The buckling behavior of rod strings in wellbore is one of the key issues in petroleum engineering. The slender rod strings in vertical wellbore were selected as research objects. Based on the energy method, the critical load formulas of sinusoidal and helical buckling were derived for the string with the bottom of the wellbore pressure. According to the sinusoidal and helical buckling’s geomet...

The aims of this study were to determine and compare frictional resistance obtained by low-friction and conventional elastomeric ligatures in the presence of artificial saliva, and observe whether this variable changed after 21 days. Super Slick® low-friction elastomeric ligatures and conventional ligatures of the brands TP conventional® and Unitek® were placed on standard edgewise maxillary ce...

We develop two new continuum contact models for coupled adhesion and friction, and discuss them in the context of existing models proposed in the literature. Our new models are able to describe sliding friction even under tensile normal forces, which seems reasonable for certain adhesion mechanisms. In contrast, existing continuum models for combined adhesion and friction typically include slid...

The combined effect of the use of carbon fiber and seawater and the molecular structure on the tribological behavior of various polymer materials under natural seawater lubrication was investigated. After the investigation, the wear morphology of the contact surface was observed by a laser scanning confocal microscope, and the texture of the wear scars and tracks were presented in 3D profiles. ...

This paper presents an investigation on mechanism of the inclined 1 cone penetration test (CPT) using the numerical discrete element method (DEM). 2 A series of penetration tests with the penetrometer inclined at different angles 3 (i.e., 0°,15°, 30°, 45° and 60°) were numerically performed under µ=0.0 and 4 µ=0.5, where µ is the frictional coefficient between the penetrometer and the soil. 5 T...

Daytime dry deposition of nitric acid to a conifer forest with a LAI of 5.3 was measured using the relaxed eddy accumulation technique. The observations indicate a mean friction velocity of 0.45m s and a mean dry deposition velocity (vd) of 7.5 cm s , with approximately equal aerodynamic (ra) and non-aerodynamic resistances (rb+rc). Mean ra is 10 sm , while mean rb+rc (derived from the differen...

E. Olejnik, A. Janas, B. Grabowska, M. Kawalec, AGH University of Science and Technology, Faculty of Foundry Engineering, Krakow, Poland Casting technology was applied and research was carried out on two alloys based on the Ni3Al phase with variable carbon content of 0,2 and 1,25 wt. % C, respectively. Resistance to abrasive wear, friction coeffi cient and Vickers microhardness were determined....

A novel set of Al2O3-B2O3-CaO composites were manufactured using a cold press-sintering. The B2O3 content in the was varied from 5 to 20 wt% and 2 CaO added composites. Dry sliding tests conducted against an alumina ball at 10–95% relative humidity. presence in-situ formed aluminum borate composite enhanced micro-hardness wear resistance, whereas humidity-sensitive phase reduced friction. Furth...