Study on the influence of rod bottom medium on stress wave behavior

The reflection at the bottom of the detection signal is weak, which affects the accurate identification of the signal at the rod bottom. The reflection intensity of the detection signal at the rod bottom is enhanced by adding to the ultrasonic insulating mediums （asphalt, rubber） at the rod bottom. According to the characteristics of the detection signal, such as amplitude, standard deviation, effective value and signal amplitude, the enhancement effect of different mediums at the rod bottom and the influence of different mediums on the stress wave behavior under the condition of graded load are analyzed, and the effectiveness of this method is verified by numerical simulation. The results show that adding asphalt or rubber to the rod bottom can enhance the reflected signal of the rod bottom during nondestructive testing. This method increases the amplitude, standard deviation and effective value of the stress wave, increases the strength of the detection signal, and can effectively improve the identification accuracy of the reflected signal of the bottom. The effective value and amplitude standard deviation of the detection signal will gradually decrease with the increase of the load applied to the anchor rod with different bottom mediums, and the consolidation wave velocity will increase by the increase of the axial load. In numerical simulation, the rod bottom mediums can increase the acceleration amplitude, reduce the energy attenuation, and the waveform characteristics are more obvious. There is a certain relationship between the reflected signal of the rod bottom and the elastic modulus of the medium of the rod bottom.