Cláudio G Schön | Universidade de Sao Paulo (original) (raw)
Uploads
Papers by Cláudio G Schön
Duplex stainless steels are Fe-Cr-Ni-Mo-N alloys with nitrogen replacing some nickel to improve i... more Duplex stainless steels are Fe-Cr-Ni-Mo-N alloys with nitrogen replacing some nickel to improve its properties. These steels have a balanced microstructure, which means that ferrite (a) and austenite (c) are in equal proportions of approximately 50% by volume. These alloys have a tendency to form intermetallic precipitates such as chromium nitrides and sigma phase (r), depending on their chemical composition and welding thermal history. Precipitation of these intermetallic phases can impair mechanical and corrosion properties. In addition, material processes such as welding and heat treatment can change the balanced microstructure. The objective of this work was to compare phases formed during heat treatment and welding of duplex stainless steel UNS S82441 with the equilibrium phases predicted by Thermo-calc Ò software. In general, the results showed good agreement between predicted and measured phases, as well as, agreement between the measured volume fraction of austenite in the heat-affected zone and austenite predicted by Thermo-calc Ò software.
The International Journal of Advanced Manufacturing Technology, 2015
ABSTRACT This work aims at studying the influence of the strain path upon the FLC 0 formability p... more ABSTRACT This work aims at studying the influence of the strain path upon the FLC 0 formability parameter, the root of the forming limit curves (FLC). The investigation was conducted in an Interstitial Free (IF) quality steel. The FLC 0 parameter was evaluated in an intrinsic tensile test in near plane strain (NPS) condition, but following two strain paths. The first one being a uniaxial (proportional) path up to initial necking. The second (non-proportional) path corresponded to applying 15% nominal plastic strain in one direction (near plane strain) followed by a second deformation applied in the orthogonal direction up to the rupture of the samples. A reduction in the limit strains corresponding to FLC 0 in the non-proportional test, has been observed. The forming limit stress curves (FLSC), and the critical values FLSD 0 are also related with these trajectories. A simulation using finite element method (FEM) has been applied to analyze the evolution of stress and strain during the two paths and the results have been found consistent for both proportional and non-proportional paths. Texture and surface roughness evolution of the sheet were also measured and related to the applied strain paths.
The aim of the present work is to develop a computational model of a compact pressurized water nu... more The aim of the present work is to develop a computational model of a compact pressurized water nuclear reactor (PWR) to investigate the use of innovative materials to enhance the biological shielding effectiveness. Two radiation transport codes were used: the first one – MCNP – for the PWR design and the GEM/EVENT to simulate (in a 1D slab) the behavior of several materials and shielding thickness on gamma and neutron radiation. Additionally MATLAB Optimization Toolbox was used to provide new geometric configurations of the slab aiming at reducing the volume and weight of the walls by means of a cost/objective function. It is demonstrated in the reactor model that the dose rate outside biological shielding has been reduced by one order of magnitude for the optimized model compared with the initial configuration. Volume and weight of the shielding walls were also reduced. The results indicated that one-dimensional deterministic code to reach an optimized geometry and test materials, combined with a three-dimensional model of a compact nuclear reactor in a stochastic code, is a fast and efficient procedure to test shielding performance and optimization before the experimental assessment. A major outcome of this research is that composite materials (ECOMASS 2150TU96) may replace (with advantages) traditional shielding materials without jeopardizing the nuclear power plant safety assurance.
Prototype calculations in ternary ordering systems based on the b.c.c. lattice have been carried ... more Prototype calculations in ternary ordering systems based on the b.c.c. lattice have been carried out with the Cluster Variation Method (CVM) in the irregular tetrahedron approximation including tetrahedron interactions. The systems under investigations were characterized by strong ordering tendencies (i.e. with large, negative first neighbour interactions in all binary subsystems) which resulted in the opening of a miscibility gap inside the B2 single-phase field. This miscibility gap is shown to be produced by frustration of the B2 cluster by a calculation using a hypothetical system with identical first neighbour interactions in the three binary subsystems. This phase diagram presents as a key feature a central three-phase miscibility gap, which transforms into an ordinary two-phase miscibility gap involving two B2 phases after the symmetry of the interactions is broken. The results are discussed in connection with the experimental Fe–Ti–Rh phase diagram.
The cluster variation method (CVM) has been used as a tool for modelling the thermodynamics of th... more The cluster variation method (CVM) has been used as a tool for modelling the thermodynamics of the b.c.c. Co–Cr–Al system within the irregular tetrahedron approximation. The interaction parameters (nearest and next-nearest neighbour pairs, as well as tetrahedron interactions) for the three binary subsystems have been derived following the so-called phenomenological approach, i.e. the interaction parameters have been fitted to experimental phase diagram and/or thermochemical data. As a result, the three binary phase diagrams of the system and four isothermal sections of the ternary phase diagram have been obtained. The results show that the CVM is thermodynamically self-consistent.
Recent binary thermodynamic descriptions are used as a starting point for the modelling of the te... more Recent binary thermodynamic descriptions are used as a starting point for the modelling of the ternary Nb–Ni–Si phase diagram. First-principles electronic structure calculations, within the framework of the Density Functional Theory (DFT), are performed for the determination of formation energies of known ternary compounds. The results are introduced into a CALPHAD-type thermodynamic model using the Compound Energy Formalism (CEF). The model parameters are then optimised in order to match the experimental 1073 K isothermal section of the ternary phase diagram.
Materials Research-Ibero-American Journal of Materials, 2014
An alternative procedure for the determination of the FLC 0 value, the limit strain value corresp... more An alternative procedure for the determination of the FLC 0 value, the limit strain value corresponding to the plane strain mode of the Forming Limit Curves (FLC), a critical parameter in the sheet formability analysis, is suggested and compared with conventional Nakazima simulation tests. The procedure was tested using two different materials:
Design specifications in automobile project and construction lead, in recent models, to the prefe... more Design specifications in automobile project and construction lead, in recent models, to the preference of
using increasingly larger and slender tires. The tire and wheel set, however, is instrumental in determin-
ing the loads which act in the entire structure, in particular, in the vehicle body. The influence of different
tire sizes and profiles over the load spectra obtained in a rough road test track was investigated by instru-
menting fourteen points in the body of a typical passenger’s car. It is shown that increased tire sizes lead
to more severe loads, which are reflected in higher damage, as estimated by the use of the linear rule.
This work aims at studying the influence of the strain path upon the FLC 0 formability parameter,... more This work aims at studying the influence of the
strain path upon the FLC 0 formability parameter, the root
of the forming limit curves (FLC). The investigation was
conducted in an interstitial free (IF) quality steel. The FLC 0
parameter was evaluated in an intrinsic tensile test in near
plane strain (NPS) condition, but following two strain paths.
The first one being a uniaxial (proportional) path up to
initial necking. The second (non-proportional) path corre-
sponded to applying 15 % nominal plastic strain in one
direction (near plane strain) followed by a second deforma-
tion applied in the orthogonal direction up to the rupture of
the samples. A reduction in the limit strains corresponding
to FLC 0 in the non-proportional test has been observed. The
forming limit stress curves (FLSC) and the critical values
FLSD 0 are also related to these trajectories. A simulation
using finite element method (FEM) has been applied to ana-
lyze the evolution of stress and strain during the two paths,
and the results have been found consistent for both pro-
portional and non-proportional paths. Texture and surface
roughness evolution of the sheet were also measured and
related to the applied strain paths.
An alternative procedure for the determination of the FLC 0 value, the limit strain value corresp... more An alternative procedure for the determination of the FLC 0 value, the limit strain value
corresponding to the plane strain mode of the Forming Limit Curves (FLC), a critical parameter in
the sheet formability analysis, is suggested and compared with conventional Nakazima simulation
tests. The procedure was tested using two different materials: interstitial-free quality steel (IF) and
a spheroidized SAE 1050 steel. The intrinsic tensile test, in a near plane strain state, was performed
using a small number of samples, with dimensions suggested by the literature. The results were
checked against Nakazima test results using the same materials. The plane strain test was reliable in
determining consistent FLC 0 values and should be preferred since it is not affected by the geometric
aspects and by friction, which do affect the Nakazima test. The reliability of the FLC 0 values obtained
by near plane strain was also corroborated through comparison with literature data.
Acta Materialia, 1998
AbstractÐThe concentration dependence of the con®gurational speci®c heat capacity and of the ther... more AbstractÐThe concentration dependence of the con®gurational speci®c heat capacity and of the thermodynamic factor for diusion have been calculated for f.c.c. Ni±Al and b.c.c. Fe±Al alloys using the Cluster Variation Method in the tetrahedron approximation. Unexpected variations have been obtained, particularly close to stoichiometric compositions. # 1998 Acta Metallurgica Inc. Published by Elsevier Science Ltd. All rights reserved.
Duplex stainless steels are Fe-Cr-Ni-Mo-N alloys with nitrogen replacing some nickel to improve i... more Duplex stainless steels are Fe-Cr-Ni-Mo-N alloys with nitrogen replacing some nickel to improve its properties. These steels have a balanced microstructure, which means that ferrite (a) and austenite (c) are in equal proportions of approximately 50% by volume. These alloys have a tendency to form intermetallic precipitates such as chromium nitrides and sigma phase (r), depending on their chemical composition and welding thermal history. Precipitation of these intermetallic phases can impair mechanical and corrosion properties. In addition, material processes such as welding and heat treatment can change the balanced microstructure. The objective of this work was to compare phases formed during heat treatment and welding of duplex stainless steel UNS S82441 with the equilibrium phases predicted by Thermo-calc Ò software. In general, the results showed good agreement between predicted and measured phases, as well as, agreement between the measured volume fraction of austenite in the heat-affected zone and austenite predicted by Thermo-calc Ò software.
The International Journal of Advanced Manufacturing Technology, 2015
ABSTRACT This work aims at studying the influence of the strain path upon the FLC 0 formability p... more ABSTRACT This work aims at studying the influence of the strain path upon the FLC 0 formability parameter, the root of the forming limit curves (FLC). The investigation was conducted in an Interstitial Free (IF) quality steel. The FLC 0 parameter was evaluated in an intrinsic tensile test in near plane strain (NPS) condition, but following two strain paths. The first one being a uniaxial (proportional) path up to initial necking. The second (non-proportional) path corresponded to applying 15% nominal plastic strain in one direction (near plane strain) followed by a second deformation applied in the orthogonal direction up to the rupture of the samples. A reduction in the limit strains corresponding to FLC 0 in the non-proportional test, has been observed. The forming limit stress curves (FLSC), and the critical values FLSD 0 are also related with these trajectories. A simulation using finite element method (FEM) has been applied to analyze the evolution of stress and strain during the two paths and the results have been found consistent for both proportional and non-proportional paths. Texture and surface roughness evolution of the sheet were also measured and related to the applied strain paths.
The aim of the present work is to develop a computational model of a compact pressurized water nu... more The aim of the present work is to develop a computational model of a compact pressurized water nuclear reactor (PWR) to investigate the use of innovative materials to enhance the biological shielding effectiveness. Two radiation transport codes were used: the first one – MCNP – for the PWR design and the GEM/EVENT to simulate (in a 1D slab) the behavior of several materials and shielding thickness on gamma and neutron radiation. Additionally MATLAB Optimization Toolbox was used to provide new geometric configurations of the slab aiming at reducing the volume and weight of the walls by means of a cost/objective function. It is demonstrated in the reactor model that the dose rate outside biological shielding has been reduced by one order of magnitude for the optimized model compared with the initial configuration. Volume and weight of the shielding walls were also reduced. The results indicated that one-dimensional deterministic code to reach an optimized geometry and test materials, combined with a three-dimensional model of a compact nuclear reactor in a stochastic code, is a fast and efficient procedure to test shielding performance and optimization before the experimental assessment. A major outcome of this research is that composite materials (ECOMASS 2150TU96) may replace (with advantages) traditional shielding materials without jeopardizing the nuclear power plant safety assurance.
Prototype calculations in ternary ordering systems based on the b.c.c. lattice have been carried ... more Prototype calculations in ternary ordering systems based on the b.c.c. lattice have been carried out with the Cluster Variation Method (CVM) in the irregular tetrahedron approximation including tetrahedron interactions. The systems under investigations were characterized by strong ordering tendencies (i.e. with large, negative first neighbour interactions in all binary subsystems) which resulted in the opening of a miscibility gap inside the B2 single-phase field. This miscibility gap is shown to be produced by frustration of the B2 cluster by a calculation using a hypothetical system with identical first neighbour interactions in the three binary subsystems. This phase diagram presents as a key feature a central three-phase miscibility gap, which transforms into an ordinary two-phase miscibility gap involving two B2 phases after the symmetry of the interactions is broken. The results are discussed in connection with the experimental Fe–Ti–Rh phase diagram.
The cluster variation method (CVM) has been used as a tool for modelling the thermodynamics of th... more The cluster variation method (CVM) has been used as a tool for modelling the thermodynamics of the b.c.c. Co–Cr–Al system within the irregular tetrahedron approximation. The interaction parameters (nearest and next-nearest neighbour pairs, as well as tetrahedron interactions) for the three binary subsystems have been derived following the so-called phenomenological approach, i.e. the interaction parameters have been fitted to experimental phase diagram and/or thermochemical data. As a result, the three binary phase diagrams of the system and four isothermal sections of the ternary phase diagram have been obtained. The results show that the CVM is thermodynamically self-consistent.
Recent binary thermodynamic descriptions are used as a starting point for the modelling of the te... more Recent binary thermodynamic descriptions are used as a starting point for the modelling of the ternary Nb–Ni–Si phase diagram. First-principles electronic structure calculations, within the framework of the Density Functional Theory (DFT), are performed for the determination of formation energies of known ternary compounds. The results are introduced into a CALPHAD-type thermodynamic model using the Compound Energy Formalism (CEF). The model parameters are then optimised in order to match the experimental 1073 K isothermal section of the ternary phase diagram.
Materials Research-Ibero-American Journal of Materials, 2014
An alternative procedure for the determination of the FLC 0 value, the limit strain value corresp... more An alternative procedure for the determination of the FLC 0 value, the limit strain value corresponding to the plane strain mode of the Forming Limit Curves (FLC), a critical parameter in the sheet formability analysis, is suggested and compared with conventional Nakazima simulation tests. The procedure was tested using two different materials:
Design specifications in automobile project and construction lead, in recent models, to the prefe... more Design specifications in automobile project and construction lead, in recent models, to the preference of
using increasingly larger and slender tires. The tire and wheel set, however, is instrumental in determin-
ing the loads which act in the entire structure, in particular, in the vehicle body. The influence of different
tire sizes and profiles over the load spectra obtained in a rough road test track was investigated by instru-
menting fourteen points in the body of a typical passenger’s car. It is shown that increased tire sizes lead
to more severe loads, which are reflected in higher damage, as estimated by the use of the linear rule.
This work aims at studying the influence of the strain path upon the FLC 0 formability parameter,... more This work aims at studying the influence of the
strain path upon the FLC 0 formability parameter, the root
of the forming limit curves (FLC). The investigation was
conducted in an interstitial free (IF) quality steel. The FLC 0
parameter was evaluated in an intrinsic tensile test in near
plane strain (NPS) condition, but following two strain paths.
The first one being a uniaxial (proportional) path up to
initial necking. The second (non-proportional) path corre-
sponded to applying 15 % nominal plastic strain in one
direction (near plane strain) followed by a second deforma-
tion applied in the orthogonal direction up to the rupture of
the samples. A reduction in the limit strains corresponding
to FLC 0 in the non-proportional test has been observed. The
forming limit stress curves (FLSC) and the critical values
FLSD 0 are also related to these trajectories. A simulation
using finite element method (FEM) has been applied to ana-
lyze the evolution of stress and strain during the two paths,
and the results have been found consistent for both pro-
portional and non-proportional paths. Texture and surface
roughness evolution of the sheet were also measured and
related to the applied strain paths.
An alternative procedure for the determination of the FLC 0 value, the limit strain value corresp... more An alternative procedure for the determination of the FLC 0 value, the limit strain value
corresponding to the plane strain mode of the Forming Limit Curves (FLC), a critical parameter in
the sheet formability analysis, is suggested and compared with conventional Nakazima simulation
tests. The procedure was tested using two different materials: interstitial-free quality steel (IF) and
a spheroidized SAE 1050 steel. The intrinsic tensile test, in a near plane strain state, was performed
using a small number of samples, with dimensions suggested by the literature. The results were
checked against Nakazima test results using the same materials. The plane strain test was reliable in
determining consistent FLC 0 values and should be preferred since it is not affected by the geometric
aspects and by friction, which do affect the Nakazima test. The reliability of the FLC 0 values obtained
by near plane strain was also corroborated through comparison with literature data.
Acta Materialia, 1998
AbstractÐThe concentration dependence of the con®gurational speci®c heat capacity and of the ther... more AbstractÐThe concentration dependence of the con®gurational speci®c heat capacity and of the thermodynamic factor for diusion have been calculated for f.c.c. Ni±Al and b.c.c. Fe±Al alloys using the Cluster Variation Method in the tetrahedron approximation. Unexpected variations have been obtained, particularly close to stoichiometric compositions. # 1998 Acta Metallurgica Inc. Published by Elsevier Science Ltd. All rights reserved.