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Jiahau Yan - One of the best experts on this subject based on the ideXlab platform.
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the effects of viscoelastic parameters on Residual Stress Development in a zirconia glass bilayer dental ceramic
Dental Materials, 2008Co-Authors: Burak Taskonak, Gilberto A Borges, John J Mecholsky, K J Anusavice, Keith B Moore, Jiahau YanAbstract:Abstract Objectives The aim of this study was to test the hypothesis that the Residual Stresses in a zirconia-based bilayer dental composite system can be tailored through heat treatment above and below the glass transition temperature of glass veneers. Methods Ceramic bilayer disc specimens were prepared from a zirconia core and a glass veneer. Each bilayer ceramic group was heat treated 40 °C below, 20 °C and 40 °C above and at the glass transition temperature of the glass veneer, and cooled using a fast or a slow cooling rate. Specimens were tested for flexure strength using a biaxial bending fixture. Residual Stresses were calculated using a fracture mechanics approach. Results Heat treatments produced significant differences ( p ≤ 0.05) between the mean flexural strengths of the heat treatment groups when the specimens were cooled using a fast cooling rate. However, there was not a significant difference ( p > 0.05) between the mean flexural strengths of the heat treatment groups when a slow cooling rate was used. Fractures initiated from the veneer surfaces of the specimens. Significance Heat treatment above and below the glass transition temperature of the veneer layer, and the cooling rate have a significant effect on the flexural strength of the bilayer ceramic laminates. The existence of Residual compressive Stress is the most likely reason for the observed strength increases. Residual Stresses can be modified using the elastic-viscoelastic relaxation behavior of a glass veneer.
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The effects of viscoelastic parameters on Residual Stress Development in a zirconia/glass bilayer dental ceramic
Dental materials : official publication of the Academy of Dental Materials, 2008Co-Authors: Burak Taskonak, Gilberto A Borges, John J Mecholsky, K J Anusavice, B. Keith Moore, Jiahau YanAbstract:Abstract Objectives The aim of this study was to test the hypothesis that the Residual Stresses in a zirconia-based bilayer dental composite system can be tailored through heat treatment above and below the glass transition temperature of glass veneers. Methods Ceramic bilayer disc specimens were prepared from a zirconia core and a glass veneer. Each bilayer ceramic group was heat treated 40 °C below, 20 °C and 40 °C above and at the glass transition temperature of the glass veneer, and cooled using a fast or a slow cooling rate. Specimens were tested for flexure strength using a biaxial bending fixture. Residual Stresses were calculated using a fracture mechanics approach. Results Heat treatments produced significant differences ( p ≤ 0.05) between the mean flexural strengths of the heat treatment groups when the specimens were cooled using a fast cooling rate. However, there was not a significant difference ( p > 0.05) between the mean flexural strengths of the heat treatment groups when a slow cooling rate was used. Fractures initiated from the veneer surfaces of the specimens. Significance Heat treatment above and below the glass transition temperature of the veneer layer, and the cooling rate have a significant effect on the flexural strength of the bilayer ceramic laminates. The existence of Residual compressive Stress is the most likely reason for the observed strength increases. Residual Stresses can be modified using the elastic-viscoelastic relaxation behavior of a glass veneer.
J Romero - One of the best experts on this subject based on the ideXlab platform.
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effect of the forging pressure on the microstructure and Residual Stress Development in ti 6al 4v linear friction welds
Acta Materialia, 2009Co-Authors: J Romero, Michael Preuss, Moataz M Attallah, M Karadge, S BrayAbstract:Abstract A detailed investigation for the influence of the forging pressure on the microstructural, microhardness, and Residual Stress Development in linear friction welded Ti–6Al–4V has been performed. Energy dispersive synchrotron X-ray diffraction scans were performed in the three principle directions across the welds to characterise the Residual Stress Development. Since the welding process results in dramatic microstructural changes, it was necessary to identify any variations of the strain-free lattice parameter across the weld regions for accurate Stress calculations. This was achieved by undertaking biaxial sin2ψ laboratory X-ray diffraction measurements on cross-weld slices cut from the centre of the welds. The cross-weld crystallographic texture was assessed using electron-backscattered diffraction. The experimental data identified a strong relationship between forging pressure and Residual Stresses and weld microstructure, whereby the Residual Stresses, the width of the weld region, and the α-Ti texture strength in the weld region generally decreased with the increase in forging pressure.
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Effect of the forging pressure on the microstructure and Residual Stress Development in Ti–6Al–4V linear friction welds
Acta Materialia, 2009Co-Authors: J Romero, Michael Preuss, Moataz M Attallah, M Karadge, Simon Edward BrayAbstract:Abstract A detailed investigation for the influence of the forging pressure on the microstructural, microhardness, and Residual Stress Development in linear friction welded Ti–6Al–4V has been performed. Energy dispersive synchrotron X-ray diffraction scans were performed in the three principle directions across the welds to characterise the Residual Stress Development. Since the welding process results in dramatic microstructural changes, it was necessary to identify any variations of the strain-free lattice parameter across the weld regions for accurate Stress calculations. This was achieved by undertaking biaxial sin2ψ laboratory X-ray diffraction measurements on cross-weld slices cut from the centre of the welds. The cross-weld crystallographic texture was assessed using electron-backscattered diffraction. The experimental data identified a strong relationship between forging pressure and Residual Stresses and weld microstructure, whereby the Residual Stresses, the width of the weld region, and the α-Ti texture strength in the weld region generally decreased with the increase in forging pressure.
Moataz M Attallah - One of the best experts on this subject based on the ideXlab platform.
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microstructural and Residual Stress Development due to inertia friction welding in ti 6246
Metallurgical and Materials Transactions A-physical Metallurgy and Materials Science, 2012Co-Authors: Moataz M Attallah, Michael Preuss, Chatri Boonchareon, Darren J Hughes, Christopher Dungey, John E Daniels, Axel Steuwer, G J BaxterAbstract:A thorough investigation has been performed to assess the microstructural properties, mechanical properties (hardness and elastic modulus), and Residual Stress Development in Ti-6Al-2Sn-4Zr-6Mo (Ti-6246) inertia friction welds in the as-welded and postweld heat-treated conditions. It was evident that the thermomechanical deformation in the weld region occurred above the β transus, forming dynamically recrystallized β grains and precipitating acicular α within the β grains, which resulted in a localized hardness increase. In the heat-affected zone, a ghost microstructure of the base metal formed because of the absence of sufficient time for diffusion, resulting in Mo segregation in the prior primary α plates. Energy-dispersive synchrotron X-ray diffraction and neutron diffraction were used to assess the Residual Stress Development in the three principal directions. The variation in the unstrained lattice parameters across the weld regions was established by imposing a Stress balance on the axial Stress component in the radial direction. It was found that the maximum Stresses occurred in the hoop direction, with significantly lower Stresses present in the radial and axial directions. The maximum tensile hoop Stresses were located at ~4 mm from the weld centerline and not at the dynamically recrystallized β-rich weld zone. This was associated with the α → β phase transformation and the subsequent acicular α precipitation within the region surrounding the weld centerline.
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effect of the forging pressure on the microstructure and Residual Stress Development in ti 6al 4v linear friction welds
Acta Materialia, 2009Co-Authors: J Romero, Michael Preuss, Moataz M Attallah, M Karadge, S BrayAbstract:Abstract A detailed investigation for the influence of the forging pressure on the microstructural, microhardness, and Residual Stress Development in linear friction welded Ti–6Al–4V has been performed. Energy dispersive synchrotron X-ray diffraction scans were performed in the three principle directions across the welds to characterise the Residual Stress Development. Since the welding process results in dramatic microstructural changes, it was necessary to identify any variations of the strain-free lattice parameter across the weld regions for accurate Stress calculations. This was achieved by undertaking biaxial sin2ψ laboratory X-ray diffraction measurements on cross-weld slices cut from the centre of the welds. The cross-weld crystallographic texture was assessed using electron-backscattered diffraction. The experimental data identified a strong relationship between forging pressure and Residual Stresses and weld microstructure, whereby the Residual Stresses, the width of the weld region, and the α-Ti texture strength in the weld region generally decreased with the increase in forging pressure.
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Effect of the forging pressure on the microstructure and Residual Stress Development in Ti–6Al–4V linear friction welds
Acta Materialia, 2009Co-Authors: J Romero, Michael Preuss, Moataz M Attallah, M Karadge, Simon Edward BrayAbstract:Abstract A detailed investigation for the influence of the forging pressure on the microstructural, microhardness, and Residual Stress Development in linear friction welded Ti–6Al–4V has been performed. Energy dispersive synchrotron X-ray diffraction scans were performed in the three principle directions across the welds to characterise the Residual Stress Development. Since the welding process results in dramatic microstructural changes, it was necessary to identify any variations of the strain-free lattice parameter across the weld regions for accurate Stress calculations. This was achieved by undertaking biaxial sin2ψ laboratory X-ray diffraction measurements on cross-weld slices cut from the centre of the welds. The cross-weld crystallographic texture was assessed using electron-backscattered diffraction. The experimental data identified a strong relationship between forging pressure and Residual Stresses and weld microstructure, whereby the Residual Stresses, the width of the weld region, and the α-Ti texture strength in the weld region generally decreased with the increase in forging pressure.
Michael Preuss - One of the best experts on this subject based on the ideXlab platform.
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microstructural and Residual Stress Development due to inertia friction welding in ti 6246
Metallurgical and Materials Transactions A-physical Metallurgy and Materials Science, 2012Co-Authors: Moataz M Attallah, Michael Preuss, Chatri Boonchareon, Darren J Hughes, Christopher Dungey, John E Daniels, Axel Steuwer, G J BaxterAbstract:A thorough investigation has been performed to assess the microstructural properties, mechanical properties (hardness and elastic modulus), and Residual Stress Development in Ti-6Al-2Sn-4Zr-6Mo (Ti-6246) inertia friction welds in the as-welded and postweld heat-treated conditions. It was evident that the thermomechanical deformation in the weld region occurred above the β transus, forming dynamically recrystallized β grains and precipitating acicular α within the β grains, which resulted in a localized hardness increase. In the heat-affected zone, a ghost microstructure of the base metal formed because of the absence of sufficient time for diffusion, resulting in Mo segregation in the prior primary α plates. Energy-dispersive synchrotron X-ray diffraction and neutron diffraction were used to assess the Residual Stress Development in the three principal directions. The variation in the unstrained lattice parameters across the weld regions was established by imposing a Stress balance on the axial Stress component in the radial direction. It was found that the maximum Stresses occurred in the hoop direction, with significantly lower Stresses present in the radial and axial directions. The maximum tensile hoop Stresses were located at ~4 mm from the weld centerline and not at the dynamically recrystallized β-rich weld zone. This was associated with the α → β phase transformation and the subsequent acicular α precipitation within the region surrounding the weld centerline.
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Inertia friction welding (IFW) for aerospace applications
Welding and Joining of Aerospace Materials, 2012Co-Authors: Mm Attallah, Michael PreussAbstract:Abstract: The use of inertia welding in the aerospace industry has been steadily increasing owing to the significant improvements it provides in joint quality, compared with the use of fusion welding. This chapter introduces the process, with respect to its operation, parameters, differences from other friction welding techniques and equipment. It also explains the application of the technique and the selection of the process parameters, and the different mathematical, analytical and numerical approaches that are used to model the thermal fields and Residual Stress Development. Details of the microstructural, mechanical properties and Residual Stress Development in inertia friction-welded Ni-based superalloys, titanium alloys, steels and other alloys are also discussed.
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effect of the forging pressure on the microstructure and Residual Stress Development in ti 6al 4v linear friction welds
Acta Materialia, 2009Co-Authors: J Romero, Michael Preuss, Moataz M Attallah, M Karadge, S BrayAbstract:Abstract A detailed investigation for the influence of the forging pressure on the microstructural, microhardness, and Residual Stress Development in linear friction welded Ti–6Al–4V has been performed. Energy dispersive synchrotron X-ray diffraction scans were performed in the three principle directions across the welds to characterise the Residual Stress Development. Since the welding process results in dramatic microstructural changes, it was necessary to identify any variations of the strain-free lattice parameter across the weld regions for accurate Stress calculations. This was achieved by undertaking biaxial sin2ψ laboratory X-ray diffraction measurements on cross-weld slices cut from the centre of the welds. The cross-weld crystallographic texture was assessed using electron-backscattered diffraction. The experimental data identified a strong relationship between forging pressure and Residual Stresses and weld microstructure, whereby the Residual Stresses, the width of the weld region, and the α-Ti texture strength in the weld region generally decreased with the increase in forging pressure.
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Effect of the forging pressure on the microstructure and Residual Stress Development in Ti–6Al–4V linear friction welds
Acta Materialia, 2009Co-Authors: J Romero, Michael Preuss, Moataz M Attallah, M Karadge, Simon Edward BrayAbstract:Abstract A detailed investigation for the influence of the forging pressure on the microstructural, microhardness, and Residual Stress Development in linear friction welded Ti–6Al–4V has been performed. Energy dispersive synchrotron X-ray diffraction scans were performed in the three principle directions across the welds to characterise the Residual Stress Development. Since the welding process results in dramatic microstructural changes, it was necessary to identify any variations of the strain-free lattice parameter across the weld regions for accurate Stress calculations. This was achieved by undertaking biaxial sin2ψ laboratory X-ray diffraction measurements on cross-weld slices cut from the centre of the welds. The cross-weld crystallographic texture was assessed using electron-backscattered diffraction. The experimental data identified a strong relationship between forging pressure and Residual Stresses and weld microstructure, whereby the Residual Stresses, the width of the weld region, and the α-Ti texture strength in the weld region generally decreased with the increase in forging pressure.
Simon Edward Bray - One of the best experts on this subject based on the ideXlab platform.
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Effect of the forging pressure on the microstructure and Residual Stress Development in Ti–6Al–4V linear friction welds
Acta Materialia, 2009Co-Authors: J Romero, Michael Preuss, Moataz M Attallah, M Karadge, Simon Edward BrayAbstract:Abstract A detailed investigation for the influence of the forging pressure on the microstructural, microhardness, and Residual Stress Development in linear friction welded Ti–6Al–4V has been performed. Energy dispersive synchrotron X-ray diffraction scans were performed in the three principle directions across the welds to characterise the Residual Stress Development. Since the welding process results in dramatic microstructural changes, it was necessary to identify any variations of the strain-free lattice parameter across the weld regions for accurate Stress calculations. This was achieved by undertaking biaxial sin2ψ laboratory X-ray diffraction measurements on cross-weld slices cut from the centre of the welds. The cross-weld crystallographic texture was assessed using electron-backscattered diffraction. The experimental data identified a strong relationship between forging pressure and Residual Stresses and weld microstructure, whereby the Residual Stresses, the width of the weld region, and the α-Ti texture strength in the weld region generally decreased with the increase in forging pressure.