Early warning material failure indicator

Claim 2

Apparatus for providing an early warning indication of impending failure of a structural element subjected to a corrosive environment, comprising a corrodible member, means for exposing said corrodible member to the corrosive environment, means for stressing said corrodible member including means for applying to said corrodible member a tensile stress such as to cause movement of the stressing means upon failure of the corrodible member, the amount of stress applied to said corrodible member being such as to cause failure by corrosion of the corrodible member before failure of the structural element, a magnetic member coupled to the corrodible member and adapted to move upon failure of the corrodible member, and means in response to failure of the corrodible member to provide an indication of said failure, said failure responsive means including electromagnetic means magnetically coupled to the magnetic member for detecting movement thereof causing a change in the magnetic coupling.

Claim 3

Apparatus as claimed in claim 1 and further comprising a housing, means for mounting the corrodible member within the housing, means for mounting the housing to the structure, and means for attaching the electromagnetic means to the outside of the housing.

Claim 4

Apparatus as claimed in claim 2 wherein the electromagnetic means is permanently mounted on the housing, and the electromagnetic means generates an electrical signal upon movement of the magnetic member.

Claim 5

In combination, a structural element under load, a corrosive environment to which the structural element becomes exposed and which will ultimately cause failure thereof, and means providing an early warning indication of impending failure of the structural element due to attack by the corrosive environment, said early warning means comprising a corrodible member, means for exposing the corrodible member to the same corrosive environment to which the structural element becomes exposed, means for stressing said corrodible member, said corrodible member when stressed being more prone to failure by stress-corrosion cracking when exposed to said corrosive environment than said structural element, a magnetic member coupled to the corrodible member, means for moving the corrodible member upon failure thereof, and means not exposed to the corrosive environment and magnetically coupled to the magnetic member for detecting movement thereof and generating an electrical signal in response to said movement to provide an early warning of future failure of the structural element.

Claim 6

In combination, a structural element under load, a corrosive environment to which the structural element becomes exposed and which will ultimately cause failure thereof, and means providing an early warning indication of impending failure of the structural element due to attack by the corrosive environment, said early warning means comprising a corrodible member, means for exposing the corrodible member to the same corrosive environment to which the structural element becomes exposed, means for stressing said corrodible member, said corrodible member when stressed being more prone to failure by stress-corrosion cracking when exposed to said corrosive environment than said structural element, a magnetic member coupled to the corrodible member, means for moving the corrodible member upon failure thereof, and means not exposed to the corrosive environment and magnetically coupled to the magnetic member for detecting movement thereof and generating an electrical signal in response to said movement to provide an early warning of future failure of the structural element.

Claim 7

The combination claimed in claim 4 wherein said corrodible member has the same chemical composition as that of the structural element.

Claim 8

The combination claimed in claim 4 wherein the corrodible member is more prone to failure by applying to it a greater unit stress than that applied to the structural element by its loading.

Claim 9

The combination claimed in claim 6 wherein the greater unit stress is achieved by providing the corrodible member with a region of reduced cross-section.

Claim 10

The combination of claim 4 wherein the corrodible member is more prone to failure as a result of having a reduced density compared with that of the structural element.

Claim 11

The combination of claim 4 wherein the corrodible member comprises a notched rod, and means for biasing the rod into a tensile stressed condition.

Claim 12

The combination of claim 4 wherein the corrodible member comprises a sintered disc having apertures therein, and means for biasing the disc into a tensile stressed condition.

Claim 13

In combination, a structural element under load, a corrosive environment to which the structural element becomes exposed and which will untimately cause failure thereof, and means providing at a remote location an early warning indication of impending failure of the structural element due to attack by the corrosive environment, said early warning means comprising a corrodible member, means for exposing the corrodible member to the same corrosive environment to which the structural element becomes exposed, means for stressing said corrodible member, said corrodible member when stressed being more prone to failure when exposed to said corrosive environment than said structural element, and means mechanically spaced from but electrically coupled to said corrodible member and responsive to failure thereof to generate outside the corrosive environment an electrical signal which can be transmitted to the remote location to provide thereat an early warning of future failure of the structural element.

Claim 14

In combination, a structural element under load, a corrosive environment to which the structural element becomes exposed and which will untimately cause failure thereof, and means providing at a remote location an early warning indication of impending failure of the structural element due to attack by the corrosive environment, said early warning means comprising a corrodible member, means for exposing the corrodible member to the same corrosive environment to which the structural element becomes exposed, means for stressing said corrodible member, said corrodible member when stressed being more prone to failure when exposed to said corrosive environment than said structural element, and means mechanically spaced from but electrically coupled to said corrodible member and responsive to failure thereof to generate outside the corrosive environment an electrical signal which can be transmitted to the remote location to provide thereat an early warning of future failure of the structural element.

Claim 15

The combination claimed in claim 11 wherein said failure responsive means includes a differential transformer capable of detecting small movements of the corrodible member.

Claim 16

The combination of claim 11 and further comprising a magnetic member coupled to the corrodible member, means for moving the magnetic member upon failure of the corrodible member, and means including a differential transformer not exposed to the corrosive environment and magnetically coupled to the magnetic member for detecting movement thereof and generating an electrical signal in response to said movement.