Effects of Specimen Thickness and Notch Shape on Fracture Modes in the Drop Weight Tear Test of API X70 and X80 Linepipe Steels |
| |
Authors: | Seokmin Hong Sang Yong Shin Sunghak Lee Nack J Kim |
| |
Affiliation: | (1) Center for Advanced Aerospace Materials, Pohang University of Science and Technology, Pohang, 790-784, Republic of Korea;(2) Department of Materials Science and Engineering, Pohang University of Science and Technology, Pohang, 790-784, Republic of Korea;(3) Graduate Institute of Ferrous Technology, Pohang University of Science and Technology, Pohang, 790-784, Republic of Korea; |
| |
Abstract: | This study is concerned with effects of specimen thickness and notch shape on drop weight tear test (DWTT) properties and
fracture modes of API X70 and API X80 low-carbon microalloyed linepipe steels. Detailed fractographic analysis of broken DWTT
specimens showed that the fracture initiated in an initial cleavage mode near the specimen notch and that some delaminations
occurred at the center of the fracture surface. The chevron notch (CN) DWTT specimens had broader initial cleavage areas than
the pressed notch (PN) DWTT specimens. The larger inverse fracture areas (i.e., cleavage areas close the hammer impact side) appeared in the PN DWTT specimens, because their higher fracture initiation
energy at the notch allowed a higher strain hardening in the hammer-impacted region. The number and length of delaminations
were larger in the CN DWTT specimens than in the PN DWTT specimens, and increased with increasing specimen thickness due to
the plane strain condition effect. As the test temperature decreased, the tendency of delaminations increased, but delaminations
were not found when the cleavage fracture prevailed at very low temperatures. The DWTT test results such as upper shelf energy
(USE) and energy transition temperature (ETT) were discussed with relation to microstructures and fracture modes including
initial cleavage fracture, ductile fracture, inverse fracture, and delaminations. |
| |
Keywords: | |
本文献已被 SpringerLink 等数据库收录! |
|