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  • Title/Summary/Keyword: Drop-in Test

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Mechanical Modeling of Pen Drop Test for Protection of Ultra-Thin Glass Layer (초박형 유리층 보호를 위한 펜 낙하 시험의 기계적 모델링)

  • Oh, Eun Sung;Oh, Seung Jin;Lee, Sun-Woo;Jeon, Seung-Min;Kim, Taek-Soo
    • Journal of the Microelectronics and Packaging Society
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    • v.29 no.3
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    • pp.49-53
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    • 2022
  • Ultra-thin glass (UTG) has been widely used in foldable display as a cover window for the protection of display and has a great potential for rollable display and various flexible electronics. The foldable display is under impact loading by bending and touch pen and exposed to other external impact loads such as drop while people are using it. These external impact loads can cause cracks or fracture to UTG because it is very thin under 100 ㎛ as well as brittle. Cracking and fracture lead to severe reliability problems for foldable smartphone. Thus, this study constructs finite element analysis (FEA) model for the pen drop test which can measure the impact resistance of UTG and conducts mechanical modeling to improve the reliability of UTG under impact loading. When a protective layer is placed to an upper layer or lower layer of UTG layer, stress mechanism which is applied to the UTG layer by pen drop is analyzed and an optimized structure is suggested for reliability improvement of UTG layer. Furthermore, maximum principal stress values applied at the UTG layer are analyzed according to pen drop height to obtain maximum pen drop height based on the strength of UTG.

The Analytic and Numerical Solutions of the 112-layer and 212-layer Models to the Strong Offshore Winds.

  • Lee, Hyong-Sun
    • Journal of the korean society of oceanography
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    • v.31 no.2
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    • pp.75-88
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    • 1996
  • The analytic and numerical solution of the 112-layer and 212-layer models are derived. The large coastal-sea level drop and the fast westward speed of the anticyclonic gyre due to strong offshore winds using two ocean models are investigated. The models are forced by wind stress fields similar in structure to the intense mountain-pass jets(20 dyne/cm2) that appear in the Gulfs of Tehuantepec and Papagayo in the Central America for periods of 37 days. Analytic and numerical solutions compare favorably with observations, the large sea-level drop (30 cm) at the coast and the fast westward propagation speeds (13 km/day) of the gyres. The coastal sea-level drop is enhanced by several factors: horizontal mixing, enhanced forcing, coastal geometry, and the existence of a second active layer in the 212-layer model. Horizontal mixing enhances the sea-level drop because the coastal boundary layer is actually narrower with mixing. The forcing τ/h is enhanced near the coast where h is thin. Especially, in analytic solutions to the 212-layer model the presence of two baroclinic modes increases the sea-level drop to some degree. Of theses factors the strengthened forcing τ/h has the largest effect on the magnitude of the drop, and when all of them are included the resulting maximum drop is -30.0 cm, close to observed values. To investigate the processes that influence the propagation speeds of anticyclonic gyre, several test wind-forced calculations were carried out. Solutions to dynamically simpler versions of the 112-layer model show that the speed is increased both by β-induced self-advection and by larger h at the center ofthe gyres. Solutions to the 212-layer model indicate that the lower-layer flow field advects the gyre westward and southward, significantly increasing their propagation speed. The Papagayo gyre propagates westward at a speed of 12.8 km/day, close to observed speeds.

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Numerical Study of Drop/impact test and Shock/impact Survivability Test for ELT(Emergency Locator Transmitter) Operations (ELT(Emergency Locator Transmitter) 운용을 위한 낙하 충격 및 추락생존성 시험에 대한 수치 해석적 연구)

  • Jung, Do-Hee;Baek, Jong-Jin
    • Journal of the Korean Society for Aeronautical & Space Sciences
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    • v.36 no.12
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    • pp.1229-1235
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    • 2008
  • ELT(emergency locator transmitter) has assisted in the rescue of thousands of lives in distress. Aviators, mariners and land users being equipped with distress beacons are capable of transmitting distress signals to the satellites in emergency situations anywhere in the world. In this paper, Drop/Impact simulation was performed for ELT Body-case. FE model for Body-case was constructed with MSC/Dytran and refined using the Karas example simulation for Body-case prototype. Shock/impact survivability analysis was performed for ELT operations. FE model constructed with MSC/Nastran. Transient response analysis for refined ELT model was perfomed for ELT under impact shock loading condition.

Difference of Potential Range Formed at the Anode Between Water Drop Test and Temperature Humidity Bias Test to Evaluate Electrochemical Migration of Solders for Printed Circuit Board

  • Young Ran Yoo;Young Sik Kim
    • Corrosion Science and Technology
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    • v.22 no.3
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    • pp.153-163
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    • 2023
  • Two types of accelerated tests, Water Drop Test (WDT) and Temperature-Humidity-Bias Test (THBT), can be used to evaluate the susceptibility to electrochemical migration (ECM). In the WDT, liquid water is directly applied to a specimen, typically a patterned conductor like a printed circuit board. Time to failure in the WDT typically ranges from several seconds to several minutes. On the other hand, the THBT is conducted under elevated temperature and humidity conditions, allowing for assessment of design and life cycle factors on ECM. THBT is widely recognized as a more suitable method for reliability testing than WDT. In both test methods, localized corrosion can be observed on the anode. Composition of dendrites formed during the WDT is similar to that formed during THBT. However, there is a lack of correlation between the time to failure obtained from WDT and that obtained from THBT. In this study, we investigated the relationship between electrochemical parameters and time to failure obtained from both WDT and THBT. Differences in time to failure can be attributed to actual anode potential obtained in the two tests.

The Effects of UBM and SnAgCu Solder on Drop Impact Reliability of Wafer Level Package

  • Kim, Hyun-Ho;Kim, Do-Hyung;Kim, Jong-Bin;Kim, Hee-Jin;Ahn, Jae-Ung;Kang, In-Soo;Lee, Jun-Kyu;Ahn, Hyo-Sok;Kim, Sung-Dong
    • Journal of the Microelectronics and Packaging Society
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    • v.17 no.3
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    • pp.65-69
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    • 2010
  • In this study, we investigated the effects of UBM(Under Bump Metallization) and solder composition on the drop impact reliability of wafer level packaging. Fan-in type WLP chips were prepared with different solder ball composition (Sn3.0Ag0.5Cu, and Sn1.0Ag0.5Cu) and UBM (Cu 10 μm, Cu 5 μm\Ni 3 μm). Drop test was performed up to 200 cycles with 1500G acceleration according to JESD22-B111. Cu\Ni UBM showed better drop performance than Cu UBM, which could be attributed to suppression of IMC formation by Ni diffusion barrier. SAC105 was slightly better than SAC305 in terms of MTTF. Drop failure occurred at board side for Cu UBM and chip side for Cu\Ni UBM, independent of solder composition. Corner and center chip position on the board were found to have the shortest drop lifetime due to stress waves generated from impact.

Compatibility Test of the Capsule with Cone Shape Bottom Guide Structures to the HANARO Reactor (원추형 하단부 구조를 갖는 캡슐의 하나로와의 양립성시험)

  • Choi, M.H.;Cho, M.S.;Choo, K.N.;Park, S.J.;Kim, B.G.;Kang, Y.H.
    • Proceedings of the KSME Conference
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    • 2004.04a
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    • pp.444-449
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    • 2004
  • The design modification of bottom guide structures of the instrumented capsule, which is used for the irradiation test in the HANARO reactor, was required because of the trouble of the bottom guide arm's pin during irradiation. The previous structure with 3-pin arms was changed into the cone shape of one body. The specimens of the bottom end cap ring with three different sizes (Φ68/70/72mm) were designed and manufactured. The out-pile tests for the capsule with previous and new three bottom guide structures were performed in the one-channel flow test facilities. In order to evaluate the compatibility with HANARO and the structural integrity of the capsule, a loading/unloading, a pressure drop, a thermal performance, a vibration, and an endurance test were conducted. From out-pile test results, the capsule with the cone shape bottom guide structures was found to be more stable than the previous structure and the optimized size of the bottom guide structure selected was 70mm in diameter. It is expected that the new bottom guide structures will be applicable to all material and special capsules which will be designed and manufactured for the irradiation tests in the future.

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Impact Bending Test Simulations of FH32 High-strength Steel for Arctic Marine Structures

  • Choung, Joonmo;Han, Donghwa;Noh, Myung-Hyun;Lee, Jae-Yik;Shim, Sanghoon
    • Journal of Advanced Research in Ocean Engineering
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    • v.2 no.1
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    • pp.28-39
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    • 2016
  • This paper provides theoretical and experimental results to verify the crashworthiness of FH32 high-strength steel for arctic marine structures against ice impact. Assuming that side-shell structures of the Korean arctic research vessel, ARAON, with ice-notation PL10, collide with sheet ice, one-third-scale test specimens with a single transverse frame are manufactured. Impact-bending tests were conducted using a rigid steel striker that mimics sheet ice. Drop height was calculated by considering the speed at which sheet ice is rammed. Prior to impact-bending tests, tensile coupon tests were conducted at various temperatures. The impact-bending tests were carried out using test specimens fully fixed to the inside bottom frame of a cold chamber. The drop-weight velocity and test specimen deformation speed were measured using a high-speed camera and digital image correlation analysis (DICA). Numerical simulations were carried out under the same conditions as the impact-bending tests. The simulation results were in agreement with the test results, and strain rate was a key factor for the accuracy of numerical simulations.

Effect of Sports Taping on Impact Forces and Muscle Tuning during Drop Landing (드롭 착지 시 스포츠 테이핑이 하지의 충격력과 근육 조율에 미치는 영향)

  • Kang, Nyeon-Ju;Chae, Woen-Sik
    • Korean Journal of Applied Biomechanics
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    • v.20 no.2
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    • pp.175-182
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    • 2010
  • The purpose of this study was to evaluate the biomechanical effect of sports taping on the lower limb during drop landing. Twelve male university students who have no musculoskeletal disorder were recruited as the subjects. Principal strain, median frequency, vertical GRF, loading rate, angular velocity and resultant joint moment were determined for each trial. For each dependent variable, paired t-test was performed to test if significant difference existed between taped and untaped conditions(p<.05). The results showed that principal strain of the thigh and the shank in taping group were significantly less than those found in control group. These indicated that sports taping may prevent excessive mechanical strain caused by impact force during the deceleration phase. Flexion(-)-extension(+) and varus(-)-valgus(+) resultant joint moment of the knee joint in taping group were greater than corresponding value for control group. It seems that extensor muscle of the knee joint were not only supported by sports taping during knee flexion but also sports taping is effective for minimizing the possibility of injury.

Analysis of Lower body on Korean Young Women and the Effect of the Lower body Type on the Shape of Flare Skirt (II) (한국 미혼 여성의 하반신체형 분석과 체형변인이 플레어스커트 입체성능에 미치는 영향(II))

  • 조정미
    • Journal of the Korean Home Economics Association
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    • v.30 no.3
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    • pp.15-32
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    • 1992
  • The purpose of this study was to detect the effect of the lower body type on the shape of flare skirts. The subjects for the wearing test were 50 female students, who were controlled in their hip and waist shapes. The skirts used for wearing test were six types(three flar angles × two fabric types). The effect of lower body type on the shape of flare skirts was determind by the hemline trace method and the silhouette photography. The data were then analyzed by the repeated measures of analysis of variance and the SNK multiple range test. The results obtained from this study were as follows : 1) When a flare skirt made with larger flare angle and better drapable fabric was worn, the numeric of the nodes increased as the drop value(hip - waist) increased. When a flare skirt made with smaller flare angle was worn, the width of horizontal sectio of hemline increased as the drop value increased. The hemline uneveness decreased on the sides and back as the drop value increased. When a flare skirt made with worse drapable fabric was worn, the sides angle of the flarskirt increased as the drop value increased. 2) When a flare skirt made with larger flare angle was worn, the numeric of nodes increased as the ratio of dropped hip increased. The wave-height increased and the back variation ratio of wave-height was higher than the front variation ratio of wave-height as the ratio of dropped hip increased. The hemiline uneveness decreased on the back as the ratio of dropped hip increased. When a flare skirt made with larger flare angle was worn, the sides angle of the flare skirt increased as the ratio of dropped hip increased.

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Determination of Consolidation Characteristics in Fine Soils Evaluated by Piezocone Tests (콘 관입시험을 이용한 연약지반 압밀특성 평가)

  • Lim, Beyong-Seock
    • Proceedings of the Korean Geotechical Society Conference
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    • 2000.02a
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    • pp.42-58
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    • 2000
  • 본 연구의 목적은 연약지반의 압밀계수 측정에 있어 Piezocone 관입시험을 이용할 때 관입시험자체의 정확성과 시험결과들에 미치는 여러 가지 지반공학적 영향요소들을 고려하려는데 있다. 본 연구의 연구실험방법으로는, Piezocone 관입을 위한 연약모형지반 조성을 위하여 초대형 Slurry Consolidometer에 Free Stress 상태의 Slurry를 45일간 압밀시킨 후 Automatic Computer Control Calibration Chamber (LSU/CALCHAS; Louisiana State University Calibration Chamber System)에 옮긴후 다시한번 압밀시키는 Two-Stage Consolidation Method를 사용하였다 동시에 연약모형지반내에 8개의 Piezometer를 설치하여 Piezocone 관입시 유발되는 지반 내에서의 과잉간극수압의 변환을 측정하였다. 총 25개의 Piezocone 시험중 4개는 Standard 10cm2 Piezocone이고, 나머지 21개는 Miniature Piezocone이 사용되었다. 모형지반은 여러 가지 Boundary Condition들과 Stress Condition 그리고 Stress History등을 고려하여 조성되었다. 또한 Dissipation Test직후의 압밀특성을 확인하기 위하여 0.01초당 한 개이상의 실측점을 측정할 수 있는 Digital-Oscilloscope를 이용하였다. 특히 Dissipation Test, 즉시 Piezocone의 Filter Element에 잡히지 않는 과잉간극수압의 Initial Drop 존재에 관한 기존의 추측을 실제 실험치로 확인할 수 있었다.

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