ai-aerospace/ams_data_full_2000-2020 huggingface dataset:
191 References  

1. B. Chalmers , Principles of Solidification, 1964   2. K. S. Bagdasarov , Growth of Crystals , 1991   3. H. Horikawa, S. Ichinose, K. Morii, S. Miyazaki, K. Otsuka, Orientation Dependence of β1  β’1 Stress - Induced Martensitic Transformation in a Cu-Al -Ni Alloy : Metall. Trans., 1988, vol. 19A, pp. 915-923   4. Z.G. Wang, Z.F. Zhang, X.W. Li, W.P. Jia, S.X. Li, Orientation dependence of the cyclic deformation behavior  and the role of grain boundaries in fatigue damage in copper crystals : Materials Science and Engineering  A319– 321 (2001) 63–73  5. X P. Sittner, K. Hashimoto, M. Kato, M. Tokuda, Stress induced martensitic transformations in tension/torsion  of CuAlNi single crystal tube : Scripta Met. 48 (2003), pp. 1153-1159   6. T.W. Duerig, K.N. Melton, D. Stockel, C.M. Wayman, Engineering Aspects  of Shape Memory Alloys, pp. 234244, 1990
195 All test fasteners were inspected for smooth assembly and cleaned prior to tests . All test fasteners (i.e.,  cap screws, nuts and washers) and fixtures were cleaned using an ultrasonic cleaner with methyl ethyl  ketone (MEK) solvent for 5 minutes and allowed to air dry before testing.  

Test Procedures  

Tests include an initial  use test, reuse  without additional adhesive test, and reuse  with additional adhesive   test. The preparation procedures for these three tests are different, but the test procedure is the same as  listed below.  

Preparation for unseated initial use tests :  1) Apply 2 drops of anaerobic adhesive to cap screw threads.   2) Apply 1 drop of anaerobic adhesive to hex nut threads.   3) Assemble cap screw and hex nut until three full threads extend beyond nut.   4) Allow adhesive to cure for 48 hours on a lint free paper towel.   5) After curing time, wipe any excess adhesive from cap screw threads with a lint free paper towel.  

Test procedure for unseated initial use tests, unseated reuse without additional adhesive tests, and unseated reuse with additional adhesive tests :  1) Clamp head of cap screw in a vise.   2) Use 0- 75 in- lb (0-8.5 N -mm) dial -type torque wrench to apply torque to nut in counter -clockwise  direction gradually until motion is initiated. Record breakaway torque at the instant of motion.   3) Continue applying torque and record torque values at 2- 5, 90,180, 270, and 360 degrees.  

Preparation for unseated reuse without additional adhesive tests :  1) Remove hex nut completely from cap screw.   2) Reassemble hex nut to the same position as in initial use test.   3) Allow adhesive to cure for 48 hours on a lint free paper towel.  

Preparation for unseated reuse with additional adhesive tests :  1) Remove hex nut completely from cap screw.   2) Add 2 drops of anaerobic adhesive to cap screw threads.   3) Add 1 drop of anaerobic adhesive to hex nut thr eads.   4) Reassemble hex nut to the same position as in initial use test.   5) Allow adhesive to cure for 48 hours on a lint free paper towel.  

Test Data and Analysis  

All the  test data has been assembled in plots of measured removal torque in inch -pounds  versus removal  angle in degrees  [11]. The allowable range of prevailing torque for ¼ - 28 (M6x1)  thread size is between 3.5  and 30 in-lb per speci fication [1- 6]. This is indicated by horizontal dashed lines in the plots  for quick  assessment of results . Each plot includes dat a from 5 to 10 test fasteners. Overlap of data points in the  plots occurs.    Figure 1 shows three plots for the unseated grade 8 fasteners with Loctite 222MS for the initial use, reuse  without additional adhesive, and r euse with additional adhesive. This shows all removal torque  measurements were within the specification of 3.5 to 30 in- lb (0.40- 3.4 N -m) for initial use giving a 100%  pass rate for this fas tener and adhesive combination.  For reuse without additional adhesive, many torque  measurements fall below the specification, whereas for reuse with additional adhesive, only a couple fall  below specification. This data shows the effect of reuse with versus without additional adhesive.
197 Test data were presented as removal torque versus removal angle with required prevailing torque range  per specificat ion added for easy assessment. Percent pass rates for the various fastener material ,  anaerobic adhesive, and assembly condition combinations  were tabulated.  

The results of this work show:   1. Use of anaerobic adhesive as a prevailing torque locking feature is viable.   2. Not all possible fastener material and anaerobic adhesive combinations provide prevailing torque  values within specification. However, any combination can be assessed using the test procedures developed.   3. Reuse without additional anaerobic adhesive generally provides some prevailing torque, and in  some cases within specification. Note that a reuse test in this work follows complete disassembly,  reassembly and 48- hour cure time regardless of whether additional adh esive is used.   4. Reuse with additional  adhesive often provides comparable removal torque data as in initial use.  

Acknowledgement 

The authors gratefully acknowledge the funding and support of the NASA Engineering and Safety Center  (NESC) and Dr. Michael Dube for this work.      References  

1. NASM25027, Nut, self- locking, 250 oF, 450oF and 800oF, National Aerospace Standard, 1999.   2. NASM8846,  Inserts, screw -thread, helical coil , National Aerospace Standard, 1998.   3. MIL-I-45914A , Insert, screw thread –  locked in, key locked , Department of  Defense Military  Specification, 1991.   4. MIL-I-45932/1C,  Insert, screw thread –  thin wall, locked in , Department of Defense Military  Specific ation, 1994.   5. NAS3350, Nuts, self -locking, 450oF and 800oF, high quality , National Aerospace Stan dard, 2006.   6. MIL-DTL-18240F , Fastener element, self -locking, threaded fastener -  250oF maximum, Department of  Defense Detail Specification, 1997.   7. Hunter, R, Hess, D,  “Direct Verification of Threaded Fastener Locking Compounds and Adhesives,”  Journal of Failure Analysis and Prevention, 12 (2012),  724-729.  8. McManamen, J,  “Orbiter Window Fastener Issue Summary,” NASA SSP presentation, 2008 .  9. Roberts, T,  “Orbiter Window Installation Fasteners,” Uni ted Space Alliance presentation, 2008.   10. Zimandy, A, Hess, D , “Effect of Re -use of Locknuts with Prevailing Torque Locking Feature,” Journal  of Failure Analysis and Prevention (featured paper), 13  (2013),  121-127.  11. Hernandez, A,  Use of Anaerobic Adhesive for Prevailing Torque Locking Feature on Threaded  Product , Univer sity of South Florida MS Thesis, 2015.
198         

Figure 1 .  Unseated plain grade 8 with Loctite   222MS:  initial use, reuse without additional  adhesive,  and reuse with additional  adhesive.  Figure 2.  Unseated A -286 with Loctite 243:   initial use, reuse without additional  adhesive,  and reuse with additional adhesive.  

Breakaway    2-5 90 180 270 36005101520253035 Removal Angle (degrees)Removal Torque (in-lb) 00.511.522.533.5 Removal Torque (N-m) Breakaway    2-5 90 180 270 36005101520253035 Removal Angle (degrees)Removal Torque (in-lb) 00.511.522.533.5 Removal Torque (N-m) Breakaway    2-5 90 180 270 36005101520253035 Removal Angle (degrees)Removal Torque (in-lb) 00.511.522.533.5 Removal Torque (N-m) Breakaway    2-5 90 180 270 36005101520253035 Removal Angle (degrees)Removal Torque (in-lb) 00.511.522.533.5 Removal Torque (N-m) Breakaway    2-5 90 180 270 36005101520253035 Removal Angle (degrees)Removal Torque (in-lb) 00.511.522.533.5 Removal Torque (N-m)
209 an order of magnitude higher than the conformal subset. Clearly, the accuracy of the correlation is greatly  increased for the conformal subset.  

Example 2: Partially obscured subsets   In this example,  an obstruction is introduced into the data set that blocks a portion of the field of view , as  shown in Figure 3. The obstruction is created by removi ng a strip of each image in the sequence. Results  comparing the obstructed subset to the unobstructed results are also shown . The max difference between  the two tracked cases  is 0.5 degree , which occurs in the frame where the pawl velocity is the highest. In  this case , where tracking is performed with DICe, the obstruction can be masked off and the two sections  of the pawl are linked together as a single subset, leading to adequate trackable area. Note that performing this correlation using square subsets is not possible because too much of the subset becomes obstructed leading to de- correlation.  

   Figure 2.  Synthetic image rotation used to illustrate accuracy difference between conformal    and square subsets.  

Figure 3.  Rotation error computer for the synthetically generated data set using a conformal  subset comparing the unobstructed and obstructed cases   0 2 4 6 8 10-0.1-0.0500.050.10.15 SyntheticImageRotation(deg)RotationError(deg)    Conformal Square 0 Square 1 0 20 40 60 80-20-100Rotation(deg)    No Obstruction Obstruction 0 20 40 60 80-1.0-0.500.51.0 FrameNo.Di,erence(deg)
214   Figure 1.  Notional Spacecraft Incorporating CEFI in Stowed and Deployed Configurations   This innovative boom system will use three separate mechanisms . The central mechanism will have four  booms and sensors wrapped around a single hub (see Figure 2) . These four booms deploy 45° to the  sides of the spacecraft in a single plane. The remaining two booms deploy from individual mechanisms  on each end of the 3U volume. The central four -boom mechanism and the single- boom mechanisms are  shown in Figure 2. All six graphite composite booms and their tip sensors will be identical.  

Figure 2.  Notional 3U Instrument Layout  

Carbon Fiber Reinforced Composite Booms   The baseline booms are 2.5- m long with a diameter of 1.27 cm (0.5”) . Manufactured from graphite  composite, these booms are extremely lightweight, stiff and thermally stable. Instrument pointing stability  is a key requirement . It is estimated that stability nee ds to be within 0.1° between orthogonal pairs . The  CEFI Instrument Components Stowed 6U SpacecraftSix 2.5m long booms  deployed 4-boom  mechanism Single -boom  mechanismsNotional 3U Spacecraft LayoutCross- sectional  View of 4 -boom  mechanism
215 boom stiffness and thermal stability will enable this requirement to be met . In particular, the booms must  have significantly more deployed stiffness than typical CubeSat appendages, such as carpenter’s tape  springs or conventional slit -tube beams.  

One of the main reasons that CTD is capable of providing such a stable sensor platform is the patented  Slit-LockTM technology . Traditional slit -tube booms have low torsional stiffness, as well as reduced  bending stiffness and stability due to shear compliance at the seam . To address these issues, CTD has  developed Slit -LockTM technology (US Patent #8863369), which involves the locking of edge features,  such as those pictured in Figure 3 , as the boom deploys . By locking the edges, the slit -tube attains near  closed- section properties, drastically improving stability in both bending and torsion.  

Figure 3.  Slit-LockTM Technology Used to Improve Boom Structural Performance    Furthermore, Slit -Lock TM edge features are aligned when the boom is stowed, allowing them to be  engaged to keys on the end caps of the spool (see Figure 4) . The slot and key engagement guarantees  that the boom will spool and unspool at precisely the same rate every time. The engagement also allows  much higher  forces to be driven from the spool into the boom as it deploys, which increases margin of  safety on deployment torque.  

Figure 4.  Aligned Slit -LockTM Edge Features and Matching Keys on End Caps of Stowage Spool  

Figure 5.  Keyed Slit -LockTM Edge Features       

           Open slit tube for packaging and  deploymentSlit-lock™ engaged for maximum deployed  structural performance                   Keys on spool end plates engage  with Slit -Lock edge featuresFour  Stowed  Booms
216 The boom’s thermal stability also has a significant effect on the instrument’s performance. Solar flux  along the boom can result in a temperature gradient across the cross -section of the boom . This is  typically problematic for deployable spacecraft appendages, since this gradient can result i n significant  “thermal bending” . Fortunately, graphite composite booms can be designed so that the laminate has a  near-zero CTE, which enables pointing accuracy to be maintained despite potentially large on- orbit  thermal gradients . The baseline booms developed for CEFI  are estimated to experience less than a 0.1°  pointing shift as a result of thermal bending.  

Root -LockTM  CTD’s CubeSat boom technology further  enhances stability by enabling the boom to regain its full cross - section at the end of deployment, as illustrated in Figure 6. This is referred to as  “Root -Lock”  (patent  pending) . This root closure provides for high root stiffness and strength, which is particularly important for  maintaining the pointing accuracy of a very long and narrow boom . Typical slit -tube booms have a  “transition zone” where the  boom transitions from flat (on the spool) to curved, and the cross -section is  never able to fully recover, leaving the boom with reduced properties at the root . Spacecraft maneuvers  can therefore result in significant bending at the root . In CTD’s baselin e design, the beam is able to  transition off of the spool and clamp down around a root plug, providing the maximum amount of root  stiffness to the structure (see Figure 6) .  

Figure 6.  Root- LockTM enables boom to regain cross- section at end of deployment, drastically  improving root strength and stiffness.  

Actuation, Positional Feedback, and Deployment Verification   The baseline design involves driving out the booms with a small motor that is efficiently integrated within  the stowage spool of each unit . CTD has demonstrated the use of both stepper and DC motors (brushed  and brushless), depending on application requirement s. For this application, we have selected a brushed  DC motor with a 141:1 gear head and attached encoder . This motor consumes less than 5 W while  running at 12 V. Deployment time is expected to be less than 5 minutes , but can be tailored to be faster  or slower depending on the application requirements . The motor measures 16 mm in diameter, 45 mm in  Transition Zone Tip fully recovered and  “Slit Lock” feature engaged Root -Lock Clamp  secures root of boom  to Root PlugDuring Stowage/Deployment Fully Deployed
217 length and weighs less than 45 g total (motor, gear head and encoder combined) . The attached encoder  provides precise positional feedbac k and deployment verification.  

Fabrication and Demonstration of Prototypes  

Under NASA funding, CTD recently manufactured and demonstrated prototypes of both the single- boom  and quad- boom mechanisms, shown in Figure 7 and Figure 8, respectively . These  booms are 1.5-m long  and 12.7- mm (0. 5-in) diameter . Both mechanisms incorporate Slit -LockTM and Root -LockTM. These  mechanisms have been stowed and deployed several times without failure or anomalous behavior .  

Figure 7.  Single -boom Prototype  

Figure 8.  Quad -boom Prototype   1.5m  boom  length Deployed Stowed Fully Stowed Partially Deployed Fully Deployed
218 Both meet the form factor requirement for the CubeSat instrument. Stowed dimensions for each unit are  presented in Figure 9 and Figure 10.  

Figure 9.  Single -boom Unit Stowed Dimensions  

Figure 10.  Quad -boom Unit Stowed Dimensions     CTD is now working on integrating the tip- mounted sensors into these units . This will involve the  installation of an embedded, multi -conductor wire harness along the length of each boom that can be  rolled up with the structure. Furthermore, a slip ring will be implemented within the stowage spool of each unit such that sensor signals and power can be transferred across the rotating interface. CTD is also  currently developing miniaturized control electronics that can be incorporated into the 3U volume.
219 Conclusions  

Accurate measurements of vector electric fields in the ionosphere are vital to making progress towards  our understanding of the physics of the heliosphere. Housing a vector e- field instrument on a CubeSat   enables multi -point 3D electric field measurements to be economically made in this region. CTD is  therefore developing the deployment system for the CubeSat Electric Field Instrument , which is enabled  by CTD ’s deployable boom technology. Under NASA funding, CTD recently designed, manufactured and  successfully demonstrated this deployment system . Next steps for the technology include the  implementation of tip- mounted sensors, wiring harness, slip ring and miniaturized drive electronics. This  technology has wide applicability to many CubeSat applications, and could also be used as an antenna,  instrument boom (magnetometer, Langmuir probe, etc.), gravity gradient boom, or as the deployable  structure for a solar array, drag sail, solar sail, etc .
222 better resistance to oxidation than conventional sputter -deposited coatings, because the metals increase  the density of the coatings, and also "seal" the reactive edges of the MoS 2 crystallites.8,9 However,  quanti tative data on the extent of oxidation and its consequent effect on performance is lacking.  

The present study was initiated to address the risk of the FAM not being able to perform as required over  its mission cycle life due to potential exposure to relat ive humidity levels up to 60% for extended periods of  time. The study was conducted in real -time. We did not accelerate by increasing the temperature or  humidity because that would give non- quantitative results that could not be readily applied to real sys tems.  We investigated the effects of storing three types of sputter -deposited MoS 2-based coatings in air  at 59%  RH, all manufactured by Hohman Plating, Inc.: Ni -MoS 2, Au-Sb2O3-MoS 2, and Sb 2O3-MoS 2. Hohman   Plating supplies many of the spacecraft contractors in the U .S., including the coatings for the FAM : the  Sb2O3-MoS 2 coating was chosen for the FAM, while the ot her two coating versions were tested for  comparison purposes. Most of the FAM operation (both ground and on- orbit) will occur in inert environments  (i.e., N 2 or vacuum); a relatively small amount of testing will occur in air. The testing was conducted in an  inert environment (gaseous N 2) at exceptionally low humidity levels (<0.08% RH) to model these conditions .  Although the absolute endurance values may vary slightly from that obtained in vacuum, we are most  interested in measuring the relative amount of endurance degradation, which should be valid while testing  in N 2.  

Figure 1.  The Focus and Alignment Mechanism (FAM) provides tip, tilt and piston   for NIRCam’s Pick Off Mirror (POM)  

Previous  Studies into MoS 2 Aging and Oxidation  

This section reviews previous work concerning oxidation of MoS 2 solid lubricants  due to humid air exposure.  MoS 2 can oxidize during exposure to water vapor alone, to oxygen alone, and to water and oxygen together.  In general, at ambient storage temperatures, appreciable oxidation is unlikely with water or oxygen alone.  For pure oxygen reacting with MoS 2, oxidation only occurs at temperatures >300°C.10 The reaction of pure  water reacting with MoS 2 has been shown to proceed for temperatures above 780°C,11 and would probably  proceed negligibly at room temperature. However, wear of the film s while they are under a partial pressure  of H 2O can accelerate the reaction process. One study showed that H 2S was produced when rubbing  supported MoS 2 films under an atmosphere containing dry nitrogen (N 2) and H 2O gases at ambient  temperature.12 As such, either elevated temperature or mechanical wear is required to oxidize MoS 2 in a  humid atmosphere without oxygen present.
226 state of Mo since the most significant result of storage in humid air is to oxidize the lubri cating MoS 2 to  nonlubricating MoO 3, as discussed above.  For this study, a Physical Electronics Versaprobe II instrument  was used.  

In order to determine the composition variation with depth into the coatings, Ar+ sputtering depth profiles  were obtained using a 1 kV accelerating voltage. Ion bombardment has an unpre dictable effect  on chemical  state, and so it is difficult to quantitatively determine relative elemental amounts as well as chemical state  with depth. However, it is useful in providing semi -quantitative comparisons between materials.  

Friction and Endurance Results  

A typical friction trace for a Hohman Plating Ni -MoS 2 coating  tested before storing in humid air is shown in  Figure 3. The mean endurance for the Hohman Plating Ni -MoS 2 coating prior to humid air storage was  125,000 cycles. In contrast, the endurances for the Au- Sb2O3-MoS 2, and Sb 2O3-MoS 2 coatings were   2.2 mil lion and 3.3 million cycles, respectively, or 18 and 26 times the endurance for the Ni -MoS 2 coating.  It has previously been shown that the Sb 2O3-containing coatings performed better than the Ni -MoS 2 coating  when tested in an air environment.6 (In that study, tests conducted in dry N 2 were stopped prior to failure  for all coatings, so relative lifetimes in an inert environment were not obtained.)  

Figure 3.  A typical friction trace for a Hohman Plating Ni -MoS 2 coating tested before storing in  humid air . Data were obtained during pin -on-disk testing in a dry N 2 environment.  

Figure 4 shows endurance data for the Ni -MoS 2 coating for various storage times. Even considering the  large scatter of the data in the first 200 days, there is a clear reduction in endurance with stor age time.  The endurance continues to drop for longer storage times up to 827 days  (2.3 years) , although the rate of  decrease appears to slow with increasing storage time. The total reduction over 2.3 years is about 55%,  which represents a significant degra dation in the performance of this coating.
227   Figure 4.  Endurance of Hohman Plating Ni -MoS 2 coatings as a function of days stored in 59% RH  air. The endurance is defined as the number of cycles for which the COF is below 0.5. Each  data  point represents the mean of three tribometer runs  on one sample ; the error bars represent    the scatter of the three runs. There is a reduction  in endurance of about 55% for a storage   time of 2.3 years.  

The endurance data for the stored Au-Sb2O3-MoS 2 coating is shown in Figure 5 . For the early storage data  (i.e., ≤200 days), the trend in endurance with storage time is not clear; it is obscured by the scatter in the  data. However, over longer storage times (i.e., 1 an d 2.3 years ), the endurance is clearly lower than the  unstored coating. Furthermore , the endurance at 1 year and 2.3 year are comparable,  suggest ing there is  a reduction in the degradation rate of the coatings after 1 year  but more data would be needed to confirm  this. The total reduction over 2.3 years  is about 20%, considerably smaller than for the Ni -MoS 2 coatings.   Figure 6 shows corresponding data for the Sb 2O3-MoS 2 coatings. As for the similar Au- containing coating,  it also shows a reduction in endurance with storage time, i.e., by 17% over 419 days of storage  (1.1 years;  this coating was placed into stor age later than the other two, and so longer storage times are not available  at the time of this writing). Again the data suggests that the endurance may have stabilized.  

Figure 5.  Endurance of Hohman Plating Au -Sb2O3-MoS 2 coatings as a function of days  stored in 59% RH air . (See Figure 4 caption.) The endurance has reduced by about   30% for a storage time of 2.3 years.