UCLA Extension

Structural Integrity of New and Aging Metallic Aircraft

This course presents both fundamental concepts and practical instruction in methods for fatigue, durability, and damage tolerance analysis/testing of metallic aircraft structures. The lectures emphasize the use of modern fatigue and fracture mechanics technology in the design of durable, damage-tolerant aircraft structures and the extended safe use of aging aircraft.

The course opens with a discussion of basic fatigue and fracture behavior of structural metallic materials. With this background, the ensuing lectures detail the structural methods used in the aircraft industry to develop fatigue loading spectra, as well as fatigue life, crack growth, and residual strength analyses. The course also explores the application of this technology to verify the structural integrity and longevity of new aircraft, along with life monitoring, maintenance, and life extension of aging aircraft.

Course Materials

Lecture notes are distributed on the first day of the course. These notes are for participants only and are not otherwise available for sale or unauthorized distribution.

Coordinator and Lecturer

Matthew Creager, PhD, President, Structural Integrity Engineering, Chatsworth, California. Dr. Creager directs the technical activities of SIE and serves as a principal engineer on consulting internal development programs at SIE. SIE—with offices in Chatsworth, Seattle, and Madrid—has programs supporting design and certification of new aircraft and major modifications to existing aircraft, as well as issues related to aging aircraft. Dr. Creager has over 30 years’ consulting experience in fatigue and fracture mechanics applications for aerospace structures, and has participated in damage tolerance and durability analyses for dozens of military and commercial aircraft. He is currently working on programs involving structural modifications to commercial and special mission aircraft, commercial and military structural integrity programs, probabilistic fatigue and fracture mechanics, and aircraft life extension programs.

Lecturers

Thomas R. Brussat, PhD , Aircraft Structural Integrity Consultant, Atlanta, Georgia. Dr. Brussat has dedicated almost 50 years to the development and application of durability and damage tolerance technology to the Aircraft Structural Integrity Program (ASIP). With Lockheed Martin Aeronautics Company he served 21 years as the Contractor Team Lead for durability and damage tolerance for the F-22 “Raptor,” covering all phases of its ASIP, from initial design requirements and design analysis, through full-scale testing, to the implementation of its 21st-century Force management program. From 1966 to 1986 Dr. Brussat was engaged in cutting-edge research supporting the initial development of USAF and USN damage tolerance methodology and criteria.

Since 2008, he has continued to support ASIP as a private consultant. He co-authored the USAF Aircraft Structural Risk & Reliability Analysis Handbook in 2010 and is active in developing and applying improved methods for structural risk analysis. Dr. Brussat was an invited speaker at the 2013 ASIP Conference and received the Lincoln Award for career achievement in Aircraft Structural Integrity. He has published numerous technical papers on fracture mechanics, crack growth analysis and test, and structural risk analysis.

Paul N. Clark, Ph.D., Principal Engineer, Southwest Research Institute, San Antonio, Texas – Hill Air Force Base Extension and Adjunct Professor, Department of Mechanical Engineering, University of Utah, Salt Lake City, Utah.

Dr. Clark is considered a subject matter expert in the areas of fatigue and corrosion of aging aircraft, crack growth mechanisms, damage tolerance and fracture mechanics. Life prediction, risk analysis, failure evaluation, failure prevention, experimental protocol development and test planning are other areas of expertise. He works in concert with United States Air Force ASIP (Aircraft Structural Integrity Program) managers to provide engineering services and continuity to continually evolving programs. Fleet-wide trending and risk projections as well as failure investigations pave the way for new structural inspections as well as repair designs, modifications, redesigns and analyses.

Dr. Clark has worked on a variety of aircraft with the United Stated Air Force. These experiences have provided numerous opportunities for creative and successful solutions to challenges leading to improved fleetwide airworthiness for these aging aircraft. Additionally, numerous publications and presentations at conferences and symposia have been produced from these experiences.

Dr. Clark also serves as an Adjunct Professor for the Department of Mechanical Engineering at the University of Utah in Salt Lake City where he has mentored dozens of graduate students and engineers through challenging programs geared toward developing solutions for today’s structural integrity and aging aircraft challenges.

Daily Schedule

Monday am – Part 1: Course Overview (Creager)

Course overview, historical background, design criteria, design philosophies, aging aircraft issues

Monday am – Part 2: Fracture Mechanics Basics (Creager)
Crack tip stress fields, stress intensity factor, small-scale yielding, plane stress and plane strain.

Monday pm – Failure of Cracked Structures (Creager)
Failure theories, failure prediction, fracture toughness testing, crack growth resistance curves, damage tolerance analysis of redundant structures

Tuesday am – Fundamental Fatigue Analysis (Clark)
Fundamental fatigue design approaches and technical approaches including, S-N (Wohler) curves, stress ratio effects, Goodman diagrams, fatigue limit estimation, stress-life, strain-life, cyclic stress-strain curves, strain hardening and softening. Specific fatigue analysis examples.

Tuesday pm – Fatigue Analysis Rules and Challenges (Clark)
Stress concentrations and notches, stress flow, local strain analysis, Neuber’s rule, residual stresses, cold-expansion, Palmgren-Miner rule, specific example aircraft challenges applied to fleet management.
Broad discussion of fatigue mechanisms, fatigue variables, and fatigue nucleation mechanisms.

Wednesday am – Material Fatigue Behavior (Clark)
Materials characterization, material discontinuities, initial discontinuity state and modified (evolving) discontinuity state and small fatigue cracks. Material behaviors for fatigue nucleation and fatigue crack growth. Influence from corrosion fatigue and fretting fatigue with examples.

Material testing and interpretation of test results, experimental test protocol development; full-scale fatigue testing, interpretation and implementation of results into fleet management and inspection, with case study examples.

Wednesday pm – Fatigue Crack Growth Analysis (Brussat)
Fundamentals of crack growth prediction; crack growth testing; variables affecting da/dN; load spectrum effects; crack retardation models; truncation, clipping and cycle counting; crack growth computer programs.

Thursday am – Fatigue Crack Growth and ASIP (Brussat)

Stress intensity estimation; spectrum crack growth rate; damage tolerance testing & analysis of airframe structure (lugs, bolted joints, and stiffened panels); continuing damage; crack growth durability & EIFS concept; applications of crack growth analysis in the USAF ASIP including in-service inspection, maintenance, & individual aircraft tracking.

Thursday pm – Part 1: Aircraft Structural Risk & Reliability Analysis (Brussat)

Limitations of deterministic life analysis; probability of failure criteria; Single Flight Probability of Failure; risk analysis data requirements; inspection and repair effects; calculation methods; examples.

Thursday pm – Part 2: Aircraft Structural Failures: Hard Lessons of History (Brussat)

Five events that redefined aircraft structural integrity analysis and verification requirements.

Friday am – Part 1: Fatigue Loading Spectra (Creager)
Usage spectra, mission profiles, load excedance curves, service loading spectra measurement Sequence affects in fatigue crack initiation.

Friday am –Part 2: Example Applications (Creager)
Fatigue crack initiation in joints, repairs (design, analysis, and test); supplementary inspection programs; structural life extension programs

For more information contact the Short Course Program Office:
shortcourses@uclaextension.edu | (310) 825-3344 | fax (310) 206-2815

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