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Dynamic Testing of Check Valve for Cryogenic Pump
Tahseen Kanwal(타신),M. A. Trimzi(모지즈),B. C. An(안병철),H. U. Kim(김홍욱),J. H. Park(박중호),Y. B. Ham(함영복) 유공압건설기계학회 2021 유공압건설기계학회 학술대회논문집 Vol.2021 No.11
Check valves are an important component in any hydraulic system. Cryogenic liquids have very low viscosity and also at cryogenic temperature, material shrinks and hardened which increases the sealing gaps dramatically. In this article, we discuss the relation between the flow rate and pressure drop for the check valve used in a high-pressure cryogenic pump. Also, we did a simulation to check the leak and analyze the check valve with and without spring at two different testing conditions: normal closed and with the varying flow direction. We found from the simulation that leakage in the normally closed position is almost zero even at high pressure which is quite different from the real scenario. This result is due to the ideal conditions used by simulation software. We also shown quantitatively that time to change of direction of flow is more for high pressure and it is low as the frequency of proportional directional control valve changes.
Tahseen Kamal,박수영,박정현,장영욱 한국고분자학회 2012 Macromolecular Research Vol.20 No.7
The structural evolution of poly(ether-b-amide12) (PEBAX®) elastomers was studied by using wide angle X-ray scattering (WAXS) at a synchrotron radiation source during the uniaxial stretching. The changes in the crystal structure of the nylon 12 were tracked during the stretching of the P6333 and P2533 compressed films, which represent a hard rubber and a soft elastomer, respectively. The nylon 12 chains of both samples favored the γ-phase in the unstrained state but their responses to the external drawing force were different. For the P6333 film containing small amounts of the soft segments, the applied force dilated the 001 crystalline lattice plane of nylon 12 which is perpendicular to its main chain and the γ form was transformed into the α" form when the applied force was high enough. However, for the P2533 containing large amounts of the soft segments, the lattice dimensions of the nylon 12 crystals did not change with the external drawing force and the transient α" form was not observed. These results might suggest that the transfer of the external force to the crystal was difficult for P2533 due to the chain relaxation of the soft segments.
Kamal, Tahseen,Shin, Tae Joo,Park, Soo-Young American Chemical Society 2012 Macromolecules Vol.45 No.21
<P>The structural evolution of poly(ε-caprolactone) (PCL) during uniaxial tensile deformation at 25 °C was examined using small- and wide-angle X-ray scatterings (SAXS and WAXS) techniques with simultaneous stress and strain (S–S) curves. A high-energy X-ray beam at the recently upgraded Pohang synchrotron radiation source revealed the complete lamellar deformation behavior of PCL. Slope-based division of the S–S curves indicated three distinct regions of elastic (region I), yielding (region II) and plastic deformations (region III). In region I, which showed elastic deformation, the WAXS patterns were isotropic, whereas the SAXS patterns became oblate due to elongation of the amorphous chains along the draw direction. In region II, which showed yielding deformation, the WAXS patterns showed a slight orientation, whereas the SAXS patterns exhibited a change from oblate to four-point and to six-point patterns due to the simultaneous fragmentation and melting of the chain-folded lamellae (leading to the four-point pattern) and the subsequent formation of chain-extended lamellae (adding another two maxima along the meridian). In region III, the WAXS patterns revealed the development of the orientation of PCL crystals, whereas SAXS patterns exhibited a two-point pattern. The newly formed chain-extended lamellae in regions II and III might produce network junctions that can transfer an applied force to the PCL crystals for increased orientation. The six-point pattern in region II for PCL was not observed or reported in the past during the uniaxial tensile deformation experiment. This might be due to fast acquisition of the X-ray patterns during mechanical drawing using synchrotron radiation.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/mamobx/2012/mamobx.2012.45.issue-21/ma301714f/production/images/medium/ma-2012-01714f_0008.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/ma301714f'>ACS Electronic Supporting Info</A></P>
Kamal, Tahseen,Park, Soo-Young,Park, Jung-Hyun,Chang, Young-Wook 한국고분자학회 2012 Macromolecular Research Vol.20 No.7
The structural evolution of poly(ether-b-amide12) (PEBAX$^{(R)}$) elastomers was studied by using wide angle X-ray scattering (WAXS) at a synchrotron radiation source during the uniaxial stretching. The changes in the crystal structure of the nylon 12 were tracked during the stretching of the P6333 and P2533 compressed films, which represent a hard rubber and a soft elastomer, respectively. The nylon 12 chains of both samples favored the ${\gamma}$-phase in the unstrained state but their responses to the external drawing force were different. For the P6333 film containing small amounts of the soft segments, the applied force dilated the 001 crystalline lattice plane of nylon 12 which is perpendicular to its main chain and the ${\gamma}$ form was transformed into the ${\alpha}$" form when the applied force was high enough. However, for the P2533 containing large amounts of the soft segments, the lattice dimensions of the nylon 12 crystals did not change with the external drawing force and the transient ${\alpha}$" form was not observed. These results might suggest that the transfer of the external force to the crystal was difficult for P2533 due to the chain relaxation of the soft segments.
Kamal, Tahseen,Park, Soo-young The Royal Society of Chemistry 2015 New Journal of Chemistry Vol.39 No.1
<P>A series of copolymers containing 4-cyanobiphenyl-4′-oxyundecylacrylate (LC11) as the hydrophobic liquid crystal (LC) unit and acrylamide (AAm) as the hydrophilic unit were synthesized by free radical polymerization. <SUP>1</SUP>H NMR spectra of the copolymers confirmed the successful copolymerization. The PAAm-<I>co</I>-PLC11 (75/25), (80/20), and (85/15) copolymers showed swelling behavior in water and formed hydrogels because of the hydrophilic AAm units in the copolymer chains while the LC11 units formed cross-linking junctions by organizing into microstructures. The organization of the LC11 units into microstructures was revealed by a polarized optical microscopy (POM) study of the copolymer hydrogels. The copolymers with LC11 ratios higher than 25 mol% were too hydrophobic to swell in water to form hydrogels. This might be because of the molecular weight of the LC11 units, which is several fold higher than AAm. The copolymers with less than 15 mol% LC11 were so hydrophilic that water dissolved them. The POM and wide angle X-ray scattering (WAXS) studies of the copolymer fiber revealed that the LC11 units were aligned with the mesogens' direction, which is perpendicular to the fiber axis.</P> <P>Graphic Abstract</P><P>The synthesis and characterization of a copolymer containing an LC unit and a hydrophilic unit are reported. The copolymer forms hydrogel in water with the LC component serving as the physical crosslink. <IMG SRC='http://pubs.rsc.org/services/images/RSCpubs.ePlatform.Service.FreeContent.ImageService.svc/ImageService/image/GA?id=c4nj01685h'> </P>
Shape-Responsive Actuator from a Single Layer of a Liquid-Crystal Polymer
Kamal, Tahseen,Park, Soo-young American Chemical Society 2014 ACS APPLIED MATERIALS & INTERFACES Vol.6 No.20
<P>Actuation of various shape changes, including bending, helical twisting, and reversible hinging, has been achieved from a single-layer sheet of poly(1,4-di(4-(3-acryloyloxypropyloxy)benzoyloxy)-2-methylbenzene) [poly(RM257)]. This actuator was developed through photopolymerization of a reactive liquid-crystal (LC) monomer (RM257) mixed with 4-pentyl-4′-cyanobiphenyl (5CB, nematic LC at room temperature) in a planar polyimide-coated LC cell. The UV beam perpendicular to one side of the LC cell produced an asymmetric phase separation between the poly(RM257) network and 5CB that resulted in an asymmetric porous structure along the thickness direction when the 5CB was extracted, in which the UV-exposed surface was pore-free and compact while the opposite surface was highly porous. As a result of this structure, the dry and curled poly(RM257) film exhibits actuation behavior when placed in acetone because of a difference in swelling between the two morphologically different sides, the film UV-exposed and nonexposed sides. The actuation of a three-dimensional tetrahedron (pyramidal) structure is also demonstrated for the first time by using a simple photopatterning technique to selectively control its asymmetric morphology at specific locations.</P><P><B>Graphic Abstract</B> <IMG SRC='http://pubs.acs.org/appl/literatum/publisher/achs/journals/content/aamick/2014/aamick.2014.6.issue-20/am504910h/production/images/medium/am-2014-04910h_0008.gif'></P><P><A href='http://pubs.acs.org/doi/suppl/10.1021/am504910h'>ACS Electronic Supporting Info</A></P>