| Budget Amount *help |
¥6,000,000 (Direct Cost: ¥6,000,000)
Fiscal Year 1985: ¥1,500,000 (Direct Cost: ¥1,500,000)
Fiscal Year 1984: ¥4,500,000 (Direct Cost: ¥4,500,000)
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| Research Abstract |
By applying the concept of the X-ray CT (Computer Tomography) method, an electric potential CT method was proposed, in which data of electric potential distribution on a conductive material were computer-processed by inverse analyses to determine locations, shapes and sizes of two-and threedimensional cracks in the material. Two inverse analysis schemes were formulated in terms of the boundary element equations. In one schene called the inverse boundary element method (IBIEM), the boundary element equations were solved for quantities on unprescribed boundaries. Cracks were identified as flux-free boundaries. In the other scheme called the least residual method (LRM), the boundary element solution of electric potential for an assumed crack profile was compared with the observed values on free boundaries. The crack profile which minimized the square sum of residuals, was employed as the most probable one. Improvements and extensions of the two schemes were discussed.
To examine the feasibility of the proposed method, numerical simulations were conducted for determining the locations, shapes and sizes of several types of twoand three-dimensional cracks: an edge crack, and internal cracks in two-dimensional bodies, and a rectangular surface crack, a rectangular internal crack and an L-shaped surface crack in three-dimensional bodies. The results demonstrated the versatility of the electric potential CT method.
Applicability of the proposed method to engineering problems was experimentally studied using steel plates. The locations and sizes of short and long single-edge and internal cracks were determined with good accuracies from the data on electric potential distribution. The electric potential method was also found useful for the quantitative measurement of crack lengths at elevated temperatures.
The numerical and experimental results lead us to believe that the proposed electric potential CT method has potential to be used as a practical inspection technique.
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