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.

Thesis (M.S.)--Brigham Young University. School of Technology, 2005. / Includes bibliographical references (p. 77-79).

This work was created in cooperation with company Mubea. Introduction part describes purpose of automotive headrest and function of special grooves, which are fitted on headrest frame. Overview of manufacturing technologies of these grooves with short summary of their advantages and disadvantages follows. The main part of this work consists of development of new alternative technology for manufacture special grooves in thin-walled tubes with following experimental verification of technological conditions and shape of grooves. This work also contains evaluation of tool life and wear. Interpretation of the results is performed by calculations and graphically.

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.

This master's thesis is focused on the modeling and tracks of thin-walled components. Used softwares are CATIA V5R20 from Dassault Systemes for Experimental Component Modeling and PowerMILL 2018 from Autodesk for Draw and NC Programming. The production efficiency between the precision casting and the workpiece of the cube blank based on the material utilization factor and machining time is compared in this work.

The diploma thesis deals with the production of spacious thin-walled castings of aluminum alloys with a good surface quality. During the casting process, different types of molding sands and aluminum alloys are used. The target of the diploma thesis is to evaluate the casting surface quality, to analyse the defects and to evaluate the results.

This diploma thesis deals with issues in machining of thin-walled components. Its first part describes materials used in the aircraft industry. Then it focuses on issues associated with the prediction of deflections of a rib wall during machining. Later on it focuses on different methods and strategies of thin-walled part milling. The diploma thesis also describes an experiment of manufacturing thin-walled components in the form of ribs and evaluation parameters such as roughness, perpendicularity and straightness deviations, width of the rib and force loading of a cutting tool as measured by various gages. The final part is devoted to a calculation of the specific cutting force and its comparison with its theoretical value.

<p>U radu su izvedene diferencijalne jednačine tankozidnog kompozitnog štapa proizvoljnog poprečnog preseka, primenom principa virtualnih pomeranja, a polazeći od funkcije deplanacije koju je predložio A. Prokić, za tankozidne štapove homogenog poprečnog preseka. Ona omogućava jedinstvenu analizu tankozidnih štapova otvorenog i zatvorenog poprečnog preseka, pretpostavka o zanemarenju klizanja u srednjoj površi štapa nije<br />neophodna, pa se smičući naponi određuju direktno iz odgovarajućih deformacija. Raspodela normalnih napona nije više određena sektorskom koordinatom već parametrima pomeranja čvornih tačaka, i u opštem slučaju je promenljiva od preseka do preseka, što omogućuje registrovanje i analizu shear lag uticaja, koji se klasičnom teorijom tankozidnih nosača ne može opisati. Kao što je poznato, shear lag uticaj predstavlja neravnomernu<br />raspodelu normalnih napona u pojasevima, s tim što se maksimalna vrednost javlja na mestu spoja pojasa sa rebrima, i u opštem slučaju je veća od vrednosti napona koja se dobija klasičnom teorijom savijanja štapova zasnovanoj na Bernoullijevoj hipotezi. To je posebno izraženo kod štapova napregnutih na savijanje kod kojih dolazi do značajne deplanacije poprečnog preseka.<br />Dobijeni sistem diferencijalnih jednačina se ne može rešiti u zatvorenom obliku te se pristupilo numeričkoj metodi, odnosno primeni metode konačnih elemenata. Definisana su dva tipa elementa sa različitim polaznim pretpostavkama. Prvi tip elementa zasnovan je na teoriji Timoshenka, odnosno uticaj transverzalnih sila na deformaciju se uzima u obzir. Drugi tip elementa zanemaruje uticaj transverzalnih sila na deformaciju, odnosno usvaja se pretpostavka da poprečni preseci i nakon deformacije ostaju ravni i upravni<br />na srednju liniju štapa. Kao dokaz tačnosti prethodno izvedenih teorijskih razmatranja urađen je niz primera pomoću programa napisanog u programskom jeziku C.</p> / <p>Differential equations of thin-walled composite beams of arbitrary cross section were<br />derived, using the principle of virtual displacements and starting from function of deplanation suggested by A. Prokic, for thin-walled beams of homogeneous cross section. It enables unique analysis thin-walled beams of open and closed cross section, assumption of neglecting shear strain in the middle surface is not necessary and shear stresses can be calculated directly from the strains. Distribution of longitudinal stresses is not defined by warping function, but parameters of longitudinal displacement, and in general case it is variable of section to section, that enables registering and analysis of shear lag, which classical theory of thin-walled beams is unable to reflect. As it is known, shear lag effect presents a non-uniform distribution of normal stresses in the flanges, maximal values are on the connection of flange and web, in general case it is larger from the value of stress obtained by classical theory of beams based on the Bernoulli hypothesis. It is especially<br />expressed at beams subjected to bending where deplanation of cross section is significant. Derived system of differential equations can not be solved in closed form solution and it was accessed to numerical method, respectively on the finite element method. Two types of element with different starting settings were defined. First type of element is based on the theory of Timoshenko, apropos the influence of transversal forces on deformation were taken into account. The second type of element neglects influence of transversal forces on deformation, concerning assumption that cross section remain plane and orthogonal on the middle line is adopted. A number of numerical examples are calculated by a computer program written in program language C as a proof of accuracy of previously derived theoretical reviews.</p>

Indiana University-Purdue University Indianapolis (IUPUI) / Thin-walled structures find wide applications in the automotive industry as energy absorption devices. A great deal of research has been conducted to design thin-walled structures, where the main objective is to reduce peak crushing forces and increase energy absorption capacity. With the advancement of computers and mathematics, it has been possible to develop 2D patterns which when folded turn into complex 3D structures. This technology can be used to develop patterns for getting structures with desired properties. In this study, square origami tubes with folding pattern (Yoshimura pattern) is designed and studied extensively using numerical analysis. An accurate Finite Element Model (FEM) is developed to conduct the numerical analysis. A parametric study was conducted to study the influence of geometric parameters on the mechanical properties like peak crushing force, mean crushing force, load uniformity and maximum intrusion, when subjected to dynamic loading. The results from this analysis are studied and various conclusions are drawn. It is found that, when the tube is folded with the pattern having specific dimensions, the performance is enhanced significantly, with predictable and stable collapse. It is also found that the stiffness of the module varies with geometrical parameters. With a proper study it is possible to develop origami structures with functionally graded stiffness, the performance of which can be tuned as per requirement, hence, showing promising capabilities as an energy absorption device where progressive collapse from near to end impact end is desired.

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