• Title, Summary, Keyword: Engineering Plastic

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Design and experiment with a plastic mulch wrapper using a hydraulic system

  • Park, Hyo Je;Lee, Sang Yoon;Park, Yong Hyun;Kim, Young Keun;Choi, Il Su;Nam, Young Jo;Kweon, Gi Young
    • Korean Journal of Agricultural Science
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    • v.47 no.1
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    • pp.43-58
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    • 2020
  • Mulching plastic is used for the purpose of maintaining soil temperature, moisture, and weed and pest prevention in agriculture. Any remaining plastic after use may contaminate the soil and damage crop growth. To solve this problem, mulching plastic wrappers have been studied and developed, but the actual use rate is quite low due to their poor performance and frequent tearing of the plastic on the field. In this study, we developed a tractor attachable mulching plastic wrapper to minimize the tearing of the mulched plastic. The developed mulching plastic wrapper consists of hydraulic motors and pumps, valves, a microcontroller, and sensors. The collecting speed of the plastic mulch was calculated considering the tractor's travel speed and the radius of the collecting drum. A proportional controller was designed to control the rotating speed of the hydraulic motor as the plastic was wound around the collection drum and the radius increased. The performance of an indoor experiment was quite promising because the difference between the collecting speed predicted by the calculation and the actual collecting speed was 2.71 rpm. Based on a field verification test, the speed difference was max. 14.28 rpm; thus, the, proportional integral derivative (PID) controller needs to be considered to control the drum speed precisely. Another issue was found when the soil covered at the edge of the plastic was hardened or the road surface was uneven, the speed control was unstable, and the plastic was torn. In future research, vibrational plows will be equipped to break-up the harden soil for collecting the plastic smoothly.

Laser Welding Parameter Variations and its Application for Plastic Adhesion

  • Park, Sung-Jin;Park, Sung-Joon;Park, Hae-Young;Park, Jae-Wook;Sim, Ji-Young;Choi, Jin-Young;Kim, Hee-Je
    • Journal of Electrical Engineering and Technology
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    • v.2 no.1
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    • pp.112-117
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    • 2007
  • a parametric investigation was conducted to evaluate the effect of the laser beam for plastic adhesion. To determine the best condition for plastic adhesion, the $CO_2$(wavelength $10.6{\mu}m$) and nd:yag(wavelength $10.6{\mu}m$) laser were experimented with. From the experiment results obtained, the nd:yag laser was revealed to be the most suitable for plastic adhesion. In this study, three adhesion parameters such as input power level, working time of laser beam and pps(pulse per second) were systematically adjusted for suitable adhesion. From these experiments, it was observed that the target plastic melted and was evaporated by the nd:yag laser. Furthermore, the relationships between adhesive surface by laser beam and above three parameters were discovered.

3-Dimensional Elastic-Plastic Contact Analysis Considering Subsurface Plastic Strain in a Half-Space (반무한체 표면아래의 소성변형을 고려한 3차원 탄소성 접촉해석)

  • Cho, Yong-Joo;Moon, Kil-Hwan;Lee, Sang-Don
    • Tribology and Lubricants
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    • v.24 no.2
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    • pp.90-95
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    • 2008
  • An elastic-plastic contact analysis is developed using a semi-analytical method. The elastic contact is solved within a Hertz theorem. The reciprocal theorem with initial strains is then introduced, to express the surface geometry as a function of contact stress and plastic strains. The irreversible nature of plasticity leads to an incremental formulation of the elastic-plastic contact problem, and an algorithm to solve this problem is set up. Closed form expression, which give residual stresses and surface displacements from plastic strains, are obtained by integration of the reciprocal theorem. The distribution of contact stress, residual stress and plastic strain are obtained by the changed surface geometry.

New Structure of Rigid Spacers for Tight Bonding of Two Plastic Substrates in Plastic LCD

  • Choi, Hong;Jang, Se-Jin;Bae, Ji-Hong;Choi, Yoon-Seuk;Kim, Sang-Il;Shin, Sung-Sik;Kim, Jae-Hoon
    • 한국정보디스플레이학회:학술대회논문집
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    • pp.352-355
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    • 2007
  • We have developed tight bonding of plastic LCD with new rigid spacer. For tight bonding of two plastic substrates, we designed structures to collect UV or thermal epoxy placed on the top of rigid spacer spontaneously by capillary effect. We confirmed that tight bonded plastic LCD has a good adhesion without induced defects and a high mechanical stability against the various external deformations. This method can be applicable to the fabrication of large plastic LCDs using stamping process.

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Dynamic response of elasto-plastic planar arches

  • Lee, S.L.;Swaddiwudhipong, S.;Alwis, W.A.M.
    • Structural Engineering and Mechanics
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    • v.4 no.1
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    • pp.9-23
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    • 1996
  • The behaviour of elasto-plastic planar arches subjected to dynamic loads in presented. The governing equations are formulated through the dynamic equations and compatibility conditions. The latter is established by applying the generalized conjugate segment analogy. Bending moments at the nodes and axial forces in the members are considered as primary variables in the elastic regime. They are supplemented by the rotations at the nodes and dislocations in the elements when plastic hinges occur. Newmark-${\beta}$ method is adopted in the time marching process. The interaction diagram of each element is treated as the yield surface for the element and the associated flow rule is enforced as plastic flow occurs. The method provides good prediction of dynamic response of elasto-plastic arches while requiring small core storage and short computer time.

A simple approach to the elasto-plastic coupling analyses of circular tunnels in confining pressure-dependent strain-softening rock masses

  • Zhang, Qiang;Li, Cheng;Guo, Qiang;Min, Ming;Wang, Yanning;Jiang, Binsong
    • Geosystem Engineering
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    • v.20 no.5
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    • pp.261-270
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    • 2017
  • The conventional strain-softening behaviors which assume the strength parameters as the functions of the plastic strain have been studied using various methods. However, rock-like materials have also been found to manifest pressure-dependent behavior for both elastic and plastic rock masses. The realization of the radial stress was found to be continuous, and gradually increased from supporting stress to in situ stress for the circular openings under hydrostatic pressure. The radial stress was spaced as numbers of sections, and each annulus was considered as an ideal plastic rock mass. The close-formed analytical solutions of each annulus can be easily obtained. Therefore, using the displacement continuum and stress boundary conditions, the dimensionless radius corresponding to the spaced radius could be derived. The radial stress and plastic shear strain at the inner radius of the outer adjacent annulus were employed to describe the material property evolution law. Then, the radii could be recursively obtained. Finally, for the conventional strain-softening rock masses, the pressure-dependent elastic rock and elasto-plastic coupling strain-softening rock masses were employed to validate the proposed approach. In this study, having completed the above steps, it was concluded that the results were in accordance with the numerical methods.

Degradation Characteristics of Strength and Stiffness due to Soils (흙의 종류에 따른 강도와 강성저하 특성)

  • Song, Byung-Woong;Kim, Hong-Taek;Yasuhara, Kazuya;Murakami, Satosh;Park, Inn-Joon
    • Proceedings of the Korean Geotechical Society Conference
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    • pp.253-260
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    • 2004
  • Many scholars and researchers has been studied for many kinds of soil characteristics, but a lot of part are still unsolved. Cyclic load-induced decreasing characteristics of strength and stiffness of soils are also well not known among them. To know that, the characteristics of five kinds of soils; clay, plastic and non-plastic silt, sand, and a weathered soil are compared with dividing two types as plastic or non-plastic soils through direct simple shear(DSS) test. From the results of DSS test, it is known that decreasing characteristics of strength and stiffness are different according to soil types. The strength of plastic and non-plastic soils increases with increment of plasticity index and decrement of volume decrease potential, respectively. And the decreasing stiffness of plastic and non-plastic soils increases with decrement of plasticity index and increment of volume decrease potential, respectively.

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Improved 3D Printing Plastic Scintillator Fabrication

  • Son, Jaebum;Kim, Dong Geon;Lee, Sangmin;Park, Junesic;Kim, Yonghyun;Schaarschmidt, Thomas;Kim, Yong Kyun
    • Journal of the Korean Physical Society
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    • v.73 no.7
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    • pp.887-892
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    • 2018
  • 3D printing techniques can be widely used for various applications owing to their fast speed, convenience, and customized shape output. The 3D printing technique is applicable to plastic scintillator fabrication which typically uses polymerization. Currently, research on application of the 3D printing technique based on photopolymerization to plastic scintillator fabrication is being pursued. However, performance of the photopolymerized scintillators reported till now is lower than that of commercial plastic scintillators (~ 30%). We have carried out research on performance improvement of the scintillator fabricated by the photopolymerization, for radiation dose measurement. Photopolymer resin with novel recipe based on acrylic monomer and naphthalene was used to fabricate the scintillator instead of the photopolymer resin based on styrene, which is typically used as the monomer for commercial scintillator. 3D printer with digital light processing was used for the photopolymerization of the photopolymer resin. As a result, light output performance of the fabricated plastic scintillator was about 67% compared with that of the commercial plastic scintillator, BC-408. The performance of the scintillator fabricated by the photopolymerization was thus improved to more than two times that obtained by previous researchers. This is sufficient to be applied to the radiation dose measurement with high dose rates such as radiation therapy. It also demonstrated the applicability of the 3D printing technique in scintillator fabrication.

On elastic and plastic length scales in strain gradient plasticity

  • Liu, Jinxing;Wang, Wen;Zhao, Ziyu;Soh, Ai Kah
    • Structural Engineering and Mechanics
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    • v.61 no.2
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    • pp.275-282
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    • 2017
  • The Fleck-Hutchinson theory on strain gradient plasticity (SGP), proposed in Adv. Appl Mech 33 (1997) 295, has recently been reformulated by adopting the strategy of decomposing the second order strain presented by Lam et al. in J Mech Pays Solids 51 (2003) 1477. The newly built SGP satisfies the non negativity of plastic dissipation, which is still an outstanding issue in other SGP theories. Furthermore, it explicitly shows how elastic strain gradients and corresponding elastic characteristic length scales come into play in general elastic-plastic loading histories. In this study, the relation between elastic length scales and plastic length scales is investigated by taking wire torsion as an example. It is concluded that the size effects arising when two sets of length scales are of the same order are essentially elastic instead of plastic.