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

2. Introduction History: – S/N QM SENSOR ferrite cores broke during the first vibration campaign, cracks located at the end of the cores – S/N EM4 SENSOR fully qualified at protoflight levels (change in vibration levels and in the test protocol, notching applied) – S/N FM1 SENSOR fully qualified at protoflight, delivered at UNH – S/N FM2 SENSOR fully qualified at protoflight, calibrated, to be delivered soon at UNH – S/N FM4 SENSOR chosen for the SCM FM3 delivery jointly with the S/N FM4 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 FM4 (1.4N.m) was different from the requested one (1.2N.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_FM4_SENSOR_cracks_after_vibration.doc MMS SCM FRB, 20 APR 20122

3. SCM Sensor Manufacturing Workflow MMS SCM FRB, 20 APR 20123 SENSOR S/N FM4 cracks detected at this step

4. 3 cycles have been performed at LPP on the S/N FM4 sensor => 2 cores broke 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 MMS SCM FRB, 20 APR 20124 12 3

5. Cycles on S/N FM3 and FMS, the try to fasten S/N FM3 to 1.2N.m failed MMS SCM FRB, 20 APR 20125 FM3FMS

6. S/N FM4 X-ray inspection The PEEK tubes have been removed from the holder to see the cracks The crack is under the jaw MMS SCM FRB, 20 APR 20126 Limits of secondary coil

7. 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, 15E-6 => 349E- 6) – Ultimate constraint for the ferrite cores measured at CNES and used in the simulations – Different torque values applied (0.8, 1.2 and 1.4N.m) – SY00728_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 FM3 and S/N FMS) – Thus, we propose to reduce the torque value (0.35N.m instead of 1.2N.m) and to add glue to avoid sliding during vibration qualifications => solution tested on the QM MMS SCM FRB, 20 APR 20127

8. 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 0.35N.m (instead of 1.2N.m) No sliding detected The screws do not moved MMS SCM FRB, 20 APR 20128

9. Update of the Workflow MMS SCM FRB, 20 APR 20129