The non-uniform flow of polycrystals by grain-boundary sliding accommodated by power-law creep

1975 ◽  
Vol 23 (4) ◽  
pp. 425-440 ◽  
Author(s):  
F.W Crossman ◽  
M.F Ashby
Keyword(s):  
Grain Boundary ◽  
Power Law ◽  
Grain Boundary Sliding ◽  
Uniform Flow ◽  
Boundary Sliding ◽  
Power Law Creep

scholarly journals Modelling of the densification of polar firn: characterization of the snow–firn transition

1998 ◽  
Vol 26 ◽  
pp. 39-44 ◽  
Author(s):  
L. Arnaud ◽  
V. Lipenkov ◽  
J. M Barnola ◽  
M. Gay ◽  
P. Duval
Keyword(s):  
Grain Boundary ◽  
Power Law ◽  
Grain Boundary Sliding ◽  
Boundary Sliding ◽  
Power Law Creep

The transformation of dry snow to firn is described by the transition between densification by deformationless restacking and densification by power-law creep. The observed decrease with temperature of the density at the snow-firn transition seems to result from the competition between grain-boundary sliding and power-law creep. These two densification processess occur concurrently in snow, although there are probably micro-regions in which sliding alone occurs. Validation of a geometrical densification model developed for ceramics has been obtained from densification data from several Antarctic and Greenland sites and from the characterization of the structure of polar firn.

scholarly journals Modelling of the densification of polar firn: characterization of the snow–firn transition

1998 ◽  
Vol 26 ◽  
pp. 39-44 ◽  
Author(s):  
L. Arnaud ◽  
V. Lipenkov ◽  
J. M Barnola ◽  
M. Gay ◽  
P. Duval
Keyword(s):  
Grain Boundary ◽  
Power Law ◽  
Grain Boundary Sliding ◽  
Boundary Sliding ◽  
Power Law Creep

The transformation of dry snow to firn is described by the transition between densification by deformationless restacking and densification by power-law creep. The observed decrease with temperature of the density at the snow-firn transition seems to result from the competition between grain-boundary sliding and power-law creep. These two densification processess occur concurrently in snow, although there are probably micro-regions in which sliding alone occurs. Validation of a geometrical densification model developed for ceramics has been obtained from densification data from several Antarctic and Greenland sites and from the characterization of the structure of polar firn.

scholarly journals Modelling the transition from grain-boundary sliding to power-law creep in dry snow densification

2021 ◽  
pp. 1-14
Author(s):  
Elizabeth M. Morris ◽  
Lynn N. Montgomery ◽  
Robert Mulvaney
Keyword(s):  
Grain Boundary ◽  
Transition Zone ◽  
Power Law ◽  
Transition Density ◽  
Grain Boundary Sliding ◽  
Smooth Transition ◽  
Physically Based ◽  
Boundary Sliding ◽  
Power Law Creep ◽  
Stage 1

Abstract This paper presents a physics-based macroscale model for the densification of dry snow which provides for a smooth transition between densification by grain-boundary sliding (stage 1) and densification by power-law creep (stage 2). The model uses established values of the stage 1 and 2 densification rates away from the transition zone and two transition parameters with a simple physical basis: the transition density and the half-width of the transition zone. It has been calibrated using density profiles from the SUMup database and physically based expressions for the transition parameters have been derived. The transition model produces better predictions of the depth of the nominal bubble close-off horizon than the Herron and Langway model, both in its classical form and in a recent version with re-optimised densification rates.

scholarly journals Анализ механизмов уплотнения термоэлектрических порошков скуттерудитов и сплавов Гейслера в процессе активированного полем спекания

2021 ◽  
Vol 55 (12) ◽  
pp. 1132
Author(s):  
А.С. Тукмакова ◽  
Н.И. Хахилев ◽  
Д.Б. Щеглова ◽  
В.Д. Насонов ◽  
А.П. Новицкий ◽  
...  
Keyword(s):  
Grain Boundary ◽  
Heusler Alloys ◽  
Rate Sensitivity ◽  
Grain Boundary Sliding ◽  
Creep Mechanism ◽  
Diffusional Creep ◽  
Creep Model ◽  
Ceramic Powders ◽  
Boundary Sliding ◽  
Power Law Creep

The analysis of the shrinkage rate of powders, based on the power-law creep model of a porous body, was carried out in this paper to calculate the compaction parameters of CoSb3-based skutterudites and Fe2VAl-based Heusler alloys within field-activated sintering. It was indicated that this method, which had already been used for metal and ceramic powders, is applicable for thermoelectric powders. The values of strain rate sensitivity were obtained, and the corresponding powder compaction mechanisms have been defined. The main creep mechanism for skutterudites was found to be a dislocation climb, that later was replaced by grain boundary sliding, and the last sintering stage was associated with diffusional creep. The main creep mechanism for Heusler alloys was grain boundary sliding, later replaced by diffusional creep.

Examination of Fracture Interfaces in Silicon Nitride

1975 ◽  
Vol 33 ◽  
pp. 60-61
Author(s):  
Nancy J. Tighe
Keyword(s):  
Silicon Nitride ◽  
Grain Boundary ◽  
Crack Growth ◽  
Subcritical Crack Growth ◽  
Slow Crack Growth ◽  
Ceramic Materials ◽  
Grain Boundary Sliding ◽  
Boundary Phase ◽  
Turbine Engines ◽  
Boundary Sliding

Silicon nitride is one of the ceramic materials being considered for the components in gas turbine engines which will be exposed to temperatures of 1000 to 1400°C. Test specimens from hot-pressed billets exhibit flexural strengths of approximately 50 MN/m2 at 1000°C. However, the strength degrades rapidly to less than 20 MN/m2 at 1400°C. The strength degradition is attributed to subcritical crack growth phenomena evidenced by a stress rate dependence of the flexural strength and the stress intensity factor. This phenomena is termed slow crack growth and is associated with the onset of plastic deformation at the crack tip. Lange attributed the subcritical crack growth tb a glassy silicate grain boundary phase which decreased in viscosity with increased temperature and permitted a form of grain boundary sliding to occur.

INTERNAL FRICTION PEAKS CONNECTED WITH GRAIN BOUNDARY SLIDING IN Al

1983 ◽  
Vol 44 (C9) ◽  
pp. C9-759-C9-764
Author(s):  
E. Bonetti ◽  
A. Cavallini ◽  
E. Evangelista ◽  
P. Gondi
Keyword(s):  
Internal Friction ◽  
Grain Boundary ◽  
Grain Boundary Sliding ◽  
Boundary Sliding
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