Non destructive testing of materials are crucial for ensuring quality and safety in the use of
various mechanical parts. Most testing’s are made on already used parts, welded sheets and
through various coatings of paint and other protections. When inspecting welds we are most
successful with phase array ultrasonic testing technique which allow us to observe the
material from different angles. Since more and more inspections are carried out on parts
already in use and therefore coated with different thicknesses of anticorrosion protection, it
is necessary to determine the influence of the coating thickness on testing results and
differences when using different ultrasonic probes with different properties. From the results
we learn that higher coating thickness increases ultrasound attenuation which is why we need
to increase registration gain to detect material defect. We learn that ultrasound attenuation is
bigger and ultrasound penetration is smaller when using probes with higher frequencies.
However the resolution of defect detection is better using higher frequency probes.
Inspection signal depends on type of defect and its shape. Reflected wave of defects with
straight edges is better than inspecting curved defect surfaces. The size of the individual
probe and its wedge also plays important role in testing and affects the length of the sound
path and accessibility when inspecting different machine parts.
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