古木材横纹偏轴受压本构关系模型

Constitutive Relation Model of Ancient Wood under Off-axis Transverse Compression

提出了一种参数少、参数物理意义简单、参数易于获取的古木材横纹偏轴受压本构关系模型.该本构关系模型将单向纤维复合材料领域中的Sun-Chen本构关系模型引入古木材领域,并将古木材横纹偏轴受压特征与该模型结合,以简化方法反映古木材累积损伤,以便准确描述古木材横纹偏轴受压下的力学响应.以北京故宫修缮替换件为样本,制作7组70个试件,通过木材横纹受压试验获取相应的应力-应变曲线.使用偏轴角度为0°、45°、90°的古木材横纹偏轴受压试验结果求解模型参数,主曲线决定系数高达0.94.使用该模型获取偏轴角度为15°、30°、60°、75°的古木材横纹偏轴受压屈服强度和应力-应变曲线.通过模型计算结果和试验结果对比可知,在使用少量试验结果的前提下,本文提出的本构关系模型可准确计算多偏轴角度的古木材横纹受压屈服强度和应力-应变曲线,能够反映斗栱用材受压损伤特征,助力古建木构保护.

A constitutive relation model under off-axis transverse compression is proposed for ancient wood,which has few parameters,simple physical meaning and easy access to parameters.The constitutive relation model introduces the Sun-Chen constitutive relation model in the field of unidirectional fiber composites,and combines the off-axis transverse compression characteristics of ancient wood to reflect the cumulative damage of ancient wood by a simple method,so as to accurately describe the mechanical response of ancient wood under off-axis transverse com⁃pression.Taking the replacement parts of the Forbidden City as samples,seven groups of 70 specimens are made.The corresponding stress-strain curve is obtained through the transverse compression test of specimens.The model parameters are solved by using the test results with off-axis angles of 0°,45°and 90°,respectively,and the determi⁃nation coefficient of the main curve is 0.94.Using this model,the yield strength and stress-strain curves with off-axis angles of 15°,30°,60°and 75°,respectively,are obtained.The comparison between the model calculation and testing results shows that using a small number of test results,the constitutive relationship model proposed in this paper can accurately calculate the transverse compressive yield strength and stress-strain curve of ancient wood with multiple off-axis angles.The constitutive relationship model can describe the characteristics of Dougong mate⁃rial compression damage,and it is also helpful in the protection of ancient wooden structures.