Theses and Dissertations

Issuing Body

Mississippi State University


Olsen, D. Gregory

Committee Member

Vizzini, J. Anthony

Committee Member

Daniewicz, R. Steven

Date of Degree


Document Type

Graduate Thesis - Open Access


Aerospace Engineering

Degree Name

Master of Science (M.S.)


James Worth Bagley College of Engineering


Department of Aerospace Engineering


Fatigue-crack growth data for the lower arm of the Apache helicopter’s scissor assembly is presented from an Army alternate source qualification test. The lower arm model is imported to finite element analysis software to obtain the stress state at a crack location. The stress state and geometry are used in seven fatigue-crack growth cases in NASGRO and AFGROW, with an additional four cases discussed briefly. The results from the fatigue-crack growth routines are compared to the fatigue-crack growth data from the Army’s test. One case reproduces the crack growth data prior to breakthrough. Some cases are shown to be more applicable to this configuration than others are. The process of performing fatigue life estimates is discussed. Suggestions are made on the viability of this approach and possible future avenues for development.