蠕变经历对落叶松材静强度影响

Effects of Creep History on the Static Strength of Larix dahurica

木材在长期重复载荷作用下的蠕变经历,即蠕变变形的发展和积累以及木材局部组织损伤和龟裂,使木材再次承载时的力学性质产生变异和劣化.试验研究表明,落叶松材在小于其比例极限应力的重复载荷作用下,经过3万次以上应力循环的蠕变经历,使其纤维方向弯曲弹性模量增大10％;顺纹抗剪强度和抗弯强度有减小趋势,这与蠕变变形的积累和木材局部组织损伤和龟裂程度密切相关,对于无明显塑性变形和局部损伤的试件其强度无明显影响.

Wood belongs to the viscoelastic materials category. The ultimate deflection of wooden beams, including accumulated creep, increases after repeated loading cycles, and resultant mechanical properties are reflected in very different degradations. The results of experiments indicated that the elastic modulus, which parallel to the grain due to creep history at lower proportinal limit stress for 30 thousand times, increases by 10%. Shear strength and bending strength parallel to the grain tend to decrease, which is relevant to accumulated plastic deflection and cracking due to creep history.