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Rajarshi Banerjee - One of the best experts on this subject based on the ideXlab platform.
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effect of Specimen Thickness on the creep response of a ni based single crystal superalloy
Acta Materialia, 2012Co-Authors: Ankit Srivastava, S Gopagoni, A Needleman, V Seetharaman, Alexander Staroselsky, Rajarshi BanerjeeAbstract:Abstract Creep tests on Ni-based single-crystal superalloy sheet Specimens typically show greater creep strain rates and/or reduced strain or time to creep rupture for thinner Specimens than predicted by current theories, which predict a size-independent creep strain rate and creep rupture strain. This size-dependent creep response is termed the Thickness debit effect. To investigate the mechanism of the Thickness debit effect, isothermal, constant nominal stress creep tests were performed on uncoated PWA1484 Ni-based single-crystal superalloy sheet Specimens of Thicknesses 3.18 and 0.51 mm under two test conditions: 760 °C/758 MPa and 982 °C/248 MPa. The Specimens contained initial microvoids formed during the solidification and homogenization processes. The dependence of the creep response on Specimen Thickness differed under the two test conditions: at 760 °C/758 MPa there was a reduction in the creep strain and the time to rupture with decreasing section Thickness, whereas at 982 °C/248 MPa a decreased Thickness resulted in an increased creep rate even at low strain levels and a decreased time to rupture but with no systematic dependence of the creep strain to rupture on Specimen Thickness. For the Specimens tested at 760 °C/758 MPa microscopic analyses revealed that the thick Specimens exhibited a mixed failure mode of void growth and cleavage-like fracture while the predominant failure mode for the thin Specimens was cleavage-like fracture. The creep Specimens tested at 982 °C/248 MPa in air showed the development of surface oxides and a near-surface precipitate-free zone. Finite-element analysis revealed that the presence of the alumina layer at the free surface imposes a constraint that locally increases the stress triaxiality and changes the value of the Lode parameter (a measure of the third stress invariant). The surface cracks formed in the oxide scale were arrested by further oxidation; for a Thickness of 3.18 mm the failure mode was void nucleation, growth and coalescence, whereas for a Thickness of 0.51 mm there was a mixed mode of ductile and cleavage-like fracture.
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effect of Specimen Thickness on the creep response of a ni based single crystal superalloy preprint
2012Co-Authors: Ankit Srivastava, S Gopagoni, A Needleman, Rajarshi Banerjee, Alexander StaroselskyAbstract:Abstract : Creep tests on Ni-based single crystal superalloy sheet Specimens typically show greater creep strain rates and/or reduced strain or time to creep rupture for thinner Specimens than predicted by current theories which predict a size independent creep strain rate and creep rupture strain. This size dependent creep response is termed the Thickness debit effect. To investigate the mechanism of the Thickness debit effect, isothermal, constant nominal stress creep tests were performed on uncoated PWA1484 Ni-based single crystal superalloy sheet Specimens of Thicknesses 3.18mm and 0.51mm under two test conditions: 760◦C/758MPa and 982◦C/248MPa. The Specimens contained initial micro-voids formed during the solidification and homogenization processes. The dependence of the creep response on Specimen Thickness differed under the two test conditions: at 760◦C/758MPa there was a reduction in the creep strain and the time to rupture with decreasing section Thickness while at 982◦C/248MPa a decreased Thickness resulted in an increased creep rate even at low strain levels and a decreased time to rupture but with no systematic dependence of the creep.
R J Gaymans - One of the best experts on this subject based on the ideXlab platform.
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polycarbonate and co continuous polycarbonate abs blends influence of Specimen Thickness
Polymer, 2002Co-Authors: J P F Inberg, R J GaymansAbstract:The influence of Specimen Thickness on the fracture behaviour of polycarbonate (PC) and co-continuous PC/ABS (50/50) blends was studied in single edge notch tensile tests at 1 m/s and different temperatures (−80 to 130 °C). Specimen Thickness ranged from 0.1 to 8 mm. In the co-continuous PC/ABS blends the rubber concentration in the ABS was 0, 15 and 30 wt%. The change in fracture toughness was typified by the change in brittle-to-ductile transition temperature (Tbd). Tbd of pure PC depended strongly on Specimen Thickness, leading to very low transition temperatures for thin PC Specimens. PC/ABS 0%, a 50/50 blend of PC and SAN (i.e. ABS without polybutadiene (PB)), was a brittle blend and showed a very high Tbd close to the Tg of SAN. Tbd did not seem to be influenced by Specimen Thickness. PC/ABS blends with 15 and 30% PB in ABS showed improved Tbd compared to PC/SAN and PC, indicating effective rubber toughening. Tbd decreased with decreasing Thickness for PC/ABS Specimens thicker than 1.5 mm. However, Tbd increased with decreasing Thickness for Specimens below 1.5 mm Thickness. In thin Specimens, the rubber-filled blend is less effective rubber toughening. The plane strain stress condition needed for rubber cavitation is apparently not present in thin Specimens.
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Polycarbonate and co-continuous polycarbonate/ABS blends: influence of Specimen Thickness
Polymer, 2002Co-Authors: J P F Inberg, R J GaymansAbstract:The influence of Specimen Thickness on the fracture behaviour of polycarbonate (PC) and co-continuous PC/ABS (50/50) blends was studied in single edge notch tensile tests at 1 m/s and different temperatures (−80 to 130 °C). Specimen Thickness ranged from 0.1 to 8 mm. In the co-continuous PC/ABS blends the rubber concentration in the ABS was 0, 15 and 30 wt%. The change in fracture toughness was typified by the change in brittle-to-ductile transition temperature (Tbd). Tbd of pure PC depended strongly on Specimen Thickness, leading to very low transition temperatures for thin PC Specimens. PC/ABS 0%, a 50/50 blend of PC and SAN (i.e. ABS without polybutadiene (PB)), was a brittle blend and showed a very high Tbd close to the Tg of SAN. Tbd did not seem to be influenced by Specimen Thickness. PC/ABS blends with 15 and 30% PB in ABS showed improved Tbd compared to PC/SAN and PC, indicating effective rubber toughening. Tbd decreased with decreasing Thickness for PC/ABS Specimens thicker than 1.5 mm. However, Tbd increased with decreasing Thickness for Specimens below 1.5 mm Thickness. In thin Specimens, the rubber-filled blend is less effective rubber toughening. The plane strain stress condition needed for rubber cavitation is apparently not present in thin Specimens.
W J Quadakkers - One of the best experts on this subject based on the ideXlab platform.
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Effect of Specimen Thickness on the growth rate of chromia scales on Ni-base alloys in high- and low-pO2 gases
Journal of Alloys and Compounds, 2020Co-Authors: J Zurek, G H Meier, E Essuman, M Hansel, L Singheiser, W J QuadakkersAbstract:Two types of experiments were carried out to study the oxidation behaviour of NiCr-base model alloys; thermogravimetric measurements for up to 72 h exposure at 1000 degrees C in synthetic air and isothermal exposures for up to 100 h at 1000 degrees C in laboratory air and in Ar-4%H-2-2%H2O. It was found that there is a significant effect of Specimen Thickness on the oxidation rate of all studied alloys. The growth rates of the chromia scales decrease with increasing Specimen Thickness in both air and the Ar-H-2-H2O mixture. Based on the present results in combination with recent literature data for ferritic steels, it is postulated that the decrease in rate is the result of compressive growth stresses in the scales which can relax by plastic deformation of the substrate for thin Specimens but are maintained at significant levels for thick Specimens. (C) 2007 Elsevier B.V. All rights reserved
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effect of Specimen Thickness on chromia scaling of ni25cr in n2 o2 h2o test gases at 1000 c
Materials at High Temperatures, 2015Co-Authors: M Hansel, E Turan, V Shemet, D Gruner, U Breuer, D Simon, Bronislava Gorr, H J Christ, W J QuadakkersAbstract:AbstractThe isothermal oxidation behaviour of a Ni25Cr model alloy was studied using Specimens of different Thicknesses at 1000°C in dry and wet N2–1%O2. The oxidation mechanisms were evaluated using thermogravimetry and SEM/electron backscatter diffraction analyses of oxide scale cross-sections. The oxidation rates decreased with increasing Specimen Thickness and increasing water vapour additions in the gas. The findings can be explained by considering the effect of H-defects and in-scale stress state on point defect concentrations in the chromia lattice.
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effect of Specimen Thickness on the growth rate of chromia scales on ni base alloys in high and low po2 gases
Journal of Alloys and Compounds, 2009Co-Authors: J Zurek, G H Meier, E Essuman, M Hansel, L Singheiser, W J QuadakkersAbstract:Abstract Two types of experiments were carried out to study the oxidation behaviour of NiCr-base model alloys; thermogravimetric measurements for up to 72 h exposure at 1000 °C in synthetic air and isothermal exposures for up to 100 h at 1000 °C in laboratory air and in Ar–4%H 2 –2%H 2 O. It was found that there is a significant effect of Specimen Thickness on the oxidation rate of all studied alloys. The growth rates of the chromia scales decrease with increasing Specimen Thickness in both air and the Ar–H 2 –H 2 O mixture. Based on the present results in combination with recent literature data for ferritic steels, it is postulated that the decrease in rate is the result of compressive growth stresses in the scales which can relax by plastic deformation of the substrate for thin Specimens but are maintained at significant levels for thick Specimens.
Ankit Srivastava - One of the best experts on this subject based on the ideXlab platform.
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effect of Specimen Thickness on the creep response of a ni based single crystal superalloy
Acta Materialia, 2012Co-Authors: Ankit Srivastava, S Gopagoni, A Needleman, V Seetharaman, Alexander Staroselsky, Rajarshi BanerjeeAbstract:Abstract Creep tests on Ni-based single-crystal superalloy sheet Specimens typically show greater creep strain rates and/or reduced strain or time to creep rupture for thinner Specimens than predicted by current theories, which predict a size-independent creep strain rate and creep rupture strain. This size-dependent creep response is termed the Thickness debit effect. To investigate the mechanism of the Thickness debit effect, isothermal, constant nominal stress creep tests were performed on uncoated PWA1484 Ni-based single-crystal superalloy sheet Specimens of Thicknesses 3.18 and 0.51 mm under two test conditions: 760 °C/758 MPa and 982 °C/248 MPa. The Specimens contained initial microvoids formed during the solidification and homogenization processes. The dependence of the creep response on Specimen Thickness differed under the two test conditions: at 760 °C/758 MPa there was a reduction in the creep strain and the time to rupture with decreasing section Thickness, whereas at 982 °C/248 MPa a decreased Thickness resulted in an increased creep rate even at low strain levels and a decreased time to rupture but with no systematic dependence of the creep strain to rupture on Specimen Thickness. For the Specimens tested at 760 °C/758 MPa microscopic analyses revealed that the thick Specimens exhibited a mixed failure mode of void growth and cleavage-like fracture while the predominant failure mode for the thin Specimens was cleavage-like fracture. The creep Specimens tested at 982 °C/248 MPa in air showed the development of surface oxides and a near-surface precipitate-free zone. Finite-element analysis revealed that the presence of the alumina layer at the free surface imposes a constraint that locally increases the stress triaxiality and changes the value of the Lode parameter (a measure of the third stress invariant). The surface cracks formed in the oxide scale were arrested by further oxidation; for a Thickness of 3.18 mm the failure mode was void nucleation, growth and coalescence, whereas for a Thickness of 0.51 mm there was a mixed mode of ductile and cleavage-like fracture.
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effect of Specimen Thickness on the creep response of a ni based single crystal superalloy preprint
2012Co-Authors: Ankit Srivastava, S Gopagoni, A Needleman, Rajarshi Banerjee, Alexander StaroselskyAbstract:Abstract : Creep tests on Ni-based single crystal superalloy sheet Specimens typically show greater creep strain rates and/or reduced strain or time to creep rupture for thinner Specimens than predicted by current theories which predict a size independent creep strain rate and creep rupture strain. This size dependent creep response is termed the Thickness debit effect. To investigate the mechanism of the Thickness debit effect, isothermal, constant nominal stress creep tests were performed on uncoated PWA1484 Ni-based single crystal superalloy sheet Specimens of Thicknesses 3.18mm and 0.51mm under two test conditions: 760◦C/758MPa and 982◦C/248MPa. The Specimens contained initial micro-voids formed during the solidification and homogenization processes. The dependence of the creep response on Specimen Thickness differed under the two test conditions: at 760◦C/758MPa there was a reduction in the creep strain and the time to rupture with decreasing section Thickness while at 982◦C/248MPa a decreased Thickness resulted in an increased creep rate even at low strain levels and a decreased time to rupture but with no systematic dependence of the creep.
J P F Inberg - One of the best experts on this subject based on the ideXlab platform.
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polycarbonate and co continuous polycarbonate abs blends influence of Specimen Thickness
Polymer, 2002Co-Authors: J P F Inberg, R J GaymansAbstract:The influence of Specimen Thickness on the fracture behaviour of polycarbonate (PC) and co-continuous PC/ABS (50/50) blends was studied in single edge notch tensile tests at 1 m/s and different temperatures (−80 to 130 °C). Specimen Thickness ranged from 0.1 to 8 mm. In the co-continuous PC/ABS blends the rubber concentration in the ABS was 0, 15 and 30 wt%. The change in fracture toughness was typified by the change in brittle-to-ductile transition temperature (Tbd). Tbd of pure PC depended strongly on Specimen Thickness, leading to very low transition temperatures for thin PC Specimens. PC/ABS 0%, a 50/50 blend of PC and SAN (i.e. ABS without polybutadiene (PB)), was a brittle blend and showed a very high Tbd close to the Tg of SAN. Tbd did not seem to be influenced by Specimen Thickness. PC/ABS blends with 15 and 30% PB in ABS showed improved Tbd compared to PC/SAN and PC, indicating effective rubber toughening. Tbd decreased with decreasing Thickness for PC/ABS Specimens thicker than 1.5 mm. However, Tbd increased with decreasing Thickness for Specimens below 1.5 mm Thickness. In thin Specimens, the rubber-filled blend is less effective rubber toughening. The plane strain stress condition needed for rubber cavitation is apparently not present in thin Specimens.
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Polycarbonate and co-continuous polycarbonate/ABS blends: influence of Specimen Thickness
Polymer, 2002Co-Authors: J P F Inberg, R J GaymansAbstract:The influence of Specimen Thickness on the fracture behaviour of polycarbonate (PC) and co-continuous PC/ABS (50/50) blends was studied in single edge notch tensile tests at 1 m/s and different temperatures (−80 to 130 °C). Specimen Thickness ranged from 0.1 to 8 mm. In the co-continuous PC/ABS blends the rubber concentration in the ABS was 0, 15 and 30 wt%. The change in fracture toughness was typified by the change in brittle-to-ductile transition temperature (Tbd). Tbd of pure PC depended strongly on Specimen Thickness, leading to very low transition temperatures for thin PC Specimens. PC/ABS 0%, a 50/50 blend of PC and SAN (i.e. ABS without polybutadiene (PB)), was a brittle blend and showed a very high Tbd close to the Tg of SAN. Tbd did not seem to be influenced by Specimen Thickness. PC/ABS blends with 15 and 30% PB in ABS showed improved Tbd compared to PC/SAN and PC, indicating effective rubber toughening. Tbd decreased with decreasing Thickness for PC/ABS Specimens thicker than 1.5 mm. However, Tbd increased with decreasing Thickness for Specimens below 1.5 mm Thickness. In thin Specimens, the rubber-filled blend is less effective rubber toughening. The plane strain stress condition needed for rubber cavitation is apparently not present in thin Specimens.