• Title/Summary/Keyword: Four-Point Bending Test

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Experimental study of anisotropic behavior of PU foam used in sandwich panels

  • Chuda-Kowalska, Monika;Garstecki, Andrzej
    • Steel and Composite Structures
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    • v.20 no.1
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    • pp.43-56
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    • 2016
  • Polyurethane foam with low density used in sandwich panels is examined in the paper. A series of experiments was carried out to identify mechanical parameters of the foam. Various experimental methods were used for determining the shear modulus, namely a four and three point bending tests (the most common in engineering practice), a double-lap shear test and a torsion test. The behavior of PU in axial compression and tension was also studied. The experiments revealed pronounced anisotropy of the PU foam. An orthotropic model is proposed. Limitations of application of isotropic model of PU in engineering practice is also discussed.

Thermal and Mechanical Properties of Ceramic Coated Al Bus Bar (세라믹 코팅 Al 부스바의 열적·기계적 특성)

  • Kwag, Dong-Soon;Baek, Seung-Myeong;Kwak, Min Hwan
    • The Transactions of The Korean Institute of Electrical Engineers
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    • v.66 no.11
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    • pp.1651-1656
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    • 2017
  • This paper deals with the thermal and mechanical properties of ceramic coating material for bus bars. A ceramic coated samples were prepared for the mechanical properties test. There are two types of samples. One is a square shape and the other is a busbar shape. Each sample was deteriorated for 30 days to compare the thermal and mechanical properties with the non-degraded samples. Two thermal properties tests are TGA and flammability tests, and four mechanical properties tests are drop impact test, cross cut, tensile test, and bend test. The ceramic coating material was never damaged by impact and did not separate from aluminum in the cross cut test. In the tensile test, the breakage of the insulating material did not occur until aluminum fractured, and the breakage of the insulating material did not occur until the maximum load in the bending test. The decomposition temperature (melting point) of the ceramic coating material was higher than that of other epoxy insulators. This ceramic coating material is nonflammable and it has excellent fire stability.

Creep Behavior of Plastics Used in Automobile Instrument Panels (자동차 인스트루먼트 패널에 사용되는 플라스틱의 크리프 거동)

  • Kim, Young-Sam;Jeon, Chi-Hoon;Tumur-Ochir, Erdenebat;Yum, Young-Jin
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.35 no.12
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    • pp.1549-1556
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    • 2011
  • Tensile and creep tests were performed at various temperatures to investigate the mechanical properties of plastics used in automotive instrument panels. Mechanical properties such as Young's modulus and Poisson's ratios changed markedly with the test temperature. Three-point bending creep tests were performed for three kinds of plastics under four loading conditions. Coefficients in the time-hardening power law creep equation were obtained from the experiment, and the creep behavior was represented by a simple expression. The results of finite element creep analysis showed good agreement with the experimental results, while the difference between the numerical and experimental results increased with the load.

Effect of Post-Annealing Conditions on Interfacial Adhesion Energy of Cu-Cu Bonding for 3-D IC Integration (3차원 소자 집적을 위한 Cu-Cu 접합의 계면접착에너지에 미치는 후속 열처리의 영향)

  • Jang, Eun-Jung;Pfeiffer, Sarah;Kim, Bi-Oh;Mtthias, Thorsten;Hyun, Seung-Min;Lee, Hak-Joo;Park, Young-Bae
    • Korean Journal of Materials Research
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    • v.18 no.4
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    • pp.204-210
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    • 2008
  • $1.5\;{\mu}m$-thick copper films deposited on silicon wafers were successfully bonded at $415^{\circ}C$/25 kN for 40 minutes in a thermo-compression bonding method that did not involve a pre-cleaning or pre-annealing process. The original copper bonding interface disappeared and showed a homogeneous microstructure with few voids at the original bonding interface. Quantitative interfacial adhesion energies were greater than $10.4\;J/m^2$ as measured via a four-point bending test. Post-bonding annealing at a temperature that was less than $300^{\circ}C$ had only a slight effect on the bonding energy, whereas an oxygen environment significantly deteriorated the bonding energy over $400^{\circ}C$. This was most likely due to the fast growth of brittle interfacial oxides. Therefore, the annealing environment and temperature conditions greatly affect the interfacial bonding energy and reliability in Cu-Cu bonded wafer stacks.

Characteristics of Flexural Behaviors for Marine Concrete Members Using High-Durable Materials (고내구성 재료를 사용한 해양 콘크리트 부재의 휨 거동 특성)

  • Yang, Eun-Ik;Kim, Myung-Yu;Park, Hae-Geun;Lee, Dong-Gun
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.12 no.6
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    • pp.249-256
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    • 2008
  • The durability of marine concrete structure is severely degraded by corrosion due to penetration and diffusion of chloride. So, many researches have been performed to improve the durability in marine concrete structure. In this study, the concrete members mixed with the mineral admixtures(SF and BFS), the epoxy-coated steel, and corrosion inhibitors are prepared, and four-point bending test of specimens are performed to investigate the flexural behaviors and the applicability for marine concrete structure. From the test results, the mineral admixtures and inhibitors are useful for safety against the initial cracking and the bending resistance in specimens. When the durable material is used in specimen, the tensile stress of reinforcing rod was less variable in same bending span length, and the durable member showed a stable behavior. And it is evaluated that the crack spacing is not larger in specimen used the durable material.

Effets of Steel Fiber Contents on Flexural Creep Behavior of High-Strength Concrete (강섬유 혼입률에 따른 고강도 콘크리트의 휨 크리프 특성)

  • Lim, Seong-Hoon;Kim, Dong-Hwi;Yun, Hyun-Do
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.24 no.2
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    • pp.111-118
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    • 2020
  • In this paper, the flexural creep behavior of hooked-end steel fiber reinforced high-strength concrete was evaluated to investigate the steel fiber content influence on long-term behavior of flexural members. An experimental program consisted of nine prismatic beam specimens with dimensions of 150 × 150 × 600mm reinforced with different contents of steel fiber (0, 0.75 and 1.5% at the volume fraction). To introduce flexural creep loading to notched prismatic beam specimens, a four-point bending test setup was used. The sustained load with 40% of the flexural strength was applied by means of a lever system and controlled by a load cell for 90 days. During sustained loading, crack mouth opening displacement (CMOD) was monitored. Conventional flexural test after creep tests were carried out to evaluate the residual capacity of each specimen. Test results showed that steel fiber content has a significant effect on the flexural creep behavior of high-strength concrete and long-term flexural load with 40% of flexural strength doesn't generate negative effects on the residual capacity of steel fiber reinforced high-strength concrete.

Facture Prediction in SiC Fiber Reinforced $Si_3N_4$ Matrix Composites from Electrical Resistivity Measurements (전기저항측정에 의한 SiC섬유강화 $Si_3N_4$기 복합재료의 파괴예측)

  • Sin, Sun-Gi
    • Korean Journal of Materials Research
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    • v.10 no.5
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    • pp.364-368
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    • 2000
  • SiC fiber reinforced $Si_3N_4$ matrix composites combined with electrical conductive phases of carbon fiber and WC powder fabricated by hot pressing at 1773K. The ability to predict fracture in the ceramic matrix composites was evaluated by measuring simultaneous load-deflection and electrical resistanc difference-deflection curves in four point bending tests. The changes in electrical resistance differences closely corresponded to the fracture behavior of the composites. Different electrical conductive phases are suited to predicting different stages and rates of fracture. These obsevations how that it is possible to perform "in situ" fracture detection in ceramic composites.

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Development of Material Deformation Measurement System using Machine Vision (머신 비전을 활용한 재료 변형 측정 기술 개발)

  • E. B. Mok;W. J. Chung;C. W. Lee
    • Transactions of Materials Processing
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    • v.32 no.1
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    • pp.20-27
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    • 2023
  • In this study, the deformation of materials was measured using the video and tracking API of OpenCV. Circular markers attached to the material were selected the region of interests (ROIs). The position of the marker was measured from the area center of the circular marker. The position and displacement of the center point was measured along the image frames. For the verification, tensile tests were conducted. In the tensile test, four circular markers were attached along the longitudinal and transverse directions. The strain was calculated using the distance between markers both in the longitudinal and transverse direction. As a result, the stress-strain curve obtained using machine vision is compared to the stress-strain curve obtained from the DIC results. RMSE values of the strain from the machine vision and DIC were less than 0.005. In addition, as a measurement example, a bending angle and springback measurement according to bending deformation, and a moving position measurement of a punch, a blank holder, and a die by time change were performed. Using the proposed method, the deformation and displacement of the materials were measured precisely and easily.

Characterization of Interfacial Adhesion of Cu-Cu Bonding Fabricated by Thermo-Compression Bonding Process (열가압 접합 공정으로 제조된 Cu-Cu 접합의 계면 접합 특성 평가)

  • Kim, Kwang-Seop;Lee, Hee-Jung;Kim, Hee-Yeoun;Kim, Jae-Hyun;Hyun, Seung-Min;Lee, Hak-Joo
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.34 no.7
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    • pp.929-933
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    • 2010
  • Four-point bending tests were performed to investigate the interfacial adhesion of Cu-Cu bonding fabricated by thermo-compression process for three dimensional packaging. A pair of Cu-coated Si wafers was bonded under a pressure of 15 kN at $350^{\circ}C$ for 1 h, followed by post annealing at $350^{\circ}C$ for 1 h. The bonded wafers were diced into $30\;mm\;{\times}\;3\;mm$ pieces for the test. Each specimen had a $400-{\mu}m$-deep notch along the center. An optical inspection module was installed in the testing apparatus to observe crack initiation at the notch and crack propagation over the weak interface. The tests were performed under a fixed loading speed, and the corresponding load was measured. The measured interfacial adhesion energy of the Cu-to-Cu bonding was $9.75\;J/m^2$, and the delaminated interfaces were analyzed after the test. The surface analysis shows that the delamination occurred in the interface between $SiO_2$ and Ti.

Analysis of Rolling Contact Surface on PM-High Speed Steel by X-ray Diffraction (구름접촉을 하는 분말고속도공구강의 X선을 이용한 표면성상해석)

  • 이한영;김용진;배종수
    • Tribology and Lubricants
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    • v.19 no.1
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    • pp.1-8
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    • 2003
  • Recently, PM-high speed steel(PM-HSS) has reportedly been a good alternative material for rolling mill because of its superior performance to conventional HSS. This paper has been aimed to investigate the possibility for application to rolling contact element for PM-HSS by X-ray diffraction technique. The X-ray elastic constant for PH-HSS has been found by X-ray diffraction during the four-point bending test. Residual stress and half-value breadth on the contact surface during rolling contact fatigue process by X-ray diffraction have also been measured. The result of this study shows that the application of X-ray diffraction technique to PM-HSS could be as possible alternative material as conventional HSS. Half-value breadth on rolling contact surface by X-ray diffraction is not changed during rolling contact fatigue process. On the other hand, the residual stress is changed. This suggests that dislocation reaction has been hardly occurred in rolling contact, depending on super-saturated carbon in PM-HSS.