Ultraviolet excitation for thermography inspection of surface cracks in welded joints

Infrared thermography is a non-contact and full field inspection method which has proven to be suitable for automatic surface crack detection. For automatic analysis of the inspection results, a high signal-to-noise ratio (SNR) is required. In this paper an alternative excitation method, using ultraviolet (UV) illumination, is presented and evaluated. Artificial surface defects, so-called notches, in a titanium plate are detected both in the weld seam and in the heat affected zone. Notches with a size from 80 μm in width and 250 μm in length are detected. The SNR using UV illumination is compared with that using flash lamp excitation. The results show that UV illumination using a mercury lamp is a good alternative as excitation source for thermography when detecting surface cracks. To validate the excitation method, results from real surface cracks are included.

[1]  Antonino Squillace,et al.  The use of infrared thermography for nondestructive evaluation of joints , 2004 .

[2]  Patrik Broberg,et al.  Possibilities and Limitations of Automated Non-Destructive Testing of Welds , 2012 .

[3]  Christiane Maierhofer,et al.  Defect sizing by local excitation thermography , 2011 .

[4]  Suneet Tuli,et al.  LED optical excitation for the long pulse and lock-in thermographic techniques , 2013 .

[5]  B. Raj,et al.  Non-Destructive Testing of Welds , 1999 .

[6]  D. Dădârlat,et al.  Depth estimation of surface cracks on metallic components by means of lock-in thermography. , 2013, The Review of scientific instruments.

[7]  Patrik Broberg,et al.  Surface crack detection in welds using thermography , 2013 .

[8]  Peter Cawley,et al.  Prediction of the thermosonic signal from fatigue cracks in metals using vibration damping measurements , 2007 .

[9]  Comparison of NDT–methods for automatic inspection of weld defects , 2015 .

[10]  Steve Dixon,et al.  Thermographic detection of surface breaking defects using a scanning laser source , 2011 .

[11]  A. Abdel-azim.  Fundamentals of Heat and Mass Transfer , 2011 .

[12]  Wilhelm Satzger,et al.  Thermographic crack detection by eddy current excitation , 2007 .

[13]  Detection of Surface Cracks in Welds using Active Thermography , 2012 .

[14]  P. Cawley,et al.  Eddy-current induced thermography—probability of detection study of small fatigue cracks in steel, titanium and nickel-based superalloy , 2012 .

[15]  W. Arnold,et al.  MECHANISMS AND MODELS FOR CRACK DETECTION WITH INDUCTION THERMOGRAPHY , 2008 .

[16]  Gui Yun Tian,et al.  Thermographic techniques for the detection of cracks in metallic components , 2011 .