• 제목, 요약, 키워드: hardening

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경화모델에 따른 고강도강판 S-rail 성형공정에서의 스프링백 모드 비교 (Comparison of Springback Modes in the Stamping Process of an S-rail with HSS according to the Hardening Model)

  • 최병현;이진우;김세호;이명규;김흥규
    • 소성가공
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    • v.22 no.1
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    • pp.30-35
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    • 2013
  • In this study, springback amounts of an S-rail are quantitatively compared according to the hardening model using a finite element simulation for the stamping process with high strength steels. For comparison of the hardening models, two types of hardening models were investigated. The two models were isotropic hardening and kinematic hardening. For the analysis with kinematic hardening, the Yoshida-Uemori model was selected. Five kinds of springback modes were measured at designated sections and a comparison was made between the experiment and the analyses with two types of hardening models. The analysis results show that the springback in the flange and the wall curl are predicted more accurately with a kinematic hardening model.

조선 해양 구조물용 강재의 소성 및 파단 특성 I: 변형률 경화 및 변형률 속도 경화의 이론적 배경 (Plasticity and Fracture Behaviors of Marine Structural Steel, Part I: Theoretical Backgrounds of Strain Hardening and Rate Hardening)

  • 정준모;심천식;김경수
    • 한국해양공학회지
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    • v.25 no.2
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    • pp.134-144
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    • 2011
  • In this paper, the global study trends for material behaviors are investigated regarding the static and dynamic hardenings and final fractures of marine structural steels. In particular, after reviewing all of the papers published at the 4th and 5th ICCGS (International Conference on Collision and Grounding of Ship), the used hardening and fracture properties are summarized, explicitly presenting the material properties. Although some studies have attempted to employ new plasticity and fracture models, it is obvious that most still employed an ideal hardening rule such as perfect plastic or linear hardening and a simple shear fracture criterion with an assumed value of failure strain. HSE (2001) presented pioneering study results regarding the temperature dependency of material strain hardening at various levels of temperature, but did not show strain rate hardening at intermediate or high strain rate ranges. Nemat-Nasser and Guo (2003) carried out fully coupled tests for DH-36 steel: strain hardening, strain rate hardening, and temperature hardening and softening at multiple steps of strain rates and temperatures. The main goal of this paper is to provide the theoretical background for strain and strain rate hardening. In addition, it presents the procedure and methodology needed to derive the material constants for the static hardening constitutive equations of Ludwik, Hollomon, Swift, and Ramberg-Osgood and for the dynamic hardening constitutive equations of power from Cowper-Symonds and Johnson-Cook.

진공압밀 배수공법에 의한 Hardening Zone에 대한 연구 (A Study on Hardening Zone by Vacuum Consolidation Drainage Method)

  • 정연인;김희중;장준호
    • 한국구조물진단유지관리공학회 논문집
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    • v.8 no.3
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    • pp.197-205
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    • 2004
  • 연약지반 개량을 위해 진공압밀공법을 적용할 경우 발생되는 Hardening Zone의 범위와 진공압 세기의 관계를 연구하였다. 이를 위하여 단위 셀 형식의 시험기를 제작하여 국내의 대표적 준설매립공사지역인 광양, 부산, 목포에서 채취한 고함수비 상태에서의 준설점성토에 대해 각각 함수비와 콘저항치수를 측정하여 진공압의 변화에 따른 Hardening Zone의 변화를 파악하였다. 높은 진공압상태에서는 배수재의 막힘현상과 배수재 부근에서 빠르게 생성되는 Hardening Zone 등으로 인하여 배수층으로의 간극수의 흐름이 방해되어 낮은 진공압상태에서 보다 Hardening zone의 범위가 커지지는 않았다.

표준 인장시험과 반복하중 C(T) 시험을 이용한 균열해석에서의 Chaboche 복합경화 모델 결정법 (Determination of Chaboche Cyclic Combined Hardening Model for Cracked Component Analysis Using Tensile and Cyclic C(T) Test Data)

  • 황진하;김훈태;류호완;김윤재;김진원;권형도
    • 한국압력기기공학회 논문집
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    • v.15 no.2
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    • pp.31-39
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    • 2019
  • Cracked component analysis is needed for structural integrity analysis under seismic loading. Under large amplitude cyclic loading conditions, the change in material properties can be complex, depending on the magnitude of plastic strain. Therefore the cracked component analysis under cyclic loading should consider appropriate cyclic hardening model. This study introduces a procedure for determining an appropriate cyclic hardening model for cracked component analysis. The test material was nuclear-grade TP316 stainless steel. The material cyclic hardening was simulated using the Chaboche combined hardening model. The kinematic hardening model was determined from standard tensile test to cover the high and wide strain range. The isotropic hardening model was determined by simulating C(T) test under cyclic loading using ABAQUS debonding analysis. The suitability of the material hardening model was verified by comparing load-displacement curves of cyclic C(T) tests under different load ratios.

변형률 독립 강소성 구성 방정식에서의 이중 후방 응력 경화 모델 (Two Back Stress Hardening Models in Rate Independent Rigid Plasticity)

  • 윤수진
    • 소성가공
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    • v.14 no.4
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    • pp.327-337
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    • 2005
  • In the present work, the two back stress kinematic hardening models are proposed by combining Armstrong-Frederick, Phillips and Ziegler's hardening rules. Simple combination of hardening rules using simple rule of mixtures results in various evolutions of the kinematic hardening parameter. Using the combined hardening models the ultimate back stress fur the present models is also derived. The stress rate is co-rotated with respect to the spin of substructure due to the assumption of kinematic hardening rule in finite deformation regime. The work piece under consideration is assumed to consist of the elastic and the rigid plastic deformation zone. Then, the J2 deformation theory is facilitated to characterize the plastic deformation behavior under various loading conditions. The plastic deformation localization behaviors strongly depend on the constitutive description namely back stress evolution and its hardening parameters. Then, the analysis for Swift's effects under the fixed boundaries in axial directions is carried out using simple shear deformation.

레이저 표면경화공정에서 신경회로망을 이용한 경화층깊이의 측정 (Estimation of hardening depth using neural network in LASER surface hardening process)

  • 박영준;우현구;조형석;한유희
    • 제어로봇시스템학회:학술대회논문집
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    • pp.212-217
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    • 1993
  • In this paper, the hardening depth in Laser surface hardening process is estimated using a multilayered neural network. Input data of the neural network are surface temperature of five points, power and travelling speed of Laser beam. A FDM(finite difference method) is used for modeling the Laser surface hardening process. This model is used to obtain the network's training data sample and to evaluate the performance of the neural network estimator. The simulational results showed that the proposed scheme can be used to estimate the hardening depth on real time.

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Hardening of Steel Sheets with Orthotropy Axes Rotations and Kinematic Hardening

  • Hahm, Ju-Hee;Kim, Kwon-Hee;Yin, Jung-Je
    • International Journal of Precision Engineering and Manufacturing
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    • v.1 no.1
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    • pp.91-97
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    • 2000
  • Anisotropic work hardening of cold rolled low carbon steel sheets is studied. The experiments consist of two stage tensile prestraining and tensile tests. At the first prestraining, steel sheets are streteched along the rolling direction by 3% and 6% tensile strains. The second prestrains are at 0${\cric}$, 30${\cric}$, 60${\cric}$to the rolling directions by varying degrees. Tensile tests are performed on the specimens cut from the sheets after the two stage prestraining. A theoretical framework on anisotropic hardening is proposed which includes Hill's quadratic yield function, ziegler's kinematic hardening rule, and Kim and Yin's assumption on the rotation of orthotropy axes. The predicted variations of R-values with second stage tensile strain are compared with the experimental data.

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가공경화지수 및 변형율속도 경화지수의 변화가 마찰상수 결정에 미치는 영향 (Effects of Work-Hardening Exponent and Strain-Rate Hardening Exponent on the Determination of Friction Factor)

  • 박치용;양동열
    • 소성가공
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    • v.1 no.1
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    • pp.42-51
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    • 1992
  • The ring compression test has been widely employed as an experimental means to determine the friction factor. The calibration curves are obtained by the rigid-plastic finite element analysis for various work-hardening exponent and strain-rate hardening exponent. The effects of work-hardening exponent and strain-rate hardening exponent are thoroughly studied and discussed from the finite element computation. The change of friction factor during height reduction in ring compression is also discussed. Then, the method to estimate the change of friction factor during ring compression is proposed.

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중간온도 영역에서의 NiAl 단결정 이상 경화거동에 대한 연구 (Investigation of anomalous hardening in NiAl Single crystals at intermediate temperatures)

  • 양철호
    • 한국정밀공학회:학술대회논문집
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    • pp.1390-1393
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    • 2005
  • The hardening model based on the dislocation mechanics is employed to study the experimentally observed high tensile elongations of NiAl along the [110] orientation at intermediate temperatures. In the hardening model proposed, a mobility of dislocation is assumed to be restricted to glide through the slip plane by forest dislocation and thermally activated cross-slip event. Overall deformation behavior of NiAl was greatly influenced by temperature-dependent dislocation mobility that both experimental and simulated yield stresses decreased as temperature increased. The results of simulation showed anomalous hardening behaviors analogous to those of experiment at certain circumstances. This behavior occurred due to the hardening contributions generated by cross-slip events that disable the dislocation motion in the primary slip systems. By comparing simulation results with experiments, it is confirmed that the proposed hardening model can represent anomalous tensile elongations due to the hardening by forest dislocations and cross-slip events.

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얇은 판상의 석출을 포함한 결정의 초기항복응력 이방성 및 경화거동에 관한 모델링 (Modeling the Anisotropy of Initial Yield Strength and Hardening Behavior of Crystals with Thin Platelet Precipitates)

  • 김준형;한정석;강태진;정관수
    • 소성가공
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    • v.14 no.6
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    • pp.496-501
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    • 2005
  • Precipitates, present in most commercial alloys, can have a strong influence on strength and hardening behavior of a single crystal. The effect of thin precipitates on the anisotropy of initial slip resistance and hardening behavior of crystals is modeled in this article. For the convenience of the computational derivation and implementation, the material formulation is given in the unrelated intermediate configuration mapped by the plastic part of the deformation gradient. Material descriptions for the considered two phased aggregates consisting in lattice hardening as well as isotropic hardening and kinematic hardening are suggested. Numerical simulations of various loading cases are presented to discuss and assess the performance of the suggested model. From the results of the numerical simulation, it is found that the suggested model represents the initial plastic anisotropy at least qualitatively well and that it has an improved representation of various characteristic hardening behaviors in comparison with conventional hardening descriptions where the precipitate structure is not reflected.