Environment enhanced fatigue crack propagation in metals: Inputs to fracture mechanics life prediction models. Final report

Technical Report · Wed Sep 01 04:00:00 EDT 1993

OSTI ID:5447333

Gangloff, R P; Kim, S

This report is a critical review of both environment-enhanced fatigue crack propagation data and the predictive capabilities of crack growth rate models. This information provides the necessary foundation for incorporating environmental effects in NASA FLAGRO and will better enable predictions of aerospace component fatigue lives. The review presents extensive literature data on stress corrosion cracking and corrosion fatigue.' The linear elastic fracture mechanics approach, based on stress intensity range (Delta(K)) similitude with microscopic crack propagation threshold and growth rates, provides a basis for these data. Results are presented showing enhanced growth rates for gases (viz., H2 and H2O) and electrolytes (e.g. NaCl and H2O) in aerospace alloys including: C-Mn and heat treated alloy steels, aluminum alloys, nickel-based superalloys, and titanium alloys. Environment causes purely time-dependent accelerated fatigue crack growth above the monotonic load cracking threshold (KIEAC) and promotes cycle-time dependent cracking below (KIEAC). These phenomenon are discussed in terms of hydrogen embrittlement, dissolution, and film rupture crack tip damage mechanisms.

• Research Organization: Virginia Univ., Charlottesville, VA (United States)
• OSTI ID: 5447333
• Report Number(s): N-94-17638; NASA-CR--191538; NAS--1.26:191538; CNN: NAG1-745; RTOP 510-02-12-10
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
360103 -- Metals & Alloys-- Mechanical Properties
360105* -- Metals & Alloys-- Corrosion & Erosion
ALLOYS
ALUMINIUM ALLOYS
ALUMINIUM BASE ALLOYS
CHEMICAL REACTIONS
CORROSION
CORROSION FATIGUE
CRACK PROPAGATION
DOCUMENT TYPES
EMBRITTLEMENT
FATIGUE
FRACTURE MECHANICS
HYDROGEN EMBRITTLEMENT
IRON ALLOYS
IRON BASE ALLOYS
MECHANICAL PROPERTIES
MECHANICS
NICKEL ALLOYS
NICKEL BASE ALLOYS
PROGRESS REPORT
STEELS
STRESS CORROSION
STRESS INTENSITY FACTORS
TITANIUM ALLOYS
TITANIUM BASE ALLOYS