This present study deals with the effect of micro-alloying elements and transformation temperature on the correlation of microstructure and tensile properties of low-carbon steels with ferrite-pearlite microstructure. Six kinds of lowcarbon steel specimens were fabricated by adding micro-alloying elements of Nb, Ti and V, and by varying isothermal transformation temperature. Ferrite grain size of the specimens containing mirco-alloying elements was smaller than that of the Base specimens because of pinning effect by the precipitates of carbonitrides at austenite grain boundaries. The pearlite interlamellar spacing and cementite thickness decreased with decreasing transformation temperature, while the pearlite volume fraction was hardly affected by micro-alloying elements and transformation temperature. The room-temperature tensile test results showed that the yield strength increased mostly with decreasing ferrite grain size and elongation was slightly improved as the ferrite grain size and pearlite interlamellar spacing decreased. All the specimens exhibited a discontinuous yielding behavior and the yield point elongation of the Nb4 and TiNbV specimens containing micro-alloying elements was larger than that of the Base specimens, presumably due to repetitive pinning and release of dislocation by the fine precipitates of carbonitrides.

Tensile strength was investigated for hybrid bar (HYB), in this study. HYB is made of both steel reinforcement and glass fiber. Cross section of HYB has a shape in which steel reinforcement wrapped with glass fiber. For the production of HYB, rebar of SD400 class and glass fiber of E class are used as main materials. Vinyl ester resin is used to harden a glass fiber. In order to evaluate for tensile strength of HYB, the direct tensile test was performed about total ten specimens. The length of total specimens is 2,200 mm including the grip. Diameter of HYB according to core diameter was considered as a test variable. Direct tensile test for HYB was performed using a UTM with a capacity of maximum 1,000 kN. Tensile strength and strain were measured for each specimen during the test. From the test results, tensile strength and elastic modulus were 317 ~ 341 MPa, 103 ~ 107 GPa, respectively. Especially, elastic modulus of HYB was improved in comparison with usual GFRP bars such as the Aslan 100 or the V-rod.

A tensile failure criterion that can minimize the mesh-dependency of simulation results on the basis of the fracture energy concept is introduced, and conventional plasticity based damage models for concrete such as CSC model and HJC model, which are generally used for the blast analyses of concrete structures, are compared with orthotropic model in blast test to verify the proposed criterion. The numerical prediction of the time-displacement relations in mid span of the beam during blast loading are compared with experimental results. Analytical results show that the numerical error is substantially reduced and the accuracy of numerical results is improved by applying a unique failure strain value determined according to the proposed criterion.

This paper is concerned with a test method that can be used to investigate the parameters of the Johnson-Cook constitutive model. These parameters are essential for accurately analyzing material behavior under impact loading conditions in numerical simulation. Ti-6Al-4V alloy (HCP crytal structure) was used as a specimen for the experiments. In the 10−3-103/ s strain rate range, three types of experimental methods (convention, compression and tension) were employed to compare the differences using MTS-810, SHPB and SHTB. Finite element analysis results when applying these parameters were displayed along with the experiment results.

The composite material has the strong durability and light weight as inhomogeneous material. Nowadays, CFRP composite has been noticed as the light weight, high strength and long fatigue life. This study has been carried actively. In this study, the properties of tensile strengths of CFRP, stainless steel are analyzed, and compared each other. In order to secure the data, the tensile specimens with notches of same size by using CFRP, and stainless steel are manufactured and experimented. When the forced displacement of about 11.5 mm proceeds in case of stainless steel specimen, the maximum load of 31000 N is shown simultaneously with the fracture of specimen. When the forced displacement of about 6 mm proceeds in case of CFRP specimen, the maximum load of 16000 N is shown. So, the structural safety becomes highest at CFRP specimen among these specimens. In this study, the finite element analysis is carried out in order to compare with the experimental results. It is verified that the experimental and analysis results are similarly shown each other. Through the result of this study, it is thought that the simulation analysis data with no experiments are trustworthy at using as the real tensile experimental data.

본 연구는 경상남도 하동군 옥종면 땅밀림 산사태지의 붕괴지 및 피해지역을 중심으로 사면붕괴양상을 규명하기 위해 땅밀림 산사태지의 인장균열지의 월별 변화양상을 조사하였다. 그 결과, 연구대상지에서는 땅밀림 산사태 발생징후라 판단되는 지하수 용출, 융기 및 함몰, 수목이상성장 등이 발견되었다. 아울러 당초 인장균열 두께와 폭은 1 : 4.2, 폭과 길이는 1 : 1.5로 나타났으며, 월평균 인장균열의 증감 폭은 폭 > 길이 > 상단부 사면길이 > 단차 순으로 나타났다. 한편, 강우인자와 인장균열의 형태 및 인장균열의 형태 중 세부인자들 간의 상관분석을 실시한 결과, 모두 상관관계가 없는 것으로 나타났다.

This study was conducted to analyze the nutrient compositions of stem and fruit of Opuntia ficus-indica var. saboten (OF) and Opuntia humifusa (OH). The results of the two-way analysis of variance test indicated that the parts, varieties and parts*varieties had influence on nutrient content except crude protein, soluble dietary fiber, Fe, Se, I, vitamin E, niacin and vitamin C. Moisture and crude ash content was higher in stem than in fruit, while crude lipid and insoluble dietary content was higher in fruit than in stem. Mineral content revealed that K (1,313.67 mg% in OF, 1,351.38 mg% in OH) was the highest in fruit and Ca (5,146.29 mg% in OF, 1,388.19 mg% in OH) was the highest in stem. Vitamin C was the most abundant vitamin in the fruit of OF (199.98 mg%) and OH (187.12 mg%). Polyunsaturated fatty acid was the highest among fatty acids (66.9~70.1%), with higher content in the stem (753.89 mg%) than fruit (578.01 mg%) in OF, while higher in the fruit (1,093.63 mg%) than stem (475.07 mg%) in OH. Moisture, crude protein, Mg, Se and riboflavin was higher in OF than OH; whereas, crude lipid, insoluble dietary fiber, total dietary fiber and monounsaturated fatty acid were higher in OH than OF. These results indicated that OF and OH could be a good food source for Ca, K and Vitamin C. Also, different nutrient content by parts and varieties, can be helpful in choice of parts or varieties for consumer purposes.

In korea, only small amount of nonstructural lightweight concrete is being used through indirect effects such as heat insulation property and soundproofing rather than structural elements due to lack of structural lightweight aggregates and lack of understanding about lightweight concrete development, etc. That`s why structural lightweight concrete to reduce weight has not been put to practical use. This study is a part of high strength lightweight aggregate concrete researches using lightweight aggregates and the purpose of this study is to find out the basic physical characteristics and tension cracking fracture characteristics of lightweight concrete. Crack Mouth Opening Displacement is measured through 3 point flexure experiment about notch beam. Load-CMOD characteristics are examined through rules of countries, characteristics of lightweight concrete and tension cracking fracture experiments. The degree of tensile characteristic alteration according to size changes of specimen and the characteristics about crack surface are analyzed. The changes of softening curve are analyzed and fracture energy is drawn through inverse analysis by the obtained Load-CMOD curve. To decide fracture energy and analysis parametric, inverse analysis is conducted and Ant Colony Method is conducted for optimization and then a way to find out optimal parameterization fracture energy is suggested.

The hydrogen embrittlement of two austenitic high-manganese steels was investigated using tensile testing under high-pressure gaseous hydrogen. The test results were compared with those of different kinds of austenitic alloys containing Ni, Mn, and N in terms of stress and ductility. It was found that the ultimate tensile stress and ductility were more remarkably decreased under high-pressure gaseous hydrogen than under high-pressure gaseous argon, unlike the yield stress. In the specimens tested under high-pressure gaseous hydrogen, transgranular fractures were usually observed together with intergranular cracking near the fracture surface, whereas in those samples tested under high-pressure gaseous argon, ductile fractures mostly occurred. The austenitic high-manganese steels showed a relatively lower resistance to hydrogen embrittlement than did those with larger amounts of Ni because the formation of deformation twins or microbands in austenitic highmanganese steels probably promoted planar slip, which is associated with localized deformation due to gaseous hydrogen.

These days, the Composite Slabs with Deep Deck plate was commonly used in domestic construction site, and, the application of the Slim Floor system was increased from the Enlargement and High-rise Building. But, Slim Floor system using the Deep Deck was shown safety problem caused by the deflection and local buckling in construction phase when used to more than 6m. Therefore, for solving the problem, the installation of the shores is essential. This study is realize the long span slab without shores from control the deflection through applied the pre-tensioning elements in CAP deck. In addition, by applying the pre-tensioning member as the tensile member of the CAP Deck slab, the pre-tensioning member for the shores tries to be used as the structural member. Accordingly, to determine the flexural performance of the CAP Deck slab through the pre-tensioning force in tensile member, and, the composite effect of the CAP Deck slab by the experiments.

This paper presents a study of the tensile properties of austenitic high-manganese steel specimens with different grain sizes. Although the stacking fault energy, calculated using a modified thermodynamic model, slightly decreased with increasing grain size, it was found to vary in a range of 23.4 mJ/m2 to 27.1 mJ/m2. Room-temperature tensile test results indicated that the yield and tensile strengths increased; the ductility also improved as the grain size decreased. The increase in the yield and tensile strengths was primarily attributed to the occurrence of mechanical twinning, as well as to the grain refinement effect. On the other hand, the improvement of the ductility is because the formation of deformation-induced martensite is suppressed in the high-manganese steel specimen with small grain size during tensile testing. The deformationinduced martensite transformation resulting from the increased grain size can be explained by the decrease in stacking fault energy or in shear stress required to generate deformation-induced martensite transformation.

In the present study, the tensile properties and dynamic strain aging of an Fe-24.5Mn-4Cr-0.45C alloy were investigated in terms of strain rate. During tensile testing at room temperature, all the stress-strain curves exhibited serrated plastic flows related to dynamic strain aging, regardless of the strain rate. Serration appeared right after yield stress at lower strain rates, while it was hardly observed at high strain rates. On the other hand, strain-rate sensitivity, indicating a general relationship between flow stress and strain rate at constant strain and temperature, changed from positive to negative as the strain increased. The negative strain-rate sensitivity can be explained by the Portevin Le Chatelier effect, which is associated with dynamic strain aging and is dependent on the strain rate because it is very likely that the dynamic strain aging phenomenon in high-manganese steels is involved in the interaction between moving dislocations and point-defect complexes.

The effect of CNT diameters on properties of CNT-polyamide composites was investigated such as electrical conductivity, tensile strength and thermal conductivity. To get different diameter distributions of CNTs, several portions of Mo and Fe in Mo-Fe/MgO catalysts were synthesized by a combustion method at 600℃. And all CNTs growed at 900℃ with 3 SLM methane and 1 SLM hydrogen for 40min. Four kinds of CNTs with different diameter distributions, such as 1~3nm, 3~7nm, 7~13nm, and 10~30nm, were selected to make CNT-polyamide composites. Each composite was manufactured by a solution mixing using bar-type ultra-sonicator in the CNT portions from 1phr to 50phr. And electrical conductivity, tensile strength, and thermal conductivity were measured. Three properties of CNT-polyamide composite, manufactured with 10nm diameter, were more excellent compared to other composites, with electrical conductivity  Ω at 7phr, thermal conductivity 2.4.W/mK at 40phr, tensile strength 60MPa at 30phr. CNTs with a diameter of 10nm were superior to other diameters for the multi-functional composite such as CNT-polyamide composites.

In this paper, we study the calculation for the damage area of the tension specimens using image processing techniques. This study was able to calculate the area of the damage region on the basis of original image. Generally, to extract the area in the original image, we have to use opening operation, close operation, the Hit-or-Miss operation and bottom hat filter, top hat filter, etc. In particular, to extract the area of the composite specimen discussed in this study, we have to use the combination of the operations and filters because it is non-isotropic material, or should develop a new algorithm based on it.

밀가루를 이용하여 만든 반죽과 이를 이용하여 가공된 면제품의 경우 시료의 두께가 매우 작아 일반적인 압축응력을 사용한 측정으로 기계적 특성이나 관능검사와의 상관관계를 규정 짓는 조직 감을 측정하는데 어려움이 있다. 면제품에 인장력을 바탕으로 한 기계적 특성을 측정을 적용할 경 우 압축응력이 가지고 있는 한계점들의 많은 부분들이 보완될 수 있다.또한 반죽의 경우 배합비에 따른 성형정도가 가공적성에 가장 중요한 요인으로 평가되고 있으며,이는 신장성을 나타내는 인장 력의 측정으로 정량화가 가능하다. 인장력측정이 기계역학적인 장점에도 불구하고 사용되기 어려운 이유는 측정하고자 하는 시편을 인장력이 적용되는 방향으로 고정시킴이 필수적인데, 이 같은 고정 점에서 미끄럼(slip) 현상이나 응력집중(stress concentration)이 발생하여 정확한 측정이 어렵기 때문 이다. O‐ring형태로 시편을 만들어 인장력 측정을 할 경우 미끄럼현상과 함께 응력집중현상을 최소 화하여 면반죽 및 면 제품의 인장력 측정이 가능하다. 본 연구의 목적은 1) O‐ring 형상의 시편을 이용한 면류제품의 인장도 측정법의 개발, 2) 밀가루 면,밀가루와 분말형 첨가물이 혼합된 면, 밀가루와 액상 혼합물이 혼합된 면의 인장도를 ring tensile 측정법으로 측정하여 혼합된 첨가물이 조직감에 미치는 영향을 평가, 3) 영상분석을 통한 인장도 측정 시의 변형률 분포도의 비교, 4) ring tensile측정법을 이용한 응력 및 변형률의 계산이다. 시료로는 1) 밀가루만을 이용한 반죽과 면, 2) 유색감자분말을 첨가한 면, 3)해삼추출물을 첨가한 면을 사용하여 반죽과 면상태에서의 인장력을 측정하였다. 인장력을 측정하기 위한 장치는 자체 개 발된 장치를 사용하여 texture analyzer(Brookfiled, Middleboro, MA US)에 부착하여 인장력을 측정하 였다. 시편에 인장력을 가한 속도는 0.5mm/sec로 고정하여 모든 실험을 수행하였다. 면의 시료의 두 께는 5mm로 만들어 사용하였다. 밀가루만으로 만든 면의 압축응력을 측정할 경우 통계적으로 유의미한 결과를 파손강도와 파손 거리에서 모두 얻기가 어려웠다. Ring형상의 시편을 만들어 인장력을 이용하여 측정할 경우 통계적 으로 유의미한 결과를 5반복에서 도출할 수 있었으며 10반복 이상을 적용할 시에도 그 5반복과 비 교하여 동일한 결과를 보여주었다. 밀가루로만 만든 면의 경우 반죽의 파손인장강도는 조리 시의 면보다 낮았으나 반죽의 파손인장거리는 조리된 면보다 높았다. 이는 조리 전 반죽 상태의 글루텐 의 신장성과 조리 후 호화상태를 정확하게 측정할 수 있음을 보여준 결과이다. 분말의 첨가물을 포 함한 경우도 유사한 결과를 나타내었으며, 첨가되는 분말의 함량, 입자크기 등에 따른 유의미한 기 계적 특성을 측정할 수 있었다. 액상의 첨가물도 인장강도와 인장력을 정확히 측정할 수 있었다. 본 연구결과는 면제품이나 시편의 두께가 작을 경우 인장력을 측정하여 시료의 기계적 특성을 정 량화 할 수 있는 방법을 제공하였으며 다양한 시료에서 유의차 있는 결과를 보여주었다.

Until recently, almost all ETFE film structures that have been erected is the cushion type because there are problems at lower allowable strength under elastic range and viscosity behaviour such as creep and relaxation of ETFE films under long-term stresses. But the number of tension type structures is currently increasing. This paper proposes the stretch fabrication of ETFE film to verify the applicability of ETFE films to tensile membrane structures. First of all, to investigate the possibility of application on tensile membrane structures, the stretch fabrication test is carried out, and it is verified that it is possible to increase the yield strength of the film membrane structures. After simulating the experiment also carries out an analytical investigation, and the effectiveness of the elasto-plastic analysis considering the viscous behavior of the film is investigated. Finally, post-aging tension measurement is conducted at the experimental facilities, and the viscosity behavior resulting from relaxation is investigated with respect to tensile membrane structures.

The hardenability of boron steel specimens with different molybdenum and chromium contents was investigated using dilatometry and microstructural observations, and then was quantitatively measured at a critical cooling rate corresponding to 90 % martensite hardness obtained from a hardness distribution plotted as a function of cooling rate. Based on the results, the effect of an austenitizing temperature on the hardenability and tensile properties was discussed in terms of segregation and precipitation behavior of boron atoms at austenite grain boundaries. The molybdenum addition completely suppressed the formation of pro-eutectoid ferrite even at the slowest cooling rate of 0.2 oC/s, while the chromium addition did at the cooling rates above 3 oC/s. On the other hand, the hardenability of the molybdenum-added boron steel specimens decreased with an increasing austenitizing temperature. This is associated with the preferred precipitation of boron atoms since a considerable number of boron atoms could be concentrated along austenite grain boundaries by a non-equilibrium segregation mechanism. The secondary ion mass spectroscopy results showed that boron atoms were mostly segregated at austenite grain boundaries without noticeable precipitation at higher austenitization temperatures, while they formed as precipitates at lower austenitization temperatures, particularly in the molybdenum-added boron steel specimens.

This study investigates the property of crack growth at the specimen of structural steel. The behaviour of fracture mechanics on the specimens with only a center crack and with holes existed symmetrically near a center crack is studied. The tensile load is applied on the specimens with these conditions. Stress intensity factors are obtained by the basis of these experimental values and these values are verified with the structural analysis of finite element method. As the length of center crack becomes larger in case of the specimen with holes existed symmetrically near a center crack, the values of deformation energy and stress become larger. On the contrary, the values of deformation energy and stress become smaller as the length of center crack becomes larger in case of the specimen with only a center crack. By examining the stress intensity factor in this study, this value becomes rather smaller although the length of center crack becomes larger. There is the position where crack is likely to happen or weak part at the mechanical structure or the machine. As the holes are punctured and arranged adequately near this crack or weak part by using the result of this study, the fracture due to it can be prevented.

This study investigated the microstructure and tensile properties of a recently made block-type Ni-Cr-Al powder porous material. The block-type powder porous material was made by stacking multiple layers of powder porous thin plates with post-processing such as additional compression and sintering. This study used block-type powder porous materials with two different cell sizes: one with an average cell size of 1,200 μm (1200 foam) and the other with an average cell size of 3,000 μm (3000 foam). The γ-Ni and γ’-Ni3Al were identified as the main phases of both materials. However, in the case of the 1,200 foam, a β-NiAl phase was additionally observed. The relative density of each block-type powder porous material, with 1200 foam and 3000 foam, was measured to be 5.78% and 2.93%, respectively. Tensile tests were conducted with strain rates of 10−2~10−4 sec−1. The test result showed that the tensile strength of the 1,200 foam was 6.0~7.1 MPa, and that of 3,000 foam was 3.0~3.3 MPa. The elongation of the 3,000 foam was higher (~9%) than that (~2%) of the 1,200 foam. This study also discussed the deformation behavior of block-type powder porous material through observations of the fracture surface, with the results above.