ANALYSIS OF THE PARAMETERS OF DYNAMIC SUPERPLASTICITY THE INDUSTRIAL ALUMINUM ALLOYS

The problem of determining the features of the development of blurred phase transitions observed under conditions of dynamic superplasticity of aluminum alloys is solved using the specific heat capacity function. Within the framework of the developed model representations, the deformation mechanisms characteristic of superplasticity and boundary metastable states are analyzed using the Fokker-Planck equation. Using a macrokinetic model, an explicit expression is obtained for the function that characterizes the mechanism of grain boundary slippage (the “drift " coefficient) that prevails in superplasticity. By integrating the differential equations resulting from the model, the solution of which establishes the type of functions responsible for the implementation of the mechanisms of grain boundary slippage and diffusion processes. It is proposed that the diffusion coefficient is responsible for the accumulation of irreversible deformations outside the velocity range of superplasticity. The function responsible for the effects of grain boundary slippage (the "drift" coefficient) is particularly active towards the middle of the superplasticity velocity interval. It is confirmed that outside the velocity range of superplasticity, there is a redistribution of mass transfer forms, the responsibility for which is assigned to the diffusion coefficient. It is shown that the diffusion function shows a tendency to decrease when approaching the range of superplasticity rates. Metastable states are characterized by the competition of diffusion mechanisms and grain boundary slippage.

Discrepancy in oil film distribution observed in ZEV reciprocating motion

Purpose This study aims to present the discrepancy in oil film distribution in reciprocating motion experimentally with zero entraining velocity (ZEV) on a conventional ball-disk test rig with oil lubrication. Design/methodology/approach Driven independently by two individual servomotors, a steel ball and a sapphire disc move at equal speed but in opposite directions in a triangle wave. The oil film images between the ball and the disc were recorded by a camera. After the experiments, the mid-section film thickness was evaluated by using a dichromatic interference intensity modulation approach. Findings The dimpled oil film in transient condition is shallower than that at steady state with the same load and velocities, and the transient dimple depth decreases with the decrease of time. The increase of the applied load offers a beneficial effect on lubrication. Boundary slippage happens in ZEV reciprocating motion. The slippage at the interface is related to the transient effect and applied load. Originality/value This study reveals the significant difference of the oil film variation in ZEV reciprocating motion, especially the complex boundary slippage at the interface of the oil and the sapphire disc. Peer review The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-01-2020-0021

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

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.

Analytical Study of Roughness on Tilted Pad Thrust Slider Bearing Improved by the Boundary Slippage

Influence of roughness on conventional hydrodynamic lubrication of tilted pad thrust slider bearing is studied. Roughness effect is studied using Christensen stochastic process. To study the effect of roughness, bearing characteristics like load carrying capacity is analyzed.

An Exploration of the Experience of Harm in the Bondage/Discipline/Sadomasochism Community

This study sought to gain insight into the attitudes, beliefs, and values that shape bondage/discipline/sadomasochism (BDSM) activities and to explore the degree and consequences of unintended or non-negotiated harms, including physical, emotional, and sexual violence. A qualitative approach, consisting of 22 semistructured interviews and over 150 hours of observations of BDSM events and activities, was used to develop an in-depth exploration of the lived experiences of participants. Thematic analysis was employed to elucidate the ways in which participants define and in some cases experience harm. Findings suggest that individuals construct rational identities that emphasize safe practices and managing harm; however; there are instances where “boundary slippage” occurs. Implications for understanding the dynamics as well as the potential dangers of “consensual” violence are discussed.

Зернограничное проскальзывание и миграция специальных границ зерен в бикристаллах Al. Атомистическое моделирование

The energy of grain boundary shears is calculated for symmetric grain boundaries (GBs) using ab initio methods and molecular-dynamic modeling in order to elucidate mechanisms that control GB shear-migration coupling in typical symmetric GBs, such as Σ3 (111), Σ5 (012), Σ5 (013) and Σ11 (113) tilt GBs, in Al bicrystal. The energy of generalized grain-boundary stacking faults (GB–SF) is determined, and the preferred directions and the energy barrier are established for grain-boundary slippage. It is shown that the relative slippage of neighboring grains at certain directions of particle shears is accompanied by conservative migration of GB in the direction perpendicular to its plain. The modeling data are comparative to known grain-boundary shear-migration coupling mechanisms in Al.