Nondestructive Testing Method Of Bolt Anchorage Quality Based On PCA And FRF

Bolt support is an effective supporting technology,which is widely used in the field of engineering,such as mine,bridge and tunnel.Therefore,it is a necessary and urgent task to detect the running state of the bolt and the degree of anchorage.The traditional static load testing method has a destructive effect on the bolt,and it is also difficult to meet the needs of large area detection in the project.The subject is based on stress wave reflection method for nondestructive testing of anchor quality.The Frequency Response Function(FRF)has the advantages of more directness and less error.Therefore,in this paper,the FRF is used as the characteristic parameter of the anchor bolt model,and the damage is identified through the Multiple Control Theory.Finally,experimental analysis is conducted to prove the feasibility of the proposed method.The main work and conclusions of this article are as follows:(1)Study on propagation characteristics of stress wave reflection method in bolt,and the original data matrix,which can contain all the modal parameters propagating in the bolt,is obtained through the FRF.(2)Apply Multiple Control Theory to Identify Anchor Bolt Damage.Principal Element Analysis(PCA)is applied to the nondestructive testing of the bolt.PCA is used to get all the principal components of the original data and calculate the contribution rate of each principal component,so as to get the cumulative contribution rate of the front N order principal components,and compress original data.At the same time,the original data is reconstructed by the former N order principal element,and the noise reduction filtering of the original data can be realized.In this paper,the Multiple Control Theory(Elliptical control chart,T~2 control chart)is used to separate the abnormal data,so as to identify the damage of the bolt.(3)PCA and Mahalanobis distance were used to evaluate the degree of bolt damage.In the experiment,due to the influence of the environment and human factors,the results of the two measurements of the same bolt can not be zero.The Minimum Mahalanobis distance of the results of two measurements is calculated,and the damage exists when the distance is larger than that,and there is no damage to the distance less than that.This method can make up for the insensitive problem of the non destructive identification method proposed in this paper.(4)Design the signal acquisition circuit of non-destructive detection,and IEPE acceleration sensor is selected in this paper.The data is collected through the A/D conversion module of DSP(TMS320F28335).Finally,LabVIEW writes the human-computer interaction interface to analysis data and display waveform.In this paper,the parameter characteristics of bolts are obtained by the frequency response function,and the type of bolts is distinguished by the Multivariate control theory.Based on the DSP design non-destructive detector of bolt,analyzed and displayed by LabVIEW.