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Trabecular bone, rather than being considered as a homogeneous material, must be analysed as a structure of interconnected beam and plate-like elements. The arrangement and morphology of these elements depend on the specific tissue studied as well as on the physiology of the individual. It is therefore impossible to define the mechanical properties trabecular bone in general. To estimate the properties of an individual structure, flexible numerical models must be developed, which allow the calculation of elastic constants and resistance of tissue previously characterised by non-destructive observation. Voxel-based modelling of structures observed by X-ray microtomography is computation intensive. Here, synthetic 2D-microstructures are analysed, constructed as a collection of Voronoi-cells obtained from the observation of plane sections of cancellous bone. The effect of architecture (vertebra and femur), bone density and loss of trabecular connectivity was researched. The study confirms findings of earlier experimental and numerical studies relating to the effect of these parameters; the technique is efficient in terms of experimental effort and numerical analysis. Consequently, the use of synthetic microstructures based on a Voronoi-cell approximation of the real bone architecture may be a promising approach for the prediction of the mechanical properties of trabecular bone.

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Modern industry, such as in aerospace, automotive, biomedical and military fields, has adopted advanced manufacturing (such as particle sintering-like processes and other 3D printing) as a rapid and efficient alternative for manufacturing industrial parts. Also, state-of-the-art techniques in the civil engineering industry include 3D concrete printing and cement-based additive manufacturing processes. All these techniques invariably include thermally-active particles, such as sintering powders and functionalized cementitious materials. The purpose of this work is to present a thermo-mechanical model for the simulation of problems involving thermo-mechanically-active particles forming discrete particles systems in advanced manufacturing. Our approach is based on the Discrete Element Method (DEM), combined with lumped heat transfer equations to describe the various thermal phenomena that may take place for such systems. Particles' motion and their thermal states over time are computed under the influence of body (e.g., gravitational) forces, contact and friction forces (and the related moments w.r.t. the particles' centers), adhesive forces as well as applied heat from external devices, heat transfer through conduction (upon contact with other particles and objects), convective cooling and radiative effects. Phase transformation, which may be critical in certain applications, is also considered. A numerical scheme is presented for solution of the model's equations. We then develop direct, large-scale numerical simulations to illustrate the validity of the proposed scheme and its practical use to the simulation of modern advanced manufacturing processes.Keywords: Particles, thermo-mechanical effects, multiphysical particle systems, advanced manufacturing and 3D printing, discrete element method (DEM) v QUINTANA RUIZ, Osvaldo Dario. Um modelo acoplado termo-mecânico para a simulação de sistemas discretos de partículas em manufatura avançada. 2021. Num de Pág. 151 f. Tese (Doutor em Ciências) -

Este artigo propõe analisar a relação entre liberdade e governo através dos discursos e medidas governamentais implementadas no Brasil e na Argentina por ocasião da COVID-19. Para isso, considera duas variáveis que se tornaram relevantes à medida que a pandemia se desenvolveu: 1) a disjuntiva entre o “econômico” e a “saúde” e 2) os níveis nacional/federal, provincial/estadual e municipal de governo como cenários na luta contra a pandemia – analisando os casos específicos de São Paulo e Buenos Aires. O objetivo é compreender as experiências do Brasil e da Argentina com base nos conhecimentos, cálculos e nas técnicas de governo implementadas para garantir o difícil e frágil equilíbrio entre a liberdade individual e a segurança comum. O período de estudo está delimitado ao ano de 2020. Desta forma, esperamos contribuir para a análise das respostas que ambos os países deram à crise governamental durante o primeiro ano de pandemia, a partir da perspectiva das práticas e dos discursos governamentais.

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