Nondestructive and Noncontact Evaluation of Corrosion and Fatigue by Laser Speckle Sensor (LSS) and Laser Moire
Abstract
Five NDE techniques have been exploited for the detection of damage caused by corrosion and fatigue. They are (1) ESPI (Electronic Speckle Pattern Interferometry), (2) Digital Speckle Correlation, (3) TADS (Time Average Digital Specklegraphy), (4) Modified Projection Grating Technique and (5) Fractal Damage Sensor. Except the first one whose basic principle is known, the rest are all new techniques. While different techniques have different advantages and disadvantages, the most versatile is probably TADS and the Modified Projection Grating technique, whereby large areas (such as 5 M x 5 M or larger) can be evaluated simultaneously. We also investigated the corrosion and fatigue processes and their synergism. We find that corrosion in general reduces the fatigue life of a metallic alloy. However, if a modest amount of initial fatigue is followed by a modest amount of corrosion, the total fatigue life is actually enhanced. This is attributed to the blunting of micro crack tips by corrosion.
Document Details
- Document Type
- Technical Report
- Publication Date
- Feb 01, 1998
- Accession Number
- ADA340357
Entities
People
- Fu-pen Chiang
Organizations
- Stony Brook University