Ultrasonic Wave Attenuation Basics for Paperboard Creasing Quality
Non-destructive ultrasonic wave attenuation evaluates paperboard crease quality by measuring acoustic energy loss caused by internal shear delamination.
Transducer Frequency Selection
Operating Parameter
Non-destructive acoustic testing of paperboard substrates requires matching the acoustic signal wavelength to the microscopic structure and caliper of the moving web. In ultrasonic stiffness and elasticity measurement, transducer frequency selection governs the balance between acoustic wave penetration depth and spatial resolution within anisotropic cellulose networks. The chosen frequency dictates the system’s ability to measure out-of-plane elastic constants and identify internal structural defects without excessive signal damping or background noise.
Substrate Interaction
Cellulose networks act as complex viscoelastic scattering media that attenuate high-frequency acoustic waves through internal friction and pore scattering. Proper transducer frequency selection matches the ultrasound wave profile to the specific paperboard grade under test. Low-frequency transducers operating between fifty and two hundred kilohertz produce long wavelengths suitable for thick, porous corrugated containerboard and heavyweight solid unbleached kraft grades, ensuring full web penetration despite heavy acoustic scattering.
High-frequency transducers operating between one and five megahertz deliver short wavelengths necessary to resolve out-of-plane transit times and localized micro-defects in lightweight, dense coated folding boxboard. Selecting an excessively high frequency leads to total signal loss within porous core plies, whereas an excessively low frequency generates wide acoustic pulses that cannot resolve thin calipers.
Acoustic Calibration
Accurate determination of dynamic elastic stiffness constants in machine, cross, and thickness directions relies on clean signal reception. Calibrating transducer frequency against board density and moisture content ensures reproducible acoustic velocity measurements across high-speed packaging converting and paper mill inspection systems.