低温对红松和大青杨木材力学性质的影响

以红松和大青杨木材为例,研究环境温度变化(尤其是低温)对木材力学性质的影响。在气干和饱湿状态下,对标准样本进行静载荷测试,获取两种木材心材和边材件在温度为20、5、-5和-20 ℃时的抗弯弹性模量、抗弯强度和顺纹抗压强度,分析各参数随温度降低的变化规律。结果表明:温度是影响木材力学性质的一个重要因素,随温度降低,气干材的抗弯弹性模量、抗弯强度和顺纹抗压强度均以近似线性趋势增大; 饱湿材各力学参数变化曲线则存在拐点,在-5～20 ℃之间,随着温度降低,各力学指标增大较慢,在-20～-5 ℃之间,随着温度降低,各力学指标增大较快; 与气干材相比,饱湿材的各力学参数对低温响应更敏感,-20 ℃时饱湿材各力学参数较20 ℃时提高约67%,而气干材-20 ℃时各力学参数仅约较20 ℃时提高15%。

Effect of low temperature on the mechanical properties of Pinus koraiensis and Populus ussuriensis timber

Pinus koraiensis and Populus ussuriensis timber were used to study the influence of environmental temperature(especially low temperature)on the mechanical properties of wood in this paper. The wood specimens of two species were conducted a series of wood quality tests at air-dried and wet conditions. Then the modulus of elasticity(MOE), modulus of rupture(MOR)and compression strength of heartwood and sapwood were obtained and analyzed at -20 ℃, -5 ℃, 5 ℃, and 20 ℃ temperature. The results showed that temperature was one of the important factors affecting the MOE, MOR and compression strength of wood. As temperature decreased,these mechanical parameters of air-dried wood increased linearly, but for the nonlinearly increased wet wood, these parameters decreased from 20 ℃ to -5 ℃, but increased fast from -5 ℃ to -20 ℃. The mechanical properties of wet wood were more sensitive to low temperature than that of air-dried wood, which of wet wood were about 67% higher at -20 ℃ than that at 20 ℃, but the corresponding value of air-dried wood only increased about 15%.