_applied sciences_  
_Article_  
**Waveguide Structure Design and Simulation for High-Temperature Corrosion Thickness Detection**  
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**Featured Application: The paper designed an optimized waveguide structure for ultrasonic testing even at a high temperature 500 deg C. With the waveguide structure, an ultrasonic-guided wave testing device was developed. Measurement error increases with temperature if the wave velocity is regarded as a constant. A temperature-dependent method was applied to achieve high precision detection at high temperatures. **  
**Abstract: Equipment corrosion often happens in the petrochemical industry, especially when high temperature materials are transported. The corrosion phenomenon should be monitored as a leak may occur due to corrosion and even cause fires and explosions. However, ordinary ultrasonic testing is not suitable for high temperature conditions because the probe may break. A waveguide structure was designed to economically detect corrosion thickness even at a high temperature 500 deg C and avoid the failure of the ultrasonic probe. Based on the heat transfer simulation, a waveguide rod was determined with optimized material, length, width and thickness, and the experiment validated the calculated result. Then, ultrasonic propagation through the designed waveguide rod and specimen was simulated. Propagation, reflection, attenuation and dissipation of the ultrasonic wave within the combined structure were displayed. A clear ultrasound signal was found near the center, while signal attenuation and dispersion occurred as it is gradually far away from the center. With the waveguide structure, an ultrasonic-guided wave testing device was developed to measure the thickness at high temperatures. Measurement error increases with temperature if the wave velocity is regarded as a constant. A temperature-dependent method was applied to achieve high precision detection at high temperatures. The research has good application potential for the corrosion detection of high-temperature equipment. **  
waveguide rod; high-temperature detection; heat transfer simulation; ultrasonic-guided wave testing; thickness measurement  
**1. Introduction**  
Oil and gas pipelines have a pivotal role in national economic development. However, corrosion issues can effectively diminish wall thickness, resulting in pipeline leakage and even explosion accidents. To guarantee the smooth and secure operation of the equipment, engineers pay close attention to the corrosion of hardware and the reduction in pipe thickness. Frequent detection is necessary to avoid security incidents. Therefore, pipeline corrosion detection has resulted in being imperative. The traditional method is to determine the specific corrosion situation of the pipeline by measuring the thickness of the pipe wall and analyzing the relevant information. In recent years, magnetic flux leakage detection, eddy current detection and ultrasonic-guided wave detection technologies have been widely used in pipeline corrosion detection at home and abroad [1; 2]. Magnetic flux leakage (MFL) detection is less costly and can detect the whole circumference of the pipe, but it is prone to untrue signals amid the detection process and has low sensitivity [3; 4; 5]. Eddy current detection can be sensitive to automatic detection of pipeline defects, but the actual depth of detection conflicts with its sensitivity [2; 6; 7]. Ultrasonic-guided waves have the advantage of single-point excitation, long propagation distance and low attenuation. In addition, they are capable of accurately locating the corrosion site and covering a large area. Therefore, ultrasonic-guided wave testing (UGWT) is widely used for corrosion detection of large diameter thick-walled oil and gas pipelines [8; 9; 10]. UGWT can also be combined with the concept of structural health monitoring. [PERSON] et al. [11] developed a guided ultrasonic wave array to monitor structural integrity. [PERSON] et al.