presentation at the world tribology conference wtc2013, torino, italy
TRANSCRIPT
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Evaluation and prediction of the effect of load frequency on the wear properties of pre-cracked nylon 66
Authors:
A. Abdelbary, M. N. Abouelwafa, I.M. El Fahham and A. H. Hamdy
Dr. Ahmed Abdelbary
Presented by:
Mechanical Eng. Dept., Faculty of Eng., Alexandria, EGYPT
WE2-FW7- 81
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1. Introduction
2. Experimental Work
3. Results & Discussion
4. Conclusions
ContentsCONTENTS
Microscopic investigation of nylon 66 worn surface showed
a number of transverse vertical cracks, which suggested
that the surface cracks play an important role in SFW [1].
3[1] Y.K. Chen, S.N. Kukureka, C.J. Hooke, M. Rao, Surface topography and wear mechanisms in
polyamide 66 and its composites, J. of Mat. Sci. 35(2000) 1269–1281.
1. INTRODUCTION
In cyclic loading, loading-unloading cycles generate
subsurface stress regions that increase the
tendency to initiate surface and subsurface cracks
[2].
Under cyclic loading, the wear rate was about 30%
larger than under a constant load of the same
magnitude [3].
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[2] J.R. Cooper, D. Dowson, J. Fisher, Macroscopic and microscopic wear mechanisms in UHMWPE, Wear 162-164 (1993) 378–384.
[3] A. Abdelbary, M.N. Abouelwafa, I. El Fahham and A. I. Gomaa, The influence of cyclic loading parameters on the wear of nylon 66, Proc. 8th International Conference on Production Engineering and Control PEDAC (2004) Egypt.
1. INTRODUCTION
5[4] K. Furber, J.R. Atkenson, and D. Dowson, The mechanisms for nylon 66: Paper II, Proc. of the 3rd
Leeds-Lyon Symposium on Tribology, 1976.
Volume loss versus sliding distance for Nylon 66 loaded at 67 N, Ref [4].
A
B
1. INTRODUCTION
Section B wear was introduced
[4] as a third wear regime
characterized by marked
increase (10:30%) in WR and
transverse cracks on the
rubbing surface.
It was suggested that section is
SFW takes place after a number
of cycles to failure proportional
to the sliding distance.
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1. INTRODUCTION
The present study aimes to: Investigate the influence of load frequency on wear of
nylon 66 with a pre-existing defect on its rubbing
surface.
Explore the relation between SFW and section B wear
regime.
Predict WR of the tested polymer using ANN wear
model.
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2. EXPERIMENTAL WORK
The dry wear tests under constant and cyclic loads
were performed using reciprocating tribometer of dual
six-station wear tracks.
Sliding speed: 0.25 m/s
Sliding stroke: 310 mm
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2. EXPERIMENTAL WORK
Tribometer: (1) motor; (2) machine frame; (3) chain drive mechanism; (4) U-beam guide; (5) reciprocating carriage; (6) spring; (7) eccentric cam; (8) dead weights; (9) pin holder.
1700 mm
1100
m
m
1
2
3
4
5
6
79
8
Cyclic load Constant load
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All tests were carried out using Nylon66 sliding on
steel counterface AISI 1050, Ra = 0.2 µm.
The imposed cracks were generated by a sharp razor
applied vertically to the surface of the test specimen.
2.5
mm
Wear pin with imposed
vertical crack
2. EXPERIMENTAL WORK
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2. EXPERIMENTAL WORK
The effect of load frequency on Pre-cracked
polymer:
Cyclic load tests: at two frequencies:
f = 0.25, 1.50 Hz, Fmean= 90 N
Constant load tests: at two loads: F = 90 , 135 N
The influence of surface imperfections:
explored by introducing three parallel cracks on the
polymer rubbing face.
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2. EXPERIMENTAL WORK
Relation between surface cracks and section B
wear:
Tests start using un-cracked pin; subsequently, surface
crack was imposed after 80 km, and tests were run
again for 40 km.
ANN model:
Constructing and training the wear model using the
experimental results.
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3. RESULTS & DISCUSSION
CONSTANT LOAD
Tes
t
F
N
surfac
e
cracks
X
km
WR x10-4
mm3.m-1
1 90 - 110 13.3
2 90 1 80 14.8
3 90 3 80 25.2
4 135 - 90 18.1
5 135 1 90 30.7F Applied force [N]X Sliding distance [km]WR Wear Rate [m m3/m]
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3. RESULTS & DISCUSSION
CYCLIC LOAD
Test
Freq.f
Hz
surfac
e
cracks
X
km
WR x10-
4
mm3.m-1
7 0.25 - 80 13.7
8 0.25 1 80 21.8
9 0.25 3 80 29.7
10 1.50 - 100 15.8
11 1.50 1 80 30.1Fmean= 90 N, Fmin/Fmax = 0.06
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3. RESULTS & DISCUSSION
Effect of frequency
test fHz
cracks RCW
12 0* 1 1.11
13 0* 3 1.89
78 0.25 1 1.59
79 0.25 3 2.17
1011 1.50 1 1.90
* Constant load tests
RCW Relative Change in WR
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3. RESULTS & DISCUSSION
Un-cracked polymer
wear pin surface after 60 km sliding, showing wear grooves parallel to the sliding direction
steel counterface after 20 km sliding, showing transfer film formed
300 µm
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3. RESULTS & DISCUSSION
wear pin surface, test 11 after 20 km sliding, showing trapped wear debris inside the crack mouth
steel counterface after 20 km sliding, showing transfer film formed
Pre-cracked polymer
300 µm
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Optical micrograph of nylon 66 rubbing surface, test 2 after 20 km sliding, showing trapped wear debris, pitting.
Pre-cracked polymer
300 µm
3. RESULTS & DISCUSSION
Sliding direction
1 mm
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wear pin surface of test (3) after 20 km sliding, showing wear pin surface with high density of wear grooves
steel counterface of test (3) after 10 km sliding, showing transfer film formed
Pre-cracked polymer, 3 surface cracks
300 µm
3. RESULTS & DISCUSSION
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Relation between SFW and section B wear
TestX
km
WR A x10-4
mm3.m-1
Xof sec. B
km
WR B x10-4
mm3.m-1
*6 120 12.7 80 14.6
**12 125 25.1 80 27.6
10 to15% increase
Test (6)
3. RESULTS & DISCUSSION
* F= 90 N** Fmean= 90 N, f= 0.25 Hz
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ANN wear model
Hidden layers Output layer
Wear Rate
WR
Input layer
Load (F or Fmean)
Maximum load (Fmax)
Frequency (f)
Cracks (n)
3. RESULTS & DISCUSSION
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ANN wear model
Ref. ANNNeurons Type
Training algorithmI/P Hidden O/P
Z. Zang {9[15105]3 1} tan-sigmoid tan-sigmoid pure-linear LM
A. Lada {7[93 ]2 1} tan-sigmoid tan-sigmoid pure-linear CGB
A. Abdelbary {5[201010]3 1} tan-sigmoid tan-sigmoid pure-linear LM
X. Liu {2[8]1 1} - tan-sigmoid pure-linear LM
Z. Jiang {9[1263]3 1} - - - CGB
A. Helmy {35[85]2 1} tan-sigmoid pure-linear pure-linear LM
Configuration of ANNs adopted from literatures
LM Levenberg-Marquardt algorithm CGB Powell–Beale conjugate Gradient algorithm
3. RESULTS & DISCUSSION
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ANN wear model
Comparison of the prediction quality for various ANNs
configurations
[201010]3
3. RESULTS & DISCUSSION
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ANN wear model
[201010]3
3. RESULTS & DISCUSSION
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3. CONCLUSIONS
1) Transverse crack(s) on the polymer rubbing face
is responsible for significant increase in wear
rate.
2) Frequency of cyclic load has an important role in
wear behaviour of surface cracked polymer.
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3. CONCLUSIONS
4) Performing a single transverse crack during the
steady state wear phase resulted in a
generation of section B wear characterized by a
relatively higher wear rate.
5) Introduction of ANNs is beneficial in predicting
the wear rate of nylon 66.
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Thank You