Estimating spatial changes in acoustic velocity in felled Douglas-fir stems Public Deposited

http://ir.library.oregonstate.edu/concern/graduate_thesis_or_dissertations/f7623g32h

Descriptions

Attribute NameValues
Creator
Abstract or Summary
  • To compete with other building materials, the wood products industry must find a way to increase value and lower costs. Wood stiffness is important for most wood uses. Value can be increased and costs can be lowered by sorting logs for stiffness in the woods using acoustic devices mounted on harvesters and processors in order to properly allocate logs to their processing destination. This decreases shipping costs because logs do not have to be reshipped if they are delivered directly to their final processing location and increases value recovery because only logs that are fit for the end use are processed. The goal of this study was to determine if four increasingly more difficult-to measure variables - length from the butt, acoustic velocity, bark percentage, and wood density - can be used to predict the acoustic velocity variation along the length of a tree in Douglas-fir and thus improve the utility of acoustic devices as tools for the optimal bucking of trees into logs which have been sorted according to stiffness. Research was undertaken in five stands. Six trees were selected from each stand. Time of flight (TOF) acoustic velocity measured across the bole of the tree had little value in predicting the longitudinal resonance acoustic velocity of a section of the tree. Although TOF across the bole was statistically significant it had a very low correlation coefficient and lacked the ability to accurately and precisely predict resonance acoustic velocity. Wood density, moisture content, and bark percentage were not significant predictors of resonance acoustic velocity of a section of a tree. The use of tree length resonance acoustic velocities was found to be a statistically significant and strongly correlated predictor of acoustic velocity of tree section. Distance of a log section from the butt of the tree and distance of a section from the butt squared were statistically significant and strongly correlated predictors of acoustic velocity of tree sections. Final models including resonance acoustic velocity measurements, distance from the butt, and distance from the butt squared were developed with high coefficients of determination (R² 0.849 using all tree length acoustic velocities (velocities taken every 3 meters up the tree that measured acoustic velocity of the entire tree after the previous 3 meter section), R² 0.827 using initial tree length acoustic velocity (acoustic velocity of the entire tree), and R² 0.678 using initial 3 meter log acoustic velocity). The models developed were found to be stand dependent, indicating a possible need for model calibration for each stand to be harvested. Lower acoustic velocity in the butt of a tree due to high microfibril angle inhibits the predictive capability of models based on acoustic velocity measurements taken from the butt of the tree to predict acoustic velocity of 3 meter sections after the first 6 meters of the tree. Acoustic velocity models based on a 3 meter log acoustic velocity or tree length acoustic measured after the first 6 meters of the tree have been removed are the best predictors of the acoustic velocity of 3 meter sections after the first 6 meters of the tree. Final models based on measurements taken after the first 6 meters of the tree included resonance acoustic velocity measurements and distance from the butt had high coefficients of determination (R² 0.860 using third tree length acoustic velocity and R² 0.887 using third 3 meter section acoustic velocities). These models were also found to be stand dependent. The use of either a single tree length acoustic velocity measurement or a single log acoustic velocity measurement with distance from the butt and/or distance from the butt squared has the potential to increase value recovery from a log by predicting the stiffness in that log and effectively matching it to its end use.
Resource Type
Date Available
Date Copyright
Date Issued
Degree Level
Degree Name
Degree Field
Degree Grantor
Commencement Year
Advisor
Committee Member
Academic Affiliation
Non-Academic Affiliation
Keyword
Subject
Rights Statement
Language
Replaces
Additional Information
  • description.provenance : Submitted by Bodie Dowding (dowdingb@onid.orst.edu) on 2010-06-17T19:34:46Z No. of bitstreams: 1 DowdingBodieT2010.pdf: 344878 bytes, checksum: fe89f03dfbbe31968186a171588be2af (MD5)
  • description.provenance : Approved for entry into archive by Laura Wilson(laura.wilson@oregonstate.edu) on 2010-08-06T15:20:04Z (GMT) No. of bitstreams: 1 DowdingBodieT2010.pdf: 344878 bytes, checksum: fe89f03dfbbe31968186a171588be2af (MD5)
  • description.provenance : Approved for entry into archive by Julie Kurtz(julie.kurtz@oregonstate.edu) on 2010-06-18T16:56:20Z (GMT) No. of bitstreams: 1 DowdingBodieT2010.pdf: 344878 bytes, checksum: fe89f03dfbbe31968186a171588be2af (MD5)
  • description.provenance : Made available in DSpace on 2010-08-06T15:20:05Z (GMT). No. of bitstreams: 1 DowdingBodieT2010.pdf: 344878 bytes, checksum: fe89f03dfbbe31968186a171588be2af (MD5)

Relationships

In Administrative Set:
Last modified: 08/14/2017

Downloadable Content

Download PDF
Citations:

EndNote | Zotero | Mendeley

Items