• van Dyk, Hermanus H.
  University of Maine Graduate School
  

This study investigated using ultrasonic testing and analyses techniques to determine their feasibility for defect detection in spruce lumber. Experiments were conducted in the radial direction in lumber and the effect of induced defects on ultrasonic wave characteristics was determined. Ultrasonic velocity was found to be ineffective due to changes in wavelength and frequency when large defects are present. Amplitude, peak frequency magnitude and area under the frequency spectra showed statistically significant differences between clear and defect bearing samples, but the variation in properties was found to be too high for these methods to be effectively applied. Variation in the data was attributed to inherent variation in the material and related to density and microstructure. When sound intensity level, a parameter that includes density, was calculated' variation between samples decreased to a level where distinctions could be made between clear and defect bearing wood, both within and between samples. Analyses and comparison of the frequency spectra showed clear changes with the introduction of defects.