Microtopography for Ductile Fracture Process Characterization - Part 2: Application for CTOA Analysis

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The crack tip opening angle (CTOA) is seeing increased use to characterize fracture in so-called "low constraint" geometries, such as thin sheet aerospace structures and thin-walled pipes. With this increase in application comes a need to more fully understand and measure actual CTOA behavior. CTOA is a measure of the material response during ductile fracture, a "crack tip response function". In some range of crack extension following growth initiation, a constant value of CTOA is often assumed. However, many questions concerning the use of CTOA as a material response-characterizing parameter remain. For example, when is CTOA truly constant? What three-dimensional ... continued below

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Lloyd, Wilson Randolph & McClintock, F. A. February 1, 2003.

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The crack tip opening angle (CTOA) is seeing increased use to characterize fracture in so-called "low constraint" geometries, such as thin sheet aerospace structures and thin-walled pipes. With this increase in application comes a need to more fully understand and measure actual CTOA behavior. CTOA is a measure of the material response during ductile fracture, a "crack tip response function". In some range of crack extension following growth initiation, a constant value of CTOA is often assumed. However, many questions concerning the use of CTOA as a material response-characterizing parameter remain. For example, when is CTOA truly constant? What three-dimensional effects may be involved (even in thin sheet material)? What are the effects of crack tunneling on general CTOA behavior? How do laboratory specimen measurements of CTOA compare to actual structural behavior? Measurements of CTOA on the outer surface of test specimens reveal little about threedimensional effects in the specimen interior, and the actual measurements themselves are frequently difficult. The Idaho National Engineering and Environmental Laboratory (INEEL) use their microtopography system to collect data from the actual fracture surfaces following a test. Analyses of these data provide full three-dimensional CTOA distributions, at any amount of crack extension. The analysis is accomplished using only a single specimen and is performed entirely after the completion of a test. The resultant CTOA distributions allow development of full and effective understanding of CTOA behaviors. This paper presents underlying principles, various sources of measurement error and their corrections, and experimental and analytical verification of CTOA analysis with the microtopography method.

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  • Workshop on the Fundamentals and Application of the Crack Tip Opening Angle (CTOA),Geesthacht, Germany,04/24/2001,04/26/2001

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  • Report No.: INEEL/CON-01-00984
  • Grant Number: DE-AC07-99ID-13727
  • Office of Scientific & Technical Information Report Number: 911074
  • Archival Resource Key: ark:/67531/metadc891287

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  • February 1, 2003

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  • Sept. 22, 2016, 2:13 a.m.

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  • Dec. 12, 2016, 7:59 p.m.

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Lloyd, Wilson Randolph & McClintock, F. A. Microtopography for Ductile Fracture Process Characterization - Part 2: Application for CTOA Analysis, article, February 1, 2003; [Idaho Falls, Idaho]. (digital.library.unt.edu/ark:/67531/metadc891287/: accessed December 16, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.