Effect of Residual Stress on Femoral Arterial Stress-Strain Behavior

Chandran, K.B.,Mun, J.H.,Chen, J.S.,Nagaraj, A.,McPherson, D.D. The Korean Society of Mechanical Engineers 2001 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.15 No.7

It is well established that arteries are subjected to residual stress. Due to the effect of residual stress, the arteries open to a horse-shoe shape when a longitudinal cut is made on an excised arterial segment. Previously, the residual stress has been quantified by the opening angle of the horse-shoe shape. We have employed a finite element analysis of the open arterial segment to restore the same to the original cylindrical shape and computed the circumferential strain as well as the stress distribution in the wall. In this study, the stress distribution in the femoral arteries of miniswine was computed with and without the residual stress for a range of transmural pressures. Our analysis showed that the residual stress has the effect of redistribution of the circumferential stresses between the intima and the adventitia under physiological loading. The redistribution of the stress with the inclusion of residual stress may be important in the studies on effect of wall stresses on the endothelial and vascular smooth muscle cells.

Shakedown analysis of a wind turbine gear considering strain-hardening and the initial residual stress

Haifeng He,Hua iju Liu,Caichao Zhu,Longhua Yuan 대한기계학회 2018 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.32 No.11

Under some heavy-duty conditions, the shakedown state may occur on gears such as those used in a megawatt wind turbine gearbox. The plastic deformation and the residual stress formed within the shakedown process further influence the contact behavior and the service life of the gear. The initial residual stress caused by the heat treatment of the case-hardening gear, together with the strain-hardening constitutive behavior of the material, have a combined effect on the shakedown state. A two-dimensional elastic-plastic contact numerical model was developed for a case-hardened wind turbine gear to study effects of the initial residual stress and the strain-hardening properties. Plastic strain and residual stress are calculated at each loading cycle without the consideration of the tooth friction. The initial yield limit and the hardening modulus of the material were obtained through a tension test on a universal tensile test machine. The initial residual stress distribution was measured with the X ray diffraction method and then embedded in the finite element model. The results show that strain-hardening behavior can significantly improve the shakedown performance, and the larger the hardening modulus is, the less the maximum plastic strain is at the final shakedown state. Initial residual compressive stress is helpful to improve the shakedown performance, while initial residual tensile stress has negative influence on the shakedown performance. As the normal load increases, the influence of the initial residual stress on the shakedown state becomes weakened.

다중충돌 쇼트피닝에서 변형률속도와 쇼트볼 경도가 잔류응력에 미치는 영향에 관한 연구

김태우(TAEWOO KIM),이영석(YOUNGSEOG LEE) 대한기계학회 2010 대한기계학회 춘추학술대회 Vol.2010 No.11

When a shot ball impacts with material, residual compress stress occurs. Improving fatigue strength of material with this residual compress stress is the purpose of shot peening process. Numerical study was performed to evaluate the effect of strain rate on the residual compressive stress. We calculated the residual compressive stress of shot peening multiple impact using ABAQUS with strain rate. Shot ball was deformable body. Material used in this study was AISI4340 steel. There were two method as follow. i) higher sensitivity of strain rate ii). lower sensitivity of strain rate. we compared residual compressive stress of two method. when sensitivity of strain rate increased, residual compressive stress is less. there are same material with yield stress, the sensitiveness of strain rate has a strong influence on residual compressive stress.

잔류응력의 영향을 고려한 용접부 내진 평가

김종성(Jong-Sung Kim),장현수(Hyun-Su Jang) 대한기계학회 2021 대한기계학회 춘추학술대회 Vol.2021 No.4

BDBE 와 같이 심각한 지진 하중 하에서 원자력 발전소의 안전성을 검증하기 위해 APR-1400의 가압기와 고온관을 연결하는 밀림배관의 탄소성 유한요소 해석을 수행하였다 [1~2]. 이전 연구에서 지진에 중요한 위치인 가압기 노즐과 핫레그 노즐의 용접부 모사할 때 3case (용접부의 기하학적 형상을 고려하지 않은 경우, 기하학적 형상과 용접 물성을 고려한 경우, 잔류응력을 고려한 경우)에 대해서 지진해석을 수행하였다. 잔류응력을 고려하여 지진해석을 수행한 경우, 누적소성변형률과 등가소성변형률이 다른 경우에 비해 상당히 크게 발생하였다. 잔류응력 해석시 용접부가 융착되는 시간은 매우 짧다. 따라서 본 연구에서는 잔류응력을 고려한 지진해석의 누적소성변형률과 등가소성변형률을 좀 더 현실적으로 시뮬레이션 하기 위해서 어닐링 온도를 고려하여 잔류응력 해석을 수행하였다. 용접 재료인 ER308l의 물성은 주기적인 테스트 결과를 가지고 있지 않기 때문에, 간단한 인장 실험의 결과를 통해 샤보세 경화 모델을 정의하였다. 또한 분석 변수(예: 지진 변위 시간 이력)는 이전 연구에 사용하였던 것과 동일한 값을 사용하였다. 잔류응력을 고려한 지진 해석시 핫레그 노즐과 용접부 사이에서 취약부위가 발생하였다. 취약 부위에 대해 ASME code [3]의 변형률 기반 허용 기준 평가를 수행하였고, 무결성이 만족되었다. 어닐링 온도는 잔류응력 해석에 의해 발생한 누적소성변형률과 등가소성변형률에 상당한 영향을 미치고, 그에 따라 잔류응력을 고려한 용접부의 내진 평가 시 여유도에 영향을 미치는 것을 확인하였다. To verify the safety of nuclear power plants under severe seismic loads, such as BDBE, the finite element elastic-plastic analysis of the surge line system connecting the pressurizer and the hot-leg of APR-1400 was conducted. In the previous study, seismic analysis was conducted on 3 cases (not considering geometry shape of weld, considering geometry shape of welds and material properties of welds, considering welding residual stress) when simulating welds in pressurizer nozzles and hot-leg nozzles, which are critical location for earthquakes. When seismic analysis was conducted in consideration of welding residual stress, accumulated plastic strain and equivalent plastic strain were significantly larger than those of other cases. When conducting welding residual stress, the time for weld to fuse is very short. Therefore, in this study, welding residual stress analysis was conducted considering annealing temperature to more realistic simulation of accumulated plastic strain and equivalent plastic strain of seismic analysis considering welding residual stress. The welding material was used as ER308l instead of TP316 which was previously used material. Since the properties of ER308l do not have cyclic test results, define the Chaboche hardening model through the results of a simple tensile experiment. Furthermore, the analytical variables (such as seismic displacement time history) used the same values as those used in previous study. The seismic analysis was conducted considering the effects of welding residual stress, and vulnerable point occurred between hot-leg nozzles and welds. The integrity was satisfied by performing strain-based acceptance criteria evaluation of ASME code. The annealing temperature was confirmed to have a significant effect on the accumulated plastic strain and the equivalent plastic strain caused by welding residual stress analysis. Accordingly, it was confirmed that the seismic evaluation of welds considering welding residual stress affects the margin.

Experimental and numerical studies of stress/strain characteristics in riveted aircraft lap joints

Chao Zeng,Wei Tian,Xiang Yao Liu,Jiu Tian Xue 대한기계학회 2019 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.33 No.7

The fatigue property of riveted lap joint is greatly related to the riveting-induced residual stress, especially the stress distribution on the faying surface. However, an accurate study of the residual stress characteristics in the riveted sheet could be very difficult. In this paper, both numerical and experimental investigations were carried out on the stress/strain characteristics in riveted aircraft lap joints. A special specimen was designed for the test of strain variations on the faying surface of the sheet by microstrain gages. For the numerical simulation, the rivet squeezing process was analyzed using the explicit dynamic finite element (FE) method, whilst a general static FE analysis was employed for the elastic springback after the squeeze force was removed. A comparison of the strain variations between the experimental results and FE simulations shows a general good agreement, although there may be some difference for points measured near the hole surface. The FE analysis reveals that both compressive and tensile residual stresses could be introduced in the riveted sheet. Massive compressive residual stress can be created in the near-surface layer of the hole. However, the stress level is not always increased with increasing the squeeze force, and so is the improvement of fatigue life observed. Further study is still necessary to account for the fatigue life decreasing effect caused by a high squeeze force.

Numerical Simulation and Measurement of Welding Residual Stresses in Orthotropic Steel Decks Stiffened with U-Shaped Ribs

Ying Gu,Yadong Li,Zihao Zhou,Songbo Ren,Chao Kong 한국강구조학회 2020 International Journal of Steel Structures Vol.20 No.3

This study aims to investigate the magnitude and distribution of welding residual stresses in orthotropic steel decks stiff ened with U-shaped ribs. Numerical simulation of the welding residual stresses is performed using the thermal elastic–plastic fi nite element method. The residual stresses are subsequently measured using the hole-drilling strain-gage method. Based on the results of this study, it can be determined that: (1) The longitudinal welding residual stresses ( σ z ) in the weld zones are tensile stresses, where the peak value exceeds the minimum yield strength ( f yl ); however, relatively low compressive stresses exist in the areas located far away from the welds; (2) The stress gradient in the weld zone is steep, and the widths of the areas experiencing tensile stress are narrow; (3) In the case of the upper surface of the deck, the weld that is fi rst deposited has the highest peak stress, while similar stresses are determined for the remaining welds. In the case of the lower surface of the deck, the peak stress in the weld zones is greater than that on the upper surface; (4) In the case of the weld zone of the U-shaped ribs, the tensile stresses reach up to 1.15 f yl ; however, at locations a short distance away from the welds, the σ z varies from tensile to compressive, and fi nally transforms into a small tensile stress at the base of the U-shaped ribs. In addition, the simulated and measured σ z are compared, and the deviation between them is analyzed.

국소 압흔변형률에 미치는 표면 잔류응력 영향 분석

이윤희 ( Yun Hee Lee ),박종서 ( Jong Seo Park ),김용일 ( Yong Il Kim ),허용학 ( Yong Hak Huh ) 대한금속재료학회(구 대한금속학회) 2015 대한금속·재료학회지 Vol.53 No.2

Berkovich pyramidal indents formed on stressed metallic glass samples were observed with an atomic force microscope. Three-dimensional morphologies of the remnant impressions with pile-up lobes were approximated as six-sided pyramids and their indent strains were estimated according to Milman’s strain definition. Under a residual stress state, it was possible to formulate the indent strain using the sum of the elastic indentation stresses and the residual stress parallel to the sample surface. Finally, the residual stress can be expressed by the multiple of the stress-dependent change in the indent strain and the Young``s modulus of the indented sample. The predicted stresses estimated from the pyramidal indent morphologies were comparable to the applied stresses except in a high stress regime. This deviating phenomenon under high tensile stress is discussed and found to be due to exaggerated plastic deformation and image scatter due to mild pile-ups.

다중충돌 쇼트피닝에서 변형률 속도와 소재 경도가 잔류응력에 미치는 영향에 관한 연구

김태우(Tae Woo Kim),양조예(Zhao Rui Yang),나두현(Doo Hyun Na),이영석(Youngseog Lee) 대한기계학회 2011 大韓機械學會論文集A Vol.35 No.11

쇼트피닝 공정은 쇼트볼이 소재에 충돌을 일으킬 때 생기는 압축잔류응력에 의해 소재의 피로 강도를 향상 시키는데 그 목적이 있다. 본 연구는 변형률 속도 민감도 변화가 압축잔류응력에 미치는 영향을 분석하기 위해서 수행되었다. 본 연구자는 변형률 속도 민감도의 영향을 고려한 쇼트피닝 다중 충돌을 ABAQUS 6.9-1 를 사용하여 모사하였다. 사용된 소재는 AISI 4340 강종이다. 본 연구자는 변형률 속도 민감성이 높은 재료와 낮은 재료를 비교하였다. 결과적으로 변형률 속도 민감성이 증가하면 압축잔류응력은 감소하였다. 또한 경도가 낮은 소재의 압축잔류응력이 경도가 높은 소재보다 더 크게 발생하였다. Shot ball impacts to materials cause residual compressive stress on their surfaces. Improving the fatigue strength of a material that has this residual compress stress is the purpose of the shot peening process. A numerical study was performed to evaluate the effect of the strain rate sensitivity and hardness of the shot ball on the residual compressive stress. We calculated the residual compressive stress due to multiple impact shot peening using ABAQUS 6.9-1. AISI 4340 steel was the material used in this study. We compared the effects of high strain rate sensitivities and low strain rate sensitivities and found that when the material’s sensitivity to the strain rate increased, the residual compressive stress decreased. In addition, the residual compressive stress of low-hardness material is higher than that of high-hardness material.

Residual stress measurement on propellant tank of 2219 aluminum alloy and study on its weak spot

Chaoqun Huang,Huan Li,Jianxiong Li,Chuanguang Luo,Yanbing Ni 대한기계학회 2017 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.31 No.5

This paper presented residual stress measurement on two circumferential Variable polarity plasma arc welding (VPPAW) joints and one circular closed Friction stir welding (FSW) joint on the propellant tank of 2219 aluminum alloy using the indentation strain-gauge method. Quite large tensile residual stresses were attached to the center and inner areas of the circular closed FSW joint. There were very large tensile stresses in some points of the two circumferential VPPAW joints, among these points, the maximum value was +253 MPa, which was about 63 % of the yield strength of 410 MPa measured in the base material. In addition, the peak of compressive residual stress was about -160 MPa. Above all, there were two typical peaks of residual stress in the circumferential VPPAW joints, one was located in the middle part while the other one was near the start/end position of the joints. Combining the result of residual stress measurement with the characteristics of the tank structure, it can be concluded that circular closed FSW joint around the flange was a weak spot on the propellant tank. And the most vulnerable point on the circular closed FSW joint has also been found.

Effects of Initial Condition of Steel Plate on Welding Deformation and Residual Stress due to Welding

PARK. J. U,LEE H. W 대한기계학회 2007 JOURNAL OF MECHANICAL SCIENCE AND TECHNOLOGY Vol.21 No.3

The effects of initial deflection and initial residual stress in steel plate on the out-of-plane deformation and residual stress due to welding are investigated from analysis results of thermal elastic-plastic FEM modeling with large deflection theory. Initial residual stress due to plate forming has very little effects on welding deformation and welding residual stress. For initial deflection, with concave profile (Type Ⅰ), welding induced deformation has the same type as initial deflection and its magnitudes are small. When initial deflection is in the direction parallel to weld line (Type Ⅱ), welding induced deformation has minor variations. When initial deflection is bended in the direction normal to weld line (Type Ⅲ), welding deformation was largely generated along the width direction of the steel plate. On the other hand, the variation in type of initial deflection does not affect the residual stress and plastic strain.