1991. http://hub.hku.hk/bib/B31209725.

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17

Go, Hok-sheung. "Lateral and torsional analysis of shear cores by semi-analytical formulation /." [Hong Kong] : University of Hong Kong, 1991. http://sunzi.lib.hku.hk/hkuto/record.jsp?B13009564.

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18

Di, Pisa Corrado. "Boundary element method for fracture mechanics analysis of thin-walled assembled structures undergoing large deflection." Thesis, Queen Mary, University of London, 2005. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.424714.

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19

Nanayakkara, Masarachige A. "Finite element analysis for the elastic stability of thin walled open section columns under generalized loading." Thesis, Loughborough University, 1986. https://dspace.lboro.ac.uk/2134/7501.

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The current interest in collapse characteristics brought about by crashworthiness requirements ýas shown the need for a better understanding and predictive capability for the thin walled open section structures. In general three possible modes exist in which a loaded thin walled open section column can buckle: 1) they can bend in the plane of one of the principal axes; 2) they can twist about the shear. centre; 3) or they can bend and twist simultaneously. The following study was undertaken to investigate the general failure of thin walled open section structures. A literature survey was conducted and it prevailed that a basic fundamental theoretical study was vital in describing the behaviour of thin walled structural members. The following stages of theoretical study have been completed: 1) Formulation of the stiffness matrix to predict the generalised force-displacement relationships assuming the small displacement theory in the linear elastic range. 2) Formulation of the geometric stiffness matrix to predict the buckling criteria under generalised loading and end constraints in the linear elastic range. 3) Formulation of the compound coordinate transformation matrix to relate local and global displacements or forces. 4) Preparation of the associated finite element computer program to solve general thin walled open sections structural problems.
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20

Back, Sung-Yong. "A shear-flexible finite element model for lateral torsional buckling analysis of thin-walled open beams." Diss., Georgia Institute of Technology, 1992. http://hdl.handle.net/1853/20999.

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21

Walker, B. D. "A combined finite strip/finite element method for the analysis of partially prismatic thin-walled structures." Thesis, University of Southampton, 1986. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.375679.

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22

Ma, Jiayao. "Thin-walled tubes with pre-folded origami patterns as energy absorption devices." Thesis, University of Oxford, 2011. http://ora.ox.ac.uk/objects/uuid:7502b18d-674d-4eff-bbc4-e649aa4d7f42.

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This dissertation is concerned with a type of energy absorption device made of thin-walled tubes. The tubes will undergo plastic deformation when subjected to an impact loading, and therefore absorb kinetic energy. It has been found that, if the surface of a tube is pre-folded according to an origami pattern, the failure mode of the tube can be altered, leading to a noticeable increase in energy absorption while at the same time, reducing the force needed to initiate plastic deformation within the tube. The main work is presented in four parts. First of all, an experimental study of a type of previously reported thin-walled square tube with pre-manufactured pyramid patterns on the surface has been conducted. Quasi-static axial crushing tests show that the octagonal mode, although numerically proven to be efficient in terms of energy absorption, cannot be consistently triggered. Secondly, a new type of thin-walled tubular energy absorption device, known as the origami tube, which has origami pattern pre-fabricated on the surface, has been studied. A family of origami patterns has been designed for tubes with different profiles. The performances of a series of origami tubes with various configurations subjected to quasi-static axial crushing have been investigated numerically. It is found that a new failure mode, referred to as the complete diamond mode, can be triggered, and both over 50% increase in the mean crushing force and about 30% reduction in the peak force can be achieved in a single tube design in comparison with those of a conventional square tube with identical surface area and wall thickness. A theoretical study of the axial crushing of square origami tubes has been conducted and a mathematical formula has been derived to calculate the mean crushing force. Comparison between theoretical prediction and numerical results shows a good agreement. Quasi-static axial crushing experiments on several square origami tube samples have been carried out. The results show that the complete diamond mode is formed in the samples and both peak force reduction and mean crushing force increase are attained. Thirdly, a new type of curved thin-walled beam with pre-manufactured origami pattern on the surface, known as the origami beam, has been designed and analyzed. A numerical study of a series of origami beams with a variety of configurations subjected to quasi-static lateral bending has been conducted. The results show that two new failure modes, namely, the longitudinal folding mode and the mixed mode, can be induced, and both reduced peak force and increased energy absorption are achieved. Finally, a number of automobile frontal bumpers, which have the origami tube and the origami beam as key components, have been designed and analyzed. Three impact tests have been conducted on each bumper. The numerical results show that both types of origami structures can perform well in realistic loading scenarios, leading to improved energy absorption of the bumpers.
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23

Yidris, Noorfaizal. "The post-buckled coupled mode interaction behaviour of thin-walled members in compression using finite element simulation." Thesis, Loughborough University, 2012. https://dspace.lboro.ac.uk/2134/9949.

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The work of this thesis sets out to give a clearer in-depth understanding of the failure mechanics of thin-walled compression members which are associated with complex interactions between the different buckling modes during the loading process. This thesis employs the finite element method in order to examine the effect of the modelling techniques imposed at the section junctions of short struts and to investigate the influence of the local and global end conditions with regard to support and loading on the compressive response of various sections, i.e. I-sections, plain channel sections, box-sections, and lipped channel sections. The thesis also details appropriate finite element modelling strategies and solution procedures taking due account of the influence of material nonlinearity and geometrical imperfections for the determination of the coupled mode interactive response of thin-walled compression members. A detailed account of the complete loading history of the compression members from the beginning of loading through to final collapse is given in the thesis. This involves elastic local buckling, nonlinear elastic and elasto-plastic post-buckling interaction behaviour and yield propagation leading to the development of an appropriate failure mechanism which causes final collapse and unloading. A new finite element modelling strategy has been developed in the thesis with particular reference to being able to deal with the classical assumption of the stress-free in-plane boundary conditions existing at the section junctions of short length strut members during post-local buckling. Also, for fixed-ended columns, with particular reference to singly-symmetric plain channel sections, it has been shown that column deflections are initiated from the onset of local buckling for the case of the constituent plate elements of the section being locally rotationally constrained at their ends. Such columns should not therefore be considered as an overall bifurcation problem of the locally buckled member. In the case of the pinned and fixed-ended boundary conditions of the columns, the finite element simulations are shown to be able to accurately describe the rather different complex failure mechanics with a high degree of imperfection sensitivity being shown to be in evidence for the pin-ended case. Considerably good agreement has been shown to occur with the independent simulations of other researchers using the finite strip method of analysis, with the analytical solution procedures of others and with the findings from independent test work and this has provided confidence in the viability and usefulness of the modelling strategies and solution procedures developed in this thesis.
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24

Abdussalam, Ragba Mohamed. "Finite element analysis of the design and manufacture of thin-walled pressure vessels used as aerosol cans." Thesis, Swansea University, 2006. https://cronfa.swan.ac.uk/Record/cronfa42323.

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Thin-walled cylinders are used extensively in the food packaging and cosmetics industries. The cost of material is a major contributor to the overall cost and so improvements in design and manufacturing processes are always being sought. Shape optimisation provides one method for such improvements. Aluminium aerosol cans are a particular form of thin-walled cylinder with a complex shape consisting of truncated cone top, parallel cylindrical section and inverted dome base. They are manufactured in one piece by a reverse-extrusion process, which produces a vessel with a variable thickness from 0.31 mm in the cylinder up to 1.31 mm in the base for a 53 mm diameter can. During manufacture, packaging and charging, they are subjected to pressure, axial and radial loads and design calculations are generally outside the British and American pressure vessel codes. 'Design-by-test' appears to be the favoured approach. However, a more rigorous approach is needed in order to optimise the designs. Finite element analysis (FEA) is a powerful tool for predicting stress, strain and displacement behaviour of components and structures. FEA is also used extensively to model manufacturing processes. In this study, elastic and elastic-plastic FEA has been used to develop a thorough understanding of the mechanisms of yielding, 'dome reversal' (an inherent safety feature, where the base suffers elastic-plastic buckling at a pressure below the burst pressure) and collapse due to internal pressure loading and how these are affected by geometry. It has also been used to study the buckling behaviour under compressive axial loading. Furthermore, numerical simulations of the extrusion process (in order to investigate the effects of tool geometry, friction coefficient and boundary conditions) have been undertaken. Experimental verification of the buckling and collapse behaviours has also been carried out and there is reasonable agreement between the experimental data and the numerical predictions.
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25

Li, Hangang Carleton University Dissertation Engineering Civil. "Thin-walled box beam finite elements for static analysis of curved haunched and skew multicell box girder bridges." Ottawa, 1992.

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26

Kolhatkar, Tanmay. "Nonlinear dynamic interactions between a rigid attachment bolted to a thin-walled sheet metal structure." The Ohio State University, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=osu1587124580918153.

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27

Jrad, Wassim. "Dynamic behavior of thin-walled beams : Analytical, numerical and experimental approaches." Electronic Thesis or Diss., Université de Lorraine, 2019. http://www.theses.fr/2019LORR0271.

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Les poutres à parois minces à sections ouvertes sont des éléments de base des ouvrages courants en génie civil, de l'automobile et de l'aéronautique. En raison de leur élancement et la forme des sections, elles sont très sensibles à la torsion et aux instabilités aussi bien en statique qu’en dynamique. En dynamique, les modes de vibration en torsion sont plus dominants par rapport au modes de flexion classiques. Pour ces raisons, les défaillances planaires de telles structures sont connues pour être une exception plutôt qu'une règle. Dans ce travail de thèse, on s’intéresse au comportement dynamique de poutres à parois minces et à section ouvertes arbitraires. En se basant sur le modèle de Vlasov qui prend en compte de la torsion et du gauchissement, les équations de mouvement 3D sont dérivées à partir du principe d’Hamilton. Des solutions analytiques originales pour différentes conditions aux limites sont dérivées pour des modes supérieurs en vibrations libres. Dans ces solutions, les effets des termes de rotation inertiels en flexion et torsion sont pris en compte. Pour des cas généraux, un modèle élément fini de poutre 3D est décrit et implémenté. Dans le modèle, un degré de liberté (ddl) est affecté au gauchissement. Toutes les matrices de rigidité masse de base sont calculées par intégration numérique (intégration de Gauss). Dans le modèle, les calculs en vibrations libres et forcées sont possibles. Le modèle est validé par comparaison aux solutions numériques et expérimentaux de la littérature. Une comparaison aux simulations des codes commerciaux est aussi suivie. Afin de valider le modèle théorique et numérique utilisé, une campagne d’essais a été suivie au LEM3 à Metz. Des essais de vibration libre et forcée sont effectués sur des poutres à parois minces avec différentes conditions aux limites. Les solutions analytiques, numériques et les mesures expérimentales sont comparées et validées. Un bon accord entre les différentes solutions est constaté. Le modèle est étendu aux poutres 3D retenues latéralement par des entretoises. Des ressorts élastiques et visqueux 3D sont ajoutés dans le modèle numérique. L'effet des entretoises est étudié dans le but d’améliorer le comportement des poutres à parois minces vis-à-vis des modes indésirables de type flexion latérale et torsion
Thin-walled beams with open section constitute main elements in engineering applications fields as in civil engineering, automotive and aerospace construction. Due to slenderness and cross section shapes, these elements are very sensitive to torsion and instabilities in both statics and dynamics. In dynamics, the torsional and flexural-torsional modes of vibration are often lower frequencies compared to the classical plane pure bending modes. Thus, planar failures of such structures are known to be an exception rather than a rule. In torsion, warping is important and governs the behavior. In this thesis work, we are interested with the dynamic behavior of thin-walled beams with arbitrary open cross sections. Based on the Vlasov’s model accounting for warping, the 3D motion equations are derived from the Hamilton’s principle. Original analytical solutions for different boundary conditions are derived for higher free vibration modes. In these solutions, the effects of the inertial rotation terms in bending and torsion are taken into consideration. For more general cases, a 3D beam finite element model is described and implemented. Compared to conventional 3D beams, warping is considered as an additional Degree Of Freedom (DOF). The mass and stiffness matrices are obtained by numerical integration (Gauss method). In the model, free and forced vibration analyses are possible. The model is validated by comparison with benchmark solutions available in the literature and other numerical results obtained from simulation on commercial codes. In order to validate the present model, laboratory test campaign is undertaken at the LEM3 laboratory in Metz. Tests are carried out on thin-walled beams with different boundary conditions. Free and forced vibration tests are performed using impact hammer and shaker machine. In the presence of arbitrary sections, flexural-torsional vibration modes are observed. The analytical, the numerical and the experimental solutions are compared and validated. Moreover, the numerical and experimental dynamic response spectra are compared. A good agreement between the various solutions is remarked. The model is extended to 3D beams in presence of lateral braces. 3D elastic and viscous springs are added in the finite element model. The effect of the springs is studied in order to improve the behavior of thin-walled beams against undesirable lateral bending and torsion modes
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28

Ryan, Bona. "Finite Element Modelling and Parametric Studies of Semi-Closed Thin-Walled Steel Polygonal Columns - Application on Steel Lattice Towers for Wind Turbines." Thesis, Luleå tekniska universitet, Institutionen för samhällsbyggnad och naturresurser, 2017. http://urn.kb.se/resolve?urn=urn:nbn:se:ltu:diva-62064.

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The trend of structural engineering in the recent years is toward the use of lighter and moreeconomical structural elements. In steel construction, peculiarly, thin-walled structural elements arebecoming more popular and have a growing importance. Improved techniques in a manufacturing ofthin-walled elements have led to increased competitiveness of such products in the buildingapplications. Some examples of such structural element can be found in everyday life in form ofcolumns, studs, roofing trusses, and light-weight frames. However, the use of slender profiles and acomplex cross sections shape lead to requirements to study instability phenomenon in a form of local,distortional, flexural, torsional and coupled instability. Such complex structural behavior is inevitablyaccompanied by demand to improve calculation methods and design provisions. In this thesis, aninnovative solution of structural element composed of thin-walled plates is proposed for theapplication on lattice support structure of wind turbine.Thin-walled cold-formed profiles are steel products usually made from cold rolled coils and folded inthe second step. In this way, only open profiles can be produced. The predominant problem of theopen cross-section is the excessive torsional effect caused by the non-coincidence between the shearcenter and mass center, and a poor torsional resistance. A better response is possible with closed crosssections, but such profiles could not be produced by the folding. The solution is to make semi-closedsection by assembling them into polygonal profiles with mechanical fasteners, as presented in thisthesis.Objective of this work is to study the proposed structural sections in design situation and toinvestigate possible design models. The expected structural behavior of the column is a mixturebetween the open and closed cross-section. These cases will be investigated through numerical study.In this thesis presented a comprehensive parametric study on the ultimate strength of proposed coldformedsteel columns using the Finite Element package ABAQUS. FE models were first developedfor columns by using automation that was made through MATLAB and Python script. The bucklingand non-linear FE study was done for the investigation of local (L), distortional (D) and global (G)possible buckling failures and ultimate resistance, respectively. Modelling issues such as boundaryconditions, meshing, initial imperfections, material models, and non-linear solution controls in FEAwere also addressed.The parametric study involved series of profiles of built-up polygonal cross-section types with variedthickness (t), number of corners (n), diameter (d), slenderness (slend), yield strength (fy), number ofpoints along corner radii (np), extension lip length (lext), gusset plate thickness (tg), member length (l),and density of fasteners (s/d ratio), loaded in compression and bending moment. The bending momentoccurs as the effect of forces acting on the connection. The purpose of this analysis is to study thecritical load, cross-sectional behavior, influence of the amplitude of initial imperfections on theultimate load, and influence of each parameter used in the analysis through Full Factorial Design.
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29

Dababneh, Odeh. "Design, Analysis And Optimization Of Thin Walled Semi-monocoque Wing Structures Using Different Structural Idealizations In The Preliminary Design Phase." Master's thesis, METU, 2011. http://etd.lib.metu.edu.tr/upload/12613759/index.pdf.

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This thesis gives a comprehensive study on the effect of using different structural idealizations on the design, analysis and optimization of thin walled semi-monocoque wing structures in the preliminary design phase. In the design part, wing structures are designed by employing two different structural idealizations that are typically used in the preliminary design phase. In the structural analysis part, finite element analysis of one of the designed wing configurations is performed using six different one and two dimensional element pairs which are typically used to model the sub-elements of semi-monocoque wing structures. The effect of using different finite element types on the analysis results of the wing structure is investigated. During the analysis study, depending on the mesh size used, conclusions are also inferred with regard to the deficiency of certain element types in handling the true external load acting on the wing structure. Finally in the optimization part, wing structure is optimized for minimum weight by using finite element models which have the same six different element pairs used in the analysis phase. The effect of using different one and two dimensional element pairs on the final optimized configurations of the wing structure is investigated, and conclusions are inferred with regard to the sensitivity of the optimized wing configurations with respect to the choice of different element types in the finite element model. Final optimized wing structure configurations are also compared with the simplified method based designs which are also optimized iteratively. Based on the results presented in the thesis, it is concluded that with the simplified methods, preliminary sizing of the wing structures can be performed with enough confidence, as long as the simplified method based designs are also optimized. Results of the simplified method of analysis showed that simplified method is applicable to be used as an analysis tool in performing the preliminary sizing of the wing structure before moving on to more refined finite element based analysis.
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30

Goodey, Richard J. "Rectangular silos; Interaction of structure and stored bulk solid." Thesis, Brunel University, 2002. http://bura.brunel.ac.uk/handle/2438/5246.

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The main aim of this research is directed towards the study of thin-walled rectangular planform silos with a view to maximising their structural efficiency. In thin plates of the type making up the wall, membrane action may increase the load carrying capability and current design guides make no account of this. Designing rectangular silos with this in mind can lead to significant structural savings. The core of the research involves using the finite element method to study the patterns of pressure exerted by the weight of a granular bulk solid on the walls of the silo structure. The stored granular solid must use an elastic-plastic material law in order to account for large deformations that can occur in a thin-walled structure. The need for this type of constitutive law led to the investigation of bulk solid properties and shows that parameters that have previously been used to categorise bulk solids may not be sufficient to describe all aspects of their behaviour. The finite element model created uses material constitutive laws that can be found in a number of packages. The required granular material parameters can be determined from a number of simple tests. This approach aims to enable engineers to routinely use similar models when designing silos. The results obtained from the finite element model exhibited some anomalies that had been observed in previous work. These were mainly apparent in the form of localised pressure peaks near the base of the model. These effects were investigated and possible mechanisms that lead to them were proposed. The results from the finite element model were compared to previous experimental work and existing theories. The model was then used to conduct parametric surveys on square and rectangular planform silos and the distribution of pressure across the wall compared to previous predictive models. Finally, a scale thin-walled metal silo was constructed and pressure measurements on filling with pea gravel made. These are compared to predictions made by the finite element model.
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31

Ahmadi, Habiburrahman. "Lateral torsional buckling of anisotropic laminated composite beams subjected to various loading and boundary conditions." Diss., Kansas State University, 2017. http://hdl.handle.net/2097/35402.

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Анотація:
Doctor of Philosophy
Department of Civil Engineering
Hayder A. Rasheed
Thin-walled structures are major components in many engineering applications. When a thin-walled slender beam is subjected to lateral loads, causing moments, the beam may buckle by a combined lateral bending and twisting of cross-section, which is called lateral-torsional buckling. A generalized analytical approach for lateral-torsional buckling of anisotropic laminated, thin-walled, rectangular cross-section composite beams under various loading conditions (namely, pure bending and concentrated load) and boundary conditions (namely, simply supported and cantilever) was developed using the classical laminated plate theory (CLPT), with all considered assumptions, as a basis for the constitutive equations. Buckling of such type of members has not been addressed in the literature. Closed form buckling expressions were derived in terms of the lateral, torsional and coupling stiffness coefficients of the overall composite. These coefficients were obtained through dimensional reduction by static condensation of the 6x6 constitutive matrix mapped into an effective 2x2 coupled weak axis bending-twisting relationship. The stability of the beam under different geometric and material parameters, like length/height ratio, ply thickness, and ply orientation, was investigated. The analytical formulas were verified against finite element buckling solutions using ABAQUS for different lamination orientations showing excellent accuracy.
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32

Sonje, Abhijit Ravindra. "Experimental and finite element investigation into the effects of manufacturing variability on the dynamic response of a bolted interface between a bracket and a thin-walled sheet metal structure." The Ohio State University, 2019. http://rave.ohiolink.edu/etdc/view?acc_num=osu1546418059243072.

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33

Le, Thanh-Nam. "Nonlinear dynamics of flexible structures using corotational beam elements." Doctoral thesis, KTH, Bro- och stålbyggnad, 2013. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-131701.

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The purpose of this thesis is to develop corotational beam elements for the nonlinear dynamic analyse of flexible beam structures. Whereas corotational beam elements in statics are well documented, the derivation of a corotational dynamic formulation is still an issue. In the first journal paper, an efficient dynamic corotational beam formulation is proposed for 2D analysis. The idea is to adopt the same corotational kinematic description in static and dynamic parts. The main novelty is to use cubic interpolations to derive both inertia terms and internal terms in order to capture correctly all inertia effects. This new formulation is compared with two classic formulations using constant Timoshenko and constant lumped mass matrices. In the second journal paper, several choices of parametrization and several time stepping methods are compared. To do so, four dynamic formulations are investigated. The corotational method is used to develop expressions of the internal terms, while the dynamic terms are formulated into a total Lagrangian context. Theoretical derivations as well as practical implementations are given in detail. Their numerical accuracy and computational efficiency are then compared. Moreover, four predictors and various possibilities to simplify the tangent inertia matrix are tested. In the third journal paper, a new consistent beam formulation is developed for 3D analysis. The novelty of the formulation lies in the use of the corotational framework to derive not only the internal force vector and the tangent stiffness matrix but also the inertia force vector and the tangent dynamic matrix. Cubic interpolations are adopted to formulate both inertia and internal local terms. In the derivation of the dynamic terms, an approximation for the local rotations is introduced and a concise expression for the global inertia force vector is obtained. Four numerical examples are considered to assess the performance of the new formulation against two other ones based on linear interpolations. Finally, in the fourth journal paper, the previous 3D corotational beam element is extended for the nonlinear dynamics of structures with thin-walled cross-section by introducing the warping deformations and the eccentricity of the shear center. This leads to additional terms in the expressions of the inertia force vector and the tangent dynamic matrix. The element has seven degrees of freedom at each node and cubic shape functions are used to interpolate local transversal displacements and axial rotations. The performance of the formulation is assessed through five examples and comparisons with Abaqus 3D-solid analyses.

QC 20131017

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34

Mezzomo, Gustavo Prates. "Análise de flambagem de perfis formados a frio utilizando modos puros de deformação." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2012. http://hdl.handle.net/10183/60995.

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A esbeltez dos perfis de aço formados a frio pode resultar na interação entre diferentes modos de flambagem, tornando a análise desses componentes uma tarefa complexa. Para o projeto de perfis formados a frio, é fundamental a compreensão da natureza do modo de flambagem ao qual estão submetidos. O cálculo de modos de flambagem puros e a quantificação da interação de modos contribuem para o estudo do comportamento desses perfis. Nesse trabalho, o cálculo da carga crítica elástica de modos de flambagem puros ou combinados é realizado através do uso de modelos de elementos finitos restringidos. Para o cálculo focado em uma classe de flambagem específica (de modos globais, distorcionais, locais ou outros), diferentes procedimentos de restrição são propostos. Utilizando um procedimento de restrição geral, o campo de deformações do modelo é restringido de acordo com uma combinação de modos de deformação da seção, definidos com base nos conceitos da teoria generalizada de vigas e do método das faixas finitas restringido. Na direção longitudinal do perfil, podem ser combinados diversos componentes harmônicos que respeitem as condições de contorno das extremidades. Também são mostrados casos em que todos os componentes harmônicos longitudinais possíveis podem ser automaticamente considerados. O cálculo de modos de flambagem combinados possibilita, automaticamente, a quantificação da interação dos modos considerados. Para validação dos procedimentos propostos, são apresentados resultados numéricos da análise de um perfil C com enrijecedores de borda, com duas diferentes condições de contorno das extremidades, e submetidos a dois tipos de carregamento. Os resultados são comparados com os fornecidos pela teoria generalizada de vigas e pelo método das faixas finitas restringido. Os procedimentos de restrição são aplicados na análise de um perfil inspirado em uma estrutura real com apoios intermediários (ao longo do comprimento), explorando a vantagem da implementação utilizando elementos finitos. O potencial dos procedimentos aqui propostos é discutido. Finalmente, foram sugeridos novos objetivos para a continuação desse trabalho.
The slenderness of cold-formed steel member can result in the interaction of different buckling modes, making the analysis of these members a complex task. In the design of thinwalled members, the understanding of the nature of the buckling mode is fundamental. The calculation of pure buckling modes and the evaluation of the interaction amongst the buckling modes help in the study of the behavior of thin-walled members. In this research, the elastic critical buckling load calculation of pure and combined buckling modes is carried out using constrained finite element models. Different constraining procedures are proposed for the calculation focused on each buckling class (of global, distortional, local or other modes). Using a general constraining procedure, the deformation fields of the model are constrained in accordance with a combination of section deformation modes, which are defined based on the concepts of the generalized beam theory and the constrained finite strip method. In the longitudinal direction on the member, several harmonic components may be combined, which must meet the boundary conditions of the member ends. Cases where all possible longitudinal harmonic components can be automatically considered are also presented. In order to validate the proposed procedures, numerical results are presented on the analysis of a lipped channel, with two different configurations of boundary conditions at member ends and submitted to two different types of loading. The results are compared to the ones provided by the generalized beam theory and the constrained finite strip method. The constraining procedures are applied to the analysis of a member inspired by a real structure with intermediate supports (between the member ends), exploring the advantages of the implementation using the finite element method. The potentiality of the procedures proposed herein is discussed. Finally, new aims are proposed in order to continue this research.
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35

Le, Thanh Nam. "Nonlinear dynamics of lexible structures using corotational beam elements." Phd thesis, INSA de Rennes, 2013. http://tel.archives-ouvertes.fr/tel-00954739.

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Анотація:
The purpose of this thesis is to propose several corotational beam formulations for both 2D and 3D nonlinear dynamic analyse of flexible structures. The main novelty of these formulations is that the cubic interpolation functions are used to derive not only the internal force vector and the tangent stiffness matrix but also the inertial force vector and the dynamic matrix. By neglecting the quadratic terms of the local transversal displacements, closed-form expressions for the inertial terms are obtained for 2D problems. Based on an extensive comparative study of the parameterizations of the finite rotations and the time stepping method, and by adopting an approximation of the local rotations, two consistent and effective beam formulations for 3D dynamics are developed. In contrast with the first formulation, the second one takes into account the warping deformations and the shear center eccentricity. The accuracy of these formulations is demonstrated through several numerical examples.
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36

MororÃ, Luiz AntÃnio Taumaturgo. "AnÃlise nÃo linear geomÃtrica de vigas laminadas de parede fina." Universidade Federal do CearÃ, 2013. http://www.teses.ufc.br/tde_busca/arquivo.php?codArquivo=14007.

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Анотація:
Conselho Nacional de Desenvolvimento CientÃfico e TecnolÃgico
A utilizaÃÃo de vigas laminadas de parede fina nas Engenharias AeronÃutica, Civil, MecÃnica e Naval tem crescido bastante nos Ãltimos anos, devido a suas elevadas relaÃÃes rigidez/peso e resistÃncia/peso. Esses elementos estruturais normalmente apresentam paredes finas devido à alta resistÃncia dos materiais compÃsitos. Outra caracterÃstica importante à que, mesmo sem apresentar grandes deformaÃÃes e sem que o limite elÃstico do material seja ultrapassado, estas vigas apresentam comportamento nÃo linear geomÃtrico devido à sua elevada esbeltez, acarretando em grandes deslocamentos e rotaÃÃes. Dependendo da laminaÃÃo utilizada, as vigas de materiais compÃsitos podem apresentar diversos acoplamentos entre esforÃos e deformaÃÃes, tornando a sua anÃlise bem mais complexa do que a anÃlise de vigas de material isotrÃpico. Neste trabalho, foram desenvolvidos dois elementos finitos de pÃrtico espacial para anÃlise nÃo linear geomÃtrica de vigas laminadas de parede fina. As propriedades seccionais da viga sÃo avaliadas atravÃs de teorias de vigas laminadas de parede fina apropriadas, em que desprezam-se os efeitos do empenamento e do cisalhamento transversal. Tais teorias de vigas laminadas conduzem a uma matriz constitutiva 4x4, onde diferentes nÃveis de acoplamento entre esforÃos e deformaÃÃes de viga sÃo considerados, por exemplo, pode-se obter uma matriz constitutiva diagonal ou cheia. A abordagem corrotacional independente do elemento à utilizada para o tratamento de grandes deslocamentos e rotaÃÃes de corpo rÃgido no espaÃo. No Ãmbito local, sÃo utilizados dois elementos, um baseado na teoria linear e outro na descriÃÃo Lagrangeana Total. O tratamento matemÃtico das grandes rotaÃÃes no espaÃo à realizado por meio do tensor das rotaÃÃes (fÃrmula de Rodrigues), juntamente com o conceito do pseudovetor. As implementaÃÃes dos elementos finitos propostos neste trabalho sÃo realizadas no software de cÃdigo aberto FAST. A metodologia de trabalho segue o roteiro clÃssico de mÃtodos computacionais, incluindo formulaÃÃo, implementaÃÃo, verificaÃÃo e validaÃÃo dos resultados. A verificaÃÃo à realizada atravÃs dos modelos tridimensionais de elementos finitos de casca e sÃlido desenvolvidos no software comercial ABAQUS. A validaÃÃo à realizada por meio da comparaÃÃo com resultados de ensaios experimentais encontrados na literatura. No que diz respeito à avaliaÃÃo das propriedades seccionais, pode-se verificar uma Ãtima concordÃncia entre as teorias de vigas laminadas adotadas neste trabalho e os resultados numÃricos e de ensaios experimentais, para todas as laminaÃÃes e carregamentos considerados. No caso dos elementos de pÃrtico espacial, verificou-se uma Ãtima concordÃncia entre os resultados dos elementos finitos propostos neste trabalho e os resultados analÃticos e computacionais disponÃveis na literatura. Observa-se tambÃm que o elemento baseado na descriÃÃo Lagrangeana à mais eficiente do que o elemento baseado na teoria linear no que tange à capacidade de apresentar uma resposta satisfatÃria com uma malha menos refinada.
The use of thin walled laminate beams in Aeronautical, Civil, Mechanical and Naval Enginee- ring is increasing in the last years. This is due to their high stiffness/weight and strength/weight ratios. Composite beams and other structural elements tend to have thin walls due to the elevated strength of the material. Other important aspect is that, even without reaching large strains and without overcoming the elastic limit of the material, such beams present geometric nonlinear behavior due to high their slenderness, leading to large displacements and rotations. Depen- ding on the composite layup, the beams of composite materials can present several couplings between generalized stresses and strains, requiring a more complex analysis procedure when compared to isotropic beams. In this work, two three-dimensional space frame finite elements that can be used to analyze composite thin-walled beams subjected to geometric non-linearity were developed. The cross-section properties of the beams are evaluated through suitable thin walled beam theories, where the effects of the warping and transverse shear are neglected. Such theories yield a 4x4 constitutive matrix for the laminate and different levels of coupling between generalized stresses and strains can be considered. Depending of such couplings, the constitu- tive matrix can either be full or diagonal. The element independent corotational approach was used in order to consider large displacaments and rigid body rotations in space. In the local coordinate system, two elements are used, one based on the linear strain theory and the other on the Total Lagrangian formulation. The mathematical treatment of the large rotations in the space is performed by means of the rotation tensor (Rodriguesâs formula) in conjunction with the concept of the pseudovector. The computational implementations of the two finite elements proposed in this work were done in the open source software FAST ( Finite Element Analysis Tool ). The methodology used follows the classical steps used in computational methods, in- cluding formulation, implementation, verification and validation of results. Such verification is accomplished through shell and solid three-dimensional finite element models developed in the ABAQUS commercial software. The validation is performed by means of comparison with the experimental results found in literature. Regarding the evaluation of cross-sectional properties, one can observe a good agreement between the laminated beam theories adopted in this work and numerical and experimental results for all composite layups and load conditions conside- red. In the case of space frame elements, a good agreement is obtained between the results of finite elements proposed in this work and the analytical and computational results available in the literature. It is also observed that the element based on the Lagrangian formulation is more efficient than the element based on the linear theory regarding the ability to provide a satisfatory response with a less refined mesh
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37

Ehrlich, Tomáš. "Zatížení větrem na chladící věž." Master's thesis, Vysoké učení technické v Brně. Fakulta stavební, 2015. http://www.nusl.cz/ntk/nusl-227719.

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Thesis is concerned with modeling fluid dynamics and computing wind load on thin-walled structure of cooling tower. Two models for computational fluid dynamics are presented – one with singleton cooling tower and second with group of four cooling tower. Thesis includes also a structural model of cooling tower and methodology of wind load transfer is presented.
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38

Geara, Fadi. "Contribution à l'étude de la torsion des poutres en voiles minces et des poutres à profil dissymétrique." Châtenay-Malabry, Ecole centrale de Paris, 1998. http://www.theses.fr/1998ECAP0598.

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Анотація:
Cette recherche est une contribution à l'étude de la torsion des poutres en voiles minces ouverts et des poutres à sections transversales non symétriques. En effet, dans le cas des poutres en voiles minces ouverts, on a développé la statique de la torsion suivant la théorie de Vlassov, c'est-à-dire en tenant compte du gauchissement qui accompagne en général la torsion, et ses effets sur les éléments de structure. Notre travail commence par la résolution de l'équation différentielle de la torsion gênée pour diverses conditions aux limites et différents chargements. Des exemples numériques ont concrétisé l'importance de la prise en compte du gauchissement dans le cas des éléments minces. L'étude a été complétée par la formulation de la poutre continue soumise à la torsion et par une étude numérique comparative avec la méthode des éléments finis en utilisant une modélisation en éléments coques et montrant la concordance entre les deux méthodes. D'autre part, dans le cas des poutres a profil dissymétrique, le centre de torsion n'est pas en général confondu avec le centre de gravité. Notre travail était de prendre en compte cette excentricité et d'introduire son effet dans la matrice de rigidité d'un élément de poutre droite, ainsi que ses effets sur les sollicitations et les déplacements des éléments de structure. L'étude a été complétée par plusieurs exemples schématisant l'intérêt de l'utilisation de la matrice de rigidité modifiée.
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39

Komoráš, Miroslav. "Pulsace toku kapaliny v pružné trubici." Master's thesis, Vysoké učení technické v Brně. Fakulta strojního inženýrství, 2019. http://www.nusl.cz/ntk/nusl-401537.

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This master’s thesis is dealing with analysis of fluid flow pulse in a flexible tube representing e.g. an artery in a human body. In ANSYS program, 3D simulations were performed, and these are so-called interrelated FSI analysis. In Maple software, 1D simulations of fluid flow in the tube were performed for various thin-walled and thick-walled variants. The aim is using these programs to determine the flow rates and pressures in the tube, its wall deformation and stress. Therefore, the theoretical part deals mainly with basic equations of flow dynamics, linear and nonlinear models and rotationally symmetric vessels. In the computational part are described individual procedures in the mentioned programs.
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40

Cheng, Shanshan. "Fire performance of cold-formed steel sections." Thesis, University of Plymouth, 2015. http://hdl.handle.net/10026.1/3316.

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Анотація:
Thin-walled cold-formed steel (CFS) has exhibited inherent structural and architectural advantages over other constructional materials, for example, high strength-to-weight ratio, ease of fabrication, economy in transportation and the flexibility of sectional profiles, which make CFS ideal for modern residential and industrial buildings. They have been increasingly used as purlins as the intermediate members in a roof system, or load-bearing components in low- and mid-rise buildings. However, using CFS members in building structures has been facing challenges due to the lack of knowledge to the fire performance of CFS at elevated temperatures and the lack of fire design guidelines. Among all available design specifications of CFS, EN1993-1-2 is the only one which provided design guidelines for CFS at elevated temperatures, which, however, is based on the same theory and material properties of hot-rolled steel. Since the material properties of CFS are found to be considerably different from those of hot-rolled steel, the applicability of hot-rolled steel design guidelines into CFS needs to be verified. Besides, the effect of non-uniform temperature distribution on the failure of CFS members is not properly addressed in literature and has not been specified in the existing design guidelines. Therefore, a better understanding of fire performance of CFS members is of great significance to further explore the potential application of CFS. Since CFS members are always with thin thickness (normally from 0.9 to 8 mm), open cross-section, and great flexural rigidity about one axis at the expense of low flexural rigidity about a perpendicular axis, the members are usually susceptible to various buckling modes which often govern the ultimate failure of CFS members. When CFS members are exposed to a fire, not only the reduced mechanical properties will influence the buckling capacity of CFS members, but also the thermal strains which can lead additional stresses in loaded members. The buckling behaviour of the member can be analysed based on uniformly reduced material properties when the member is unprotected or uniformly protected surrounded by a fire that the temperature distribution within the member is uniform. However if the temperature distribution in a member is not uniform, which usually happens in walls and/or roof panels when CFS members are protected by plaster boards and exposed to fire on one side, the analysis of the member becomes very complicated since the mechanical properties such as Young’s modulus and yield strength and thermal strains vary within the member. This project has the aim of providing better understanding of the buckling performance of CFS channel members under non-uniform temperatures. The primary objective is to investigate the fire performance of plasterboard protected CFS members exposed to fire on one side, in the aspects of pre-buckling stress distribution, elastic buckling behaviour and nonlinear failure models. Heat transfer analyses of one-side protected CFS members have been conducted firstly to investigate the temperature distributions within the cross-section, which have been applied to the analytical study for the prediction of flexural buckling loads of CFS columns at elevated temperatures. A simplified numerical method based on the second order elastic – plastic analysis has also been proposed for the calculation of the flexural buckling load of CFS columns under non-uniform temperature distributions. The effects of temperature distributions and stress-strain relationships on the flexure buckling of CFS columns are discussed. Afterwards a modified finite strip method combined with the classical Fourier series solutions have been presented to investigate the elastic buckling behaviour of CFS members at elevated temperatures, in which the effects of temperatures on both strain and mechanical properties have been considered. The variations of the elastic buckling loads/moments, buckling modes and slenderness of CFS columns/beams with increasing temperatures have been examined. The finite element method is also used to carry out the failure analysis of one-side protected beams at elevated temperatures. The effects of geometric imperfection, stress-strain relationships and temperature distributions on the ultimate moment capacities of CFS beams under uniform and non-uniform temperature distributions are examined. At the end the direct strength method based design methods have been discussed and corresponding recommendations for the designing of CFS beams at elevated temperatures are presented. This thesis has contributed to improve the knowledge of the buckling and failure behaviour of CFS members at elevated temperatures, and the essential data provided in the numerical studies has laid the foundation for further design-oriented studies.
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41

Шейченко, Роман Ігорович. "Забезпечення міцності тонкостінних конструкцій із підвищеними технічними характеристиками". Thesis, Національний технічний університет "Харківський політехнічний інститут", 2019. http://repository.kpi.kharkov.ua/handle/KhPI-Press/41327.

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Анотація:
Дисертація на здобуття наукового ступеня кандидата технічних наук (доктора філософії) за спеціальністю 05.02.09 "Динаміка та міцність машин" (13 – Механічна інженерія). – Національний технічний університет «Харківський політехнічний інститут», Харків, 2019. Потреби сучасної промисловості, транспорту і сфери послуг у інноваційних виробах із підвищеними техніко-економічними характеристиками останнім часом різко зростають. При цьому велику частку серед такої продукції займають тонкостінні машинобудівні конструкції, у яких раціонально поєднуються масові і характеристики міцності. У той же час на багато виробів (літаки, судна, рухомий склад залізниць, крани, перевантажувачі, ємності високого тиску, апарати хімічної промисловості, устаткування агропромислового комплексу) поширюються суворі офіційні правила і норми, спрямовані, у першу чергу, на забезпечення безпеки експлуатації. Відповідно, при проектних дослідженнях використовуються усталені методики розрахунку, а також традиційні технічні рішення. Незважаючи на тиск сталої практики, що схиляється до створення виробів у вигляді «клонів» давно створених аналогів, діє також протилежна тенденція. Вона породжується загальним прагненням до прогресу, навіть у консервативних областях діяльності, а також економічними міркуваннями. Більш того, багато споживачів інноваційних виробів установлюють свої додаткові вимоги до продукції, що спрямовані на продовження терміну служби конструкцій, підвищення їхньої продуктивності, інтенсивності експлуатаційних режимів або навантажувальної здатності. У цих обставинах, окрім нормативних обмежень, з’являються додаткові, що ускладнює виконання вимог до проектованих конструкцій. Таким чином, виникла і посилюється у своїй актуальності та важливості науково-практична задача розробки методів забезпечення міцності інноваційних тонкостінних машинобудівних конструкцій при дії комплексу експлуатаційних навантажень. Її постановка, розв’язання та впровадження у практику проектних досліджень склала мету, зміст і напрями дисертаційних досліджень. У дисертаційній роботі розв’язана науково-технічна задача, яка полягає в удосконалення методів і моделей для проектного забезпечення міцності тонкостінних машинобудівних конструкцій при дії комплексу експлуатаційних навантажень. У роботі для аналізу напружено-деформованого стану тонкостінних машинобудівних конструкцій застосовуються співвідношення теорії пружності і методу скінченних елементів. Формування геометричної форми досліджуваних конструкцій здійснювалося методами твердотільного і поверхневого моделювання. Для варіативної зміни структури і розмірів досліджуваних об’єктів адаптовано і розвинено метод узагальненого параметричного моделювання стосовно інноваційних тонкостінних машинобудівних конструкцій. Експериментальні дослідження здійснювалися методами тензометрії та акселерометрії. У ході виконання дисертаційного дослідження отримано наступні наукові результати: 1) проведено аналіз умов експлуатації, нормативних вимог, а також методів розрахунку тонкостінних машинобудівних конструкцій з урахуванням обмежень на міцність, і на цій основі визначені напрями дисертаційних досліджень; 2) удосконалено методи і моделі для обґрунтування проектних параметрів інноваційних тонкостінних машинобудівних конструкцій за критеріями міцності при дії комплексу експлуатаційних навантажень із урахуванням нормативних обмежень; 3) здійснено розв’язання низки прикладних задач проектного обґрунтування технічних рішень для тонкостінних машинобудівних конструкцій за критеріями міцності та довговічності; 4) здійснено розрахунково-експериментальні дослідження напружено- деформованого стану інноваційних тонкостінних машинобудівних конструкцій, які спроектовано на основі рекомендацій із застосуванням результатів дисертаційних досліджень; 5) впроваджено результати досліджень у виробництво.
Тhesis for candidate of technical science degree (Philosophy Doctor) in speciality 05.02.09 – Dynamics and Strength of Machines (13 – mechanical engineering). – National Тechnical University «Kharkov Polytechnic Institute», Kharkiv, 2019. The needs of modern industry, transport and services in innovative products with increased technical and economic characteristics have recently been increasing dramatically. Large proportion of such products are thin-walled engineering structures, which rationally combine mass and strength characteristics. At the same time, strict rules and regulations are applied to many products (aircraft, ships, rolling stock, cranes, reloaders, high-pressure vessels, chemical industry equipment, agricultural equipment) for ensure the operation safety. Accordingly, design studies use established computational methods, as well as traditional technical solutions. In spite of pressure of established practice, which tends to create products as "clones" of long-created analogues, opposite trend also applies. It is generated by general aspiration for progress, even in conservative areas of activity, as well as economic considerations. Moreover, many consumers of innovative products set their additional requirements for products aimed at extending service life of structures, increasing their productivity, intensity of operating modes or load capacity. In these circumstances, in addition to regulatory restrictions, there are additional ones, which complicates the requirements fulfillment for projected designs. Thus, the scientific and practical task of developing methods for strength ensuring of innovative thin-walled engineering structures under action of operating loads complex has appeared and is intensified in its urgency and importance. Its formulation, solution and implementation to design studies practice is goal, content and directions of dissertation research. In the dissertation work the scientific and technical problem is solved, which consists in methods and models improvement for strength ensurance of thin-walled engineering structures under action of operational loads complex. In the work for stress-strain state analysis of thin-walled engineering structures the theory of elasticity ratios and the finite element method are used. Geometric shape formation of investigated structures was carried out by methods of solid state and surface modeling. For structure and size variation of studied objects, the method of generalized parametric modeling for innovative thin-walled engineering structures is adapted and developed. Experimental studies were carried out using strain gauge and accelerometer methods. In course of dissertation research the following scientific results were obtained: 1) an analysis of operating conditions, regulatory requirements, as well as analysis methods of thin-walled engineering structures taking into account the constrains on durability, and on this basis, the dissertation research directions were determined; 2) methods and models for design parameters justification of innovative thin-walled engineering structures according to strength criteria under action of operational loads complex, taking into account regulatory constraints are improved; 3) solution of a number of applied tasks of technical solutions substantiation for the thin-walled engineering structures according to strength and durability criteria; 4) computational and experimental studies of stress-strain state of innovative thin-walled engineering structures that are designed on the basis of recommendations with application of dissertation research results; 5) research results are introduced into production.
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42

Шейченко, Роман Ігорович. "Забезпечення міцності тонкостінних конструкцій із підвищеними технічними характеристиками". Thesis, Національний технічний університет "Харківський політехнічний інститут", 2019. http://repository.kpi.kharkov.ua/handle/KhPI-Press/41324.

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Анотація:
Дисертація на здобуття наукового ступеня кандидата технічних наук за спеціальністю 05.02.09 – динаміка таміцність машин. Національний технічний університет «Харківський політехнічний інститут», Міністерство освіти і науки України, Харків, 2019. Дисертація присвячена удосконаленню методів і моделей для проектного забезпечення міцності тонкостінних машинобудівних конструкцій при дії комплексу експлуатаційних навантажень. Обґрунтування раціональних параметрів і конструктивних рішень ТСМБК здійснюється за критеріями мінімізації маси, зниження напружень, підвищення терміну експлуатації. Ураховуються апроксимації залежностей критеріальних величин, що поступово локалізуються, від варійованих параметрів. Узагальненими параметрами виступають структура, проектно-технологічні рішення ТСМБК, конструктивні параметри і експлуатаційні режими. При цьому забезпечується розв’язання задач одиничного аналізу, багатоваріантних досліджень, а також обґрунтування раціональних проектно-технологічних рішень. На розвиток відомих підходів розглянуті наступні узагальнення: уніфікація, доцільність, ефективності, ідентифікація навантажень, верифікація, прогнозування, відлаштування. Здійснена також алгоритмізація запропонованих методів розрахунку НДС тонкостінних машинобудівних конструкцій на основі поєднання переваг універсальних і спеціальних систем. Проведено розв’язання низки прикладних задач. Обґрунтовано раціональні проектні параметри інноваційних ТСМБК. Представлено результати експериментальних досліджень інноваційних вагону-цистерни, вагону-платформи і крана-перевантажувача, які спроектовано і виготовлено на основі впровадження рекомендацій за підсумками дисертаційних досліджень.
Thesis for the degree of Candidate of Technical Sciences in specialty 05.02.09 – Dynamics and strength of machines. National Technical University «Kharkiv Polytechnic Institute», Ministry of Education and Science of Ukraine, Kharkiv, 2019. The thesis is devoted to the improvement of methods and models for the design ensuring of the strength of thin-walled engineering structures under the action of operational loadings complex. The justification for rational parameters and design solutions for thin-walled engineering structures is carried out according to the criteria of mass minimizing, stresses reducing, and service life increasing. Various additional criteria such as cost, manufacturability, economy, energy efficiency, can be taken into account in the formation of the quality function. The dependences approximations of criterion values, which are gradually localized, from variable parameters are taken into account. The structure, design and technological solutions of thin-walled engineering structures, structural parameters and operating modes are the generalized parameters. This provides a solution to the problems of a single analysis, multivariate studies, as well as the justification for rational design and technological solutions. The following generalizations are considered: unification, expediency, efficiency, loading identification, verification, forecasting, tune-up in development of known approach. The algorithmization of proposed methods for calculating of the stress strain state of thin-walled engineering structures has also been carried out based on a combination of the advantages of universal and special systems. A number of applied problems are solved. Parametric finite element models of researched objects have been developed based on a set of studies of the stress-strain state of the power elements. The rational design parameters of innovative thin-walled engineering structures are determined. The results of experimental studies of innovative tank cars, platform cars and loading cranes, which are designed and manufactured based on the implementation of recommendations from dissertation research, are presented. Comparative experimental and computational studies of the structures stress-strain state were carried out. They are combined with certification tests, during which the stresses in the power elements were recorded. The operational loadings are determined which are acting on thin-walled structures. During the tests, regularities were established that determine the dependence of the loadings components on the structure from various factors. Verification of the numerical models parameters of thin-walled engineering constructions elements was carried out. Designed on the basis of researches innovative structures have improved technical and economic characteristics compared with similar ones.
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43

Атрошенко, Александр Александрович. "Анализ конструкционной прочности составных тонкостенных конструкций с болтовым соединением элементов". Thesis, НТУ "ХПИ", 2016. http://repository.kpi.kharkov.ua/handle/KhPI-Press/21814.

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Анотація:
Диссертация на соискание научной степени кандидата технических наук по специальности 05.02.09 – динамика и прочность машин. Национальный технический университет "Харьковский политехнический институт", Министерство образования и науки Украины, Харьков, 2016. Диссертация посвящена разработке подходов, методов и моделей для исследования конструкционной прочности составных тонкостенных машиностроительных конструкций с болтовым соединением элементов. В работе решена задача анализа напряженно-деформированного состояния составных тонкостенных машиностроительных конструкций с болтовым соединением элементов, а также его реализация и определение закономерностей распределения прогибов, смещений и продольных усилий. Также в данной постановке учитывались следующие важные факторы: зазор в болтовых соединениях, силы трения между контактирующими поверхностями, предварительная затяжка болтовых соединений, наличие уплотнительных шайб состоящих из полимерных материалов, а также учета гофрированной формы применяемых панелей. На основе математических моделей напряженно-деформированного состояния оболочечных, стержневых и пластинчатых конструкций в работе разработана математическая модель, которая учитывает влияние продольных сил и геометрической нелинейности в целом на НДС составленных тонкостенных конструкций. При этом предложена процедура осреднения продольных усилий, действующей в сечении стержня. В результате система связанных дифференциальных уравнения преобразуется к дифференциальному уравнению и интегральному соотношению. Для решения задачи об определении НДС составного стержня выбран метод конечных разностей. Получены результаты решения ряда прикладных задач. Установлены закономерности изменения напряженно-деформированного состояния тонкостенных конструкций на примере металлических бункеров при варьировании проектно-технологических параметров. Экспериментально определен характер поведения системы полос, соединенных болтовым крепежом с зазором, нагруженных равномерно по верхней кромке поперечным циклическим усилием. Проведено сравнение полученных численных результатов исследований с полученными экспериментальными данными. Подтверждено качественное и количественное соответствие результатов численных и экспериментальных исследований изменения прогибов системы полос.
Thesis for the degree of Candidate of technical Sciences in specialty 05.02.09 – dynamics and strength of machines. National technical University "Kharkiv Polytechnic Institute", Ministry of Education and Science of Ukraine, Kharkiv, 2016. The thesis is devoted to the development of approaches, methods and models to study structural strength of composite thin-walled engineering structures with bolted elements. This work is solves the problem of analysis of the stress-strain state of composite thin-walled engineering structures with bolted elements, as well as its implementation and determination of the distribution of deflections, displacements and longitudinal efforts. Also in this formulation the following important factors were taken into account: the gap in bolted joints, friction force between the contacting surfaces, the pre-tightening of bolted connections, the presence of polymeric materials, as well as consideration of the corrugated shape of panels used. On the basis of mathematical models of the stress-strain state of the shell, the rod and plate structures, a mathematical model that takes into consideration the influence of axial forces and geometric nonlinearity in general on stress-strain state of composed thin-walled structures was elaborated in this thesis. The results of solving some applied problems were obtained. The regularities of changes of stress-strain state of thin-walled engineering structures at variation of design and process parameters were defined.
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44

Bai, Ruqing. "Numerical modeling of isotropic and composites structures using a shell-based peridynamic method." Thesis, Compiègne, 2019. http://www.theses.fr/2019COMP2482.

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Анотація:
Le travail de thèse porte sur de nouveaux compléments et améliorations pour la théorie de la péridynamique concernant la modélisation numérique de structures minces telles que les poutres et les plaques, les composites isotropes et multicouches soumis à un chargement dynamique. Nos développements ont principalement porté sur l'exploration des possibilités offertes par la méthode péridynamique, largement appliquée dans divers domaines de l'ingénierie où des discontinuités fortes ou faibles peuvent se produire, telles que des fissures. La procédure de généralisation de la méthode Peridynamics pour la modélisation des structures de poutres de Timoshenko et des structures de plaques de Reissner-Mindlin avec une large plage de rapport épaisseur sur longueur allant de structures épaisses à très minces est indiquée. Et un impact avec une faible vitesse simplifié basé sur le modèle péridynamique développé pour la poutre de Timoshenko et la plaque de Reissner-Mindlin a été proposé en utilisant une procédure de contact spécifique pour l'estimation « naturelle » de la charge d'impact. L’originalité de la méthode actuelle réside dans l’introduction avec deux techniques permettant de réduire le problème de blocage par cisaillement qui se pose dans les structures à poutres et à plaques minces, à savoir la méthode d’intégration réduite (ou sélective) et la formulation mixte. Le modèle péridynamique résultant pour les structures de poutre de Timoshenko et les structures de plaque de Reissner-Mindlin est efficace et ne souffre d'aucun phénomène de verrouillage par cisaillement. En outre, la procédure de généralisation de la méthode péridynamique pour la modélisation de structures composites minces renforcées par des fibres est introduite. L’approche péridynamique pour la modélisation d’une couche est d’abord validée en quasi-statique, ce qui inclut des problèmes de prévision de la propagation de fissures soumis à des conditions de chargement mécaniques. La méthode péridynamique a ensuite été étendue à l’analyse de structures composites minces renforcées par des fibres utilisant la théorie fondamentale d’une couche. Enfin, plusieurs applications impliquant des structures composites minces renforcées par des fibres et des résultats numériques ont été validées par comparaison à la solution FEM obtenue à l'aide d'un logiciel commercial ou à des solutions de référence de la littérature. Dans toutes les applications, Péridynamics montre que les résultats correspondent parfaitement aux solutions de référence, ce qui prouve son potentiel d’efficacité, en particulier pour la simulation de chemins de fissures dans les structures isotropes et composites
This thesis introduces some new complements and improvments for the Bond-Based Peridynamics theory concerning the numerical modeling of thin structures such as beams and plates, isotropic and multilayer composites subjected to dynamic loading. Our developments have been focused mainly on exploring the possibilities offered by the Peridynamic method, which has been widely applied in various engineering domains where strong or weak discontinuities may occur such as cracks or heterogeneous media. The generalization procedure of the Peridynamics method for the modeling of Timoshenko beam structures and Reissner-Mindlin plate structures respectively with a wide range of thickness to length ratio starting from thick structures to very thin structures is given. And A simplified low velocity impact based on the developed Peridynamic model for Timoshenko beam and ReissnerMindlin plate has been proposed by using a specific contact procedure for the estimation of the impact load. The originality of the present method was the introduction for the first time of two techniques for the alleviation of the shear locking problem which arises in thin beam and plate structures, namely the reduced (or selective) integration method and mixed formulation. The resulting Peridynamic model for Timoshenko beam structures and Reissner-Mindlin plate structures is efficient and does not suffer from any shear locking phenomenon. Besides, the generalization procedure of Peridynamic method for the modeling of fiber-reinforced thin composite structures is introduced. The Peridynamic approach for the modeling of a lamina is firstly validated in the quasi-statics including a crack propagation prediction problems subjected to mechanical loading conditions and then the Peridynamic method was further extended to analyze fiber-reinforced thin composite structures using the fundamental lamina theory. Finally, several applications involving fiber-reinforced thin composite structures and numerical results were validated by comparison to the FEM solution obtained using commercial software or to reference solutions from the literature. In all applications, the Peridynamics shows that results are matching perfectly the reference solutions, which proves its efficiency potentiality especially for crack paths simulation in isotropic and composite structures
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45

Атрошенко, Олександр Олександрович. "Аналіз конструкційної міцності складених тонкостінних конструкцій з болтовим з'єднанням елементів". Thesis, НТУ "ХПІ", 2016. http://repository.kpi.kharkov.ua/handle/KhPI-Press/21789.

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Анотація:
Дисертація на здобуття наукового ступеня кандидата технічних наук за спеціальністю 05.02.09 – динаміка та міцність машин. Національний технічний університет "Харківський політехнічний інститут", Міністерство освіти і науки України, Харків, 2016. Дисертація присвячена розробці підходів, методів і моделей для дослідження конструкційної міцності складених тонкостінних машинобудівних конструкцій з болтовим з'єднанням елементів. У роботі розв'язана задача аналізу напружено-деформованого стану складених тонкостінних машинобудівних конструкцій з болтовим з'єднанням елементів, а також його реалізація і визначення закономірностей розподілу прогинів, зміщень і поздовжніх зусиль. Також в даній постановці ураховувались наступні важливі чинники: зазор у болтовому з'єднанні, сили тертя між контактуючими поверхнями, попереднє затягуванням болтових з'єднань, наявністю полімерних матеріалів, а також урахування гофрованої форми застосованих панелей. На основі математичних моделей напружено-деформованого стану оболонкових, стрижневих та пластинчатих конструкцій, в роботі розроблена математична модель, яка ураховує вплив поздовжніх сил і геометричної нелінійності в цілому на НДС складених тонкостінних конструкцій. Отримані результати розв'язання низки прикладних задач. Установленні закономірності зміни напружено-деформованого стану тонкостінних машинобудівних конструкцій при варіюванні проектно-технологічних параметрів.
Thesis for the degree of Candidate of technical Sciences in specialty 05.02.09 – dynamics and strength of machines. National technical University "Kharkiv Polytechnic Institute", Ministry of Education and Science of Ukraine, Kharkiv, 2016. The thesis is devoted to the development of approaches, methods and models to study structural strength of composite thin-walled engineering structures with bolted elements. This work is solves the problem of analysis of the stress-strain state of composite thin-walled engineering structures with bolted elements, as well as its implementation and determination of the distribution of deflections, displacements and longitudinal efforts. Also in this formulation the following important factors were taken into account: the gap in bolted joints, friction force between the contacting surfaces, the pre-tightening of bolted connections, the presence of polymeric materials, as well as consideration of the corrugated shape of panels used. On the basis of mathematical models of the stress-strain state of the shell, the rod and plate structures, a mathematical model that takes into consideration the influence of axial forces and geometric nonlinearity in general on stress-strain state of composed thin-walled structures was elaborated in this thesis. The results of solving some applied problems were obtained. The regularities of changes of stress-strain state of thin-walled engineering structures at variation of design and process parameters were defined.
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46

Wong, Chia-Ching, and 翁嘉慶. "The Application of Thin-walled Composite Beam Element." Thesis, 1997. http://ndltd.ncl.edu.tw/handle/59371868970524725935.

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碩士
國立成功大學
航空太空工程學系
85
The main purpose of the present here is to analysis thethin-walled composite beam structures by using the thin- walledcomposite beam finite element developed by Wu and Sun, and compare the results with experimental data. The element has twonodes, 10 degrees of freedom per node. And it is suitable for either open-section or closed section beams of any shape, stacking sequence and boundary condition.
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47

Khosravi, Peyman. "Nonlinear finite element analysis and design optimization of thin-walled structures." Thesis, 2007. http://spectrum.library.concordia.ca/975373/1/NR31149.pdf.

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In this study, an efficient, accurate and robust methodology for nonlinear finite element analysis and design optimization of thin-walled structures is presented. Main parts of this research are: formulation and development of an accurate and efficient shell element, a robust nonlinear finite element analysis technique, and an efficient optimization methodology. In the first part, a new three-node triangular shell element is developed by combining the optimal membrane element and discrete Kirchhoff triangle (DKT) plate bending element, and is then modified for laminated composite plates and shells so as to include the membrane-bending coupling effect. Also, a moderately thick shell element is developed in a similar manner by combining the discrete Kirchhoff-Mindlin triangular (DKMT) plate bending element and the optimal membrane element. Using appropriate shape functions for the bending and membrane modes of the element, the "inconsistent" stress stiffness matrix is formulated and the tangent stiffness matrix is determined. In the second part, a robust nonlinear finite element analysis program based on the corotational technique is developed to analyze thin-walled structures with geometric nonlinearity. The new element is thoroughly tested by solving few popular benchmark problems. The results of the analyses are compared with those obtained based on other membrane elements. In the third part, optimization algorithms based on the optimality criteria are developed and then combined with the nonlinear finite element analysis to optimize different types of thin-walled structures with geometric nonlinearity. The optimization problem considers the thickness or geometry design variables, and aims to maximize the critical load of the structure subject to constant total mass, or minimize the total mass subject to constant applied loads. The optimization results based on the developed design optimization algorithm are compared with those based on the gradient-based sequential quadratic programming method to demonstrate the efficiency and accuracy of the developed procedure. An application of the thickness optimization for locating the potential places to add the stiffeners in stiffened panels is also presented. Also a method is presented to efficiently incorporate the effects of local buckling and mode switching during optimization process for stiffened panels.
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48

Pon, Chen-Yann, and 彭成彥. "Nonprismatic Thin-walled Beam Analysis Model of the Differential Quadrature Element Method." Thesis, 1996. http://ndltd.ncl.edu.tw/handle/88025930688620846513.

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49

GU, BAO-DING, and 顧寶鼎. "Nonlinear finite element analysis of three-dimensional thin-walled beam-column members." Thesis, 1991. http://ndltd.ncl.edu.tw/handle/65803485129672350393.

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50

王海臨. "Vibration Analysis of Thin-walled Structures Using a Finite Element-Transfer Matrix Method." Thesis, 1997. http://ndltd.ncl.edu.tw/handle/11819611416192660942.

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