榉木横纹三点弯曲受压声发射损伤模型研究

为探究木材在横纹受压下脆性断裂的损伤演变过程，依据声发射（acoustic emission,AE）事件构建木材损伤变量本构模型。首先，将木材内部等效为若干根互不相关的受压木纤维，每根横纹受压木纤维又可等效为受压微弹簧。然后基于概率思想，在微弹簧的中性层受力分析基础上，假设横纹受压的微弹簧极限应变服从某一分布函数的随机变量，经过分析得到微弹簧的极限应变服从分布函数和木材横纹受压损伤演化方程，以及累计AE振铃计数-应变曲线和损伤变量之间关系。最后，通过榉木(Zelkova schneideriana)试件三点弯曲AE试验得到归一化累计AE振铃计数-应变曲线，再利用Gaussian曲线拟合出所需参数，进而得到微弹簧的极限应变分布规律和损伤演化方程的表达式，建立三点弯曲受压AE损伤模型。结果表明，累计AE计数与榉木横纹受压的微观损伤过程是对应的，并且结合AE试验数据得出的损伤演化数学模型可以很好地反映榉木横纹受压过程中的损伤演化特征。

Acoustic Emission Damage Model of Zelkova schneideriana Transverse Grain Compression Three-Point Bending

In order to explore the damage evolution process of wood brittle fractures under transverse grain compression,a constitutive model of wood damage variables was constructed based on acoustic emission (AE) events.First of all,the interior of the wood was equivalent to several unrelated compressed wood fibers,and each transverse compressed wood fiber could be equivalent to a compressed microspring.Then,based on probabilistic thinking,the force analysis was conducted on the neutral layer of the microspring,from which it was assumed that the ultimate strain of the microspring under the transverse grain obeyed a random variable of a certain distribution function.Through the analysis,the distribution function that ultimate strain of the micro spring obeyed and the damage evolution process of Zelkova schneideriana under the transverse grain,as well as the relationship between the cumulative AE ringing count strain curve-the damage variable were obtained.Finally,the normalized cumulative AE ringing count-strain curve was obtained through the three-point bending AE test of Z.schneideriana specimen,and the required parameters were fitted by Gaussian curve,then the ultimate strain distribution law and the expression of damage evolution equation of micro spring were obtained,and the AE damage model of three-point bending compression was established.The research results showed that the cumulative AE count corresponded to the microscopic damage process of Z.schneideriana under compression,and the damage evolution mathematical model derived from the AE test data could well reflect the damage evolution characteristics of the Z.schneideriana under the transverse grain compression.