Intermodal TFM with Applications to Weld Inspections
Many different types of ultrasound scans exist, which are commonly used and accepted. Each method has its own detection limitations and when the industry introduces a new scan type, it will be to overcome intrinsic ultrasound physics issues.
The introduction of total focused imagery (Total focusing Method: TFM) in the non-destructive testing field has improved many procedures. Most of the current phased array and TFM techniques are based on single-mode sweeps, which resolve specific inspection challenges. Among the available propagation modes, each one of the TFM scans is likely to be amplitude-sensitive with regard to the nature of its recorded defects. TFM indeed improves the resolution and amplitude response when the appropriate mode has been chosen. By deploying the latest electronic and software technologies, it is possible to combine several TFM scans and construct an inter-mode image from one acquisition frame. This approach is supported by common mathematical algorithms and existing TFM strategies. To point out this new type of inspection, we will call it TFM Inter-mode (TFMiTM). The article will describe its proof of concept and a study on natural weld defects, namely lack of fusion, cracks, and porosities. There are recognized advantages of the combined TFM technique, but additional considerations will be brought to light in this article.
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