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| 2. |
- Li, Wen-Bin, et al.
(författare)
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Instantaneous and residual stresses developed in hot isostatic pressing of metals and ceramics
- 1991
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Ingår i: Metallurgical and Materials Transactions. A. - 1073-5623 .- 1543-1940. ; 22:5, s. 1071-1078
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Tidskriftsartikel (refereegranskat)abstract
- Under many conditions, hot isostatic pressing (HIP) of metallic or ceramic porous preforms occurs by the densification of a shell at the surface of the preform, which then thickens until the whole sample is fully densified. The development of such a dense shell reduces the effective pressure acting to densify the remaining porosity. Furthermore, this pressure difference can lead to anisotropic creep of the shell, and this may be a contributary cause of shape change of samples during HIP. The stresses occurring during cooling of the sample and the residual stresses are calculated as a function of all of the various material and pressing parameters. It is found that, in many cases, the cooling stresses which are tensile at the surface may well be large enough to cause cracking in ceramic samples
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| 5. |
- Li, Wen-Bin, et al.
(författare)
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The effect of non-uniform densification during hot isostatic pressing
- 1992
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Ingår i: Hot isostatic pressing. - : Elsevier. - 185166744X ; , s. 23-28
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Konferensbidrag (refereegranskat)abstract
- Hot isostatic pressing (HIPing) is an extremely efficient way of densifying ceramic and metallic powders, or for healing porosity in castings. However, depending on the parameters of pressure, temperature, heating rate and sample size, can result in a non-uniform mode of densification. This mainly occurs when a rapidly heated sample, or a sample of large size, densifies quickly at the surface to produce in effect a fully dense, hard shell. It is shown that there can be a number of negative factors resulting from this, including reduced rates of densification, decrease of effective pressure, sample shape change, non-uniform shrinkage and the development of residual stresses in the sample etc. The materials mentioned are copper, steel, and Al sub 2 O sub 3
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| 7. |
- Ringer, S.P, et al.
(författare)
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Effect of particle pinning on recrystallization of a titanium-stabilized stainless steel
- 1990
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Ingår i: Recrystallization '90. - Warrendale, Pa : Minerals, Metals & Materials Society. - 0873391241 ; , s. 483-489
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Konferensbidrag (refereegranskat)abstract
- Recent work has shown that maintenance of coherency between stable particles and matrix after the bypassing of grain boundaries during grain growth can occur to reduce the energy of the particle /matrix interface, and that this occurs by a diffusion controlled bodily rotation of the particle. Since coherent particles, in general, offer more resistance to migrating boundaries than incoherent ones, a particle rotation, if it occurs, should tend to help refine grain size following recrystallization. The recrystallization and early stages of grain growth of a deformed Ti-stabilized austenitic stainless steel (321) containing coherent and semicoherent TiC precipitates has been studied by light optical and transmission electron microscopy. Evidence for a particle rotation following recrystallization of this alloy is presented. A model explaining this behaviour is developed and discussed in terms of the likely effects phenomena such as this and particle reversion will have on the recrystallization behaviour of these steels
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| 8. |
- Tan, Z., et al.
(författare)
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On analysis and measurement of residual stresses in the bending of sheet metals
- 1994
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Ingår i: International Journal of Mechanical Sciences. - : Elsevier BV. - 0020-7403 .- 1879-2162. ; 36:5, s. 483-491
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Tidskriftsartikel (refereegranskat)abstract
- A new method for evaluating distribution of residual stresses in bent sheet metals is presented. Due to the non-uniform distribution of strain and stress across thickness, springback on unloading induces residual stress in a bent specimen. The authors have formulated the problem and shown that the springback and residual stresses can be expressed as a function of geometric parameters and material properties of sheet metals, e.g. bending curvature, thickness, Young's modulus, work-hardening index, etc. The layer-removing method was used to determine the residual stresses in the study. By simulating the layer-removing process, analytical measurement of the residual stress was made. The analytical results were compared with the experimental data measured, and a good agreement was found.
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