For more than a hundred years, materials science engineers have faced the problem of assessing the structural integrity of materials and structures without destroying them. Scientists in disciplines as diverse as aerospace, defense systems, energy, infrastructure and transportation, petrochemical and manufacturing have explored ways to determine the physical properties of the materials that society has come to rely on, and they have struggled with very challenging questions:
- Is there a crack or void, or other defect present?
- Is that defect severe enough to compromise the performance or reliability of that structure?
- How can we confidently detect structural defects during manufacturing, or once a product is in use?
This is the field of Non Destructive Evaluation (NDE) and Non Destructive Testing (NDT), in which ultrasound is playing an increasingly important role. In addition to ultrasound, other methods for using NDT/NDE include magnetic particle, liquid penetrant, radiographic, electromagnetic, and visual testing. Today, NDE/NDT is commonly used in material fabrication, manufacturing and construction to control production quality, economics, standardization during manufacturing as well as to ensure product integrity and reliability and most importantly safety once deployed in the field. Engineers evaluate steel and other metals, concrete, composites and many other materials.
Pierre Belanger, Professor at École de technologie supérieure (ETS), Montreal, Canada has used Verasonics ultrasound systems for materials sciences. He recently described for Plane Wave how he uses ultrasound for testing large billets of expensive metals: “For over 4 years, I have used ultrasound as the primary method of non-destructive evaluation in our lab at ETS. Ultrasound is proven as a valuable tool for ensuring quality control and standardization in production processes, while being flexible and cost effective. If a defect is found in NDE, machining can be adjusted or avoided, saving time and money, while, most importantly, ensuring public safety.”
When using ultrasound for NDT/NDE, high frequency sound waves are applied to the material being evaluated. If the sound waves encounter a defect or a material with different acoustic impedance, an abnormality will become visible to the researcher in the wave forms detected by the system. Materials science uses compression waves, shear waves, guided waves and other techniques to locate and characterize materials during industrial inspections.
Professor Belanger added, “Today in industry, ultrasound is routinely used to evaluate materials because of its flexibility in frequency and signal, and because it is possible to achieve a high level of accuracy in the analysis required to perform comprehensive non-destructive testing and evaluation.”