# Structural Health Monitoring of Walking Dragline Excavator Using Acoustic Emission
###### Abstract  
The article is devoted to the organization of the structural health monitoring of a walking dragline excavator using the acoustic emission (AE) method. Since the dragline excavator under study is a large and noisy industrial facility, preliminary prospecting researches were carried out to conduct effective control by the AE method, including the study of AE sources, AE waveguide, and noise parameters analysis. In addition, AE filtering methods were improved. It is shown that application of the developed filtering algorithms allows to detect AE impulses from cracks and defects against a background noise exceeding the useful signal in amplitude and intensity. Using the proposed solutions in the monitoring of a real dragline excavator during its operation made it possible to identify a crack in one of its elements (weld joint in a dragline back leg). acoustic emission; structure health monitoring; walking excavator; AE impulse detection +
Footnote †: journal: Medical2015 to 2020, 15 accidents caused by breakage of back legs and five accidents caused by breakage of the dragline boom were registered in Russia. The most widely spread non-destructive testing (NDT) of dragline structural components is ultrasonic testing, which is carried out in the welded joints of an excavator twice a year. However, this method does not allow detect abrupt changes in the stress-strain state. Furthermore, it is extremely time-consuming and leads to long-lasting downtime. Draglines are commonly equipped with a structural health monitoring system with video supervision systems and an electrical equipment diagnostics system, but operational monitoring of the metal structures conditions is usually not performed. In this paper, the possibility of using the acoustic emission (AE) method to detect defects in the dragline metal structures is discussed. AE is a non-destructive testing (NDT) method based on the physical phenomenon of elastic waves emission when a material undergoes irreversible changes in its internal structure, for example, because of crack formation. The AE method has a high sensitivity to crack detection and is used to detect cracks at early stages of their growth. An important advantage of the AE method is the ability to detect defects located at a great distance from the control point; cracks and other defects emit AE waves, which propagate over the testing structure and can be detected by the AE sensors at about 10 m from the defect. The AE method is passive, it does not require probing action, which allows it to be effectively used in structural health monitoring systems for monitoring loaded structures in the operating mode without decommissioning. AE testing provides low noise immunity, therefore, such experiments are traditionally carried out for equipment when the operation of equipment is suspended. Recently, the technology of AE monitoring which requires the use of specific methods for detecting AE signals against a noise background has become more popular [3; 4; 5]. AE monitoring is performed for both statically and dynamically loaded equipment. Most widespread application of AE testing in the operating mode is testing of bearings, compressors, and pumps [6; 7; 8]. The various defects have a specific AE signature with a certain periodicity connected with a rotation frequency. The periodicity analysis allows to recognize the AE activity against the noise process. Some of the most complicated structures for AE structural health monitoring are railways and roads bridges [9; 10]. The complicity consists of the fact that trains and cars are oftentimes a noise source and a load excitation, and the moment of passage of vehicles is simultaneously the moment of the most probable occurrence of AE activity. Solving of this problem is achieved by reducing the distance between AE sensors,  
Figure 1: Basic components of a dragline ESH-20.90: 1—back legs, 2—boom, 3—hoist rope, 4—mast, 5—bucket, 6—dragrope. high-frequency filtration, and using additional strain gauges or vibration measurements.