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Search Results: 1 - 10 of 6431 matches for " Waldemar Alfredo;Cetlin "
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The effect of cyclic torsion on the dislocation structure of drawn mild steel
Aguilar, Maria Teresa Paulino;Corrêa, Elaine Carballo Siqueira;Monteiro, Waldemar Alfredo;Cetlin, Paulo Roberto;
Materials Research , 2006, DOI: 10.1590/S1516-14392006000300016
Abstract: cold forming is usually associated with the "work hardening" of the material being formed. the work hardening behavior of metals subject to complex processing paths is different from that in monotonic deformation. the results show that, after some initial hardening, there is a possibility that further deformation will cause softening in the material ("work softening"). recent work showed that cyclic torsion applied to drawn products causes changes in the subsequent tensile behavior of low carbon steel, and that the effect will depend on the previous "history" of the material. for annealed samples, the cyclic torsion leads to an increase in the yield strength, but does not affect the tensile strength and elongation. for the case of previously drawn bars, the cyclic deformation caused a decrease in the yield and tensile strength and an increase in the total elongation. the present paper discusses the dislocation structure changes associated with different strain paths in mild steel.
Work softening of drawn low carbon steel bars
Aguilar, Maria Teresa Paulino;Corrêa, Elaine Carballo Siqueira;Monteiro, Waldemar Alfredo;Ferreira, Nildemar Aparecido Messias;Cetlin, Paulo Roberto;
Materials Research , 2001, DOI: 10.1590/S1516-14392001000200008
Abstract: the work hardening of metals subjected to complex processing paths is different from that in monotonic deformation. changes in the deformation mode can promote transients in the strain-hardening rate, leading to anomalous softening or hardening of the material. this paper investigates the influence of strain path changes on the tensile behavior of drawn 0.12% steel rods. annealed or predrawn specimens were submitted to cyclic twisting and then tested in tension. the results show that the cyclic deformation causes changes in the mechanical behavior of the metal, and the effect will depend on the previous "history" of the material. cyclic twisting causes hardening in annealed samples, but leads to softening of the drawn bars. these phenomena are in line with the corresponding substructural aspects.
Characterization of Nickel Alloy 600 with Ultra-Fine Structure Processed by Severe Plastic Deformation Technique (SPD)  [PDF]
Waldemar Alfredo Monteiro, Silvio Luis Ventavele da Silva, Luciana Ventavele da Silva, Arnaldo Homobono Paes de Andrade, Luis Carlos Elias da Silva
Journal of Materials Science and Chemical Engineering (MSCE) , 2017, DOI: 10.4236/msce.2017.54004
Abstract: High strength nickel based alloys are used in a multitude of advanced systems where lightweight, high power density mechanical power transmission systems are required. Components such as gears, bearings and shafts could be made significantly smaller and more durable if a major improvement in nickel based alloy mechanical properties could be achieved. An important refinement in grain size (includes nanometric level) is thought to be a promising method for achieving fundamental improvements in mechanical properties. Grain size is known to have a significant effect on the mechanical behavior of materials. One of the most favorable methods of achieving extreme grain refinement is by subjecting the materials to severe plastic deformation (SPD). The principal micro-structural variations in superalloys are the precipitation amount and morphology, grain size and the distribution of carbide precipitation that could reduce the mechanical properties of the alloys. This work shows optical and transmission electron microscopy analysis and also hardness data after severe plastic deformation (pure shear stress).
Mathematical model predicts the elastic behavior of composite materials
Boari, Zoroastro de Miranda;Monteiro, Waldemar Alfredo;Miranda, Carlos Alexandre de Jesus;
Materials Research , 2005, DOI: 10.1590/S1516-14392005000100017
Abstract: several studies have found that the non-uniform distribution of reinforcing elements in a composite material can markedly influence its characteristics of elastic and plastic deformation and that a composite's overall response is influenced by the physical and geometrical properties of its reinforcing phases. the finite element method, eshelby's method and dislocation mechanisms are usually employed in formulating a composite's constitutive response. this paper discusses a composite material containing sic particles in an aluminum matrix. the purpose of this study was to find the correlation between a composite material's particle distribution and its resistance, and to come up with a mathematical model to predict the material's elastic behavior. the proposed formulation was applied to establish the thermal stress field in the aluminum-sic composite resulting from its fabrication process, whereby the mixture is prepared at 600 °c and the composite material is used at room temperature. the analytical results, which are presented as stress probabilities, were obtained from the mathematical model proposed herein. these results were compared with the numerical ones obtained by the fem method. a comparison of the results of the two methods, analytical and numerical, reveals very similar average thermal stress values. it is also shown that maxwell-boltzmann's distribution law can be applied to identify the correlation between the material's particle distribution and its resistance, using eshelby's thermal stresses.
Work softening of drawn low carbon steel bars
Aguilar Maria Teresa Paulino,Corrêa Elaine Carballo Siqueira,Monteiro Waldemar Alfredo,Ferreira Nildemar Aparecido Messias
Materials Research , 2001,
Abstract: The work hardening of metals subjected to complex processing paths is different from that in monotonic deformation. Changes in the deformation mode can promote transients in the strain-hardening rate, leading to anomalous softening or hardening of the material. This paper investigates the influence of strain path changes on the tensile behavior of drawn 0.12% steel rods. Annealed or predrawn specimens were submitted to cyclic twisting and then tested in tension. The results show that the cyclic deformation causes changes in the mechanical behavior of the metal, and the effect will depend on the previous "history" of the material. Cyclic twisting causes hardening in annealed samples, but leads to softening of the drawn bars. These phenomena are in line with the corresponding substructural aspects.
The Quantum Oscillatory Modulated Potential - Part II - The Stability of the Hydrogen Atom  [PDF]
Waldemar Wolney Filho
Journal of Modern Physics (JMP) , 2012, DOI: 10.4236/jmp.2012.38090
Abstract: The purpose of this work is to show the stability of the hydrogen atom with the use the Quantum Oscillatory Modulated Potential and the Heisenberg equations of motion, postulating that the electron in the hydrogen atom is behaving as a quantum harmonic oscillator. With the electron confined between two potential barriers, created by the new potential function, we are considering that at absolute temperature the power absorbed or emitted by the electron per unit of time can be used to determine the zero point energy of the oscillator. Assuming that electron is only exchanging energy with the nucleus of the atom we are making use of the operators of creation and annihilation of a photon to explain how the energy between the proton and the electron can be exchanged to keep the atom a stable system.
The Quantum Oscillatory Modulated Potential Ⅰ- The Hydrogen Atom  [PDF]
Waldemar Wolney Filho
Journal of Modern Physics (JMP) , 2012, DOI: 10.4236/jmp.2012.37081
Abstract: In this work we are presenting a modified Coulomb potential function to describe the interaction between two micro-scopic electric charges. In particular, concerning the interaction between the proton and the electron in the hydrogen atom. The modified potential function is the product of the classical Coulomb potential and an oscillatory function dependent on a quantized phase factor. The oscillatory function picks up only selected points along the Coulomb potential, creating potential wells and barriers around the nucleus of the atom. The new potential reveals us new features of the hydrogen atom. Searching for a manner to determine the phase factor, we are using the concept of the de Broglie particle wavelike behavior and the quantum analogue of the virial theorem for describing the bound motion of a particle in a central force field. This procedure is a kind of feedback action, where we are making use of well established concepts of the quantum mechanics aiming to determine the phase factor of the new interaction potential.
The Quantum Oscillatory Modulated Potential—Electric Field Wave Packets Produced by Electrons  [PDF]
Waldemar Wolney Filho
Journal of Modern Physics (JMP) , 2015, DOI: 10.4236/jmp.2015.614216
Abstract: In this work we are formulating a new theory for describing the waving nature of a microscopic electric particle. Based on the predictions of the Quantum Oscillatory Modulated Potential—QOMP, for describing the interaction between two microscopic electric particles, electron-electron, for instance, we are postulating that the waving behavior of these particles may be an attribute of the charges of the particles and not their masses as currently accepted. For a microscopic electric charge, we are presenting new arguments showing that the electric field in the vicinity of a microscopic charge is spatially waving and can be determined as the gradient per unit of charge of this new quantum interaction potential, with use of an appropriated phase factor to account for the behavior of an unbound electron. Differently of what is predicted by the classical Coulomb electric field, when a charged particle is moving under the action of a potential of V volts, the new electric field existing around the charge has the form of a wave packet. For typical values of the potential V, the wavelength of the waving electric field is in very good agreement with those experimentally observed with diffraction of electrons in crystalline solids.
Targeting DNA with Anthracyclines: The Importance of the Sugar Moiety
Waldemar Priebe
Molecules , 2000, DOI: 10.3390/50300299
Abstract: No abstract available
Ensino, pesquisa e gest?o acadêmica na universidade: Teaching, research and higher education academic management
Marques, Waldemar;
Avalia??o: Revista da Avalia??o da Educa??o Superior (Campinas) , 2011, DOI: 10.1590/S1414-40772011000300011
Abstract: this article discusses the relations between the teacher's teaching activities and research work, trying to clarify in which aspects both are different and in which aspects they are closely inter-related. it emphasizes the processes which act as a strong incentive to research and to the publication of its results, whereas the same incentive is absent from the teaching activities and pedagogical innovation. it also discusses the problems of academic management, pointing to some aspects which indicate the fragility of the conditions under which management is taking place, conditions which do not lead to spaces of reflection on the processes of construction and dissemination of knowledge which point towards innovative pedagogical practices which might explicit or strengthen the necessary interaction of teaching and research.
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