Rheological properties of the upper mantle in Canada from olivine microrheology

1980 ◽  
Vol 17 (11) ◽  
pp. 1499-1505 ◽  
Author(s):  
G. Ranalli
Keyword(s):  
Rheological Properties ◽  
Power Law ◽  
Upper Mantle ◽  
Depth Range ◽  
Grain Sizes ◽  
Diffusion Controlled ◽  
Linear Creep ◽  
Power Law Creep ◽  
Edge Dislocations ◽  
Lateral Variations

The rheological properties of the upper mantle for geotherms representative of shield and Cordilleran regions are studied on the basis of olivine microrheology. The equation for power-law creep, where the strain rate is dependent upon the diffusion-controlled climb of edge dislocations, is found to yield realistic values of creep strength and viscosity, when the experimentally determined parameters for dry olivine are used. For grain sizes larger than 0.01 cm, power-law creep is predominant over linear creep in the upper mantle, but the increasing importance of grain-boundary diffusion with decreasing depth makes linear creep a very likely deformation mechanism in the upper lithosphere.The differences between shield and Cordilleran geotherms are reflected in lateral variations in the rheological properties of the lithosphere and upper mantle. The lithosphere is thinner, and the upper mantle softer, in the Cordilleran region. The lateral variations in effective viscosity in the 100–200 km depth range are between one and two orders of magnitude.

scholarly journals New Developments in Understanding Harper-Dorn, Five- power Law Creep and Power-law Breakdown

2020 ◽  
Author(s):  
michael kassner
Keyword(s):  
Stress Exponent ◽  
Power Law ◽  
Dislocation Network ◽  
Creep Equation ◽  
Self Diffusion ◽  
Wide Range ◽  
Recent Developments ◽  
Initial Dislocation Density ◽  
Power Law Creep ◽  
Edge Dislocations

This paper discusses recent developments in creep, over a wide range of temperature, that mqy change our understanding of creep. The five-power law creep exponent (3.5 to 7) has never been explained in fundamental terms. The best the scientific community has done is to develop a natural three power-law creep equation that falls short of rationalizing the higher stress exponents that are typically five. This inability has persisted for many decades. Computational work examining the stress-dependence of the climb rate of edge dislocations we may rationalize the phenomenological creep equations. Harper-Dorn creep, “discovered” over 60 years ago has been immersed in controversy. Some investigators have insisted that a stress exponent of one is reasonable. Others believe that the observation of a stress exponent of one is a consequence of dislocation network frustration. Others believe the stress exponent is artificial due to the inclusion of restoration mechanisms such as dynamic recrystallization or grain growth that is not of any consequence in the five power-law regime. Also, the experiments in the Harper-Dorn regime, which accumulate strain very slowly (sometimes over a year) may not have attained a true steady state. New theories suggest that absence or presence of Harper-Dorn may be a consequence of the initial dislocation density. Novel experimental work suggests that power-law breakdown may be a consequence of a supersaturation of vacancies which increase self-diffusion.

Is power-law creep diffusion-controlled?

1978 ◽  
Vol 26 (4) ◽  
pp. 629-637 ◽  
Author(s):  
J.P. Poirier
Keyword(s):  
Power Law ◽  
Diffusion Controlled ◽  
Power Law Creep

scholarly journals New Developments in Understanding Harper–Dorn, Five-Power Law Creep and Power-Law Breakdown

Metals ◽  
2020 ◽  
Vol 10 (10) ◽  
pp. 1284
Author(s):  
Michael E. Kassner
Keyword(s):  
Stress Exponent ◽  
Power Law ◽  
Dislocation Network ◽  
Creep Equation ◽  
Self Diffusion ◽  
Wide Range ◽  
Recent Developments ◽  
Initial Dislocation Density ◽  
Power Law Creep ◽  
Edge Dislocations

This paper discusses recent developments in creep, over a wide range of temperature, that may change our understanding of creep. The five-power law creep exponent (3.5–7) has never been explained in fundamental terms. The best the scientific community has done is to develop a natural three power-law creep equation that falls short of rationalizing the higher stress exponents that are typically five. This inability has persisted for many decades. Computational work examining the stress-dependence of the climb rate of edge dislocations may rationalize the phenomenological creep equations. Harper–Dorn creep, “discovered” over 60 years ago, has been immersed in controversy. Some investigators have insisted that a stress exponent of one is reasonable. Others believe that the observation of a stress exponent of one is a consequence of dislocation network frustration. Others believe the stress exponent is artificial due to the inclusion of restoration mechanisms, such as dynamic recrystallization or grain growth that is not of any consequence in the five power-law regime. Also, the experiments in the Harper–Dorn regime, which accumulate strain very slowly (sometimes over a year), may not have attained a true steady state. New theories suggest that the absence or presence of Harper–Dorn may be a consequence of the initial dislocation density. Novel experimental work suggests that power-law breakdown may be a consequence of a supersaturation of vacancies which increase self-diffusion.

scholarly journals Three Regions in the Power-Law Creep Regime of TiAl

1992 ◽  
Vol 33 (12) ◽  
pp. 1182-1184 ◽  
Author(s):  
Yukio Ishikawa ◽  
Kouichi Maruyama ◽  
Hiroshi Oikawa
Keyword(s):  
Power Law ◽  
Power Law Creep ◽  
Creep Regime

A simple FE approach to study microstructural influences in power-law creep

2012 ◽  
Vol 52 (1) ◽  
pp. 73-76 ◽  
Author(s):  
Cornelia Pein ◽  
Christof Sommitsch
Keyword(s):  
Power Law ◽  
Power Law Creep

scholarly journals Rheological properties of emulsions stabilized by green banana (Musa cavendishii) pulp fitted by power law model

2009 ◽  
Vol 52 (6) ◽  
pp. 1541-1553 ◽  
Author(s):  
Dayane Rosalyn Izidoro ◽  
Agnes de Paula Scheer ◽  
Maria-Rita Sierakowsk
Keyword(s):  
Response Surface Methodology ◽  
Rheological Properties ◽  
Response Surface ◽  
Power Law ◽  
Cone Angle ◽  
Rheological Behaviour ◽  
Quadratic Model ◽  
Soy Oil ◽  
Power Law Model ◽  
Green Banana

In this work, the rheological behaviour of emulsions (mayonnaises) stabilized by green banana pulp using the response surface methodology was studied. In addition, the emulsions stability was investigated. Five formulations were developed, according to design for constrained surfaces and mixtures, with the proportion, respectively: water/soy oil/green banana pulp: F1 (0.10/0.20/0.70), F2 (0.20/0.20/0.60), F3 (0.10/0.25/0.65), F4 (0.20/0.25/0.55) and F5 (0.15/0.225/0.625) .Emulsions rheological properties were performed with a rotational Haake Rheostress 600 rheometer and a cone and plate geometry sensor (60-mm diameter, 2º cone angle), using a gap distance of 1mm. The emulsions showed pseudoplastic behaviour and were adequately described by the Power Law model. The rheological responses were influenced by the difference in green banana pulp proportions and also by the temperatures (10 and 25ºC). The formulations with high pulp content (F1 and F3) presented higher shear stress and apparent viscosity. Response surface methodology, described by the quadratic model,showed that the consistency coefficient (K) increased with the interaction between green banana pulp and soy oil concentration and the water fraction contributed to the flow behaviour index increase for all emulsions samples. Analysis of variance showed that the second-order model had not significant lack-of-fit and a significant F-value, indicating that quadratic model fitted well into the experimental data. The emulsions that presented better stability were the formulations F4 (0.20/0.25/0.55) and F5 (0.15/0.225/0.625).

scholarly journals Rapid mantle flow with power-law creep explains deformation after the 2011 Tohoku mega-quake

2019 ◽  
Vol 10 (1) ◽  
Author(s):  
Ryoichiro Agata ◽  
Sylvain D. Barbot ◽  
Kohei Fujita ◽  
Mamoru Hyodo ◽  
Takeshi Iinuma ◽  
...  
Keyword(s):  
Power Law ◽  
Mantle Flow ◽  
Power Law Creep
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