Model for the robust mechanical behavior of nacre

2001 ◽  
Vol 16 (9) ◽  
pp. 2475-2484 ◽  
Author(s):  
A. G. Evans ◽  
Z. Suo ◽  
R. Z. Wang ◽  
I. A. Aksay ◽  
M. Y. He ◽  
...  
Keyword(s):  
Experimental Study ◽  
Mechanical Behavior ◽  
Inelastic Deformation ◽  
Inelastic Behavior ◽  
Stress Strain ◽  
Recent Experimental Study ◽  
Structural Robustness ◽  
Measured Stress

The inelastic deformation of nacre that leads to its structural robustness has been characterized in a recent experimental study. This article develops a model for the inelastic behavior, measured in tension, along the axis of the aragonite plates. The model is based on observations for abalone nacre that the inelasticity is associated with periodic dilatation bands. These bands contain coordinated separations at the periphery of the plates. The separations open as the material strains. The response is attributed to nanoscale asperities on the surfaces of the plates. The model calculates the stresses needed to displace the plates, resisted by elastic contacts at the asperities. The results are compared with the measured stress/strain curves.

Effect of reverse thermoelastic phase transformation on stress of onset of structural deformation in titanium nickelide

2021 ◽  
pp. 2-10
Author(s):  
A. A. Movchan ◽  
◽  
S. A. Kazarina ◽  
A. L. Silchenko ◽  
◽  
...  
Keyword(s):  
Experimental Study ◽  
Phase Transformation ◽  
Inelastic Deformation ◽  
Titanium Nickelide ◽  
Structural Deformation ◽  
Isotropic Hardening ◽  
Reverse Phase ◽  
Maximum Value ◽  
Study Results ◽  
Thermoelastic Phase Transformation

The experimental study results of the dependence in the stress value of the onset of the structural deformation on the degree of the reverse phase transformation occurring after the complete direct martensitic transformation in titanium nickelide are described. It is established that these results are qualitatively and quantitatively correctly described in the framework of the model according to which the maximum value of the intensity of the intrinsic inelastic deformation of the martensitic part of the representative volume of the shape-memory alloy is used as a parameter of isotropic hardening.

scholarly journals Comparison of waveform-derived corneal stiffness and stress-strain extensometry-derived corneal stiffness using different cross-linking irradiances: an experimental study with air-puff applanation of ex vivo porcine eyes

2020 ◽  
Vol 258 (10) ◽  
pp. 2173-2184 ◽  
Author(s):  
Robert Herber ◽  
Mathew Francis ◽  
Eberhard Spoerl ◽  
Lutz E. Pillunat ◽  
Frederik Raiskup ◽  
...  
Keyword(s):  
Experimental Study ◽  
Ex Vivo ◽  
Cross Linking ◽  
Displacement Curve ◽  
Stress Strain ◽  
Strain Measurements ◽  
Deflection Amplitude ◽  
Force Displacement ◽  
Stiffening Effect ◽  
Porcine Eyes

Abstract Purpose To assess corneal stiffening of standard (S-CXL) and accelerated (A-CXL) cross-linking protocols by dynamic corneal response parameters and corneal bending stiffness (Kc[mean/linear]) derived from Corvis (CVS) Scheimpflug-based tonometry. These investigations were validated by corneal tensile stiffness (K[ts]), derived from stress-strain extensometry in ex vivo porcine eyes. Methods Seventy-two fresh-enucleated and de-epithelized porcine eyes were soaked in 0.1% riboflavin solution including 10% dextran for 10 min. The eyes were separated into four groups: controls (n = 18), S-CXL (intensity in mW/cm2*time in min; 3*30) (n = 18), A-CXL (9*10) (n = 18), and A-CXL (18*5) (n = 18), respectively. CXL was performed using CCL Vario. CVS measurements were performed on all eyes. Subsequently, corneal strips were extracted by a double-bladed scalpel and used for stress-strain measurements. K[ts] was calculated from a force-displacement curve. Mean corneal stiffness (Kc[mean]) and constant corneal stiffness (Kc[linear]) were calculated from raw CVS data. Results In CVS, biomechanical effects of cross-linking were shown to have a significantly decreased deflection amplitude as well as integrated radius, an increased IOP, and SP A1 (P < 0.05). Kc[mean]/Kc[linear] were significantly increased after CXL (P < 0.05). In the range from 2 to 6% strain, K[ts] was significantly higher in S-CXL (3*30) compared to A-CXL (9*10), A-CXL (18*5), and controls (P < 0.05). At 8% to 10% strain, all protocols induced a higher stiffness than controls (P < 0.05). Conclusion Several CVS parameters and Kc[mean] as well as Kc[linear] verify corneal stiffening effect after CXL on porcine eyes. S-CXL seems to have a higher tendency of stiffening than A-CXL protocols have, which was demonstrated by Scheimpflug-based tonometry and stress-strain extensometry.

Experimental study of the mechanical behavior of FRP-reinforced concrete canvas panels

2017 ◽  
Vol 176 ◽  
pp. 608-616 ◽  
Author(s):  
Fangyuan Zhang ◽  
Huisu Chen ◽  
Xiangyu Li ◽  
Hui Li ◽  
Tao Lv ◽  
...  
Keyword(s):  
Experimental Study ◽  
Reinforced Concrete ◽  
Mechanical Behavior
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