Non-collinear Mixing Technique Research Articles

A non-collinear mixing technique to measure the acoustic nonlinearity parameter of an adhesive bond from one side of the sample

he Acoustic Nonlinearity Parameter (ANLP) of adhesive bonds. One of the most significant features of the new method is that it requires only one-side access to the adhesive bond being measured, which significantly increases its utility in field measurements. To demonstrate the effectiveness of the newly developed technique, an adhesively jointed aluminum sample was measured with different heat loading time, using the non-collinear mixing technique with a longitudinal and a shear wave as incident waves to obtain the ANLP of the adhesive bond. The measured results clearly show that the ANLP varies with aging time. To verify that the signals received from the shear wave receiver are indeed the mixed wave, the finite element method was used to simulate the wave motion in the test sample. The simulation results clearly show that the signals recorded by the shear wave receiver are the desired mixed wave, whose amplitude is proportional to the ANLP of the adhesive bond.

2D finite element modeling of the non-collinear mixing method for detection and characterization of closed cracks

The non-collinear mixing technique is applied for detection and characterization of closed cracks. The method is based on the nonlinear interaction of two shear waves generated with an oblique incidence, which leads to the scattering of a longitudinal wave. A Finite Element model is used to demonstrate its application to a closed crack. Contact acoustic nonlinearity is modeled using unilateral contact law with Coulomb׳s friction. The method is shown to be effective and promising when applied to a closed crack. Scattering of the longitudinal wave also enables us to image the crack, giving its position and size.

The use of non-collinear mixing for nonlinear ultrasonic detection of plasticity and fatigue

This letter reports on the application of the non-collinear mixing technique to the ultrasonic measurement of material nonlinearity to assess plasticity and fatigue damage. Non-collinear mixing is potentially more attractive for assessing material state than other nonlinear ultrasonic techniques because system nonlinearities can be both independently measured and largely eliminated. Here, measurements made on a sample after plastic deformation and on a sample subjected to low-cycle fatigue show that the non-collinear technique is indeed capable of measuring changes in both, and is therefore a viable inspection technique for these types of material degradation.