• Title, Summary, Keyword: quasi-static test

Search Result 296, Processing Time 0.041 seconds

Deformation and Fracture Behavior of Structural Bulk Amorphous Metal under Quasi-Static Compressive Loading (준정적 압축하에서 구조용 벌크 아몰퍼스 금속의 변형 및 파괴거동)

  • Shin, Hyung-Seop;Ko, Dong-Kyun;Oh, Sang-Yeob
    • Transactions of the Korean Society of Mechanical Engineers A
    • /
    • v.27 no.10
    • /
    • pp.1630-1635
    • /
    • 2003
  • The deformation and fracture behaviors of a bulk amorphous metal, Zr-based one (Zr$\_$41.2/Ti$\_$13.8/Cu$\_$12.5/Ni$\_$10/Be$\_$22.5/: Vitreloy), were investigated over a strain rate range (7x10$\^$-4/~4 s$\^$-1/). The uniaxial compression test and the indentation test using 3mm-diameter WC balls were carried out under quasi-static loading conditions. As a result, at the uniaxial compressive state, the fracture stress of the material was very high (~1,700MPa) and the elastic strain limit was about 2%. The fracture strength showed a strain rate independent behavior up to 4 s$\^$-1/. Using indentation tests, the plastic deformation behavior of the Zr-based BAM up to a large strain value of 15% could be achieved, even though it was the deformation under locally constrained condition. The Meyer hardness of the Zr-based BAM measured by static indentation tests was about 5 GPa and it revealed negligible strain hardening behavior. At indented sites, the plastic indentation occurred forming a crater and well-developed multiple shear bands were generated around it along the direction of 45 degree when the indentation load exceeded 7kN. With increasing indentation load, shear bands became dense. The fracture surface of the specimen after uniaxial compressive tests showed vein-like pattern, typical morphology of many BAMs.

The research on static and dynamic mechanical properties of concrete under the environment of sulfate ion and chlorine ion

  • Nie, Liangxue;Xu, Jinyu;Bai, Erlei
    • Computers and Concrete
    • /
    • v.20 no.2
    • /
    • pp.205-214
    • /
    • 2017
  • The Hydraulically driven test system and ${\Phi}100mm$ split Hopkinson pressure bar(SHPB) test device were employed to research the quasi-static and dynamic mechanical properties of concrete specimens which has been immersed for 60 days in sodium sulfate (group S1) and sodium chloride (group S2) solution, the evolution of their mass during corrosive period was explored at the same time, and the mechanism of performances lost was analyzed from the microscopic level by using scanning electron microscope. Results of the experimental indicated that: their law of mass both presents the trend of continuous rising during corrosive period, and it increases rapidly on the early days, the mass growth of group S1 and group S2 in first 7 days are 76.78% and 82.82% of their total increment respectively; during the corrosive period, the quasi-static compressive strength of specimens in two groups are significantly decreased, both of which present the trend of increase first and then decrease, the maximum growth rate of group S1 and group S2 are 7.52% and 12.71% respectively, but they are only 76.23% and 82.84% of specimens which under normal environment (group N) on day 60; after immersed for 60 days, there were different decrease to dynamic compressive strength and specific energy absorption, and so as their strain rate sensitivities. So the high salinity environment has a significant effect of weaken the quasi-static and dynamic mechanical performance of concrete.

A Constitutive Equation with Impulse-Momentum Theory for the Expanded Polypropylene (충격량-운동량 이론을 접목시킨 발포 폴리프로필렌의 구성방정식)

  • Kim, Byeong Kil;Cho, Jae Ung;Jeong, Kwang Young;Kim, Nam Hoon;Oh, Bum S.;Hahn, Youngwon;Cheon, Seong S.
    • Composites Research
    • /
    • v.29 no.3
    • /
    • pp.91-97
    • /
    • 2016
  • In this paper, impulse-momentum theory was coupled to a constitutive equation both for implementing quasi-static and impact characteristics of EPP (Expanded polypropylene). Also, parameters which have physical meanings were expressed as functions of relative density. Simultaneous nonlinear Newton-Raphson method was applied to find the proper values for parameters in the constitutive equation along with quasi-static test data. Results from the impulse-momentum theory coupled constitutive equation showed good agreement with experimental data and the potential to be applied to different material type polymeric foam.

Fatigue Life Evaluation of Spot Weldments of SPC Sheet Including Strain Rate Effect (변형률속도효과를 고려한 일반냉연강판 점용접부의 피로수명평가)

  • Song, Joon-Hyuk;Nah, Seok-Chan;Yu, Hyo-Sun;Kang, Hee-Yong;Yang, Sung-Mo
    • Transactions of the Korean Society of Automotive Engineers
    • /
    • v.14 no.1
    • /
    • pp.48-53
    • /
    • 2006
  • A methodology is described for predicting the fatigue life of the resistance spot weldment including strain rate effect. Because it is difficult to perform a physical failure test with high strain rate, an analytical method is necessary to get the mechanical properties of various strain rate, To this end, quasi-static tensile-shear tests at several strain rate were performed on spot weldments of SPC. These test provided the empirical data with the strain rate. With these results, we formulated the function of fatigue life prediction using the lethargy coefficient which is the global material property from tensile test. And, we predicted the fatigue life of spot weldment at dynamic strain rate. To confirm this method for fatigue life prediction, analytical results were compared with the experimental fatigue data.

Seismic performance of RC bridge piers subjected to moderate earthquakes

  • Chung, Young Soo;Park, Chang Kyu;Lee, Dae Hyoung
    • Structural Engineering and Mechanics
    • /
    • v.24 no.4
    • /
    • pp.429-446
    • /
    • 2006
  • Experimental investigation was conducted to evaluate the seismic ductility of earthquake-experienced concrete columns with an aspect ratio of 2.5. Eight circular concrete columns with a diameter of 600 mm were constructed with three test parameters: confinement ratio, lap-splice of longitudinal bars, and retrofitting with Fiber Reinforced Polymer (FRP) materials. The objective of this research is to examine the seismic performance of RC bridge piers subjected to a Quasi static test (QST), which were preliminary tested under a series of artificial earthquake motions referred to as a Pseudo dynamic test (PDT). The seismic enhancement effect of FRP wrap was also investigated on these RC bridge piers. Six specimens were loaded to induce probable damage by four series of artificial earthquakes, which were developed to be compatible with earthquakes in the Korean peninsula by the Korea Highway Corporation (KHC). Directly after the PDT, six earthquake-experienced columns were subjected to inelastic cyclic loading under a constant axial load of $0.1{f_c}^{\prime}A_g$. Two other reference specimens without the PDT were also subjected to similar quasi-static loads. Test results showed that specimens pre-damaged by moderate artificial earthquakes generally demonstrated good residual seismic performance, which was similar to the corresponding reference specimen. Moreover, RC bridge specimens retrofitted with wrapping fiber composites in the potential plastic hinge region exhibited enhanced flexural ductility.

Performance Evaluation on Static Loading and Cyclic Loading for Structural Insulated Panels (구조용단열패널의 정적가력과 반복가력 성능 평가)

  • Nah, Hwan-Seon;Lee, Hyeon-Ju;Choi, Sung-Mo
    • Journal of the Korean Society for Advanced Composite Structures
    • /
    • v.4 no.1
    • /
    • pp.33-39
    • /
    • 2013
  • Structural insulated panels, structurally performed panels consisting of a plastic insulation bonded between two structural panel facings, are one of emerging products with a viewpoint of its energy and construction efficiencies. These components are applicable to fabricated wood structures. In Korea, there are few technical documents regulated structural performance and engineering criteria in domestic market. This study was conducted to identify fundamental performance of both monotonic load and quasi static cyclic load for SIPs in shear wall application. Static test results showed that maximum load was 44.3kN, allowable shear load was 6.1kN/m, shear stiffness was 1.23 M N/m, and ductility ratio was 3.6. Cyclic test was conducted by two kinds of specimens : single panel and double panels. Cyclic test results, which were equivalent to static test results, showed that maximum load was 45.42kN, allowable shear load was 6.3kN/m. Furthermore the accumulated energy dissipation capability for double panels was as 2.3 times as that for single panel. From performance of structural tests, it was recommended that the allowable shear load for panels was at least 6.1kN/m.

Collapse Characteristics on Width Ratio and Flange Spot-Weld Pitch for Hat-Shaped Members (모자형 단면부재의 폭비와 플랜지 용접간격에 따른 압궤특성)

  • Cha, Cheon-Seok;Gang, Jong-Yeop;Kim, Yeong-Nam;Kim, Jeong-Ho;Kim, Seon-Gyu;Yang, In-Yeong
    • Transactions of the Korean Society of Mechanical Engineers A
    • /
    • v.25 no.1
    • /
    • pp.98-105
    • /
    • 2001
  • The fundamental and widely used spot welded sections of automobiles (hat and double hat-shaped section members) absorb most of the energy in a front-end collision. The sections were tested on axial static(10mm/min) and quasi-static(1000mm/min) loads. Based on these test results, specimens with various thickness, shape and spot weld pitch on the flange have been tested with impact velocity(7.19m/sec) the same as a real life car clash. Characteristics of collapse have been reviewed and a structure of optimal energy absorbing capacity is suggested.

Dynamic Test Results Assessment on the Optical Bench of LEO Satellite (저궤도 지구관측위성의 광학탑재체 지지구조물 동환경시험 결과분석)

  • Kim, Kyung-Won;Kim, Jin-Hee;Rhee, Ju-Hun;Kim, Sun-Won;Jin, Ik-Min;Park, Jong-Sung
    • Proceedings of the Korean Society for Noise and Vibration Engineering Conference
    • /
    • /
    • pp.242-245
    • /
    • 2006
  • This paper is an assessment on the dynamic test results of optical bench for LEO satellite. According to the design requirements, optical bench was designed and manufactured. Dynamic test was performed to verify stability of optical bench. Low level random vibration test, sine burst test and sine vibration test are carried out to identify dynamic characteristics and to verify static strength and safety under quasi-static load conditions. From the result it can be stated that the optical bench is well qualified under the launch environmental conditions.

  • PDF

The Estimation of Fatigue Strength of Structure with Practical Dynamic Force by Inverse Problem and Lethargy Coefficient (구조물의 피로강도평가를 위한 역문제 및 무기력계수에 의한 실동하중해석)

  • 양성모;송준혁;강희용;노홍길
    • Transactions of the Korean Society of Automotive Engineers
    • /
    • v.12 no.1
    • /
    • pp.106-113
    • /
    • 2004
  • Most of mechanical structures are composed of many substructures connected to one another by various types of mechanical joints. In automotive engineering, it is important to study these connected structures under various dynamic forces for the evaluations of fatigue life and stress concentration exactly. In this study, the dynamic response of vehicle structure to external forces is classified an inverse problem involving strains from the experiment and the analysis. The practical dynamic forces are determined by the combination of the analytical and experimental method with analyzed strain by quasi-static finite element analysis under unit force and with measured strain by a strain gage under driving load, respectively. In a stressed body, inter-molecular chemical bonds are failed beyond the certain magnitude. The failure of molecular structure in material is considered as a time process of which rate is determined by mechanical stress. That is, the failure of inter-molecular chemical bonds is the fatigue lift of material. This kinetic concept is expressed as lethargy coefficient. And S-N curve is obtained with the lethargy coefficient from quasi-static tensile test. Equivalent practical dynamic force is obtained from the identification of practical dynamic force for one loading point. Using the practical dynamic force and S-N curve, fatigue life of a window pillar is analyzed with FEM under the identified force by the procedure of above mentioned.

Study on Reinforcement Effect of Circular RC Columns by Helical Bar Under Cyclic Lateral Load (반복 횡하중을 받는 원형 철근콘크리트 기둥의 Helical Bar 보강효과에 대한 연구)

  • Kim, Seong-Kyum;Park, Jong-Kwon;Han, Sang-Hee;Kim, Byung-Cheol;Jang, Il-Young
    • Journal of the Korea institute for structural maintenance and inspection
    • /
    • v.18 no.1
    • /
    • pp.48-58
    • /
    • 2014
  • In this study, quasi-static according to the displacement-controlled (strain control) method tests on RC columns for seismic reinforcement performance in accordance with the provisions of the seismic design and construction before 1992 design code for highway bridges in korea. Used reinforcement that improves the performance of Inorganic Helical Bar, a kind of alloy steel, circular columns were tested outside the seismic reinforcing. In the experiment, fracture behavior, lateral load-displacement relation, ductility and energy assessment evaluation was performed through tests. The variables in experimental are section force of reinforcement, spiral reinforcement spacing, reinforcement method. Improved seismic performance and effect were confirmed through quasi-static test experiments. The results of study confirmed determination the appropriate size of reinforcement, reinforcement forces, spacing and selection of the type required, furthermore, not only mechanical reinforcement but also substitution of high-strength concrete reinforced with concrete cover improved seismic performance.