基于敲击法的碳纤维板加固钢梁脱粘检测研究

Debonding detection of steel beams reinforced by carbon fiber-reinforced polymer plates by the percussion method

碳纤维板与钢梁之间的界面连接情况影响着钢梁的加固效果以及承载性能的发挥,为更好地判别脱粘病害,探究出一种有效的界面脱粘位置定性识别方法。首先制作碳纤维板加固钢梁后的未脱粘试件和脱粘试件,然后通过采用局部敲击指定位置的方法来获取声音信号,并采用Welch功率谱密度(PSD)估计法和快速傅里叶变换(FFT)分析声音信号中的频谱特征。结果表明:从低阶振动频率范围0~500 Hz来看,PSD估计法的2条曲线峰值差别明显,存在脱粘损伤部位的PSD曲线峰值处频率较正常部位处峰值对应频率明显向0偏移,从工况1 PSD曲线中提取得到的平均一阶振动频率从定量的角度揭示出脱粘损伤部位与正常部位频率的变化,这与界面脱粘后局部刚度降低有关;与传统常用的FFT损伤定位方法相比,PSD曲线峰值相比FFT曲线峰值差异性更大,更容易判别出该位置是否发生了脱粘损伤。文章还探究不同属性锤头对试验结果的影响,为实际工程提供有效的参考。

The interface connection between carbon fiber-reinforced polymer(CFRP)plates and steel beams has an influence on the reinforcement effect and bearing performance of steel beams.To better determine problems regarding debonding,an effective approach to qualitatively identi-fying the interface debonding position was examined.In this study,the bonding and debonding specimens of CFRP plate-reinforced steel beams were fabricated.Sound signals were acquired by locally knocking on specified positions,and then,Welch power spectral density(PSD)estimation and fast Fourier transform(FFT)were employed for analysis of the spectral characteristics of sound signals.The findings exhibited that the difference between the peak values of two curves from the Welch PSD estimation is distinct within the low-order vibration frequency range of 0-500 Hz,and the frequency at the peak of the PSD curve with debonding damage is obviously shifted to zero compared with the corresponding frequency at the normal part.The average first-order vibration frequency extracted from PSD curves under the first working condition quantitatively shows the change in frequencies at the debonding damage and normal parts,which corresponds to the decrease in local stiffness after debonding.Compared with the traditional FFT damage location method,the peak values of the PSD curves are greatly different from those of the FFT curves;therefore,it is easier to determine whether the debonding damage has occurred at the position.Moreover,the influence of hammerheads with different attributes on the experiment results was investigated,thus providing a reference for practical engineering.