Fatigue behavior of OSB in shear

A five-point bending test was used to investigate shear fatigue properties of 18.26-mm- (23/32-in.-) thick commercial oriented strandboard (OSB) under repeated sinusoidal load. The test was found to be an effective low-cost method of determining shear fatigue behavior of OSB. Maximum applied stress was controlled between 70 and 100 percent of the material’s average static strength, and loading frequencies of 0.5 and 1 Hz were used. Fatigue behavior in shear using a five-point bending test is described as a three-stage process in the plot of load-deflection ratio versus cycles. Fatigue failure in shear is defined as the sharp loss of the load-deflection ratio that initiates stage II. Prior to this sharp reduction, there was a gradual decline in the ratio. The fatigue properties (S-N curve (stress-number of cycles)) for OSB are produced, where the stress level percent is based on a predicted static strength. A linear regression closely fits the S-N data. A stress level of 60 percent (based on the predicted strength of the materials) with an associated fatigue life of 10 to the fifth power cycles was the smallest load level tested. The trend of the data indicates that the endurance limit (infinite life) of the OSB is well below this stress level. Although the average fatigue life for material tested at 80 percent stress level and 0.5 Hz is 19 percent greater than for 1 Hz, there was no statistically significant difference between the fatigue lives at the two frequencies.

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