Ultrasonic C-scan detection for stainless steel spot welding based on wavelet package analysis

Abstract

An ultrasonic test of spot welding for stainless steel is conducted. Based on wavelet packet decomposition, the ultrasonic echo signal has been analyzed deeply in time - frequency domain, which can easily distinguish the nugget from the corona bond. The 2D C-scan images produced by ultrasonic C scan which contribute to quantitatively calculate the nugget diameter for the computer are further analyzed. The spot welding nugget diameter can be automatically obtained by image enhancement, edge detection and equivalent diameter algorithm procedure. The ultrasonic detection values in this paper show good agreement with the metallographic measured values. The mean value of normal distribution curve is 0.006 67, and the standard deviation is 0.087 11. Ultrasonic C-scan test based on wavelet packet signal analysis is of high accuracy and stability.

Keywords

stainless steel / spot welding / ultrasonic test / wavelet package analysis / nugget diameter

References

[1] Nied H. The Finite Element Modeling of the Resistance Spot Welding Process[J]. Weld. J., 1984, 63(4): 123-132.

[2] Jou M. Real Time Monitoring Weld Quality of Resistance Spot Welding for the Fabrication of Sheet Metal Assemblies[J]. Journal of Materials Processing Technology, 2003, 132(1): 102-113.

[3] Aslanlar S. The Effect of Nucleus Size on Mechanical Properties in Electrical Resistance Spot Welding of Sheets Used in Automotive Industry[J]. Materials & Design, 2006, 27(2): 125-131.

[4] Aslanlar S, Ogur A, Ozsarac U, et al. Effect of Welding Current on Mechanical Properties of Galvanized Chromided Steel Sheets in Electrical Resistance Spot Welding[J]. Materials & Design, 2007, 28(1): 2-7.

[5] Bayraktar E, Kaplan D, Buirette C, et al. Application of Impact Tensile Testing to Welded Thin Sheets[J]. Journal of Materials Processing Technology, 2004, 145(1): 27-39.

[6] Ditchburn R J, Burke S K, Scala C M. NDT of Welds: State of the Art [J]. NDT & E International, 1996, 29(2): 111-117.

[7] Mansour T M. Ultrasonic Inspection of Spot Welds in Thin-Gage Steel[J]. Materials Evaluation, 1988, 46(5): 650-658.

[8] Maev R G, Ptchelintsev A, Denissov A A. Ultrasonic Imaging with 2D Matrix Transducers[J]. Acoustical Imaging, 2002, 25: 157-162.

[9] Shi L F, Zheng X M, Shi Y W. Ultrasonic C-Scan Testing for Determining the Spot Size of the Resistance Spot Welding in Aluminum Alloy[J]. Nondestructive Testing, 2004, 26(1): 34-36.

[10] Thornton M, Han L, Shergold M. Progress in NDT of Resistance Spot Welding of Aluminium Using Ultrasonic C-Scan[J]. NDT & E International, 2012, 48: 30-38.

[11] Neves J, Loureiro A. Fracture Toughness of Welds-Effect of Brittle Zones and Strength Mismatch[J]. Journal of Materials Processing Technology, 2004, 153: 537-543.

[12] Nguyen T N, Wahab M A. The Effect of Weld Geometry and Residual Stresses on the Fatigue of Welded Joints Under Combined Loading[J]. Journal of Materials Processing Technology, 1998, 77(1): 201-208.

[13] Strang G. Wavelet Transforms Versus Fourier Transforms[J]. Bulletin of the American Mathematical Society, 1993, 28(2): 288-305.

[14] Daubechies I. The Wavelet Transform, Time-Frequency Localization and Signal Analysis[J]. IEEE Transactions on Information Theory, 1990, 36(5): 961-1 005.

[15] Kaya K, Bilgutay N M, Murthy R. Flaw Detection in Stainless Steel Samples Using Wavelet Decomposition[J]. IEEE Ultrasonics Symposium, 1994, 2: 1 271-1 274.

[16] Luan Y L, Feng J C, Gang T. Ultrasonic Evaluation of TiAl and 40Cr Diffusion Bonding Quality Based on Time-Scale Characteristics Extraction[J]. NDT & E International, 2011, 44(8): 789-796.

[17] Chao Y J. Failure Mode of Spot Welds: Interfacial Versus Pullout[J]. Science & Technology of Welding & Joining, 2003, 8(2): 133-137.