Fracture Toughness and Duration of Load Factor II. Duration Factor for Cracks Propagating Perpendicular-to-Grain


  • Arno P. Schniewind


<i>Pseudotsuga menziesii</i>, <i>Eucalyptus obliqua</i>, fracture mechanics, duration of load, fracture toughness, beams, notched beams, bending, tension, acoustic emissions


Dead load tests of notched beams of Douglas-fir with the crack plane parallel-to-grain and the propagation direction of the crack perpendicular-to-grain showed that presently used duration of load factors can be used for this type of loading. A decrease in strength with increasing duration was observed, but the effect was less than in unnotched beams. Ramp loading tests of messmate stringybark and Douglas-fir notched beams showed increased loads at crack initiation at slower load rates. In messmate stringybark this increase was not statistically significant, but was found significant in Douglas-fir. These results suggest that stress redistribution is taking place around the notch tip, and that a duration of load factor need not be applied to this particular system.


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