Assessment of brown-rot decay using X-ray computer tomography and ultrasonic measurements

Mcgovern, Megan

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https://hdl.handle.net/2142/29708 Copy

Description

Title

Assessment of brown-rot decay using X-ray computer tomography and ultrasonic measurements

Author(s)

Mcgovern, Megan

Issue Date

2012-02-06T20:12:13Z

Director of Research (if dissertation) or Advisor (if thesis)

Reis, Henrique M.

Department of Study

Industrial&Enterprise Sys Eng Civil & Environmental Eng

Discipline

Systems & Entrepreneurial Engr Civil Engineering

Degree Granting Institution

University of Illinois at Urbana-Champaign

Degree Name

M.S.

Degree Level

Thesis

Keyword(s)

• Loblolly pine
• wood
• wood decay
• rot
• X-ray computed tomography
• wood density
• ultrasonic velocity
• attenuation.

Abstract

Loblolly pine (Pinus taeda) wood cube specimens were exposed to Gloeophyllum fungus (Gloeophyllum trabeum) for increasing periods of time ranging from one week to twelve weeks. The corresponding mass of each of these specimens was recorded before and after they were subjected to the controlled decay. X-ray computed tomography (CT) was then carried out. From the CT scans and recorded mass data, the specimens’ corresponding volumes and densities were calculated. Blocks decayed for twelve weeks experienced, on the average, the greatest loss of mass (≈40%), volume (≈30%), and density (≈37%). The observations quantified the well-known effect of non-uniform decay, with the greatest occurring at the surface in contact with the fungi and decreasing to the opposite surface. Wood blocks subjected to controlled decay for twelve weeks lost 47% of density at the surface in contact with the fungi and 28% at the opposite surface, while blocks subjected to only one week of decay experienced over 5% density loss at the surface in contact with fungi and nearly 0% at the opposite surface. While the mass loss of specimens exposed to only one week of controlled decay was difficult to evaluate because of initial moisture absorption, these results indicate that x-ray CT can detect decay in wood specimens exposed to only one week of controlled decay using density measurements. For each of the three principal material directions of these specimens with controlled decay, ultrasonic longitudinal and (polarized) shear velocity measurements along with the corresponding attenuation measurements are presented. The measurements were carried out using longitudinal and shear ultrasonic transducers with a center frequency of 100 kHz. A steel delay line was used because of the relative small size of the wooden specimens relative to the used wavelengths. Waveform averaging was used along with the phase-slope method to measure velocities. It was observed that the velocities increase with increasing frequency and decrease with increasing amount of decay, while the corresponding attenuations increase with increasing frequency and with amount of decay.

Graduation Semester

2011-12

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http://hdl.handle.net/2142/29708

Copyright and License Information

Copyright 2011 Megan E McGovern

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