COMPARATIVE ANALYSIS OF USING COUPLING FLUIDS IN FLAW DETECTION ON THE EXAMPLE OF ULTRA-SOUND CONTROL OF AN ALL-ROLLED WHEEL SURFACE

Abstract

Coupling fluids are important flaw detection materials that are used during ultrasonic testing in order to find out acoustic contact between the piezoelectric transducer and the object of control. The paper considers coupling fluids of various viscosities that can be used as a coupling medium for ultrasonic flaw detection. A comparative analysis of the effect of the studied coupling fluids on the sensitivity of the control is carried out, which is determined by the attenuation of the transmitted ultrasonic signal through the roll surface of the car wheelset wheel. The control sensitivity is assessed on the flat and inclined surfaces of the all-rolled wheel. The introduction of ultrasound into the wheel material (steel 2) is carried out by an inclined piezoelectric transducer at an angle α = 900, with an oscillation frequency f = 0.4 MHz. It is found out that by providing a reliable constant force of the ultrasonic transducer P121-90-0.4 due to the permanent magnets built into it, an increase in the viscosity of the coupling fluid can significantly affect the amplitude of the received echo signals. During the research, it is found that low-viscosity coupling fluids are characterized by stable coupling regardless of the time and clamping force of the transducer, in contrast to high-viscosity coupling media, when using them sharp fluctuations in the overall gain of the second through signal in AGC zone are observed on the flaw detector screen. Therefore, in practice, the use of high-viscosity coupling media leads to a sharp increase in signal amplification (amplitude), which may result in over reject.