scholarly journals Characterizing the Material Properties of the Kidney and Liver in Unconfined Compression and Probing Protocols with Special Reference to Varying Strain Rate

Biomechanics ◽  
2021 ◽  
Vol 1 (2) ◽  
pp. 264-280
Author(s):  
Blake Johnson ◽  
Scott Campbell ◽  
Naira Campbell-Kyureghyan
Keyword(s):  
Elastic Modulus ◽  
Strain Rate ◽  
Material Properties ◽  
Kidney Tissue ◽  
Failure Stress ◽  
Rate Dependency ◽  
Unconfined Compression ◽  
Porcine Tissue ◽  
Liver And Kidney ◽  
Strain Rate Dependency

The liver and kidneys are the most commonly injured organs due to traumatic impact forces applied to the abdomen and pose a challenge to physicians due to a hard-to-diagnose risk of internal bleeding. A better understanding of the mechanism of injury will improve diagnosis, treatment, forensics, and other fields. Finite element modelling is a tool that can aid in this understanding, but accurate material properties are required including the strain rate dependency and the feasibility of using animal tissue properties instead of human. The elastic modulus in a probing protocol and the elastic modulus, failure stress, and failure strain in a compression protocol were found for both liver and kidney tissue from human and porcine specimens at varying strain rates. Increases in the elastic modulus were seen for both the human kidney and liver, but only for the porcine kidney, when comparing the unconfined compression and probing protocols. A strain rate dependency was found for both the liver and kidney properties and was observed to have a larger saturation effect at higher rates for the failure stress than for the elastic modulus. Overall, the material properties of intact liver and kidney were characterized, and the strain rate dependency was numerically modelled. The study findings suggest that some kidney and liver material properties vary from human to porcine tissue. Therefore, it is not always appropriate to use material properties of porcine tissue in computational or physical models of the human liver and kidney.

scholarly journals Modeling of the Strain Rate Dependency of Polycarbonate’s Yield Stress: Evaluation of Four Constitutive Equations

2016 ◽  
Vol 2016 ◽  
pp. 1-9 ◽  
Author(s):  
Abdullah A. Al-Juaid ◽  
Ramzi Othman
Keyword(s):  
Experimental Data ◽  
Strain Rate ◽  
Yield Stress ◽  
Power Law ◽  
Constitutive Relations ◽  
Stress Sensitivity ◽  
Strain Rate Range ◽  
Rate Dependency ◽  
Rate Range ◽  
Strain Rate Dependency

The main focus of this paper is in evaluating four constitutive relations which model the strain rate dependency of polymers yield stress. Namely, the two-term power-law, the Ree-Eyring, the cooperative, and the newly modified-Eyring equations are used to fit tensile and compression yield stresses of polycarbonate, which are obtained from the literature. The four equations give good agreement with the experimental data. Despite using only three material constants, the modified-Eyring equation, which considers a strain rate-dependent activation volume, gives slightly worse fit than the three other equations. The two-term power-law and the cooperative equation predict a progressive increase in the strain rate sensitivity of the yield stress. Oppositely, the Ree-Eyring and the modified-Eyring equations show a clear transition between the low and high strain rate ranges. Namely, they predict a linear dependency of the yield stress in terms of the strain rate at the low strain rate range. Crossing a threshold strain rate, the yield stress sensitivity sharply increases as the strain rate increases. Hence, two different behaviors were observed though the four equations fit well the experimental data. More experimental data, mainly at the intermediate strain rate range, are needed to conclude which, of the two behaviors, is more appropriate for polymers.

scholarly journals Time-dependent behaviour of sand with different fine contents under oedometric loading

2019 ◽  
Vol 56 (1) ◽  
pp. 102-115 ◽  
Author(s):  
Friedrich Levin ◽  
Stefan Vogt ◽  
Roberto Cudmani
Keyword(s):  
Strain Rate ◽  
Creep Behaviour ◽  
Silty Sand ◽  
Granular Soils ◽  
Rate Dependency ◽  
Viscous Effects ◽  
Fine Content ◽  
Constant Rate ◽  
Rate Controlled ◽  
Strain Rate Dependency

To characterize the effects of creep, strain rate, and relaxation in granular soils, different sands have been studied under oedometric loading. The tests were analysed in the framework of the isotache concept. The results show increasing creep rates with increasing vertical stresses and a strong reduction of the creep rate upon unloading. A lower void ratio leads to less creep. Evaluation of the ratio Cα/Cc, where Cα is the creep coefficient and Cc is the compression index, demonstrates considerable deviation from a constant soil-specific value for the sands. With increasing fine content, however, a constant soil-specific ratio has been found for a silty sand. In strain rate–controlled tests, a sand with low and a sand with significant content of nonplastic fines were compared. Constant rate of strain tests displayed practically no strain rate dependency for the sand with little fines and a well visible strain rate dependency for the very silty sand. Tests with stepwise change of strain rate showed non-isotache behaviour for the sand with little fines and isotache behaviour for the other. Stress-relaxation tests displayed an isochronous behaviour. The analysis of the three viscous effects in sands showed they cannot altogether be mathematically described in the framework of the isotache concept. A new compression model for the creep behaviour of sands is presented.

scholarly journals Image-Based Inertial Impact Test for Characterisation of Strain Rate Dependency of Ti6Al4V Titanium Alloy

2019 ◽  
Vol 60 (2) ◽  
pp. 235-248 ◽  
Author(s):  
T. Fourest ◽  
P. Bouda ◽  
L. C. Fletcher ◽  
D. Notta-Cuvier ◽  
E. Markiewicz ◽  
...  
Keyword(s):  
Titanium Alloy ◽  
Strain Rate ◽  
Impact Test ◽  
Rate Dependency ◽  
Ti6al4v Titanium Alloy ◽  
Strain Rate Dependency
Sign in / Sign up

Export Citation Format

Share Document