Stress Relaxation Studies of the Viscoelastic Properties of Polymers

1956 ◽  
Vol 27 (7) ◽  
pp. 673-685 ◽  
Author(s):  
Arthur V. Tobolsky
Keyword(s):  
Stress Relaxation ◽  
Viscoelastic Properties ◽  
Relaxation Studies

Stress Relaxation Studies of the Viscoelastic Properties of Polymers

1957 ◽  
Vol 30 (2) ◽  
pp. 427-448
Author(s):  
Arthur V. Tobolsky
Keyword(s):  
Stress Relaxation ◽  
Simple Form ◽  
Mathematical Description ◽  
Viscoelastic Properties ◽  
Amorphous Polymers ◽  
Chemical Stress ◽  
Natural Polymers ◽  
Crystalline Polymers ◽  
Relaxation Stress ◽  
Relaxation Studies

Abstract Extensive studies of the viscoelastic properties of polymers undertaken in the author's laboratory by means of the method of stress relaxation are here reviewed. The discussion is divided into four parts: chemical stress relaxation, stress relaxation in amorphous polymers, stress relaxation in crystalline polymers, and stress relaxation in certain natural polymers and polyelectrolytes. Mathematical description of the phenomena are presented in simple form. The relation between structure and viscoelastic properties of polymers are discussed and a rather complete over-all picture of these phenomena seems to be emerging.

Mechanical properties of the tadpole tail fin

1998 ◽  
Vol 201 (19) ◽  
pp. 2691-2699 ◽  
Author(s):  
PA Doherty ◽  
RJ Wassersug ◽  
JM Lee
Keyword(s):  
Stress Relaxation ◽  
Large Deformation ◽  
Forced Vibration ◽  
Viscoelastic Properties ◽  
Developmental Plasticity ◽  
Rana Catesbeiana ◽  
Small Deformation ◽  
Collagen Fibres ◽  
Tadpole Tail ◽  
Undulatory Swimming

The tadpole tail fin is a simple double layer of skin overlying loose connective tissue. Collagen fibres in the fin are oriented at approximately +/-45 degrees from the long axis of the tail. Three tests were conducted on samples of the dorsal tail fin from 6-10 Rana catesbeiana tadpoles to establish the fin's viscoelastic properties under (1) large-deformation cyclic loading at 1 and 3 Hz, (2) small-deformation forced vibration at 1 and 3 Hz, and (3) stress relaxation under a 0.1 s loading time. The fin was very fragile, failing easily under tensile loads less than 7 g. It was also strikingly viscoelastic, as demonstrated by 72+/-1 % hysteresis loss (at 3 Hz), 16+/-3 % stress remaining after 100 s of stress relaxation and a phase angle of 18+/-1 degrees in forced vibration. As a consequence of its viscoelastic properties, the fin was three times stiffer in small than in large deformation. This may account for the ability of the fin to stay upright during normal undulatory swimming, despite the absence of any skeletal support. Tadpoles in nature are often found with damaged tails. We suggest that the unusually viscoelastic and fragile nature of the fin helps tadpoles escape the grasp of predators. Because the fin deforms viscoelastically and tears easily, tadpoles can escape predators and survive otherwise lethal attacks with only minor lacerations to the fin. Recent studies have shown that certain tadpoles develop taller fins in the presence of predators. This developmental plasticity is consistent with the tail fin acting as a protective but expendable 'wrap' around the core muscle tissue.

scholarly journals Influence of Network Topology on the Viscoelastic Properties of Dynamically Crosslinked Hydrogels

2020 ◽  
Author(s):  
Emilia M. Grad ◽  
Isabell Tunn ◽  
Dion Voerman ◽  
Alberto S. de Léon ◽  
Roel Hammink ◽  
...  
Keyword(s):  
Relaxation Time ◽  
Stress Relaxation ◽  
Network Topology ◽  
Viscoelastic Properties ◽  
Polymeric Materials ◽  
Direct Result ◽  
Reference Network ◽  
Self Healing ◽  
Combine Stress ◽  
Synthetic Cell

Biological materials combine stress relaxation and self-healing with non-linear stress-strain responses. These characteristic features are a direct result of hierarchical self-assembly, which often results in fiber-like architectures. Even though structural knowledge is rapidly increasing, it has remained a challenge to establish relationships between microscopic and macroscopic structure and function. Here, we focus on understanding how network topology determines the viscoelastic properties, i.e. stress relaxation, of biomimetic hydrogels. We have dynamically crosslinked two different synthetic polymers with one and the same crosslink. The first polymer, a polyisocyanopeptide (PIC), self-assembles into semi-flexible, fiber-like bundles and thus displays stress-stiffening, similar to many biopolymer networks. The second polymer, 4-arm poly(ethylene glycol) (starPEG), serves as a reference network with well-characterized structural and viscoelastic properties. Using one and the same coiled coil crosslink allows us to decouple the effects of crosslink kinetics and network topology on the stress relaxation behavior of the resulting hydrogel networks. We show that the fiber-containing PIC network displays a relaxation time approximately two orders of magnitude slower than the starPEG network. This reveals that crosslink kinetics is not the only determinant for stress relaxation. Instead, we propose that the different network topologies determine the ability of elastically active network chains to relax stress. In the starPEG network, each elastically active chain contains exactly one crosslink. In the absence of entanglements, crosslink dissociation thus relaxes the entire chain. In contrast, each polymer is crosslinked to the fiber bundle in multiple positions in the PIC hydrogel. The dissociation of a single crosslink is thus not sufficient for chain relaxation. This suggests that tuning the number of crosslinks per elastically active chain in combination with crosslink kinetics is a powerful design principle for tuning stress relaxation in polymeric materials. The presence of a higher number of crosslinks per elastically active chain thus yields materials with a slow macroscopic relaxation time but fast dynamics at the microscopic level. Using this principle for the design of synthetic cell culture matrices will yield materials with excellent long-term stability combined with the ability to locally reorganize, thus facilitating cell motility, spreading and growth.

scholarly journals Viscoelastic Properties of the Hindfoot Bones

2018 ◽  
Vol 3 (3) ◽  
pp. 2473011418S0045
Author(s):  
Michelle Son ◽  
Brent Munroe
Keyword(s):  
Stress Relaxation ◽  
Exponential Decay ◽  
Viscoelastic Properties ◽  
Peak Load ◽  
Distal Tibia ◽  
Bony Union ◽  
Load Relaxation ◽  
Trabecular Thickness ◽  
Trabecular Separation ◽  
Trabecular Number

Category: Hindfoot Introduction/Purpose: Obtaining and maintaining compression at an arthrodesis site is a key factor in achieving successful bony union. Bones, like other collagen containing tissues, are known to exhibit viscoelastic properties that may lead to stress relaxation at the arthrodesis site. The viscoelastic properties of the hindfoot bones when subjected to compression (as occurs during fusion surgery) are not known. The objective of this study was to quantify the viscoelastic properties of hindfoot bones under compression by measuring the time course of stress relaxation. Methods: 19 cadaveric human bone cubes 10 mm on each side consisting of trabecular and subchondral bone were cut from the hindfoot bones including the talus, calcaneus, and distal tibia. Each cube was scanned with micro computed tomography (µCT) to quantify bone volume/total volume ratio (BV/TV), trabecular thickness, trabecular separation, trabecular number, and connectivity density. Each specimen was then immersed in a saline bath and compressed 1 mm at a strain rate of 1 mm/s using an MTS machine (Fig 1). This compressed position was then held for 3 hours while the load was recorded. Following the compression test, each specimen was re-scanned with µCT. Results: Two distinct patterns of load relaxation were found. The first consisted of a uniform exponential decay. The second had a similar exponential decay but included a plateau occurring between 1-6 minutes. This second pattern was reflected in the average fractional load relaxation graph (Fig 2). The average peak load was 24.14 kg (SD ± 15.07 kg) and average end relaxation was 2.93 kg (SD ± 3.81 kg). The average time to achieve 95% decay in total load was 34.7 min (SD ± 29.1 min) although removing some outliers, it decreased to 24.9 min (SD ± 18.4 min) which is more representative of the overall data. Averages of BV/TV, trabecular thickness, and trabecular separation increased after stress relaxation while average connectivity density and trabecular number decreased. Conclusion: These data suggest that, due to the viscoelastic properties of bone, approximately 95% of an applied compressive load generated by a fixed displacement is lost within the first 30 minutes. Applied clinically, these findings may have a significant impact on the optimal surgical technique used for osteosynthesis and arthrodesis. Specifically, these data call into question whether the compression applied during surgery can be maintained throughout the healing phase without the application of continuous compression via an external fixator or internal continuous compression device. At minimum, these data suggest that lag or compression screws should be retightened prior to wound closure.

Viscoelastic properties of the central region of porcine temporomandibular joint disc in shear stress-relaxation

2019 ◽  
Vol 93 ◽  
pp. 126-131
Author(s):  
Eva Barrientos ◽  
Fernandez Pelayo ◽  
Eiji Tanaka ◽  
María Jesús Lamela-Rey ◽  
Alfonso Fernández-Canteli
Keyword(s):  
Shear Stress ◽  
Stress Relaxation ◽  
Temporomandibular Joint ◽  
Central Region ◽  
Viscoelastic Properties ◽  
Temporomandibular Joint Disc ◽  
Shear Stress Relaxation

scholarly journals Stress Relaxation Studies of CBA and SSC Coil Sections

1985 ◽  
Vol 32 (5) ◽  
pp. 3672-3674
Author(s):  
M. Anerella ◽  
A. Hoffman ◽  
R. Jackimowicz ◽  
W. Lenz ◽  
J. Skaritka ◽  
...  
Keyword(s):  
Stress Relaxation ◽  
Relaxation Studies

Transverse Nuclear Spin Relaxation Studies of Viscoelastic Properties of Membrane Vesicles. II. Experimental Results

2002 ◽  
Vol 106 (21) ◽  
pp. 5517-5526 ◽  
Author(s):  
Gerhard Althoff ◽  
Oliver Stauch ◽  
Marija Vilfan ◽  
Diego Frezzato ◽  
Giorgio J. Moro ◽  
...  
Keyword(s):  
Spin Relaxation ◽  
Nuclear Spin ◽  
Viscoelastic Properties ◽  
Membrane Vesicles ◽  
Experimental Results ◽  
Nuclear Spin Relaxation ◽  
Relaxation Studies

scholarly journals Identifying Regional Viscoelastic Properties of the Superficial Muscular Aponeurotic System

2020 ◽  
Author(s):  
Robert Lukavsky ◽  
Andrew Trussler ◽  
Fritz E Barton ◽  
Michael Lee
Keyword(s):  
Stress Relaxation ◽  
Parotid Gland ◽  
Viscoelastic Properties ◽  
Masseter Muscle ◽  
Nasolabial Fold ◽  
Bursting Strength ◽  
Lateral Canthus

Abstract Background Suspension of the superficial muscular aponeurotic system (SMAS) is generally believed to be necessary in facelift surgery. Although many techniques have been suggested, all rely on the viscoelastic properties of the SMAS Objectives The aim of this study was to determine the viscoelastic properties of bursting strength, stress relaxation, and creep in the lateral, mid-cheek, and medial regions of the SMAS. Methods The viscoelastic properties of the SMAS were determined in 12 cadaveric hemifaces. Lateral SMAS was classified as the SMAS overlying the parotid gland; mid-cheek SMAS as anterior to the parotid and overlying the masseter muscle; and medial SMAS as including tissue extending medial from the lateral canthus and ending at the nasolabial fold. Results The 3 SMAS regions showed significantly different bursting strengths: 38.9 N for the lateral SMAS, 26.7 N for the mid-cheek SMAS, and 11.9 N for the medial SMAS (P < 0.0001). Stress relaxation was similar in all vertical regions with measurements of 54% in the lateral, 48% in the mid-cheek, and 59% in the medial SMAS. Creep was found to be similar in the lateral and mid-cheek SMAS with values of 18% and 19%, respectively. The medial SMAS was noted to have a higher creep at 22%. Conclusions The lateral SMAS has a stronger bursting strength than the mid-cheek and medial SMAS. Creep appears to be lower in the lateral and mid-cheek SMAS. Stress relaxation appears to be similar in all 3 vertical regions.

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