When performing finite element analysis using materials with porosity the porosity shows different mechanical properties from the existing mechanical properties of the existing base materials. In this study the equivalent properties were calculated and verified by applying the representative volume element (RVE) method and assuming that the material with porosity is a 2D orthotropic material. In case of finite element analysis using porous material or composite material, it is inefficient to perform the analysis through material modeling. Based on the element volume and element stress values ​​derived using the finite element analysis program, the representative stress values ​​and elastic modulus matrix were calculated using Python. In addition, equivalent properties were derived using the calculated elastic modulus matrix. The pores were simulated by etching a thin plate specimen made of STS304 material in a certain pattern, and the elastic modulus and Poisson's ratio were measured through a UTM and compared with simulation results. It was confirmed that an error of 7.028% for elastic modulus and 10% for Poisson's ratio occurred, and through this, the validity of this simulation was verified.

The demand for materials with porosity is steadily increasing and the need for porous materials is increasing in fields such as chemical engineering and energy storage. In order to minimize trial and error, verifying design validity through finite element method at the design stage has the advantage to verify design validity with low cost. However there are limitations in finite element analysis using porous materials. In this study calculating the equivalent mechanical properties reflecting the porosity was carried out, and the first step was the isotropic elasticity in plane stress condition. The equivalent elastic modulus and the equivalent Poisson's ratio were derived through simulation. Assuming that the voids exist in a two-dimensional symmetrical shape and a constant distribution, the unit cell was defined and the equivalent mechanical properties were calculated. The specimen with same condition were measured through a universal test machine (UTM), the elastic modulus and Poisson's ratio were measured. The similarity between the value obtained through the simulation and the value measured through the experiment was under 5%, so the validity of this simulation was verified. With this result, FEM with porous materials will be used for design.

Gas detection is necessary for various reasons, including the prevention of gas leakages and the creation of necessary environmental conditions. Among the gas detection methods, leakage of gas can be confirmed using materials that undergo color changes that are easily distinguished by the naked eye. Metal nanoparticles (NPs) experience variations in their absorption wavelengths under the localized surface plasmon effect (LSPR) with mechanical stresses, which change the distance between NPs. In this study, we attempted to detect the presence of gas utilizing the LSPR-related color change of a chain of Au NPs. The assembly of Au NPs, arranged in a chain shape, experienced a color change from dark blue to purple with a change in the distance between the NPs by applying a physical force, i.e., compression, stretching, and gas pressure. As the force of compression and the degree of stretching increased, the absorption wavelength shifted from doublet peaks at 650 and 550 nm to a singlet peak at 550 nm. Further, applying gas pressure caused an identical color change. With this result, we propose a method that could be applied to all gases that require detection based on gas pressure.

In general, it is required mechanical properties and strength tests to use the material in engineering applications. The material fringe values of photoelastic materials vary with the supplier, the batch of resin, temperature and age, it is necessary to calibrate each of sheet of photoelastic material at the time of the test. In this paper, we perform tensile tests and calibrations tests for photoelastic stress fringe constant in order to obtain the mechanical properties of materials and photoelastic material fringe constants of PMMA and PSM-1. From this tests, the tensile strength of PMMA and PSM-1 were 100.5 MPa and 71.5 MPa, respectively. Also, the measured material stress fringe constants of PMMA and PSM-1 were 13.33 N/mm and 6.91 N/mm, respectively.

This paper is concerned with the mechanical design of hyperbaric oxygen chamber for multi-users using stress analysis. HBOT(Hyperbaric Oxygen Therapy) is very effective medical equipment for increasing the concentration of melted oxygen in human and animal body. The hyperbaric oxygen supplies to the impaired cell of human and animal to recover the healthy condition. This research reported the design specifications and mechanical safety of hyperbaric oxygen chamber using computational stress analysis with CATIA program. The result from this research can be used for making the practical HBOT equipment for multi-users and to manufacture the real model

In this study, the effects of cryogenic treatment cycles on the residual stress and mechanical properties of 7075 aluminum alloy (Al7075) samples, in the form of a tube-shaped product with a diameter of 500 nm, were investigated. Samples were first subjected to solution treatment at 470˚C, followed by cryogenic treatment and aging treatment. The residual stress and mechanical properties of the samples were systematically characterized. Residual stress was measured with a cutting method using strain gauges attached on the surface of the samples; in addition, tensile strength and Vickers hardness tests were performed. The detailed microstructure of the samples was investigated by transmission electron microscopy. Results showed that samples with 85 % relief in residual stress and 8% increase in tensile strength were achieved after undergoing three cycles of cryogenic treatments; this is in contrast to the samples processed by conventional solution treatment and natural aging (T4). The major reasons for the smaller residual stress and relatively high tensile strength for the samples fabricated by cryogenic treatment are the formation of very small-sized precipitates and the relaxation of residual stress during the low temperature process in uphill quenching. In addition, samples subjected to three cycles of cryogenic treatment demonstrated much lower residual stress than, and similar tensile strength compared to, those samples subjected to one cycle of cryogenic treatment or artificial aging treatment.

A mutation of UNCL, an inner nuclear membrane RNAbinding protein, has been found to eliminate mechanotransduction in Drosophila. UNCL is expressed in human periodontal tissue including in periodontal ligament (PDL) fibroblasts. However, it is unclear how a mechanical stimulus is translated into cellular responses in PDL fibroblasts. The aim of this study was to evaluate the effect of UNCl on mechanical stress related genes in PDL fibroblasts in response to mechanical stress. The mRNA of TGF-β, COX-2, and MMP-2 was up-regulated after UNCL inactivation in PDL fibroblasts under the compression force. Under the tensile force, inactivation of UNCL decreased the expression of Biglycan, RANKL, MMP-2, and TIMP-2 mRNAs while it increased the expression of TIMP-1. p38-MAPK was expressed in PDL fibroblasts under compression forces whereas phospho-ERK1/2, p65-NFkB, and c-fos were expressed under tension forces. The expression and phosphorylation of the mechanical stress related genes, kinases, and transcription factors were changed according to the types of stress. Furthermore, most of them were regulated by the inactivation of UNCL. This suggests that UNCL is involved in the regulation of mechanical stress related genes through the signaling pathway in PDL fibroblasts.

The periodontal ligament (PDL) is that soft, specialized connective tissue situated between the cementum covering the root of the tooth and bone forming the socket wall. The PDL is a connective tissue particularly well adapted to its principal function, supporting the teeth in their sockets and at the same time permitting them to withstand the considerable force of mastication. During the life time, PDL is usually exposed to mechanical stress by mastication. However, little is known about the gene which is related to the mechanical stress in PDL. UNC-50 (PDLs22) was identified and isolated from D. melanogater and C. elegance. This gene was also regulated in sensory bristle for mechanotransduction in D. melanogaster. In this study, to uncover the relationship between UNC-50 and mechanical stress, we induced the mechanical stress by medium displacement in cementoblast cell line. After mechanical stress induction UNC-50 expression was analyzed by RT-PCR, Real-time PCR, and western analysis. The expression of UNC-50 was increased after medium displacement of cementoblast in vitro. Collagen type I, type III, and osteonection mRNAs were also strongly expressed after mechanical stress induction. The results of this study suggest that UNC-50 might responsible for molecular event in PDL inducing cementoblast under mechanical stress.

마이크로 머신 소자는 일반전자 소자와 달리 소자 자체에 미세한 기계적 구조물을 갖고 있으며, 이의 구동을 통하여 센서 또는 엑츄에이터의 기능을 갖게 된다. 이 소자들은 그 작동 요구특성에 따라 패키지의 기계적, 환경적 격리를 요구하거나 분위기조절이 요구되는 등 까다로운 패키지 특성을 필요로 한다. 또한 미세한 작동소자들로 인하여 열 및 열응력에 매우 민감하며, 패키지방법에 따라 구동부위의 작동 특성이 크게 변화할 수 있다. 본 연구에서는 마이크로 머신 소자가 패키지 상에 접촉되어 패키지 될 때, 소자의 접촉 재료 및 공정온도, 크기 등이 마이크로 머신 소자에 미치는 열응력을 연구하였다. 유한요소해석법을 사용하여 소자에 미치는 열응력과 이로 인한 마이크로머신 소자의 물리적 변형을 예측하고, 이를 통하여 마이크로 머신 소자 패키지에 최소한의 열응력을 미치는 소자접속 재료의 선별과 패키지 설계의 최적화를 이루고자 하였다.

활성금속 브레이징 방법으로 스테인레스 스틸과 질화규소를 접합하여 기계적 특성 및 유한요소법을 사용하여 접합체에서 발생되는 잔류응력의 크기를 조사하였다. 고강도 접합체를 제조하기 위하여 연성금속인 Cu 및 Cu/Mo 적층체를 중간재로 사용하였으며, 중간재의 두께 및 구조에 따라 접합체에서 발생되는 잔류응력의 크기 및 분포가 접합강도에 미치는 영향에 관하여 조사하였다.중간재인 Cu의 두께가 0.2mm 일대 세라믹스에 발생되는 최대 잔류응력의 크기가 급격히 감소하였으며, 최대 접합강도가 나타났다. Cu/Mo 다층 중간재를 사용한 접합체에서는 Cu/Mo 두께비가 감소할수록 접합강도는 증가되었다. 스테인레스 스틸/질화규소 접합체에서 Cu/Mo 중간재의 사용은 Cu 중간재 사용보다 접합강도를 증가시키는데 효과적이었으며, 최대 접합강도는 450Mpa 정도이었다. Cu/Mo 중간재를 사용한 접합체에서는 Mo에 최대 인장방향의 잔류응력이 발생하여 강도 측정시 Mo의 지배적인 소성변형으로 잔류응력이 감소되어 접합체의 접합강도를 향상시키는 것으로 생각된다.

어린잎 채소는 조직이 연하고 부드러워 가공, 포장, 유통시에 물리적인 상해를 받기 쉬우며 수확 후 수분증발 및 성분 변화 등으로 품질이 급격히 저하된다. 본 연구는 어린잎 채소 중에서 다채의 수확 후 생리특성을 구명하고 적정 포장방법을 개발하고자 수행하였다. 공시재료는 연구소 온실에서 2007년 1월 29일에 다채 종자를 플러그 트레이에 파종하여 30일 정도 키운 다채를 사용하였으며, 수확 후 에서 12시간 예냉 처리한 후 P-plus 필름,