When solid PZT ceramic is activated (pulsed) it expands and contracts in the intended direction, but also in unintended directions.
Energy going the useless directions takes away from energy going in the useful directions.
The structure of 1-3 composite breaks up the energy going in the useless directions and points it in the direction of intended use.
This increases the efficiency from approximately 50% to 70%.
The result is more sensitivity and is seen by the user as deeper penetration into the part being inspected.
Sounds flows better between materials that have similar acoustic impedance (density x sound velocity in units of Mrayl).
The acoustic impedance of solid PZT (32 Mrayl) is very high compared to plastic (3 Mrayl) and water (1.5 Mrayl).
The structure of 1-3 composite reduces the impedance of the active material as much as 40% so that sound flows more freely from the composite to materials of lower acoustic impedance.
The result is a sound wave that rings less and has more bandwidth. The user sees it as better detection of smaller flaws.
Because grainy materials attenuate higher frequencies first, the return signal will be lower in frequency than the transmitted signal.
Higher bandwidth means that the probe will receive the lower frequency signal better than a low bandwidth transducer.
Since 1-3 composite is composed of up to 60% plastic, the shape can be modified after it is manufactured.
This makes curved and focused transducers easier and quicker to manufacture.
Solid PZT ceramics are brittle materials and prone to cracking and chipping.
The plastic in the composite structure absorbs impacts while protecting the ceramic that it surrounds.
Yes, but they can generally be overcome. That is where Vermon’s experience and expertise comes in. Here are the disadvantages and solutions.
1 – Higher sensitivity can lead to a longer dead zone in straight beam applications.
This can be overcome in many applications by designing probes that use any combination of appropriate transducer geometry, matching layer(s), backing material and focusing.
Having made transducers from 1-3 composite since 1985, Vermon has developed expertise in all of these areas.
2 – The plastic portion can be difficult to electrode, if the process of applying electrodes is not well developed, manufacturing yields from plating loss can be seen.
This is overcome with a well developed and well maintained process involving a high degree of cleanliness and process temperature control.
Vermon has been completing these processes in house since 1985.
3 – Material waste – since making composite is usually a subtractive process, up to 75% of the raw PZT material may be lost – lost material is captured by filtering and is properly disposed of – use or recycling of the captured material can be an area of research.