Non-Destructive Evaluation of Embedded Cracks in Metal by Ultrasound: Experimental Investigation

Abstract

Embedded cracks of different type of samples of mild steel gas pipe API 1104 were identified and sized using Non-destructive evaluation. A procedure to create these embedded cracks inside the sample was developed. The UH-F1000knX hydraulic universal testing machine was used for bending and arc welding was done for bidding. 21 samples of different thickness and crack size were physically made. They were machined in shaper and grinding machine. A special reference slit of known deformity size was made to calibrate the ultrasonic testing machine’s sensitivity. EPOCH-650 ultrasonic testing machine was used to identify and measure these defects. Both normal and shear waves were used. Contact probe was used. Using the fabricated reference slit 4 different curves of deformity size (mm) vs Eco amplitude (%) were developed. Each of them provided a 3rd-degree polynomial equation. Amplitude Comparison Technique (ACT) and Amplitude Distance Differential Technique (ADDT) was used to size the deformities. For each shear wave an eco-amplitude (%) vs constant (c) curve was developed. Validation was done by destructive testing. For identifying deformities, around 95% accuracy was obtained and for sizing the deformities almost 60% accuracy was obtained. 35° and 45° shear waves gave 72% and 43% accurate data respectively.