Bookmarking the NDE Capability and Challenges Near the Dawn of the New Millennium

摘要

As the 2nd Millennium is coming to an end, it is interesting to look back and see how far the field of NDE has been advanced so far and what are still the challenges. Like many other fields, improvements were made in every aspect of the NDE science and engineering where computers and internet contributed greatly to the rapid advancement. The various NDE methods were benefited with better inspection techniques. Also, efforts are increasingly being made to integrate several methods to form multi-mode systems that take advantage of the complementary capabilities to increase the functionality as well as the overlapping capabilities to improve the reliability. Some technologies affected most or all the NDE methods and those include the use of computer graphics and interactive simulation to investigate the response of the specific methods. The effect of flaws on the wave response is analyzed using theoretical models and analytical tools, including finite element techniques. Also, inversion techniques are developed to extract flaw characteristics and material properties using nondestructive measurements. Sensors can be divided into the following groups 1. Remote sensors - Eddy current, magnetic, visual, dry-couple ultrasonics, etc. 2. Attached sensors - Cracking fuse, resistance gauging, strain gage, acoustic emission, ultrasonic, eddy current, fiber optics 3. Sensitive coating - Bruising paint indicator, brittle coating, liquid crystals 4. Imbedded sensors - Fiber optics, dielectric, eddy current, magnetic, ultrasonics The most practical sensors currently used are the ones that either operated remotely or attached to the test structures. The manufacturers and user are still not receptive to using sensors that are imbedded or permanently attached or coated. This is due to the addition in weight and the potential effect on the structural integrity. The use of stick-on wireless type sensors are expected to emerge in the coming years allowing to monitor structural integrity throughout structures life cycles without disassembly, redesign or complex wiring. The use of the crawler technology, which was enabled by JPL, is offering great potential to rapid field inspection, where plug-and-ply boards would define the crawler functionality. Employing off-the-shelf components and standard personal computers bus structure (e.g., ISA, PCI etc.) can lead to a significant reduction in system cost. Currently, NDE hardware manufacturers have to develop a complete instrument each time a new product is introduced. It is envisioned that concentration on the development of components with focused NDE functionality (e.g., ultrasonics) will have great payoff. It would lead to substantially greater affordability of future instruments and to a faster transition of NDE technology to commercial use. Since the 96 ASNT Fall Conference, the author started holding Sessions on the topic of Robotics and Miniaturized NDT Instruments. The intent of these Sessions is to attract industry and academia attention to the topic of developing generic mother-crawler and related plug-in modules. Recent government interest in addressing the issue of NDE of corrosion turned the spotlight onto MACS (JPL, Pasadena, CA) as a potential baseline for robotic multi-sensor platform for rapid scanning of aircraft structures. In future generations of this technology, micro-electronic mechanical systems (MEMS) is expected to lead to extremely small NDE instruments and scanners. Insect-size micro-scanners may potentially crawl into an aircraft engine and other hidden areas and perform inspection or other maintenance tasks. Advancement in miniature electronics, actuators, robotics, wireless communication as well as sensors are expected to make great impact on the field of NDE in the coming years. The search for smarter methods that can rapidly and inexpensively detect very small flaws in complex materials and structures at very high probability and repeatability will continue to be a challeng