A new ASTM International standard will enable fracture toughness testing on defects that are directly analogous to those commonly found in structural applications. ASTM E2899, Test Method for Measurement of Initiation Toughness in Surface Cracks under Tension and Bending, was developed by Subcommittee E08.07 on Fracture Mechanics, part of ASTM International Committee E08 on Fatigue and Fracture.
“The vast majority of naturally occurring cracks are surface cracks, as opposed to through-thickness or edge cracks, as represented in most fracture toughness test standards,” says Douglas Wells, structural materials engineer at NASA’s Marshall Space Flight Center, and an E08 member. “In addition to the realistic crack shape, the application of tensile loading across the crack is more representative of common structural configurations. These factors influence the constraint imposed upon the crack, which in turn can influence the measured fracture toughness.”
According to Wells, ASTM E2899 will be used by entities required to address the defect tolerance of safety-critical structures, including petroleum plants and pipelines, nuclear reactors, aircraft and spacecraft.
“Often there is a desire to test the material behavior using a test specimen that is a close analog to the structure in terms of crack shape, material thickness and loading condition,” says Wells. “ASTM E2899 is designed to provide a test method to perform standardized tests of surface cracks in flat plates in either tension or bending, thus providing a reasonably direct analog to many cases of cracking in structural configurations.”
Interested parties are always welcome to join the E08.07 task group responsible for ASTM E2899. The task group is currently planning a series of interlaboratory analytical and experimental studies to support the precision and bias statements in ASTM E2899.
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ASTM Committee E08 Next Meeting: Nov. 11-14, 2013, November Committee Week, Jacksonville, Fla.
Technical Contact: Douglas N. Wells, NASA-MSFC, Huntsville, Ala., Phone: 256-544-3300; firstname.lastname@example.org
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November 7, 2013