Resumo em Inglês:

Abstract The main goal of the present paper is to develop a mathematical framework for modeling the field equations arising in the problem of an elastic, isotropic, non-saturated porous media (pores filled with air and water) within the context of Eshelbian mechanics. The global balance of pseudomomentum is performed in a fully material manifold to account for the configurational forces due to material inhomogeneities, involving the Maxwell stress tensor. Biot’s momentum conservation equations in a dilute scheme for a micromechanical environment, combined with the Mori–Tanaka homogenization theory, are employed for the geomechanical solution. In the mathematical description, pores are treated as Eshelby inhomogeneous inclusions within a solid skeleton, making them the source of configurational forces. The resulting field equations show that these configurational forces evolve in a strongly nonlinear manner due to their dependence on the nature of the pores as well as the soil's mechanical properties. This behavior was numerically observed through the implementation of the boundary value problem using the Finite Element Method

Resumo em Inglês:

Abstract This study investigates the numerical modeling of failure mechanisms in reinforced concrete (RC) beams using the phase-field method, emphasizing its capability to simulate complex fracture behaviors under various loading conditions. The model incorporates a fourth-order degradation tensor to account for tensile, shear, and tensile-shear crack initiation and propagation. Six beam configurations from Marzec and Tejchman's experiments were modeled, varying dimensions, reinforcement ratios, and spans. The numerical results, obtained through finite element analyses, were compared with experimental data, revealing the model's accuracy in capturing crack patterns, failure mechanisms, and load-displacement responses. Key findings include the transition of failure modes from flexural to shear-dominated as beam slenderness decreases, consistent with experimental observations. Despite some discrepancies in peak load predictions, the phase-field model showed its potential for robust analysis of RC beam behavior, offering insights into fracture evolution and structural performance.

Resumo em Inglês:

Abstract Shape Memory Alloys (SMAs) are materials known for their thermomechanical coupling associated to phase transformation processes. When subjected to stresses, SMAs exhibit nonlinear characteristics, necessitating special methodologies to assess their performance and structural integrity. The design of mechanical components with geometric discontinuities, such as notches and holes, has traditionally been addressed through simplified mechanical design methods incorporating stress concentration factors (SCFs). These approaches are applied under both static and cyclic mechanical or thermal loading conditions. The presence of plastic deformations introduces stress/strain redistribution and nonlinearities effects such as plasticity. In this work the stress concentration in SMA pseudoelastic thin plates with holes is investigated through numerical simulations and experimental tests. The numerical model is based on finite elements method using a SMA constitutive model to represent the pseudoelastic behavior and plasticity is calibrated from experimental results obtained from tension tests with the Digital Image Correlation (DIC) method. The numerical results present the effect of stresses and martensitic volume fractions and the strain decomposition results considering elasticity, phase transformation and plasticity. An experimental-numerical calibration is performed with good agreement. The DIC results present a Lüders type strain related to the preferential transformation pattern. The stress concentration factors are calculated from numerical results and show a variation of its value according to the stage of phase transformation and plasticity. The study presents a proposal of a method to consider the effect of geometry and material properties and load history on the design of mechanical components.

Resumo em Inglês:

Abstract This paper investigates the vibration attenuation performance of periodic foundations for surface structures. A numerical method is proposed, which considers one- or two-dimensional linear-elastic bodies under time-harmonic external load and seismic excitation. These bodies are modeled via the Finite Elements Method, while their supporting soil is modeled as a homogeneous half-space via the Indirect Boundary Element Method. Coupling between the methods is obtained by imposing direct continuity and equilibrium conditions at the interface. Three different configurations of foundations are studied: 1) no foundation, 2) homogeneous foundation, and 3) sandwich foundation – two materials layered in an alternate fashion. Material properties and thickness of the layers are selected to induce prescribed bandgaps in the response of the structure. The results are presented in terms of data that can be directly applied in engineering practice.

Resumo em Inglês:

Abstract This study explores the efficacy of 2D Digital Image Correlation (DIC) for material characterization of titanium spinal rods, particularly under large strain conditions. The research aims to address the lack of comprehensive material data by performing tensile tests of cylindrical specimens and applying 2D digital image correlation to derive the true stress-strain curve during plastic deformation, assuming negligible out-of-plane displacements and adopting Gromada’s coefficient of correction for triaxial stress state. The verification process includes a direct comparison with available manufacturer and literature specifications, as well as an experimental four-point bending test in conjunction with a numerical model for comparative analysis. Results demonstrate that 2D DIC, with adjustments for triaxial stress states, can reliably determine material properties, showing less than 5% deviation from established literature values. The findings advocate for the cost-effective use of 2D DIC as a promising tool for enhancing the accuracy of finite element models, especially in applications involving large deformation.

Resumo em Inglês:

Abstract This paper presents a comparative study of stochastic Kriging-based optimization algorithms applied to a generic infrastructure planning problem, using direct policy search (DPS) as a heuristic approach. The evaluated problem is a sequential decision problem involving a generic infrastructure planning scenario under uncertainty, with performance dependent on system and cost model parameters. The focus is to compare the impact of heterogeneous noise treatment in an optimization framework, approaching three algorithms: Minimum Quantile criterion (MQ), stochastic Efficient Global Optimization (sEGO), and Expected Improvement with Reinterpolation (EIR). The MQ algorithm is the only one that does not address information about the noise variance of the stochastic parameter. The results demonstrate that the algorithms presented satisfactory performance, especially those with heterogeneous noise treatment, and show potential for solving complex infrastructure engineering planning problems under uncertainties in a DPS framework.