PSI - Issue 13

Yuki Nishizono et al. / Procedia Structural Integrity 13 (2018) 1817–1827 —‹ ‹•Š‹œ‘‘ Ȁ –”—…–—”ƒŽ –‡‰”‹–› ”‘…‡†‹ƒ ͲͲ ሺʹͲͳͺሻ ͲͲͲ – ͲͲͲ

ʹ

1818

Nomenclature ca

0 0 k TS EL y p ̅̅̅ p ̅̅̅ . n C 0 B W d T P

arrest toughness material constant material constant

temperature at crack arrested point yield stress at room temperature tensile strength at room temperature

elongation

vTrs

surface transition temperature von Mises equivalent stress

yield stress

equivalent strain

equivalent strain rate material constant

equivalent strain when strain hardening starts

strain hardening exponent material constant material constant fracture initiated load arrested crack length thickness of specimen width of specimen span of three-point bending crack length

S ca−PB [ d ] critical

arrest toughness evaluated by the press-notched bend test

dynamic stress intensity factor

test temperature

dynamic stress intensity factor when a crack is arrested

1. Introduction

Investigation of brittle crack propagation behavior in steel is becoming more important for improving reliability of social infrastructure and applying appropriate materials to many kinds of structural components. In particular, there is a significant trend for steel plates used to increase in thickness accompanied by upsizing tanks and ships. The priority items in the safety evaluation of steel structural components generally include an ability to arrest crack propagation, which is necessary to prevent a catastrophic failure even if a brittle fracture occurs. The “double integrity” concept of brittle crack initiation control and arrest has been considered to be an effective and rational methodology for several decades. The wide plate tensile test such as ESSO test is one of the major methods for evaluating brittle crack arrest toughness of steel plates (Nippon Kaiji Kyokai, 2009). Although ESSO test makes it possible to accurately evaluate arrest toughness which indicates the Arrhenius type temperature dependence (Eq. 1), it is not suitable for quality assurance test at mass production of steel plates due to its high economical cost and long lead-time. ca = 0 ∙ (− 0 k ) (1) In response to such industry needs, attempts have been made to replace the wide plate tensile test with small-scale tests for many years. In particular, much effort has been made on the evaluation methods not based on fracture mechanics, such as Charpy impact test and NRL Drop-Weight test (Okawa et al., 2015). Although these methods have a great advantage in terms of their simplicity and cost, they only give us a relative indicator of fracture properties (Ishikawa et al., 1991) (The Japan Welding Engineering Society, 1995). On the other hand, the evaluation methods based on fracture mechanics, e.g. CCA test, also have had many problems such as the inability to evaluate ca in high