Volume 3, Issue 7 (July 2006)
Elasto-Viscoplastic Behavior of the Ferritic Stainless Steel AISI 441-EN 1.4509 from Room Temperature to 850°C
In order to predict the thermomechanical fatigue (TMF) damage of stainless steel parts submitted to thermal loading, the elasto-viscoplastic behavior has to be described accurately in a wide range of temperature, strain, and strain rate levels. The study is done on a stabilized ferritic stainless steel grade equivalent to AISI 441 or EN 1.4509 standard which is used more and more in high temperature application up to 950°C, for example, in exhaust manifolds, heat exchanger, burners, or water-boiler device. The elasto-viscoplastic model proposed by Chaboche is chosen and identified on the basis of isothermal cyclic tests including relaxation and graduated cyclic strain tests performed under air at 300, 650 and 850°C. The validation procedure was performed afterward by comparison with stabilized behavior under nonisothermal conditions, especially in-phase, out-of-phase, and diamond TMF cycles. Results of simulation show very good fitting with the experimental curves which would lead to a more accurate fatigue life prediction.