ISSN:
1573-2673
Source:
Springer Online Journal Archives 1860-2000
Topics:
Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
Notes:
Abstract Effect of tensile overload on elevated temperature crack growth behavior during the subsequent load hold period has been studied by numerical and experimental methods. Finite element analysis of compact specimens shows that when the tensile overload precedes the load hold period, C t during the hold period is significantly smaller (i.e. retarded) compared to the case without the overload. This is due to crack tip stress relaxation associated with large crack tip plasticity generated by the overload. A modified C t estimation scheme is proposed by introducing a new equation for t pl. Using this scheme, the retardation behavior of C t due to the overload is successfully modeled. Creep-fatigue crack growth data for an ex-service 1.25Cr-0.5Mo steel at 538°C (1000°F) were generated in air. The hold times are 10 seconds, 98 seconds and 10 minutes. Time-dependent crack growth rate during the load hold period, (da/dt)avg, is correlated with (C t )avg estimated by the new estimation scheme. (da/dt)avg data from all the tests with overload are higher than those from the tests without overload. The peak stress associated with the overload seems to have enhanced void nucleation and to incrase the time-dependent crack growth rate due to creep. This argument is supported by microscopic observations.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF00012361
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