A discussion on two alternative approaches to CT coupon based K1C determination providing results comparable with ASTM E 399

Iyengar, Parthasarathy; Mardaras, Jon; Soe, Shwe

Abstract

The value of Plane Strain Fracture Toughness of a material calculated in accordance with the ASTM E 399 has been noted to be a specimen size-dependent value. The size-dependency of the same with respect to ductile materials has been an area of debate both for quality testing in production and the best applicable value for new structural design of components. While in case of production quality assessment the primary challenge is the repeatability of complying results for ductile materials, for new design – it is of a representative value for the material. Crack Mouth Opening Displacement (CMOD) and the applied load are traditionally used to calculate K1C from CT specimen by ASTM (2023). A discussion on the comparison of two K1C equivalents is presented here based upon observations with respect to specific Aluminium alloys and their relationship with this established material indicator is explored. Equivalents considered are K1si and round tensile specimen inspired by Sarchamy et al (1996) and Wilson (1997). While K1si is based upon CMOD estimation by assuming a fixed amount of crack extension of 0.5 mm irrespective of tested specimen size, round specimen may be applicable when dimensionally constrained.

• Journal Article Type: Article
• Acceptance Date: Jul 9, 2025
• Online Publication Date: Jul 9, 2025
• Publication Date: 2025
• Deposit Date: Jul 21, 2025
• Publicly Available Date: Jul 22, 2025
• Journal: Procedia Structural Integrity
• Electronic ISSN: 2452-3216
• Publisher: Elsevier
• Peer Reviewed: Peer Reviewed
• Volume: 68
• Pages: 446-452
• DOI: https://doi.org/10.1016/j.prostr.2025.06.080
• Public URL: https://uwe-repository.worktribe.com/output/14706989
• Additional Information: This article is maintained by: Elsevier; Article Title: A discussion on two alternative approaches to CT coupon based K1C determination providing results comparable with ASTM E 399; Journal Title: Procedia Structural Integrity; CrossRef DOI link to publisher maintained version: https://doi.org/10.1016/j.prostr.2025.06.080; Content Type: article; Copyright: © 2025 The Author(s). Published by Elsevier B.V.