• Transactions of the Korean Society of Automotive Engineers
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• v.10 no.6
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• pp.125-132
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• 2002

Bumpers are structural components to reduce physical damage to the front and rear ends of a passenger motor vehicle from low speed collisions. Damage assessment and the protectiveness are the commonly used designing criteria but in this study, relative displacements of the bumper are examined. To absorb the crash energy without significant damage to the bumper itself, foam material is installed between fascia and beam. However, it is not easy to predict the exact displacements generated in bumper structures through FEM because the compressive stress-strain curve of a foam material depends on strain rates that deviates significantly on each trial. Under this uncertain condition, a range of displacements is calculated and the optimum design is performed using the design of experiments. The result will be used to find the design that minimizes the weight within displacement constraints. The orthogonal array of L9 is introduced to find the optimum of the design variables that considers the thickness of inner beam, outer beam and stay, This study will suggest the design procedure of a front bumper using the uncertain stress-strain curve of a foam material.

• Journal of Theoretical and Applied Mechanics
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• v.2 no.1
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• pp.31-50
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• 1996

In this paper, a finite element analysis based on the local approach concept to fracture in the continuum damage mechanics is performed to analyze ductile fracture in two dimensional quasi-static state. First an isotropic damage model based on the generalized concept of effective stress is proposed for structural materials in the context of large deformation. In this model, the stiffness degradation is taken as a measure of damage and so, the fracture phenomenon can be explained as the critical deterioration of stiffness at a material point. The modified Riks' continuation technique is used to solve incremental iterative equations. Crack propagation is achieved by removing critically damaged elements. The mesh size sensitivity analysis and the simulation of the well known shearing mode failure in plane strain state are carried out to verify the present formulation. As numerical examples, an edge cracked plate and the specimen with a circular hole under plane stress are taken. Load-displacement curves and successively fractured shapes are shown. From the results, it can be concluded that the proposed model based on the local approach concept in the continuum damage mechanics may be stated as a reasonable tool to explain ductile fracture initiation and crack propagation.

• Corrosion Science and Technology
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• v.17 no.1
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• pp.6-11
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• 2018

Outdoor exposure tests using of 7B04 aluminium alloy samples including plate, tensile and various SCC samples were carried out in Tuandao station, Shandong province (East of China) and Wanning station, Hainan province (South of China). Corrosion characteristics including weight loss, microstructure, tensile strength and SCC susceptibility were investigated. The corrosion rates in Tuandao and Wanning showed high to low and the corrosion rates changed to the following equation of $w=at^b$ (b<1). The corrosion of 7B04 aluminium alloy in Wanning was more serious than that in Tuandao. Pitting appeared at early stage of expose test, and it can be changed to general corrosion with test time extension. The 7B04 aluminium alloy of which specimen shapes are forging and thick plate also showed SCC (Stress corrosion cracking) in the marine atmosphere. The higher SCC sensitivity was observed in Wanning station than in Tuandao station. The 7B04 aluminium alloy with a high stress level was more sensitive to SCC. Intergranular and transgranular or a mixed mode of cracking can be observed in different marine exposure.

• Journal of Microbiology and Biotechnology
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• v.16 no.9
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• pp.1416-1421
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• 2006

We identified a gene encoding the N-acetylmuramoyl L-alanine amidase (amiB) of Vibrio anguillarum, which catalyzes the degradation of peptidoglycan in bacteria. The entire open reading frame (ORF) of the amiB gene was composed of 1,722 nucleotides and 573 amino acids. The deduced amino acid sequence of AmiB showed a modular structure with two main domains; an N-terminal region exhibiting an Ami domain and three highly conserved, continuously repeating LysM domains in the C-terminal portion. An amiB mutant was constructed by homologous recombination to study the biochemical function of the AmiB protein in V. anguillarum. Transmission electron microscopy (TEM) revealed morphological differences, and that the mutant strain formed trimeric and tetrameric unseparated cells, suggesting that this enzyme is involved in the separation of daughter cells after cell division. Furthermore, inactivation of the amiB gene resulted in a marked increase of sensitivity to oxidative stress and organic acids.

• Anxiety and mood
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• v.13 no.1
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• pp.10-16
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• 2017

Objective : This study aimed to investigate differences in demographic, clinical characteristics, and quality of life between panic-disorder patients with generalized anxiety disorder (PD+GAD) and without generalized anxiety disorder (PD-GAD). Methods : We examined data from 218 patients diagnosed with PD+GAD (150 patients) and PD-GAD (68patients). The following instruments were applied: Stress coping strategies, Beck Depression Inventory (BDI), Beck Anxiety Inventory (BAI), Panic Disorder Severity Scale (PDSS), Anxiety Sensitivity Index-Revised (ASI-R), Albany Panic and Phobia Questionnaire (APPQ), NEO-neuroticism(NEO-N), Short Form health survey-36 (SF-36). Results : Compared to the PD-GAD group, the PD+GAD group had higher scores in emotion-focused coping strategies and clinical severity, such as BDI, BAI, PDSS, ASI, APPQ, and neuroticism. The PD+ GAD group showed lower scores in most scales in SF-36 status than PD-GAD group. Conclusions : This study shows that PD+GAD patients are different from PD-GAD patients in coping strategies, clinical severity and quality of life. It emphasizes the need of personalized therapy in clinical approach among patients with PD+GAD.

• Journal of Ocean Engineering and Technology
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• v.31 no.4
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• pp.299-307
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• 2017

The design of the mooring line to maintain the position of an offshore structure in rough marine environments is recognized as a very important consideration. Conventional fatigue evaluation of a mooring line was performed by considering the tensile force acting on the mooring line, but the mooring line broke after 238 days in the girassol area even though the expected fatigue life was expected to be longer. The causes of this event are known to be due to OPB/IPB (out-of-plane bending/in-plane bending) caused by chain link friction due to the excessive tensile strength of the mooring line. In this study, three models with different boundary conditions were proposed for fatigue analysis of a mooring line considering OPB/IPB. Interlink stiffness was calculated by nonlinear structure analysis and a stress concentration factor was derived. In addition, the sensitivity of interlink stiffness according to the magnitude of tensile force, large deformation effect, and coefficient of friction was analyzed, and the effect of critical elastic slip and bending moment calculation position on interlink stiffness was confirmed.

• Advances in aircraft and spacecraft science
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• v.7 no.2
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• pp.135-149
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• 2020

In the current paper, a generalization of the results of Zhao et al. (2008) on a new design of C/C composite multidisc brake system is presented. The purpose of this paper is to study the effect of thermal sensitivity of Carbon/Carbon (C/C) composite material on the temperature distributions, deformation, and stress during braking. In this regard, a transient temperature-displacement coupled analysis for C/C composite brake discs with frictional heat generation under simulated operating conditions is performed. An axisymmetric model for brake system is used for the finite element analysis according to the theory of energy transformation and transportation. The transient temperature distributions on the friction surfaces, deformation, and stress are obtained. To check the validity, the results are corroborated with other solutions available in the literature, wherever possible. The current study could be used as a guide in the initial design of a high performance multidisc brake system.

• Journal of the Korean Society of Mechanical Technology
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• v.13 no.2
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• pp.115-121
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• 2011

The size of hydrogen molecule is not so small as to invade into the lattice of material, and therefore, hydrogen invades into the material as atom. Hydrogen movement is done by diffusion or dislocation movement in the near crack tip or plastic deformation. Hydrogen appeared to have many effects on the mechanical properties of the Cr-Mo steel alloys. The materials for this study are 1.25Cr-0.5Mo and 2.25Cr-1Mo steels used at high temperature and pressure. The hydrogen amount obtained by theoretical calculation was almost same with the result solved by finite element analysis. The distribution of hydrogen concentration and average concentration was calculated for a flat specimen. Also, finite element analysis was employed to simulate the redistribution of hydrogen due to stress gradient. The calculation of hydrogen concentration diffused into the material by finite element method will provide the basis for the prediction of delayed fracture of notched specimen. The distribution of hydrogen concentration invaded into the smooth and notched specimen was obtained by finite element analysis. The hydrogen amount is much in smooth specimen and tends to concentrate in the vicinity of surface. Hydrogen embrittlement susceptibility of notched specimen after hydrogen charging is more remarkable than that of smooth specimen.

• Animal cells and systems
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• v.7 no.1
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• pp.57-62
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• 2003

Flounder B lymphocytes isolated from different tissues were studied in terms of cell proliferation, apoptosis and the effects of cortisol on these processes. B lymphocytes, isolated from the flounder head kidney and spleen, were characterized by higher proliferation and lower intracellular calcium ($Ca^2$) response to lgcrosslinking compared with peripheral blood B lymphocytes. Cortisol induced high levels of apoptosis (150% of control levels) in peripheral blood B lymphocytes, in combination with a stimulatory LPS signal. Head kidney and to a lesser extent spleen B lymphocytes, although less sensitive than their equivalent in peripheral blood, underwent cortisol-induced apoptosis irrespective of extra stimulation up to 142% of control levels. Also proliferation with and without LPS stimulation was suppressed by cortisol (compared to plasma values measured during stress conditions) that is effective in inducing a significant increase in apoptosis in all three populations of B-cells, suggesting that cortisol may be important for immunoregulation in both stressed and non-stressed conditions. This implies possible severe impact of stress on lymphocyte development and activity, Different sensitivity of B-cells to the corticosteroid, with respect to developmental stage and activity, may prevent excessive and long lasting depletion of B-lymphocytes.

• Advances in aircraft and spacecraft science
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• v.6 no.1
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• pp.51-67
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• 2019

AMOSC (Automatic Margin Of Safety Calculation) is a SW tool which has been developed to calculate the failure index of layered composite structures by referring to the cutting edge state-of-the-art LaRC05 criterion. The stress field is calculated by a finite element code. AMOSC allows the user to calculate the failure index also by referring to the classical Hoffman criterion (which is commonly applied in the aerospace industry). When developing the code, particular care was devoted to the computational efficiency of the code and to the automatic reporting capability. The tool implemented is an API which has been embedded into Femap Siemens SW custom tools. Then, a user friendly graphical interface has been associated to the API. A number of study-cases have been solved to validate the code and they are illustrated through this work. Moreover, for the same structure, the differences in results produced by passing from Hoffman to LaRC05 criterion have been identified and discussed. A number of additional comparisons have thus been produced between the results obtained by applying the above two criteria. Possible future developments could explore the sensitivity of the failure indexes to a more accurate stress field inputs (e.g. by employing finite elements formulated on the basis of higher order/hierarchical kinematic theories).