Article
Materials Science, Multidisciplinary
Bin Li, Janel Leung
Summary: The migration of symmetric tilt grain boundaries (GBs) in face centered cubic copper under a shear strain at 100 K was studied. Results showed that the angles between specific atomic planes could determine the mode of motion of the GB, whether it is by shear coupling, hybrid mode of shear coupling + sliding, or only GB sliding. Structural analyses revealed atomic planes behavior during shear coupling, allowing the identification of transformation units and rate-limiting factors for lattice transformation.
Article
Nanoscience & Nanotechnology
Anastasia V. Mikhaylovskaya, Olga A. Yakovtseva, Natalia Yu. Tabachkova, Terence G. Langdon
Summary: During superplastic deformation of microduplex-structured brasses, strain primarily occurs in the beta-phase through grain boundary sliding and dislocation slip/creep mechanisms. Dynamic recrystallization and twinning transform the initial coarse beta-phase grains into ultrafine grains, and alloying with Al improves superplastic behavior and reduces residual cavitation.
SCRIPTA MATERIALIA
(2022)
Article
Nanoscience & Nanotechnology
Hidetoshi Somekawa, Jangho Yi, Hiromi Takahashi, Takanobu Hiroto, Koichi Tsuchiya
Summary: Experimental studies have revealed that many cavities are formed at grain boundaries and grain boundary triple junctions of fine-grained magnesium specimens during plastic deformation at room temperature, and the size and density of these cavities increase with the progression of deformation. The majority of cavities are controlled by plasticity, and their growth rate is similar to those observed in superplastic magnesium alloys tested at elevated temperatures.
MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING
(2022)
Article
Nanoscience & Nanotechnology
Anand Varma, Aditya Gokhale, Hariharan Krishnaswamy, Dilip K. Banerjee, Jayant Jain
Summary: This study investigates the stress relaxation behavior in pure magnesium during interrupted uniaxial tensile tests, showing non-constancy in total strain and the role of shear dominated deformation like grain boundary sliding. The deformation induced evolution of surface inhomogeneity is studied to quantify the effect of grain boundary sliding, with a proposed stress relaxation model accommodating this behavior.
MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING
(2021)
Article
Mechanics
Dinar Zaripov, Vladislav Ivashchenko, Rustam Mullyadzhanov, Renfu Li, Nikolay Mikheev, Christian J. Kaehler
Summary: In this study, the mechanism of near-wall reverse flow (NWRF) events in turbulent duct flow at a relatively low Reynolds number Re-tau around 200 was investigated using direct numerical simulations and particle image velocimetry. A conceptual model was proposed to explain the formation of NWRF events, suggesting they are caused by intense hairpin vortices at the interface between high- and low-momentum flow regions. The similarity of flow topologies associated with NWRF events at Re-tau around 200 with those at higher Reynolds numbers indicates a generality of the proposed mechanism.
JOURNAL OF FLUID MECHANICS
(2021)
Article
Multidisciplinary Sciences
Asghar Shirani, Yuzhe Li, Osman Levent Eryilmaz, Diana Berman
Summary: The study reveals the anti-wear capability of metal nitride-copper nanocomposite coatings in liquid hydrocarbon environments. The formation of carbon-based protective films at the sliding interface contributes to the significant reduction of wear. Analysis of tribological characteristics under different conditions provides insights into the tribocatalysis mechanism facilitating the formation of zero-wear coatings.
SCIENTIFIC REPORTS
(2021)
Article
Nanoscience & Nanotechnology
Zeinab Savaedi, Hamed Mirzadeh, Rouhollah Mehdinavaz Aghdam, Reza Mahmudi
Summary: Shear punch testing was used to evaluate the superplasticity of a hot rolled fine-grained Mg-3Zn-0.5RE-0.5Zr (ZEK300) alloy. The alloy exhibited regions I, II, and III of deformation behavior typical of superplastic materials, with a grain size of 4.5 μm. In region II, the strain rate sensitivity indices of the ZEK300 alloy were determined to be 0.51, 0.48, and 0.41 at temperatures of 350, 400, and 450 degrees C, respectively. The average activation energy of 87.6 kJ mol-1 suggests that grain boundary sliding (GBS) facilitated by grain boundary diffusion is the dominant deformation mechanism.
MATERIALS SCIENCE AND ENGINEERING A-STRUCTURAL MATERIALS PROPERTIES MICROSTRUCTURE AND PROCESSING
(2023)
Article
Engineering, Mechanical
Andreas Gebhard, Bai Cheng Jim
Summary: This study investigates the behavior of transfer films between polymers and metals through experimental analysis of friction and wear of materials. The results show that the extent and stability of transfer film formation have a significant impact on friction and wear, and mixed fiber/solid lubricant grades can reduce this impact.
Article
Chemistry, Physical
Vikram Rathee, Daniel L. Blair, Jeffrey S. Urbach
Summary: In this study, direct measurements of spatially resolved surface stresses of a dense suspension during large amplitude oscillatory shear in the discontinuous shear thickening regime were reported using boundary stress microscopy. The increase in complex viscosity above a frequency-dependent critical strain was found to be coincident with the appearance of large heterogeneous boundary stresses, indicating the formation of transient solid-like phases on spatial scales larger than the particle size. The critical strain for the appearance of solid-like phases was largely determined by the peak oscillatory stress, which depended on the peak shear rate and the frequency-dependent suspension viscosity. The solid-like phases dissipated and reformed on each cycle, with a spatial pattern that was highly variable at low frequencies but remarkably persistent at the highest frequency measured (omega = 10 rad s(-1)).
Article
Thermodynamics
Rozie Zangeneh
Summary: In this study, the influence of heat transfer on the interaction between a compressible turbulent shear layer and shockwave in a scramjet is investigated. It is found that wall temperature affects reattachment location and shock behavior, with lower wall temperatures resulting in more severe heat transfer. Fluctuating heat flux shows intermittent behavior with scattered spots, and the distribution of Stanton number exhibits strong heat transfer and complex patterns within the interaction.
INTERNATIONAL JOURNAL OF HEAT AND FLUID FLOW
(2021)
Article
Energy & Fuels
Shu Zheng, Yuhong Zhang, Yu Yang, Qiang Lu
Summary: In this study, the effects of nitrogenous bio-fuel on soot and NOx formation during gasoline combustion were investigated. The results showed that an increase in the proportion of pyridine in the bio-fuel led to an increase in NO concentration and different effects on soot formation at different heights.
Article
Geochemistry & Geophysics
J. Ding, F. M. Chester, J. S. Chester, X. Shen, C. Arson
Summary: The operation of fracture, diffusion, and intracrystalline-plastic micromechanisms during semibrittle deformation of rock is directly relevant to understanding mechanical behavior across the brittle-plastic transition in the crust. Experimental results with synthetic salt-rocks suggest coupled operation of micromechanisms leading to a distinct rheology, indicating the need to consider interactions between multiple microscopic processes to accurately describe the mechanical behavior of rocks. The study highlights the importance of water content and deformation rates in influencing mechanical behavior, with chemical reactions along grain boundaries playing a significant role in deformation processes.
JOURNAL OF GEOPHYSICAL RESEARCH-SOLID EARTH
(2021)
Article
Materials Science, Multidisciplinary
Zhuoran Zeng, Mengran Zhou, Peter Lynch, Frederic Mompiou, Qinfen Gu, Mohsen Esmaily, Yuanming Yan, Yao Qiu, Shiwei Xu, Hidetoshi Fujii, Chris Davies, Jian-Feng Nie, Nick Birbilis
Summary: The ductility of extruded polycrystalline pure magnesium with fine grain size is primarily supported by the sliding between grouped grains, grain rotation, and dislocation slip, which postpones the occurrence of localized stress concentration and significantly increases the ductility of pure Mg at room temperature.
Article
Mechanics
Aditi Sengupta, Bhavna Joshi
Summary: This study numerically investigates the coupled Kelvin-Helmholtz Rayleigh-Taylor instability (KHRTI) by solving the compressible Navier-Stokes equations for differentially heated air streams in a three-dimensional box. The role of thermal gradient and reversing air streams on the instability is explored, and the development of the turbulent mixing layer is analyzed. The results show that the KHRTI evolves through a combination of Kelvin-Helmholtz and Rayleigh-Taylor mechanisms, and the transition to turbulent mixing involves the formation of coherent structures.
Article
Engineering, Mechanical
Mikhail Boiko, Andrey Sidashov, Tatiana G. Boiko, Igor Burykin, Igor E. Uflyand
Summary: The study reveals that the interaction between DEHS and the metal surface leads to chemical transformations of molecules and the formation of boundary lubricating films, with unoxidized iron on the friction track accelerating this process.
TRIBOLOGY INTERNATIONAL
(2022)