Abstract
Small crack-initiation-arrest events so called Pop-ins often occur at COD tests for welds and COD values at such Pop-ins are usually very small in comparison with those at. the following final fractures. Present assessment regards Pop-in as a critical event because significance of Pop-ins for actual structures hasn't been made clear. Therefore much effort has been made in materials and welding procedures in order to prevent Pop-ins. It is, however, considered to be too conservative to assess Pop-in as initiation of critical brittle fracture if it.is proved that Pop-in makes no influence on the safety of actual structures. And so it is indispensable to clarify the significance of Pop-ins which occur at COD tests and to establish their safety assessment in actual structures.
