Predictive models were developed for stiffness and bending strength of southern pine 2x6, eight ft. lumber using nondestructive measurements of stresswave velocity, density and visual characteristics such as knots, slope of grain and rate of growth. To account for local areas of weakened material due to knots and slope of grain, a grid system was developed to quantify general knot size and location. Multiple regression models were created using these physical and visual measurements. Two sets of models were developed: one that removed influential samples with abnormal wavespeeds (greater than 18,000 ft./s) indicative of poor wood quality; and, models that included all samples. Static modulus of elasticity (MOEs) model performance was significantly better for those that removed influential samples compared to the all-sample models, with an R2 of 0.892 and 0.720, respectively. Modulus of rupture (MOR) model performance was slightly better with influential samples removed R2 of 0.714 and 0.690, respectively. The location of knots within a board significantly altered the mechanical properties, especially bending strength. The results indicate potential for greater specification of allowable stresses for different orientations during bending. A simulated grading study was conducted to assess the feasibility of the developed models. Thousands of samples were generated according to estimated variable distributions and graded according to the American Lumber Standards Committee Machine Graded Policy. Results suggest that these models may be feasible in an actual lumber grading scenario.
| Identifer | oai:union.ndltd.org:LSU/oai:etd.lsu.edu:etd-11182013-144154 |
| Date | 17 December 2013 |
| Creators | Romer, Jacob |
| Contributors | Shupe, Todd F., De Hoop, Cornelis F., Hse, Chung Y. |
| Publisher | LSU |
| Source Sets | Louisiana State University |
| Language | English |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://etd.lsu.edu/docs/available/etd-11182013-144154/ |
| Rights | unrestricted, I hereby certify that, if appropriate, I have obtained and attached herein a written permission statement from the owner(s) of each third party copyrighted matter to be included in my thesis, dissertation, or project report, allowing distribution as specified below. I certify that the version I submitted is the same as that approved by my advisory committee. I hereby grant to LSU or its agents the non-exclusive license to archive and make accessible, under the conditions specified below and in appropriate University policies, my thesis, dissertation, or project report in whole or in part in all forms of media, now or hereafter known. I retain all other ownership rights to the copyright of the thesis, dissertation or project report. I also retain the right to use in future works (such as articles or books) all or part of this thesis, dissertation, or project report. |
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