竹材蠕变应力指数的确定

Determination and analysis of bamboo creep stress exponent

对拉伸蠕变与球型压头下的压痕蠕变进行了理论分析,推导出宏观压痕试验得出的压痕蠕变应力指数与单轴拉伸试验得出的蠕变应力指数相等。在此基础上,以毛竹为研究对象,测试了其拉伸蠕变和宏观压痕蠕变,并分析了两者的蠕变行为及其联系。结果表明:竹材拉伸蠕变变形、竹材端面压痕蠕变压痕位移随时间和荷载的增加而增大,弹性段应变与应力呈线性关系;拉伸蠕变试验所测得的蠕变应力指数为1.36,在240、480、720 N的规定试验力下,竹材端面压痕蠕变试验所得的蠕变应力指数为1.47。

A theoretical analysis was made on tensile creep and indentation creep under spherical indenter. It was concluded that the indentation creep stress exponent obtained in the macro-indentation test was equal to the one obtained in the uniaxial tensile test, based on which, the tensile creep and indentation creep of Moso bamboo （Phyllostachs edulis） were investigated and compared. The results showed that both bamboo tensile creep deformation and the depth of bamboo cross section indentation creep increased with the increasing of time and load and that the strain and stress in the elastic region indicated linear relationship. The creep stress exponents obtained in the macro-indentation test under the loads of 240 N, 480 N and 720 N, and uniaxial tensile test were 1.47 and 1.36, respectively.