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Hydraulic Actuator Project. Development of Materials Joint Test Protocol has been work-in-progress for more than one year; large number of contributors and intermittent amount of time devoted to bringing it together
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Hydraulic Actuator Project • Development of Materials Joint Test Protocol has been work-in-progress for more than one year; large number of contributors and intermittent amount of time devoted to bringing it together • In Summer 2001, decided to concentrate on developing and executing a rod/seal functional test to assess performance of HVOF coatings against selected seal materials • Initially expected contractor to perform work, but in Fall 2001 became aware of test apparatus at NAVAIR Pax River used for assessing new seal materials; assessment determined that this would be ideal for HCAT planned work
NAVAIR Pax River Seal Testing Information provided by Jeff Moorman at Pax River • Problem was that large percentage of components on Navy aircraft hydraulic systems removed due to external leakage • Most components are packed with Nitrile rubber seals which is damaged above 200o F; amount of seal damage is cumulative with exposure time and increases rapidly with elevated temperatures • Pax River used in-house test apparatus to identify and qualify a seal material that would better withstand operating conditions by eliminating or delaying external leakage • Seal failure modes include hardening and cracking, abrasion, and extrusion
Pax River Test Apparatus Environmental Chamber: Temperatures from -65 to +300 deg.F; hydraulic power supply is outside chamber Drive rod goes through chamber wall; hydraulic pressures inside seal fixture are varied between 1000 and 3000 psi
Pax River Test Apparatus Test apparatus mounted in environmental chamber; consists of four rods with pair of seal blocks per rod Primary seals in blue, secondary seals in magenta; two seal configurations per block and 16 seal configurations under test
Pax River Test Spectrum to be Usedon Evaluation of HVOF Coatings Cycle Details - Each hour consisted of: 20 minutes sine wave 3.5 in pk to pk with period of 1.5 seconds. Max velocity of 8 in/sec. 20 minutes sine wave 2.0 in pk to pk with period of 4 seconds superimposed with a dither 3/8 inch pk to pk at 4 Hz. 20 minutes sine wave dither in place 3/8 inch pk to pk at 4 Hz. Testing was performed in 16 hour days. First day at 300 degrees F with 25 degree drop on each subsequent day. Stand was cold soaked to 0 degrees F between testing blocks. Block 6 at 175 degrees F was followed by -40 degree F soak and 4 hours at 300 degrees F to complete 100 hours. Internal pressures were actuator drive pressures which varied from 500 to 2500 psi throughout testing.
Current Status • Test rods have been fabricated at Metcut and are being shipped to NRL • Working to finalize test document and get cost proposal from Pax River