Defect detection using a new ultrasonic guided wave modal analysis technique (UMAT)

摘要

A new ultrasonic guided wave modal analysis technique (UMAT) is being studied to bridge the gap between ultrasonic guided wave methods and lower frequency vibration modal analysis methods for Nondestructive Evaluation (NDE) and Structural Health Monitoring (SHM). The new technique provides improved defect detection sensitivity superior to modal analysis alone, and, at the same time, reduces the number of inspection positions required by the guided wave techniques for a complete coverage of the structures being inspected. Instead of focusing on the transient structural response to a guided wave input, the proposed UMAT puts the emphasis on the long time structural response to a specifically defined ultrasonic guided wave input. Since different guided wave modes and frequencies yield good sensitivities to different kinds of defects, the specified guided wave input which is selected to target on a certain defect type provides a special sensitivity to the defect type. By varying the input guided wave modes and frequencies, good sensitivities to all different kinds of defects can be achieved. In UMAT, the defect information is extracted through modal analyses on the long time structural responses to the controlled guided wave inputs. Thanks to the fact that the long time structural responses result from multiple reflections and scatterings of the input guided wave energy, an overall coverage of the structure can be reached from a very limited number of tests. UMAT is also capable of inspecting odd shaped parts with different attachment considerations or boundary conditions and even hidden, coated, or insulated parts as long as a small section is accessible.