scholarly journals Small-scale mechanical characterization of space-exposed fluorinated ethylene propylene recovered from the Hubble Space Telescope

2013 ◽  
Vol 32 (3) ◽  
pp. 602-607 ◽  
Author(s):  
Justin S. Jones ◽  
John A. Sharon ◽  
Jelila S. Mohammed ◽  
Kevin J. Hemker
Keyword(s):  
Mechanical Characterization ◽  
Hubble Space Telescope ◽  
Small Scale ◽  
Space Telescope ◽  
Ethylene Propylene ◽  
Fluorinated Ethylene Propylene

Environmental Exposure Conditions for Teflon® Fluorinated Ethylene Propylene on the Hubble Space Telescope

2000 ◽  
Vol 12 (1) ◽  
pp. 125-139 ◽  
Author(s):  
Joyce A Dever ◽  
Kim K de Groh ◽  
Bruce A Banks ◽  
Jacqueline A Townsend ◽  
Janet L Barth ◽  
...  
Keyword(s):  
Environmental Exposure ◽  
Hubble Space Telescope ◽  
Low Earth Orbit ◽  
X Rays ◽  
Space Telescope ◽  
Ethylene Propylene ◽  
Temperature Ranges ◽  
Absorbed Radiation Dose ◽  
Fluorinated Ethylene Propylene ◽  
Exposure Conditions

The outer layer of Teflon® fluorinated ethylene propylene (FEP) multi-layer insulation (MLI) on the Hubble Space Telescope (HST) was observed to be significantly cracked at the time of the Second HST Servicing Mission (SM2), 6.8 years after HST was launched into low Earth orbit (LEO). Comparatively minor embrittlement and cracking were also observed in the FEP materials retrieved from solar-facing surfaces on the HST at the time of the First Servicing Mission (3.6 years exposure). After SM2, a failure review board was convened to address the problem of degradation of MLI on the HST. In order for this board to determine possible degradation mechanisms, it was necessary to consider all environmental constituents to which the FEP MLI surfaces were exposed. Based on measurements and various models, the environmental exposure conditions for the FEP surfaces on the HST were estimated, including: the number and temperature ranges of thermal cycles; equivalent sun hours; fluence and absorbed radiation dose of x-rays, trapped protons and electrons and plasma electrons and protons; and atomic oxygen (AO) fluence. This paper presents the environmental exposure conditions for FEP on the HST, briefly describing the possible roles of the environmental factors in the observed FEP embrittlement and providing references to the published works which describe in detail testing and analysis related to FEP degradation on the HST.

USE OF SPATIOTEMPORAL DIAGRAMS TO CHARACTERIZE A SILO DISCHARGING PROCESS

2013 ◽  
Vol 37 (1) ◽  
pp. 53-70
Author(s):  
Blaise Nsom ◽  
Noureddine Latrache
Keyword(s):  
Cross Section ◽  
Flow Rate ◽  
Mechanical Characterization ◽  
Direct Method ◽  
Rectangular Cross Section ◽  
Small Scale ◽  
Flat Bottom ◽  
Shear Box ◽  
A Direct Method

To get a better knowledge of discharging flows of ensiled granular materials, a small scale silo was designed and built. It is equipped with a flat bottom and it has a rectangular cross section. Moreover, it is entirely transparent for image processing purpose. First of all, a physical and mechanical characterization of wood granules (inert materials) was performed using a shear box testing. Then, silo emptying flows were generated. Flow regimes and flow rate were determined using spatiotemporal diagrams extracted from images of the free surface of the ensiled material. The same method was then used to measure the flow rate of discharging flows of soya, colza and rye seeds which were characterized in a previous study. For each material studied, the flow rate measured with this non intrusive method was successfully compared with a direct method consisting in weighing a volume of grains discharged during a unit time and with Berveloo’s formula.

scholarly journals Mechanical Characterization of Timber-to-Timber Composite (TTC) Joints with Self-Tapping Screws in a Standard Push-Out Setup

2020 ◽  
Vol 10 (18) ◽  
pp. 6534
Author(s):  
Chiara Bedon ◽  
Martina Sciomenta ◽  
Massimo Fragiacomo
Keyword(s):  
Mechanical Characterization ◽  
Numerical Models ◽  
Three Dimensional ◽  
Analytical Models ◽  
Small Scale ◽  
Load Bearing ◽  
Timber Constructions ◽  
Technical Interest ◽  
Push Out

Self-tapping screws (STSs) can be efficiently used in various fastening solutions for timber constructions and are notoriously able to offer high stiffness and load-carrying capacity, compared to other timber-to-timber composite (TTC) joint typologies. The geometrical and mechanical characterization of TTC joints, however, is often hard and uncertain, due to a combination of various influencing parameters and mechanical aspects. Among others, the effects of friction phenomena between the system components and their reciprocal interaction under the imposed design loads can remarkably influence the final estimates on structural capacity, in the same way of possible variations in the boundary conditions. The use of Finite Element (FE) numerical models is well-known to represent a robust tool and a valid alternative to costly and time consuming experiments and allows one to further explore the selected load-bearing components at a more refined level. Based on previous research efforts, this paper presents an extended FE investigation based on full three-dimensional (3D) brick models and surface-based cohesive zone modelling (CZM) techniques. The attention is focused on the mechanical characterization of small-scale TTC specimens with inclined STSs having variable configurations, under a standard push-out (PO) setup. Based on experimental data and analytical models of literature, an extended parametric investigation is presented and correlation formulae are proposed for the analysis of maximum resistance and stiffness variations. The attention is then focused on the load-bearing role of the steel screws, as an active component of TTC joints, based on the analysis of sustained resultant force contributions. The sensitivity of PO numerical estimates to few key input parameters of technical interest, including boundaries, friction and basic damage parameters, is thus discussed in the paper.

Molecular and mechanical characterization of reactive ethylene-propylene elastomers and their use in PA6-based blends

Polymer ◽  
1992 ◽  
Vol 33 (14) ◽  
pp. 2940-2948 ◽  
Author(s):  
M. Abbate ◽  
V.Di Liello ◽  
E. Martuscelli ◽  
P. Musto ◽  
G. Ragosta ◽  
...  
Keyword(s):  
Mechanical Characterization ◽  
Ethylene Propylene

Initial Characterization of Active Transitioning Centaur, P/2019 LD2 (ATLAS)

2021 ◽  
Author(s):  
Bryce Bolin ◽  
Yanga Fernandez ◽  
Carey Lisse ◽  
Timothy Holt
Keyword(s):  
Cross Section ◽  
Hubble Space Telescope ◽  
Gas Production ◽  
Wide Field ◽  
Imaging Spectrometer ◽  
Space Telescope ◽  
Resolution Imaging ◽  
Array Camera

<p>We present visible and mid-infrared imagery and photometry of temporary Jovian co-orbital comet P/2019 LD2 taken with Hubble Space Telescope/Wide Field Camera 3 (HST/WFC3), Spitzer Space Telescope/Infrared Array Camera (Spitzer/IRAC), and the GROWTH telescope network, visible spectroscopy from Keck/Low-Resolution Imaging Spectrometer (LRIS), and archival Zwicky Transient Facility observations taken between 2019 April and 2020 August. Our observations indicate that the nucleus of LD2 has a radius between 0.2 and 1.8 km assuming a 0.08 albedo and a coma dominated by ∼100 μm-scale dust ejected at ∼1m s−1 speeds with a ∼1'' jet pointing in the southwest direction. LD2 experienced a total dust mass loss of ∼108 kg at a loss rate of ∼6 kg s<sup>−1</sup> with Afρ/ cross-section varying between ∼85 cm/125 km<sup>2</sup> and ∼200 cm/310 km<sup>2</sup> from 2019 April 9 to 2019 November 8. If the increase in Afρ/cross section remained constant, it implies LD2ʼs activity began ∼2018 November when within 4.8 au of the Sun, implying the onset of H2O sublimation. We measure CO/CO<sub>2</sub> gas production of <10<sup>27</sup> mol s<sup>−1</sup>/<10<sup>26</sup> mol s<sup>−1</sup> from our 4.5 μm Spitzer observations; g–r = 0.59 ± 0.03, r–i = 0.18 ± 0.05, and i– z = 0.01 ± 0.07 from GROWTH observations; and H2O gas production of <80 kg s<sup>−1</sup> scaling from our estimated C<sub>2</sub> production of Q<sub>C2</sub> < 7.5 x 10<sup>24</sup> mol s<sup>−1</sup> from Keck/LRIS spectroscopy. We determine that the long-term orbit of LD2 is similar to Jupiter-family comets having close encounters with Jupiter within ∼0.5 Hill radius in the last ∼3 y and within 0.8 Hill radius in ∼9 y. Additionally, 78.8% of our orbital clones are ejected from the solar system within 10<sup>6</sup> yr, having a dynamical half-life of 3.4 × 10<sup>5</sup> yr.</p>

Characterization of infrared filters for the wide-field camera 3 of Hubble Space Telescope

2001 ◽  
Author(s):  
Rene A. Boucarut ◽  
Manuel A. Quijada ◽  
Olivia L. Lupie ◽  
Sharon M. Struss ◽  
Linda A. Miner
Keyword(s):  
Hubble Space Telescope ◽  
Wide Field ◽  
Space Telescope

scholarly journals Small Scale Mechanical Characterization of Thin Foil Materials via Pin Load Microtesting

2015 ◽  
Vol 55 (7) ◽  
pp. 1375-1387 ◽  
Author(s):  
R. Wheeler ◽  
A. Pandey ◽  
A. Shyam ◽  
T. Tan ◽  
E. Lara-Curzio
Keyword(s):  
Mechanical Characterization ◽  
Thin Foil ◽  
Small Scale
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