This image depicts the setup for infrared testing of lap joints.  The images below are of a such a lap joint with a three poor spot welds in the middle.

Here is the raw thermographic data.

Here is the same data after removing the noise and vertical gradient.

Here is the same data processed for the local gradient in surface temperature.

The above series of images from thermographic data show that sophisticated postprocessing of the raw data offers advantages in identifying good spot welds from poor ones.  Processing the matrix data with FFT algorithms and numerical differentiation brings out important details that are hidden in the raw infrared data.  The strong change in the surface temperature gradients at the two spot welds on the outside corresponded to high strength welds.  The location of the three spot welds in the middle can be determined and the weak temperature gradients correspond to low strength welds. 

Recent publications related to NDE research performed at the IRLab include:

D. Hopkins, S. Nakagawa, K. Nihei and D. Turler, 1997. Imaging Flaws in Adhesive Joints Using Acoustic Techniques and Infrared Thermography. In Review of Progress in Quantitative Nondestructive Evaluation, Vol. 17.

D. Türler, D. Hopkins, S. Nakagawa, A. Valente, and K. Nihei, 1998. Thermographic and Acoustic Imaging of Spot-Welded and Weld-Bonded Joints. To appear in Review of Progress in Quantitative Nondestructive Evaluation, Vol. 18.

D. Türler, D. Hopkins, S. Nakagawa, A. Valente, and K. Nihei, 1998. Nondestructive Evaluation of Spot-Welded and Weld-Bonded Joints Using Acoustic and Thermographic Imaging Techniques. Submitted to the Society of Automotive Engineers.

For more information on Non-Destructive Evaluation research at the Infrared Thermography Laboratory contact:

Daniel Turler
Lawrence Berkeley National Laboratory
FAX (510) 486-6046