Title page for ETD etd-0708103-163628


Type of Document Dissertation
Author Vun, Ronnie Yunheu
Author's Email Address yvun1@lsu.edu
URN etd-0708103-163628
Title Ultrasonic Characterization of Engineering Performance of Oriented Strandboard
Degree Doctor of Philosophy (Ph.D.)
Department Forestry, Wildlife, & Fisheries
Advisory Committee
Advisor Name Title
Qinglin Wu Committee Chair
Charles J. Monlezun Committee Member
Eyassu Woldesenbet Committee Member
Quang Van Cao Committee Member
W. Ramsay Smith Committee Member
Richard L. Kurtz Dean's Representative
Keywords
  • non-contact ultrasonics
  • online application
  • ANOVA
  • direct contact ultrasonics
  • density calibration
  • root mean square voltage
  • transmissivity coefficient
  • lead break calibration
  • acoustic emission
  • EN300
  • RILEM
  • high stress level
  • particulated size comparison
  • creep rupture
  • particlboard
  • red cedar
  • bagasse
  • spatial resemblance
  • high transduction transducer
  • impedance
  • stress stabilization
  • fracture initiation and propagation
  • creep recovery
  • viscoelastic components
  • critical defect location
  • defect trench
  • critical crack
  • internal bonding
  • gagescope
  • secondwave
  • velocity
  • attenuation
  • dynamic rising moisture content
  • strength correlation
  • MOR
  • MOE
  • loblolly
  • three-layer oriented strandboards
  • phenol formaldehyde
  • zero-void densification
  • backward elimnation
  • aspen
  • flake alignment
  • density validation
  • out of limit
  • control limit
  • PRESS
Date of Defense 2003-05-06
Availability unrestricted
Abstract
Direct-contact (DC) and non-contact (NC) ultrasonic transmission (UT) methods were developed to characterize the structural performance of oriented strandboard (OSB). The UT variable velocity was shown to be sensitive to the physical impediments caused by flake interfacial boundaries and embedded voids. Both attenuation and root mean square (RMS) voltage were good indicators of the “zero void” densification level for OSB, a point of the greatest transmissivity of the stress wave energy.

For both DC and NC methods, the predicted densities of the model were validated for spatial distribution over each OSB type. Based on the EN300 standard for panel manufacturing, the control limits were ±10% of the panel average density. The density prediction was found to improve with higher resin content (RC) and higher nominal density (ND) levels. From the out-of-limits plots, the predicted in-situ densities produced a reasonably spatial coherence to the measured values. All panels made with ND 0.60 g/cm3 or greater conformed well within the limits, with declining conformity towards lower RC panels.

For each composite type made of different particle sizes, the equilibrium moisture content showed a decreasing trend toward smaller particle panels. The attenuation and RMS were good indicators for moisture change and densification level for each composite type. The velocity, sensitive to physical resistance of particle sizes, increased with increasing IB strength and sample density, manifesting the positive influence of layering, resin content, and the negative effect of bark as a constituent.

The results of the creep rupture tests on commercial OSB using an acoustic emission (AE) technique indicated that the cumulative AE event count parameter was highly correlated with deflection parameter and appropriately represented the accumulation of incipient damage. Under high stress levels, specimens with high moisture content (MC) sustained the worse damages having the shortest creep rupture time followed by specimens with dynamically rising MC. Defects on the compression-side of the bending specimen were found critical to creep rupture than those on the tension-side. The in-plane fracture patterns tended to follow the defect trenches of low-density valleys, and worsened with greater variability of the horizontal density, indicating the need to measure and control the horizontal density variation within reasonable limits.

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