Correlation of Cooperatively Localized Rearrangement on the “Fluidized Domain" of Polymers to Their Nonexponentially Viscoelastic Behavior and Lifetime at Double Aging Processes II: Estimation of Long-term Mechanical Behavior and Lifetime of Polymeric Materials from Short-time Creep and Stress Relaxation Tests

2010 ◽  
Vol 23 (2) ◽  
pp. 185-194 ◽  
Author(s):  
Yan Jin ◽  
Ming-shi Song ◽  
Gui-xian Hu ◽  
Da-ming Wu
Keyword(s):  
Stress Relaxation ◽  
Mechanical Behavior ◽  
Viscoelastic Behavior ◽  
Polymeric Materials ◽  
Double Aging ◽  
Creep And Stress Relaxation ◽  
Short Time

Lifetime prediction of high-modulus polyethylene yarns subjected to creep using the Larson–Miller methodology

2019 ◽  
Vol 27 (7) ◽  
pp. 400-406
Author(s):  
Jefferson Morais Gautério ◽  
Leonardo Cofferri ◽  
Antonio Henrique Monteiro da Fonsec da Silva ◽  
Felipe Tempel Stumpf
Keyword(s):  
High Temperature ◽  
Mechanical Behavior ◽  
Polymeric Materials ◽  
Constant Load ◽  
Lifetime Prediction ◽  
High Modulus ◽  
Accelerated Tests ◽  
Creep Tests ◽  
Modulus Polyethylene

The aim of the present work is to apply the Larson–Miller technique for the study of the mechanical behavior under creep of high-modulus polyethylene (HMPE) fibers focused on use as in offshore mooring ropes. Creep is known to be a long-term phenomenon, so in most cases, reproducing such experiments in real time is not feasible, and as the life span of anchoring systems must be in the order of decades, accelerated tests are required to verify the long-term mechanical behavior of the material. The methodology using the Larson–Miller parameter is a well-documented and powerful technique for materials’ lifetime prediction, although seldom applied to polymeric materials. It involves in performing accelerated (high temperature and/or loads) creep tests to determine the parameters that are later used to estimate the rupture time of the material under constant load. It is concluded that the Larson–Miller technique is efficient for calculating the lifetime of HMPE subjected to creep.

Viscoelasticity Analysis and Experimental Validation of Anisotropic Composite Overwrap Cylinders

2012 ◽  
Author(s):  
Jerome T. Tzeng ◽  
Ryan P. Emerson ◽  
Daniel J. O’Brien
Keyword(s):  
Stress Relaxation ◽  
Experimental Validation ◽  
Elevated Temperatures ◽  
Model Simulation ◽  
Viscoelastic Behavior ◽  
Pressure Vessels ◽  
Steel Cylinder ◽  
Viscoelastic Effects ◽  
Creep And Stress Relaxation ◽  
Composite Cylinders

Stress relaxation and creep of composite cylinders are investigated based on anisotropic viscoelasticity. The analysis accounts for ply-by-ply variation of material properties, ply orientations, and temperature gradients through the thickness of cylinders subjected to mechanical and thermal loads. Experimental validation of the model is conducted using a high-tensioned composite overwrapped on a steel cylinder. The creep and stress relaxation response of composite is accelerated at elevated temperatures, then characterized and compared to the model simulation. Fiber reinforced composite materials generally illustrate extreme anisotropy in viscoelastic behavior. Viscoelastic effects of the composite can result in a drastic change of stress and strain profiles in the cylinders over a period of time, which is critical for structural durability of composite cylinders. The developed analysis can be applied to composite pressure vessels, gun barrels, and flywheels design of life prediction.

scholarly journals Study on the Time-Dependent Mechanical Behavior and Springback of Magnesium Alloy Sheet (AZ31B) in Warm Conditions

Materials ◽  
2021 ◽  
Vol 14 (14) ◽  
pp. 3856
Author(s):  
Jae-Hyeong YU ◽  
Chang-Whan Lee
Keyword(s):  
Magnesium Alloy ◽  
Stress Relaxation ◽  
Dynamic Recrystallization ◽  
Mechanical Behavior ◽  
Alloy Sheet ◽  
Holding Time ◽  
Time Dependent ◽  
Die Set ◽  
Creep And Stress Relaxation ◽  
Springback Angle

In this study, the time-dependent mechanical behavior of the magnesium alloy sheet (AZ31B) was investigated through the creep and stress relaxation tests with respect to the temperature and pre-strain. The microstructure changes during creep and stress relaxation were investigated. As the tensile deformation increased in the material, twinning and dynamic recrystallization occurred, especially after the plastic instability. As a result, AZ31B showed lower resistance to creep and stress relaxation due to dynamic recrystallization. Additionally, time-dependent springback characteristics in the V- and L-bending processes concerning the holding time and different forming conditions were investigated. We analyzed changes of microstructure at each forming temperature and process. The uniaxial tensile creep test was conducted to compare the microstructures in various pre-strain conditions with those at the secondary creep stage. For the bending process, the change of the microstructure after the forming was compared to that with punch holding maintained for 1000 s after forming. Due to recrystallization, with the holding time in the die set of 60 s, the springback angle decreased by nearly 70%. Increased holding time in the die set resulted in a reduced springback angle.

Indentation Creep and Relaxation Measurements of Polymers

2004 ◽  
Vol 841 ◽  
Author(s):  
Mark R. VanLandingham ◽  
Peter L. Drzal ◽  
Christopher C. White
Keyword(s):  
Stress Relaxation ◽  
Mechanical Response ◽  
Creep Compliance ◽  
Relaxation Modulus ◽  
Polymeric Materials ◽  
Indentation Creep ◽  
Dimethyl Siloxane ◽  
Linear Viscoelastic Material ◽  
Linear Viscoelastic ◽  
Creep And Stress Relaxation

ABSTRACTInstrumented indentation was used to characterize the mechanical response of polymeric materials. A model based on contact between a rigid probe and a linear viscoelastic material was used to calculate values for creep compliance and stress relaxation modulus for epoxy, poly(methyl methacrylate) (PMMA), and two poly(dimethyl siloxane) (PDMS) elastomers. Results from bulk rheometry studies were used for comparison to the indentation creep and stress relaxation results. For the two glassy polymers, the use of sharp pyramidal tips produced responses that were considerably more compliant (less stiff) than rheometry values. Additional study of the deformation remaining in epoxy after creep testing revealed that a large portion of the creep displacement measured was due to post-yield flow. Indentation creep measurements of the epoxy using a rounded conical tip also produced nonlinear responses, but the creep compliance values appeared to approach linear viscoelastic values with decreasing creep force. Responses measured for the PDMS were mainly linear elastic, but the filled PDMS exhibited some time-dependence and nonlinearity in both rheometry and indentation measurements.

scholarly journals Stress relaxation of wood-polymer composites of savewood

2019 ◽  
Vol 97 ◽  
pp. 02044
Author(s):  
Andrey Askadskii ◽  
Tatyana Matseevich ◽  
O.A. Gorbacheva
Keyword(s):  
Stress Relaxation ◽  
Mechanical Behavior ◽  
Wood Flour ◽  
Relaxation Processes ◽  
Wood Polymer ◽  
Nonlinear Mechanical ◽  
Final Stress ◽  
Long Time ◽  
Wood Polymer Composites

Experiments on stress relaxation on the samples representing fragments of terraced boards have been carried out. Matrix polymer is polyvinyl chloride (PVC). The combined wood filler, which is a mixture of wood flour and chalk, has been used. Measurements conducted at different permanent deformations of compression from 2 to 5% and temperatures from 20 to 70°C. Found that under all conditions the relative relaxation takes small values, indicating the long-term conservation of the mechanical workability of the products. Nonlinear mechanical behavior is evident already at 3% strain. At temperatures from 20 to 35°C relaxation processes take place almost identically, without reduction in initial and final stress. At temperatures of 50 and 70°C both stresses are reduced. The master curve is plotted, which allows prediction the mechanical behavior for a long time.

scholarly journals Viscoelastic Properties of the Aortic Valve Interstitial Cell

2009 ◽  
Vol 131 (4) ◽  
Author(s):  
W. David Merryman ◽  
Paul D. Bieniek ◽  
Farshid Guilak ◽  
Michael S. Sacks
Keyword(s):  
Aortic Valve ◽  
Stress Relaxation ◽  
Interstitial Cell ◽  
Viscoelastic Behavior ◽  
Time History ◽  
Micropipette Aspiration ◽  
Valve Closure ◽  
Physiological Time ◽  
Viscoelastic Effects ◽  
Creep And Stress Relaxation

There has been growing interest in the mechanobiological function of the aortic valve interstitial cell (AVIC) due to its role in valve tissue homeostasis and remodeling. In a recent study we determined the relation between diastolic loading of the aortic valve (AV) leaflet and the resulting AVIC deformation, which was found to be substantial. However, due to the rapid loading time of the AV leaflets during closure (∼0.05 s), time-dependent effects may play a role in AVIC deformation during physiological function. In the present study, we explored AVIC viscoelastic behavior using the micropipette aspiration technique. We then modeled the resulting time-length data over the 100 s test period using a standard linear solid model, which included Boltzmann superposition. To quantify the degree of creep and stress relaxation during physiological time scales, simulations of micropipette aspiration were preformed with a valve loading time of 0.05 s and a full valve closure time of 0.3 s. The 0.05 s loading simulations suggest that, during valve closure, AVICs act elastically. During diastole, simulations revealed creep (4.65%) and stress relaxation (4.39%) over the 0.3 s physiological time scale. Simulations also indicated that if Boltzmann superposition was not used in parameter estimation, as in much of the micropipette literature, creep and stress relaxation predicted values were nearly doubled (7.92% and 7.35%, respectively). We conclude that while AVIC viscoelastic effects are negligible during valve closure, they likely contribute to the deformation time-history of AVIC deformation during diastole.

Study of the Viscoelastic Behavior and Molecular Weight Distribution of Polyisobutylene

1954 ◽  
Vol 27 (2) ◽  
pp. 393-414
Author(s):  
Kensal E. Van Holde ◽  
J. W. Williams
Keyword(s):  
Molecular Weight ◽  
Experimental Investigation ◽  
Stress Relaxation ◽  
Mechanical Behavior ◽  
Weight Distribution ◽  
Viscoelastic Behavior ◽  
Elastic Behavior ◽  
High Polymer ◽  
Relaxation Experiments ◽  
Mechanical Studies

Abstract The viscoelastic behavior of linear high polymers has commanded considerable attention in recent years. The very thorough studies by Fox and Flory of the melt viscosity of polystyrene and polyisobutylene, the stress relaxation experiments of Tobolsky and coworkers, and dynamic-mechanical studies by Ferry have contributed greatly to our knowledge of the mechanical behavior of these interesting substances. However, there are many facets of this subject which have not received thorough experimental investigation. In particular, there has been no detailed study of the effect of molecular weight and polydispersity on the elastic behavior of viscoelastic materials. It was felt, therefore, that a study of the viscoelastic behavior of a series of very carefully characterized samples of a representative linear high polymer would contribute substantially to the understanding of this subject. The polymer chosen was polyisobutylene, which displays both flow and elastic behavior at room temperatures.

Creep and Stress Relaxation of Natural Rubber Vulcanizates. Part I. Effect of Crosslink Density on the Rate of Creep in Different Vulcanizing Systems

1971 ◽  
Vol 44 (3) ◽  
pp. 707-720
Author(s):  
E. D. Fairlie
Keyword(s):  
Creep Rate ◽  
Stress Relaxation ◽  
Natural Rubber ◽  
Chemical Treatment ◽  
Crosslink Density ◽  
Strong Dependence ◽  
Viscoelastic Behavior ◽  
Creep And Stress Relaxation ◽  
Natural Rubber Vulcanizates ◽  
Determining Factor

Abstract The physical creep of unfilled natural rubber vulcanizates, prepared with different vulcanizing systems, has been studied. For each of the three vulcanizing systems chosen there is a strong dependence of creep rate on crosslink density, but the rates for accelerated sulfur vulcanizates are two or three times higher than those of peroxide vulcanizates of similar crosslink density. Supplementary experiments, in which the crosslink structure of sulfur vulcanizates is modified either by chemical treatment or by variations in the vulcanizing conditions, show that the nature of the crosslink itself is not a determining factor in the type of vulcanizate. Other features, such as the type and quantity of extranetwork material arising from the vulcanizing process, contribute significantly to the viscoelastic behavior of accelerated sulfur vulcanizates.

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