Abstract:Friction hodographs contain all the information related to the intensity and symmetry of the friction phenomenon. We show how an atomic force microscope can be used to collect friction hodographs at the nanoscale and how to carry out data interpretation to unravel the frictionsurface structure relationship. As a model system, we analyzed the basal plane of orthorhombic b-alanine single crystals, and interpreted the data in terms of a constitutive model of orthotropic friction with slip direction-dependent fric… Show more
“…Maintaining the cantilever and surface orientation and changing the sliding direction introduce problems, as perturbations coming from the buckling of the cantilever. This problem has been revisited in a recent work by Campione et al [19], where apparent variations in the elevation produced by buckling were related to the friction component along the cantilever axis and used to determine the so-called hodograph friction of the surface.…”
We present a series of numerical simulations on the friction-anisotropy behavior and stick-slip dynamics of a point mass in the framework of a 2d Prandtl-Tomlinson model. Results for three representative surface lattice are shown: square, hexagonal and honeycomb. Curves for scan angle dependence of static friction force, and kinetic one at T = 0 K and T = 300 K are shown. Friction force maps are computed at different directions.
“…Maintaining the cantilever and surface orientation and changing the sliding direction introduce problems, as perturbations coming from the buckling of the cantilever. This problem has been revisited in a recent work by Campione et al [19], where apparent variations in the elevation produced by buckling were related to the friction component along the cantilever axis and used to determine the so-called hodograph friction of the surface.…”
We present a series of numerical simulations on the friction-anisotropy behavior and stick-slip dynamics of a point mass in the framework of a 2d Prandtl-Tomlinson model. Results for three representative surface lattice are shown: square, hexagonal and honeycomb. Curves for scan angle dependence of static friction force, and kinetic one at T = 0 K and T = 300 K are shown. Friction force maps are computed at different directions.
“…If the needle slides along the principal direction, the friction force is parallel, but with the opposite direction. However, if the needle is not completely in the registry state (for example, misaligned by several degrees), or if the pushing force slightly moves it from the registry state, then an additional force component appears along the direction normal to the registry state 12,71,72 , and this additional force can be responsible for the observed needle movement in the lateral direction (with respect to the direction of the registry state).…”
Section: E Preferential Sliding Directionsmentioning
Two-dimensional (2D) materials are envisaged as ultra-thin solid lubricants for nano-mechanical systems. So far, their frictional properties at the nanoscale have been studied by standard friction force microscopy. However, lateral manipulation of nanoparticles is a more suitable method to study the dependence of friction on the crystallography of two contacting surfaces. Still, such experiments are lacking. In this study, we combine atomic force microscopy (AFM) based lateral manipulation and molecular dynamics simulations in order to investigate the movements of organic needle-like nanocrystallites grown by van der Waals epitaxy on graphene and hexagonal boron nitride. We observe that nanoneedle fragments -when pushed by an AFM tip -do not move along the original pushing directions. Instead, they slide on the 2D materials preferentially along the needles' growth directions, which act as invisible rails along commensurate directions. Further, when the nanocrystallites were rotated by applying a torque with the AFM tip across the preferential sliding directions, we find an increase of the torsional signal of the AFM cantilever. We demonstrate in conjunction with simulations that both, the significant friction anisotropy and preferential sliding directions are determined by the complex epitaxial relation and arise from the commensurate and incommensurate states between the organic nanocrystallites and the 2D materials. arXiv:1810.00756v1 [cond-mat.mes-hall]
“…In these equations parameter a is measurable, it is the length of the largest line from point C to the area's boundary, S is a contact area. Equations (5) in dimensionless form (asterisks are omitted):…”
Section: Equations Of Motionmentioning
confidence: 99%
“…For equation (5) taking into account conditions v = 0, ω = 0 we have that parameter β is zero and from (3) and (4) we achieve system of equations:…”
Anisotropy of friction force is proved to be an important factor in various contact problems. We study dynamical behavior of thin plates with respect to symmetric and asymmetric orthotropic friction. Terminal motion of plates with circular and elliptic contact areas is mainly analyzed. Evaluation of friction forces for both symmetric and asymmetric orthotropic cases are shown. Regular pressure distribution is considered. Differential equations are formulated and solved numerically for a number of initial conditions. Examples show significant influence of friction force asymmetry on the motion.
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