Optical Strain Gage Measurement of Accumulated Damage Around Geometrical Discontinuities Such as in Pipes and Pressure Vessels

The optical strain gage technologies are used to measure strain and evaluate accumulated damage around a geometrical discontinuity such as holes, notches or fillets that exist in pipes and pressure vessels. Results are presented for coupons undergoing stress. The results are consistent with theory. The DMI technologies optically observe record and measure the deformation of a target affixed to the surface of the part undergoing stress in a region of expected maximum strain or a region physically and mathematically linked to the region of maximum strain. Data is acquired from its proprietary target (strain gage) or 2D Data Matrix mark used as a target/strain gage. The deformation of the mark/strain gage as the object undergoes deformation is mathematically described by total strain equal to the elastic and plastic strain components. This equation can be rewritten to express strain life in terms of plastic strain. The measured plastic component of strain is directly related to the damage.Copyright © 2006 by ASME