THE EFFECT OF DISPLACEMENT RATE ON VISCOELASTIC PROPERTIES OF RAT CERVIX

2016 ◽  
Vol 28 (03) ◽  
pp. 1650018 ◽  
Author(s):  
Alireza Ashofteh Yazdi ◽  
Ali Esteki ◽  
Mohammad Mehdi Dehghan ◽  
Farhad Tabatabai Ghomsheh
Keyword(s):  
Viscoelastic Properties ◽  
Viscoelastic Model ◽  
Elastic Response ◽  
Displacement Rate ◽  
Sufficient Information ◽  
Cervical Insufficiency ◽  
Load Relaxation ◽  
Pregnant Rats ◽  
Tension Tests ◽  
Relaxation Curves

Determining the viscoelastic response of cervix at different displacement rates can provide sufficient information for the normal mechanical behavior of the tissue in assessment of cervical insufficiency. The objective of this study was to investigate the effect of displacement rate on viscoelastic properties of rat cervix. Different displacement rates were employed to measure the tensile and load-relaxation properties of cervices from virgin and 16 days post-conception pregnant rats. After preconditioning, the displacement of 2[Formula: see text]mm was applied to the distal halves of five pregnant rat’s cervices and 1 millimeter to the five virgin samples circumferentially. Uniaxial tension tests were employed at the displacement rates of 0.01, 0.1 and 1 mm/s randomly and were held for 10 min while the tissues were relaxed. Tensile and load-relaxation curves were well described by a quasi-linear viscoelastic model. Statistical analysis revealed significant correlation between the change in displacement rate and the elastic response, as well as the viscous response of the virgin samples. For pregnant samples, though, the correlation was found significant between the displacement rate and the elastic response of the tissue. Virgin tissue is strongly viscoelastic. Quantitative measurements of cervical mechanical properties will lead to a more accurate assessment of cervical insufficiency and prediction of preterm birth.

Determination of an average quasi-linear viscoelastic model for the mechanical behavior of rat cervix

2017 ◽  
Vol 233 (5) ◽  
pp. 924-929
Author(s):  
Alireza Ashofteh Yazdi ◽  
Ali Esteki ◽  
Mohammad Mehdi Dehghan
Keyword(s):  
Mechanical Behavior ◽  
Viscoelastic Model ◽  
Precise Description ◽  
Average Model ◽  
Tension Tests ◽  
Linear Viscoelastic ◽  
Model Equations ◽  
Relaxation Curves ◽  
Linear Viscoelastic Model

The objective of this study was to determine an average quasi-linear viscoelastic model for the mechanical behavior of rat cervix. The average model is applicable at defined displacement rates for virgin and pregnant tissues in the last trimester of pregnancy. After preconditioning, the displacement of 2 mm was applied to the distal halves of five pregnant rat’s cervices and 1 mm to the five virgin samples circumferentially. Uniaxial tension tests were employed at the displacement rates of 0.01, 0.1 and 1 mm/s randomly and were held for 10 min while the tissues were relaxed. Tensile and load-relaxation curves were well described by a quasi-linear viscoelastic model. Two average quasi-linear viscoelastic models were fitted to all 30 curves obtained from experiments for virgin and pregnant tissues. The average quasi-linear viscoelastic model coefficients were extracted using the average model equations. Cervical tissue is strongly viscoelastic. Determination of an average viscoelastic model of rat cervix may lead to a more precise description of the mechanical behavior of the virgin and pregnant tissues in the assessment of cervical insufficiency.

scholarly journals Viscoelastic Properties of Cell Structures Manufactured Using a Photo-Curable Additive Technology—PJM

Polymers ◽  
2021 ◽  
Vol 13 (11) ◽  
pp. 1895
Author(s):  
Tomasz Kozior ◽  
Czesław Kundera
Keyword(s):  
Viscoelastic Properties ◽  
Cellular Structure ◽  
Material Selection ◽  
Cellular Structures ◽  
Test Results ◽  
Additive Technology ◽  
Polymer Resin ◽  
Cell Structures ◽  
Relaxation Curves ◽  
The Impact

This research paper reviews the test results involving viscoelastic properties of cellular structure models made with the PolyJet Matrix—PJM additive technology. The designed test specimens were of complex cellular structure and made of three various photo-curable polymer resin types. Materials were selected taking into account the so-called “soft” and “tough” material groups. Compressive stress relaxation tests were conducted in accordance with the recommendations of standard ISO 3384, and the impact of the geometric structure shape and material selection on viscoelastic properties, as well as the most favorable geometric variants of the tested cellular structure models were determined. Mathematica and Origin software was used to conduct a statistical analysis of the test results and determine five-parameter functions approximating relaxation curves. The most favorable rheological was adopted and its mean parameters determined, which enables to match both printed model materials and their geometry in the future, to make a component with a specific rheological response. Furthermore, the test results indicated that there was a possibility of modelling cellular structures within the PJM technology, using support material as well.

Viscoelastic properties of doxorubicin-treated HT-29 cancer cells by atomic force microscopy: the fractional Zener model as an optimal viscoelastic model for cells

2019 ◽  
Vol 19 (3) ◽  
pp. 801-813 ◽  
Author(s):  
Maricela Rodríguez-Nieto ◽  
Priscila Mendoza-Flores ◽  
David García-Ortiz ◽  
Luis M. Montes-de-Oca ◽  
Marco Mendoza-Villa ◽  
...  
Keyword(s):  
Atomic Force Microscopy ◽  
Cancer Cells ◽  
Viscoelastic Properties ◽  
Viscoelastic Model ◽  
Zener Model ◽  
Force Microscopy ◽  
Atomic Force ◽  
Fractional Zener Model ◽  
Ht 29

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–Viscoplastic Cyclic Deformation of Polycarbonate Polymer: Experiment and Constitutive Model

2016 ◽  
Vol 83 (4) ◽  
Author(s):  
Chao Yu ◽  
Guozheng Kang ◽  
Fucong Lu ◽  
Yilin Zhu ◽  
Kaijuan Chen
Keyword(s):  
Constitutive Model ◽  
Kinematic Hardening ◽  
Viscoelastic Model ◽  
Creep Recovery ◽  
Strong Nonlinearity ◽  
Viscoplastic Strain ◽  
Cyclic Tension ◽  
Nonlinear Viscoelastic ◽  
Tension Tests ◽  
Proposed Model

A series of uniaxial tests (including multilevel loading–unloading recovery, creep-recovery, and cyclic tension–compression/tension ones) were performed to investigate the monotonic and cyclic viscoelastic–viscoplastic deformations of polycarbonate (PC) polymer at room temperature. The results show that the PC exhibits strong nonlinearity and rate-dependence, and obvious ratchetting occurs during the stress-controlled cyclic tension–compression/tension tests with nonzero mean stress, which comes from both the viscoelasticity and viscoplasticity of the PC. Based on the experimental observation, a nonlinear viscoelastic–viscoplastic cyclic constitutive model is then constructed. The viscoelastic part of the proposed model is constructed by extending the Schapery's nonlinear viscoelastic model, and the viscoplastic one is established by adopting the Ohno–Abdel-Karim's nonlinear kinematic hardening rule to describe the accumulation of irrecoverable viscoplastic strain produced during cyclic loading. Furthermore, the dependence of elastic compliance of the PC on the accumulated viscoplastic strain is considered. Finally, the capability of the proposed model is verified by comparing the predicted results with the corresponding experimental ones of the PC. It is shown that the proposed model provides reasonable predictions to the various deformation characteristics of the PC presented in the multilevel loading–unloading recovery, creep-recovery, and cyclic tension–compression/tension tests.

The Time and History-Dependent Viscoelastic Properties of the Canine Medial Collateral Ligament

1981 ◽  
Vol 103 (4) ◽  
pp. 293-298 ◽  
Author(s):  
S. L.-Y. Woo ◽  
M. A. Gomez ◽  
W. H. Akeson
Keyword(s):  
Medial Collateral Ligament ◽  
Viscoelastic Properties ◽  
Cyclic Stress ◽  
Elastic Response ◽  
Collateral Ligament ◽  
Stress Strain ◽  
Linear Viscoelastic ◽  
Viscoelastic Theory ◽  
Linear Viscoelastic Theory

The viscoelastic properties of the canine medial collateral ligament (MCL) were investigated. Stress-strain relationships at different strain rates, long-term stress relaxation and cyclic stress-strain curves of the MCL were obtained experimentally using a bone-MCL-bone preparation. The experimental data were used in conjunction with the quasi-linear viscoelastic theory as proposed by Fung [15] to characterize the reduced relaxation function, G(t) and elastic response σe (ε) of this tissue. It was found that the quasi-linear viscoelastic theory can adequately describe the time and history-dependent rheological properties of the canine medial collateral ligament.

Dynamic Lumped Element Response of the Human Fingerpad

1999 ◽  
Vol 121 (2) ◽  
pp. 178-183 ◽  
Author(s):  
D. T. V. Pawluk ◽  
R. D. Howe
Keyword(s):  
Experimental Data ◽  
Constant Velocity ◽  
Relaxation Function ◽  
Viscoelastic Model ◽  
Compressive Load ◽  
Elastic Response ◽  
Sensory Response ◽  
Time Constants ◽  
Lumped Element

The dynamic response of the fingerpad plays an important role in the tactile sensory response and precision manipulation, as well as in ergonomic design. This paper investigates the dynamic lumped element response of the human fingerpad in vivo to a compressive load. A flat probe indented the fingerpad at a constant velocity, then held a constant position. The resulting force (0–2 N) increased rapidly with indentation, then relaxed during the hold phase. A quasilinear viscoelastic model successfully explained the experimental data. The instantaneous elastic response increased exponentially with position, and the reduced relaxation function included three decaying exponentials (with time constants of approximately 4 ms, 70 ms, and 1.4 s) plus a constant. The model was confirmed with data from sinusoidal displacement trajectories.

scholarly journals Modelling sea-level fingerprints of glaciated regions with low mantle viscosity

2021 ◽  
Vol 12 (3) ◽  
pp. 783-795
Author(s):  
Alan Bartholet ◽  
Glenn A. Milne ◽  
Konstantin Latychev
Keyword(s):  
Sea Level ◽  
21St Century ◽  
Viscoelastic Model ◽  
Elastic Response ◽  
Earth Model ◽  
Sea Level Changes ◽  
Relative Sea Level ◽  
Global Average ◽  
Low Viscosity ◽  
Mantle Viscosity

Abstract. Global patterns of sea-level change – often termed “sea-level fingerprints” – associated with future changes in ice/water mass re-distribution are a key component in generating regional sea-level projections. Calculation of these fingerprints is commonly based on the assumption that the isostatic response of the Earth is dominantly elastic on century timescales. While this assumption is accurate for regions underlain by mantle material with viscosity close to that of global average estimates, recent work focusing on the West Antarctic region has shown that this assumption can lead to significant error where the viscosity is significantly lower than typical global average values. Here, we test this assumption for fingerprints associated with glaciers and ice caps. We compare output from a (1D) elastic Earth model to that of a 3D viscoelastic model that includes low-viscosity mantle in three glaciated regions: Alaska, southwestern Canada, and the southern Andes (Randolph Glacier Inventory (RGI) regions 1, 2, and 17, respectively). This comparison indicates that the error incurred by ignoring the non-elastic response is of the order of 1 mm in most areas (or about 1 % of the barystatic signal) over the 21st century with values reaching the centimetre level in glaciated regions. However, in glaciated regions underlain by low-viscosity mantle, the non-elastic deformation can result in relative sea-level changes with magnitudes of up to several tens of centimetres (or several times the barystatic value). The magnitude and spatial pattern of this non-elastic signal is sensitive to variations in both the projected ice history and regional viscosity structure, indicating the need for loading models with high spatial resolution and improved constraints on regional Earth viscosity structure to accurately simulate sea-level fingerprints in these regions. The anomalously low mantle viscosity in these regions also amplifies the glacial isostatic adjustment signal associated with glacier changes during the 20th century, causing it to be an important (and even dominant) contributor to the modelled relative sea-level changes over the 21st century.

scholarly journals Effect of Degradation and Osteoarthritis on the Viscoelastic Properties of Human Knee Articular Cartilage: An Experimental Study and Constitutive Modeling

Biomechanics ◽  
2021 ◽  
Vol 1 (2) ◽  
pp. 225-238
Author(s):  
Hesam Khajehsaeid ◽  
Zanko Abdollahpour ◽  
Hedyeh Farahmandpour
Keyword(s):  
Articular Cartilage ◽  
Mechanical Behavior ◽  
Energy Absorption ◽  
Tissue Damage ◽  
Viscoelastic Properties ◽  
Viscoelastic Model ◽  
Absorption Capacity ◽  
Model Parameters ◽  
Human Knee ◽  
Nonlinear Viscoelastic Model

Articular cartilage, as a hydrated soft tissue which covers diarthrodial joints, has a pivotal role in the musculoskeletal system. Osteoarthritis is the most common degenerative disease that affects most individuals over the age of 55. This disease affects the elasticity, lubrication mechanism, damping function, and energy absorption capability of articular cartilage. In order to investigate the effect of osteoarthritis on the performance of articular cartilage, the mechanical behavior of human knee articular cartilage was experimentally investigated. Progressive cyclic deformation was applied beyond the physiological range to facilitate degradation of the tissue. The relaxation response of the damaged tissue was modeled by means of a fractional-order nonlinear viscoelastic model in the framework of finite deformations. It is shown that the proposed fractional model well reproduces the tissue’s mechanical behavior using a low number of parameters. Alteration of the model parameters was also investigated throughout the progression of tissue damage. This helps predict the mechanical behavior of the osteoarthritic tissue based on the level of previous damage. It is concluded that, with progression of osteoarthritis, the articular cartilage loses its viscoelastic properties such as damping and energy absorption capacity. This is also accompanied by a loss of stiffness which deteriorates more rapidly than viscosity does throughout the evolution of tissue damage. These results are thought to be significant in better understanding the degradation of articular cartilage and the progression of OA, as well as in the design of artificial articular cartilages.

scholarly journals Numerical Modeling of pipes conveying gas-liquid two-phase flow

2019 ◽  
Vol 97 ◽  
pp. 05022 ◽  
Author(s):  
Bakhtiyar Khudayarov ◽  
Kholidakhon Komilova ◽  
Fozilzhon Turaev
Keyword(s):  
Slug Flow ◽  
Viscoelastic Properties ◽  
Gas Flow ◽  
Viscoelastic Model ◽  
Longitudinal Direction ◽  
Two Phase ◽  
Liquid Phases ◽  
Tensile Forces ◽  
Hereditary Theory ◽  
Bubble Zone

Results of studies of the oscillations of pipelines conveying a two-phase slug flow are presented in the paper. A viscoelastic model of the theory of beams and the Winkler base model are used in the study of pipeline oscillations with a gas-containing slug flowing inside. The Boltzmann-Volterra hereditary theory of the viscoelasticity is used to describe the viscoelastic properties of the pipeline material and earth bases. The effect of gas and liquid phases flow rates, influence of tensile forces in the longitudinal direction of the pipeline, parameters of Winkler bases, parameters of singularity in the heredity kernels and geometric parameters of the pipeline on the oscillations of structures with viscoelastic properties are numerically studied. It is revealed that an increase in the length of the gas bubble zone leads to a decrease in the amplitude and oscillation frequency of the pipeline. The critical rates for a two-phase slug flow are determined. It is revealed that an increase in the soil density of the bases leads to an increase in the critical rate of gas flow. It is shown that an account of viscoelastic properties of structure material and earth bases leads to a decrease in the critical flow rate.

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