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Title: J-R Curve Determination for Disk-shaped Compact Specimens Based on the Normalization Method and Direct Current Potential Drop Technique

Material ductile fracture toughness can be described by J-integral versus crack extension relationship (J-R curve). As a conventional J-R curve measurement method, unloading compliance (UC) becomes impractical in elevated temperature testing due to relaxation of the material and a friction induced back-up shape of the J-R curve. In addition, the UC method may underpredict the crack extension for standard disk-shaped compact (DC(T)) specimens. In order to address these issues, the normalization method and direct current potential drop (DCPD) technique were applied for determining J-R curves at 24 C and 500 C for 0.18T DC(T) specimens made from type 316L stainless steel. For comparison purchase, the UC method was also applied in 24 C tests. The normalization method was able to yield valid J-R curves in all tests. The J-R curves from the DCPD technique need adjustment to account for the potential drop induced by plastic deformation, crack blunting, etc. and after applying a newly-developed DCPD adjustment procedure, the post-adjusted DCPD J-R curves essentially matched J-R curves from the normalization method. In contrast, the UC method underpredicted the crack extension in all tests resulting in substantial deviation in the derived J-R curves manifested by high Jq values than the normalization ormore » DCPD method. Only for tests where the UC method underpredicted the crack extension by a very small value, J-R curves determined by the UC method were similar to those determined by the normalization or DCPD method.« less
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  1. ORNL
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Resource Relation:
Conference: ASTM Sixth International Symposium on Small Specimen Test Techniques, Houston, TX, USA, 20140129, 20140131
Research Org:
Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)
Sponsoring Org:
ORNL work for others; USDOE Office of Science (SC)
Country of Publication:
United States
Fracture Toughness; J-R curve; Elastic Unloading Compliance; Normalization; DCPD