scholarly journals Use of the Borehole Dilatometer Stress - Relaxation Test For Determining the Creep Properties of Ice

1991 ◽  
Author(s):  
B Ladanyi ◽  
P Huneault
Keyword(s):  
Stress Relaxation ◽  
Relaxation Test ◽  
Stress Relaxation Test ◽  
Creep Properties

Evaluation of the Creep Strength of 9Cr-1Mo-V and 1Cr-1Mo-1/4V Castings and Weldments Using Accelerated Creep Testing

2020 ◽  
Author(s):  
Scot J. Laney
Keyword(s):  
Stress Relaxation ◽  
Weld Metal ◽  
Filler Metal ◽  
Creep Testing ◽  
Relaxation Test ◽  
Stress Relaxation Test ◽  
Creep Data ◽  
Creep Properties ◽  
First Case ◽  
Accelerated Creep

Abstract Knowledge of creep properties is vital in determining the allowable stresses for rotating equipment design at high temperatures. Unfortunately, the traditional method to generate creep data requires several long term tests; in some cases, upwards of 100,000 hours are needed. These tests are often time and cost prohibitive to perform. Some data is available from sources such as the ASME Boiler and Pressure Vessel Code, but these are limited to commonly available materials in set processing conditions. They speak very little to the properties for new materials, alternate processing of existing materials, and properties for weldments and heat affected zones (HAZ) that occur in the fabrication of large equipment. Due to this, several methods have been developed for accelerated creep testing. One such method is the Stress Relaxation Test (SRT) developed by Woodford. This high precision stress relaxation test can generate five decades of creep data in a single, one-day test. This paper discusses the use of the SRT method to evaluate two different materials and their weldments used in the manufacturing of steam turbine casings. The first material is cast 9Cr-1Mo-V (SA-217, Grade C12A). In this first case, material from two different foundries was tested at temperatures between 550°C and 700°C. Specimens consisting entirely of matching weld metal and those that that include the HAZ centered between weld metal and the base casting were also tested as a means to verify fabrication and casting upgrade procedures. In this case, the data generated for all three sample types very closely match those given in literature. In a nearly identical test program, testing was performed on cast 1Cr-1Mo-¼V steel (ASTM A356, Grade 9). In this second case, the base casting closely matched literature data, while the weldments did not. In one instance, through a significant reduction in properties of the weld metal specimen, the SRT method was able to detect that an under matching filler metal was used. In another instance, the HAZ specimen, from a weldment using matching filler metal, failed during the test. It was found that the welding procedure resulted in overheating the sample. These two case studies illustrate the ability of the SRT method to accurately predict creep properties and its sensitivity to detect variations in properties, which can make it useful for rapid verification of welding procedures for high temperature applications.

Analysis on the Creep Mechanism of 12Cr-Mo-W-0.25V Steel Based on Long-Term Stress Relaxation Test Data

2016 ◽  
Vol 853 ◽  
pp. 158-162
Author(s):  
Jie Zhao ◽  
Tie Shan Cao ◽  
Cong Qian Cheng ◽  
Hui Fang Li
Keyword(s):  
Stress Relaxation ◽  
Test Data ◽  
Activation Volume ◽  
High Stress ◽  
Relaxation Curve ◽  
Relaxation Test ◽  
Dislocation Slip ◽  
Stress Relaxation Test ◽  
Steel Base

The current paper investigates on the creep behavior of 12Cr-Mo-W-0.25V heat resistant steel base on the long-term stress relaxation test data. It is shows that the stress relaxation curve can be divided into 2 stages: the high stress stage has higher apparent activation volume of 79~350 b3 and the low stress stage is 35~78 b3. Besides, the Helmholtz free energy at the high stress stage is 827~1034 kJ/mol which is higher than 210~252 kJ/mol of the low stress stage. Taking both apparent activation volume and activation energy into account, it is assumed that the high stress stage is mainly controlled by dislocation slip and the low stress stage is more related to diffusion.

Comparison of the Trueness of Fits of the Biphasic Transverse Isotropic and Kelvin Models to the Tensile Behavior of Temporomandibular Joint Disc

2021 ◽  
Vol 143 (6) ◽  
Author(s):  
Wuyang Li ◽  
Sara Trbojevic ◽  
Alejandro J. Almarza
Keyword(s):  
Experimental Data ◽  
Stress Relaxation ◽  
Temporomandibular Joint ◽  
Second Order ◽  
Relaxation Test ◽  
Stress Relaxation Test ◽  
Kelvin Model ◽  
Biphasic Model ◽  
Tmj Disc ◽  
Transverse Isotropic

Abstract This technical brief explores the validity and trueness of fit for using the transverse isotropic biphasic and Kelvin models (first and second order generalized) for characterization of the viscoelastic tensile properties of the temporomandibular joint (TMJ) discs from pigs and goats at a strain rate of 10 mm/min. We performed incremental stress-relaxation tests from 0 to 12% strain, in 4% strain steps on pig TMJ disc samples. In addition, to compare the outcomes of these models between species, we also performed a single-step stress-relaxation test of 10% strain. The transverse isotropic biphasic model yielded reliable fits in reference to the least root mean squared error method only at low strain, while the Kelvin models yielded good fits at both low and high strain, with the second order generalized Kelvin model yielding the best fit. When comparing pig to goat TMJ disc in 10% strain stress-relaxation test, unlike the other two Kelvin models, the transverse isotropic model did not fit well for this larger step. In conclusion, the second order Kelvin model showed the best fits to the experimental data of both species. The transverse isotropic biphasic model did not fit well with the experimental data, although better at low strain, suggesting that the assumption of water flow only applies while uncrimping the collagen fibers. Thus, it is likely that the permeability from the biphasic model is not truly representative, and other biphasic models, such as the poroviscoelastic model, would likely yield more meaningful outputs and should be explored in future works.

Study on Nonlinear Viscoelastic Properties of Asphalt Mixture Based on Stress Relaxation Test

2014 ◽  
Vol 563 ◽  
pp. 48-52
Author(s):  
Lei Chen ◽  
Zhi Xin Yu ◽  
Wei Ping Cui ◽  
Li Juan Qin
Keyword(s):  
Stress Relaxation ◽  
Asphalt Mixture ◽  
Viscoelastic Behavior ◽  
Exponential Model ◽  
Relaxation Test ◽  
Asphalt Binders ◽  
Stress Relaxation Test ◽  
Nonlinear Viscoelastic ◽  
Low Temperature Cracking ◽  
Relaxation Experiments

Development of normal stress in the direction perpendicular to the asphalt mixture is an important feature of the nonlinear viscoelastic behavior of asphalt binders. In this paper, this phenomenon was studied with the help of stress-relaxation experiments in torsion.  Results indicate that stress relaxation test by controlling strain could be used to evaluate the stress relaxation ability of asphalt mixture. With the aging degree of asphalt mixtures increased, the low temperature cracking resistance got worse; the higher the temperature is, the faster the stress relaxed; the smaller the initial strain, the worse the stress relaxation ability also. The viscoelasticity of asphalt mixture could be simulated by exponential model fractional and the experiments well supported the modeling results.

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