Effect of the interfacial area measurement parameters on the push-out strength between fiber post and dentin

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Nonoxidative thermal degradation kinetic of polyamide 6,6 reinforced with carbon nanotubes

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Crude Glycerin associated with starch or fiber-based energy ingredients at two levels of concentrate for beef cattle

Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP)

Purification and biochemical characterization of an alkaline pectin lyase from Fusarium decemcellulare MTCC 2079 suitable for Crotolaria juncea fiber retting

An extracellular pectin lyase secreted by Fusarium decemcellulare MTCC 2079 under solid state fermentation condition has been purified to electrophoretic homogeniety by using ammonium sulfate fractionation, carboxymethyl cellulose and gel filtration (Sephadex G-100) column chromatographies. The purified enzyme showed single protein band corresponding to molecular mass 45 +/- 01 kDa on sodium dodecyl sulfate polyacrylamide gel electrophoresis. The enzyme had maximum activity at pH 9.0 and showed maximum stability in the pH range of 9.0-12.0. The optimum temperature of the purified enzyme was 50 degrees C and it showed maximum stability upto 40 degrees C. The energy of activation for the thermal denaturation (Ea) was 59.06 kJ mol(-1) K-1. The K-m and k(cat) values using citrus pectin as the substrate were 0.125mgml(-1) and 72.9 s(-1) in 100mM sodium carbonate buffer pH 9.0 at 50 degrees C. The biophysical studies on pectin lyase showed that its secondary structure belongs to alpha+beta class of protein with comparatively less of beta-sheets. Purified pectin lyase showed efficient retting of Crotolaria juncea fibers.

Nonlinear formulation based on FEM, Mazars damage criterion and Fick's law applied to failure assessment of reinforced concrete structures subjected to chloride ingress and reinforcements corrosion

Structural durability is an important design criterion, which must be assessed for every type of structure. In this regard, especial attention must be addressed to the durability of reinforced concrete (RC) structures. When RC structures are located in aggressive environments, its durability is strongly reduced by physical/chemical/mechanical processes that trigger the corrosion of reinforcements. Among these processes, the diffusion of chlorides is recognized as one of major responsible of corrosion phenomenon start. To accurate modelling the corrosion of reinforcements and to assess the durability of RC structures, a mechanical model that accounts realistically for both concrete and steel mechanical behaviour must be considered. In this context, this study presents a numerical nonlinear formulation based on the finite element method applied to structural analysis of RC structures subjected to chloride penetration and reinforcements corrosion. The physical nonlinearity of concrete is described by Mazars damage model whereas for reinforcements elastoplastic criteria are adopted. The steel loss along time due to corrosion is modelled using an empirical approach presented in literature and the chloride concentration growth along structural cover is represented by Fick's law. The proposed model is applied to analysis of bended structures. The results obtained by the proposed numerical approach are compared to responses available in literature in order to illustrate the evolution of structural resistant load after corrosion start. (C) 2014 Elsevier Ltd. All rights reserved.

Processing and characterization of ablative composites used in rocket motors

The main objective of this research work was to obtain two formulations of ablative composites. These composites are also known as ablative structural composites, for applications in atmospherically severe conditions according to the high-temperature, hot gaseous products flow generated from the burning of solid propellants. The formulations were manufactured with phenolic resin reinforced with chopped carbon fiber. The composites were obtained by the hot compression molding technique. Another purpose of this work was to conduct the physical and chemical characterization of the matrix, the reinforcements and the composites. After the characterization, a nozzle divergent of each formulation was manufactured and its performance was evaluated through the rocket motor static firing test. According to the results found in this work, it was possible to observe through the characterization of the raw materials that phenolic resins showed peculiarities in their properties that differentiate one from the other, but did not exhibit significant differences in performance as a composite material for use in ablation conditions. Both composites showed good performance for use in thermal protection, confirmed by firing static tests (rocket motor). Composites made with phenolic resin and chopped carbon fiber showed that it is a material with excellent resistance to ablation process. This composite can be used to produce nozzle parts with complex geometry or shapes and low manufacturing cost.

Modeling of multiple cracks in reinforced concrete members using solid finite elements with high aspect ratio

This paper presents a new technique to model interfaces by means of degenerated solid finite elements, i.e., elements with a very high aspect ratio, with the smallest dimension corresponding to the thickness of the interfaces. It is shown that, as the aspect ratio increases, the element strains also increase, approaching the kinematics of the strong discontinuity. A tensile damage constitutive relation between strains and stresses is proposed to describe the nonlinear behavior of the interfaces associated with crack opening. To represent crack propagation, couples of triangular interface elements are introduced in between all regular (bulk) elements of the original mesh. With this technique the analyses can be performed integrally in the context of the continuum mechanics and complex crack patterns involving multiple cracks can be simulated without the need of tracking algorithms. Numerical tests are performed to show the applicability of the proposed technique, studding also aspects related to mesh objectivity.

Heat Treatment and Yb-Fiber Laser Welding of a Maraging Steel

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES)