• 제목/요약/키워드: restraint stress model

검색결과 65건 처리시간 0.028초

소성거동을 고려한 원주방향 관통균열 열림에 미치는 압력유기굽힘의 구속효과 평가 모델 (Evaluation Model for Restraint Effect of Pressure Induced Bending on the Circumferential Through-Wall Crack Opening Considering Plastic Behavior)

  • 김진원
    • 대한기계학회논문집A
    • /
    • 제30권9호
    • /
    • pp.1134-1141
    • /
    • 2006
  • This paper presents the model for evaluating restraint effect of pressure induced bending (PIB) on the circumferential through-wall crack opening displacement (COD), which considers plastic behavior of crack. This study performed three-dimensional elastic-plastic finite element (FE) analyses for different crack angle, restraint length, pipe geometry, stress level, and material conditions, and evaluated the influence of each parameter on the PIB restraint effect on COD. Based on these evaluations and additional perfectly-plastic FE analyses, a closed-form model to evaluate the restraint effect of PIB on the plastic crack opening of circumferential through-wall crack, was proposed as functions of crack angle, restraint length, radius to thickness ratio, axial stress corresponding to an internal pressure, and normalized COD evaluated from linear-elastic crack opening condition.

Evaluation of Models for Estimating Shrinkage Stress in Patch Repair System

  • Kristiawan, Stefanus A.
    • International Journal of Concrete Structures and Materials
    • /
    • 제6권4호
    • /
    • pp.221-230
    • /
    • 2012
  • Cracking of repair material due to restraint of shrinkage could hinder the intended extension of serviceability of repaired concrete structure. The availability of model to predict shrinkage stress under restraint condition will be useful to assess whether repair material with particular deformation properties is resistance to cracking or not. The accuracy in the prediction will depend upon reliability of the model, input parameters, testing methods used to characterize the input parameters, etc. This paper reviews a variety of models to predict shrinkage stress in patch repair system. Effect of creep and composite action to release shrinkage stress in the patch repair system are quantified and discussed. Accuracy of the models is examined by comparing predicted and measured shrinkage stress. Simplified model to estimate shrinkage stress is proposed which requires only shrinkage property of repair material as an input parameter.

Repeated restraint stress promotes hippocampal neuronal cell ciliogenesis and proliferation in mice

  • Lee, Kyounghye;Ko, Hyuk Wan
    • Laboraroty Animal Research
    • /
    • 제34권4호
    • /
    • pp.203-210
    • /
    • 2018
  • Stress severely disturbs physiological and mental homeostasis which includes adult neurogenesis in hippocampus. Neurogenesis in hippocampus is a key feature to adapt to environmental changes and highly regulated by multiple cellular signaling pathways. The primary cilium is a cellular organelle, which acts as a signaling center during development and neurogenesis in adult mice. However, it is not clear how the primary cilia are involved in the process of restraint (RST) stress response. Using a mouse model, we examined the role of primary cilia in repeated and acute RST stress response. Interestingly, RST stress increased the number of ciliated cells in the adult hippocampal dentate gyrus (DG). In our RST model, cell proliferation in the DG also increased in a time-dependent manner. Moreover, the analysis of ciliated cells in the hippocampal DG with cell type markers indicated that cells that were ciliated in response to acute RST stress are neurons. Taken together, these findings suggest that RST stress response is closely associated with an increase in the number of ciliated neurons and leads to an increase in cell proliferation.

EVALUATION MODEL FOR RESTRAINT EFFECT OF PRESSURE INDUCED BENDING ON THE PLASTIC CRACK OPENING OF A CIRCUMFERENTIAL THROUGH-WALL CRACK

  • Kim, Jin-Weon
    • Nuclear Engineering and Technology
    • /
    • 제39권1호
    • /
    • pp.75-84
    • /
    • 2007
  • This paper presents a closed-form model for evaluating the restraint effect of pressure induced bending on the opening of a circumferential through-wall crack, which is considered plastic deformation behavior. Three-dimensional finite element analyses with different crack lengths, restraint conditions, pipe geometries, magnitudes of internal pressure, and tensile properties were used to investigate the influence of each parameter on the pressure-induced bending restraint on the crack opening displacement. From these investigations, an analytical model based on elastic-perfectly plastic material was developed in terms of the crack length, symmetric restraint length, mean radius to thickness ratio, axial stress corresponding to the internal pressure, and normalized crack opening displacement evaluated from a linear-elastic crack opening condition. Finite element analyses results demonstrate that the proposed analytical model reliably estimated the restraint effect of pressure-induced bending on the plastic crack opening of a circumferential through-wall crack and properly reflected the dependence on each parameter within the range over which the analytical expression was derived.

튜브 용접부의 용접변형 및 잔류응력에 관한 연구 (A Study on Welding Distortion and Residual Stress for Tubular Welded Joint)

  • 진형국;신상범;이동주;박동환
    • Journal of Welding and Joining
    • /
    • 제30권5호
    • /
    • pp.51-56
    • /
    • 2012
  • The purpose of this study is to evaluate the distortion and the residual stress of GTA tubular welds between tube and head. In order to do it, the heat input model for GTA welding process was first developed by experiment and FE analyses. The welding distortion and the residual stress distribution of the tubular welds according to welding pass and various restraint degrees were evaluated by using FEA with the heat input model. From FEA results, it was found that the residual stress and the radial distortion at the weld toe of tube part decrease with a decrease in the number of welding pass. However, the maximum residual stresses in each direction of tubular welds are almost constant regardless of the external restraint degree. It was mainly due to the high internal restraint of the welds.

The Anti-apoptotic Effect of Ghrelin on Restraint Stress-Induced Thymus Atrophy in Mice

  • Jun Ho Lee;Tae-Jin Kim;Jie Wan Kim;Jeong Seon Yoon;Hyuk Soon Kim;Kyung-Mi Lee
    • IMMUNE NETWORK
    • /
    • 제16권4호
    • /
    • pp.242-248
    • /
    • 2016
  • Thymic atrophy is a complication that results from exposure to many environmental stressors, disease treatments, and microbial challenges. Such acute stress-associated thymic loss can have a dramatic impact on the host's ability to replenish the necessary naïve T cell output to reconstitute the peripheral T cell numbers and repertoire to respond to new antigenic challenges. We have previously reported that treatment with the orexigenic hormone ghrelin results in an increase in the number and proliferation of thymocytes after dexamethasone challenge, suggesting a role for ghrelin in restraint stress-induced thymic involution and cell apoptosis and its potential use as a thymostimulatory agent. In an effort to understand how ghrelin suppresses thymic T cell apoptosis, we have examined the various signaling pathways induced by receptor-specific ghrelin stimulation using a restraint stress mouse model. In this model, stress-induced apoptosis in thymocytes was effectively blocked by ghrelin. Western blot analysis demonstrated that ghrelin prevents the cleavage of pro-apoptotic proteins such as Bim, Caspase-3, and PARP. In addition, ghrelin stimulation activates the Akt and Mitogen-activated protein kinases (MAPK) signaling pathways in a time/dose-dependent manner. Moreover, we also revealed the involvement of the FoxO3a pathway in the phosphorylation of Akt and ERK1/2. Together, these findings suggest that ghrelin inhibits apoptosis by modulating the stress-induced apoptotic signal pathway in the restraint-induced thymic apoptosis.

Shrinkage and crack characteristics of filling materials for precast member joint under various restraint conditions

  • Lim, Dong-Kyu;Choi, Myoung-Sung
    • Advances in concrete construction
    • /
    • 제14권2호
    • /
    • pp.139-151
    • /
    • 2022
  • Filling materials poured into precast member joint are subjected to restraint stress by the precast member and joint reinforcement. The induced stress will likely cause cracks at early ages and performance degradation of the entire structure. To prevent these issues and design reasonable joints, it is very important to analyze and evaluate the restrained shrinkage cracks of filling materials at various restraint conditions. In this study, a new time zero-that defines the shrinkage development time of a filling material-is proposed to calculate the accurate amount of shrinkage. The tensile stresses and strengths at different ages were compared through the ring test (AASHTO PP34) to evaluate the crack potential of the restrained filling materials at various restraint conditions. The mixture which contained an expansive additive and a shrinkage reducing agent exhibited high resistance to shrinkage cracking owing to the high-drying shrinkage compensation effect. The high-performance, fiber-reinforced cement composite, and ultra-high-performance, fiber-reinforced cement composite yielded very high resistance to shrinkage and cracking owing to the pull-out property of steel fibers. To this end, multiple nonlinear regression analyses were conducted based on the test results. Accordingly, a modified tensile stress equation that considered both the geometric shape of the specimen and the intrinsic properties of the material is proposed.

단백질과 단백질 가수분해물이 침수 속박 스트레스로 유도된 위 궤양 흰쥐의 질소대사에 미치는 영향 (Effect of Protein and Protein Hydrolysate on Nitrogen Metabolism in Rats with Gastric Ulcer Induced by Restraint and Water-Immersion Stress)

  • 김창임
    • Journal of Nutrition and Health
    • /
    • 제28권4호
    • /
    • pp.291-297
    • /
    • 1995
  • This study aimed to verify the nutritional and curative effects of protein hydroysate in rats model with gastric ulcer induced by restraint and water-immersion stress. Sprague-Dawley, famale rats weighing approximtely 200g were forced in 5$\times$5$\times$15cm plexiglas cage. The restraint and water immersion stress was carried at 20$\pm$2$^{\circ}C$ for 8-hours. After stress 4 kinds of diets(10% casein, 20% casein, 10% casein hydrolysate, 20% casein hydrolysate) were given for 5 days. In the gastric ulcer rats model, the growth, gastric emptying rate, trypsin activity in gastrointestinal content, plasma total protein, albumin, $\alpha$-amino-N, UUN, creatinine and hydroxyproline of the urine and nitrogen retention were analyzed for nutritional effects of dietary nitrogen levels(10%, 20%) and sources (casein, casein hydrolysate). The results were as follows ; In gastric ulcer rats model, severeness of ulcer, plasma protein, gastric emptying rate, nitrogen retention rate were not different between 20% casein-fed group and 20% casein hydrolysatefed group. But 10% casein hydrolysate-fed group had more curative group. The casein hydrolysate diet-fed group was lower trysin activity in small intestianl content than the casein-fed group, at both casein level(10%, 20%). Finally at 20% levels, there was no difference between casein and casein hydrolysate diet, but 10% level, casein hydrolysate diet was more curative of ulcer than casein diet in gastric ulcer rat model. The results of this study provide useful information concerning diet therapy for the patients with gastrointestinal diseases and the field of enteral diet materials.

  • PDF

Simulation of concrete shrinkage taking into account aggregate restraint

  • Tangtermsirikul, Somnuk;Nimityongskul, Pichai
    • Structural Engineering and Mechanics
    • /
    • 제5권1호
    • /
    • pp.105-113
    • /
    • 1997
  • This paper proposes a model for simulating concrete shrinkage taking into account aggregate restraint. In the model, concrete is regarded as a two-phase material based on shrinkage property. One is paste phase which undergoes shrinkage. Another is aggregate phase which is much more volumetrically stable. In the concrete, the aggregate phase is considered to restrain the paste shrinkage by particle interaction. Strain compatibility was derived under the assumption that there is no relative macroscopic displacement between both phases. Stresses on both phases were derived based on the shrinking stress of the paste phase and the resisting stress of the aggregate phase. Constitutive relation of paste phase was adopted from the study of Yomeyama, K. et al., and that of the aggregate phase was adopted from the author's particle contact density model. The equation for calculating concrete shrinkage considering aggregate restraint was derived from the equilibrium of the two phases. The concrete shrinkage was found to be affected by the free shrinkage of the paste phase, aggregate content and the stiffness of both phases. The model was then verified to be effective for simulating concrete shrinkage by comparing the predicted results with the autogeneous and drying shrinkage test results on mortar and concrete specimens.

한약처방 JSB가 구금스트레스로 우울증을 유발한 생쥐의 행동과 생체지표에 미치는 영향 (Effects of JSB, a Korean Medicine, on Behaviors and Biological Factors in a Mouse Model of Depression Induced by Restraint Stress)

  • 신윤민;임형택;황은영;김가나;이원길;김연경;장희진;최정준
    • 동의신경정신과학회지
    • /
    • 제32권1호
    • /
    • pp.25-37
    • /
    • 2021
  • Objectives: Depression is a mood disorder showing low energy, loss of interest, anhedonia, and anxiety. It affects a patients' daily life. This disease is considered a social problem because the patient may commit suicide in extreme cases. JSB is composed of 12 Korean medicinal herbs. It has been prescribed to patients with depression. The objective of this study is to investigate anti-depressive effects of JSB on restraint stress-induced depression in a mouse model. Methods: Depression was induced by restraint stress. Mice were orally administered JSB at 10, 20, or 40 mg/kg for 14 days. Forced swimming test (FST) and open field test (OFT) were performed. Brain-derived neurotrophic factor (BDNF) mRNA level was measured by real time-PCR. Plasma levels of corticosterone and serotonin were measured by ELISA. Blood levels of AST and ALS were measured using a biochemical analyzer. Results: JSB treatment significantly reduced the immobility time in FST. BDNF mRNA level was increased by JSB treatment in the hippocampi of mice. Although the expression of TNF-α was also increased by JSB, such increase was not statistically significant. The increase of corticosterone level in plasma induced by restraint stress was significantly down-regulated by JSB. JSB reduced blood level of AST, but not ALT. Conclusions: JSB has a potential to manage depression, setting a foundation for clinical application of Korean medicine with safety.