# US 8,739,611 B2 · Strain indicator for a gas turbine engine component > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 8,739,611 B2 - Document ID: US8739611B2 - Status: Granted - Kind: B2 - Application number: 13/208,938 - Filed: 2011-08-12 - Published: 2012-03-15 - Granted: 2014-06-03 - Earliest claimed: 2010-09-15 - Assignees: ROLLS-ROYCE plc - Applicants: Ian C. D. Care; Ewan F. Thompson - Inventors: Ian C. D. Care; Ewan F. Thompson - Web page: https://patentgrep.com/patent/US8739611B2 ## CPC - F01D 21/003: {Arrangements for testing or measuring (for measuring vibrations G01H)} - G01M 5/0016: {of aircraft wings or blades} - G01M 5/0033: {by determining damage, crack or wear} - F05D 2260/80: Diagnostics - Y02T 50/60: Efficient propulsion technologies, e.g. for aircraft - F01D: NON-POSITIVE DISPLACEMENT MACHINES OR ENGINES, e.g. STEAM TURBINES (machines or engines for liquids F03; non-positive displacement pumps F04D) - G01M: TESTING STATIC OR DYNAMIC BALANCE OF MACHINES OR STRUCTURES; TESTING OF STRUCTURES OR APPARATUS, NOT OTHERWISE PROVIDED FOR - F05D: INDEXING SCHEME FOR ASPECTS RELATING TO NON-POSITIVE-DISPLACEMENT MACHINES OR ENGINES, GAS-TURBINES OR JET-PROPULSION PLANTS - Y02T: CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO TRANSPORTATION ## Abstract A component for use in a gas turbine engine comprises an indicator operable to provide a visual indication when strain over a threshold value has been experienced by the component by transitioning from a rest state to an indication state on occurrence of strain above the threshold value. Also disclosed is a method of detecting foreign object damage in a component of a gas turbine engine, comprising: identifying at least one of a component or a region of a component that is subject to increased strain during a foreign object impact; and mounting an indicator on the identified component or region of a component, the indicator providing a visual indication when increased strain has been experienced. ## Claims ### Claim 1 A component for use in a gas turbine engine, the component comprising an indicator operable to provide a visual indication when strain over a threshold value has been experienced by the component by transitioning from a rest state to an indication state on occurrence of strain above the threshold value, wherein: the indicator includes an indication element and a fixation element that mounts the indication element to a surface of the component, and the transition of the indicator from the rest state to the indication state comprises failure of at least one of the indication element and the fixation element. ### Claim 2 (depends on 1) A component as claimed in claim 1, wherein the visual indication comprises a change in colour of the indicator between the rest and indication states. ### Claim 3 (depends on 1) A component as claimed in claim 1, wherein the indicator is operable to transition through a plurality of indication states on occurrence of strain over successive threshold values. ### Claim 4 (depends on 1) A component as claimed in claim 1, wherein the indication element comprises a patch of frangible material. ### Claim 5 (depends on 4) A component as claimed in claim 4, wherein the frangible material comprises a colour that is indicative of the indication state. ### Claim 6 (depends on 4) A component as claimed in claim 4, wherein the patch of frangible material houses at least one frangible container which holds a dye of a colour that is indicative of the indication state. ### Claim 7 (depends on 4) A component as claimed in claim 4, wherein an outer surface of the indication element-comprises a coating of a colour that is indicative of the rest state. ### Claim 8 (depends on 1) A component as claimed in claim 1, wherein the fixation element comprises a frangible adhesive. ### Claim 9 (depends on 8) A component as claimed in claim 8, wherein the frangible adhesive comprises a colour that is indicative of the indication state. ### Claim 10 (depends on 1) A component as claimed in claim 1, wherein the fixation element comprises a frangible mechanical fastening. ### Claim 11 (depends on 10) A component as claimed in claim 10, wherein the indication element comprises a colour that is indicative of the rest state. ### Claim 12 (depends on 11) A component as claimed in claim 11, wherein a region of the component that is covered by the indication element comprises a colour that is indicative of the indication state. ### Claim 13 (depends on 1) A component as claimed in claim 1, wherein the fixation element comprises a housing formed within the blade. ### Claim 14 (depends on 13) A component as claimed in claim 13, wherein the housing is operable to release the indication element on experiencing strain above the threshold value. ### Claim 15 (depends on 1) A component as claimed in claim 1, wherein the indicator is located at a region of the component that is subject to strain over the threshold value during an impact event. ### Claim 16 (depends on 1) A component as claimed in claim 1, wherein the component is made of composite material. ### Claim 17 (depends on 1) A component as claimed in claim 1, wherein the component is a blade or stationary vane or nose cone or intake nacelle. ### Claim 18 (depends on 1) A gas turbine engine including a component as claimed in claim 1. ### Claim 19 A method of detecting foreign object damage in a component of a gas turbine engine, comprising: identifying at least one of a component or a region of a component that is subject to increased strain during a foreign object impact; and mounting an indicator on the identified component or region of a component, the indicator providing a visual indication when increased strain has been experienced, wherein: the indicator includes an indication element and a fixation element that mounts the indication element to a surface of the component, and the transition of the indicator from the rest state to the indication state comprises failure of at least one of the indication element and the fixation element.