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Bithermal low-cycle fatigue evaluation of automotive exhaust system alloy SS409.

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Title: Bithermal low-cycle fatigue evaluation of automotive exhaust system alloy SS409.
Authors: Lu, G.-Y., Behling, M. B., Halford, G. R.
Source: Fatigue & Fracture of Engineering Materials & Structures. Sep2000, Vol. 23 Issue 9, p787. 8p. 4 Charts, 5 Graphs.
Subjects: Stainless steel fatigue, Metals, Thermomechanical treatment, Fracture mechanics, Strains & stresses (Mechanics)
Abstract: This investigation provides thermomechanical fatigue data for the ferritic stainless steel alloy SS409, used extensively in automotive exhaust system components. The data were generated to assess the total strain version of the strain range partitioning (TS-SRP) method for the design and durability assessment of automotive exhaust systems. The cyclic lifetime and the cyclic stress–strain–temperature–time behaviour for alloy SS409 were measured using bithermal tests with extreme temperatures of 400 and 800 °C. Fatigue lives ranged up to 10 000 cycles with hold-times of 0.33–2.0 min. The bithermal fatigue behaviour was compared to isothermal, strain-controlled fatigue behaviour at both 400 and 800 °C. Thermomechanical cycling was found to have a profound detrimental influence on the fatigue resistance of SS409 compared to isothermal cycling. Supplementary bithermal tests with hold-times ranging from 40 s to 1.5 h were conducted to calibrate the TS-SRP equation for extrapolation to longer lifetimes. The observed thermomechanical (bithermal) fatigue lives correlated well with estimated lives using the TS-SRP equations: 70% of the bithermal fatigue data fall within a factor of 1.2 of calculated life; 85% within a factor of 1.4; and 100% within a factor of 1.8. [ABSTRACT FROM AUTHOR]
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Database: Engineering Source
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Abstract:This investigation provides thermomechanical fatigue data for the ferritic stainless steel alloy SS409, used extensively in automotive exhaust system components. The data were generated to assess the total strain version of the strain range partitioning (TS-SRP) method for the design and durability assessment of automotive exhaust systems. The cyclic lifetime and the cyclic stress–strain–temperature–time behaviour for alloy SS409 were measured using bithermal tests with extreme temperatures of 400 and 800 °C. Fatigue lives ranged up to 10 000 cycles with hold-times of 0.33–2.0 min. The bithermal fatigue behaviour was compared to isothermal, strain-controlled fatigue behaviour at both 400 and 800 °C. Thermomechanical cycling was found to have a profound detrimental influence on the fatigue resistance of SS409 compared to isothermal cycling. Supplementary bithermal tests with hold-times ranging from 40 s to 1.5 h were conducted to calibrate the TS-SRP equation for extrapolation to longer lifetimes. The observed thermomechanical (bithermal) fatigue lives correlated well with estimated lives using the TS-SRP equations: 70% of the bithermal fatigue data fall within a factor of 1.2 of calculated life; 85% within a factor of 1.4; and 100% within a factor of 1.8. [ABSTRACT FROM AUTHOR]
ISSN:8756758X
DOI:10.1046/j.1460-2695.2000.00310.x