# Structural Health Monitoring of Walking Dragline Excavator Using Acoustic Emission
###### Abstract
Another way to detect the AE activity of a defect during the testing of the noisy structure is to design a scaled model of the testing structure. This method is successfully used for the AE testing of the various chemical reactors, absorbers, and crystallizers [11; 12]. Investigation of the scaled model of the test structure allows obtaining a pattern of acoustic noise, in this case the appearance of a defect can be detected as a change of regularity in the parameters of the reference noise signal. If it is impossible to design a model, the study of noise is carried out on the operating equipment. There are some papers devoted to the AE testing of handling equipment: cranes, lifts, and excavators [13; 14; 15; 16; 17]. However, as a rule, the testing of handling equipment involves a special low-speed loading program which provides a low noisy level. AE testing of a walking dragline excavator is a rather difficult problem, since it involves the testing of a large-sized structure in difficult weather conditions and at an extremely high noise level. This paper describes a method of design of a walking dragline excavator monitoring system based on the application of the AE method. A simplified block diagram of the monitoring system is shown in Figure 2. It consists of hardware part and software parts, the software parts in turn are divided into acquisition system and data analysis system. The hardware equipment is represented by a digital measuring system A-Line 32D DDM (produced by Interunis-IT company). Its main feature consists of subsequential connection of the measuring channels. A data acquisition system provides the traditional AE impulse threshold detection, calculation of AE parameters, and location of AE sources based on the determination of the difference in the time of arrival of AE impulses to neighboring sensors. The data analysis algorithm provides intelligent processing of AE data for detection of the defects against the background of high-intensity technological noise. In a preliminary analysis, the possibility of carrying out AE monitoring to assess the strain-stress state of the dragline components was studied by identification of favorable and adverse factors. The most unfavorable factor is a high level of noise in the dragline operating cycle. In most cases it is caused by the movement of the dragrope and hoisting ropes. Therefore, the high-intensity acoustic noise can reach 75 dB in the 100-400 kHz range. Despite this critical level, monitoring still can be performed because the sources of noise, as a rule, are not localized at certain points in the structure and are not identified on the diagram. The favorable factor is the waveguide form. The dragline structural components usually obtain the form of hollow pipelines and could be interpreted as a one-layered cylindric waveguide. In the absence of multiple reflections and scattering, the AE impulses have a relatively short rise time and duration, while providing a significant difference in the waveform of the useful and noise data. Figure 2: Block diagram of the structure health monitoring system.