Linear Viscoelastic Response of Dendronized Polymers

2012 ◽  
Vol 45 (21) ◽  
pp. 8813-8823 ◽  
Author(s):  
R. Pasquino ◽  
B. Zhang ◽  
R. Sigel ◽  
H. Yu ◽  
M. Ottiger ◽  
...  
Keyword(s):  
Viscoelastic Response ◽  
Dendronized Polymers ◽  
Linear Viscoelastic

Dynamic mechanical analysis of dry wood: Linear viscoelastic response region and effects of minor moisture changes

Holzforschung ◽  
2007 ◽  
Vol 61 (1) ◽  
pp. 28-33 ◽  
Author(s):  
Nanjian Sun ◽  
Sudipto Das ◽  
Charles E. Frazier
Keyword(s):  
Dynamic Mechanical Analysis ◽  
Mechanical Analysis ◽  
Viscoelastic Response ◽  
Southern Pine ◽  
Yellow Poplar ◽  
Dynamic Mechanical ◽  
Linear Viscoelastic ◽  
Dry Wood ◽  
Wood Analysis ◽  
Response Region

Abstract The dynamic mechanical analysis (DMA) of wood with moisture content (MC) below 1% has not yet been described. Aiming at this low MC range, the linear viscoelastic response region (LVR) of thoroughly dried wood was studied in single-cantilever bending. The LVR limit was determined as a function of grain orientation and temperature using yellow-poplar (Liriodendron tulipifera) and southern yellow pine (Pinus spp.). The LVR limit for dry wood ranged from approximately 0.03% to 0.16% strain. The LVR limit was greater for bending perpendicular to the grain than for parallel to the grain, suggesting that DMA signal quality would be better in the former case. Southern pine generally exhibited a greater LVR limit than yellow-poplar. The LVR anisotropy was greater in yellow-poplar than in southern pine. These findings suggest that detailed LVR analysis might be useful for wood analysis, or at least that regular LVR analysis is required for reliable wood DMA. The effects of wood moisture changes (between 0% and 1%) were observed in low-temperature secondary relaxations, consistent with the previous findings of others. Yellow-poplar specimens exhibited a significant storage modulus increase over a 250°C temperature range when specimen moisture increased from 0% to ∼0.7%.

scholarly journals Stress relaxation of porcine tendon under simulated biological environment: experiment and modeling

2021 ◽  
Vol 23 (1) ◽  
Author(s):  
Sylwia D. Łagan ◽  
Aneta Liber-Kneć
Keyword(s):  
Stress Relaxation ◽  
Viscoelastic Model ◽  
Model Fitting ◽  
Viscoelastic Behavior ◽  
Strain Range ◽  
Viscoelastic Response ◽  
Physiological Strain ◽  
Linear Viscoelastic ◽  
Biological Environment ◽  
Environment Experiment

Purpose: The aim of the study was to investigate the viscoelastic response in the low and high physiological strain with the use of experimental and modeling approach. Methods: Viscoelastic response in the low, transition and high physiologic strain (3, 6 and 9%) with consideration of simulated biological environment (0.9% saline solution, 37 °C) was measured in relaxation tests. Preconditioning of tendons was considered in the testing protocol and the applied range of load was obtained from tensile testing. The quasi-linear viscoelasticity theory was used to fit experimental data to obtain constants (moduli and times of relaxation), which can be used for description of the viscoelastic behavior of tendons. The exponential non-linear elastic representation of the stress response in ramp strain was also estimated. Results: Differences between stress relaxation process can be seen between tendons stretched to the physiological strain range (3%) and exceeding this range (6 and 9%). The strains of 6% and 9% showed a similar stress relaxation trend displaying relatively rapid relaxation for the first 70 seconds, whereas the lowest strain of 3% displayed relatively slow relaxation. Conclusions: Results of the model fitting showed that the quasi-linear viscoelastic model gives the best fit in the range of low physiological strain level.

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