FIELDS Fabrication Review Board FRB Search Coil Magnetometer

FIELDS Fabrication Review Board FRB Search. Coil Magnetometer SENSOR S/N 4 Ferrite cores cracks P. LEROY MMS SCM FRB, 20 APR 2012 1

Introduction • History: – S/N QM SENSOR ferrite cores broke during the first vibration campaign, cracks located at the end of the cores – S/N EM 4 SENSOR fully qualified at protoflight levels (change in vibration levels and in the test protocol, notching applied) – S/N FM 1 SENSOR fully qualified at protoflight, delivered at UNH – S/N FM 2 SENSOR fully qualified at protoflight, calibrated, to be delivered soon at UNH – S/N FM 4 SENSOR chosen for the SCM FM 3 delivery jointly with the S/N FM 4 PREAMP • Cracks detected at the center of the ferrite cores during post-vibration thermal cycle validation at LPP (see next slide for workflow) – ambient pressure – Cycle [°C]: 22 – 30 – 40 – 50 – 60 – 50 – 40 – 30 – 22 – Plateau of 5 minutes at each step • • Investigations have shown that the torque value used for S/N FM 4 (1. 4 N. m) was different from the requested one (1. 2 N. m) due to a bad calibration of the screw-driver. This is the only difference we saw between the previous models NCR documented: MMS-SCM-NC-TRI 139_FM 4_SENSOR_cracks_after_vibration. doc MMS SCM FRB, 20 APR 2012 2

SCM Sensor Manufacturing Workflow SENSOR S/N FM 4 cracks detected at this step MMS SCM FRB, 20 APR 2012 3

3 cycles have been performed at LPP on the S/N FM 4 sensor => 2 cores broke 1 2 • • 3 MMS SCM FRB, 20 APR 2012 • X cracked during cycle 1 Crack not seen during the X-ray inspection performed between after cycle 1 Cycle 2 launched for validation => Z cracked Tubes removed from the holder => crack detected at X-ray inspectio Cycle 3 performed without the screws 4

Cycles on S/N FM 3 and FMS, the try to fasten S/N FM 3 to 1. 2 N. m failed FM 3 MMS SCM FRB, 20 APR 2012 FMS 5

S/N FM 4 X-ray inspection • • The PEEK tubes have been removed from the holder to see the cracks The crack is under the jaw Limits of secondary coil MMS SCM FRB, 20 APR 2012 6

• New run of thermoelastic analyses – Coefficient of thermal expansion of the Mapsil resin updated after characterization at CNES(real value 20 times larger than the one used in the previous simulations, 15 E-6 => 349 E 6) – Ultimate constraint for the ferrite cores measured at CNES and used in the simulations – Different torque values applied (0. 8, 1. 2 and 1. 4 N. m) – SY 00728_RP_1445_12_MMS_Mechanical_Analysis. pdf • • • No crack seen in simulation at 60°C, margins are quite high => this does not meet the experimental results The simulation will be updated with the 2216 solution, the geometry of the PEEK tubes will also be updated slightly Conclusion: – Thermoelastic effects are the source of the cracks – The fastening of the screws add constraints where the cores actually crack – The cores have never cracked when not fastened (either alone or mounted in the holder without fastening the screws as tested on S/N FM 3 and S/N FMS) – Thus, we propose to reduce the torque value (0. 35 N. m instead of 1. 2 N. m) and to add glue to avoid sliding during vibration qualifications => solution tested on the QM MMS SCM FRB, 20 APR 2012 7

Configuration tested in vibration • Tested at protoflight levels along the Z axis (highest levels) • 2216 glue added on both sides of the PEEK tubes • Screws fastened at 0. 35 N. m (instead of 1. 2 N. m) • No sliding detected • The screws do not moved MMS SCM FRB, 20 APR 2012 8

Update of the Workflow MMS SCM FRB, 20 APR 2012 9