1. Factors that Affect the Fatigue Life of Rubber: A Literature Survey W. V. Mars* - Cooper Tire & Rubber Co. A. Fatemi - U. of Toledo Paper #6 (the paper can be purchased at www.rubber.org)www.rubber.org ACS Rubber Division Meeting Savannah, Georgia April 29, 2002 *Speaker, wvmars@coopertire.com

2. Overview Part I - “A Literature Survey on Fatigue Analysis Approaches for Rubber”, W. V. Mars, A. Fatemi, Int. J. Fatigue, Vol. 24, No. 9, pp. 949-961, 2002. –Crack Nucleation Approach (S-N style) –Crack Growth Approach (dc/dn = f(T)) Today - Important Factors –Mechanical Load History –Environmental Conditions –Rubber Formulation –Stress-Strain Behavior

3. Parameters for Simple Histories

4. Effect of Minimum Strain Cadwell et al, Ind. Eng. Chem., Anal. Ed., 12, 19 (1940) Filled NR

5. Effects of Max. SERR & R-Ratio 1.E-08 1.E-07 1.E-06 1.E-05 1.E-04 1.E-03 1.E-02 1.E-011.E+001.E+01 Maximum Energy Release Rate, kJ/m 2 Crack Growth Rate, mm/cycle R = 0 R = 0.035 R = 0.061 R = 0.35 R = 0.47 Sub-Threshold Regime Transition Regime Power-Law Regime Unstable Crack Growth Lindley, Int. J. Fracture, 9, 449 (1973) Unfilled NR

6. Effect of Static Period under Strain Roland, Sobiesky, RCT, 62, 683 (1989) Polyisoprene

7. Effect of Load Sequence Sun et al, TSTCA, 28, 196 (2000) ε ε ε ε Cycles

8. Effect of Waveform Hardy et al, RubberChem ‘99, Paper #2, Antwerp, Belgium, (1999) (Both compounds based on BIIR) Compound A Compound B Pulse Sine

9. Effect of Strain Rate Young, RCT, 59, 809 (1986) Unfilled CIIRUnfilled NR

10. Multiaxial Loading UndeformedDeformed H δ max δ min 1 2 Cadwell et al, Ind. Eng. Chem., Anal. Ed., 12, 19 (1940) Applied Loads Crack Loading? Crack Closure? Material property dependence on multiaxial loading? http://www.umi.com/hp/Products/Dissertations.html - “Multiaxial Fatigue of Rubber”, by W. V. Mars, U. of Toledo, 2001

11. CIIRNatural RubberBR Effect of Temperature Young, RCT, 59, 809 (1986)

12. Temperature and T o ? L Plane of Crack Propagation n monomer units crosslink Crack tip - Undeformed State Lake & Thomas, Proc. Roy. Soc. Lon., A, 300, 108 (1967)

13. Effects of Ozone and Oxygen Young, RCT, 59, 809 (1986) CIIRNatural Rubber

14. Electrical Charges? Electro- & tribo- elastic effects cause electric charges to accumulate under cyclic deformation. Metallic grips grounded, then insulated. Effect on fatigue resistance. –Grounded condition gives longer fatigue life –Larger filler loading - larger effect Dogadkin et al, RCT, 33, 970 (1960)

15. Polymer / Filler Effects + Gum Filled with 50 phr N300 carbon black (fine) da / dN Lake & Lindley, Rubber J., 146 (10), 24 (1964) Filled with 50 phr N900 carbon black (coarse)

16. Antidegradants Lake & Lindley, Rubber J., 146 (10), 24 (1964) Air, Gum NR, No AO Vaccum, Gum NR, No AO Air, Gum NR, +AO

17. Proposed Effect of Hysteresis Lake & Thomas, Proc. Roy. Soc. Lon., A, 300, 108 (1967)

18. Strain Crystallization Choi & Roland, RCT, 70, 202 (1997)

19. The Mullins Effect Progressively Increasing Simple Tension, N = 8 time strain Mars, Ph.D. Dissertation, U. Toledo, (2001)

20. T c and Loss Modulus Mullins, Trans. IRI, 35, 213 (1959) Data points are for various butadiene- styrene and butadiene- acrylonitrile co- polymers

21. Summary Mechanical Load History Alternating Load and Maximum Load Minimum Load, Mean Load, R-Ratio Statically Strained Rest Period Load Sequence Multiaxial Loading Frequency / Waveform

22. Summary Environmental Conditions Temperature Ozone Oxygen Electrical Charges?

23. Summary Rubber Formulation Polymer Type Filler Type and Loading Antidegradants Vulcanization

24. Summary Stress-Strain Behavior Strain-Crystallization Mullins Effect Rate-Independent Hysteresis Viscoelasticity

25. Questions and Discussion