scholarly journals Load-dependent surface nanomechanical properties of poly-HEMA hydrogels in aqueous medium

Soft Matter ◽  
2019 ◽  
Vol 15 (38) ◽  
pp. 7704-7714 ◽  
Author(s):  
Gen Li ◽  
Illia Dobryden ◽  
Eric Johansson Salazar-Sandoval ◽  
Mats Johansson ◽  
Per M. Claesson
Keyword(s):  
Aqueous Medium ◽  
Cross Linking ◽  
Slip Effect ◽  
Stick Slip ◽  
Nanomechanical Properties ◽  
Combined Action

The combined action of load and shear results in the formation of a temporary sub-micrometer hill in front of the tip. As the tip pushes against such hills, a pronounced stick-slip effect is observed for the hydrogel with low cross-linking density.

Palladium immobilized on in situ cross-linked chitosan superfine fibers for catalytic application in an aqueous medium

2018 ◽  
Vol 42 (13) ◽  
pp. 11023-11030 ◽  
Author(s):  
Lulu Liang ◽  
Li Nie ◽  
Minjuan Jiang ◽  
Fusheng Bie ◽  
Linjun Shao ◽  
...  
Keyword(s):  
Aqueous Medium ◽  
Itaconic Acid ◽  
Cross Linking ◽  
Catalytic Application ◽  
Chitosan Composite

Chitosan composite superfine fibers with a diameter of 321 ± 99 nm were prepared by electrospinning with PEO as the co-spinning polymer and itaconic acid as the in situ cross-linking agent.

The Effect of Cross-Linking on Nano-Mechanical Properties of Polyamide

2016 ◽  
Vol 699 ◽  
pp. 37-42 ◽  
Author(s):  
Martin Ovsik ◽  
David Manas ◽  
Miroslav Manas ◽  
Michal Stanek ◽  
Martin Reznicek
Keyword(s):  
Mechanical Properties ◽  
Surface Layer ◽  
Material Properties ◽  
Basic Material ◽  
Nanoindentation Test ◽  
Cross Linking ◽  
Indentation Hardness ◽  
Depth Sensing ◽  
Nanomechanical Properties ◽  
Radiation Crosslinking

Radiation crosslinking of polyamidu 6 (PA 6) is a well-recognized modification of improving basic material characteristics. Radiation, which penetrated through specimens and reacted with the cross-linking agent, gradually formed cross-linking (3D net), first in the surface layer and then in the total volume, which resulted in considerable changes in specimen behaviour. This research paper deals with the possible utilization of irradiated PA6. The material already contained a special cross-linking agent TAIC (5 volume %), which should enable subsequent cross-linking by ionizing β – radiation (15, 30 and 45 kGy). The effect of the irradiation on mechanical behavior of the tested PA 6 was investigated. Material properties created by β – radiation are measured by nanoindentation test using the DSI method (Depth Sensing Indentation). Hardness increased with increasing dose of irradiation at everything samples; however results of nanoindentation test shows increasing in nanomechanical properties of surface layer. The highest values of nanomechanical properties were reached radiation dose of 45 kGy, when the nanomechanical values increased by about 95%. These results indicate advantage cross-linking of the improved mechanical properties.

Simulacija i odstranjivanje stick-slip efekta servosistema sprovodnog aparata hidraulične turbine

2021 ◽  
Vol 23 (1) ◽  
pp. 37-41
Author(s):  
Darko Babunski ◽  
◽  
Emil Zaev ◽  
Atanasko Tuneski ◽  
Laze Trajkovski ◽  
...  
Keyword(s):  
Hydraulic Cylinder ◽  
Friction Model ◽  
Slip Effect ◽  
Hydraulic Systems ◽  
Hydraulic Actuator ◽  
Stick Slip ◽  
Hydro Turbine ◽  
Servo Mechanism ◽  
The Mathematical Model ◽  
Slip Phenomenon

Friction is a repeatable and undesirable problem in hydraulic systems where always has to be a tendency for its removal. In this paper, the friction model is presented through which the most accurate results are achieved and the way of friction compensation, approached trough technique presented with the mathematical model of a hydraulic cylinder of a hydro turbine wicket gate controlled by a servomechanism. Mathematical modelling of a servo mechanism and hydraulic actuator, and also the simulation of hydraulic cylinder as a part of a hydro turbine wicket gate hydraulic system where the stick-slip phenomenon is present between the system components that are in contact is presented. Applied results in this paper and the theory behind them precisely demonstrate under what circumstances the stick-slip phenomenon appears in such a system. The stick-slip effect is simulated using Simulink and Hopsan software and the analysis of the results are given in this paper. Removal of the stick-slip effect is presented with the design of a cascade control implemented to control the behaviour of the system and remove the appearance of a jerking motion.

A Novel Trans-Scale Precision Positioning Stage Based on the Stick-Slip Effect

2012 ◽  
Vol 2 (2) ◽  
pp. 1-14 ◽  
Author(s):  
Bowen Zhong ◽  
Liguo Chen ◽  
Zhenhua Wang ◽  
Lining Sun
Keyword(s):  
Friction Model ◽  
Slip Effect ◽  
Precision Positioning ◽  
Stick Slip ◽  
Kinematics Model ◽  
Lugre Friction Model ◽  
Positioning Stage ◽  
Simulation Results ◽  
Relationship Of ◽  
The Relationship

This article focuses on developing a novel trans-scale precision positioning stage based on the stick-slip effect. The stick-slip effect is introduced and the rigid kinematics model of the stick-slip driving is established. The forward and return displacement equations of each step of the stick-slip driving are deduced. The relationship of return displacement and the acceleration produced by friction are obtained according to displacement equations. Combining with LuGre friction model, the flexible dynamics model of the stick-slip driving is established and simulated by using Simulink software. Simulation results show that the backward displacement will reduce with the acceleration of the slider produced by dynamic friction force, the rigid kinematics model is also verified by simulation results which are explained in further detail in the article.

Stick-Slip Behaviour of Seals With Respect to Time Dependent Friction Forces

2004 ◽  
Author(s):  
Markus Lindner ◽  
Matthias Kro¨ger ◽  
Karl Popp ◽  
Manuel Gime´nez
Keyword(s):  
Stability Analysis ◽  
Time Dependent ◽  
Dynamic Friction ◽  
Slip Effect ◽  
Stick Slip ◽  
Friction Forces ◽  
Seal Design

In the present paper dynamic friction processes in seals are investigated. The undesired stick-slip effect of these components under real technical conditions is analyzed. Starting with the basics of stick-slip vibrations the development of an advanced seal design with improved properties is presented that prevents stick-slip. Finally, an optimization based on the extensive but simple stability analysis is shown by an expanded theory of stick-slip simulations.

scholarly journals Study on Optimization of Damping Performance and Damping Temperature Range of Silicone Rubber by Polyborosiloxane Gel

Polymers ◽  
2020 ◽  
Vol 12 (5) ◽  
pp. 1196 ◽  
Author(s):  
Jiang Zhao ◽  
Nan Jiang ◽  
Dongsheng Zhang ◽  
Bobing He ◽  
Xian Chen
Keyword(s):  
Silicone Rubber ◽  
Intermolecular Forces ◽  
Mechanical Analysis ◽  
Covalent Bonding ◽  
Cross Linking ◽  
Damping Properties ◽  
Transfer Energy ◽  
Covalent Bonds ◽  
Combined Action ◽  
Rheological Test

Polyborosiloxane gel (PBS-gel) with shear hardening properties was prepared by cross-linking boric acid and hydroxyl-terminated polydimethylsiloxane through B–O–Si dynamic covalent bonding. The prepared PBS gel was mixed with methyl vinyl silicone rubber (MVQ), and a benzoyl peroxide (BPO) cross-linking agent was added to vulcanize the silicone rubber. At the same time, the gel molecules were co-vulcanizing with MVQ to produce molecular cross-linking. The effects of PBS-gel on the damping properties of silicone rubber were analyzed by dynamic rheological test, Fourier transform infrared spectroscopy and dynamic mechanical analysis. The results demonstrated that the damping performance of MVQ/PBS rubber is greatly improved and the rubber has a tanδ > 0.3 in the range of −25~125 °C. The shear-hardening gel is uniformly dispersed in the system, due to the combined action of covalent bonds and intermolecular forces, which act as an active molecular chain that can efficiently dissipate and transfer energy inside the silicone rubber.

Squeal vibrations, glass sounds, and the stick-slip effect

2010 ◽  
Vol 88 (11) ◽  
pp. 863-876 ◽  
Author(s):  
A. J. Patitsas
Keyword(s):  
Relative Velocity ◽  
Smooth Surface ◽  
Acoustic Emissions ◽  
Water Layer ◽  
Ceramic Plate ◽  
Slip Effect ◽  
Stick Slip ◽  
Shear Modes ◽  
Modes Of Vibration ◽  
Finger Skin

The origin of the squeal acoustic emissions when a chalk is rubbed on a blackboard or better on a ceramic plate, and those when a wet finger is rubbed on a smooth surface, such as a glass surface, is sought in the stick-slip effect between the rubbing surfaces. In the case of the squealing chalk, the stick-slip effect is anchored by shear modes of vibration in about a 0.3 mm thick chalk powder band at the rubbing interface, while in the case of the wet finger on glass, by such modes in a band comprising the finger skin. Furthermore, there are the interfacial bands at the contact areas that result in the decrease of the friction coefficient with relative velocity of slide, i.e., the condition for the stick-slip effect to occur. Such bands are basically composed of the asperities on the surface of the chalk band and of the epidermis ridges and the water layer, respectively.

Multiple Solutions in an Amplitude Limited Jeffcott Rotor Including Rubbing and Stick-Slip Effect

2005 ◽  
Author(s):  
Jan-Olov Aidanpa¨a¨
Keyword(s):  
Bifurcation Diagram ◽  
Contact Stiffness ◽  
Damping Ratio ◽  
Slip Effect ◽  
Chaotic Motions ◽  
Stick Slip ◽  
Diagram Method ◽  
Machine Failure ◽  
Jeffcott Rotor ◽  
Stable Solutions

The non-linear behaviour of rub-impact rotors have been studied in several papers. In such systems rich dynamics have been found together with the coexistence of solutions within some specific parameter ranges. In this paper an attempt is made to find all stable solutions for an amplitude limited Jeffcott rotor including rubbing and stick-slip effect. The recently suggested “multi bifurcation diagram method” is used to find and extract stable sets of bifurcation diagrams. A system is chosen where the linear stationary amplitude only exceeds the clearance in a narrow region near the natural frequency. Therefore large regions in frequency are expected to have only the linear stationary response. The results show that it is only for very low frequencies that one single solution exists. Even though periodic motions are dominant, there exist large ranges in frequency with quasi-periodic or chaotic motions. For the studied cases, three coexisting stable solutions are most common. In one case as many as four stable solutions was found to coexist. For rotors with large clearances (no impacts necessary) it is still possible to find several coexisting motions. For all cases the stick motion is the most severe one with large amplitudes and high backward whirl frequencies. In real situations the consequence of this stick motion is machine failure. These high amplitude motions were found to be stable over large frequency ranges. From the stability analysis it was found that this rolling motion can be avoided by low spin speed, low contact stiffness, low coefficient of friction, small ratio of disc radius/clearance or high damping ratio. In a design situation the parameters are seldom known with high accuracy. Therefore, it is of interest to know all solutions for parameter intervals. The multi-bifurcation diagram can be used in such situations to design a robust machine or at least be prepared for unwanted dynamics.

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