Viscoelastic stress relaxation in film/substrate systems—Kelvin model

2003 ◽  
Vol 93 (5) ◽  
pp. 2453-2457 ◽  
Author(s):  
Sun-Chien Ko ◽  
Sanboh Lee ◽  
Chun-Hway Hsueh
Keyword(s):  
Stress Relaxation ◽  
Kelvin Model ◽  
Viscoelastic Stress Relaxation ◽  
Film Substrate

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.

Predicting variations of the least principal stress with depth: Application to unconventional oil and gas reservoirs using a log-based viscoelastic stress relaxation model

Geophysics ◽  
2022 ◽  
pp. 1-56
Author(s):  
Ankush Singh ◽  
Mark D. Zoback
Keyword(s):  
Stress Relaxation ◽  
Principal Stress ◽  
Oil And Gas ◽  
Learning Technologies ◽  
Stress Profile ◽  
Gas Reservoirs ◽  
Midland Basin ◽  
Multi Stage ◽  
Viscoelastic Stress Relaxation ◽  
Geophysical Logs

Knowledge of layer-to-layer variations of the least principal stress, S hmin, with depth is essential for optimization of multi-stage hydraulic fracturing in unconventional reservoirs. Utilizing a geomechanical model based on viscoelastic stress relaxation in relatively clay rich rocks, we present a new method for predicting continuous S hmin variations with depth. The method utilizes geophysical log data and S hmin measurements from routine diagnostic fracture injection tests (DFITs) at several depths for calibration. We consider a case study in the Wolfcamp formation in the Midland Basin, where both geophysical logs and values of S hmin from DFITs are available. We compute a continuous stress profile as a function of the well logs that fits all of the DFITs well. We utilized several machine learning technologies, such as bootstrap aggregation (or bagging), to improve the generalization of the model and demonstrate that the excellent fit between predicted and observed stress values is not the result of over-fitting the calibration points. The model is then validated by accurately predicting hold-out stress measurements from four wells within the study area and, without recalibration, accurately predicting stress as a function of depth in an offset pad about 6 miles away.

Internal Stresses and Adhesion Properties of Film/Substrate Interfaces

1990 ◽  
Vol 188 ◽  
Author(s):  
M. Ignat ◽  
A. Chouaf ◽  
Ph. Normandon
Keyword(s):  
Stress Relaxation ◽  
Internal Stress ◽  
Experimental Methods ◽  
Internal Stresses ◽  
Silicon Substrates ◽  
Stress Evolution ◽  
Adhesion Properties ◽  
External Stresses ◽  
Film Substrate

ABSTRACTThe evolution of internal stresses in Tungsten films deposited on Silicon substrates submitted to external stresses is discussed here. The stresses are estimated and measured by theoretical and experimental methods. The discussion of the internal stress evolution is shown to be dependent of the film/substrate interfaces, and of the loss of adhesion inducing stress relaxation.

Studies of Viscoelastic Relaxation of Some Nitrile Rubbers under Compressive Stress

1977 ◽  
Vol 50 (5) ◽  
pp. 906-914 ◽  
Author(s):  
B. Stenberg ◽  
J. F. Jansson
Keyword(s):  
Stress Relaxation ◽  
Point Of View ◽  
Relaxation Behavior ◽  
Relaxation Processes ◽  
Theoretical Point ◽  
Stress Relaxation Behavior ◽  
Physical Mechanisms ◽  
Viscoelastic Stress Relaxation ◽  
Nitrile Rubbers ◽  
Relaxation Curves

Abstract Stress relaxation in rubbers is usually supposed to be due to chemical aging phenomena of a mainly elastic material. Considerable physical viscoelastic processes can, however, be observed in the rubbery region, depending upon the type of rubber, crosslink density, type of crosslink, filler, and so on. Thus, in chemical stress relaxation experiments chemical and physical mechanisms are superimposed and can seldom be distinguished. Stress relaxation curves registered at different temperatures contain contributions from both types of mechanism. From a practical, as well as a theoretical, point of view it is therefore essential to find methods of distinguishing between the two relaxation processes. This would be possible if the relaxation curves were obtained during periods of time so short that the chemical relaxation can be neglected. The long-term physical relaxation is then obtained by shifting the curves by, for instance, the method of reduced variables. This technique has been utilized by Curro and Salazar. We now present an alternative procedure by which the physical viscoelastic stress relaxation behavior is determined from dynamic data. The physical relaxation curves are calculated from values of E′(ω) and E″(ω) obtained at different frequencies and temperatures. In this method of determining the physical relaxation, no change of sample is needed, nor is it necessary to allow the sample to relax between measurements. The stress relaxation behavior under compression of three nitrile rubbers has been studied, and it is shown that physical mechanisms dominate just above room temperature, while chemical mechanisms dominate at higher temperatures.

Viscoelastic stress relaxation in the hamstrings before and after a 10-week stretching program

2015 ◽  
Vol 51 (5) ◽  
pp. 761-764 ◽  
Author(s):  
Gustavo H. Peixoto ◽  
Andre G. Andrade ◽  
Hans J.K. Menzel ◽  
Silvia R.S. Araújo ◽  
Antônio E.M. Pertence ◽  
...  
Keyword(s):  
Stress Relaxation ◽  
Before And After ◽  
Viscoelastic Stress Relaxation
Sign in / Sign up

Export Citation Format

Share Document