Development of Validated Crack Measurement System for Vibrating Structures.

摘要

Analyses were developed to obtain resonant frequencies of panels with and without cracks and subjected to vibratory loads. These analyses were extended to panels with bonded composite patches. A dynamic stress analysis method was developed for panels tested under vibratory loads produced by shaker excitation. Analytically predicted resonant frequencies and stresses compared well with test data provided by Wright Patterson Air Force Base (WPAFB). A review of crack growth data. obtained at WPAFB under vibratory loads. indicated that conventional stress intensity factor (SIF) solutions in AFGROW or other crack growth codes could not be used for accurate prediction of crack growth because of absence of methodology accounting for dynamic stresses and frequency effects. The SIF used in AFGROW were modified to account for these factors. Using the modified SIF, crack growth predictions were made for the WPAFB data on panels with and without bonded composite patches. A good correlation was obtained between predictions and test data. A Visual Crack Measurement system (VCMS) was used to monitor cracks in the WPAFB tests. An integrated VCMS design was developed. The integrated VCMS will perform crack measurement and structural integrity evaluation functions. The integrated system will also design repair patches for dynamic loading.