scholarly journals A Kinetic Study of the Emerging of Grains and Block of Grains from the Inner Volume to the Free Surface of a Cd-Zn Alloy Superplastically Deformed

2012 ◽  
Vol 2012 ◽  
pp. 1-6
Author(s):  
J. A. Montemayor-Aldrete ◽  
R. Mendez-Olvera ◽  
P. Ugalde-Velez ◽  
G. Torres-Villaseñor ◽  
M. del Castillo-Mussot
Keyword(s):  
Shear Stress ◽  
Free Surface ◽  
Measurement Technique ◽  
Superplastic Deformation ◽  
Room Temperature ◽  
Local Measurement ◽  
Nanocrystalline Structures ◽  
Microcrystalline Materials ◽  
Zn Alloy ◽  
Mismatch Angle

A local measurement technique for the study of the kinetic processes of emerging of grains or blocks of grains from the inner volume to the free surface of superplastic materials during deformation is presented and used for the case of the Cd-Zn eutectic alloy deformed at room temperature. This technique could be used to evaluate the approximate time of fracture due to fissure or cavitation growth in samples under superplastic deformation. In principle, this technique will be useful for the development of physical procedures, which allows retarding the process of formation of low mismatch angle, , between neighboring grains, process which gives place to blocks of grains which dynamically behave as units under the shear stress action. For materials with nanocrystalline structures, such processes are expected to be higher than those of the case of microcrystalline materials.

On the room temperature deformation mechanisms of a Mg–Y–Zn alloy with long-period-stacking-ordered structures

2015 ◽  
Vol 82 ◽  
pp. 414-423 ◽  
Author(s):  
Jin-Kyung Kim ◽  
Stefanie Sandlöbes ◽  
Dierk Raabe
Keyword(s):  
Room Temperature ◽  
Deformation Mechanisms ◽  
Temperature Deformation ◽  
Ordered Structures ◽  
Long Period ◽  
Zn Alloy

Defect Structure of MEV Si Implantation in GaAs

1988 ◽  
Vol 126 ◽  
Author(s):  
S.-Tong Lee ◽  
G. Braunstein ◽  
Samuel Chen
Keyword(s):  
Free Surface ◽  
Defect Structure ◽  
Room Temperature ◽  
Surface Region ◽  
Peak Position ◽  
Lattice Disorder ◽  
Depth Profiles ◽  
Trim Calculation ◽  
Good Agreement

ABSTRACTThe defect and atomic profiles for MeV implantation of Si in GaAs were investigated using He++ channeling, TEM, and SIMS. Doses of 1–10 × 1015Si/cm2 at 1–3 MeV were used. MeV implantation at room temperature rendered only a small amount of lattice disorder in GaAs. Upon annealing at 400°C for 1 h or 800°C for 30 a, we observed a ‘defect-free’ surface region (- 1 μ for 3 MeV implant). Below this region, extensive secondary defects were formed in a band which was 0.7 μ wide and centered at 2 μ for 3 MeV implant. These defects were mostly dislocations lying in the [111] plane. SIMS depth profiles of Si implants showed the Si peak to be very close to the peak position of the defects. The experimental profiles of Si were compared to the TRIM calculation; generally good agreement existed among the peak positions.

Evaluation of a film-based wall shear stress measurement technique in a turbulent channel flow

2016 ◽  
Vol 70 ◽  
pp. 437-442 ◽  
Author(s):  
Omid Amili ◽  
Michael D. Hind ◽  
Jonathan W. Naughton ◽  
Julio Soria
Keyword(s):  
Shear Stress ◽  
Wall Shear Stress ◽  
Channel Flow ◽  
Measurement Technique ◽  
Stress Measurement ◽  
Turbulent Channel Flow ◽  
Wall Shear ◽  
Wall Shear Stress Measurement

A bioprinted composite hydrogel with controlled shear stress on cells

2020 ◽  
pp. 095441192097668
Author(s):  
Amirhossein Bakhtiiari ◽  
Rezvan Khorshidi ◽  
Fatemeh Yazdian ◽  
Hamid Rashedi ◽  
Meisam Omidi
Keyword(s):  
Shear Stress ◽  
Cell Viability ◽  
Room Temperature ◽  
Degradation Rate ◽  
Diffusion Rate ◽  
Sol Gel ◽  
Three Dimensional ◽  
Simulation Software ◽  
Sol Gel Transition ◽  
Gel Transition

In recent decades, three dimensional (3D) bio-printing technology has found widespread use in tissue engineering applications. The aim of this study is to scrutinize different parameters of the bioprinter – with the help of simulation software – to print a hydrogel so much so that avoid high amounts of shear stress which is detrimental for cell viability and cell proliferation. Rheology analysis was done on several hydrogels composed of different percentages of components: alginate, collagen, and gelatin. The results have led to the combination of percentages collagen:alginate:gelatin (1:4:8)% as the best condition which makes sol-gel transition at room temperature possible. The results have shown the highest diffusion rate and cell viability for the cross-linked sample with 1.5% CaCl2 for the duration of 1 h. Finally, we have succeeded in printing the hydrogel that is mechanically strong with suitable degradation rate and cell viability.

Coupling between the mesoscopic dynamics and shear stress of a room-temperature ionic liquid

2018 ◽  
Vol 20 (26) ◽  
pp. 17809-17817 ◽  
Author(s):  
Tsuyoshi Yamaguchi
Keyword(s):  
Shear Stress ◽  
Ionic Liquid ◽  
Domain Structure ◽  
Shear Viscosity ◽  
Room Temperature ◽  
Room Temperature Ionic Liquid

Shear viscosity of an ionic liquid is governed by the dynamics of the charge-alternation mode irrespective of the presence of the domain structure.

Nuvolve Engineered Polysaccharides as Performance-Enhancing Additives for Latex Wood Adhesives

2020 ◽  
Vol 70 (3) ◽  
pp. 293-301
Author(s):  
Joseph J. Marcinko ◽  
Christian Lenges ◽  
Kyle Kim ◽  
Monica Harvey
Keyword(s):  
Nuclear Magnetic Resonance ◽  
Shear Stress ◽  
Acer Saccharum ◽  
Room Temperature ◽  
Mechanical Analysis ◽  
Enzymatic Polymerization ◽  
Resonance Spectroscopy ◽  
Wood Adhesives ◽  
Wood Bonding ◽  
Performance Enhancing

Abstract The work presented here focuses on the, incorporation of an engineered polysaccharide polymer, α-1,3-glucan, derived from the enzymatic polymerization of sucrose, as a performance-enhancing additive for commercial, latex-based wood adhesives used in wood bonding applications. Adhesive performance was measured on hard maple (Acer saccharum) using ASTM Standard Method D-905. Dynamic mechanical analysis and solid-state nuclear magnetic resonance spectroscopy were the characterization techniques used to assess the properties of room-temperature–cured adhesive films. Significant increases in shear stress were observed for these formulated latex adhesives containing the polysaccharide polymer.

Conductivity, Electrodeposition and Magnetic Property of Cobalt(II) and Dysprosium Chloride in Zinc Chloride-1-Ethyl-3-Methylimidazolium Chloride Room Temperature Molten Salt

2003 ◽  
Vol 58 (1) ◽  
pp. 139-146 ◽  
Author(s):  
Hsin-Yi Hsu ◽  
Chao-Chen Yang
Keyword(s):  
Zinc Chloride ◽  
Room Temperature ◽  
Deposition Potential ◽  
Nucleation Density ◽  
Alloy Electrodeposition ◽  
Viscosity Increase ◽  
Different Temperatures ◽  
Time Required ◽  
Computerized System ◽  
Zn Alloy

Abstract Electric conductivity of the molten zinc chloride-1-ethyl-3-methylimidazolium chloride phases has been measured by a computerized system using the d.c. four-probes method. The sequence of the conductivities for the different component melts is ZnCl2-EMIC > ZnCl2-EMIC-CoCl2 > ZnCl2- EMIC-DyCl3 > ZnCl2-EMIC-CoCl2-DyCl3. The results may be explained in terms of the viscosity increase due to the complex formation. The electrochemistry and the nucleation mechanism of cobalt(II) or/and dysprosium chloride in acidic ZnCl2-EMIC melts have been investigated by cyclic voltammetry and chronoamperometry at different temperatures, respectively. The results of the SEM and VSM analyses reveal that reduction of Dy3+ to Dy2+ may have occurred, while reduction of Dy3+ to Dy(0) is conjectured to play no role. Moreover, the results of chronoamperometry experiments show that nucleation in the alloy electrodeposition is instantaneous, and that, as the applied deposition potential becomes more negative, the nucleation density increases, which rapidly shortens the time required for the diffusion zones to overlap. Electrodeposition of a Dy-Co-Zn alloy on a Ni or Cu sheet from the 50-50 mol% ZnCl2-EMIC melt containing 1.687 mol% CoCl2 and 1.114 mol% DyCl3 has been accomplished, and the morphology and the composition have been analyzed by SEM and EDS, respectively. The magnetism of the deposited layer is discussed based on the results of the VSM analysis.

scholarly journals Understanding controversies in the α-ω and ω-β phase transformations of zirconium from nonhydrostatic thermodynamics

2019 ◽  
Vol 9 (1) ◽  
Author(s):  
Lin Zhang ◽  
Ying-Hua Li ◽  
Yan-Qin Gu ◽  
Ling-Cang Cai
Keyword(s):  
Shear Stress ◽  
Phase Transformations ◽  
Room Temperature ◽  
Solid Medium ◽  
Thermodynamic Formalism ◽  
Initial Pressure ◽  
Theoretical Explanation ◽  
Β Phase ◽  
Key Factor ◽  
The Impact

AbstractSignificant debate has been noted in the α-ω and ω-β phase transformations of zirconium. The initial pressure of the α-to-ω transformation at room temperature has been reported to vary from 0.25 to 7.0 GPa, while the hydrostatic transformation is believed to occur at approximately 2.2 GPa. Shear stress is commonly considered as a key factor leading to the discrepancy. However, the principal mechanisms previously proposed concluded that the phase transformation pressure would be decreased in the presence of shear stress. The experimental results of the α-ω transformation in zirconium are contrary to this conclusion. In the ω-β phase diagram of zirconium, the dT/dP along the phase boundary near the α-ω-β triple-point was reported to be either positive or negative, but no theoretical explanation, especially a quantitative one, has been proposed. This article aimed to quantitatively investigate and explain the controversies reported in the α-ω and ω-β phase transformations of zirconium by applying a new nonhydrostatic thermodynamic formalism for solid medium, which has recently been proposed and is capable of quantitatively estimating the impact of shear stress on phase transformations in solids.

High-Temperature Fatigue Properties of Single Crystal Superalloys in Air and Hydrogen

2001 ◽  
Author(s):  
Nagaraj K. Arakere
Keyword(s):  
High Pressure ◽  
Shear Stress ◽  
High Temperature ◽  
Fatigue Life ◽  
Single Crystal ◽  
Room Temperature ◽  
Turbine Blades ◽  
The Core ◽  
Blade Tip ◽  
Pressure Hydrogen

Hot section components in high performance aircraft and rocket engines are increasingly being made of single crystal nickel superalloys such as PWA1480, PWA1484, CMSX-4 and Rene N-4 as these materials provide superior creep, stress rupture, melt resistance and thermomechanical fatigue capabilities over their polycrystalline counterparts. Fatigue failures in PWA1480 single crystal nickel-base superalloy turbine blades used in the Space Shuttle Main Engine (SSME) fuel turbopump are discussed. During testing many turbine blades experienced Stage II non-crystallographic fatigue cracks with multiple origins at the core leading edge radius and extending down the airfoil span along the core surface. The longer cracks transitioned from stage II fatigue to crystallographic stage I fatigue propagation, on octahedral planes. An investigation of crack depths on the population of blades as a function of secondary crystallographic orientation (β) revealed that for β = 45+/- 15 degrees tip cracks arrested after some growth or did not initiate at all. Finite element analysis of stress response at the blade tip, as a function of primary and secondary crystal orientation, revealed that there are preferential β orientations for which crack growth is minimized at the blade tip. To assess blade fatigue life and durability extensive testing of uniaxial single crystal specimens with different orientations has been tested over a wide temperature range in air and hydrogen. A detailed analysis of the experimentally determined Low Cycle Fatigue (LCF) properties for PWA1480 and SC 7-14-6 single crystal materials as a function of specimen crystallographic orientation is presented at high temperature (75 F – 1800 F) in high-pressure hydrogen and air. Fatigue failure parameters are investigated for LCF data of single crystal material based on the shear stress amplitudes on the 24 octahedral and 6 cube slip systems for FCC single crystals. The max shear stress amplitude [Δτmax] on the slip planes reduces the scatter in the LCF data and is found to be a good fatigue damage parameter, especially at elevated temperatures. The parameter Δτmax did not characterize the room temperature LCF data in high-pressure hydrogen well because of the noncrystallographic eutectic failure mechanism activated by hydrogen at room temperature. Fatigue life equations are developed for various temperature ranges and environmental conditions based on power-law curve fits of the failure parameter with LCF test data. These curve fits can be used for assessing blade fatigue life.

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