%0 Journal Article %T Torsional Fatigue Life Estimation for Steel Thin-Wall Specimens Considering Crack Initiation Phase %J International Journal of Iron & Steel Society of Iran %I Iron & Steel Society of Iran %Z 2981-0388 %A Ebrahimi, Zohreh %D 2022 %\ 01/21/2022 %V 19 %N 1 %P 30-37 %! Torsional Fatigue Life Estimation for Steel Thin-Wall Specimens Considering Crack Initiation Phase %K Steel thin-wall specimen %K Initial crack length %K ؛ Torsional load %K Critical plane approach %R 10.22034/ijissi.2022.551006.1224 %X An improved model for fatigue life evaluation of a steel thin-wall tubular specimen based on critical plane theory is presented. This new fatigue model incorporates the crack initiation phase in the life prediction model. The total fatigue life is a combination of both crack initiation and crack propagation lives. The initial crack length is not applied priory, but is calculated within the model. The crack initiation life is evaluated using a critical plane approach base on a modified Smith-Watson-Topper and the Fatemi-Socie criteria. The fatigue lives obtained from the proposed model are validated by experimental results for a thin-wall tubular specimen. Both critical plane criteria gave similar fatigue lives, with the Fatemi-Socie criteria giving a slightly more accurate initiation life. Without consideration of the crack initiation phase, the model absolute error is high. The proposed model indicates that a correct determination of the fatigue life requires consideration of the crack initiation phase. %U https://journal.issiran.com/article_697469_b8e62c168a4f7dcf07e8849428f2849a.pdf