Abstract. The graphical user interface (GUI) in usual engineering problems, has facilitated the modeling as well as provides greater flexibility in meshing, boundary conditions and physical properties by employing visual tools, improving... more
Abstract. The graphical user interface (GUI) in usual engineering problems, has facilitated the modeling as well as provides greater flexibility in meshing, boundary conditions and physical properties by employing visual tools, improving the analysis interpretation. However, with the need for more efficient computational implementations - less computational effort and shorter analysis, the boundary element method (BEM) comes as efficient and flexible suggestion, allowing greater versatility to the geometric modeling and meshing programs. The BEM stands out among the other numerical methods due to discretization criterion of the model adopted, in the case it occurs only on the boundary thereof, making simple and versatile implementation. In this context, this work proposes the development of a graphical interface program easy user handling for pre-processing, called BEMLAB2D and implemented in MATLAB for two-dimensional models analysis with BEM, which allows modelling complex geometr...
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Abstract. The stress analysis structures with complex geometry where it is continuously amended by the crack growth, as in aircraft fuselages, usually requires the employment of numerical methods, since the presence of cracks in the... more
Abstract. The stress analysis structures with complex geometry where it is continuously amended by the crack growth, as in aircraft fuselages, usually requires the employment of numerical methods, since the presence of cracks in the structure raises difficulties for the modelling and, therefore, the calculation of the stress intensity factors. Therefore, both the finite element method (FEM) and the boundary element method (BEM) have been applied in this type of analysis, with a slight advantage for the BEM due it does not require continuous remeshing, whenever the crack spreads. Here, the BEM will be used in the treatment of modelling crack considering two independent boundary integral equations, known as dual boundary element method (DBEM): the displacement equation applied for collocation on one of the crack boundary and remaining boundaries, and the traction equation applied for collocation on the opposite crack boundary. Moreover, boundary continuous and discontinuous quadratic ...
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This chapter presents a new alternative approach to the analysis of the fatigue life of aircraft fuselage parts considering the compliance of internal elements to replace the classical model of critical crack size. In this case, from a... more
This chapter presents a new alternative approach to the analysis of the fatigue life of aircraft fuselage parts considering the compliance of internal elements to replace the classical model of critical crack size. In this case, from a global–local analysis using the boundary element method (BEM), induced stresses at a macro model, and their effects on micro models are evaluated. The BEM enables efficient simulations of the propagation of initial defects to assess the damage tolerance. For this purpose, computational techniques were developed that allowed evaluating these models, through a probabilistic treatment to assess damage tolerance and fatigue life. Finally, this technique is shown as an alternative to ensure the integrity and proper operation of fuselage panels avoiding reaching a Limit State during its projected lifespan.
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Allying the interactivity computing environments and conducting practical activities inacademic disciplines is an important complement thetheoretical part of these, besides giving students the understanding and fixing of concepts learned.... more
Allying the interactivity computing environments and conducting practical activities inacademic disciplines is an important complement thetheoretical part of these, besides giving students the understanding and fixing of concepts learned. Thus, the concepts communicated in lectures in an interactive and visual between teacher and students and associated with situations abstracted from reality, makes the classes more productive and motivating. On the other hand, Computer Graphics has proved substantially as important support tool in the development of computer programs and interactive communication as a vehicle for teaching purposes. Thus, this paper presents the development of an interactive visualComputing Platform, written in JAVA, enabling closer and address the problem of physical form as real as possible, as well as assist learning and understanding the External Equilibrium in two dimensions. Application examplesillustrate and validate the platform. Index Terms - data modeling,...
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Abstract. The Fracture Mechanics has become an important analytical tool in the design and subsequent operation in structures that may develop cracks during their service life. In this regard, and based on the principle of linear elastic... more
Abstract. The Fracture Mechanics has become an important analytical tool in the design and subsequent operation in structures that may develop cracks during their service life. In this regard, and based on the principle of linear elastic fracture mechanics (LEFM) and the knowledge of their stress intensity factors (FITs), this paper proposes numerically evaluate these factors from the use of two analysis programs: the well-established ABAQUS CAE package for analysis with finite element method (FEA) and an academic program called emCracker2D still under testing, using a formulation based on the dual boundary element method (DBEM) and the J-integral technique for calculating the FITs. The latter is based on object-oriented programming and written in C++ language, having an interface with MATLAB for treatment of modeling, meshing and viewing results. This work is limited to the application and use of BemCracker2D program to obtain the stress factors as proposed, and will not be address...
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One of the main advantages of the Boundary Elements Methods (BEM) is the inherent feature of a Boundary Representation scheme (B-Rep),since it represents the geometry and physical properties of a model using just its boundary. This... more
One of the main advantages of the Boundary Elements Methods (BEM) is the inherent feature of a Boundary Representation scheme (B-Rep),since it represents the geometry and physical properties of a model using just its boundary. This characteristic makes the representation andmanipulation of the model geometry an easy task, also allowing the boundary element mesh generation in a straightforward and simple way.Even though a simple pre-processor program may suffice for generating most two-dimensional boundary element models, in some specialcases the modeling procedure represents a cumbersome task, requiring pre-processor programs with enhanced characteristics. The specialcases considered in this work are non-trivial models, such as geometries with infinite or semi-infinite domains, multiple regions, disconnectedregions, cracks and holes. To handle with the modeling task of these special models, the present development proposes a scheme based onthe well-known Half-Edge data structure (HE...
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Over the years several design philosophies to fatigue developed in order to combine structural safety and economy to manufacturing and operating aircraft process. The safe-life approach, which consists of designing and manufacturing a... more
Over the years several design philosophies to fatigue developed in order to combine structural safety and economy to manufacturing and operating aircraft process. The safe-life approach, which consists of designing and manufacturing a safe aeronautical structure throughout its useful life, results in factors that oversize the structural elements, preventing the possibility of failure and evidently leading to high design costs. On the other hand, the approach based on the damage tolerance concept, in which it is assumed that the structure, even whether damaged, is able to withstand the actions for which it was designed until the detection of a crack due to fatigue or other defects during its operation. Here, we propose a new methodology to the damage tolerance problem in which two-dimensional global-local analysis at different levels of external requests will be made by means of compliance, aimed at finding a relationship between fatigue life and the Paris constant. Moreover, the Bem...
Purpose The purpose of this paper is to describe further developments on a novel formulation of the boundary element method (BEM) for inelastic problems using the dual reciprocity method (DRM) but using object-oriented programming (OOP).... more
Purpose The purpose of this paper is to describe further developments on a novel formulation of the boundary element method (BEM) for inelastic problems using the dual reciprocity method (DRM) but using object-oriented programming (OOP). As the BEM formulation generates a domain integral due to the inelastic stresses, the DRM is employed in a modified form using polyharmonic spline approximating functions with polynomial augmentation. These approximating functions produced accurate results in BEM applications for a range of problems tested, and have been shown to converge linearly as the order of the function increases. Design/methodology/approach A programming class named DRMOOP, written in C++ language and based on OOP, was developed in this research. With such programming, general matrix equations can be easily established and applied to different inelastic problems. A vector that accounts for the influence of the inelastic strains on the displacements and boundary forces is obta...
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Este trabalho visa dar continuidade a estudos inelásticos anteriores, nos quais a análise de problemas viscoelásticos é realizada através do Método dos Elementos de Contorno (MEC) com o Método de Reciprocidade Dual (MRD). Aqui, o MEC é... more
Este trabalho visa dar continuidade a estudos inelásticos anteriores, nos quais a análise de problemas viscoelásticos é realizada através do Método dos Elementos de Contorno (MEC) com o Método de Reciprocidade Dual (MRD). Aqui, o MEC é aplicado em análise de ...