Research On Nondestructive Testing Technology Of Measuring Bolt Length Based On Sterss Wave Method

China's infrastructure construction has developed rapidly since the reform and opening up,Chinese people have made great progress in mining,dams,tunnels,bridges,deep foundation pits and other projects.The use of anchor bolts is also rising in the context of such a large-scale project in our country.In China,only the bolts used in the roadway are more than 10 millions per year.Whether the construction quality of each anchor is effective that not only affects the overall project quality,but also affects the safety of people.Therefore,the bolt detection technology is a sword that guarantees safe.There are two current anchor detection techniques,one for lossy detection and the other for non-destructive testing.The lossy detection operation is complicated,the workload is large,and the overhead is huge,so it has been phased out in recent years.The non-destructive testing method has been favored by people for its fast,accurate and at the same time ensuring the overall safety and stability of the project.The non-destructive testing technology has also developed rapidly.The stress wave is a technology and method that has been rapidly developed and applied in nondestructive testing technology in recent years.The propagation data of the stress wave in the anchor is collected by the excitation vibration of the free end of the anchor,comprehensive evaluation of anchor engineering by means of time-frequency analysis of digital signals of stress wave signals.This paper designs an automatic,intelligent,simple and fast bolt length measuring instrument based on stress wave method by useing stress wave technology,it can reduce the cost,effectively reduce the measurement difficulty of the bolt,and improve the overall safety and stability of the project.According to the measured results,the measurement error of the bolt length of the instrument is less than 3%,it plays an important role in the anchorage detection of anchors.The paper makes a detailed analysis and elaboration on the realization process of the anchor length nondestructive detector,including the following aspects.The basic principle of anchor anchoring and the one-dimensional model of anchor are analyzed.The propagation law of longitudinal wave on one-dimensional model of anchor and the attenuation model of stress wave on one-dimensional model of anchor is discussed.Based on the theory of anchor stress wave theory and bolt anchorage detection engineering,a set of software and hardware solutions is proposed,and the optimal hardware platform is selected.According to the knowledge of analog,digital and embedded,and digital signal processing,hardware platform construction and function realization,wherein the hardware platform includes a main control module,a stress wave acquisition module,a multi-chip data interface,a pre-trigger module,etc.then software is written for each module,and a detailed analysis of the driving and control process is performed;Through the stress wave anchor length detection principle and digital signal processing theory,the wavelet denoising algorithm and the matlabGUI software platform are used to realize the upper machine stress wave data processing and graphical interface display;Then through the instrument measurement,the performance parameters of the design are tested and compared to verify the basic electrical performance of the instrument.The data link analysis proves the correct of the data link of the instrument,and finally through several actual engineering test comparisons.Verify and evaluate the accuracy of the instrument in bolt detection.