Mike Menning’s notes from the 7/7 Conference Call - Tracker Static Testing
Mike Menning Alessandro Brez Eric Swensen
John Ku Nando Menon
Martin Nordby Andrea Tenze
Dick Horn Nicola Saggini
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.
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.
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.