AN EVALUATION FOR BUTT JOINT CRACKING TESTS IN TERMS OF RESTRAINT SEVERITY AND RESTRAINT STRESS

An apparatus for measuring the restraint severity has been set up based on the concept of tensile restraint severity.The restraint severity of butt weld cracking specimens usually used in shipbuilding has been measured.The types of these specimens are the Tekken type,Lehigh type,Straight Slit type with circular holes at the ends,H-type,restraint butt joint and window type,etc.The results show that the restraint coefficient of H-type cracking specimen is highest and that of window type is lowest.At the same time,the measurements of the restraint severity are performed for joints connecting one block of a ship to another.The measurements indicate that at the same slit length there is a good agreement between the restraint severity of the ship structure and that of the Tekken type and restraint butt joint cracking specimens.The restraint stresses of the Tekken type and restraint butt joint cracking specimens are measured by means of the relieving stress electrometrical method.The experimental results indicate also that for a given configuration,the amount of restraint severity is a criterion for predicting the extent of restraint for the structure.In twodimentional stress state,the corresponding relationship between restraint severity and restraint stress for different specimen configurations is not always in existence.