Mike Menning’s notes from
the 7/7 Conference Call - Tracker Static Testing
Attendees:
Mike Menning Alessandro Brez Eric Swensen
John Ku Nando Menon
Martin Nordby Andrea Tenze
Dick Horn Nicola Saggini
Mark Molini
Dave Rich
Dick Horn
Jim Martin
Travel Plans
John Ku, Mark Molini, and
Erik Swensen have made ( or are making ) plans to travel to Pisa for a working
session with INFN to assist in the transition of responsibility for the static
load tests on the lower tray assembly. The planned travel will place John,
Mark, and Erik at INFN from Mon April 19 to Fri April 23.
Practice Test Objectives
The purpose of the practice
tests is to transition the responsibility for the static load test fixture for
the lower tray from Hytec to INFN. The visit from John, Mark, and Erik is to
assemble the test fixture in Italy and bring it to a state of operational
readiness. Operational readiness will be achieved by installing a bottom tray
assembly with the old interface design and applying some level of loads to the
lower tray assembly while recording the load and deflection data. The loads
need not be the full test loads but the desire is to validate that the test
fixture and instrumentation have been assembled correctly and are performing in
a reasonable and expected fashion. It is desirable to function the test fixture
in all four of it's load configurations. Compatibility of the instrumentation
and data collection equipment supplied by SLAC to augment the equipment
supplied by Hytec should demonstrated. A draft test procedure for an Acceptance
test or a Proto-flight test should be developed and utilized in the practice
tests. Any additional equipment that is needed should be identified and a
delivery plan developed.
Acceptance Test Objectives
The purpose of the
acceptance tests is to demonstrate for each flight lower tray assembly that the
workmanship for the bonded joints between the titanium parts and the closures
is of such quality that proceeding to the next level of assembly with the lower
tray is low risk. Mike Menning suggested that this might be accomplished with a
reduced number of load cases from the set of load cases tested at Hytec ( X
axis, y axis, diagonal along the xy axis, and a n axial z load). From
discussions with Erik Swensen, Mike suggested that an xx test and a yy test
would be a choice which would provide confidence in the structural bonds and
would allow rapid reconfiguration from one load case to another. The intent is
that a real time judgment on test success can be determined by applying a load
( via a spring deflection) and monitoring the load for any reduction in value
over a period of time. For instance a load reduction of less than 10% over 30 seconds
might be considered a successful test. Sandro
pointed out that if frequent switches were to be required during acceptance
testing from the axial to the lateral load configuration that additional
hardware would be required in the form of load cell, load application spring,
etc.
Proto-Qual Test Objectives
Mike Menning presented his
opinion that the purpose of the Proto-Qual test is to demonstrate that flight
hardware can successfully sustain loads which are in excess of the expected
flight loads. Once this is demonstrated on one article of flight hardware, acceptance
tests can be performed on the remaining flight hardware at levels equal to the
expected flight loads with the knowledge that the article still has a finite
structural margin remaining. A great deal of discussion followed on this issue.
Much of the concern is that INFN did not realize early on that the transfer of
static test responsibility from Hytec to INFN would entail a design
qualification test. Accordingly there is little or no schedule available for
performing this test. As a result of this discussion, John Ku was given an
action to evaluate the qual load levels versus the proto-qual load levels
versus the acceptance load levels versus the minimum workmanship load levels
for the bottom tray assemblies and to prepare a recommendation for the static
test plan which best qualifies the flight hardware while minimizing schedule
penalty. John's recommendation will be the subject of a follow-up conference
call on Wed April 14 at 8:00 AM Pacific Time. Mike Menning to arrange for a
call-in number.
Heat Straps
It was generally agreed that
heat straps do not carry any significant structural load across the interface
and can be omitted in a static load test. A spacer is needed of the thickness
of the heat straps between the sidewall and close-outs to avoid damage to the
side walls during assembly.
Cones
The eccentric cones are
needed in both all static and vibration tests to create an interface with a
flight type stiffness which properly distributes loads within the lower tray
assembly. No adjustment of the eccentric cones to achieve a specific alignment
condition is needed (except in those
cases where alignment repeatability before and after vibration test is to be
demonstrated) . Shims are needed
between the flexures and grid simulators in all cases to prevent damage to the
close-outs when the nuts are tightened to preload the flexures against the grid
simulator.
Granite table and Adapter
plate
The granite table will
arrive in Pisa the week of the 19-24 th. Although it is not expected to be
installed and available for attachment of the test fixture during the visit by
John, Mark, and Erik, lower level load tests on the steel adapter plate are
expected to be possible.
Additional Equipment for
SLAC to Bring
A discussion of some of the
instrumentation and miscellaneous equipment needs followed. Mark Molini plans
to make a "gift basket" of all of the items which may be needed to
perform a successful practice test. Mark and John will stay in close touch with
Andrea via E-mail in order to keep the list current.