Atomistic Simulation of Structural and Mechanical Properties of the AMgF 3 (A = K, Rb, and Cs) Compounds Under Hydrostatic Pressure

2019 ◽  
Vol 41 (7) ◽  
pp. 646-652 ◽  
Author(s):  
Afranio Sousa ◽  
Heveson Lima
Keyword(s):  
Mechanical Properties ◽  
Hydrostatic Pressure ◽  
Atomistic Simulation

scholarly journals Accelerated degradation of polyetheretherketone and its composites in the deep sea

2018 ◽  
Vol 5 (4) ◽  
pp. 171775 ◽  
Author(s):  
Hao Liu ◽  
Jianzhang Wang ◽  
Pengfei Jiang ◽  
Fengyuan Yan
Keyword(s):  
Mechanical Properties ◽  
Wear Resistance ◽  
Hydrostatic Pressure ◽  
Deep Sea ◽  
Normal Pressure ◽  
Wear Behaviour ◽  
Special Equipment ◽  
Accelerated Degradation ◽  
Seawater Environment

The performance of polymer composites in seawater, under high hydrostatic pressure (typically few tens of MPa), for simulating exposures at great depths in seas and oceans, has been little studied. In this paper, polyetheretherketone (PEEK) and its composites reinforced by carbon fibres and glass fibres were prepared. The seawater environment with different seawater hydrostatic pressure ranging from normal pressure to 40 MPa was simulated with special equipment, in which the seawater absorption and wear behaviour of PEEK and PEEK-based composites were examined in situ . The effects of seawater hydrostatic pressure on the mechanical properties, wear resistance and microstructure of PEEK and its composites were focused on. The results showed that seawater absorption of PEEK and its composites were greatly accelerated by increased hydrostatic pressure in the deep sea. Affected by seawater absorption, both for neat PEEK and composites, the degradation on mechanical properties, wear resistance and crystallinity were induced, the degree of which was increasingly serious with the increase of hydrostatic pressure of seawater environment. There existed a good correlation in an identical form of exponential function between the wear rate and the seawater hydrostatic pressure. Moreover, the corresponding mechanisms of the effects of deep-sea hydrostatic pressure were also discussed.

An experimental study of the mechanical properties of seamless and overlapped stitched composite tubes under hydrostatic pressure, lateral compression, and impact

2020 ◽  
Vol 55 (7-8) ◽  
pp. 212-221
Author(s):  
Masoud Yekani Fard ◽  
Brian Raji ◽  
Bao Doan ◽  
Michael Brooks ◽  
John Woodward ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Hydrostatic Pressure ◽  
Maximum Pressure ◽  
Seamless Tube ◽  
Lateral Compression ◽  
Composite Tubes ◽  
Functional Failure ◽  
Stress Risers ◽  
The Matrix ◽  
Extent Of Damage

Mechanical properties and damage mechanisms of closed circular preforms and overlapped stitched composite tubes under lateral compression, impact, and hydrostatic pressure were studied. The functional failure pressures of the tubes with different boundary conditions were determined and compared. Stitch at the overlapped zone creates stress risers that lead to premature functional failure at a hydrostatic pressure at ∼1/3 of the theoretical maximum pressure of the tube as delamination occurs at the overlapping region. Seamless tubes reached values close to theoretical operating hydrostatic pressures before leakage was observed at the tube ends. The deflection of the overlapped stitched tube due to lateral compression is less than the deflection in the seamless tube, and it is limited to 5% of the inner diameter using the Spangler equation. Brittle kinks, cracks, and delamination occur in overlapped stitched tubes while seamless tubes regain the shape with limited localized cracks after unloading. The fabric architecture of a seamless tube allows for the reorientation of fiber tows as cracks develop in the matrix, thus resulting in a lesser extent of damage when the tube is subject to impact.

Length Scale Effects in Materials Deformation of Nano and Microscale Au Structures

2009 ◽  
Author(s):  
Jie Lian ◽  
Junlan Wang
Keyword(s):  
Mechanical Properties ◽  
Elastic Modulus ◽  
Size Effect ◽  
Sample Size ◽  
Atomistic Simulation ◽  
Scale Effects ◽  
Elastic Recovery ◽  
Boundary Effect ◽  
Dislocation Nucleation ◽  
Atomistic Simulations

In this study, intrinsic size effect — strong size dependence of mechanical properties — in materials deformation was investigated by performing atomistic simulation of compression on Au (114) pyramids. Sample boundary effect — inaccurate measurement of mechanical properties when sample size is comparable to the indent size — in nanoindentation was also investigated by performing experiments and atomistic simulations of nanoindentation into nano- and micro-scale Au pillars and bulk Au (001) surfaces. For intrinsic size effect, dislocation nucleation and motions that contribute to size effect were analyzed for studying the materials deformation mechanisms. For sample boundary effect, in both experiments and atomistic simulation, the elastic modulus decreases with increasing indent size over sample size ratio. Significantly different dislocation motions contribute to the lower value of the elastic modulus measured in the pillar indentation. The presence of the free surface would allow the dislocations to annihilate, causing a higher elastic recovery during the unloading of pillar indentation.

Hydrostatic pressure induced structural phase transition and mechanical properties of fluoroperovskite

2019 ◽  
Vol 31 (50) ◽  
pp. 505406 ◽  
Author(s):  
Hao Cheng ◽  
Ai-Jie Mao ◽  
Xiao-Rong Cheng ◽  
Hao Tian ◽  
Xi-Long Dou ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Phase Transition ◽  
Hydrostatic Pressure ◽  
Structural Phase Transition ◽  
Structural Phase

scholarly journals Potato Starch Hydrogels Produced by High Hydrostatic Pressure (HHP): A First Approach

Polymers ◽  
2019 ◽  
Vol 11 (10) ◽  
pp. 1673 ◽  
Author(s):  
Dominique Larrea-Wachtendorff ◽  
Gipsy Tabilo-Munizaga ◽  
Giovanna Ferrari
Keyword(s):  
Mechanical Properties ◽  
Hydrostatic Pressure ◽  
High Hydrostatic Pressure ◽  
Potato Starch ◽  
Water Concentration ◽  
Medium Size ◽  
Processing Temperature ◽  
Processing Conditions ◽  
Scanning Calorimetry ◽  
Absorption Bands

Starch-based hydrogels have received considerable interest due to their safe nature, biodegradability and biocompatibility. The aim of this study was to verify the possibility of producing natural hydrogels based on potato starch by high hydrostatic pressure (HHP), identifying suitable processing conditions allowing to obtain stable hydrogels, as well as to characterize structural and mechanical properties of these products. Sieved (small size granules and medium size granules) and unsieved potato starch samples were used to prepare aqueous suspensions of different concentrations (10–30% w/w) which were processed at 600 MPa for 15 min at different temperatures (25, 40 and 50 °C). Products obtained were characterized by different techniques (light and polarized microscopy, Fourier transform infrared spectroscopy (FTIR), rheology and differential scanning calorimetry (DSC)). Results obtained so far demonstrated that potato starch suspensions (20% starch–water concentration (w/w)) with granules mean size smaller than 25 µm treated at 600 MPa for 15 min and 50 °C showed a complete gelatinization and gel-like appearance. Potato HHP hydrogels were characterized by high viscosity, shear-thinning behavior and a highly structured profile (G’ >> G’’). Moreover, their FTIR spectra, similarly to FTIR profiles of thermal gels, presented three absorption bands in the characteristic starch-gel region (950–1200 cm−1), whose intensity increased with decreasing the particle size and increasing the processing temperature. In conclusion, potato starch hydrogels produced by HHP in well-defined processing conditions exhibited excellent mechanical properties, which can be tailored according to the requirements of the different applications envisaged.

Probing the mechanical properties of carbon nanohorns subjected to uniaxial compression and hydrostatic pressure

Carbon ◽  
2017 ◽  
Vol 125 ◽  
pp. 236-244 ◽  
Author(s):  
Yanli Nan ◽  
Bo Li ◽  
Xiang Zhao ◽  
Xiaolong Song ◽  
Lei Su
Keyword(s):  
Mechanical Properties ◽  
Hydrostatic Pressure ◽  
Uniaxial Compression ◽  
Carbon Nanohorns
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