DescriptionIn this work three-dimensional (3D) thermographic defect reconstructions of composite materials based on the virtual wave concept (VWC) are presented. The intention of VWC-concept is to combine the two nondestructive evaluation methods thermography and ultrasonic testing. It has the following advantages: complex shaped components can be tested contactless using an infrared-camera for surface temperature data acquisition and ultrasonic reconstruction methods, such as the frequency domain focusing aperture technique (F-SAFT), can be employed for 3D thermographic imaging. The VWC is a two-step reconstruction method. In the first step, the surface temperature signal of a thermally stimulated specimen is measured. Based on this signal a so called virtual wave field is calculated. In the second step, inverse wave propagation methods such as F-SAFT are applied on the virtual wave field to calculate the initial temperature distribution. The transformation of the surface temperature field into a virtual wave field is an ill-posed inverse problem. Therefore, the iterative regularization method, called alternating direction method of multipliers (ADMM), is applied to compute an appropriate regularized solution and virtual wave field, respectively. In the present work the performance of VWC considering a carbon fiber-reinforced polymers specimen with flat bottom holes is shown. Moreover, a three-dimensional defect reconstruction of a wood plastic composite material, obtained via VWC, is compared with the results obtained via computer tomography.
|Period||17 Sep 2019|
|Event title||15th International Symposium on Nondestructive Characterization of Materials|