Avaliação da ocorrência de fratura inversa em ensaio DWTT em aço de elevada tenacidade

Abstract

The Drop Weight Tear Testing is a common test method for determining a materials ability to arrest a propagating crack. This testing method was developed by Battelle Memorial Institute, and is conducted in accordance with specification API RP 5L3 Recommended Practice for Conducting Drop Weight Tear Testing on Line Pipe. However, modern steels for pipelines with thermomechanical processing, including accelerated cooling, do not exhibit the same behavior to fracture that conventional steels. Invalid DWTT test results in steels with greater toughness are caused by phenomenon of inverse fracture. In the present study, DWTT in full-size and a sub-size specimens were conducted on a high toughness steel, produced with different thermomechanical processing conditions, and the inverse fracture occurring in the hammer-impacted region was evaluated. In a general manner, a correlation between DWTT results and tensile mechanical properties was observed. The tests also show that the geometry of the specimen (full-size or sub-size) has a direct influence on DWTT results.