• Title, Summary, Keyword: three-point bending test

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Measurement of the mixed mode fracture strength of green sandstone using three-point bending specimens

  • Li, Yifan;Dong, Shiming;Pavier, Martyn J.
    • Geomechanics and Engineering
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    • v.20 no.1
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    • pp.9-18
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    • 2020
  • Three-point bending specimens have been used to investigate the mixed mode fracture of green sandstone. Dimensionless stress intensity factors and T-stresses were calculated first by using the finite element method for various crack lengths, crack angles and span to length ratios. It is shown that three-point bending specimens can provide the whole range of mode mixities from pure mode I to pure mode II, provided suitable values are chosen for the crack angle and span to length ratio. The fracture test results were also used to compare with predictions of different criteria. These comparisons show that modified criteria including the influence of the T-stress agree better with experiment than the conventional criteria but that no one criterion matches perfectly the test results.

Test and Analysis of Triaxially Braided Composite Circular Arch under Three-Point Bending

  • Nega, Biruk F.;Woo, Kyeongsik;Lee, Hansol
    • Composites Research
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    • v.32 no.5
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    • pp.249-257
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    • 2019
  • In this paper, the buckling behavior of triaxially braided circular arch with monosymmetric open section subjected to three-point bending was studied experimentally and numerically. First, test specimens were manufactured using vacuum assisted resin transfer molding (VARTM). Then the specimen was tested under three-point bending to determine the ultimate buckling strength. Before performing the numerical analysis, effective material properties of the braided composite were obtained through micro-meso scale analysis virtual testing validated with available test results. Then linear buckling analysis and geometrically non-linear post buckling analysis, established to simulate the test setup, were performed to study the buckling behavior of the composite frame. Analysis results were compared with experimentally obtained ones for verification. The effect of manufacturing defects of tow misalignment, irregular surface and resin rich region, and uncertainties during test setup were studied using numerical models. From the numerical analyses performed it was observed that both manufacturing defect and uncertainties had effect on the buckling behavior and strength.

Numerical simulation of fracture and damage behaviour of concrete at different ages

  • Jin, Nanguo;Tian, Ye;Jin, Xianyu
    • Computers and Concrete
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    • v.4 no.3
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    • pp.221-241
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    • 2007
  • Based on the experiment results, the damage and fracture behavior of concrete at the ages of 1d, 2d, 7d and 28d, in three-point bending and uniaxial tensile tests, were simulated with a finite element program, ABAQUS. The critical stress intensity factor $K_{IC}^s$ and the critical crack tip opening displacement ($CTOD_C$) of concrete were calculated with effective-elastic crack approach for the three-point bending test of grade C30 concrete. Based on the crack band model, a bilinear strain-softening curve was derived to simulate the LOAD-CMOD curves and LOAD-Displacement curves. In numerical analysis of the uniaxial tension test of concrete of grade C40, the damage and fracture mechanics were combined. The smeared cracking model coupling with damaged variable was adopted to evaluate the onset and development of microcracking of uniaxial tensile specimen. The uniaxial tension test was simulated by invoking the damage plastic model which took both damage and plasticity as inner variables with user subroutines. All the numerical simulated results show good agreement with the experimental results.

Effects of High Temperature-moisture on Corrosion and Mechanical Properties for Sn-system Solder Joints (고온고습환경이 Sn계 무연솔더의 부식 및 기계적 특성에 미치는 영향)

  • Kim, Jeonga;Park, Yujin;Oh, Chul Min;Hong, Won Sik;Ko, Yong-Ho;Ahn, Sungdo;Kang, Namhyun
    • Journal of Welding and Joining
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    • v.35 no.3
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    • pp.7-14
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    • 2017
  • The effect of high temperature-moisture on corrosion and mechanical properties for Sn-0.7Cu, Sn-3.0Ag-0.5Cu (SAC305) solders on flexible substrate was studied using Highly Accelerated Temperature/Humidity Stress Test (HAST) followed by three-point bending test. Both Sn-0.7Cu and SAC305 solders produced the internal $SnO_2$ oxides. Corrosion occurred between the solder and water film near flexible circuit board/copper component. For the SAC305 solder with Ag content, furthermore, octahedral corrosion products were formed near Ag3Sn. For the SAC305 and Sn-0.7Cu solders, the amount of internal oxide increased with the HAST time and the amount of internal oxides was mostly constant regardless of Ag content. The size of the internal oxide was larger for the Sn-0.7Cu solder. Despite of different size of the internal oxide, the fracture time during three-point bending test was not significantly changed. It was because the bending crack was always initiated from the three-point corner of the chip. However, the crack propagation depended on the oxides between the flexible circuit board and the Cu chip. The fracture time of the three-point bending test was dependent more on the crack initiation than on the crack propagation.

The effect of preheat treatment on ceramic to metal bond strength (도재-금속의 결합 강도에 미치는 비금속 합금의 열처리 효과)

  • Kim, Chi-Young;Kim, Young-Gon; Cho, Hyun-Seol
    • Journal of Technologic Dentistry
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    • v.24 no.1
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    • pp.33-41
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    • 2002
  • In dental prosthetics, the application of metal-ceramic restorations has steadily increased since their introduction. This is due to excellent esthetics in combination with high mechanical stability. In order to optimum bond strength between metal and ceramics, controlled oxidation of metal substructure is essential factor. Beryllium containing and beryllium free Ni-Cr alloys for metal-ceramic restorations were evaluated for the metal-ceramic bond strength by changing heat treatment for oxide formation. A mechanical three-point bending test was employed to evaluate the interfacial bond strength of metal-ceramic. In each metal, plate type specimens were used for mechanical three-point bending test. With Ni-Cr alloys for metal ceramics, mechanical three-point bending test showed that double degassing was more available preheat treatment method than another. It was found that beryllium containing Ni-Cr alloys are more effective than beryllium-free for metal-ceramic bond strength.

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A Numerical Study on The Three Point Bending Behavior of Aluminum Foam Filled Stainless Steel Tube (알루미늄 폼으로 충진된 스테인레스 관의 3 점 굽힘 특성에 관한 수치적 연구)

  • Ha, San;Kim, Am-Kee;Cheon, Seong-Sik;Lee, Chang-Hun;Lee, Hyo-Jin;Cho, Seong-Seock
    • Proceedings of the KSME Conference
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    • pp.388-393
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    • 2004
  • A comprehensive numerical study on the three point bending behavior of Aluminum foam-filled stainless steel tube has been performed. Aluminium alloy foams with various densities were produced and their mechanical properites were evaluated. Finite element(FE) analysis of three point bending test was performed to evaluate bending behavior of foam filled cylindrical structures. Results showed that foam filling offered remarkable increase of bending resistance and enhanced the crashworthiness of the structure. It turned out to prevent the inward fold formation at the compression flange, resulted into the multiple propagating folds and increased the load carrying capacity.

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Bending Performance Evaluation of Reinforced Aluminum Square Tube Beams (보강 알루미늄 사각관 보의 굽힘 성능평가)

  • Lee Sung-Hyuk;Choi Nak-Sam
    • Transactions of the Korean Society of Automotive Engineers
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    • v.13 no.5
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    • pp.171-180
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    • 2005
  • Bending performances of aluminum square tube beams reinforced by aluminum plates under three point bending loads have been evaluated using experimental tests combined with theoretical and finite element analyses. A finite element simulation for the three-point bending test was performed. Basic properties of aluminum materials used for initial input data of the finite element simulation were obtained from the true stress-true strain curves of specimens which had been extracted from the Al tube beams. True stresses were determined from applied loads and cross-sectional area records of a tensile specimen with a rectangular cross-section by real-time photographing, and true strains were obtained from in-situ local elongation measurements of the specimen gage portion by the multi-point scanning laser extensometer. Six kinds of aluminum tube beam specimens adhered by aluminum plates were employed fur the bending test. The bending deformation behaviors up to the maximum load described by the numerical simulation were in good agreement with experimental ones. After passing the maximum load, reinforcing plate was debonded from the aluminum tube beam. An aluminum tube beam strengthened by aluminum plate on the upper web showed an excellent bending capability.

Study on the Improvement of the Image Analysis Speed in the Digital Image Correlation Measurement System for the 3-Point Bend Test

  • Choi, In Young;Kang, Young June;Hong, Kyung Min;Kim, Seong Jong;Lee, Gil Dong
    • Journal of the Optical Society of Korea
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    • v.18 no.5
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    • pp.523-530
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    • 2014
  • Machine material and structural strain are critical factors for appraising mechanical properties and safety. Particularly in three and four-point bending tests, which appraise the deflection and flexural strain of an object due to external force, measurements are made by the crosshead movement or deflection meter of a universal testing machine. The Digital Image Correlation (DIC) method is one of the non-contact measurement methods. It uses the image analyzing method that compares the reference image with the deformed image for measuring the displacement and strain of the objects caused by external force. Accordingly, the advantage of this method is that the object's surface roughness, shape, and temperature have little influence. However, its disadvantage is that it requires extensive time to compare the reference image with the deformed image for measuring the displacement and strain. In this study, an algorithm is developed for DIC that can improve the speed of image analysis for measuring the deflection and strain of an object caused by a three-point bending load. To implement this algorithm for improving the speed of image analysis, LabVIEW 2010 was used. Furthermore, to evaluate the accuracy of the developed fast correlation algorithm, the deflection of an aluminum specimen under a three-point bending load was measured by using the universal test machine and DIC measurement system.

Study on the Measurement of Flexural Strain Using the Digital Image Correlation in the Three-Point Bending Test (이미지 상관법을 이용한 휨 변형률 측정에 관한 연구)

  • Choi, In Young;Kang, Young June;Hong, Kyung Min;Ko, Kwang Su;Lee, Hak Sung
    • Journal of the Korean Society of Manufacturing Technology Engineers
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    • v.23 no.5
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    • pp.498-504
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    • 2014
  • Displacements and strains are very important for material evaluation as critical factors to a machine's life cycle and safety. Typically, the strain gauge has been employed to measure displacement and strain. However, this contact-type measurement method has disadvantages that are not quantified under the test conditions of a specific object shape, surface roughness, and temperature. In this paper, the measurement of deflection and flexural strain due to the three-point bending test is presented, employing Digital Image Correlation (DIC) methods. In order to ensure measurement reliability, DIC and universal test machine methods were compared by measuring the deflections and flexural strains developed by such bending tests.

High Temperature Properties of Fiber Reinforced Composites under the Different Loading Conditions

  • Weiguang, Hu;Park, Soo-Jeong;Kim, Yun-Hae
    • Composites Research
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    • v.30 no.3
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    • pp.188-192
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    • 2017
  • The mechanical properties of composites are significantly affected by external environment. It is essential to understand the degradation of material performance and judge the material's lifetime in advance. In the current research, changes in mechanical properties of glass fiber and unsaturated polyester composite materials (GFRP, Glass fiber reinforced plastic) were investigated under different bending stress and submerged in hot water at a temperature of $80^{\circ}C$. Loading time of 100 H (hours), 200 H, 400 H, 600 H, 800 H for testing under stresses equal to 0% (stress-free state), 30%, 50% and 70% of the ultimate strength was applied on the GFRP specimens. From the values of bending stress, obtained from three-point bending test, fracture energy, failure time, and life curve were analysed. Moreover, a normalized strength degradation model for this condition was also developed. It was observed that within 100 H, the decline rate of the bending strength was proportional to the pressure.