ai-aerospace/ams_data_full_2000-2020 huggingface dataset:
A sample of image files from the FLIR are shown in Figure 5 where a photo of the flex tape is shown for  reference and images from the cases where only trace #1 is powered, traces 1-7 are powered, and all traces are powered. In each case, 10 A is applied to every trace. Data like these were taken for 10 A applied to traces in the series 1, 1-2, 1-3 and so on until all traces were powered. Similar data were gathered for the cases where only trace 1 is powered, then only trace 2 and so on thru trace 6. These results are given in Figure 7.  Figure 5. FLIR images of flex tape tests. Leftmost image is a photogr aph of a segment of the flex  tape tested shown for context. The other images, left to right, are of trace#1 (bottommost trace)  active, traces 1-7 active, and all thirteen traces active. The numerical results from the series of images in Figure 5 are given in Figure 6. This graph shows the  progression of the maximum temperature rise in the flex tape as more and more traces are energized. Here we can see that when three or fewer traces are energized near the edge of the tape the maximum temperature is less than the other cases. In every other case shown, the maximum temperature is relatively unchanged. This result is expressed in Figure 8 as a derating factor similar to those defined in  MIL-STD-975. 0 20 40 60 80  0 10 20 30 40 50 60 70 Temperature Rise, °C  Position Width of Tape, mm  165
Figure 6. Temperature profiles across the width of th e flex tape. Starting at the right side of the  graph trace number one has 10A applied, the next data set is with two traces activated, and so  on until all thirteen are active with 10A (cor responding to right-most image in Figure 5)  Figure 7. 3D plot of temperature output file fr om FLIR converted in Excel and corresponding to  the single trace image in Figure 5. The graph to the right shows the results from individual,  discrete loading of tapes 1-6 showing the more benign maximum temperatures associated  with moving the active trace toward the center of the flex tape. 0 20 40 60  Width Direction Temperature, °C  Length  Direction 0 10 20 30 40 50  0 20 40 60 Temperature Rise, °C  Position Width of Tape, mm  166
Figure 8. Results of trace loading tests (from Fi gure 6) represented as a derating factor and  compared to MIL-STD-975.  Remarks and Conclusions More work will need to be done in order to fully characterize and draw definitive conclusions about the  thermal relationship between individual traces and their adjacent traces with flex tapes in other common configurations (trace widths, thicknesses and spacing) but for this particular tape we have found the  following: 1. Radiative cooling of exposed (not wound into a twist capsule) flex tape can be substantial and the  results of these tests, or any not done in a flight-like configuration, should be taken in context.Traces of the dimensions used in these tests should not be used at 10 A in a flight twist capsule configuration. In fact, for the application for which these particular tapes were designed and used the maximum current is 2.5 A per trace. 2. Interior traces run cooler than exterior traces. Those traces in the middle of the tape spread heat  across several adjacent neighbor traces; those on the edges of a tape can only dissipate heat in one direction and can be several degrees hotter than equivalently loaded interior ones. 3. Traces on a single tape do not follow the rules for leadwire bundle derating per MIL-STD-975.  Once more than three adjacent traces are fully loaded, the maximum temperature rise in the tape  has reached its maximum, though placeing active traces on either side of a tape, keeping the middle for low power traces, should result in lower overall temperatures. A practical application of conclusion 3 above is that the conservative current rating approach outlined at  the beginning of this article can be modified for cases where the power traces can be allocated in groups of three or less. More work needs to be done with other flex tapes and rating models updated in order to determine how this relief should be applied. References 1. Military Standard. “NASA Standard Electrical, Electronic, and Electromechanical (EEE) Parts  List”, MIL-STD-975L, 31 January 1994. 2. Military Standard. “Printed Wiring Board, Flexible or Rigid-Flex, General Specification For”, MILP-50884E, 1 September 2010. 3. Hayes, Ron L and Blair R Allen. “Temperature-Based Current Derating of Monofilament Slip Ring  Brush Wire for Space Applications.” /g23/g22 /g85/g71/g3 /g44/g81/g87/g72/g85/g81/g68/g87/g76/g82/g81/g68/g79/g3 /g54/g36/g48/g51/g40/g3 /g54/g92/g80/g83/g82/g86/g76/g88/g80/g3 /g68/g81/g71/g3 /g40/g91/g75/g76/g69/g76/g87/g76/g82/g81 , Volume 43, May 31-June 4, 1998, pp. 1883-1893.0.3 0.4 0.5 0.6 0.7 0.8 0.9 1 1.1  0 2 4 6 8 10 12 14 16 18 20 Bundle Derating Factor  Number of Active Conductors Results from this study  MIL-STD-975  167
Design of 3D-Printed Tita nium Compliant Mechanisms Ezekiel G. Merriam*, Jonathan E. Jones**, and Larry L. Howell*  Abstract This paper describes 3D-printed titanium compliant mechanisms for aerospace applications. It is meant  as a primer to help engineers design compliant, multi-axis, printed parts that exhibit high performance. Topics covered include brief introductions to both compliant mechanism design and 3D printing in  titanium, material and geometry considerations for 3D printing, modeling techniques, and case studies of  both successful and unsuccessful part geometries. Key findings include recommended flexure geometries, minimum thicknesses, and general design guidelines for compliant printed parts that may not be obvious to the first time designer. Introduction A compliant mechanism derives its motion from the deflection of its constituent members. Compliant  mechanisms offer decreased part count, decreased complexity, lower weight, longer life, and lower cost.Since compliant mechanisms can be designed with no surface contact, wear and all its associated issues are eliminated. In many cases, bearings may be eliminated, along with their weight, complexity, and failure modes [1]. Preliminary work has shown the applicability of compliant mechanism technology to space applications [2]. Additionally, compliant mechanisms lend themselves to monolithic construction through additive manufacturing processes. Advances in Electron Beam Melting (EBM) enable additive manufacturing (also referred to as rapid  manufacturing) in a variety of metals, including alloys of Titanium. The EBM process is well documented  [3] [4]. Case studies have shown that rapid manufacturing offers reduced costs when production volumes  are low, many design iterations are to be explored, high geometric complexity is needed, or when new materials are to be explored [5] [6]. Additionally, material scrap rate can be significantly reduced by printing a near-net-shape part rather than machining it from solid billet [7]. Combining compliant  mechanisms with rapid manufacturing techniques opens up interesting possibilities for creating compliant  space mechanisms that have unprecedented performance.   *Brigham Young University, Provo, UT **NASA Marshall Space Flight Center, Huntsville, AL /g51/g85/g82/g70/g72/g72/g71/g76/g81/g74/g86/g3/g82/g73/g3/g87/g75/g72/g3/g23/g21/g81/g71/g3/g36/g72/g85/g82/g86/g83/g68/g70/g72/g3/g48/g72/g70/g75/g68/g81/g76/g86/g80/g86/g3/g54/g92/g80/g83/g82/g86/g76/g88/g80/g15/g3/g49/g36/g54/g36/g3/g42/g82/g71/g71/g68/g85 /g71/g3/g54/g83/g68/g70/g72/g3/g41/g79/g76/g74/g75/g87/g3/g38/g72/g81/g87/g72/g85/g15/g3/g48/g68/g92/g3/g20/g23/g16/g20/g25/g15/g3/g21/g19/g20/g23Figure 1. A compliant titanium hinge  produced with EBM. This hinge is capable of ±90° of motion. Images provided courtesy of Robert Fowler. [8] 169
Allowable Stress Two grades of titanium powder are currently produced for use in EBM machines: Ti6Al4V and Ti6Al4V  ELI (ELI is “extra low interstitials,” which improves ductility and fracture toughness of the alloy). These two  alloys have slightly different strength characteristics, but Ti6Al4V has slightly higher strength [13]. Table 1 presents strength data from several sources. These data were gathered from samples prepared in  different ways; some used highly polished samples while other samples are tested in the as-built condition, with no post-processing or heat treatment. Rafi et al, found a strong correlation between build orientation and strength [14], while the manufacturer data make no distinction between build orientations [13].  Table 1. Summary of strength data gathered from other sources.  (*) indicates that sample underwent HIP process. Material Sy Sut Se Notes Ti6Al4V 950 1020 600* Manufacturer data [13] Ti6Al4V ELI 930 970 600* Manufacturer data [13] Ti6Al4V ELI 782 842 120 As-built vertical [14] Ti6Al4V ELI 844 917 225 As-built horizontal [14] Ti6Al4V ELI 869 928 325 Machined vertical [14] Ti6Al4V ELI 899 978 300 Machined horizontal [14] Geometry Constraints Feature Geometry Minimum wall or flexure thickness depends on feature orientation. A minimum thickness of 0.75 mm is  recommended for flexures that have the thickness orthogonal or parallel to the build direction. If the flexure is built at other angles, 1.00 mm is recommended as the minimum thickness. If the flexure is built  at some angle from the vertical, the larger dimension is recommended. Figure 3a illustrates this  orientation dependence. The authors have had good success building flexures that rise at 45° from the  horizontal when the flexures are 1.00-mm thick.  (a) (b) Figure 2.  (a) - Flexures built at angles not orthogona l or parallel to build plate should be slightly  thicker. (b) - Horizontal flexure s build more successfully when supported by build plate as shown  on the right. Thermal Stresses and Part Warping Because the build chamber is maintained at between 500°C and 700°C, most stresses are relieved  during the part’s build cycle [11, 3], but some warping due to thermal stresses has been observed. Figure  4 shows a part where enough warping occurred that the part failed to build correctly. Although not fully  understood, it is thought that this warping is due to stresses that occur when the molten metal solidifies but are subsequently relieved as the part is held at high temperature. Usually the part is bulky enough  171
that these low stresses do not cause warping. For the geometry shown in Figure 4, the part was  redesigned to have the flexures rest on the build plate (illustrated in Figure 3b). Supporting the flexures in this way eliminated the warping and allowed a successful build. It is postulated that other ways to avoid warping include better support of the cantilevered flexure from underneath (by having it connect to another portion of the part) or making it wider. In general, narrow, unsupported flexures are to be avoided.  Figure 3. Build failure due to warping of slender flexures. Manufacturing Clearances Clearances are important to ensure that the completed mechanism can move freely, without fusing  sections that should move relative to one another. On a number of mechanisms with small (<2 mm) gaps, the final gap dimension was significantly less than was specified in the part file. Additionally, gaps must be wide enough that un-melted powder can be easily removed to allow motion in the mechanism. Experience with successful mechanisms suggests a minimum gap of 1.0 mm. The final gaps are less than the specified gap. In one instance, a gap as small as 0.66 mm was specified and the part successfully printed without fusing the two sections together; the measured clearance was 0.23 mm. These clearances were measured in the horizontal direction (parallel to the build plate). Vertical  clearances should be specified larger, especially in areas where powder removal is difficult. Powder and Support Removal Another design consideration is that the geometry must allow for removal of un-melted powder and any  support structure. Closed geometries should be avoided, or openings should be provided to allow access to loosen packed powder with hand tools or media blasting. In some cases this may not be possible, and  post machining using special fixtures or tooling must be used. Figure 5 shows the tooling required to  allow machining the inside of a particular feature. In another case example, a linear spring was printed that consisted of Bellev ille washers stacked end-to -end. The internal areas of the spring were  inaccessible, but by using a press to compress the spring, enough powder was removed from between each washer segment to allow the spring to function as intended.  172
Figure 4. The 2 DOF pointer mechanism in fixture for removal of powder  and supports from inside a split-tube flexure. Summary The following checklist can be used for designing compliant mechanisms for EBM manufacturing: Select minimum thickness for desired flexure orientation (0.75 mm for horizontal or vertical  flexures and 1.0 mm for other angles)  Find flexure length sufficient to bring stress into allowable range, subject to deflection and  thickness Select flexure width to support applied loads without requiring excessive actuation torque Ensure minimum gap width is observed (1.0 mm) Ensure horizontal flexures are supported at both ends Ensure that geometry allows powder removal If post-machining is necessary, provide geometry for fixturing Orient part so that every feature is built up from build plate or supported in some way Acknowledgements This work was supported by a NASA Office of the Chief Technologist’s Space Technology Research  Fellowship. The support of NASA Marshall Space Flight Center in the fabrication of titanium parts is gratefully acknowledged. 173
Magnetic Gearing versus Conv entional Gearing in Actuators  for Aerospace Applications Gregor Puchhammer* Abstract Magnetic geared actuators (MGA) are designed to perform highly reliable, robust and precise motion on  satellite platforms or aerospace vehicles. The design allows MGA to be used for various tasks in space  applications. In contrast to conventional geared drives, the contact and lubrication free force transmitting elements lead to a considerable lifetime and range extension of drive systems. This paper describes the fundamentals of magnetic wobbling gears (MWG) and the deduced inherent characteristics, and compares conventional and magnetic gearing. Introduction Actuators are widely used on satellite platforms and will be a necessity for future space missions. There  are numerous potential applications of actuators, such as antenna and solar arrays steering, robotic  arms, rovers, and optical instrumentation. Gearboxes with conventional toothed gear wheels are the  state-of-the-art solution for such actuator gears. Mechanical gear performance is highly affected by the  vacuum conditions and wide temperature range of the space environment [1]. During launch, high  vibrational loads and fretting leads to contact adhesion due to wearing-out of solid lubricants. In vacuum,  evaporation leads to loss of oil and a subsequent contamination of satellite surfaces or optical  components. Additionally, radiation can degrade some polymers or oxidize solid lubricants. Extended  temperatures can cause an ineffective lubrication at temperature extremes. However, these gears require  some sort of lubrication to maintain functionality throughout their entire lifetime. Figure 1.  MWG with Hollow Input and Output Shaft The problem of compromised lifetime and degradation in gears can be identified as a problem of  contacting surfaces and their proper lubrication [1]. In different kinds of gears, sliding contact is a critical  issue. Friction losses and wear often limits the efficiency and lifetime. As it is commonly known,  lubrication and space tribology are still areas of intense research aimed at reducing the effects of wear and tear. Until now, these harsh environmental conditions and the availability of appropriate lubricants often make it difficult to fulfill these needs in a satisfying manner. *Karl Rejlek GmbH, Vienna, Austria /g51/g85/g82/g70/g72/g72/g71/g76/g81/g74/g86/g3/g82/g73/g3/g87/g75/g72/g3/g23/g21/g81/g71/g3/g36/g72/g85/g82/g86/g83/g68/g70/g72/g3/g48/g72/g70/g75/g68/g81/g76/g86/g80/g86/g3/g54/g92/g80/g83/g82/g86/g76/g88/g80/g15/g3/g49/g36/g54/g36/g3/g42/g82/g71/g71/g68/g85 /g71/g3/g54/g83/g68/g70/g72/g3/g41/g79/g76/g74/g75/g87/g3/g38/g72/g81/g87/g72/g85/g15/g3/g48/g68/g92/g3/g20/g23/g16/g20/g25/g15/g3/g21/g19/g20/g23 175
Magnetic Wobbling Gears No contact, no sliding, no need of lubrication!  This is the simple answer to overcome lubrication problems in general, and particularly in space-related  issues. Triggered by an idea for powerful and quiet actuation drives, the MWG emerged several years  ago with astonishing properties. Beside quietness, which is not a main focus for space-related  applications, the non-contact power transmission particularly seems to match most of the needs in space.Once the problem of lubrication has been overcome due to the lack of lubrication needs, the usual boundaries of conventional gearing no longer exist. Temperature ranges, lifetime cycles, and wear and  tear problems are transferred to the question of proper dimensioning of bearings, where well-established  solutions exist, starting from few Kelvins in cryogenic temperatures up to a few hundred degrees Centigrade for extended temperature ranges. MWG Background For a short time, conventional gears can be replaced by powerful magnetic gearing systems. In magnetic  gears, the traditional load- and friction-bearing elements are replaced by preferably strong permanent magnets to transmit energy. There is absolutely no contact between the acting magnetic surfaces. The gearing parts are friction free and perform consistently without lubrication.  Regarding magnetic gearing in general, there are many different functional principles comparable to  those in conventional gears. Besides the proposed MWG system, possible candidates for magnetic gears include magnetic worm gears, magnetic spur gears, magnetic bevel gears, magnetic planetary gears, magnetic cycloid gears and even magnetic superconducting harmonic gears. Table 1 shows a  comparison of the performances of torque conversion devices with respect to different criteria. Table 1.  Comparison of Magnetic Gears Torque Conversion Device / Year From: [5] Torque  Density  [Nm/l]  Magnetic  Syst TD [Nm/l Magnetic  Syst TD [Nm/kg]  Maximum Torque  [Nm] Torque  Stiffness  [Nm/rad] Gear  Ratio Magnetic worm gear / 1993[5]2 2 Magnetic spur gear / 1974[5]20 20 10 Liquid cooled PM BL machine[5]30 30 1 Magnetic planetary gear / 1991[5]90 90 8 2-stage high ratio magnetic cycloid gear / 2006 [4]75 120 360 1-stage low ratio magnetic cycloid gear / 2006 [4]183 295 20 Harmonic magnetic gear / 2007[5]110 - 210–860 Magnetic superconducting harmonic drive / 2013[3]5 0–1 0 0 5 0–1 0 0 MWG, Type B (fully magnetic) / 2009[2]135 350 58 11 250 45 MWG, Type C (fully magnetic) / 2009 [2]11 250 2025 MWG, Type B (fully magnetic) / 2012 [2]170 500 82 50 1250 49 MWG, Type A / 2013 [2]605 110 55 2500 51 MWG, Type A / 2014 (targeted data) (>110) (35) (5000) 120 176
Selection criteria for the ‘best suited in space’ magnetic gear are shown in Table 1. As the required  amount of space on a satellite platform seems to be of importance, weight is of much higher priority. To get an idea of the magnetic performance, the magnetic system torque density rated in [Nm/kg] describes the amount of material of the magnetic system itself, which is necessary to produce the maximal torque. Itconsists of magnets and back iron, and defines the weight. This seems to be an effective way to comparethe power of different torque conversion devices, including conventional gearing systems as well as  magnetic systems in general and magnetic gearing systems alone. This is also a better method than  regarding only the magnetic system, rated in [Nm/l], without bearings but including the amount of internal  magnetic working range.  Different Types of MWG There are several possibilities for setting up a magnetic gear based on wobbling kinematics (Fig. 2). As  basic kinematics, a wobbling motion must be generated by a rotating input shaft, which has a cranked  region (dash-dotted line) onto which the wobbling bearing (not shown in Fig. 2) is fixed. The outer race of  the bearing is coupled with the magnetic wobbling wheel (Wh2, Wh2-3). The input shaft is rotating with  the input speed. The wobbling wheel performs the wobbling motion with the same frequency as the input  shaft, and has a superimposed rotation with the reduced speed of the output shaft. Both magnetic wheels (Wh1, Wh2) are magnetically coupled over an air-gap and perform the magnetic gearing due to a  difference in ‘magnetic pole pairs on wheel’ numbers between them. The gear ratio in MWG can be  computed in the same simple manner as for conventional wobbling gears by substituting the number of teeth with the number of ‘pole pairs on wheel’. Whereas the basic kinematics of wobbling gears is the  same for all three MWG types, there are some possibilities for generating the actual output shaft rotation. As the wobbling wheel’s useful output rotation is superimposed by the wobbling motion, a functional  element for ‘dewobbling’ action is needed for all three MWG types.  Figure 2.  Working Principle of Three Different Types of MWG /g120Type A consists of two single magnetic wheels. Wheel1 (Wh1) is fixed within the gear housing.  Wheel2 (Wh2) generates the output motion by magnetic gearing. The ‘dewobbling’ motion is done by a universal joint, such as a cardan or a homokinetic joint, coupled between Wheel2 and the output  shaft.   /g120Type B shows a MWG with three different types of magnetic wheels. Whereas Wheel1 and Wheel2  are acting in the same manner as in Type A, Wheel4 (Wh4) is part of the output shaft. The  ‘dewobbling’ motion is performed by the magnetic clutch setup of the wheel-pair Wh2 and Wh4. 177
MWG Compared to State-of-the-art Mechanical Gears Due to different available data of gears it is difficult to compare gears one with another. All data were  taken from actual catalogues, and all gears were compared with the same reduction ratios, the same nominal torques and the same operating conditions, if possible. As seen in [6] and [7], there are many different definitions of torsional loads: ‘Limit for momentary peak  torque’, ‘Limit for repeated peak torque’, ‘Limit for average torque’, ‘Rated torque at rated speed’, or ’Limit for maximum overload torque’. In MWG, there is only one limiting torque, the so-called ‘Maximum  Torque’. Therefore, the definition of different rated torques is no longer necessary in MWG. Figure 3.  Torsional Stiffness with Blocked Input Shaft at Gear Ratio=100 and Nominal Torque=50 Nm: MWG, HFUC and Planetary Gear  Figure 4.  Hysteresis Loss of MWG (i=45, 11Nm) 179