Effect of cross grain on stress waves in lumber
Forest Products Laboratory, 1980 - House & Home - 9 pages
This report evaluates the effect of cross grain on the transit time of longitudinal compression stress waves in Douglas-fir 2 x 8 lumber. Results should aid development of lumber stress grading systems using modulus of elasticity measurements based on stress waves. (Author).
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3-foot length 3-foot transit distance 32 grid points average basis based on average basis yielded celerometer centered about cross centerline basis centerline timing basis compression stress containing spiral grain cross grain cross sections CX3 and CX6 differences edges effect of cross eight grid points end nearer foot evaluated fastest point basis five Douglas-fir 8-foot flatsawn grain angle grain slope growth rings hammer end horn lip I I I I I I IMPACT END imum induced stress wave interactions with lumber lagging long axis matched runs measured transit microsecond midwidth modulus of elasticity moisture content negative cup number 8 end perpendicular Pith side POINT NUMBER Figure point timing basis points spaced Poisson's ratio positive cup reference accelerometer right-handed spiral grain shown in figure slope of grain Specific gravity Specimen number stress-wave apparatus stress-wave E's stress-wave measurements stress-wave transit trend uniform bending Waves in Lumber wide faces yielded a stress-wave