油松根系的轴向疲劳性能研究

Axial Fatigue Properties of Pinus Tabulaeformis Root

初次室内模拟自然界导致土壤侵蚀的循环荷载作用,研究油松根系的轴向疲劳性能.结果表明:油松根系100次和1 000次疲劳后的抗拉力和抗拉强度均大于疲劳前根系单调轴向抗拉力和抗拉强度;油松根系轴向循环应力-应变滞回曲线表现出明显的周期循环特征,"滞回环"最初阶段为较饱满的"梭形",具有较好的塑形变形和耗能能力,其间距较大,表现为"稀疏型"排列;随着循环次数的增加,"滞回环"间距越来越小,表现为"密集型"排列,趋于稳定;"滞回环"的加载段和卸载段均可用二次函数拟合,拟合曲线参数A、B、C除较小直径波动较大外,其余各根径的函数参数变化平稳;根系的疲劳轴向应变包括弹性变形和塑性变形两部分,以第20次循环为界限,总应变可划分为两个阶段:应变迅速增长阶段和应变缓慢增长阶段.

The axial fatigue properties test were carried out on pinus tabulaeformis root indoor, simulating cyclic loading leading to soil erosion in nature. Results showed that root tensile force and tensile strength of pinus tabulaeformis after fatigued cycle 100 times and 1000 times were both significantly higher than those of root under monotonic loading. The fatigue stress - strain hysteretic curve of root showed obvious cycle features. At initial stage, ＂hysteretic loop＂ was a plump shape of ＂spindle＂ with a better capacity of plastic deformation and energy dissipation, and was arranged for ＂sparse＂ but not close. With increasing cycle number, hysteretic loop spacing was more and more intensive which tended to be stable. ＂Hysteretic loop＂ of loading section and unloading section were both fit by quadratic function, The fitting parameter A, B and C of ＂ Hysteretic loop＂ varied smoothly with increasing cycle number in addition to the smaller diameter roots. Total deformation of hysteresis curve included elastic deformation and plastic deformation. With 20th cycle for boundaries, total strain was divided into two stages： rapid growth stage and slow growth stage.