• Title/Summary/Keyword: elastic-plastic behavior

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Estimation of Elastic Plastic Behavior Fracture Toughness Under Hydrogen Condition of Inconel 617 from Small Punch Test (Inconel 617 재료의 소형펀치 실험을 이용한 수소취화처리재의 탄-소성 거동 및 파괴인성 유추)

  • Kim, Nak Hyun;Kim, Yun Jae;Yoon, Kee Bong;Ma, Young Hwa
    • Transactions of the Korean Society of Mechanical Engineers A
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    • v.37 no.6
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    • pp.753-760
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    • 2013
  • The hydrogen embrittlement of metallic materials is an important issue from the viewpoint of structural integrity. In this regard, the estimation of mechanical properties and fracture toughness under hydrogen conditions provides very important data. This study provides an experimental validation of the approach for simulating the small punch of Inconel 617 using finite element damage analysis, as recently proposed by the authors, and applies an inverse method for the determination of the constitutive tensile behavior of materials. The mechanical properties obtained from the inverse method are compared with those obtained from the tensile test and validated. The mechanical properties and fracture toughness are predicted by using the inverse method and finite element damage analysis.

A study on fatigue properties of GFRP in synthetic sea water (인공해수중 GFRP의 피로특성에 관한 연구)

  • 김연직;임재규
    • Transactions of the Korean Society of Mechanical Engineers
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    • v.17 no.6
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    • pp.1351-1360
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    • 1993
  • The fatigue behavior of GFRP composites is affected by environmental parameters. Therefore, we have to study on effect of sea water on fatigue behavior of GFRP composites as to maintain the safety and confidence in design of ocean structure of GFRP. In this paper, we investigated the fatigue properties of chopped strand glass mat/polyester composite in synthetic sea water. (pH 8.2) In case of the glass fiber (CSM type) reinforced polyester composite materials, the fatigue crack in the both dry and wet specimens tested in air or synthetic sea water occurred at the initial of cycle. Thereafter, it was divided with two regions that one decreased with the crack extension and the other increased with the crack extension. The transition point occurred during the crack propagation shifted to high ${\Delta}K$ value as load increase but its point is not changed regardless of immersion or test environment under a constant load. The synthetic sea water degrades the bond strength between fiber and matrix, thereby the tendency of rapid deceleration and acceleration of the crack growth was appeared.

Behavior of Concrete-Filled Square Tubular Beam-Column under Cyclic Load (반복하중을 받는 콘크리트충전 각형강관 보-기둥의 거동)

  • Kang, Chang-Hoon;Moon, Tae-Sup
    • Journal of Korean Society of Steel Construction
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    • v.12 no.4 s.47
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    • pp.387-395
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    • 2000
  • The purpose of this research is to evaluate the capacity of strength and plastic deformation of those members, and provide experimental data on the seismic behavior of these members as a basis for developing guidelines for designing seismically resistant concrete-filled steel tubular columns. Eighteen cantilever-type specimens were tested under constant axial load and cyclically lateral load as models of bottom columns in high-rise building. The parameters studied in the test program included, are width-thickness ratio of steel tube, slenderness ratio (Lo/D) and axial force ratio. From the test results, the effects of parameters on the strength, the deformation capacity, energy absorption capacity are discussed. The specimen flexural capacity under combined axial and lateral loading was found to be almost accurately predicted by criteria AIJ and AISC-LRFD providing conservative results. Therefore KSSC for encased composite column can be applied to the concrete filled column if composite section and elastic modulus are modified according to AIJ and AISC-LRFD. Finally, the proposed flexural capacity considering confinement effects is a food agreement on the tests results.

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Parametric Study of MD Constitutive Model for Coarse-Grained Soils (조립재료에 대한 MD구성모델의 매개 변수 연구)

  • Choi, Changho
    • Journal of the Korean Geosynthetics Society
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    • v.12 no.1
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    • pp.11-19
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    • 2013
  • Coarse-grained soils are typical engineering materials commonly used in many civil engineering applications such as structural fills, subgrade and drainage fills for dam, railway and bridge. Various researches have been performed with related to constitutive laws for numerical analysis of such structures. This paper presents a parametric study for a constitutive model for coarse grained materials. The model is a kind of the bounding surface models based on critical state theory. A distinct feature of the model is to capture the response of coarse-grained materials with different void ratios and confining pressures using a single set of model parameters. The model behavior is defined with a set of elastic parameters, critical state parameters, and model-specific parameters. The parametric study was performed for the model-specific parameters. The result of parametric study shows that the model is capable to capture stress-dilatancy behavior and kinematic-hardening under non-associative plastic flow.

Failure Behavior of Laser Cladding Layer used by Fe-based Bulk Metallic Glass (Fe계 벌크 비정질 합금을 이용한 레이저 용접층의 파손 거동)

  • Lim, Byung-Chul;Kim, Dae-Hwan;Park, Sang-Heup
    • Journal of the Korea Academia-Industrial cooperation Society
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    • v.16 no.9
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    • pp.5743-5747
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    • 2015
  • In this study, Fe-based bulk amorphous alloy powder manufactured using gas atomization fabrication was used for laser welding. the fracture behavior of welding layer were analyzed. Tensile test results show that the destruction occurred immediately after the elastic deformation, After plastic deformation of the substrate, the destruction occurred. The actual maximum tensile strength of the welding layer and the substrate are 959.9MPa and 220.4MPa. welding layer were each $485.5{\pm}21$ and $197.4{\pm}14$ to the substrate and the actual microhardness, The welding layer has very high hardness. The welding layer showed a very weak fine acicular structure. The base material was shown in the micro structure appear a coarse grain. SEM observations of the fracture after the tensile test. Fracture morphology of the base metal and the welding layer showed ductile fracture and brittle fracture, respectively.

Three dimensional dynamic soil interaction analysis in time domain through the soft computing

  • Han, Bin;Sun, J.B.;Heidarzadeh, Milad;Jam, M.M. Nemati;Benjeddou, O.
    • Steel and Composite Structures
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    • v.41 no.5
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    • pp.761-773
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    • 2021
  • This study presents a 3D non-linear finite element (FE) assessment of dynamic soil-structure interaction (SSI). The numerical investigation has been performed on the time domain through a Finite Element (FE) system, while considering the nonlinear behavior of soil and the multi-directional nature of genuine seismic events. Later, the FE outcomes are analyzed to the recorded in-situ free-field and structural movements, emphasizing the numerical model's great result in duplicating the observed response. In this work, the soil response is simulated using an isotropic hardening elastic-plastic hysteretic model utilizing HSsmall. It is feasible to define the non-linear cycle response from small to large strain amplitudes through this model as well as for the shift in beginning stiffness with depth that happens during cyclic loading. One of the most difficult and unexpected tasks in resolving soil-structure interaction concerns is picking an appropriate ground motion predicted across an earthquake or assessing the geometrical abnormalities in the soil waves. Furthermore, an artificial neural network (ANN) has been utilized to properly forecast the non-linear behavior of soil and its multi-directional character, which demonstrated the accuracy of the ANN based on the RMSE and R2 values. The total result of this research demonstrates that complicated dynamic soil-structure interaction processes may be addressed directly by passing the significant simplifications of well-established substructure techniques.

Characteristic Analysis of Superelastic Shape Memory Alloy Long-Lasting Damper with Pretension (긴장력이 적용된 초탄성 형상기억합금 장수명 댐퍼의 특성 분석)

  • Lee, Heon-Woo;Kim, Young-Chan;Hu, Jong-Wan
    • KSCE Journal of Civil and Environmental Engineering Research
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    • v.44 no.1
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    • pp.11-17
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    • 2024
  • A seismic structure is an earthquake-resistant design that dissipates seismic energy by equipping the structure with a device called a damper. As research efforts to reduce earthquake damage continue to rise, technology for isolating vibrations in structures has evolved by altering the materials and shapes of dampers. However, due to the inherent nature of the damper, there are an unescapable restrictions on the extent of plastic deformation that occurs in the material to effectively dissipate energy. Therefore, in this study, we proposed a long-life damper that offers semi-permanently usage and enhances structural performance by applying additional tension which is achieved by utilizing super elastic shape memory alloy (SSMA), a material that self-recovers after deformation. To comprehensively understand the behavior of long-life dampers, finite element analysis was performed considering the design variables such as material, wire diameter, and presence of tension, and response behavior was derived to analyze characteristics such as load resistance, energy dissipation, and residual displacement to determine the performance of long-life dampers in seismic structure. Excellence has been proven from finite element analysis results.

Anchorage mechanism of inflatable steel pipe rockbolt depending on rock stiffness (팽창형 강관 록볼트의 암반 강성에 따른 정착 거동 특성)

  • Kim, Kyeong-Cheol;Kim, Ho-Jong;Jung, Young-Hoon;Shin, Jong-Ho
    • Journal of Korean Tunnelling and Underground Space Association
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    • v.19 no.2
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    • pp.249-263
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    • 2017
  • The expansion behavior of inflatable steel pipe rockbolt shows geometric nonlinearity due to its ${\Omega}-shaped$ section. Previous studies on the anchoring behavior of inflatable steel pipe rockbolt were mainly performed using theoretical method. However, those studies oversimplified the actual behavior by assuming isotropic expansion of inflatable steel pipe rockbolt. In this study, the anchoring behavior of the inflatable steel pipe rockbolt were investigated by the numerical method considering the irregularity of pipe expansion and other influencing factors. The expansion of inflatable steel pipe rockbolt, the contact stress distribution and the change of the average contact stress and the contact area during installation were analyzed. The contact stresses were developed differently depending on the constitutive behavior of rocks. Small contact stresses occurred in steel pipes installed in elasto-plastic rock compared to steel pipes installed in elastic rock. Also, the anchoring behaviors of the inflatable steel pipe rockbolt were different according to the stiffness of the rock. The steel pipe was completely unfolded in the case of the stiffness smaller than 0.5 GPa, but it was not fully unfolded in the case of the stiffness larger than 0.5 GPa for the given analysis condition. When the steel pipe is completely unfolded, the contact stress increases as the rock stiffness increases. However, the contact stress decreases as the rock stiffness increases when the steel pipe is not fully expanded.

Seismic behavior of K-type eccentrically braced frames with high strength steel based on PBSD method

  • Li, Shen;Wang, Chao-yu;Li, Xiao-lei;Jian, Zheng;Tian, Jian-bo
    • Earthquakes and Structures
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    • v.15 no.6
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    • pp.667-685
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    • 2018
  • In eccentrically braced steel frames (EBFs), the links are fuse members which enter inelastic phase before other structure members and dissipate the seismic energy. Based on the force-based seismic design method, damages and plastic deformations are limited to the links, and the main structure members are required tremendous sizes to ensure elastic with limited or no damage. Force-based seismic design method is very common and is found in most design codes, it is unable to determine the inelastic response of the structure and the damages of the members. Nowadays, methods of seismic design are emphasizing more on performance-based seismic design concept to have a more realistic assessment of the inelastic response of the structure. Links use ordinary steel Q345 (the nominal yielding strength $f_y{\geq}345MPa$) while other members use high strength steel (Q460 $f_y{\geq}460MPa$ or Q690 $f_y{\geq}690MPa$) in eccentrically braced frames with high strength steel combination (HSS-EBFs). The application of high strength steels brings out many advantages, including higher safety ensured by higher strength in elastic state, better economy which results from the smaller member size and structural weight as well as the corresponding welding work, and most importantly, the application of high strength steel in seismic fortification zone, which is helpful to popularize the extensive use of high strength steel. In order to comparison seismic behavior between HSS-EBFs and ordinary EBFs, on the basis of experimental study, four structures with 5, 10, 15 and 20 stories were designed by PBSD method for HSS-EBFs and ordinary EBFs. Nonlinear static and dynamic analysis is applied to all designs. The loading capacity, lateral stiffness, ductility and story drifts and failure mode under rare earthquake of the designs are compared. Analyses results indicated that HSS-EBFs have similar loading capacity with ordinary EBFs while the lateral stiffness and ductility of HSS-EBFs is lower than that of EBFs. HSS-EBFs and ordinary EBFs designed by PBSD method have the similar failure mode and story drift distribution under rare earthquake, the steel weight of HSS-EBFs is 10%-15% lower than ordinary EBFs resulting in good economic efficiency.

A Study on Seismic Performance Evaluation of Tunnel to Considering Material Nonlinearity (재료의 비선형성을 고려한 터널의 내진성능평가에 관한 연구)

  • Choi, Byoungil;Ha, Myungho;Noh, Euncheol;Park, Sihyun;Kang, Gichun
    • Journal of the Korea institute for structural maintenance and inspection
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    • v.26 no.3
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    • pp.92-102
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    • 2022
  • Various numerical analysis models can be used to evaluate the behavior characteristics of tunnel facilities which are representative underground structures. In general, the Mohr-Coulomb model, which is most often used for numerical analysis, is an elastic-perfect plastic behavior model. And the deformation characteristics are the same during the load increase-load reduction phase. So there is a problem that the displacement may appear different from the field situation in the case of excavation analysis. In contrast, the HS-small strain stability model has a wide range of applications for each ground. And it is known that soil deformation characteristics can be analyzed according to field conditions by enabling input of initial elastic modulus and nonlinear curve parameter and so on. However, civil engineers are having difficulty using nonlinear models that can apply material nonlinear properties due to difficulties in estimating ground property coefficients. In this study, the necessity of rational model selection was reviewed by comparing the results of seismic performance evaluation using the Mohr-Coulomb model, which civil engineers generally apply for numerical analysis of tunnels, and the HS Small strain Stiffness model, which can consider ground nonlinearity.