Accession Number:

ADA151835

Title:

Transition Region for Corner Cracks at Holes.

Descriptive Note:

Master's thesis,

Corporate Author:

AIR FORCE INST OF TECH WRIGHT-PATTERSON AFB OH SCHOOL OF ENGINEERING

Personal Author(s):

• Chansler,P. A.

Report Date:

1984-12-01

Pagination or Media Count:

135.0

Abstract:

This study develops correction factors for currently used stress intensity factor equations to more accurately predict stress intensity factors for a corner-crack emanating from a hole as it transitions to a uniform through-the-thickness crack. These correction factors resulted in an increase in accuracy for total life prediction and much better correlation between analytical stress intensity factor predictions and experimental results in the transition region for 2024-T351 and 7075-T651 aluminum alloys. An experimental program was undertaken to generate all 2024-T351 aluminum test data. The 7075-T651 aluminum test data was generated during earlier work. Correction factors developed by Opel for 7075-T651 aluminum were evaluated for 2024-T351 aluminum and found to be excessively conservative. Hartranft and Sih suggested the stress intensity factors be evaluated at an imaginary surface at an angle phi away from the front and hole-bore surfaces. These stress intensity factors could then be used in the life prediction models for life from a corner-crack until back surface penetration. Life predictions were made using the new model, an instantaneous model which assumes a through-crack at back surface penetration, Opels model, Brussats model and the Collipriest-Ehret model. Keywords include Cracks, Crack propagation, Cracking Fracturing.

Descriptors:

• *ALUMINUM ALLOYS
• *CRACKS
• MATHEMATICAL MODELS
• LIFE EXPECTANCY(SERVICE LIFE)
• PREDICTIONS
• CRACKING(FRACTURING)
• CRACK PROPAGATION
• HOLES(OPENINGS)
• CORRECTIONS
• STRESS CONCENTRATION

Subject Categories:

• Metallurgy and Metallography
• Mechanics

Distribution Statement:

APPROVED FOR PUBLIC RELEASE