scholarly journals HIGH-FREQUENCY VIBRATIONS IN THE CONTACT OF BRAKE SYSTEMS

2019 ◽  
Vol 17 (2) ◽  
pp. 103 ◽  
Author(s):  
Johannes Otto ◽  
Georg-Peter Ostermeyer
Keyword(s):  
Boundary Layer ◽  
Testing Machine ◽  
Dynamic Contact ◽  
Contact Structures ◽  
Pin On Disc ◽  
The Coefficient Of Friction ◽  
High Frequency Vibrations ◽  
Open Question ◽  
Vibration Signatures ◽  
Dynamics And Vibration

The processes and interactions that occur due to friction in the brake are still not fully understood today. In particular, the processes in the boundary layer have been shown to be responsible for a variation in the coefficient of friction and the associated wear. Dynamic contact structures in the boundary layer are made responsible for this behaviour. Vibration analyses on brake systems usually concentrate on operating vibrations analyses of the brake system components. In order to gain an understanding of the cause of such phenomena and oscillations, it is necessary to understand the mechanism of origin in the contact area. Therefore, highly specialized tribotesters have been developed at the Institute for Dynamics and Vibration to investigate the dynamic processes through experiments and simulative investigations. It can be shown that ultrasonic frequencies are generated in the friction boundary layer. These ultrasonic frequencies could not only be found in pin-on-disc testers, but also in complete vehicle brake systems. It was possible to identify that the vibration signatures between 20 and 80 kHz depend on a whole series of different influencing variables and have no dependence on the testing machine. In connection with the friction theories, it is an open question whether these oscillations can be made responsible as a kind of trigger pulse for the squealing of 1 to 20 kHz. In addition, it is a problem that the parking sensors installed in the vehicle work on an ultrasonic basis in the same frequency range and can therefore lead to failure due to these frequencies.

THE INFLUENCE OF THE ADDITION OF GRAPHITE ON THE TRIBOLOGICAL PROPERTIES OF POLYLACTIC (PLA) APPLIED IN 3D PRINTING TECHNOLOGY

Tribologia ◽  
2018 ◽  
Vol 277 (1) ◽  
pp. 89-93 ◽  
Author(s):  
Wojciech PAWLAK ◽  
Wojciech WIELEBA ◽  
Janusz KLUCZYŃSKI ◽  
Lucjan ŚNIEŻEK
Keyword(s):  
3D Printing ◽  
Tribological Properties ◽  
Testing Machine ◽  
Linear Wear ◽  
Optimal Composition ◽  
Fused Filament Fabrication ◽  
Pin On Disc ◽  
The Coefficient Of Friction ◽  
Steel Disc ◽  
Preliminary Research

The article presents the results of studies on the influence of the addition of graphite to a PLA filament on linear wear and the coefficient of friction. A cylinder of 8 millimetre diameter manufactured in Fused Filament Fabrication process, popularly called 3D printing was used as a specimen. Studies were conducted on pin-on-disc testing machine, in which the cylinders mentioned above were paired with a steel disc – the counter-specimen. Specimens used in research were enriched by 5%, 10%, 20%, and 30% of graphite in comparison to the base filament – Natural PLA, which were not enriched with any additions that could improve its tribological properties. The experiment was conducted as a preliminary research. The gained results create a basis to select the optimal composition of additions to the PLA to create a filament with better tribological properties.

Effect of carbon nanotubes modified with different concentrations of rare earth lanthanum on the mechanical and tribological properties of epoxy composites

2021 ◽  
pp. 002199832098764
Author(s):  
Mingren Jiang ◽  
Xianhua Cheng
Keyword(s):  
Carbon Nanotubes ◽  
Rare Earth ◽  
Polymer Matrix ◽  
Photoelectron Spectroscopy ◽  
Polymer Matrix Composites ◽  
Testing Machine ◽  
Matrix Composites ◽  
Mechanical And Tribological Properties ◽  
The Coefficient Of Friction ◽  
The Rare Earth

Rare earth modified acidified carbon nanotubes were prepared by functionalization of acidified carbon nanotubes with different concentrations of LaCl3. The modification results were characterized by Fourier-transform infrared and X-ray photoelectron spectroscopy. The rare earth successfully increases the surface activity of the acidified carbon nanotubes. Polymer matrix composites were prepared by using the rare earth modified acidified carbon nanotubes as the reinforcement in epoxy matrix. Mechanical properties were analyzed by Zwick Z100 testing machine and the tribological behaviors were test by multifunctional tribological tester. Compared with pure epoxy (epoxy resin), the mechanical strength of the best composite sample was increased by 50–120%, the coefficient of friction was reduced by 19.4% and the wear rate was reduced by approximately 40 times. The experimental results show that the RE concentration of 0.2–0.3 wt% has the most obvious influence on the properties of polymer composites. The mechanism of rare earth reinforcement in polymer matrix is analyzed and suggested.

INFLUENCE OF NITROGEN FLOW RATE ON FRICTION COEFFICIENT AND SURFACE ROUGHNESS OF TiN COATINGS DEPOSITED ON TOOL STEEL USING ARC METHOD

2007 ◽  
Vol 14 (05) ◽  
pp. 1007-1013 ◽  
Author(s):  
ESAH HAMZAH ◽  
ALI OURDJINI ◽  
MUBARAK ALI ◽  
PARVEZ AKHTER ◽  
MOHD RADZI HJ. MOHD TOFF ◽  
...  
Keyword(s):  
Surface Roughness ◽  
Friction Coefficient ◽  
Tool Steel ◽  
Flow Rate ◽  
Physical Vapor Deposition ◽  
Gas Flow ◽  
Cutting Tools ◽  
Gas Flow Rate ◽  
Pin On Disc ◽  
The Coefficient Of Friction

In the present study, the effect of various N 2 gas flow rates on friction coefficient and surface roughness of TiN -coated D2 tool steel was examined by a commercially available cathodic arc physical vapor deposition (CAPVD) technique. A Pin-on-Disc test was carried out to study the Coefficient of friction (COF) versus sliding distance. A surface roughness tester measured the surface roughness parameters. The minimum values for the COF and surface roughness were recorded at a N 2 gas flow rate of 200 sccm. The increase in the COF and surface roughness at a N 2 gas flow rate of 100 sccm was mainly attributed to an increase in both size and number of titanium particles, whereas the increase at 300 sccm was attributed to a larger number of growth defects generated during the coating process. These ideas make it possible to optimize the coating properties as a function of N 2 gas flow rate for specific applications, e.g. cutting tools for automobiles, aircraft, and various mechanical parts.

The Dependence of the Friction Coefficient on the Size and Course of Sliding Speed

2014 ◽  
Vol 693 ◽  
pp. 305-310 ◽  
Author(s):  
Eva Labašová
Keyword(s):  
Friction Coefficient ◽  
Normal Load ◽  
Testing Machine ◽  
Current Component ◽  
Sliding Speed ◽  
Rectangular Shape ◽  
Coefficient Increase ◽  
The Coefficient Of Friction ◽  
Ring Method ◽  
Run Up

The coefficient of friction for the bronze material (CuZn25Al6) with insert graphite beds and other bronze material (CuSn12) are investigated in this paper. Friction coefficient was investigated experimentally by the testing machine Tribotestor`89 which uses the principle of the ring on ring method. The external fixed bushing was exposed to the normal load of the same size in all tests. Process of load was increased from level 50 N to 600 N during run up 300 s, after the run up the appropriate level of load was held. The internal bushing performed a rotational movement with constant sliding speed. The value of sliding speed was changed individually for every sample (v = 0.2 (0.3, 0.4) m.s-1). The forth test had a rectangular shape of sliding speed with direct current component 0.3 m.s-1 and the amplitude 0.1 m.s-1 period 300 s, the whole test took 2100 s. The obtained results reveal that friction coefficient increase with the increase of sliding speed.

Tribological Behaviour of GFR Polymer Composites

2005 ◽  
Author(s):  
J. Quintelier ◽  
P. Samyn ◽  
P. De Baets ◽  
J. Degrieck
Keyword(s):  
Polymer Matrix Composites ◽  
Normal Load ◽  
Thin Polymer Film ◽  
Matrix Composites ◽  
Tribological Behaviour ◽  
Frictional Behavior ◽  
Glass Fiber Reinforced ◽  
Thin Polymer ◽  
Pin On Disc ◽  
The Coefficient Of Friction

On a Pin-on-Disc test rig with composite disc and steel pin tribological experiments were done on pultruded glass fiber reinforced polymer matrix composites plates. The wear and frictional behavior strongly depends on the structure. Also the normal load plays an important role in the frictional behavior, which is of greater importance than the speed. The formation of a thin polymer film onto the wear track results in a lowering of the coefficient of friction with 20%.

scholarly journals Tribological wear of Fe-Al coatings applied by gas detonation spraying

2021 ◽  
Author(s):  
Tomasz Chrostek
Keyword(s):  
Dry Friction ◽  
Shear Stresses ◽  
X Ray Diffraction ◽  
Detonation Spraying ◽  
Gas Detonation ◽  
Compressive Stresses ◽  
Spraying Parameters ◽  
Thin Oxide Films ◽  
Pin On Disc ◽  
The Coefficient Of Friction

Comparative tests of gas detonation (GDS) coatings were carried out in order to investigate the influence of spraying parameters on abrasive wear under dry friction conditions. The tests were carried out using the pin-on-disc (PoD) method at room temperature. The microstructure of the coatings was analysed by X-ray diffraction (XRD) and scanning electron microscopy (SEM / EDS) methods. The results showed that with specific GDS process parameters, the main phases in both coatings were FeAl and Fe3Al involving thin oxide films Al2O3. The tribological tests proved that the coatings sprayed with the shorter barrel of the GDS gun showed higher wear resistance. The coefficient of friction was slightly lower in the case of coatings sprayed with the longer barrel of the GDS gun. During dry friction, oxide layers form on the surface, which act as a solid lubricant. The load applied to the samples during the tests causes shear stresses, thus increasing the wear of the coatings. During friction, the surface of the coatings is subjected to alternating tensile and compressive stresses, which lead to delamination and is the main wear mechanism of the coatings.

Selection of Molybdenum-Filled Hip Implant Material Using Grey Relational Analysis Method

2018 ◽  
pp. 675-692 ◽  
Author(s):  
Amit Aherwar ◽  
Amit Singh ◽  
Amar Patnaik ◽  
Deepak Unune
Keyword(s):  
Grey Relational Analysis ◽  
Testing Machine ◽  
Base Material ◽  
Analysis Method ◽  
Wear Properties ◽  
Hardness Tester ◽  
Relational Analysis ◽  
Implant Material ◽  
Pin On Disc ◽  
Grey Relational

In this study, a series of implant material containing molybdenum of different weight percentages were fabricated via high temperature vertical vacuum casting induction furnace and examined their physical, mechanical and wear properties. The mechanical properties were tested by the micro-hardness tester and the compression testing machine, while the wear performance was analyzed through a pin-on-disc tribometer under different operating conditions at room temperature. Density, hardness, compressive strength and sliding wear were considered as criterions for this study. The proportions of alternatives consist of Co-30Cr as a base material and molybdenum as an alloying element which was varied from 0 to 4wt.%. Due to the conflict between the properties obtained, the Grey relational analysis method (GRA) was applied to choose the best material among the set of alternatives. From the results obtained, it was found that Co-30Cr implant material containing 4wt.%molybdenum provides the best combination of the properties for a given application (i.e. hip femoral head).

Effect of Heat Treatment on the Structure, Wear and Corrosion of AISI L6 Tool Steel

2021 ◽  
Vol 406 ◽  
pp. 448-456
Author(s):  
Oualid Ghelloudj ◽  
Amel Gharbi ◽  
Djamel Zelmati ◽  
Khedidja Bouhamla ◽  
Chems Eddine Ramoul ◽  
...  
Keyword(s):  
Tool Steel ◽  
Tribological Behavior ◽  
Wear Testing ◽  
Wear And Corrosion ◽  
Hardening Treatment ◽  
Pin On Disc ◽  
The Coefficient Of Friction ◽  
Hardened Tool Steel ◽  
Hardness Increase ◽  
Steel Hardening

This work is a contribution in analyzing structure, tribological behavior and corrosion of AISI L6 hardened tool steel. Structural characterization and tribological behavior of steel were investigated using Optical Microscopy (OM), Scanning electron microscopy (SEM), wear testing by friction on a pin-on-disc Tribometer and corrosion by potentiodynamic polarization. Comparing to the as-received steel, hardening has generated a fine martensitic microstructure causing a 1.5 times hardness increase. Hardening has contributed to improvement of wear resistance as the coefficient of friction has decreased from 0.86 to 0.67μ. An increase in corrosion resistance was observed after hardening treatment.

scholarly journals Investigation of Laminar–Turbulent Transition on a Rotating Wind-Turbine Blade of Multimegawatt Class with Thermography and Microphone Array

Energies ◽  
2019 ◽  
Vol 12 (11) ◽  
pp. 2102 ◽  
Author(s):  
Torben Reichstein ◽  
Alois Peter Schaffarczyk ◽  
Christoph Dollinger ◽  
Nicolas Balaresque ◽  
Erich Schülein ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Wind Turbine ◽  
Microphone Array ◽  
Suction Side ◽  
Flow Transition ◽  
Turbulent Transition ◽  
Start Up ◽  
Open Question ◽  
Laminar Turbulent Transition

Knowledge about laminar–turbulent transition on operating multi megawatt wind turbine (WT) blades needs sophisticated equipment like hot films or microphone arrays. Contrarily, thermographic pictures can easily be taken from the ground, and temperature differences indicate different states of the boundary layer. Accuracy, however, is still an open question, so that an aerodynamic glove, known from experimental research on airplanes, was used to classify the boundary-layer state of a 2 megawatt WT blade operating in the northern part of Schleswig-Holstein, Germany. State-of-the-art equipment for measuring static surface pressure was used for monitoring lift distribution. To distinguish the laminar and turbulent parts of the boundary layer (suction side only), 48 microphones were applied together with ground-based thermographic cameras from two teams. Additionally, an optical camera mounted on the hub was used to survey vibrations. During start-up (SU) (from 0 to 9 rpm), extended but irregularly shaped regions of a laminar-boundary layer were observed that had the same extension measured both with microphones and thermography. When an approximately constant rotor rotation (9 rpm corresponding to approximately 6 m/s wind speed) was achieved, flow transition was visible at the expected position of 40% chord length on the rotor blade, which was fouled with dense turbulent wedges, and an almost complete turbulent state on the glove was detected. In all observations, quantitative determination of flow-transition positions from thermography and microphones agreed well within their accuracy of less than 1%.

FRICTIONAL PROPERTIES OF PALM KERNEL ACTIVATED CARBON-EPOXY COMPOSITE UNDER VARIOUS NORMAL LOADS

2015 ◽  
Vol 76 (10) ◽  
Author(s):  
Khai Wei Chua ◽  
Mohd Fadzli Bin Abdollah ◽  
Noor Ayuma Mat Tahir ◽  
Hilmi Amiruddin
Keyword(s):  
Activated Carbon ◽  
Room Temperature ◽  
Epoxy Composite ◽  
Normal Load ◽  
Palm Kernel ◽  
Molding Method ◽  
Frictional Properties ◽  
Pin On Disc ◽  
The Coefficient Of Friction ◽  
Sliding Test

This study investigates the effect of normal load on the frictional properties of palm kernel activated carbon-epoxy (PKAC-E) composite. The PKAC-E composite specimen was fabricated by hot compression molding method. The dry sliding test was performed by using a pin-on-disc tribometer at various normal loads, range from 5 – 100N. The sliding speed and distance were constant. All tests were performed at room temperature. It was found that the coefficient of friction decreases with normal load, though at 60N, friction coefficient increases slightly and remains almost invariant at about 0.04 with normal load. The main conclusion of this study is that PKAC-E composite has a potential for tribological material application but only limited at low normal load under unlubricated conditions.

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