A variation of the kinetic creep equation

1982 ◽  
Vol 14 (1) ◽  
pp. 105-108 ◽  
Author(s):  
V. N. Kiselevskii
Keyword(s):  
Creep Equation ◽  
Kinetic Creep

Creep Parameters for Pile Settlement Equations

1989 ◽  
Vol 111 (4) ◽  
pp. 258-263
Author(s):  
D. Stelzer ◽  
O. B. Andersland
Keyword(s):  
Static Load ◽  
Experimental Tests ◽  
Sand Particle ◽  
Shear Stresses ◽  
Frozen Ground ◽  
Creep Equation ◽  
Frozen Sand ◽  
Pile Settlement ◽  
Ice Content ◽  
Friction Pile

Friction pile settlement in frozen ground is tyically predicted on the basis of a creep equation relating shear stresses at the soil/pile interface to pile displacement rates. Creep parameters are used to characterize soil type, soil/ice structure, temperature, and loading conditions. Experimental tests involving model steel piles embedded in frozen sand provided data showing that change in a given test variable can alter the numerical value for some of the creep parameters. The test variables included static, incremental, and dynamic loading; pile surface roughness; soil ice content; and sand particle size. Changes observed included the apparent effect on creep rate when a small dynamic load was superimposed on the static load. A tabulation of observed creep parameter changes is included.

scholarly journals A Study on the Tension Creep Equation during Hydration in the Early Age.

1999 ◽  
pp. 43-53
Author(s):  
Isamu YOSHITAKE ◽  
Hideaki NAKAMURA ◽  
Senji NAGAI ◽  
Sumio HAMADA
Keyword(s):  
Early Age ◽  
Creep Equation

On the Measurement of Material Creep Parameters by Nanoindentation

2004 ◽  
Vol 841 ◽  
Author(s):  
J. A. LaManna ◽  
W. C. Oliver ◽  
G. M. Pharr
Keyword(s):  
Material Constant ◽  
Uniaxial Stress ◽  
Complete Characterization ◽  
Indentation Load ◽  
Amorphous Selenium ◽  
Load History ◽  
Time Data ◽  
Creep Equation ◽  
Uniaxial Creep ◽  
Material Creep

ABSTRACTPrevious studies of how material creep parameters can be measured by nanoindentation testing have focused mostly on measurement of the stress exponent for creep, n, and the activation energy, Qc. However, a more complete characterization requires that the material constant A in the uniaxial creep equation εu =Aσn (where εu is the uniaxial strain rate and σ is the uniaxial stress) also be evaluated. Here, we begin to address this issue by performing simple nanoindentation creep experiments in amorphous selenium at temperatures above and below the glass transition. At 35°C and above, the material exhibits a simple linear viscous creep behavior that is load history independent. This allows the parameter A to be determined from the indentation load-displacement-time data by means of an analytical solution. To examine the validity of the approach, values of the parameter A measured in nanoindentation tests are compared to independent measurements obtained in uniaxial tension creep experiments.

Biaxial Thermal Creep of Alloy 617 and Alloy 230 for VHTR Applications

2014 ◽  
Author(s):  
Kun Mo ◽  
Wei Lv ◽  
Hsiao-Ming Tung ◽  
Di Yun ◽  
Yinbin Miao ◽  
...  
Keyword(s):  
High Temperature ◽  
Thermal Creep ◽  
Secondary Creep ◽  
Alloy 617 ◽  
Creep Equation ◽  
Creep Stress ◽  
High Temperature Mechanical Properties ◽  
Inconel 617 ◽  
Creep Regime ◽  
Secondary Regime

In this study, we employed pressurized creep tubes to investigate the biaxial thermal creep behavior of Inconel 617 (Alloy 617) and Haynes 230 (Alloy 230). Both alloys have been considered to be the primary candidate structural materials for very high temperature reactors (VHTRs) due to their exceptional high-temperature mechanical properties. The current creep experiments were conducted at 900°C for the effective stress range of 15–35 MPa. For both alloys, complete creep strain development with primary, secondary, and tertiary regimes were observed in all studied conditions. The tertiary creep was found to be dominant in the entire creep lives of both alloys. With increasing applied creep stress, the fraction of the secondary creep regime decreases. The nucleation, diffusion, and coarsening of creep voids and carbides on grain boundaries was found to be the main reason for the limited secondary regime, and was also found to be the major cause of creep fracture. The creep curves computed using the adjusted creep equation of the form ε = Aσ cosh−1(1 + rt) + Pσntm agree well with the experimental results for both alloys at the temperatures of 850–950°C. Paper published with permission.

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.

scholarly journals Multilayer method for solving a problem of metals rupture under creep conditions

2019 ◽  
Vol 23 (Suppl. 2) ◽  
pp. 575-582 ◽  
Author(s):  
Evgenii Kuznetsov ◽  
Sergey Leonov ◽  
Dmitry Tarkhov ◽  
Alexander Vasilyev
Keyword(s):  
Neural Network ◽  
Experimental Data ◽  
Parameter Identification ◽  
Uniaxial Tension ◽  
Network Modeling ◽  
Identification Problem ◽  
Neural Network Modeling ◽  
Creep Theory ◽  
Parameter Identification Problem ◽  
Kinetic Creep

The paper deals with a parameter identification problem for creep and fracture model. The system of ordinary differential equations of kinetic creep theory is applied for describing this model. As for solving the parameter identification problem, we proposed to use the technique of neural network modeling, as well as the multilayer approach. The procedures of neural network modeling and multilayer approximation constructing application is demonstrated by the example of finding parameters for uniaxial tension model for isotropic steel 45 specimens at creep conditions. The solution corresponding to the obtained parameters agrees well with theoretical strain-damage characteristics, experimental data, and results of other authors.

Evaluation of Creep Deformation Property of Grade 91 Steels

2015 ◽  
Author(s):  
Kazuhiro Kimura ◽  
Kota Sawada ◽  
Hideaki Kushima
Keyword(s):  
Creep Rate ◽  
Creep Deformation ◽  
Minimum Creep Rate ◽  
Deformation Property ◽  
Time Dependent ◽  
Tertiary Creep ◽  
Total Strain ◽  
Dominant Factor ◽  
Creep Equation ◽  
Time To Rupture

Creep deformation property of Grade T91 steels over a range of temperatures from 550 to 625°C was analyzed by means of the empirical creep equation reported in the previous study [1]. The creep equation consists of four time dependent terms and one constant and time to rupture is estimated as a time to total strain of 10%. Accuracy of the creep equation to represent creep curve and to predict time to rupture and minimum creep rate was indicated. Times to minimum creep rate, total strain of 1%, initiation of tertiary creep and rupture were evaluated by the creep equation. Stress dependence of strains at minimum creep rate and the initiation of tertiary creep were analyzed. Contribution of four time dependent terms to the strains at minimum creep rate, total strain of 1% and initiation of tertiary creep was investigated. Three parameters to determine a temperature and time-dependent stress intensity limit, St, were compared and a dominant factor of St was examined. Heat-to-heat variation of the creep deformation property was investigated on two heats of T91 steels contain low and high nickel concentrations.

Predicting Thermal Fatigue Lifetimes for SMT Solder Joints

1992 ◽  
Vol 114 (4) ◽  
pp. 472-476 ◽  
Author(s):  
J. Sauber ◽  
J. Seyyedi
Keyword(s):  
Finite Element ◽  
Solder Joint ◽  
Thermal Cycling ◽  
Thermal Fatigue ◽  
Solder Joints ◽  
Finite Element Models ◽  
Creep Tests ◽  
Creep Equation ◽  
Joint Behavior ◽  
Creep Strains

A power-law type creep equation has been added to finite element models to calculate solder joint response to time, temperature, and stress level. The ability of the models to predict solder joint behavior was verified by running a series of creep tests. The models were then solved to determine the solder joint creep strains which occur during thermal cycling. These creep strains were used to predict the degradation of pull strength resulting from thermal cycling. More than 8,600 solder joints were thermally cycled and then individually pull tested to verify the accuracy of the method.

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