scholarly journals Non-Linear Signal Analysis Applied to Surface Wear Condition Monitoring in Reciprocating Sliding Testing Machines

2006 ◽  
Vol 13 (4-5) ◽  
pp. 327-341 ◽  
Author(s):  
Francisco Paulo Lépore Neto ◽  
José Daniel Biasoli de Mello ◽  
Marcelo Braga dos Santos
Keyword(s):  
Friction Force ◽  
Signal Analysis ◽  
Testing Machine ◽  
Wear Testing ◽  
Friction Forces ◽  
Prismatic Body ◽  
Linear Path ◽  
Elastic Bodies ◽  
Non Linear ◽  
Linear Signal

When the surfaces of two elastic bodies present relative motions under certain amount of contact pressure the mechanical system can be unstable. Experiments conducted on elastic bodies in contact shown that the dynamic system is self-excited by the non-linear behavior of the friction forces. The main objective of this paper is to estimate the friction force using the vibrations signals, measured on a reciprocating wear testing machine, by the proposed non-linear signal analysis formulation. In the proposed formulation the system global output is the sum of two outputs produced by a linear path associated in parallel with a non-linear path. This last path is a non-linear model that represents the friction force. Since the linear path can be identified by traditional signal analysis, the non-linear function can be evaluated by the global input/output relationships. Validation tests are conducted in a tribological system composed by a sphere in contact with and a prismatic body, which has an imposed harmonic motion. The global output force is simultaneously measured by a piezoelectric and by a piezoresistive load cells. The sphere and prismatic body vibrations are measured by a laser Doppler vibrometer and by an accelerometer respectively. All signals are digitalized at the same time base and the data is transferred to a microcomputer. The non-linear signal analysis technique uses this data to identify the friction force.

Non-Linear Signal Analysis Applied to Surface Wear Condition Monitoring in Reciprocating Sliding Testing Machines

2005 ◽  
Author(s):  
F. P. Le´pore ◽  
J. D. B. De Mello ◽  
M. B. Santos
Keyword(s):  
Signal Analysis ◽  
Testing Machine ◽  
Nonlinear Function ◽  
Wear Testing ◽  
Friction Forces ◽  
Linear Path ◽  
Non Linear ◽  
In Series ◽  
Linear Signal ◽  
Non Linear System

Experiments conducted on elastic bodies under friction forces shown that the dynamical system is self-excited by the non-linear behavior of frictional forces. The main objective of this paper is to study the vibrations signals measured on a reciprocating wear testing machine using non-linear signal analysis formulation. A two input and one output MISO model is proposed to represent the non-linear system dynamics. The global output is the sum of two outputs produced by one linear path associated in parallel with a non-linear path. This last path has a non-linear model that represents the friction force and another linear transfer function connected in series. Since the linear path is identified by traditional signal analysis, the nonlinear function can be evaluated by the global input/output relationships, and can be correlated to wear conditions of the contact surfaces. Validation tests are conducted in a tribological system composed by a sphere in contact with a prismatic body witch has an imposed harmonic motion.

scholarly journals Evaluation of the friction force generated by monocristalyne and policristalyne ceramic brackets in sliding mechanics

2013 ◽  
Vol 18 (1) ◽  
pp. 121-127 ◽  
Author(s):  
Roberta Ferreira Pimentel ◽  
Roberto Sotto Maior Fortes de Oliveira ◽  
Maria das Graças Afonso Miranda Chaves ◽  
Carlos Nelson Elias ◽  
Marco Abdo Gravina
Keyword(s):  
Friction Force ◽  
Artificial Saliva ◽  
Testing Machine ◽  
Friction Coefficients ◽  
Friction Forces ◽  
Maximum Friction ◽  
Steel Wires ◽  
Ceramic Brackets ◽  
Sliding Mechanics

OBJECTIVE: To evaluate and compare "in vitro" the maximum friction force generated by three types of esthetic brackets, two types of polycrystalline conventional ceramic brackets (20/40 and InVu) and one type of sapphire monocrystalline bracket (Radiance) in dry and artificial saliva wet settings. Also, to evaluate the influence exerted by artificial saliva on the friction forces of those brackets. METHODS: Tests were performed in dry and artificial saliva wet setting (Oral Balance) by using an EMIC DL 10000 testing machine, simulating a 2 mm slide of 0.019 x 0.025-in rectangular stainless steel wires over the pre-angulated and pre-torqued (right superior canine, Roth prescription, slot 0.022 x 0.030-in) brackets (n = 18 for each bracket). In order to compare groups in dry and wet settings, the ANOVA was used. For comparisons related to the dry versus wet setting, the student t test was used for each group. RESULTS: The results showed that in the absence of saliva the Radiance monocrystalline brackets showed the highest friction coefficients, followed by the 20/40 and the InVu polycrystalline brackets. In tests with artificial saliva, the Radiance and the 20/40 brackets had statistically similar friction coefficients and both were greater than that presented by the InVu brackets. The artificial saliva did not change the maximum friction force of the Radiance brackets, but, for the others (20/40 and InVu), an increase of friction was observed in its presence. CONCLUSION: The InVu brackets showed, in the absence and in the presence of saliva, the lowest friction coefficient.

New Hypothesis of Friction and Its Application to Design of a Railway Wheelset

1999 ◽  
Vol 121 (4) ◽  
pp. 768-773
Author(s):  
A. Fridberg ◽  
L. Vinnik
Keyword(s):  
Contact Mechanics ◽  
Friction Force ◽  
Normal Load ◽  
Friction Forces ◽  
Railway Wheel ◽  
Elastic Bodies ◽  
Tractive Effort ◽  
Wheel Rolling ◽  
New Hypothesis

A new hypothesis for friction forces between two elastic bodies is proposed. The hypothesis is based on contact mechanics problem. The study concentrates on the problem of a railway wheel rolling on rail under tractive effort and normal load. The effect of friction force in developing adhesion is considered. Based on the proposed hypothesis, new design of a railway wheelset has been developed and tested on Moscow Metro and tramcar.

scholarly journals Influence of Nanoscale Textured Surfaces and Subsurface Defects on Friction Behaviors by Molecular Dynamics Simulation

Nanomaterials ◽  
2019 ◽  
Vol 9 (11) ◽  
pp. 1617 ◽  
Author(s):  
Ruiting Tong ◽  
Zefen Quan ◽  
Yangdong Zhao ◽  
Bin Han ◽  
Geng Liu
Keyword(s):  
Molecular Dynamics ◽  
Molecular Dynamics Simulation ◽  
Friction Force ◽  
Copper Substrate ◽  
Dynamics Simulation ◽  
Textured Surfaces ◽  
Friction Forces ◽  
Subsurface Structures ◽  
Texture Orientation ◽  
Subsurface Defects

In nanomaterials, the surface or the subsurface structures influence the friction behaviors greatly. In this work, nanoscale friction behaviors between a rigid cylinder tip and a single crystal copper substrate are studied by molecular dynamics simulation. Nanoscale textured surfaces are modeled on the surface of the substrate to represent the surface structures, and the spacings between textures are seen as defects on the surface. Nano-defects are prepared at the subsurface of the substrate. The effects of depth, orientation, width and shape of textured surfaces on the average friction forces are investigated, and the influence of subsurface defects in the substrate is also studied. Compared with the smooth surface, textured surfaces can improve friction behaviors effectively. The textured surfaces with a greater depth or smaller width lead to lower friction forces. The surface with 45° texture orientation produces the lowest average friction force among all the orientations. The influence of the shape is slight, and the v-shape shows a lower average friction force. Besides, the subsurface defects in the substrate make the sliding process unstable and the influence of subsurface defects on friction forces is sensitive to their positions.

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