• Title/Summary/Keyword: Fatigue-free

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A Comparative Study of the Fatigue Behavior of SnAgCu and SnPb Solder Joints (무연솔더(SnAgCu)와 유연솔더(SnPb)의 피로 수명 비교 연구)

  • Kim, Il-Ho;Park, Tae-Sang;Lee, Soon-Bok
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.28 no.12
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    • pp.1856-1863
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    • 2004
  • In the last 50 years, lead-contained solder materials have been the most popular interconnect materials used in the electronics industry. Recently, lead-free solders are about to replace lead-contained solders for preventing environmental pollutions. However, the reliability of lead-free solders is not yet satisfactory. Several researchers reported that lead-contained solders have a good fatigue property. The others published that the lead-free solders have a longer thermal fatigue life. In this paper, the reason for the contradictory results published on the estimation of fatigue life of lead-free solder is investigated. In the present study, fatigue behavior of 63Sn37Pb, and two types of lead-free solder joints were compared using pseudo-power cycling testing method, which provides more realistic load cycling than chamber cycling method does. Pseudo-power cycling test was performed in various temperature ranges to evaluating the shear strain effect. A nonlinear finite element model was used to simulate the thermally induced visco-plastic deformation of solder ball joint in BGA packages. It was found that lead-free solder joints have a good fatigue property in the small temperature range condition. That condition induce small strain amplitude. However in the large temperature range condition, lead-contained solder joints have a longer fatigue life.

The Effect of Drawing and Heat Treatment on Fatigue Life and Machinability in Free Machining Steel (쾌삭강의 피로수명 및 절삭성에 미치는 인발-열처리의 영향)

  • Suh, C.H.;Kim, D.B.;Oh, S.K.;Jung, Y.C.;Park, M.K.;Kim, Y.S.
    • Transactions of Materials Processing
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    • v.19 no.2
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    • pp.95-100
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    • 2010
  • Drawing and normalizing are efficient means for controlling strength, fatigue and machinability of free machining steel. Normally strength and machinability are conflicting properties which need to be optimized. In this study, the effects of normalizing temperature and reduction of area on strength, fatigue and machinability were investigated. Fine grains were generated at lower normalizing temperature and fatigue life was increased with decreasing grain size. Matrix was work hardened and elongated with increasing reduction of area. Inclusions also were elongated and cross-sectional area of inclusions along drawing axis was decreased. The effects of work hardening and grain size on fatigue life were significant, but only work hardening affected machinability. Shape and distribution of inclusions after drawing had little effect on fatigue life and machinability.

Solder Joints Fatigue Life of BGA Package with OSP and ENIG Surface Finish (OSP와 ENIG 표면처리에 따른 BGA 패키지의 무연솔더 접합부 피로수명)

  • Oh, Chulmin;Park, Nochang;Hong, Wonsik
    • Korean Journal of Metals and Materials
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    • v.46 no.2
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    • pp.80-87
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    • 2008
  • Many researches related to the reliability of Pb-free solder joints with PCB (printed circuit board) surface finish under thermal or vibration stresses are in progress, because the electronics is operating in hash environment. Therefore, it is necessary to assess Pb-free solder joints life with PCB surface finish under thermal and mechanical stresses. We have investigated 4-points bending fatigue lifetime of Pb-free solder joints with OSP (organic solderability preservative) and ENIG (electroless nickel and immersion gold) surface finish. To predict the bending fatigue life of Sn-3.0Ag-0.5Cu solder joints, we use the test coupons mounted 192 BGA (ball grid array) package to be added the thermal stress by conducting thermal shock test, 500, 1,000, 1,500 and 2,000 cycles, respectively. An 4-point bending test is performed in force controlling mode. It is considered that as a failure when the resistance of daisy-chain circuit of test coupons reaches more than $1,000{\Omega}$. Finally, we obtained the solder joints fatigue life with OSP and ENIG surface finish using by Weibull probability distribution.

The Efficacy of Newly Designed Screw for Prevention of the Screw Breakage in Syndesmosis Fixation: Biomechanical Study (나사 파단 예방을 위해 새로 디자인한 경비 인대 결합 나사의 효용성: 생역학 연구)

  • Lee, Dong-Oh;Song, Sang-Heon
    • Journal of Korean Foot and Ankle Society
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    • v.24 no.2
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    • pp.94-97
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    • 2020
  • Purpose: Fatigue breakage of cortical screws sometimes occurs after syndesmosis fixation, regardless of the period of screw retention. This study compared the fatigue strength of a novel screw design to conventional cortical screws in the fixed state of syndesmosis. Materials and Methods: Twelve sawbone models were tested mechanically to determine the fatigue strength of three screw designs. The first group was composed of cortical screws, while the second and third groups were newly-designed screws. The second group was composed of screws with a 2.4-mm diameter thread-free portion of the mid-shank while the third group had a 2.0-mm diameter thread-free mid-shank. A 400 N load was applied repetitively to a fibula model and the number of cycles until screw failure was recorded. Four screws from each group were tested, giving a total of 12 fatigue tests. Results: The average cycles until screw failure for groups 1, 2, and 3 were 8,134, 63,186, and 2,581, respectively. The second group showed the highest fatigue strength (p=0.018). The other two screw designs showed similar fatigue strength (p=0.401). Conclusion: New screw designs with a thread-free portion in the mid-shank could reduce the occurrence of fatigue breakage after syndesmosis fixation.

Procedural steps for reliability evaluation of ultrasonically welded REBCO coated conductor lap-joints under low cycle fatigue test condition

  • Michael De Leon;Mark Angelo Diaz;Hyung-Seop Shin
    • Progress in Superconductivity and Cryogenics
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    • v.25 no.4
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    • pp.28-31
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    • 2023
  • This study presents a comprehensive procedure for the low cycle fatigue test of ultrasonically welded (UW) coated conductor (CC) lap-joints. The entire process is examined in detail, from the robust fabrication of the UW REBCO CC joints to the reliability testing under a low number of repeated cycle fatigue conditions. A continuous Ic measurement system enables real-time monitoring of Ic variations throughout the fatigue tests. The study aims to provide a step-by-step procedure that involves joint fabrication, electromechanical property (EMP) tests under uniaxial tension for stress level determination, and subsequent low-cycle fatigue tests. The joints are fabricated using a hybrid method that combines UW with adding In-Sn soldering, achieving a flux-free hybrid welding approach (UW-HW flux-free). The selected conditions for the low cycle fatigue tests include a stress ratio of R=0.1 and a frequency of 0.02 Hz. The results reveal some insights into the fatigue behavior, irreversible changes, and cumulative damage in the CC joints.

Free Spanning of Offshore Pipelines by DNV

  • CHOI HAN SUK
    • Journal of Ocean Engineering and Technology
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    • v.19 no.2 s.63
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    • pp.47-52
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    • 2005
  • This paper introduces a procedure for free span and fatigue analysis of offshore pipelines per DNV-RP-F105, 2002. The new method includes the axial force and deflection load in pipelines. The screening criteria were established to calculate the allowable span lengths in the new design codes. The screening criteria allows a certain amount of vortex-induced vibration due to wave and current loading. However, the induced pipe stresses are very small and usually below the limit stresess of typical S-N curves. In contrast, the conventional criteria did not allow any vortex-induced vibration in the free span of pipelines. Thus, the screening criteria yields reduced allowable span lengths. A simplified procedure was established to calculate the fatigue damage due to long-term current distribution. The long-term current statistics was assumed with a 3-parameter Weibull distribution. The fatigue damage was estimated for the span lengths obtained from the screening criteria for various conditions. Sample calculations show the effect of axial force for various boundary conditions. Comparisons with conventional criteria are included.

Thermal Fatigue Life Prediction of ${\mu}BGA$ Solder Joint Using Sn-37mass%Pb Solder and Sn-3.5mass%Ag Lead-free Solder (Sn-37mass%Pb 솔더 및 Sn-3.5mass%Ag 무연솔더를 이용한 ${\mu}BGA$ 솔더접합부의 열피로수명 예측)

  • 신영의;이준환;하범용;정승부;정재필
    • Journal of Welding and Joining
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    • v.19 no.4
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    • pp.406-412
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    • 2001
  • This study is focussed on the numerical prediction of the thermal fatigue life of a ${\mu}BGA$(Micro Ball Grid Array) solder joint. Numerical method is used to perform three-dimensional finite element analysis for Sn-37mass%Pb. Sn-3.5mass%Ag solder alloys during the given thermal cycling. Strain values, along with the result of mechanical fatigue tests for solder alloys were then used to predict the solder joint fatigue life using the Coffin-Manson equation. In this study, a practical correlation for the prediction of the thermal fatigue life is suggested by using the dimensionless variable $\gamma$. As a result. it could be found that Sn-3.5mass%Ag has longer fatigue life than Sn-37mass%Pb in low cycle fatigue. In addition. the result with ${\gamm}ashow$a good agreement with the FEA results.

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Free Spanning of Offshore Pipelines by DNV 2002 (DNV 2002에 의한 해저관로의 자유경간해석)

  • Choi, Han-Suk;Joo, Joo-Kyung
    • Proceedings of the Korea Committee for Ocean Resources and Engineering Conference
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    • 2002.10a
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    • pp.29-33
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    • 2002
  • A procedure of free span and fatigue analysis of offshore pipelines was made per DNV-RP-F105, 2002. The new method includes the axial force and deflection load in pipelines. The screening criteria were used to calculate the allowable span lengths. The screening criteria allow small amplitudes of vortex-induced vibration due to wave and current loading. However, the induced pipe stress is very small and usually below the limit stress of a typical S-N curve. A simplified method was established to calculate the fatigue damage due to long-term current distribution. The long-term current statistics was assumed with a 3-parameter Weibull distribution. The fatigue damage was estimated for the span lengths obtained from the screening criteria for various conditions. Sample calculations show the effect of axial force for various boundary conditions.

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Glasses-free Interactive 3D Display: The Effects of Viewing Distance, Orientation and Manual Interaction on Visual Fatigue (무안경식 Interactive 3D Display: 시청거리, 시청방위, 협응동작이 시각피로에 미치는 영향)

  • Kim, Duk-Joong;Li, Hyung-Chul O.;Kim, Shin-Woo
    • Journal of Broadcast Engineering
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    • v.17 no.4
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    • pp.572-583
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    • 2012
  • In this study, we investigated visual fatigue in i3D system and basic factors that contribute to visual fatigue in the system. i3D is a type of glasses-free display which supports elementary manual interaction of users with the display. In Experiment 1, we performed open-ended survey of visual fatigue and collected responses from observers which then were used as survey questions for visual fatigue. The questions were validated by factor analysis from which we derived fatigue measurement scale. In Experiment 2, we measured visual fatigue in various conditions using survey questions obtained from Experiment 1. Using manual interaction (present/absent), viewing distance(1/2/4m), and viewing orientation($0/28/56^{\circ}$) as three factors in within-subject design, we measured visual fatigue in each condition. The results indicated that visual fatigue deceases with farther viewing distance, but viewing orientation and manual interaction does not influence visual fatigue. Although fatigue unexpectedly decreased in an extreme viewing condition (e.g., distance 1m, orientation $56^{\circ}$), the results were obtained because of technical limitation of glasses-free 3D display. General discussion provides discussion on limits of the current study and suggestions for future research.

Effect of Prolonged Running-induced Fatigue on Free-torque Components

  • Ryu, Ji-Seon
    • Korean Journal of Applied Biomechanics
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    • v.26 no.1
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    • pp.31-37
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    • 2016
  • Purpose: The purpose of this study was to investigate the differences in FT (free-torque) components between non-fatigue and fatigue conditions induced by prolonged running. Methods: Fifteen healthy runners with no previous lower-extremity fractures ($22.0{\pm}2.1$ years of age) participated in this study. Ground reaction force data were collected for the right-stance phase for 10 strides of 5 and 125-min running periods at 1,000 Hz using an instrumented force platform (instrumented dual-belt treadmills, Bertec, USA) while the subjects ran on it. The running speed was set according to the preferences of the subjects, which were determined before the experiment. FT variables were calculated from the components of the moment and force output from the force platform. A repeated-measures one-way ANOVA was used to test for significant differences between the two conditions. The alpha level for all the statistical tests was 0.05. Results: The absolute FT at the peak braking force was significantly greater after 5 mins of running than after 125 mins of running-which was regarded as a fatigued state-but there were no significant differences in the absolute peak FT or impulse between the conditions. Conclusion: The FT variables in the fatigue condition during prolonged running hardly affect the tibial stress syndrome.