Stress indicating mechanical fastening device

Claim 1

A TORQUE INDICATING FASTENING DEVICE COMPRISING A BODY HAVING AN INTERNALLY THREADED OPENING FOR SECUREMENT TO OTHER STRUCTURE, SAID BODY HAVING AN UPPER END SURFACE AND A LOWER END SURFACE, SAID BODY HAVING AN ANNULAR RECESS CONCENTRIC WITH THE INTERNALLY THREADED OPENING, SAID RECESS EXTENDING FROM THE UPPER END SURFACE TOWARDS THE LOWER END SURFACE AND DEFINING AN OUTER WALL PORTION AND AN INNER WALL PORTION, THE BODY MATERIAL BETWEEN THE BOTTOM OF THE RECESS AND THE LOWER END SURFACE HAVING A PREDETERMINED CROSS-SECTIONAL AREA TO RESULT IN A PREDETERMINED STRESS YIELD POINT, AND A STRESSSENSITIVE MATERIAL IN THE RECESS IN INTIMATE CONTACT WITH THE SURFACES DEFINING THE RECESS, SAID STRESS-SENSITIVE MATERIAL BEING REACTIVE TO RELATIVE MOVEMENT OF THE AFOREMENTIONED OUTER WALL PORTION AND INNER WALL PORTION OF THE BODY TO INDICATE THE OCCURRENCE OF SUCH RELATIVE MOVEMENT, RELATIVE MOVEMENT OCURRING WHEN THE TORQUE APPLIED TO THE BODY REACHES THE STRESS YIELD POINT OF THE BODY MATERIAL BETWEEN THE BOTTOM OF THE RECESS AND SAID LOWER END SURFACE.