Advanced Ultrasound Technique by the Total Focusing Method for the identification and characterization of defects

Inspenet, August 17, 2023. The Total Focusing Method (TFM) is based on the same targeting and focusing methodology as conventional Phased Array ultrasound technology; only, in this case, the targeting is applied to all parts of the region of interest (the “TFM area”), and not just to a fixed depth.

Carlos Álvarez

Published: August 17, 2023

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Ultrasound has been a fundamental tool in the non-destructive inspection of materials for decades, allowing the detection and characterization of defects without compromising the integrity of the inspected objects. As technology advances, more sophisticated and effective techniques emerge, and one of the most prominent is the Ultrasound Technique by Total Focusing Method (advanced-ultrasound-technique-by-the-total-focusing-method -for-the-identification-and-characterization-of-defects) . This technique has revolutionized the way defects are identified and characterized in a wide range of industrial applications, from manufacturing to maintenance.

The Total Focusing Method (TFM) is based on the same targeting and targeting methodology as multi-element ultrasound technology (Phased Array) conventional; only, in this case, the targeting is applied to all parts of the region of interest (the “TFM area”), and not just to a fixed depth. Although TFM could be applied by physically transmitting focused acoustic beams at all positions in the region of interest, the time required to complete such an acquisition cycle is extremely long.

What is Ultrasound by the Total Focusing Method (TFM)?

Technological advancement in the field of non-destructive inspection has revolutionized the way in which defects in materials and components are detected and characterized. One technique that has gained prominence in this area is Ultrasound by the Total Focusing Method (TFM). This is a sophisticated technique within the Ultrasonic test method and incorporated into the advanced Phased Array Ultrasound (PAUT) technique that has significantly improved the ability to detect and characterize defects, as well as the probability of detection (POD) in critical applications in the industrial sector.

Gekko Eddyfi: Fault detector and defect characterization — High resolution Fault Detector, Phase Array and TFM: (Gekko Eddyfi), Eddyfi Source.

TFM employs an innovative approach where each transducer element is activated individually and the signal is collected by all transducer elements, this first part of the process being known as Full Matrix Capture (FMC).

This information is then processed by a powerful software whose algorithms allow the dynamic adjustment of the focal point during data processing (TFM), with which a detailed image of the internal structure of the material is obtained, allowing the detection of defects or discontinuities with an increase of the POD, as well as its detailed characterization, this last aspect being one of the most valuable contributions of the technique.

Effect identification

One of the highlights of TFM Ultrasound is its ability to identify defects with exceptional accuracy, in addition to enhancing the POD. By performing dynamic focal point adjustment, the TFM technique can detect defects such as cracks, inclusions, porosity, and discontinuities in metallic and non-metallic materials. The array of transducers allows for complete sample coverage, resulting in more reliable and comprehensive defect detection compared to conventional ultrasound techniques.

Defect characterization

In addition to identification, accurate defect characterization is essential to understanding their nature and severity. TFM Ultrasound provides the ability to assess the shape, size, orientation, and location of defects. The information collected through this technique allows engineers and technicians to determine if a defect is critical and if it may affect the structural or functional integrity of a component. This is one of the tests that best allows the characterization of defects on a par with radiography. This is especially crucial in industries like aerospace, automotive, and energy, where safety and performance are top of mind.

Applications of Ultrasound by the Total Focusing Method (TFM):

TFM has found a wide variety of applications in various industries due to its ability to deliver high-resolution images and its versatility in different contexts for defect detection and characterization, apart from a good POD. Some of the key applications of the TFM are:

Weld Inspection: In the construction and manufacturing industry, TFM is used to inspect welds on metal structures. It allows the detection of cracks, inclusions and other defects that could affect the integrity of the welded joints.
Composite Materials Evaluation: In the automotive and aerospace industries, TFM is valuable for evaluating composite materials in components such as aircraft wings or car bodies. You can detect internal defects that are not visible from the surface.
Tube and Pipeline Inspection: In the oil and gas industry, TFM is used to inspect pipes and pipes for corrosion, erosion, or other types of deterioration.
Quality Control in Manufacturing: The TFM is applied in the manufacture of parts and components to guarantee their quality and functionality, detecting defects that could affect their performance.
Scientific Research: TFM also has applications in scientific research, such as the study of advanced materials, the characterization of biological structures, and more.

Advantages of Ultrasound by the Total Focusing Method over Conventional Techniques

Ultrasound by the Total Focusing Method (TFM) offers several significant advantages compared to conventional ultrasound inspection techniques:

Enhanced Resolution: TFM uses advanced algorithms to focus the ultrasonic beam at multiple points, generating high-resolution images with detailed visualization of defects. This improved resolution improves POD by allowing the detection and characterization of smaller, more superficial defects that might go undetected with conventional methods.
Improved Sensitivity: With TFM, ultrasonic energy can be more precisely focused on flaws, leading to increased flaw detection sensitivity. This means that even subtle or challenging defects can be detected with greater reliability, reducing the risk of false negatives.
Better Characterization of Defects: TFM allows a better characterization of defects. This not only helps identify the location of defects, but also allows assessment of their shapes, orientations, and sizes, leading to more informed decisions about component integrity.
Reduced Inspection Time: TFM can significantly reduce inspection time compared to conventional techniques. The method’s ability to collect and process large amounts of data efficiently improves productivity and speeds up critical inspections.
Versatility: TFM is applicable to a wide range of materials and structures, including metals, composites, and welds. Its adaptability to various inspection scenarios makes it a valuable tool in many industries, including aerospace, oil and gas, manufacturing, and infrastructure.

Conclusions

The Total Focusing Method (TFM) Ultrasound Technique has proven to be an invaluable tool for defect identification and characterization in a variety of industrial applications. Its ability to provide high-resolution images and its versatility in different contexts make this technique an essential option for advanced non-destructive inspection.

As technology continues to evolve, TFM will play an increasingly important role in ensuring the quality and integrity of materials and components in many industries. The integration of TFM in NDT practices has meant a paradigm shift in the detection and evaluation of defects.

Bibliographic references:

OLYMPUS. Use of the Total Focusing Method to Improve Multi-Element Ultrasound (Phased Array) Image Processing; Consulted on August 13, 2023; https://www.olympus-ims.com/es/applications/using-the-total-focusing-method-to-improve-phased-array-ultrasonic-imaging