Predicting crack initiation and propagation in pressurized aircraft structures
(0) Estimation of the total life of an aircraft or an aerospace component requires assessment of damage and fracture evolution under cyclic spectral fatigue service loading. To estimate the total life of an aircraft or aerospace components requires having high cycle fatigue data (S-N) for the material under study Certification by Analysis-Supported-by-Test (CAST) allows for risk mitigation that complies with FAA certification requirements, ASTM validation requirement, and the FAA building block certification strategy. This CAST effort provided a risk mitigation Damage Tolerance Analysis (DTA) strategy for condition based non-invasive inspection of the fuselage skin area under the antenna mounting of an aircraft. The methodology addresses the following critical issues: where, when and why multi-site failure (initiation, growth) occurs, and if repair bulletin needs to be issued. If repair could be avoided operators/owners would be spared considerable expense. A multi-scale progressive fatigue crack growth failure analysis combined progressive damage and fracture approach is used to predict the upper/lower fuselage, antenna, and the flange multibolt connections. A novel method (implemented in the GENOA progressive failure analysis software) of predicting Kth and KIC using a crack tip process zone strain energy based approach is presented. The model estimates Kth and KIC to derive: (1) material fracture toughness vs. thickness from stress-strain curve; (2) material fatigue crack growth curve (da/dn vs. dk) from fracture toughness; and (3) structural S-N Curve of notched part (S-N data for Kt>1). Using the progressive crack growth analysis in GENOA it has been shown as an example that multi-site fatigue cracks arising from antenna installation in the aircrafts pressurized fuselage did not grow unstably nor coalesce during the service life of the aircraft. Furthermore the residual strength of the antenna installation is never exceeded. With the analysis supported by validating tests, FAA accepted the analytical results and the aircraft retained certification with no repairs required.
Pressurized aircraft structure Crack initiation Crack propagation Life estimation Progressive failure analysis
Bob Farahmand Frank Abdi Kamran Nikbin
Alpha Star Corp, Long Beach, CA 90804,USA Imperial College London, Exhibition Road, London SW7 2AZ, UK
国际会议
2012 International Symposium on Structural Integrity 2012国际结构完整性学术研讨会 ISSI 2012
济南
英文
33
2012-10-31（万方平台首次上网日期，不代表论文的发表时间）