Patent ID: 6874370

Claim:
Apparatus for calculating strain and fatigue damage in materials based on observing the deformation of a geometric shape associated with a body undergoing cyclic loading, the geometric shape being affixed to or identified on or formed in the surface of the body and defining a target, the target having a perimeter, being associated with the body in such a way that the deformation of the target and the deformation under load of the body with which it is associated bear a one-to-one relationship, and emitting or reflecting a detectable physical quantity, the apparatus comprising: sensor means for capturing the total image of a target and for outputting data representing the total image of the target, means for isolating the perimeter of the target using edging algorithms and the data acquired from the sensor means, means for setting a number of nodes to be tracked and establishing the nodes on the perimeter of the target in accordance with finite element theory, means for tracking, relative to a coordinate system and as a function of time, the movement of perimeter nodes of the target as the body undergoes deformation during or after the termination of cyclic loading, and recording the displacement as a function of time, means for manipulating the data on movement of the nodes using (i) fundamental concepts of nonlinear stress analysis, (ii) finite element analysis, and (iii) material properties and characteristics and an equation based on strain-controlled test methods, and means for displaying the results of the computer manipulated data.