SYMPOSIA PAPER Published: 01 August 2022
STP163820210048

Advanced Noncontact Measurement Technologies for a CF-188 Structural Fatigue and Residual Strength Test

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A full-scale fatigue test was conducted by the National Research Council (NRC) on an inboard wing leading-edge flap (ILEF) of a CF-188 fighter. The objective was to determine whether the service life of this component could be extended after a midlife structural modification was performed. The NRC's Structural Mechanics and Monitoring (SMM) Team was tasked with the application of various different experimental measurement techniques; including digital image correlation (DIC), fiber optical strain sensor (FOS), and residual stress x-ray diffraction (XRD) measurements; to help provide a more comprehensive illustration of the deformation strain experienced by the ILEF during various stages of testing, aid in the detection of damage progression, and provide data to aid in structural integrity life assessment of the control surface. The DIC system was used for trend line monitoring and for detecting the presence of residual plastic strain after the residual strength test was completed. No monotonically increasing strain trends were observed from the full-field data sets. An additional analysis of the strain data both before and after RST loads did not conclusively show evidence of significant residual strains in the test article (ILEF); however, the residual strains remaining in the inner wing after RST suggest either some degree of damage to the wing or actuator difficulties in achieving the 0-g load condition post RST. The XRD system provided key information regarding shot peened portions of the ILEF lugs. Comparisons between XRD scan measurements from shot peened and as-machined areas on the ILEF lugs show that residual compressive stresses induced by shot peening were relatively consistent across all lugs. The magnitudes of the stress measured (approximately –170 to –195 MPa) in the shot peened areas were significantly above the ones measured from the as-machined areas but below the theoretical Almen 8A residual stress of –219.23 MPa.

Author Information

Backman, David
National Research Council Canada, Aerospace Research Center, Ottawa, ON, CA
Li, Linxi
National Research Council Canada, Aerospace Research Center, Ottawa, ON, CA
Sa, Jong, Hyun
National Research Council Canada, Aerospace Research Center, Ottawa, ON, CA
Brunet, Stephane
National Research Council Canada, Aerospace Research Center, Ottawa, ON, CA
Rutledge, Robert
National Research Council Canada, Aerospace Research Center, Ottawa, ON, CA
Jain, Saksham
National Research Council Canada, Aerospace Research Center, Ottawa, ON, CA
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Details
Pages: 83–115
DOI: 10.1520/STP163820210048
ISBN-EB: 978-0-8031-7724-6
ISBN-13: 978-0-8031-7723-9