It is not a new idea in NDT to use non-contactly without couplant
generated Lamb waves (or guided waves) for testing of plate materials.
The unit is packaged in a compartmentalized and padded carrying case along with the transducer set, a 20-ft interconnection cable, one tube of acoustic couplant
, and mounting hardware.
Each sticker protruded slightly from the load and had attached (using a constant force spring) an AET175 kHz transducer, using grease couplant
In the contact method (also known as the pulse-echo method), an ultrasonic probe (transducer) is pressed against the casting surface with a couplant
to maintain a good contact between the casting and the transducer, which sends and receives sound signals.
The method was fast, simple, and did not require a liquid couplant
to transmit the waves.
Each model includes a transducer assembly, interconnecting cable, couplant
, rechargeable battery pack, universal mains supply, metal case, and instruction manual.
But ultrasonic tools cannot be used at all because of the absence of couplant
in the pipeline.
Using water as a couplant
, the ultrasonic, nondestructive tool "looks under the skin" of aircraft fuselages and wings for corrosion, bonding failures, and other defects.
Some of the topics covered included the relative cost-effectiveness of viscosity-reducing surface treatments on alumina trihydrate (ATH) of different particle sizes; effectiveness of different grafted polyolefins in coupling glass and PP; surface-treated microspheres as polymer blend compatibilizers; reground thermosets as low-cost fillers in polyolefins; property enhancement through coupling of natural cellulose-derived fillers in thermoplastics-including recycled materials; and a simple, new method of calculating how much couplant
is just enough.
An advanced lift-off algorithm allows scanning in real world situations such as variations in paint thickness, surface roughness and other causes of lift-off and as with all eddy current equipment, inspections can be carried out with no need for direct contact with the material and with no need for couplant
The UT pig was then propelled using base oil which serves as a couplant
in ultrasonic testing.
through piezo-electric transducers requiring a liquid couplant
or electro-magnetic acoustic transmission (usually referred to as EMAT) which can also be applied in a gas environment.