effect of temperature on the fatigue behavior polymer gears

1. The Dominant effect of temperature
on the fatigue behaviour of polymer
gears
By: Brij Nandan Tripahti
17MT001599
MET(Mechanical)

2. Content
• Introduction
• Experimental setup
• Experiment at room temp.
• Experiment at controlled temp.
• Discussion on result
• Conclusion
• References

3. INTRODUCTION
• Polymer gears/ plastic gears are replacing
metal gears in many industries like
automotive, medical etc.
• Advantage: Ease of production
: Low manufacturing cost
: Good noise damping capacity
: Chemical Inertness

4. • Disadvantage: Poor mechanical properties
: Low Thermal conductivity
• Polymers are very sensitive to temp.
• Heat generated by: Frictional losses (T as µ )
: Hysteresis losses
• Failure mode: decrease of tooth thickness due to thermal
load and fracture due to mechanical load
• Temp= f{ lubricant, Nano composites, material of driving
and driven gear, gear geometry }

5. Abbreviation and Terminology
• POM : -> Polymer gears (polyacetals/polyoxymethylene)
• SS :-> steel gear (1.2312 DIN 40CrMnMoS8-6)
• POM gear :made by injection moulding
:Involute profile
: Good fatigue behaviour

6. Injection moulding

7. Experimental Setup

8. Arrangement of setup
Lateral Y
positioning
-centre
distance
Transverse X positioning-
adding new gears

9. • The efficiency is calculated based on the
measured input and output Torques and
transmission ratio (1.18)
• BY IR camera, the real time operating temp
can be measured and controlled using a feed
back loop
• Area of temp measurement was 1mm^2
• Torque : 1.0 Nm (26.3MPa), 1.2 Nm (30.7 Mpa) ,
1.4 Nm (34.8 MPa)
Speed:1500 rpm

10. Experimental Setup at room temp. or
uncontrolled temp.
• Fatigue life of
POM gear
against SS gear
as a function of
torque at room
temp. is shown
here

12. The increase in the temperature during the test was
2°,4° and 8° C at 1.0, 1.2, &1.4 Nm of Torque. Just
before failure temp. increased abruptly as shown
•
Avg. root temp values of multiple
measurement as a function of torque at
room temperature
Evolution of temperature in a single
measurement

13. Efficiency and Torque dependency
Avg efficiency values as a function of
Torque at room temp
Evolution of frequency in a single
measurement

14. Effect of Torque on gear failure based
on number of cycles

15. Experiments at well controlled temp.
• In order to investigate the influence of actual
gear root temp on fatigue life and teeth
degradation failure ,POM was meshed at
controlled temp.
• 30° C
• 50° C
• 70° C

16. Root temp of POM gear
while running against SS at
different cycles
a) 1.0 Nm
b) 1.2 Nm
c) 1.4 Nm

17. Combined study of all results

18. Efficiency Vs Temperature
Efficiency decreases with
increasing torque.
This becomes more prominent
as the root temp is increased

19. Efficiency decreases by 3%, 5% and
9% at
a) 30°C
b) 50°C
c) 70°C
respectively as torque increases from
1.0 to 1.4 Nm
At controlled root temp

20. Optical image of worn teeth profiles with increasing number of
cylces at 1.4 Nm and controlled temp a) 30°C ,(b) 50°C , (c) 70°C
Dotted lines show initial shape

21. Conclusion
• Temp at the same load/torque-changes the fatigue life
upto
a) 4 times at 70°C
b) 2 times at 50°C
As compared to 30°C
• Fatigue life= f{ Torque ,Temperature}
• Temp increase also decreases the efficiency (90-97%)
by upto 9% in this work for the highest load (34.8 MPa
root stress at 1.4 Nm) at 70°C

22. Reference
• B.J. Briscoe S.K. Sinha , chapter 1- Tribological
application of polymers and their composites
• A. Abdelary, Wear of polymers and composites
• G.W. Stachowiak, A.W. Batchelor, 16- wear of
non metallic materials, engineering tribology