A Speculation on Dynamic Recrystallization l. Introduction Moderate to low stacking fault metals ... more A Speculation on Dynamic Recrystallization l. Introduction Moderate to low stacking fault metals deformed at high ternperatures may work-harden sufficiently for recrystallization to occur simultaneously with straining in thc so called " dynamic recrystallization " ; this process is considered as consisting of a series of work hardening and recrystallization cycles,1) involving a stable grain size (d,) corresponding to an " equilibrium nucleus density "I); d, seems to depend only on Zener-Hollomon's parameter2) and to decrease as
Materials Science Engineering a Structural Materials Properties Microstructure and Processing, Aug 1, 2009
The evolution of damage was investigated for an aluminum alloy processed by equal-channel angular... more The evolution of damage was investigated for an aluminum alloy processed by equal-channel angular pressing. The investigation was performed for two different structural states: an annealed condition where there is strain hardening and a processed condition where the strain hardening capability is essentially exhausted and there is a near perfect-plastic behavior. Finite element modeling (FEM) was used with experimental data obtained from tension and compression testing at room temperature. The results show that high levels of damage may be accumulated in the material exhibiting strain hardening behavior and this may lead to billet segmentation whereas in the near perfect-plastic condition cracking occurs only on the upper surfaces of the billets and these cracks are reasonably stable.
The occurrence of strain softening in drawn low carbon steel bars, as a consequence of cyclic tor... more The occurrence of strain softening in drawn low carbon steel bars, as a consequence of cyclic torsion, was previously observed in terms of changes in the mechanical properties of the bars and in the drawing stress, bringing out the possibility of employing cyclic straining ...
Materials Science Engineering a Structural Materials Properties Microstructure and Processing, Jun 1, 2007
... 1633–1648. [14] AI Fernández, B. López and JM Rodríguez-Ibabe. Scripta Mater., 40 5 (1999), p... more ... 1633–1648. [14] AI Fernández, B. López and JM Rodríguez-Ibabe. Scripta Mater., 40 5 (1999), pp. 543–549. [15] EI Poliak and JJ Jonas. ISIJ Int., 43-5 (2003), pp. 684–691. [16] IP Pinheiro, WA Monteiro, R. Barbosa and PR Cetlin. Mater. Sci. Eng. A, 368 (2004), pp. 280–285. ...
Abstract Sheet metal forming commonly involves vari-ous processing steps leading to complex strai... more Abstract Sheet metal forming commonly involves vari-ous processing steps leading to complex strain paths. The work hardening of the metal under these circumstances is different from that observed for monotonic straining. The effect of the strain path on the hardening of ...
In the present work, experimental techniques for evaluating the deformation and the redundant wor... more In the present work, experimental techniques for evaluating the deformation and the redundant work factor in the axisymmetric drawing of ferritic AISI 420 stainless steel bars were investigated. Six operation conditions, involving two reductions of area and three die ...
Page 1. ULTRAFINE GRAINED MATERIALS Avoiding cracks and inhomogeneities in billets processed by E... more Page 1. ULTRAFINE GRAINED MATERIALS Avoiding cracks and inhomogeneities in billets processed by ECAP Paulo R. Cetlin Maria Teresa P. Aguilar Roberto B. Figueiredo Terence G. Langdon Received: 23 January ...
Metal working of metallic polycrystals is industrially used under cold or hot conditions (1). Mon... more Metal working of metallic polycrystals is industrially used under cold or hot conditions (1). Monotonic cold working leads to parabolic work hardening, the rate of which decreases as the temperature is raised or the strain rate lowered. Tension-compression cyclic cold straining involves less hardening than monotonic deformation, for the same total strain (2,3). This effect is enhanced by the use of lower strain amplitudes per cycle. The sequential multiaxial deformation of metals comprises successive straining along different axes. It results in a situation similar to cyclic straining, involving (a) decreased work hardening, as compared to monotonic straining, and (b) the same effect of strain amplitude (4).
ABSTRACT The performance of materials made from Portland cement is usually evaluated by tensile s... more ABSTRACT The performance of materials made from Portland cement is usually evaluated by tensile strength under compression loads, elastic modulus and porosity. Modulus of elasticity is usually determined from compression tests, and the results show large dispersions. With the advances in data acquisition and signal processing, the infrared thermography and forced resonant frequency have been increasingly used in the study of materials. However, these studies are devoted almost entirely to metals. In this paper it is evaluates the use of the method of forced longitudinal resonance frequency and infrared thermography as a tool for characterization of the buildings cementitious materials. The results show that thermography and forced resonant frequency are Able to detect changes in concrete macrostructure as well as the nature of its constituents.
ABSTRACT An investigation was conducted to evaluate the feasibility of using commercial purity (C... more ABSTRACT An investigation was conducted to evaluate the feasibility of using commercial purity (CP) titanium of grade 1 for dental implants after processing by equal-channel angular pressing (ECAP). The material was processed by ECAP for 4 passes at room temperature. Dental implants were machined from the unprocessed material and the material processed by ECAP and their mechanical properties were evaluated in tensile and compression testing and in fatigue using the conditions specified in the ISO 14801 standard for dental implants. The results show processing by ECAP increases the yield stress and the ultimate tensile stress but reduces the strain hardening rate and hence the overall elongation to failure. Although processing by ECAP increases the fatigue life using cyclic bending loads, a comparison with published data suggests the fatigue behavior CP Ti of grade 1 is slightly less satisfactory than for commercial implants fabricated from higher grade titanium alloys.
A Speculation on Dynamic Recrystallization l. Introduction Moderate to low stacking fault metals ... more A Speculation on Dynamic Recrystallization l. Introduction Moderate to low stacking fault metals deformed at high ternperatures may work-harden sufficiently for recrystallization to occur simultaneously with straining in thc so called " dynamic recrystallization " ; this process is considered as consisting of a series of work hardening and recrystallization cycles,1) involving a stable grain size (d,) corresponding to an " equilibrium nucleus density "I); d, seems to depend only on Zener-Hollomon's parameter2) and to decrease as
Materials Science Engineering a Structural Materials Properties Microstructure and Processing, Aug 1, 2009
The evolution of damage was investigated for an aluminum alloy processed by equal-channel angular... more The evolution of damage was investigated for an aluminum alloy processed by equal-channel angular pressing. The investigation was performed for two different structural states: an annealed condition where there is strain hardening and a processed condition where the strain hardening capability is essentially exhausted and there is a near perfect-plastic behavior. Finite element modeling (FEM) was used with experimental data obtained from tension and compression testing at room temperature. The results show that high levels of damage may be accumulated in the material exhibiting strain hardening behavior and this may lead to billet segmentation whereas in the near perfect-plastic condition cracking occurs only on the upper surfaces of the billets and these cracks are reasonably stable.
The occurrence of strain softening in drawn low carbon steel bars, as a consequence of cyclic tor... more The occurrence of strain softening in drawn low carbon steel bars, as a consequence of cyclic torsion, was previously observed in terms of changes in the mechanical properties of the bars and in the drawing stress, bringing out the possibility of employing cyclic straining ...
Materials Science Engineering a Structural Materials Properties Microstructure and Processing, Jun 1, 2007
... 1633–1648. [14] AI Fernández, B. López and JM Rodríguez-Ibabe. Scripta Mater., 40 5 (1999), p... more ... 1633–1648. [14] AI Fernández, B. López and JM Rodríguez-Ibabe. Scripta Mater., 40 5 (1999), pp. 543–549. [15] EI Poliak and JJ Jonas. ISIJ Int., 43-5 (2003), pp. 684–691. [16] IP Pinheiro, WA Monteiro, R. Barbosa and PR Cetlin. Mater. Sci. Eng. A, 368 (2004), pp. 280–285. ...
Abstract Sheet metal forming commonly involves vari-ous processing steps leading to complex strai... more Abstract Sheet metal forming commonly involves vari-ous processing steps leading to complex strain paths. The work hardening of the metal under these circumstances is different from that observed for monotonic straining. The effect of the strain path on the hardening of ...
In the present work, experimental techniques for evaluating the deformation and the redundant wor... more In the present work, experimental techniques for evaluating the deformation and the redundant work factor in the axisymmetric drawing of ferritic AISI 420 stainless steel bars were investigated. Six operation conditions, involving two reductions of area and three die ...
Page 1. ULTRAFINE GRAINED MATERIALS Avoiding cracks and inhomogeneities in billets processed by E... more Page 1. ULTRAFINE GRAINED MATERIALS Avoiding cracks and inhomogeneities in billets processed by ECAP Paulo R. Cetlin Maria Teresa P. Aguilar Roberto B. Figueiredo Terence G. Langdon Received: 23 January ...
Metal working of metallic polycrystals is industrially used under cold or hot conditions (1). Mon... more Metal working of metallic polycrystals is industrially used under cold or hot conditions (1). Monotonic cold working leads to parabolic work hardening, the rate of which decreases as the temperature is raised or the strain rate lowered. Tension-compression cyclic cold straining involves less hardening than monotonic deformation, for the same total strain (2,3). This effect is enhanced by the use of lower strain amplitudes per cycle. The sequential multiaxial deformation of metals comprises successive straining along different axes. It results in a situation similar to cyclic straining, involving (a) decreased work hardening, as compared to monotonic straining, and (b) the same effect of strain amplitude (4).
ABSTRACT The performance of materials made from Portland cement is usually evaluated by tensile s... more ABSTRACT The performance of materials made from Portland cement is usually evaluated by tensile strength under compression loads, elastic modulus and porosity. Modulus of elasticity is usually determined from compression tests, and the results show large dispersions. With the advances in data acquisition and signal processing, the infrared thermography and forced resonant frequency have been increasingly used in the study of materials. However, these studies are devoted almost entirely to metals. In this paper it is evaluates the use of the method of forced longitudinal resonance frequency and infrared thermography as a tool for characterization of the buildings cementitious materials. The results show that thermography and forced resonant frequency are Able to detect changes in concrete macrostructure as well as the nature of its constituents.
ABSTRACT An investigation was conducted to evaluate the feasibility of using commercial purity (C... more ABSTRACT An investigation was conducted to evaluate the feasibility of using commercial purity (CP) titanium of grade 1 for dental implants after processing by equal-channel angular pressing (ECAP). The material was processed by ECAP for 4 passes at room temperature. Dental implants were machined from the unprocessed material and the material processed by ECAP and their mechanical properties were evaluated in tensile and compression testing and in fatigue using the conditions specified in the ISO 14801 standard for dental implants. The results show processing by ECAP increases the yield stress and the ultimate tensile stress but reduces the strain hardening rate and hence the overall elongation to failure. Although processing by ECAP increases the fatigue life using cyclic bending loads, a comparison with published data suggests the fatigue behavior CP Ti of grade 1 is slightly less satisfactory than for commercial implants fabricated from higher grade titanium alloys.
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