Cast metal parts are extensively used in many industries and applications such as pump casing and blades, engines, piping and pipeline flanges, and rail wheelsets. Thermal effects during the cast manufacturing processes such as solidification and cooling can cause the generation of different types of defects in the components. Depending on the size of the cast parts and rate of solidification, the grain structure of these materials can also be significantly influenced. Nondestructive evaluation and inspection of cast parts is necessary for quality assurance and defect detection of these materials. Effective detection and sizing of defects and anomalies in cast manufactured parts prevent extra cost and time associated with repair and maintenance. Surface breaking cracks and porosity are among the most common types of defects in large cast components.  Surface breaking cracks are often visible on the surface or can be easily detected on the surface using dye penetrant testing or magnetic particle testing. There are several limitations encountered when using conventional methods of nondestructive inspection for as-built cast parts due to surface conditions, coarse-grain structure, and characteristics of potential defects. Magnetic particle testing is not a practical option in filed testing condition and dye penetrant testing can only show the cracks on the surface without much information regarding the depth of the crack into the material. While using conventional ultrasonic testing, extra machining is usually needed to be able to detect the possible defects such as cracks and porosity in cast parts due to the rough surface conditions. In addition, the coarse-grain microstructure causes high attenuation in the propagation of ultrasound waves. The use of low-frequency ultrasound wave decreases the attenuation of waves, however increases the minimum detectable size of defect as well. Ultrasonic adaptive imaging based on the phased-array technology is proposed for coarse-grain heavy walled cast material inspection. The Phased Array Ultrasonic Testing (PAUT) and Time of Flight Diffraction (TOFD) technologies have made significant improvements in inspection and reliability in various industries. Ultrasonic phased array is an advanced technology that offers considerable potential for inspecting cast parts. The capability of aperture focusing on phased array ultrasonic methods provides the opportunity for the adjustment of the delay laws in ultrasonic beams and reduces the noise and beam distortion for better imaging results. Using electronic control of the beam, phased arrays can scan, sweep, steer and focus the ultrasound. Considering the advantages of PAUT for inspection and testing of the materials, a comprehensive understanding of the ultrasonic beam focusing setup and selection of appropriate transducer considering the number and arrangement of piezoelectric elements and the right angle wedges is necessary. Aluminum and iron cast samples having both operational defects (cracks generated during the lifetime of components) and artificially made defects (EDM notches representing surface breaking and ID cracks) were successfully inspected using the Phased Array Ultrasonic Testing (PAUT). Unlike conventional ultrasonic techniques, results show a promising way to provide inspection for as-built cast parts with rough surface finish conditions. The proposed method helps to decrease the inspection time and eliminate extra machining and preparation costs. Enhanced defect sizing approach provides useful information for repair and maintenance decision making such as the amount of material grinding and post-welding procedure.


Ultrasonic Phased Array Technique for Defect Detection and Sizing in Heavy-Walled Cast Components

Division / Sponsors: 
Aerospace, Bioengineering, Applied Mechanics, Design Engineering Division, Advanced Energy Systems, Manufacturing Engineering Division, Noise Control and Acoustics, Nondestructive Evaluation, Diagnosis, and Prognosis (NDPD), Nuclear Engineering Division, Process Industries Division, Fluids Engineering, Heat Transfer, Materials, Microelectromechanical Systems, Safety Engineering and Risk Analysis, Computers & Information in Engineering


Paper Proceedings: https://asmedigitalcollection.asme.org/IMECE/IMECE2020/volume/84478

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