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Test Apparatus for Outdoor Cyclic Fatigue Testing of Sealants and Other Materials.

IP.com Disclosure Number: IPCOM000126302D
Original Publication Date: 2005-Jul-12
Included in the Prior Art Database: 2005-Jul-12
Document File: 4 page(s) / 114K

Publishing Venue

National Institute of Standards and Technology

Related People

Christopher C. White: INVENTOR [+6]

Abstract

A new cyclic fatigue test apparatus (CFTA) was developed for cyclic fatigue testing materials outdoors. The cycles originate from weather-induced movement of actual materials and thus give a complex cyclic movement to the CFT A. Materials placed in the CFT A are fatigue cycled using this complex movement to achieve weather-induced fatigue. The apparatus can test up to 20 specimens and the changes in each specimen during the test are determined from its load and deflection. The apparatus can also run a stress-relaxation profile on the specimens at any time during the exposure.

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A new cyclic fatigue test apparatus (CFTA) was developed for cyclic fatigue testing materials outdoors. The cycles originate from weather-induced movement of actual materials and thus give a complex cyclic movement to the CFT A. Materials placed in the CFT A are fatigue cycled using this complex movement to achieve weather-induced fatigue. The apparatus can test up to 20 specimens and the changes in each specimen during the test are determined from its load and deflection. The apparatus can also run a stress- relaxation profile on the specimens at any time during the exposure.

11. Details of the invention, including the following information:

a. General field of application, and principal utility of the invention.

     Any type of material that may undergo thermal or moisture induced cyclic fatigue can be tested using this apparatus. At present it is being used to test viscoelastic materials.
b. Theory of operation.

     The apparatus is designed to cyclic fatigue materials using complex cycles obtained during outdoor weathering. The cyclic motion is obtained from the movement of a sensor material caused by thermal or moisture induced changes. The signal that originates form the sensor material is fed through a computer to control linear actuators on the device to duplicate the motion of the sensor material. The actual movement of the specimens is measured and feed back to the computer to ensure that the movement is correct. The computer can be set to limit maximum strain and in addition limit switches are in place to ensure that an errant signal does not cause excessive movement.
c. If mechanical or electrical invention, give detailed sketches or drawings. All component parts should be labeled, and the description keyed thereto.

  Exhibits A-C show the test apparatus, Exhibit D shows the sensor (in this case a black aluminum bar), and exhibit E shows a flow chart for the computer control software.

Exhibit D shows the sensor. It is approximately 1 meter long with one end fixed to a wood support. The other end moves through the thermally induced expansion and contraction of the aluminum and the movement is measured by a linear variable differential transformers (L VDT). If moisture induced movement was needed, the sensor would be a piece of flat-grained wood mounted on an aluminum support. The sensor (Exhibit D) changes dimension as the weather changes and electronic signal from the L VTD is fed to a computer that can modify the signal to increase or decrease the signal intensity (thus increasing or decreasing the movement on the specimen). The computer can also set limits on the amount of movement to keep the strain on the specimen within set limits. Exhibit A shows a front view of the apparatus. The test apparatus has a stationary aluminum I-beam (upper beam) and a moveable aluminum I-beam (lower beam). The signal from the computer is fed to a controller that directs the linear actuator to move. The linear actuator causes a movement of the l...