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One of the fundamental aims of fracture mechanics is to define fracture toughness KIC of a material. Hence, the ASTM E399 standard was developed. However according to the standard, large‐sized specimens are required to determine the fracture toughness of low alloy carbon steels. ASTM E1921 standard was developed on the fracture toughness of ferritic steels. In this study, a new method was proposed to determine the fracture toughness of ferritic steels. The purpose of the present paper is to compare the results of the method with the experimental results. Two steels that are used in gas and oil main pipelines were investigated in this study.

Èññëåäóåòñÿ âëèÿíèå ìîðôîëîãèè ñòðóêòóðû ôåððèòà è åãî îáúåìíîãî ñîäåðaeàíèÿ íà ìåõàíè÷åñêèå ñâîéñòâà è âÿçêîñòü ðàçðóøåíèÿ äâóõôàçíûõ ñòàëåé. Äëÿ îïðåäåëåíèÿ çíà÷åíèé âÿçêîñòè ðàçðóøåíèÿ èñïîëüçîâàëè íå ñòàíäàðòíûé, à àëüòåðíàòèâíûé ïîäõîä. Ñòàëè ïîäâåðãàëè ãîìîãåíèçèðóþùåé òåðìîîáðàáîòêå. Ïóòåì ïîëíîãî îòaeèãà èëè çàêàëêè ñòàëåé èç àóñòåíèòíîãî ñîñòîÿíèÿ äî ïðèìåíåíèÿ äîêðèòè÷åñêîãî îòaeèãà â àóñòåíèòíîé îáëàñòè ïîëó÷åíû äâå ðàçëè÷íûå èñõîäíûå ìèêðîñòðóêòóðû. Ïîëó÷åíû äâóõôàçíûå ñòàëè ñ äâóìÿ òèïàìè ìîðôîëîãèè (êðóïíî-è ìåëêîçåðíèñòàÿ) ñ 40-, 20-è 10%-íûì îáúåìíûì ñîäåðaeàíèåì ôåððèòà â çàâèñèìîñòè îò èñõîäíîé ìèêðîñòðóêòóðû. Îòïóùåííûå îáðàçöû ñ 10%-íûì îáúåìíûì ñîäåðaeàíèåì ôåððèòà èìåëè áîëåå âûñîêèå çíà÷åíèÿ âÿçêîñòè ðàçðóøåíèÿ ïî ñðàâíåíèþ ñ òàêîâûìè äðóãèõ îáðàçöîâ èç ýòèõ ñòàëåé.

One of the most important aims of the fracture mechanics is to determine the fracture toughness of a material. Various methods were developed for this purpose and have been still used nowadays. In the J‐integral method that is one of them, providing of a dominant linear elastic condition on the specimen is not required. However, in ferritic steels, the fracture toughness values (KJC) obtained by the J‐integral method show some inconsistencies. Therefore, the ASTM E1921 standard was developed on ferritic steels, which are instabilities in the values of elastic or elastoplastic fracture toughness. In this study, a new method was used to determine the fracture toughness (KIC) of ferritic steels, and it was compared with the standard. Three steels with different mechanical properties and average grain size were investigated in this study.

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