July 9 ART Meeting Minutes


2. Action item status:


ART-1:  Provide ART with test result data from Vibration Tests (LAT-TD-00788) - Horn Closed

ART-2:  Provide ART results of insert pull out tests - Johnson - Open

      Current Status: Tom Borden to work with Hytec to provide data

ART-3:  Provide ART the properties for the carbon-carbon material - Johnson - Closed

ART-4:  Provide a recommendation for design practice and analysis cases for redundant load path considerations - Rodini - Closed

ART-5: Distribute a proposed analysis plan to the team and review it at the next ART - Borden - ECD 11 July

      Current status: Action broadened to include failure analysis, failed material review & corrective action

ART-6: Coordinate a review of environment requirements - Graf/Rodini - ECD 15 July

ART-7: Consider & recommend plan for additional flexure testing - Borden/Millican - ECD 11 July

ART-8: Bernie Graf to investigate material failure analysis capability at GSFC - ECD 15 July


3. Discussion


- Tom Borden discussed his initial proposal for failure analysis.  The goal is to provide an analysis that accounts for the factors that may have contributed to the failure, including insert tolerances, fitting factors, stress concentration assumptions, unexpected load conditions at the corners (bending contribution).  The analysis is seeking to develop a better understanding of design loads and strength requirements and resulting margins given the current material selection leading to a refinement of our ability to predict this failure condition for the current design.  The analysis should also lead to concurrence with the ART on assumptions that should be used for the various factors during corrective action.  Tom is completing coordination with the tracker team and Hytec to refine the analysis plan & schedule.


-  The ART is in process or completed review of the following possible contributing factors to the failure


-- Over test conditions: The tracker team has indicated that they verified AMES test environment input as correct.

-- Design environments over specified: Bernie Graf/Ben Rodini ART-6 in work

-- Lower than expected material strength: Recommend material property test/inspection of failed part

-- Incorrect design load requirements: ART-2 in work

-- Review of processes: Reviewed insert tolerances, recommend a 1.25 factor to account for non-uniform load sharing

-- Review of design assumptions: Stress concentration factor of 2.1 may be low for application, Should add a fitting factor of 1.15(TBR)

-- Review likelihood that first test failure (screw backout) overstressed corner attach point: Supporting analysis required, include in ART-2

-- Verify adequacy of current FEM - Hytec correlation to initial test data reported


4. Closure plan


- The ART has recommended that the tracker team proceed in a parallel path investigation focused in three areas:


-- Complete failure analysis per ART-2

-- Conduct further inspection and test of failed parts to determine as built material properties and processing defects

-- Continue with refinement of proposed corrective actions to ensure a robust design


Please provide any corrections/clarifications of these minutes to Dick Horn prior to the next meeting 11 July