Development of Crack Arrest Temperature Test Method by Using a Local Temperature Gradient

Abstract

This study evaluated the brittle Crack Arrest Temperature (CAT) through an isothermal crack arrest test. Generally, the embrittled zone is required in a CAT test. According to conventional studies, the test method consists of arresting a double tension–type brittle crack with an Electron Beam melt-run, which acts as a crack initiator and crack runway. However, conventional CAT test methods have disadvantages in that they need additional processes to create an embrittled zone with Electron Beam Welding (EBW). A Local Temperature Gradient (LTG) system is developed to overcome the limitations of the conventional EBW embrittlement CAT test method. LTG systems do not require additional EBW to develop a brittle zone to initiate a brittle crack. In a LTG system, the LTG method is proposed instead of EBW to create the embrittled zone. The LTG system is free of flaws. In EBW, it is impossible to perform accurate CAT tests because the presence of defects affects the brittle crack arrest. In this study, a new CAT test method is introduced to evaluate brittle CATs more easily. Furthermore, both test methods were compared for the same specimens to verify the validity of the test method.

Brittle Crack Arrest Temperature Estimation Method Utilizing a Small-Scale Test with a Thick Steel Plate for Shipbuilding

“…where σg (P/Bt) is the applied gross stress (N/mm 2 ), P is the applied load (N), B is the specimen width (mm), and t is the specimen thickness (mm). temperature gradient conditions [27,28]. For CAT evaluation, an experiment was performed by facilitating the occurrence of brittle cracks by randomly developing a brittle area with electron beam welding (EBW) and local temperature gradient (LTG).…”

“…( Brittle crack arrest toughness can be secured by evaluating 𝐾 and CAT. Large-scale ESSO tests of brittle crack arrest toughness have recently been widely conducted under temperature gradient conditions [27,28]. For CAT evaluation, an experiment was performed by facilitating the occurrence of brittle cracks by randomly developing a brittle area with electron beam welding (EBW) and local temperature gradient (LTG).…”

“…Previously, research was conducted to predict CAT through smallscale NRL experiments [5,14,27]. Wisener derived a formula for predicting CAT, considering the influence of the thickness and strength of the applied steel [5,28,29]. Because applying the formula to the latest steel is difficult, a novel prediction formula is required [14].…”