• 제목/요약/키워드: Plastic strain energy

검색결과 216건 처리시간 0.028초

전자기 성형에서의 변형률 속도 효과 해석 (Analysis of the Strain Rate Effect in Electro-Magnetic Forming)

  • 곽신웅;신효철;이종수
    • 대한기계학회논문집
    • /
    • 제14권5호
    • /
    • pp.1043-1058
    • /
    • 1990
  • 본 연구에서는 전자기 성형법에 의한 원통형상의 가공재의 자유 확관성형 가 공에 대해서 유한요소해석법을 이용한 변형 및 응력해석을 수행하였다. 탄소성 재료 모형을 확장하여 변형 경화율이 변형률 및 변형률 속도의 지배를 받는 변형률 속도 종 속 탄소성 재료 모형을 도입하였고, 1차 제하 이후까지 포함하여 고속 성형시 변형률 속도 효과에 의해 발생하는 현상들에 대해서 연구하였다.결과의 비교 및 논의를 위 하여, 해석대상과 성형조건, 그리고 가공재에 작용하는 자기압력은 Suzuki의 것과 동 일한 것을 사용하였다.

고질소강 오스테나이트계 스테인레스강의 압축변형특성 (Deformation Characteristic by Compression in High-Nitrogen Austenitic Stainless Steel)

  • 이종욱;김동수;김병구;이명열
    • 한국소성가공학회:학술대회논문집
    • /
    • 한국소성가공학회 2007년도 추계학술대회 논문집
    • /
    • pp.139-141
    • /
    • 2007
  • Compression tests were carried out to investigate morphologies of compressed specimen, deformation microstructure and stress-strain relation in high-nitrogen austenite stainless steel. Tests were performed under a wide range of temperature and, with true strain rates up to $\dot{\varepsilon}$ =0.05, 0.1, 0.5 and $1.0s^{-1}$. The activation energy of loading force was equal to plastic deformation energy within the temperature range of $900^{\circ}C$ to $1250^{\circ}C$. Dynamically recrystallized grain size decreased with an increasing strain rate and temperature. Flow stresses and deformation microstructures, were used to quantify the critical strain rate and recrystallized grain size. The grain size versus strain rate-temperature map obtained in the study was in good agreement with the deformation microstructures of compressed specimens.

  • PDF

Rheological Aspect of the Plastic Energy Dissipation

  • Kim, Myung-Ho
    • 한국유변학회:학술대회논문집
    • /
    • 한국유변학회 2003년도 춘계학술발표회 논문집
    • /
    • pp.93-98
    • /
    • 2003
  • In this paper, the main emphasis and focus will be to study and illuminate the nature of Plastic Energy Dissipation (PED) in variety of polymers. This PED term represents the heat generated during the irreversible deformation of a polymer solid. A series of experiments for various polymers have been conducted in direct measurement method and indirect evaluation method - the incremental strain stress relaxation ((ISSR) method. The experimental evidence to relate the stress relaxation and the sensible temperature rise were revealed by the series of direct method experiments.

  • PDF

조선 해양 구조물용 강재의 소성 및 파단 특성 III: 파단 변형률에 관한 실험적 연구 (Plasticity and Fracture Behaviors of Marine Structural Steel, Part III: Experimental Study on Failure Strain)

  • 정준모;심천식;김경수
    • 한국해양공학회지
    • /
    • 제25권3호
    • /
    • pp.53-65
    • /
    • 2011
  • This is the third of several companion papers dealing with the derivation of material constants for ductile failure criteria under hydrostatic stress. It was observed that the ultimate engineering stresses and elongations at fracture from tensile tests for round specimens with various notch radii tended to increase and decrease, respectively, because of the stress triaxiality. The engineering stress curves from tests are compared with numerical simulation results, and it is proved that the curves from the two approaches very closely coincide. Failure strains are obtained from the equivalent plastic strain histories from numerical simulations at the time when the experimental engineering stress drops suddenly. After introducing the new concept of average stress triaxiality and accumulated average strain energy, the material constants of the Johnson-Cook failure criterion for critical energies of 100%, 50%, and 15% are presented. The experimental results obtained for EH-36 steel were in relatively good agreement with the 100% critical energy, whereas the literature states that aluminum fits with a 15% critical energy. Therefore, it is expected that a unified failure criterion for critical energy, which is available for most kinds of ductile materials, can be provided according to the used materials.

Theoretical Considerations on Effect of Environments on Strain Hardening

  • Lee, Byoung-Whie
    • Nuclear Engineering and Technology
    • /
    • 제3권1호
    • /
    • pp.21-31
    • /
    • 1971
  • 금속의 소성변형에 필요한 일의 일부는 전표면자유에너지 (Total Surface Free Energy)의 변화에 소모된다. 전표면자유에너지 변화는 비표면 자유에너지 (Specific Surface Free Energy)에 의해 변화하며 비표면자유에너지는 분위기에 따라 달라 진다. 열역학적규명, 체적불변율과 흡착으로 인한 두 개의 판이하게 다른 강화 혹은 약화를 초래하는 전위(Dislocation) 상호작용기구를 기반으로 금속의 소성변형으로 인한 가공경화, 응력 및 에너지에 미치는 분위기의 영향을 이론식으로 도출했다. 이론식은 진공중금속표면장력 (${\gamma}$$_{s}$), 개면장력 (${\gamma}$$_{se}$ ), 포면전위밀도($\rho$$_{s}$), 내부전위 밀도($\rho$$_{i}$)와 표면노출율(f)의 함수로 표시할 수 있었다. 이론식을 이용하여 각기 다른 분위기내에서의 금속의 기계특성을 예측 비교해봤다.다.다.

  • PDF

3 차원 유한요소해석을 이용한 자유경계조건에서의 두께 1.7 mm DP780 고강도 강판의 저 속 충격 특성 분석 (A Study on Low Velocity Impact Characteristics of DP 780 High Strength Steel Sheet with Thickness of 1.7 mm on the Free Boundary Condition Using Three-Dimensional Finite Element Analysis)

  • 안동규;남경흠;성대용;양동열;임지호
    • 한국정밀공학회지
    • /
    • 제27권11호
    • /
    • pp.46-56
    • /
    • 2010
  • The present research works investigated into the low velocity impact characteristics of DP 780 high strength steel sheet with 1.7 mm in thickness subjected to free boundary condition using three-dimensional finite element analysis. Finite element analysis was carried out via ABAQUS explicit code. Hyper-elastic model and the damping factor were introduced to improve an accuracy of the FE analysis. An appropriate FE model was obtained via the comparison of the results of the FE analyses and those of the impact tests. The influence of the impact energy and nose diameter of the impact head on the force-deflection curves, impact time, absorption characteristics of the impact energy, deformation behaviours, and stress-strain distributions was quantitatively examined using the results of FE analysis. The results of the FE analysis showed that the absorption rate of impact energy lies in the range of the 70.7-77.5 %. In addition, it was noted that the absorption rate of impact energy decreases when the impact energy increases and the nose diameter of the impact head decreases. The local deformation of the impacted region was rapidly increased when the impact energy was larger than 76.2 J and the nose diameter was 20 mm. A critical impact energy, which occur the instability of the DP780, was estimated using the relationship between the plastic strain and the impact energy. Finally, characteristics of the plastic energy dissipation and the strain energy density were discussed.

전변형률 에너지밀도를 이용한 고강도 저 합금강의 저주기 피로수명 예측 (Low Cycle Fatigue Life Prediction of HSLA Steel Using Total Strain Energy Density)

  • 김재훈;김덕희
    • 한국정밀공학회지
    • /
    • 제19권6호
    • /
    • pp.166-175
    • /
    • 2002
  • Low cycle fatigue tests are performed on the HSLA steel that be developed for a submarine material. The relation between strain energy density and numbers of cycles to failure is examined in order to predict the low cycle fatigue life of HSLA steel. The cyclic properties are determined by a least square fit techniques. The life predicted by the strain energy method is found to coincide with experimental data and results obtained from the Coffin-Manson method. Also the cyclic behavior of HSLA steel is characterized by cyclic softening with increasing number of cycle at room temperature. Especially, low cycle fatigue characteristics and microstructural changes of HSLA steel are investigated according to changing tempering temperatures. In the case of HSLA steel, the $\varepsilon$-Cu is farmed in $550^{\circ}C$ of tempering temperature and enhances the low cycle fatigue properties.

고인성 종이의 탄성-소성 파괴의 에너지 판단기준 (The Energy Criteria for Elastic-Plastic Fracture in Tough Paper)

  • 박종문
    • Journal of the Korean Wood Science and Technology
    • /
    • 제24권4호
    • /
    • pp.64-73
    • /
    • 1996
  • 고인성 종이의 탄성-소성 파괴를 파괴역학을 이용하여 분석하였다. 탄성-소성 물질의 파괴에 있어서 균열이 언제 진행되기 시작하는지 이론적 판단 기준을 유도하고, mode I 파괴를 linear image strain analysis(LISA)로 관찰한 후, 파괴역학 변수들을 계산하였다. 크랙(crack)이 있는 물질에 외부하중이 작용할 때 변형율 에너지 발산 속도(strain energy release rate)가 그 물질이 견딜 수 있는 파괴저항(fracture resistance)에 도달하면 안정적인 파괴가 진행된다. 이를 이용하여 크랙의 초기 진행시 결점주위의 응력, 파괴저항, 크랙 진행거리, 기하인자(geometry factor) 등을 구하였다. 이 변수들은 종이의 파괴역학적 특성을 정량적으로 나타내므로 유용하게 활용될 수 있을 것이다.

  • PDF

Round robin analysis to investigate sensitivity of analysis results to finite element elastic-plastic analysis variables for nuclear safety class 1 components under severe seismic load

  • Kim, Jun-Young;Lee, Jong Min;Park, Jun Geun;Kim, Jong-Sung;Cho, Min Ki;Ahn, Sang Won;Koo, Gyeong-Hoi;Lee, Bong Hee;Huh, Nam-Su;Kim, Yun-Jae;Kim, Jong-In;Nam, Il-Kwun
    • Nuclear Engineering and Technology
    • /
    • 제54권1호
    • /
    • pp.343-356
    • /
    • 2022
  • As a part of round robin analysis to develop a finite element elastic-plastic seismic analysis procedure for nuclear safety class 1 components, a series of parametric analyses was carried out on the simulated pressurizer surge line system model to investigate sensitivity of the analysis results to finite element analysis variables. The analysis on the surge line system model considered dynamic effect due to the seismic load corresponding to PGA 0.6 g and elastic-plastic material behavior based on the Chaboche combined hardening model. From the parametric analysis results, it was found that strains such as accumulated equivalent plastic strain and equivalent plastic strain are more sensitive to the analysis variables than von Mises effect stress. The parametric analysis results also identified that finite element density and ovalization option in the elbow elements have more significant effect on the analysis results than the other variables.

Plastic energy approach prediction of fatigue crack growth

  • Maachou, Sofiane;Boulenouar, Abdelkader;Benguediab, Mohamed;Mazari, Mohamed;Ranganathan, Narayanaswami
    • Structural Engineering and Mechanics
    • /
    • 제59권5호
    • /
    • pp.885-899
    • /
    • 2016
  • The energy-based approach to predict the fatigue crack growth behavior under constant and variable amplitude loading (VAL) of the aluminum alloy 2024 T351 has been investigated and detailed analyses discussed. Firstly, the plastic strain energy was determined per cycle for different block load tests. The relationship between the crack advance and hysteretic energy dissipated per block can be represented by a power law. Then, an analytical model to estimate the lifetime for each spectrum is proposed. The results obtained are compared with the experimentally measured results and the models proposed by Klingbeil's model and Tracey's model. The evolution of the hysteretic energy dissipated per block is shown similar with that observed under constant amplitude loading.