摘要
为研究超高性能混凝土(UHPC)轴拉破坏全过程的声发射(AE)机理和分形特征,首先,开展了不同钢纤维(端钩形、微波纹形和直圆形)增强的UHPC轴拉试件破坏试验,得到UHPC轴拉破坏过程中的声发射信号;其次,利用快速傅里叶变换计算信号的主频,分析主频在试验过程中的分布特征;然后,基于分形理论利用分形盒维度计算方法对信号进行分形分析,并探究分形盒维度与主频之间的关联性;最后,利用小波包变换方法计算破坏过程中的平均频带能量,分析不同应力状态下各频带能量的演变规律。试验结果表明:变形纤维的端钩和波纹与基体滑移过程产生较高的主频信号,而直圆纤维与基体滑移过程产生较低的主频信号;试件破坏阶段主频段信号分布增多,但依然以基体微裂和钢纤维相对滑移为主;分形盒维度在试件开裂前分布较集中,且在即将破坏时分形盒维度增大,开裂后变分散,新生微裂纹产生的信号分形盒维度与开裂前类似,宏观裂纹扩展产生的信号分形盒维度降低;平均分形盒维度随主频的增大而增大,呈近似二阶多项式变化,主频越高的信号复杂程度越高;AE信号能量集中于1~4频段,不同纤维增强试件的主要能量在频段上的分布不同,但在即将破坏时所有试件能量均由低频向高频转变。说明声发射信号具有良好的分形特征,且能很好地反映UHPC轴拉破坏过程中的损伤特性。
In order to study the acoustic emission(AE) mechanism and fractal characteristics of ultra-high performance concrete(UHPC) in the whole process of axial tensile failure.Firstly,the failure tests of UHPC axial tensile specimens reinforced with different steel fibers(end hook type,microwave texture type and straight circular type) were carried out,and the AE signals in the process of UHPC axial tensile failure were obtained.Secondly,the dominant frequency of the signal was calculated by fast Fourier transform,and the distribution characteristics of the dominant frequency in the test process were analyzed.Then,based on the fractal theory,the fractal analysis of the signal was carried out by using the fractal box dimension calculation method,and the correlation between the fractal box dimension and the dominant frequency was explored.Finally,the wavelet packet transform method was used to calculate the average frequency band energy during the failure process,and the evolution law of each frequency band energy under different stress states was analyzed.The results show that the end hook and ripple of the deformed fiber produce a higher dominant frequency signal during the sliding process with the matrix,while the straight circular fiber produces a lower dominant frequency signal during the sliding process with the matrix.In the failure stage of the specimen,the signal distribution of the dominant frequency band increases,but it is still dominated by matrix micro-crack and relative slip of steel fiber.The fractal box dimension is concentrated before the cracking of the specimen,and the fractal box dimension increases when the specimen is about to be destroyed,and becomes dispersed after cracking.The fractal box dimension of the signal generated by the new micro-crack is similar to that before cracking,and the fractal box dimension of the signal generated by the macro-crack propagation is reduced.The average fractal box dimension increases with the increase of the dominant frequency,which is approximately a second-order
作者
袁明
邓俊杰
刘昀
颜东煌
黄练
韩怀志
YUAN Ming;DENG Jun-jie;LIU Yun;YAN Dong-huang;HUANG Lian;HAN huai-zhi(School of Civil Engineering,Changsha University of Science&Technology,Changsha 410114,Hunan,China;Guangxi Jiaotou Technology Co.,Ltd.,Nanning 531400,Guangxi,China;School of Road and Bridge Engineering,Hunan Communication Polytechnic,Changsha 410132,Hunan,China;School of Architecture Engineering,Guangxi Minzu University,Nanning 530006,Guangxi,China)
出处
《长安大学学报（自然科学版）》
CAS
CSCD
北大核心
2024年第3期93-103,共11页
Journal of Chang’an University(Natural Science Edition)
基金
国家自然科学基金项目(52078054,51878073)
湖南省交通科技项目(201932)
湖南省自然科学基金项目(2021jj30730)
湖南省研究生科研创新项目(CX20200832,X20190650)。
关键词
桥梁工程
超高性能混凝土
声发射
裂缝扩展
信号分类
波形分形
频谱特征
bridge engineering
UHPC
AE
crack propagation
signal classification
waveform fractal
frequency spectrum characteristic
