The Sliding and Rolling of a Cylinder at the Nano-Scale

2004 ◽  
Author(s):  
O. Taylan Sari ◽  
George G. Adams ◽  
Sinan Mu¨ftu¨
Keyword(s):  
Contact Problem ◽  
Scale Effects ◽  
Cylindrical Body ◽  
Friction Stress ◽  
Two Dimensional ◽  
Nano Scale ◽  
Sliding Motion ◽  
Tangential Forces ◽  
Applied Forces ◽  
The Subject

The behavior of a nano-scale cylindrical body (e.g. a fiber), lying on a substrate and acted upon by a combination of normal and tangential forces, is the subject of this investigation. As the scale decreases to the nano level, adhesion becomes an important issue in this contact problem. Thus this investigation treats the two-dimensional plane strain elastic deformation of both the cylinder and the substrate during a rolling/sliding motion, including the effect of adhesion using the Maugis model. For the initiation of sliding, the Mindlin approach is used, whereas for rolling, the Carter approach is utilized. Each case is modified for nano-scale effects by including the effect of adhesion on the contact area and by using the adhesion theory of friction for the friction stress. Analytical results are given for the normal and tangential loading problems, including the initiation of sliding and rolling in terms of dimensionless quantities representing adhesion, cylinder size, and applied forces.

Nano-Scale Effects in the Sliding and Rolling of a Cylinder on a Substrate

2005 ◽  
Vol 72 (5) ◽  
pp. 633-640 ◽  
Author(s):  
O¨. T. Sari ◽  
G. G. Adams ◽  
S. Mu¨ftu¨
Keyword(s):  
Contact Problem ◽  
Scale Effects ◽  
Cylindrical Body ◽  
Friction Stress ◽  
Two Dimensional ◽  
Nano Scale ◽  
Sliding Motion ◽  
Tangential Forces ◽  
Applied Forces ◽  
The Subject

The behavior of a nano-scale cylindrical body (e.g., a fiber), lying on a substrate and acted upon by a combination of normal and tangential forces, is the subject of this investigation. As the scale decreases to the nano level, adhesion becomes an important issue in this contact problem. Thus, this investigation treats the two-dimensional plane strain elastic deformation of both the cylinder and the substrate during a rolling/sliding motion, including the effect of adhesion using the Maugis model. For the initiation of sliding, the Mindlin approach is used, whereas for rolling, the Carter approach is utilized. Each case is modified for nano-scale effects by including the effect of adhesion on the contact area and by using the adhesion theory of friction for the friction stress. Analytical results are given for the normal and tangential loading problems, including the initiation of sliding and rolling in terms of dimensionless quantities representing adhesion, cylinder size, and applied forces.

Plastic Ploughing of a Sinusoidal Asperity on a Rough Surface

2015 ◽  
Vol 82 (7) ◽  
Author(s):  
H. Song ◽  
R. J. Dikken ◽  
L. Nicola ◽  
E. Van der Giessen
Keyword(s):  
Friction Stress ◽  
Dislocation Dynamics ◽  
Two Dimensional ◽  
Unit Process ◽  
Contact Models ◽  
Self Similar ◽  
Dynamics Simulations ◽  
Micrometer Scale ◽  
Edge Dislocations ◽  
Flat Contact

Part of the friction between two rough surfaces is due to the interlocking between asperities on opposite surfaces. In order for the surfaces to slide relative to each other, these interlocking asperities have to deform plastically. Here, we study the unit process of plastic ploughing of a single micrometer-scale asperity by means of two-dimensional dislocation dynamics simulations. Plastic deformation is described through the generation, motion, and annihilation of edge dislocations inside the asperity as well as in the subsurface. We find that the force required to plough an asperity at different ploughing depths follows a Gaussian distribution. For self-similar asperities, the friction stress is found to increase with the inverse of size. Comparison of the friction stress is made with other two contact models to show that interlocking asperities that are larger than ∼2 μm are easier to shear off plastically than asperities with a flat contact.

Two-dimensional buoyant plumes in a uniform co-flow

2021 ◽  
Vol 932 ◽  
Author(s):  
Gary R. Hunt ◽  
Jamie P. Webb
Keyword(s):  
Theoretical Investigation ◽  
Analytical Solutions ◽  
Richardson Number ◽  
Relative Magnitude ◽  
Dynamical Behaviour ◽  
Finite Width ◽  
Two Dimensional ◽  
Buoyant Plumes ◽  
The Subject ◽  
Flow Case

The behaviour of turbulent, buoyant, planar plumes is fundamentally coupled to the environment within which they develop. The effect of a background stratification directly influences a plumes buoyancy and has been the subject of numerous studies. Conversely, the effect of an ambient co-flow, which directly influences the vertical momentum of a plume, has not previously been the subject of theoretical investigation. The governing conservation equations for the case of a uniform co-flow are derived and the local dynamical behaviour of the plume is shown to be characterised by the scaled source Richardson number and the relative magnitude of the co-flow and plume source velocities. For forced, pure and lazy plume release conditions the co-flow acts to narrow the plume and reduce both the dilution and the asymptotic Richardson number relative to the classic zero co-flow case. Analytical solutions are developed for pure plumes from line sources, and for highly forced and highly lazy releases from sources of finite width in a weak co-flow. Contrary to releases in quiescent surroundings, our solutions show that all classes of release can exhibit plume contraction and the associated necking. For entraining plumes, a dynamical invariance spatially only occurs for pure and forced releases and we derive the co-flow strengths that lead to this invariance.

Nano-scale effects of selective spin-on deposition

2021 ◽  
Author(s):  
Ryan L. Burns ◽  
Yuanyi Zhang ◽  
Colton D'Ambra ◽  
Mark H. Somervell ◽  
Sean Berglund ◽  
...  
Keyword(s):  
Scale Effects ◽  
Nano Scale

Boundary Layers and Skin Friction in High-Speed Flow

1951 ◽  
Vol 55 (485) ◽  
pp. 285-302 ◽  
Author(s):  
A. D. Young
Keyword(s):  
Boundary Layer ◽  
Boundary Layers ◽  
High Speed ◽  
Scale Effects ◽  
Practical Interest ◽  
High Speed Flow ◽  
High Speeds ◽  
Speed Flow ◽  
The Subject ◽  
Small Disturbances

SummaryIn this paper an attempt is made to review present knowledge of the subject of boundary layers at high speeds, without delving too deeply into the theory, and to draw attention to the results of practical interest. The introductory remarks describe broadly the special features of boundary layers in compressible flow, namely the existence of both thermal and velocity layers and their interdependence, the sensitivity of the external flow to the layers, and their inter-action with shock waves. The results of importance arising from the theory of the laminar boundary layer and of its stability to small disturbances are then discussed, followed by a summary of the present inadequate state of knowledge of turbulent boundary layer characteristics. It is noted that progress in the latter must await the production of more experimental data. The paper concludes with a discussion of scale effects and the allied problem of boundary layer—shock wave inter-action.

scholarly journals Nano-Scale Hydroxyapatite: Synthesis, Two-Dimensional Transport Experiments, and Application for Uranium Remediation

2011 ◽  
Vol 2011 ◽  
pp. 1-5 ◽  
Author(s):  
S. R. Kanel ◽  
T. P. Clement ◽  
M. O. Barnett ◽  
M. N. Goltz
Keyword(s):  
Complete Removal ◽  
Saturated Porous Media ◽  
Two Dimensional ◽  
Tracer Transport ◽  
Flow Conditions ◽  
X Ray Diffraction ◽  
Nano Scale ◽  
Groundwater Systems ◽  
Transport Patterns

Synthetic nano-scale hydroxyapatite (NHA) was prepared and characterized using X-ray diffraction (XRD) and scanning electron microscopy (SEM) methods. The XRD data confirmed that the crystalline structure and chemical composition of NHA correspond to Ca5OH(PO4)3. The SEM data confirmed the size of NHA to be less than 50 nm. A two-dimensional physical model packed with saturated porous media was used to study the transport characteristics of NHA under constant flow conditions. The data show that the transport patterns of NHA were almost identical to tracer transport patterns. This result indicates that the NHA material can move with water like a tracer, and its movement was neither retarded nor influenced by any physicochemical interactions and/or density effects. We have also tested the reactivity of NHA with 1 mg/L hexavalent uranium (U(VI)) and found that complete removal of U(VI) is possible using 0.5 g/L NHA at pH 5 to 6. Our results demonstrate that NHA has the potential to be injected as a dilute slurry forin situtreatment of U(VI)-contaminated groundwater systems.

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