Meaning
Solid state components that convert electrical energy into mechanical vibrations and back again provide the basis for non destructive testing in manufacturing environments. A piezoceramic transducer uses materials that expand and contract in response to an applied voltage. This movement creates the ultrasonic waves that travel through a mould or a finished part to detect internal flaws.
When the returning wave hits the material, it generates a small voltage that the monitoring system records as data.
Energy Conversion
Conversion of electrical pulses into mechanical force is highly efficient in these materials. A piezoceramic transducer can generate high frequency waves that penetrate deep into reinforced polymers or thick sections of resin. The strength of the pulse depends on the ceramic composition and the voltage level of the excitation signal.
Frequency Response
Response characteristics of the device determine the resolution of the inspection. Higher frequencies provide better detail for detecting small cracks or bubbles but have less penetration depth in absorbing materials. A piezoceramic transducer is often designed for a specific resonant frequency that matches the material properties of the part being tested.
In injection moulding applications, these devices must operate at a frequency that can overcome the high attenuation of the molten plastic. They are usually housed in a protective casing to withstand the high pressures found inside the machine barrel or the tool cavity.
Mechanical Integration
Integration of the probe into the tooling requires careful consideration of the mounting pressure and the acoustic coupling. If the contact between the transducer and the tool is not stable, the signal quality will vary between shots.
