scholarly journals Atomistic potential based cohesive modeling for surface separation

2014 ◽  
Author(s):  
Kegui Xin ◽  
Minghua He
Keyword(s):  
Surface Separation ◽  
Cohesive Modeling

Recent Patents on Abnormal Hydrodynamic Thrust Slider Bearings: Part II-the Second Mode of the Bearings

2020 ◽  
Vol 13 (1) ◽  
pp. 35-40
Author(s):  
Yongbin Zhang ◽  
Huansheng Cheng ◽  
Junyan Wang
Keyword(s):  
Operating Conditions ◽  
Moving Surface ◽  
Friction Coefficients ◽  
Surface Separation ◽  
Slider Bearings ◽  
Stationary Surface ◽  
Boundary Slippage ◽  
Load Carrying ◽  
Second Mode ◽  
Inlet Zone

Background: As a successive part, the paper introduces the second mode of abnormal hydrodynamic thrust slider bearings with divergent surface separations registered in the patents, where the boundary slippage is artificially designed both on the stationary surface in the inlet zone and on the whole moving surface. Objective : To introduce a second method for artificially designing the boundary slippage for the formation of abnormal hydrodynamic thrust slider bearings. Methods: The analytical results are presented for the introduced bearings. The performances of the bearings are demonstrated. Result: : In appropriate operating conditions, the introduced bearings can have considerable loadcarrying capacities with low friction coefficients on the scales 10-3 or 10-4. With the weakening of the boundary slippage on the moving surface, the load-carrying capacities of the bearings are all increased, while the friction coefficients of the bearings are all reduced. Conclusion: When the boundary slippage is present both on the stationary surface in the bearing inlet zone and on the whole moving surface, abnormal hydrodynamic thrust slider bearings can be designed with the surface separation in the bearing inlet zone lower than that in the bearing outlet zone. The performances of these bearings are quite satisfactory.

scholarly journals Selected Aspects of Cohesive Zone Modeling in Fracture Mechanics

Metals ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 302
Author(s):  
Wiktor Wciślik ◽  
Tadeusz Pała
Keyword(s):  
Cohesive Zone ◽  
Mixed Mode ◽  
Review Paper ◽  
Failure Process ◽  
Cohesive Zone Modeling ◽  
Mixed Mode Loading ◽  
Cohesive Models ◽  
Cohesive Modeling ◽  
Zone Modeling ◽  
Intensive Development

This review paper discusses the basic problems related to the use of cohesive models to simulate the initiation and development of failure in various types of engineering issues. The most commonly used cohesive zone models (CZMs) are described. Recent achievements in the field of cohesive modeling are characterized, with particular emphasis on the problem of mixed mode loading, the influence of the strain rate, the stress state triaxiality, and fatigue. A separate chapter of the work is devoted to the identification of cohesive parameters. Examples of the use of CZMs for the analysis of the fracture and failure process in various applications, both on the macro and microscopic scale, are given. The directions of CZMs development were indicated as well as the issues that are currently under particularly intensive development.

scholarly journals A morphological study of plasma and phagosome membranes during endocytosis in Acanthamoeba.

1980 ◽  
Vol 84 (2) ◽  
pp. 246-260 ◽  
Author(s):  
B Bowers
Keyword(s):  
Plasma Membrane ◽  
Morphological Study ◽  
Direct Evidence ◽  
Particle Density ◽  
Early Stage ◽  
Chemical Analyses ◽  
Surface Separation ◽  
Phospholipid Ratio ◽  
Major Route ◽  
Particle Ingestion

Particle ingestion by Acanthamoeba is rapid. Within 40 s bound particles can be surrounded by pseudopods, brought into the cytoplasm, and released as phagosomes into the cytoplasmic stream. In electron micrographs the phagosome appears as a flasklike invagination of the surface. Separation from the surface occurs by fragmentation of the attenuated "neck+ of the invagination. The separated phagosome membrane has a three- to fourfold greater density of intramembrane particles than the plasma membrane from which it derives. This change is evident within 15 min of ingestion and is detectable while the membrane is still tightly apposed to the particle. There is no direct evidence for the mechanism of this increase; no increase in particle density was seen in the membrane at an early stage in the forming phagosomes still connected to the surface. These morphological observations are consistent with chemical analyses, to be reported in a separate communication, that show that the phagosome membrane has a higher protein to phospholipid ratio and a higher glycosphingolipid content than the plasma membrane. Enlarged phagosomes (presumptive phagolysosomes) show multiple small vesiculations of characteristic morphology. The small vesicles are postulated to be the major route of membrane return to the cell surface.

Surface Separation Equilibria and Dynamics of Cationic Dye Loaded onto Citric Acid and Sodium Hydroxide Treated Eggshells

2018 ◽  
Vol 17 (1) ◽  
Author(s):  
Elisha A. Adeniji ◽  
Temitope O. Abodunrin ◽  
Temitope A. Ogunnupebi ◽  
Babatunde A. Koiki ◽  
Abimbola M. Olatunde ◽  
...  
Keyword(s):  
Citric Acid ◽  
Diffusion Mechanism ◽  
Experiment Data ◽  
Surface Separation ◽  
Rate Limiting Step ◽  
Monolayer Adsorption ◽  
Delta G ◽  
Rate Limiting ◽  
Best Fit ◽  
Adsorption Systems

AbstractThis research enthusiastically highlights the bio-adsorption of methylene blue (MB) by local, poultry, NaOH and citric acid modified ubiquitous eggshell (LES, NLES, CLES, PES, NPES and CPES) adsorbents. The microstructures of these adsorbents indicated that they had some surface functional moieties that were responsible for the adsorption of MB. The Langmuir isotherm and PSO model best fit the experiment data. The largest Langmuir monolayer adsorption capacity${q_{max}}$, was 242.47 mg/g, with the largest MB initial concentration of 400 mg/L. This was a clear indication and a confirmation that MB adsorption by the powdered eggshells was chemisorptive. Moreover, the values of$F$, the thickness of the boundary layer/film were$\gt 0$, showing that the rate limiting step for the adsorption process was controlled by more than one diffusion mechanism. The values of$\Delta {G^\circ }$for the adsorption of MB by the adsorbents indicated that the adsorption reactions were all non-feasible and non-spontaneous. The values for$\Delta {S^\circ }$(J/K/mol) for LES, NLES and CPES for the uptake of MB showed decrease in the chaos or degree of randomness of the adsorption reactions, and the reverse was the case for PES, NPES and CLES for the uptake of MB, which showed increase in the chaos or degree of randomness of the adsorption. The adsorption of MB by LES, NLES and CPES gave$\Delta {H^\circ }$(kJ/mol) values which were indicative of endothermic nature of the adsorption systems, and the reverse was the case for the uptake of MB by PES, NPES and CLES, which was indicative of the exothermic nature of the adsorption systems.

scholarly journals The effect of sampling interval on the predictions of an asperity contact model of two-process surfaces

2017 ◽  
Vol 65 (3) ◽  
pp. 391-398 ◽  
Author(s):  
P. Pawlus ◽  
R. Reizer ◽  
M. Wieczorowski ◽  
W. Żelasko
Keyword(s):  
Surface Region ◽  
Sampling Interval ◽  
Plasticity Index ◽  
Contact Model ◽  
Asperity Contact ◽  
Normal Contact ◽  
Method Of Calculation ◽  
Surface Separation ◽  
Sampling Intervals ◽  
Flat Steel

AbstractContact of random machined two-process steel textures with a smooth, flat steel surface is discussed in this paper. Two-process surfaces were machined by vapour blasting followed by lapping. An elastic-plastic contact model was applied, assuming distributed radius of asperities. Calculation procedures allowed the mean surface separation, contact pressure, and area fraction to be computed as functions of sampling intervals. Parameters characterizing the summits important in contact mechanics were calculated for different sampling intervals. Plasticity index of two-process textures was calculated using the modified procedure. It was found that the influence of sampling interval on normal contact depended on the rough surface ability to plastic deformation. The use of a traditional method of calculation overestimated the plasticity index. Peaks from plateau surface region governed contact characteristics of two-process surfaces.

Contact of Rough Surfaces in Ankle Implants Under Combined Normal and Twist Loading

2018 ◽  
Vol 1 (4) ◽  
Author(s):  
Mohammad Hodaei ◽  
Kambiz Farhang
Keyword(s):  
Medical Application ◽  
Roughness Effects ◽  
Implant Surface ◽  
Surface Separation ◽  
Lateral Contact ◽  
Medical Issues ◽  
The Mean ◽  
Scale Roughness ◽  
Approximate Equations ◽  
Comprehensive Study

The medical application of implant replacements to remedy the pain in joints has necessitated a comprehensive study of wear due to contact of implant surfaces. Excessive wear can lead to toxicity and other implant associated medical issues such as patient discomfort and decreased mobility. Since implant wear is the result of contact between surfaces of tibia and talus implant, it is important to establish a model that can address implant surface contact mechanics with roughness effects. In this research, a statistical contact model is developed for the interaction of tibia and talus including normal and lateral contact in which surface roughness effects are included. The model accounts for the elastic–plastic interaction of the implant surface with roughness. For this purpose, tibia and talus implants are considered as macroscopic surfaces containing micron-scale roughness. Approximate equations are obtained that relate the contact force to the mean surface separation explicitly. Closed-form equations are obtained for hysteretic energy loss in implant using the approximate equations. Such a function can serve as a very useful tool for implant designers and manufacturers. Natural frequencies of both adduction-abduction and planter-dorsiflexion rotations are obtained using nonlinear vibration analyses.

Effect of the Leakage Flows and the Upstream Platform Geometry on the Endwall Flows of a Turbine Cascade

2006 ◽  
Author(s):  
E. de la Rosa Blanco ◽  
H. P. Hodson ◽  
R. Vazquez
Keyword(s):  
Mass Flow Rate ◽  
Mass Flow ◽  
Flow Rate ◽  
Separation Bubble ◽  
Tangential Velocity ◽  
Low Pressure ◽  
Leakage Flow ◽  
Backward Facing Step ◽  
Surface Separation ◽  
Pressure Surface

This work describes the effect that the injection of leakage flow from a cavity into the mainstream has on the endwall flows and their interaction with a large pressure surface separation bubble in a low-pressure turbine. The effect of a step in hub diameter ahead of the blade row is also simulated. The blade profile under consideration is a typical design of modern low-pressure turbines. The tests are conducted in a low speed linear cascade. These are complemented by numerical simulations. Two different step geometries are investigated, i.e., a backward-facing step and a forward-facing step. The leakage tangential velocity and the leakage mass flow rate are also modified. It was found that the injection of leakage mass flow gives rise to a strengthening of the endwall flows independently of the leakage mass flow rate and the leakage tangential velocity. The experimental results have shown that below a critical value of the leakage tangential velocity, the net mixed-out endwall losses are not significantly altered by a change in the leakage tangential velocity. For these cases, the effect of the leakage mass flow is confined to the wall, as the inlet endwall boundary layer is pushed further away from the wall by the leakage flow. However, for values of the leakage tangential velocity around 100% of the wheelspeed, there is a large increase in losses due to a stronger interaction between the endwall flows and the leakage mass flow. This gives rise to a change in the endwall flows structure. In all cases, the presence of a forward-facing step produces a strengthening of the endwall flows and an increase of the net mixed-out endwall losses when compared with a backward-facing step. This is because of a strong interaction with the pressure surface separation bubble.

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