Remote and powerless miniature fatigue monitor and method
First Claim
1. A method for monitoring fatigue in a structure comprising the steps of:
- providing passive fatigue monitors;
locating a region of high stress intensity on a structure;
identifying the principal direction of stresses on said structure;
aligning and bonding said passive fatigue monitors to said structure along the axes of principal stresses;
applying a cycle lead to generate stresses in said structure;
removing said passive fatigue monitor from said structure after the development of striation patterns independent of any crack formation or lack of formation;
determining the number of fatigue-induced striations; and
evaluating the state of fatigue from the number of striations produced during the load application cycle.
2 Assignments
0 Petitions
Accused Products
Abstract
A method and passive monitor for measurement of fatigue is provided. The method includes locating regions of high stress on a structure or material to be monitored, identifying the direction of principal stresses, and then aligning and bonding a specially fabricated passive fatigue monitor to the structure. After the structure has been subjected to a stress cycle, the passive fatigue monitor is removed and the striations formed in the monitor are evaluated. If necessary, contrast enhancement of striations can be performed prior to striation evaluation. Data from evaluations is assessed using rain flow cycle counting and Miners cumulative damage algorithms. The passive fatigue monitor is a small coupon of material fabricated from aluminum or other material known to form well-defined striations. The monitor is specially modified to contain a precrack which provides the location for striation formation.
-
Citations
18 Claims
-
1. A method for monitoring fatigue in a structure comprising the steps of:
-
providing passive fatigue monitors; locating a region of high stress intensity on a structure; identifying the principal direction of stresses on said structure; aligning and bonding said passive fatigue monitors to said structure along the axes of principal stresses; applying a cycle lead to generate stresses in said structure; removing said passive fatigue monitor from said structure after the development of striation patterns independent of any crack formation or lack of formation; determining the number of fatigue-induced striations; and evaluating the state of fatigue from the number of striations produced during the load application cycle. - View Dependent Claims (2)
-
-
3. A method for monitoring fatigue in a structure comprising the steps of:
-
providing passive fatigue monitors; locating a region of high stress intensity on a structure; identifying the direction of principal stresses by applying a coating of photoelastic material to the structure and illuminating said structure to produce fringe patterns; aligning and bonding said passive fatigue monitors to said structure along the axes of principal stresses; applying a cycle load to generate stresses in said structure; removing said passive fatigue monitor from said structure after the development of striation patterns independent of any crack formation or lack of formation; determining the number of fatigue-induced striations; and evaluating the state of fatigue from the number of striations produced during the load application cycle. - View Dependent Claims (4, 5, 6, 7, 8, 9, 10, 11, 12, 13)
-
- 14. A passive miniature fatigue monitor for producing striations independent of any crack formation or lack of formation comprising a coupon having bonding surfaces on a first end and on a second end and further having a reduced thickness center section, the center section having a pre-crack formed therein, the entire coupon being fabricated of a material that develops well-defined striations.
- 17. A passive miniature fatigue monitor for producing striations comprising a coupon having bonding surfaces on a first end and on a second end and further having a reduced thickness center section, the center section producing fatigue induced striations independent of crack formations therein, the entire coupon being fabricated of a polymer-based material.
Specification