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