Skip to Main Content
U.S. Forest Service
Caring for the land and serving people

United States Department of Agriculture

Home > Search > Publication Information

  1. Share via EmailShare on FacebookShare on LinkedInShare on Twitter
    Dislike this pubLike this pub
    Author(s): C.C. Gerhards
    Date: 1982
    Source: Res. Pap. FPL-384. Madison, WI: U.S. Department of Agriculture, Forest Service, Forest Products Laboratory, 1982: 28 pages
    Publication Series: Research Paper (RP)
    Station: Forest Products Laboratory
    PDF: View PDF  (287 KB)

    Description

    An impact stress wave was induced in the end of 2 by 6 lumber containing knots. Rather than a normal, perpendicular-to-the-axis profile in transiting by a knot, the stress wave tended to Iead in zones of clear wood in the direction of the slope of grain or slope of the annual rings and to lag behind the knot. Of three methods evaluated to time the stress wave, the "average" timing method was more consistent than other methods in flagging the 6-inch length containing a knot from adjacent clear wood 6-inch lengths. Stress wave modulus of elasticity (ESW) calculaled from the data tended to be lowest with the average timing method. AIl ESW's were higher than ESB (static bending modulus of elasticity); however, the two types of moduli tended to approach each other as knots were removed by ripping away successive 3/4-inch strips down to a specimen width of 1-3/4- inches. The results of this study should provide guidance in establishing stress wave methods for machine grading of lumber.

    Publication Notes

    • We recommend that you also print this page and attach it to the printout of the article, to retain the full citation information.
    • This article was written and prepared by U.S. Government employees on official time, and is therefore in the public domain.

    Citation

    Gerhards, C.C. 1982. Effect of knots on stress waves in lumber. Res. Pap. FPL-384. Madison, WI: U.S. Department of Agriculture, Forest Service, Forest Products Laboratory, 1982: 28 pages

    Cited

    Google Scholar

    Keywords

    Lumber, stress waves, knots, grading

    Related Search


    XML: View XML
Show More
Show Fewer
Jump to Top of Page