Fatigue performance of wood composites subjected to edgewise bending stresses

摘要

This research project evaluated edgewise bending fatigue performance of selected wood composites by subjecting them to zero-to-maximum constant amplitude and cyclic stepped loads. The regression equations of S-N curves (applied nominal stress vs. lognumber of cycles to failure) through low 5 percent data points were derived for wood composites included in this study and proposed as design equations for achieving a conservative design of furniture frame structural members considering fatigue effects.It was observed that the equation had the form: The constant H values in the equation were 0.06, 0.08, and 0.10, for plywood, oriented strandboard (OSB), and particleboard (PB), respectively. Cyclic stepped load tests of full-size back top rail specimens indicated that Palmgren-Miner rule provided a conservative estimation of fatigue life of wood composites subjected to cyclic stepped bending stresses based on their low 5 percent limit S-N curves. Results of stress ratio analyses suggested that the ratio of material modulus of rupture (MOR) to the fatigue stress level required to be achieved for design of upholstered furniture frame members considering stepped fatigue effects could be set to 1.85 for plywood, 1.56 for OSB, and 1.46 for PB.