Metal Testing

About

Background: This invention can identify damage prior to catastrophic failure, or can determine that a part scheduled for replacement can remain in service. The guiding principle of nondestructive testing (NDT) is the evaluation of a component to determine its suitability for service without compromising the component itself. When properly implemented, NDT can identify a damaged part prior to catastrophic failure, or can determine that a part scheduled for replacement can remain in service. In both cases, the savings in terms of time, money and potentially lives are significant, which is why the NDT industry generates billions of dollars a year in revenue. Unfortunately, the earliest signs of structural change in a material due to mechanical, thermal or chemical stress often cannot be detected by current NDT methods. Second harmonic generation (SHG) has great promise as an NDT platform. This nonlinear optical technique could be implemented for a fraction of the cost of many NDT methods and potentially detect the earliest possible signs of material weakness. SHG has great potential to be faster, cheaper, easier to interpret, and more sensitive than current NDT technologies. An NDT system based on SHG could be built for around $30,000, making it much cheaper than existing NDT instrumentation that can cost upwards of $250,000. In addition, many NDT methods require that equipment be taken off-line and transported to a testing facility, resulting in additional costs and downtime. SHG testing systems could also be incorporated into assembly lines, allowing for testing of each part as it is produced, rather than random sampling from a batch as is commonly done. The readout from such an SHG system would be a simple numerical value, allowing a trained technician to readily determine the serviceability of a component by comparing to a reference sample. SHG also has the potential to be field-deployable, allowing for on-site testing. In addition to the enormous revenue potential this represents, SHG may also allow for the incorporation of real-time testing on assembly lines or other production facilities. The savings in terms of minimizing downtime, reducing the number of defective components, and reducing unnecessarymaintenance would be substantial. An SHG system could also be automated to provide a determination of the suitability of a given sample for its intended use; many current NDT methods provide subjective results and require a technician to make a determination as to suitability, which increases the possibility of human error in interpreting the results. Three primary advantages of the invention include: sensitivity to effects of deformation before cracks have formed; remote, non-invasive detection; and low likelihood of false positives. Current disadvantages include: sensitivity still needs to be determine for a variety of systems; there is a significant possibility of false negatives, and more needs to be done to reduce those; as of now, this is a laboratory-based technique, although miniaturization and portability should be possible.