Testing Turbine Disks Non-Destructively With Dual Array Ultrasonic...

Testing Turbine Disks Non-Destructively With Dual Array Ultrasonic Transducers

Manufacturing Technology Insights | Monday, June 27, 2022

The influence of relative position between the planar defect and acoustic source has been analysed. Based on this, the transmission and reception algorithm for the dual array method has been proposed.

FREMONT, CA: A crucial part of the aero engine is the superalloy turbine disc. Diffusion flaws are easily created on the welding interface due to factors including surface roughness and impurities during the welding process, putting the robustness of the aero-engine in danger. These flaws – which differ from volume defects like holes and pores in that they are planar defects – are challenging to find since the proximity of the defects to the ultrasonic transducers will have a significant impact on the detection outcomes. The transmitting transducer may have trouble picking up the echo signal if the sound beam's incidence direction is not parallel to the planar flaw. The turbine disc structure has led to this significant limit. Additionally, the space available for the transducer arrangement is constrained by the intricate structure of the tested superalloy turbine disc. The traditional monolithic transducer pulse reflection approach is currently the most widely utilised detection technique. The acoustic waves would travel throughout the disc using this technique. As a result, the defect echo has a low signal-to-noise ratio and poor detection resolution.

Ultrasonic array beam is more adaptable and adjustable than traditional monolithic transducers. For the inspection of objects, it may scan in several directions and angles. This can significantly lower the defect missed rate and increase the accuracy of the detection. The delay law, which refers to the process of firing array components in correctly time-delayed pulses, makes it possible to change the focus depths and steering angles of sound beams, which enhances the detection of imaging flaws. The detection of low-pressure turbine discs, jet engine turbine blades, corner-shaped components, and welds in blade specimens are only a few examples of the uses of the ultrasonic phased array technology that have been studied in the past. To examine the stress corrosion cracking of the tenon teeth in the low-pressure turbine disc, used a phased array ultrasonic technique. The detection capacity and resolution are enhanced by this technology. To find the cracks in the low-pressure turbine disc and gauge their depth, Yang et al. combined phased array ultrasonic testing with artificial neural network techniques. The Rene 95 board has a flat-bottomed hole with a diameter of 0.254 mm and a buried depth of 3.18 mm, which the General Electric Company can see using an ultrasonic microscope. These investigations have shown a good ability to detect minor flaws, but their inspection efficiency is poor because they can only look at surface flaws. The majority of the identified objects are plate structures, not complex structures, even though time-of-flight diffraction, total focusing method, TFM15, ultrasonic phased array technology, etc. have all been employed in planar defects examination. To strengthen the safety and quality requirements of the superalloy disc, the non-destructive testing (NDT) method needs to be further enhanced to defect smaller flaws in complex structures.

For the novel method, a related synthetic acoustic beam transmission-reception algorithm is created. Numerical simulation is used to simulate the unique method's applications for a variety of fault depths. The outcomes of the simulation were confirmed by an experiment. It implies that the unique dual array approach may be employed in various fault depths and effectively increase the efficiency and accuracy of detection for the superalloy turbine disc.

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