Assessment of Longitudinal Shrinkage and Swelling Using the APA and ASTM Methods
Keywords:APA, ASTM, longitudinal shrinkage, radiata pine, swelling
AbstractThe APA and ASTM methods of measuring longitudinal shrinkage and swelling were evaluated and compared using radiata pine coupons with a wide range of wood properties and different operators. The two methods gave different measurements of longitudinal shrinkage and swelling as a result of differences in the location of the measurement points, and the ability to correct for out-of-plane distortion. The APA method gave more precise measurements from the use of inserted brass eyelets and the correction of out-of-plane distortion with a vacuum table. The measurements were not affected by wood type or operator. The ASTM method was found to be sensitive to the condition of the transverse surface at the measurement point and to the presence of drying distortion. The measurements varied in response to wood type and operator. The results indicate the APA method is more precise for measuring longitudinal shrinkage and swelling when measurements are made in series along boards and cants.
APA test method (2001) P-1. Linear expansion and thickness swell measured from oven-dry or 50% relative humidity to vacuum-pressure soak. APA PRP-108 Performance standards and qualification policy for structural-use panels. Pp. 43-44. APA-The Engineered Wood Association.nASTM standard (1999) D1037-96a, Sections 107-110, Linear variation with change in moisture content. Annual Book of ASTM Standards, Volume 04.10: 154-156.nLittell RC, Milliken GA, Stroup WW, Wolfinger RD (1996) SAS System for Mixed Models. SAS Institute Inc., Cary, NC 633 Pp.nNordström J-EP, Johansson I (1995) End-grain glue-joint strength. Part 2: The microstructure of machined end-grain surfaces of spruce timber. Holz Roh-Werkst 53:38.nOehlert GW (1992) A note on the delta method. Am Stat 46(1):27-29.nSAS Institute Inc (2000) SAS/STAT User's Guide. Version 8, Volumes 1, 2, and 3. SAS Institute Inc., Cary, NC.n
The copyright of an article published in Wood and Fiber Science is transferred to the Society of Wood Science and Technology (for U. S. Government employees: to the extent transferable), effective if and when the article is accepted for publication. This transfer grants the Society of Wood Science and Technology permission to republish all or any part of the article in any form, e.g., reprints for sale, microfiche, proceedings, etc. However, the authors reserve the following as set forth in the Copyright Law:
1. All proprietary rights other than copyright, such as patent rights.
2. The right to grant or refuse permission to third parties to republish all or part of the article or translations thereof. In the case of whole articles, such third parties must obtain Society of Wood Science and Technology written permission as well. However, the Society may grant rights with respect to Journal issues as a whole.
3. The right to use all or part of this article in future works of their own, such as lectures, press releases, reviews, text books, or reprint books.