Location

Snowbird, UT, USA

Start Date

1-1-1999 12:00 AM

Description

Fatigue crack growth can be strongly influenced by crack closure, i. e., the contacting of the opposing faces of a fatigue crack above the minimum load in a loading cycle. This crack closure shields the crack tip from the full stress field, but different views are held regarding the extent of this shielding. The type of closure, whether it be plasticity-induced, or roughness-induced may also play a role. According to Elber, who considered plasticity-induced closure, the crack is effectively closed as soon as the first detectable closure is developed in the wake of the crack tip. However, Otto Buck and his colleagues, who used ultrasonic waves to investigate crack closure, have been in the forefront of those who claim that the crack tip continues to close even after the first closure contacts have been made, thereby leading to a lesser degree of shielding than in Elber’s view. The purpose of the present paper is to review the extensive work in the area highlighting the ultrasonic approaches as well as the current state of the art concerning crack closure, and to discuss the various views concerning the extent of shielding provided by crack closure.

Book Title

Review of Progress in Quantitative Nondestructive Evaluation

Volume

18B

Chapter

Chapter 6: Materials Characterization

Section

Otto Buck Memorial/Materials Characterization

Pages

1651-1656

DOI

10.1007/978-1-4615-4791-4_211

Language

en

File Format

application/pdf

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Jan 1st, 12:00 AM

On Crack Closure and Crack Tip Shielding During Fatigue Crack Growth

Snowbird, UT, USA

Fatigue crack growth can be strongly influenced by crack closure, i. e., the contacting of the opposing faces of a fatigue crack above the minimum load in a loading cycle. This crack closure shields the crack tip from the full stress field, but different views are held regarding the extent of this shielding. The type of closure, whether it be plasticity-induced, or roughness-induced may also play a role. According to Elber, who considered plasticity-induced closure, the crack is effectively closed as soon as the first detectable closure is developed in the wake of the crack tip. However, Otto Buck and his colleagues, who used ultrasonic waves to investigate crack closure, have been in the forefront of those who claim that the crack tip continues to close even after the first closure contacts have been made, thereby leading to a lesser degree of shielding than in Elber’s view. The purpose of the present paper is to review the extensive work in the area highlighting the ultrasonic approaches as well as the current state of the art concerning crack closure, and to discuss the various views concerning the extent of shielding provided by crack closure.