Effect of Knots on Stress Waves in Lumber.
Abstract
Although stress waves have been proposed as a means for rapid machine stress rating of lumber, the concept has seen only limited commercial application. A better understanding of how stress waves propagate and interact with characteristics inherent in lumber should enhance the commercial use of stress wave-techniques for lumber grading. Previous reports on stress waves were concerned with lumber elasticity or with the effects of moisture content annual rings, or slope of grain in number. This report is concerned with propagation of stress waves in lumber containing knots and how the propagation characteristics may be used to determine a modulus of elasticity based on stress waves. A static bending modulus of elasticity is included for comparison. The study is based on an evaluation of eleven 8-foot long flatsawn 2 by 6's that were subsequently ripped in five stages down to a width of about 1-3/4 inches, with reevaluation after each stage. (Author)
Document Details
- Document Type
- Technical Report
- Publication Date
- Sep 01, 1982
- Accession Number
- ADA120112
Entities
People
- C. C. Gerhards
Organizations
- Forest Products Laboratory