Nil ductility transition temperature

FRACTURE TEST RESULTS Nil Ductility Transition Temperature Tests... 

Standard Method for Conducting Drop-Weight Test to Determine Nil-Ductility Transition Temperature of Ferritic Steels, E-208, 1975 Annual Book of ASTM Standards Part 10, ASTM, Philadelphia, Pennsylvania (1975). 

Evaluation of ferritic steels using nil-ductility transition temperature measurements correlated to fracture resistance ... 

ASTM (2006), Standard Test Method for conducting drop-weight test to determine nil-ductility transition temperature of ferritic steels, E 208-06, American Society for Testing and Materials International, West Conshohocken, PA. 

Nil-ductility transition temperature Fracture toughness Dynamic Tndt Blunt changes to sharp Sharp crack Drop-weight specimen test e.g., ASTM E 208. Uses brittle weld crack starter on test specimen. Propagation test Fracture toughness test of fatigue pre-cracked... 

Evaluation of dynamic fracture characteristics of 9Cr-lMo ferritic steel was carried out for normalised tempered (N T), aged (at 1013 K for 1-2 h) and welded conditions (with PWHT). The drop-weight nil-ductility transition temperatures (Tj ) were 248 K, 248 K and 268 K respectively for N T, aged and welded conditions. Despite the difficulties in crack-profile measurement and the uncertainties in fracture loads due to microstructural variation in HAZ of the drop-weight specimens, the particular procedure developed enabled determination of conservative estimates of at/below T. j. from instrumented drop-weight tests which are... 

Nil Ductility Transition Temperature (NDT) Also known as DBTT (ductile-brittle transition temperature) The temperature above which the material is predominantly ductile and below which it is predominantly brittle. The NDT represents the point at which the fracture energy passes below a predetermined point, i.e. 15 ft-lbs (20 joules) for ordinary steel or 40 ft-lbs (54 joules) for Cr-Mo steels. 

Reactor pressure vessel supports are subject to neutron irradiation at low temperature during plant operation. The neutron flux is lower than that at RPV, but the low irradiation temperature could result in higher embrittlement rate. Some reactor pressure vessel supports were fabricated without special requirements on fracture and radiation resistance. Steel surveillance specimens that had been irradiated in an environment believed to be similar to that in operating reactor cavities exhibited a greater than expected shift (increase) in the nil-ductility-transition temperature. This indicated that there was a potential for excessive embrittlement of reactor vessel supports. Moreover, the RPV supports are in many cases difficult to access or inaccessible for in-service inspection. 

In 1964 a failure occurred near the nil ductility transition temperature of a large heat exchanger, under test by the Foster Wheeler Corporation. As a result of this failure and concerns raised in 1964-1965 by British researchers, the Advisory Committee on Reactor Safeguards issued a November 24, 1965 letter. While acknowledging the low probability of reactor pressure vessel failure, the Advisory Committee on Reactor Safeguards expressed concern for the... 

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