scholarly journals Celebrating Soft Matter's 10th Anniversary: Chain configuration and rate-dependent mechanical properties in transient networks

Soft Matter ◽  
2015 ◽  
Vol 11 (11) ◽  
pp. 2085-2096 ◽  
Author(s):  
Michelle K. Sing ◽  
Zhen-Gang Wang ◽  
Gareth H. McKinley ◽  
Bradley D. Olsen
Keyword(s):  
Mechanical Properties ◽  
10Th Anniversary ◽  
Rate Dependent ◽  
Transient Networks ◽  
Chain Configuration

Differential effects of static and cyclic stretching during elastase digestion on the mechanical properties of extracellular matrices

2007 ◽  
Vol 103 (3) ◽  
pp. 803-811 ◽  
Author(s):  
Rajiv Jesudason ◽  
Lauren Black ◽  
Arnab Majumdar ◽  
Phillip Stone ◽  
Bela Suki
Keyword(s):  
Mechanical Properties ◽  
Enzyme Activity ◽  
Failure Stress ◽  
Cyclic Stretch ◽  
Mechanical Forces ◽  
Peak Strain ◽  
Static Stretch ◽  
Cyclic Stretching ◽  
Rate Dependent ◽  
Physiological Processes

Enzyme activity plays an essential role in many physiological processes and diseases such as pulmonary emphysema. While the lung is constantly exposed to cyclic stretching, the effects of stretch on the mechanical properties of the extracellular matrix (ECM) during digestion have not been determined. We measured the mechanical and failure properties of elastin-rich ECM sheets loaded with static or cyclic uniaxial stretch (40% peak strain) during elastase digestion. Quasistatic stress-strain measurements were taken during 30 min of digestion. The incremental stiffness of the sheets decreased exponentially with time during digestion. However, digestion in the presence of static stretch resulted in an accelerated stiffness decrease, with a time constant that was nearly 3× smaller (7.1 min) than during digestion alone (18.4 min). These results were supported by simulations that used a nonlinear spring network model. The reduction in stiffness was larger during static than cyclic stretch, and the latter also depended on the frequency. Stretching at 20 cycles/min decreased stiffness less than stretching at 5 cycles/min, suggesting a rate-dependent coupling between mechanical forces and enzyme activity. Furthermore, pure digestion reduced the failure stress of the sheets from 88 ± 21 kPa in control to 29 ± 15 kPa ( P < 0.05), while static and cyclic stretch resulted in a failure stress of 7 ± 5 kPa ( P < 0.05). We conclude that not only the presence but the dynamic nature of mechanical forces have a significant impact on enzyme activity, hence the deterioration of the functional properties of the ECM during exposure to enzymes.

scholarly journals Strain-Rate-Dependent Deformation Behavior and Mechanical Properties of a Multi-Phase Medium-Manganese Steel

Metals ◽  
2019 ◽  
Vol 9 (3) ◽  
pp. 344 ◽  
Author(s):  
Simon Sevsek ◽  
Christian Haase ◽  
Wolfgang Bleck
Keyword(s):  
Mechanical Properties ◽  
Strain Rate ◽  
Strain Rate Sensitivity ◽  
Deformation Behavior ◽  
Rate Sensitivity ◽  
Manganese Steel ◽  
Strain Rates ◽  
Rate Dependent ◽  
Medium Manganese Steel ◽  
Multi Phase

The strain-rate-dependent deformation behavior of an intercritically annealed X6MnAl12-3 medium-manganese steel was analyzed with respect to the mechanical properties, activation of deformation-induced martensitic phase transformation, and strain localization behavior. Intercritical annealing at 675 °C for 2 h led to an ultrafine-grained multi-phase microstructure with 45% of mostly equiaxed, recrystallized austenite and 55% ferrite or recovered, lamellar martensite. In-situ digital image correlation methods during tensile tests revealed strain localization behavior during the discontinuous elastic-plastic transition, which was due to the localization of strain in the softer austenite in the early stages of plastic deformation. The dependence of the macroscopic mechanical properties on the strain rate is due to the strain-rate sensitivity of the microscopic deformation behavior. On the one hand, the deformation-induced phase transformation of austenite to martensite showed a clear strain-rate dependency and was partially suppressed at very low and very high strain rates. On the other hand, the strain-rate-dependent relative strength of ferrite and martensite compared to austenite influenced the strain partitioning during plastic deformation, and subsequently, the work-hardening rate. As a result, the tested X6MnAl12-3 medium-manganese steel showed a negative strain-rate sensitivity at very low to medium strain rates and a positive strain-rate sensitivity at medium to high strain rates.

scholarly journals Performance of Thermo-Mechanically Processed AA7075 Alloy at Elevated Temperatures—From Microstructure to Mechanical Properties

Metals ◽  
2020 ◽  
Vol 10 (7) ◽  
pp. 884 ◽  
Author(s):  
Seyed Vahid Sajadifar ◽  
Emad Scharifi ◽  
Ursula Weidig ◽  
Kurt Steinhoff ◽  
Thomas Niendorf
Keyword(s):  
Mechanical Properties ◽  
Elevated Temperatures ◽  
Tensile Tests ◽  
Uniaxial Tensile ◽  
Forming Process ◽  
Softening Mechanism ◽  
Rate Dependent ◽  
Heat Treated ◽  
Different Temperatures ◽  
Die Forming

This study focuses on the high temperature characteristics of thermo-mechanically processed AA7075 alloy. An integrated die forming process that combines solution heat treatment and hot forming at different temperatures was employed to process the AA7075 alloy. Low die temperature resulted in the fabrication of parts with higher strength, similar to that of T6 condition, while forming this alloy in the hot die led to the fabrication of more ductile parts. Isothermal uniaxial tensile tests in the temperature range of 200–400 °C and at strain rates ranging from 0.001–0.1 s−1 were performed on the as-received material, and on both the solution heat-treated and the thermo-mechanically processed parts to explore the impacts of deformation parameters on the mechanical behavior at elevated temperatures. Flow stress levels of AA7075 alloy in all processing states were shown to be strongly temperature- and strain-rate dependent. Results imply that thermo-mechanical parameters are very influential on the mechanical properties of the AA7075 alloy formed at elevated temperatures. Microstructural studies were conducted by utilizing optical microscopy and a scanning electron microscope to reveal the dominant softening mechanism and the level of grain growth at elevated temperatures.

Mechanical Properties of Bulk Nanocrystalline Silver-Using Compression Tests

2010 ◽  
Vol 152-153 ◽  
pp. 1313-1316
Author(s):  
Guo Jun Hu ◽  
Zhi Quan Hong
Keyword(s):  
Mechanical Properties ◽  
Coarse Grained ◽  
Strain Rates ◽  
Test Results ◽  
Compression Tests ◽  
Static Test ◽  
Rate Dependent ◽  
Average Grain Size ◽  
Bulk Nanocrystalline ◽  
The Relationship

In this paper, the compression test on the bulk nanocrystalline sliver ( n Ag) with average grain size of 50 nm was made. The stress-strain curves under different strain rates were obtained by test. The test results show that the mechanical behavior of n Ag is rate-dependent, and the dynamic compress yield stress are about 1.5 times of that n Ag in static test condition; The effect of strain harding on n Ag is smaller than that of coarse-grained silver (c Ag) in plastic deformation; The relationship between the yield strength and the logarithm of strain rate is approximately linear.

Characterizing the mechanical properties of tropoelastin protein scaffolds

2013 ◽  
Vol 1569 ◽  
pp. 45-50 ◽  
Author(s):  
Audrey C. Ford ◽  
Hans Machula ◽  
Robert S. Kellar ◽  
Brent A. Nelson
Keyword(s):  
Mechanical Properties ◽  
Elastic Modulus ◽  
Cell Attachment ◽  
Mechanical Design ◽  
Protein Composition ◽  
Tissue Scaffolds ◽  
Surrounding Tissue ◽  
Protein Scaffolds ◽  
Initial Stiffness ◽  
Rate Dependent

ABSTRACTThis paper reports on mechanical characterization of electrospun tissue scaffolds formed from varying blends of collagen and human tropoelastin. The electrospun tropoelastin-based scaffolds have an open, porous structure conducive to cell attachment and have been shown to exhibit strong biocompatibility, but the mechanical character is not well known. Mechanical properties were tested for scaffolds consisting of 100% tropoelastin and 1:1 tropoelastin-collagen blends. The results showed that the materials exhibited a three order of magnitude change in the initial elastic modulus when tested dry vs. hydrated, with moduli of 21 MPa and 0.011 MPa respectively. Noncrosslinked and crosslinked tropoelastin scaffolds exhibited the same initial stiffness from 0 to 50% strain, and the noncrosslinked scaffolds exhibited no stiffness at strains >∼50%. The elastic modulus of a 1:1 tropoelastin-collagen blend was 50% higher than that of a pure tropoelastin scaffold. Finally, the 1:1 tropoelastin-collagen blend was five times stiffer from 0 to 50% strain when strained at five times the ASTM standard rate. By systematically varying protein composition and crosslinking, the results demonstrate how protein scaffolds might be manipulated as customized biomaterials, ensuring mechanical robustness and potentially improving biocompatibility through minimization of compliance mismatch with the surrounding tissue environment. Moreover, the demonstration of strain-rate dependent mechanical behavior has implications for mechanical design of tropoelastin-based tissue scaffolds.

Nanoindentation of Poly (Methyl Methacrylate)

2000 ◽  
Vol 649 ◽  
Author(s):  
Michael J. Adams ◽  
David M. Gorman ◽  
Simon A. Johnson
Keyword(s):  
Experimental Data ◽  
Mechanical Properties ◽  
Penetration Depth ◽  
Polymeric Materials ◽  
Polymer Coatings ◽  
Organic Polymer ◽  
Berkovich Indenter ◽  
Homogeneous Half Space ◽  
Rate Dependent ◽  
Thin Polymer

ABSTRACTFor the indentation of an elastic-plastic homogeneous half-space with a pyramidal indenter, the load theoretically increases with the square of the total penetration depth. Experimental data are presented in the current paper that demonstrate the validity of this relationship for an organic polymer and a Berkovich indenter, provided that appropriate account is taken of the tip defect and viscoplasticity. It is also shown that a simple analytical solution exists for the ratio of the contact depth to the total penetration depth. These findings assist in identifying procedures for obtaining the rate-dependent mechanical properties of thin polymer coatings or polymeric materials with depth-dependent mechanical properties.

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