No abstract

Elastomeric components are widely used in the engineering field since their mechanical properties can vary according to a specific condition, enabling their applications under large deformations and multiaxial loading. In this context, the present study seeks to investigate the main challenges involved in the finite element hyperelasticity simulation of rubber-like material components under different cases of multiaxial loading and precompression. The complex geometry of a conical rubber spring was chosen to deal with several deformation modes; this component is in the suspension system placed between the frame and the axle for railway vehicles. The framework of this study provides the correlation between axial and radial stiffness under precompression obtained by experimental tests in prototypes and virtual modeling obtained through a curve fitting procedure. Since the material approaches incompressibility, different shape functions were adopted to describe the fields of pressure and displacements according to the finite element hybrid formulation. The material parameters were accurately adjusted through an optimization algorithm implemented in Python program language which calibrates the finite element model according to the prototype test data. However, as an initial guess, the proper constitutive model and its parameters were first defined based only on the uniaxial tensile test data, since this test is easy to perform and well understood. The validation of the simulation results in comparison with the experimental data demonstrated that care should be given when the same component is subjected to different multiaxial loading cases.

Elastomeric bearing pads are responsible for transferring loads at the junction between beams and columns of bridges and viaducts, providing restrict freedom of movement in the superstructure. The elastomeric material of the bearing pad is a synthetic rubber reinforced with carbon black particles and subjected to a process of vulcanization, also represented by hyperelastic material models based on strain energy density functions. The objective of the present paper is to use the finite element analysis software Abaqus® to select the most appropriate hyperelastic model, as well as its constants, applying them in a bearing pad installed in an existing viaduct, evaluating its behavior and displacements resulting from the application of usual loads. The proposed methodology presents results coherent with technical specifications limits for available bearing pads products.

ABSTRACT. Structural optimization has received increasing attention in several different areas of engineering and has been identified as the most challenging and economically rewarding task in the field of structural design. In this context, the current paper proposes a methodology based on Evolutionary Structural Optimization (ESO) that corresponds to an evolutionary procedure applied for topological optimization in which the finite elements with the lowest stress levels are progressively removed from a structure. The optimization studies are applied for structures subjected to a transient dynamic response where different damping ratios are applied in the physical models, since its determination is extremely hard and can even change the structural stiffness in case of elastoplastic regime. Thus, a nonlinear behavior is considered to evaluate the effects for each damping ratio, and elastoplasticity theory for small strains is extended for a von Mises material with linear, isotropic work-hardening. For this purpose it is possible to evaluate a combination of different optimal topologies for the different damping ratios through an algorithm developed in the Python programming language. The stress levels present such a difference for each linear and nonlinear response, which characterizes a marked change in the structural stiffness of each analyzed model. Keywords: evolutionary structural optimization, dynamic response, damping, finite element method.Influência da taxa de amortecimento no projeto de otimização estrutural considerando análise dinâmica no domínio do tempo RESUMO. A otimização estrutural vem recebendo cada vez mais atenção em diversas áreas da engenharia e tem sido identificada como um dos maiores desafios em projeto estrutural. Neste contexto, o presente trabalho propõe uma metodologia baseada na Otimização Estrutural Evolucionária (ESO) que corresponde a um procedimento evolutivo aplicado em otimização topológica em que os elementos finitos com os mais baixos níveis de tensão são progressivamente removidos da estrutura. Os estudos de otimização são aplicados em estruturas sujeitas a uma resposta dinâmica transitória, e diferentes taxas de amortecimento são aplicadas nos modelos físicos, pois a sua determinação é extremamente difícil, podendo inclusive, alterar a rigidez da estrutura em casos de regime elastoplástico. Assim, o comportamento não linear é considerado a fim de se avaliar os seus efeitos para cada taxa de amortecimento, e a teoria da elastoplasticidade para pequenas deformações é estendida a um material de von Mises com encruamento isotrópico linear. Com este propósito é possível avaliar uma combinação das topologias ótimas distintas para as diferentes taxas de amortecimento através de um algoritmo desenvolvido em linguagem de programação Python. Os níveis de tensões apresentaram diferenças significativas para respostas linear e não linear, caracterizando acentuada alteração na rigidez estrutural dos modelos analisados.Palavras chave: otimização estrutural evolucionária, resposta dinâmic...