Time-Dependent Mechanical Behavior of Sheep Digital Tendons, Including the Effects of Preconditioning

2001 ◽  
Vol 124 (1) ◽  
pp. 78-84 ◽  
Author(s):  
A. Sverdlik ◽  
Y. Lanir
Keyword(s):  
Mechanical Properties ◽  
Material Characterization ◽  
Predictive Power ◽  
Structural Model ◽  
Strain Level ◽  
Time Dependent ◽  
Model Data ◽  
Reference Length ◽  
Good Agreement

The time-dependent mechanical properties of sheep digital extensor tendons were studied by sequences of stress-relaxation tests. The results exhibited irreversible preconditioning and reversible viscoelasticity. Preconditioning effects were manifested by stress decay during consecutive stretch cycles to the same strain level, accompanied by elongation of the tendon’s reference length. They intensified with increased strain level, and were reduced or became negligible as the strain decreased. The significance of intrinsic response mechanisms was studied via a structural model that includes viscoelasticity, preconditioning, and morphology of the tendon’s collagen fibers. Model/data comparisons showed good agreement and good predictive power, suggesting that preconditioning can be integrated into comprehensive material characterization of tendons.

Mechanical, Electrical and Thermal Characterization of Commercially Available LTCC Dielectric Tapes

2013 ◽  
Vol 543 ◽  
pp. 212-215
Author(s):  
Goran Radosavljević ◽  
Nelu Blaž ◽  
Andrea Marić ◽  
W. Smetana ◽  
Ljiljana Živanov
Keyword(s):  
Mechanical Properties ◽  
Surface Roughness ◽  
Electrical Properties ◽  
Material Characterization ◽  
Mechanical Characterization ◽  
Thermal Characterization ◽  
Material Parameters ◽  
Mechanical And Electrical Properties

Presented paper deals with mechanical and electrical properties of several commercially available LTCC (Low Temperature Co-fired Technology) tapes, as well as their thermal characterization. Three commercially available dielectric tape materials provided by Heraeus (CT700, CT707 and CT800) are investigated. The samples for determination of significant material parameters are prepared using the standard LTCC fabrication process. Results of the material characterization (chemical analysis, surface roughness electrical and mechanical properties) are presented. In addition thermo-electrical and-mechanical characterization of investigated tapes analysis is performed.

INVESTIGATIONS OF THE VISCOELASTICITY OF ESOPHAGEAL TISSUE USING INCREMENTAL STRESS-RELAXATION TEST AND CYCLIC EXTENSION TEST

2006 ◽  
Vol 06 (03) ◽  
pp. 261-272 ◽  
Author(s):  
W. YANG ◽  
T. C. FUNG ◽  
K. S. CHIAN ◽  
C. K. CHONG
Keyword(s):  
Stress Relaxation ◽  
Material Characterization ◽  
Predictive Ability ◽  
Time Dependent ◽  
Relaxation Test ◽  
Cyclic Test ◽  
Stress Relaxation Test ◽  
Esophageal Tissue ◽  
Linear Viscoelastic

The time-dependent mechanical properties of porcine esophagus were investigated experimentally and theoretically. It was hypothesized that the viscoelasticity was quasi-linear. The incremental stress-relaxation test was conducted to identify the material constants included in the quasi-linear viscoelastic (QLV) model. To verify the predictive ability of the model, the incremental cyclic test was performed. Hysteresis was calculated and compared with that predicted by the model. Results showed that stresses relaxed by 20–30% within the first 10 s and stabilized at 50% at 300 s. The QLV model was shown to be able to describe the viscoelasticity of esophagus across various stretch levels. The model could also predict the hysteresis during cyclic test well. It suggested that the QLV could be used as the material characterization of esophageal tissue.

scholarly journals Approaches for process and structural finite element simulations of braided ligament replacements

2016 ◽  
Vol 47 (3) ◽  
pp. 408-425 ◽  
Author(s):  
Thomas Gereke ◽  
Oliver Döbrich ◽  
Dilbar Aibibu ◽  
Jorg Nowotny ◽  
Chokri Cherif
Keyword(s):  
Mechanical Properties ◽  
Finite Element ◽  
Process Model ◽  
Structural Model ◽  
Structural Parameters ◽  
Healing Process ◽  
Resorbable Polymers ◽  
Wide Range ◽  
Experimental Trials ◽  
Good Agreement

To prevent the renewed rupture of ligaments and tendons prior to the completed healing process, which frequently occurs in treated ruptured tendons, a temporary support structure is envisaged. The limitations of current grafts have motivated the investigation of tissue-engineered ligament replacements based on the braiding technology. This technology offers a wide range of flexibility and adjustable geometrical and structural parameters. The presented work demonstrates the possible range for tailoring the mechanical properties of polyester braids and a variation of the braiding process parameters. A finite element simulation model of the braiding process was developed, which allows the optimization of production parameters without the performance of further experimental trials. In a second modelling and simulation step, mechanical properties of the braided structures were virtually determined and compared with actual tests. The digital element approach was used for the yarns in the numerical model. The results show very good agreement for the process model in terms of braiding angles and good agreement for the structural model in terms of force-strain behaviour. With a few adaptions, the models can, thus, be applied to actual ligament replacements made of resorbable polymers.

Characterization of Shear Interfacial Mechanical Properties in Adhesive Layer by Hybrid/Inverse Method

2015 ◽  
Vol 1090 ◽  
pp. 12-17
Author(s):  
Juan Wang ◽  
Jun Qiang Li
Keyword(s):  
Mechanical Properties ◽  
Inverse Method ◽  
Adhesive Layer ◽  
Time Dependent ◽  
Independent Experiment ◽  
Inverse Identification ◽  
Identification Method ◽  
Experiment Verification ◽  
Structural Adhesive

A novel hybrid/inverse identification method is developed to predict the time-dependent shear interfacial mechanical properties of the adhesive layer. In this method, to effectively predict the mechanical behavior of the shear joints, which was made of the aluminum alloy and silica gel structural adhesive, a novel time-dependent shear interfacial model was embedded in the joints to denote the adhesive layer. Based on the interfacial failure results obtained from experiment and the numerical simulation, the hybrid/inverse identifying time-dependent interfacial parameters is constructed by means of genetic algorithms and the time-dependent interfacial adhesive parameters can then be determined. By independent experiment verification, it is found that the hybrid/inverse identification method is promising in identifying time-dependent interfacial parameters of adhesive bonded structures.

Preliminary Characterization of Resilin Isolated from the Cockroach, Periplaneta Americana

1992 ◽  
Vol 292 ◽  
Author(s):  
Elizabeth Craig Lombardi ◽  
David L. Kaplan
Keyword(s):  
Mechanical Properties ◽  
Amino Acid ◽  
Amino Acid Analysis ◽  
Periplaneta Americana ◽  
Insect Cuticle ◽  
Oligonucleotide Probes ◽  
Protein Matrix ◽  
Tryptic Fragment ◽  
Good Agreement

AbstractWe would like to mimic the mechanical properties of animal systems for the development of novel materials. Insect cuticle serves as one source of inspiration for the design of these materials. Cuticle is composed of chitin embedded in a protein matrix which may also contain plasticizers, fillers, crosslinkers, and minerals. The specific properties of the cuticle depend on the type, amount and interactions between each component. We are renewing the investigation of the elastic cuticle, resilin. Resilin, a protein-based elastomer first described in the early 1960s, has properties which have been reported to be most like those of ideal rubbers. We have examined resilin isolated from the prealar arms of the cockroach, Periplaneta americana. The results of amino acid analysis are in good agreement with earlier data reported for resilin. A series of tryptic fragments have been isolated and sequenced. These peptides have been used for the design of oligonucleotide probes for the identification of the gene(s) from a teneral cockroach cDNA library. A biopolymer, based on one tryptic fragment, has been designed and synthesized. We are continuing to treat resilin with residue specific proteases in order to map the resilin protein.

scholarly journals High-throughput microfluidic characterization of erythrocyte shape and mechanical variability

2018 ◽  
Author(s):  
Felix Reichel ◽  
Johannes Mauer ◽  
Ahmad Ahsan Nawaz ◽  
Gerhard Gompper ◽  
Jochen Guck ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Red Blood Cells ◽  
High Throughput ◽  
Blood Cells ◽  
Microvascular Blood Flow ◽  
Flow Conditions ◽  
Wide Range ◽  
Single Well ◽  
Good Agreement

The motion of red blood cells (RBCs) in microchannels is important for microvascular blood flow and biomedical applications such as blood analysis in microfluidics. The current understanding of the complexity of RBC shapes and dynamics in microchannels is mainly based on several simulation studies, but there are a few systematic experimental investigations. Here, we present a combined study, which systematically characterizes RBC behavior for a wide range of flow rates and channel sizes. Even though simulations and experiments generally show good agreement, experimental observations demonstrate that there is no single well-defined RBC state for fixed flow conditions, but rather a broad distribution of states. This result can be attributed to the inherent variability in RBC mechanical properties, which is confirmed by a model that takes the variation in RBC shear elasticity into account. This represents a significant step toward a quantitative connection between RBC behavior in microfluidic devices and their mechanical properties, which is essential for a high-throughput characterization of diseased cells.Significance StatementThe ability to change shape is crucial for the proper functioning of red blood cells under harsh conditions in the microvasculature, since their shapes strongly affect the flow behavior of whole blood. Our results from simulations and systematic experiments reveal the shapes and dynamics of red blood cells for different flow conditions and channel dimensions, generally in good agreement. However, in the experiments, cells do not exhibit a single well-defined shape for fixed flow conditions. We show that this distribution of shapes can be attributed to the variability in mechanical properties of red blood cells.

Optimal Design of Biaxial Tests for Structural Material Characterization of Flat Tissues

1996 ◽  
Vol 118 (1) ◽  
pp. 41-47 ◽  
Author(s):  
Y. Lanir ◽  
O. Lichtenstein ◽  
O. Imanuel
Keyword(s):  
Optimal Design ◽  
Material Characterization ◽  
Structural Model ◽  
Optimal Designs ◽  
Model Parameters ◽  
Optimal Sampling ◽  
Material Symmetry ◽  
Wide Range ◽  
Biaxial Tests

A rational methodology is developed for optimal design of biaxial stretch tests intended for estimating material parameters of flat tissues. It is applied to a structural model with a variety of constitutive equations and test protocols, and for a wide range of parameter levels. The results show nearly identical optimal designs under all circumstances. Optimality is obtained with two uniaxial stretch tests at mutually normal directions inclined by 22.5 deg to the axes of material symmetry. Protocols which include additional equibiaxial tests provide superior estimation with lower variance of estimates. Tests performed at angles 0, 45, and 90 deg to the axes of material symmetry provide unreliable estimates. The optimal sampling is variable and depends on the protocols and model parameters. In conclusion, the results indicate that biaxial tests can be improved over presently common procedures and show that this conclusion applies for a variety of circumstances.

Characterization of Thin Films using Micromechanical Structures

1992 ◽  
Vol 276 ◽  
Author(s):  
R. I. Pratt ◽  
G. C. Johnson ◽  
R. T. Howe ◽  
D. J. Nikkel
Keyword(s):  
Thin Films ◽  
Mechanical Properties ◽  
Nonlinear Dynamic ◽  
Material Characterization ◽  
Intrinsic Stress ◽  
Nonlinear Dynamic Response ◽  
Wafer Substrate ◽  
Micromechanical Structures ◽  
Geometrically Constrained

ABSTRACTMicromechanical structures designed for material characterization through analysis of their nonlinear dynamic response are presented. The structures consist of a rigid movable mass supported by beams which are attached to the wafer substrate. The structures are designed so that they are geometrically constrained, which is the source of their nonlinearity. The nonlinearity is shown to be well modeled by Duffing's equation for a stiffening spring and it is this model which is used to fit the test data to the desired mechanical properties, namely Young's modulus, intrinsic stress and damping.

scholarly journals Characterization of Sustainable Robotic Materials and Finite Element Analysis of Soft Actuators Under Biodegradation

2021 ◽  
Vol 8 ◽  
Author(s):  
Toshiaki Nagai ◽  
Ashitaka Kurita ◽  
Jun Shintake
Keyword(s):  
Mechanical Properties ◽  
Biodegradable Materials ◽  
Biodegradable Material ◽  
Element Analysis ◽  
Soft Actuator ◽  
Degradation Rates ◽  
Soft Actuators ◽  
And Control ◽  
Good Agreement

Biodegradability is an important property for soft robots that makes them environmentally friendly. Many biodegradable materials have natural origins, and creating robots using these materials ensures sustainability. Hence, researchers have fabricated biodegradable soft actuators of various materials. During microbial degradation, the mechanical properties of biodegradable materials change; these cause changes in the behaviors of the actuators depending on the progression of degradation, where the outputs do not always remain the same against identical inputs. Therefore, to achieve appropriate operation with biodegradable soft actuators and robots, it is necessary to reflect the changes in the material properties in their design and control. However, there is a lack of insight on how biodegradable actuators change their actuation characteristics and how to identify them. In this study, we build and validate a framework that clarifies changes in the mechanical properties of biodegradable materials; further, it allows prediction of the actuation characteristics of degraded soft actuators through simulations incorporating the properties of the materials as functions of the degradation rates. As a biodegradable material, we use a mixture of gelatin and glycerol, which is fabricated in the form of a pneumatic soft actuator. The experimental results show that the actuation performance of the physical actuator reduces with the progression of biodegradation. The experimental data and simulations are in good agreement (R2 value up to 0.997), thus illustrating the applicability of our framework for designing and controlling biodegradable soft actuators and robots.

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