Forewords

In the field of industrial inspection, ultrasonic thickness measurement technology has become the core means of metal material thickness detection. YUSHI UM-5 series ultrasonic thickness gauge type as the domestic industry's first batch of mainstream thickness measurement equipment with A-scan, which is equipped with TC550 composite wafer probe and digital waveform analysis system, for the precision measurement of complex working conditions to provide a solution. In this paper, the equipment in the surface of the raised steel inspection practice as an example, the system analyzes the non-smooth surface of the technical challenges and breakthrough path.

A more serious challenge comes from the distortion of the acoustic wave propagation path. Irregular surface morphology triggers non-perpendicular incidence of the ultrasonic beam, resulting in significant acoustic scattering effects. As shown in the diagram, the mottled structure of the steel surface, where each protrusion can be a secondary source of sound, results in a multi-path superposition of the echo signal. This scattering phenomenon will make the measurement waveform "burr-like" interference, thickness reading fluctuations of up to ± 0.5mm.

The waveform displayed by the device visualizes this phenomenon: the main echo signal shows multiple tiny fluctuation peaks in the front section, which is a typical feature of multiple reflections of sound waves on rough surfaces. When there are small defects within the material, this waveform distortion will be further aggravated, bringing double interference to the identification of the true thickness value.

The Critical Path of Precision Technology

To address the coupling challenge, the first step is to remove the surface dust and floating rust, clean and apply a moderate viscosity coupling agent, and finally press the probe against the coupling agent.

In the waveform analysis session, the A-scan interface of UM-5 series is particularly important. By setting the parameters such as gain and muffler, the noise reflected from the surface can be effectively filtered out. When the 10.35mm main echo signal was detected in the figure, the reliability of the measurement data was verified by combining the steel longitudinal sound velocity of 5920m/s and the caliper measurement.

Developing the potential of equipment

The waveform recording function of the UM-5 series thickness gauges provides a new dimension for quality traceability. By storing the A-Scan waveform during measurement, a three-dimensional database of "surface morphology - waveform characteristics - thickness value" can be established. The application practice of a steel plant shows that after accumulating 200 sets of data, the accuracy of the equipment for the first measurement of similar conditions has increased to 98.6%.

In the case of coating, the penetrating coating mode (E-E) of the equipment can be enabled. The device automatically corrects the calculated value of sound range by two bottom surface echoes.