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Experimental and numerical analysis of 3D printed cement mortar specimens using inkjet 3DP

Shakor Pshtiwan, Gowripalan Nadarajah, Rasouli Habib

Archives of Civil and Mechanical Engineering

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2021

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Vol. 21, no. 2

287--302

EN

Investigations involving the experimental and numerical analysis of inkjet (powder-based) 3DP are relatively limited for cement mortar materials. This study, by using cement mortar specimens, aimed to determine the optimum strength of 3D printed structural members in all three planes by identifying the compressive strength of cubes, the modulus of elasticity and Poisson’s ratio. In addition, this study aimed to analyse and verify the numerical model for 3D printed cementitious mortar (CP) prisms and beams using an inkjet 3D printer by considering the mechanical behaviour of the printed prisms under compression. Robust and optimal mechanical properties of the 3D printed cementitious mortar obtained from laboratory testing were utilised in the simulation of structural components using ABAQUS software. As inputs for simulation, the strength properties of the printed objects in all three cartesian planes were obtained from test results. The obtained results showed that the printed cementitious materials have orthotropic properties and that the results of experiments were consistent with the analytical solutions and hypothesised model for the different geometric shapes. This finding is extremely valuable in determining the optimum features of 3D printed structures.

2

Eksperymentalno-numeryczna analiza ortotropii pianki stosowanej jako rdzeń w płytach warstwowych

Głowacki B., Chuda-Kowalska M.

Materiały Budowlane

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2017

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nr 1

68--69

3

Transient thermal analysis of functionally graded shallow shells by the MLPG

Sladek J., Sladek V., Solek P.

Computer Methods in Materials Science

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2009

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Vol. 9, No. 2

171-177

EN

In recent years the demand for construction of huge and lightweight shell and spatial structures is increasing. To minimize the weight of shell structures a layered profile of the shell is utilized frequently. In such a case a delaminating of individual layers may occur due to a jump change of the material properties. To remove this phenomenon the functionally graded materials (FGMs) has been introduced recently. FGMs are multi-phase materials with a pre-determined property profile, where the phase volume fractions are varying gradually in space. This results in continuously nonhomogenous material properties at the macroscopic structural scale. Often, these spatial gradients in the material behaviour render FGMs as superior to conventional composites because of their continuously graded structures and properties. FGMs may exhibit isotropic or anisotropic material properties, depending on the processing technique and the practical engineering requirements. Many linear bending studies are focused only to a lateral pressure load with assumption of uniformly distributed temperature in the whole shell. However, in shells with FGM properties the role of thermal loading is more imperative. Therefore, it is interesting to analyze shells under a general thermal load. Literature sources on this subject are poor and they are mostly restricted to analyses of plates. Due to the high mathematical complexity of the boundary or initial-boundary value problems, analytical approaches for FGMs are restricted to simple geometry and boundary conditions. The choice of an appropriate mathematical model together with a consistent computational method is important for such kind of structures. Most significant advances in shell analyses have been made using the finite element method (FEM). It is well known that numerical results by standard displacement-based type shell element are over stiff with yielding the shear locking phenomena in thin shells. Locking problems arise due to inconsistencies in discrete representations of the transverse shear energy and the membrane energy. The boundary element method (BEM) has emerged as an alternative numerical method to solve plate and shell problems. It is a very powerful computational method if a fundamental solution is available for considered problem. However, the fundamental solution for a thick orthotropic shell wit continuously varying material properties is not available according to the best of the author?s knowledge. Meshless approaches for solution of problems of continuum mechanics have attracted much attention during the past decade. One of the most rapidly developed meshfree methods is the Meshless Local Petrov-Galerkin method (MLPG). The solution of the uncoupled problem in the present paper is split into two tasks. In the first task the temperature distribution in the shell has to be obtained by solving the diffusion equation. The temperature distribution in shell has to be analyzed as 3-D problem. The MLPG is applied to transient heat conduction equations in a continuously nonhomogeneous solid. The Laplace transform technique is used to eliminate the time variable. Several quasi-static boundary value problems must be solved for various values of the Laplace-transform parameter. The Stehfest?s inversion method is applied to obtain the time-dependent solution. In the second task, the set of governing differential equations for Reissner-Mindlin shell bending theory with Duhamel-Neumann constitutive equations is solved. Since thermal changes in solids are relatively slow with respect to elastic wave velocity, the inertial terms in Reissner-Mindlin governing equations are not considered. The problem is considered as quasi-static with time dependent thermal forces. The MLPG method is applied again to solution of that problem with the meshless Moving Least-Squares (MLS) approximation of primary field variables. The nodal points are spread freely in the analyzed domain and on its boundary. The essential boundary conditions are satisfied by collocation of approximated fields at nodes with prescribed values. In other nodes, the governing PDEs are considered on subdomains around these nodes in the local weak-form with using unit test functions. The resulting local integral equations are discretized within the assumed approximation of field variables. Numerical results for simply supported and clamped square shells are presented to illustrate the efficiency of the present computational method.

PL

Tematem niniejszej pracy jest wykorzystanie lokalnej beziastkowej metody Petrova-Galerkina (MLPG) do problemu odkształceń termicznych powłok Reissnera-Mindlina. W studium wykorzystano model funkcjonalnych materiałów gradientowych z założeniem ciągłej zmiany własności na grubości elementu powłokowego. Forma słaba równań występujących w teorii Reissnera-Mindlina została przeniesiona na zbiór równań całkowych rozwiązywanych w obszarze zdefiniowanych poddomen. Cylindryczne poddomeny losowo otaczają wygenerowane punkty węzłowe. W rozwiązaniu wykorzystano beziatkową aproksymację metody Moving Least-Squares (MLS).

4

Wpływ przyjęcia ortotropowych własności materiału na rozkłady naprężeń i odkształceń w kości miednicy człowieka

John A., Kokot G.

Zeszyty Naukowe Katedry Mechaniki Stosowanej / Politechnika Śląska

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2003

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z. 20

182-187

PL

W procesie modelowania numerycznego kości miednicy człowieka istotną rolę odgrywa etap przyjęcia modelu ośrodka i zadawania stałych materiałowych. Dotychczas, w większości aplikacji numerycznych, w ujęciu makro, traktuje się kość jako ośrodek izotropowy, liniowo-sprężysty. Mimo uproszczenia, jest to jedyne efektywne podejście ze względu na brak danych doświadczalnych. Dane dotyczące ortotropowych własności tkanki kostnej można znaleźć w literaturze, dotyczą one jednak kości długich. Opierając się na danych literaturowych w niniejszej pracy podjęto próbę zbadania wpływu ortotropowych własności materiałowych tkanki kostnej w obszarze okołopanewkowym na rozkład naprężeń i odkształceń w kości miednicy człowieka.

EN

Numerical modeling of the human pelvic bone is a complex process which needs take into account many important problems. There are very important: geometrical model, boundary conditions, load and material properties. Up to now, in numerical applications, the bone tissue is assumed as an isotropic, linear elastic material. It is a simplification, but it arises from the numerical possibilities and available data and it is the only effective solution of the problem in macro scale. A certain data, concerning orthotropic material properties of the bone tissue, is a accessible in literature, but it concern tibia bone, not pelvic bone. In this paper, on the ground of available data, atest of the influence of anisotropic material properties on the stress and strain distribution in pelvic bone is presented.