Pre processing of ultrasonic signals austenitic stainless steel weld at high temperature

Abstract

Abstract Time of flight Diffraction technique is an advanced ultrasonic NDE method, adopted in weld integrity testing. A better testing is being sought, particularly at elevated temperatures. With the suitable high temperature probes, the ultrasonic ToFD testing can be used at elevated temperatures also. The nature of weldment always plays an important role in assessment of weld integrality. High temperature ToFD testing of Austentic stainless steel weld testing yields a less Probability of Detection due to the noise added to ultrasonic signal at high temperatures. Hence, signal denoising is an essential prerequisite for the successful application of TOFD testing. In this work, one austenitic stainless steel weldment was artificially induced with slag defect. At high temperatures, the TOFD testing has been conducted on the weld piece and the resultant signals are applied over the proposed algorithms. Various combinations of wavelets, decomposition levels with different thresholding levels are applied to select an optimum denoising method. The evaluation of wavelet based denoising is achieved by calculating the SNR. Results show that the noises can be suppressed well and SNR is improved.