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City traffic conditions contain frequent starts and stops. Thus, Single-Stage Continuously Variable Transmissions are subject to high loads when operating at high gear ratios, leading to excessive friction that cause slipping and heating of friction elements. This study proposes a microprofile with undulation on the surface of the pulley. A mathematical dependence on the technological quality assurance of the surface layer of the V-belt transmission parts formed during turning is proposed, enabling the prediction of height parameters of undulation depending on the change in the spindle speed, feed, and cutting speed. Estimating the error in the field experiment data and calculating values of the proposed methodology showed that the height parameters of the undulation of pulleys have a relative error of 6.3%. [ABSTRACT FROM AUTHOR]

City traffic conditions contain frequent starts and stops. Thus, Single-Stage Continuously Variable Transmissions are subject to high loads when operating at high gear ratios, leading to excessive friction that cause slipping and heating of friction elements. This study proposes a microprofile with undulation on the surface of the pulley. A mathematical dependence on the technological quality assurance of the surface layer of the V-belt transmission parts formed during turning is proposed, enabling the prediction of height parameters of undulation depending on the change in the spindle speed, feed, and cutting speed. Estimating the error in the field experiment data and calculating values of the proposed methodology showed that the height parameters of the undulation of pulleys have a relative error of 6.3%.

Indentation size effect (ISE), in general, is observed in shallow indentation tests, which is manifested as an increase (NISE) or decrease (RISE) in hardness with penetration depth decreases. The complicated origin of ISE is dependent on multiple factors, which can be divided into two types, both strain gradient and external factors. It's very difficult to judge which factor is the source for a certain ISE phenomenon. Further, studies on ISE phenomena under the joint of multiple factors are fewer. To date, the classical Nix-Gao model based on strain gradient has been widely recognized, but it's sometimes not suited for all ISE. And most current analytical models on ISE are not yet mature. Therefore, more mechanistic models on ISE are required, especially for RISE. Herein, we critically reviewed several mechanistic models on ISE, focusing on the exploration of RISE, and developed an analytical model incorporating external factors, i.e. surface undulation and indenter tip irregularity, to account for NISE and RISE. We examined the two external factors on the origin responsible for ISE in light of 3D numerical simulations and experimental observations, meanwhile, the combined effect of both factors on ISE was also considered. The effect of both external factors on ISE can be equivalent to a depth deviation δ. The corresponding hardness deviation caused by δ can be theoretically eliminated through correcting the depth deviation. More importantly, only after eliminating the effect of external factors on ISE, one can determine whether the ISE results from strain gradient plasticity. Finally, this paper was summarized and outlooked.

Surface undulation was formed while growing InGaN/GaN multi-quantum wells on a semi-polar m-plane (1–100) sapphire substrate. Two distinct facets, parallel to 11 2 ¯ 2 and 01 1 ¯ 1 , were formed in the embedded multi-quantum wells (MQWs). The structural and luminescence characteristics of the two facets were investigated using transmission electron microscopy equipped with cathodoluminescence. Those well-defined quantum wells, parallel and slanted to the growth plane, showed distinct differences in indium incorporation from both the X-ray yield and the contrast difference in annular darkfield images. Quantitative measurements of concentration in 01 1 ¯ 1 MQWs show an approximately 4 at% higher indium incorporation compared to the corresponding 11 2 ¯ 2 when the MQWs were formed under the same growth condition. [ABSTRACT FROM AUTHOR]

Flow around a traveling wave-based surface-undulating NACA0012 hydrofoil has been numerically studied. In particular, we determine the effect of the phase speed of the wave, the phase difference between the waves traveling on the top and bottom surfaces, and the wave number on flow dynamics around and behind the hydrofoil and propulsive performance. The flow results in a vortex sheet or a street behind the hydrofoil, where oppositely signed vortices are aligned in either forward or reverse direction. Apart from these, side vortices start forming on either side of the hydrofoil at a higher wave number. The phase difference analysis between the upper and lower surface undulation reveals the configuration better for the hydrofoil's lateral and longitudinal stability. The hydrofoil can shift from high thrust to high lateral force configuration by changing the phase difference between waves on the top and bottom surfaces. Thrust increases with an increase in the wave number, and a threshold value of phase speed and wave number exists where the drag-to-thrust transition happens. The added mass force-based scaling analysis corroborates with the simulated results. [ABSTRACT FROM AUTHOR]

Surface undulation was formed while growing InGaN/GaN multi-quantum wells on a semi-polar m-plane (1–100) sapphire substrate. Two distinct facets, parallel to 112¯2 and 011¯1, were formed in the embedded multi-quantum wells (MQWs). The structural and luminescence characteristics of the two facets were investigated using transmission electron microscopy equipped with cathodoluminescence. Those well-defined quantum wells, parallel and slanted to the growth plane, showed distinct differences in indium incorporation from both the X-ray yield and the contrast difference in annular darkfield images. Quantitative measurements of concentration in 011¯1 MQWs show an approximately 4 at% higher indium incorporation compared to the corresponding 112¯2 when the MQWs were formed under the same growth condition.

The factors responsible for periodic machining errors are analyzed, and corresponding mathematical models are proposed. Approaches to decreasing the periodic machining errors in machine tools are suggested. [ABSTRACT FROM AUTHOR]

The saponin escin, extracted from horse chestnut seeds, forms adsorption layers with high viscoelasticity and low gas permeability. Upon deformation, escin adsorption layers often feature surface wrinkles with characteristic wavelength. In previous studies, we investigated the origin of this behavior and found that the substantial surface elasticity of escin layers may be related to a specific combination of short-, medium-, and long-range attractive forces, leading to tight molecular packing in the layers. In the current study, we performed atomistic molecular dynamics simulations of 441 escin molecules in a dense adsorption layer with an area per molecule of 0.49 nm2. We found that the surfactant molecules are less submerged in water and adopt a more upright position when compared to the characteristics determined in our previous simulations with much smaller molecular models. The number of neighbouring molecules and their local orientation, however, remain similar in the different-size models. To maintain their preferred mutual orientation, the escin molecules segregate into well-ordered domains and spontaneously form wrinkled layers. The same specific interactions (H-bonds, dipole–dipole attraction, and intermediate strong attraction) define the complex internal structure and the undulations of the layers. The analysis of the layer properties reveals a characteristic wrinkle wavelength related to the surface lateral dimensions, in qualitative agreement with the phenomenological description of thin elastic sheets.

Errors in machining and the relation between the final surface roughness and the vibration of the machining system (the lathe, the attachment, the tool, and the workpiece) are considered, for the case of turning. Software for visualization of surface roughness produced by machining is developed. [ABSTRACT FROM AUTHOR]

Humans can perceive a wide and small surface undulation that is hundreds micrometers in height and hundreds millimeters in width by scanning the surface with their whole fingers and palm in the distal and proximal directions. We developed a wearable haptic device that presents a surface undulation to the hand. The device is composed of nine independent stimulator units that control the heights of nine finger pads of the index finger, the middle finger, and the ring finger (three units on each finger) according to the virtual surface. Three experiments are carried out to evaluate the haptic perception by the haptic device. A first experiment shows that the perceived dimensions are diminished as compared to the dimensions applied by the haptic device. On the basis of this result, the applied dimensions are calibrated to match the virtual surface undulation to the real surface undulation. A second experiment shows that the shape of gently-curved surfaces can be estimated with the haptic display. A third experiment shows that the discrimination threshold is not different between the virtual surface undulation and the real surface undulation. These experimental results show the applicability of the haptic device as a haptic interface. [ABSTRACT FROM AUTHOR]

The wetting and adhesion properties of undulated a-C:H surfaces were investigated. The nano-undulated a-C:H films were prepared by radio frequency plasma enhanced chemical vapor deposition (r.f. PECVD) using nanoscale Cu dots surface on a Si (100) substrate. FE-SEM and AFM analysis showed that the surface had nanoscale undulations. Raman spectra of film showed that the plasma induced damage with Ar ions significantly suppressed the graphitization of a-C:H structure. Also, it was observed that the untreated flat a-C:H surfaces had a water wetting angle of 72° and adhesion force of 333 nN. After the treatment for the undulated a-C:H surfaces whose surface morphologies change to an array of pillar asperities, its wetting angle of water increased up to 104° and adhesion force decreased down to 11 nN. These results agree with the estimation of real area of contact on the basis of Hertz and JKR adhesion models. The effect of the surface undulation treatment was discussed with the following factors: the surface morphology affinity to pillar shape, a reduction of the real area of contact and air pockets trapped in pillar double asperities of the surface.

A method is proposed for assessing the influence of dynamic processes in the elastic metal-cutting machine on the resulting surface undulation and roughness. Algorithms for successive parameter calculation are outlined. [ABSTRACT FROM AUTHOR]

The saponin escin, extracted from horse chestnut seeds, forms adsorption layers with high viscoelasticity and low gas permeability. Upon deformation, escin adsorption layers often feature surface wrinkles with characteristic wavelength. In previous studies, we investigated the origin of this behavior and found that the substantial surface elasticity of escin layers may be related to a specific combination of short-, medium-, and long-range attractive forces, leading to tight molecular packing in the layers. In the current study, we performed atomistic molecular dynamics simulations of 441 escin molecules in a dense adsorption layer with an area per molecule of 0.49 nm2. We found that the surfactant molecules are less submerged in water and adopt a more upright position when compared to the characteristics determined in our previous simulations with much smaller molecular models. The number of neighbouring molecules and their local orientation, however, remain similar in the different-size models. To maintain their preferred mutual orientation, the escin molecules segregate into well-ordered domains and spontaneously form wrinkled layers. The same specific interactions (H-bonds, dipole–dipole attraction, and intermediate strong attraction) define the complex internal structure and the undulations of the layers. The analysis of the layer properties reveals a characteristic wrinkle wavelength related to the surface lateral dimensions, in qualitative agreement with the phenomenological description of thin elastic sheets. [ABSTRACT FROM AUTHOR]

The degree of strain relaxation via a formation of misfit dislocation has been calculated in single Si1-xGex/Si (001) epilayers grown at 640°C, by gas-source molecular beam epitaxy. The scale of strain relief via misfit dislocation was below 22% for Ge content x≤0.15. However, in the case of growth temperature of 550°C. the degree of strain relaxation in 270 nra single epilayer structures was 9% via misfit dislocation formation with negligible relaxation by surface undulation. As growth temperature decreased from 640°C to 550°C with higher Ge content (x=0.22), the mode of strain relaxation appears to have changed from one of misfit dislocation and surface undulation mechanism to that of predominant misfit dislocation formation. [ABSTRACT FROM AUTHOR]