Earticle

Residual stresses can have a significant influence on the fatigue lives of structural engineering components. For the accurate assessment of fatigue lifetimes a detailed knowledge of the residual stress profile is required. Significant advances have been made in recent years fur obtaining accurate and reliable determinations of residual stress distributions. These include both experimental and numerical methods. The purpose of this study is to simulate peening process with the help of the finite element method in order to predict the magnitude and distribution of the residual stresses in accordance with the parameters, which are, e.g. shot velocity, shot diameter, shot impact angle, shot shape, distance between two impinging shots, and material parameters.

본 연구는 현재 내진 구조 분야에서 압축부재로 사용되고 있는 폴리우레탄의 한계를 극복하기 위해 폴리케톤이라는 신소재 제안을 목적으로 한다. 기존 폴리우레탄은 우수한 탄성 특성을 지녔음에도 불구하고 구조물에 발생하는 변위를 회복하기에는 부족한 경향이 있다. 반면, 폴리케톤은 뛰어난 강도 성능을 보유함과 동시에 친환경 소재로 주목받고 있다. 이러한 장점을 가진 폴리케톤의 압축특성 평가를 위하여 기존에 사용되고 있던 폴리우레탄과의 비교실험을 진행하고자 한다. 단순압축실험과 반복 하중 조건에서의 실험 속도 변화를 통해 폴리케톤의 속도 의존성을 파악하고, 추가적으로 선행압축을 적용하여 압축거동 특성을 확인하였다. 폴리케톤은 폴리우레탄에 비하여 약 10배가량 높은 압축강도를 나타내었으며 비교적 작은 변위에서는 14배가량 높은 변형 회복능력으로 폴리케톤의 우수한 회복특성을 입증하였다.

The purpose of this study is to propose a new material called polyketone to overcome the limitations of polyurethane, which is currently used as a compression member in the field of earthquake-resistant structures. Although existing polyurethane has excellent elastic properties, it tends to be insufficient to recover the displacement that occurs in the structure. On the other hand, polyketone has excellent strength performance and is attracting attention as an eco-friendly material. In order to evaluate the compression properties of polyketone, which has these advantages, we would like to conduct a comparative experiment with polyurethane that was previously used. The speed dependence of polyketone was identified through simple compression experiments and experimental speed changes under repeated loading conditions, and additional compression behavior was applied to confirm compression behavior characteristics. Polyketone showed compressive strength about 10 times higher than that of polyurethane, and its excellent recovery characteristics were demonstrated by its deformation recovery ability about 14 times higher at relatively small displacements.

This study shows a variance regularization method in order to obtain the stable optimal solutions, when a numerical method accelerating design variables is used for material topology optimization algorithm. Since a moved and regularized Heaviside function used in the accelerated method is composed of nonlinear concave and convex functions in a given design domain between 0 and 1, design variables below 0.5 can move fast toward the value of 0 and those over 0.5 are rapidly located to the value of 1. However optimal solutions may be not stable due to singularity of element stiffness, while the accelerated design variables are too closed to value 0. In particular this instability may occur to the accelerated method-based material topology optimization algorithms much repeating the moved and regularized Heaviside function. In order to resolve the problem, in this study, a variance regularization is formulated within a linear governing equation for structural analyses of optimization procedures. Numerical examples for topologically optimally modeling a linear elastostatic MBB-beam verify that the accelerated method of design variables take numerical stability of topological optimal solutions by being associated with the variance regularization method.

This study is to develop a new composite material, a mixture of epoxy resin and granite aggergates which is called Expoxy-Granite, to overcome the inherent disadvantages of conventional materials commonly used as a bed structure material of long-term dimensional/ thermal stability. Under the various manufacturing conditions which could be formulated through experimental investigation, we have constructed 6 kinds of Epoxy-Granite structure models having one fifth the size of the ultra-precision machine tool bed structure. They are compared with cast iron and pure granite models through the dynamic test and the thermal deformation test. Both in the steel ball dropping test and in the forced vibration test, three types of epoxy-granite models made in this study have shown much better dynamic characteristics than the cast iron model and almost the same characteristics as compared with the pure granite model. In the thermal deformation test the above composite materials have also represented lower thermal displacements in the vertical direction of each model as compared with other specimens. It is therefore seen that the epoxy-granite complsite material can be applied to the construction of high-precision machine tool bed, instead of cast iron or pure granite.

A new fungivle material named Epoxy-Granite composite is applied to the column structure of drilling center in order to investigate the advanced dynamic charateristics comparing with a conventional cast iron material. The dimensions of new column structure are adjusted to keep the same stiffness (EI value) and the manufacturing conditions are formulated based on the preceeding research experience about the development of Epoxy-Granite structural material. The two kinds of experiments are set up, one of which is for the measurement of natural mode and frequency using experimental modal analysis, and the other one is for the measurement of vibration amplitude during idling operation of a machine tool. The comparison of maximum accelerance values at each natural frequency of bending mode shows a Epoxy-Granite column have larger modal damping ratios(over 2times) than a cast iron column. The vibration amplitude of Epoxy-Granite column measrued on the bed, motor base, and top of column are also much smaller (up to 12%) than the case of cast iron column. It is therefore confirmed that a Epoxy-Granite material exhibits a good anti- vibrational propderty even if it is used under the actual operational environments of machine tool as a practical structural element.

본 연구는 부석사 조사당 벽화의 벽체 바탕에 대한 재료와 구조를 과학적으로 조사⋅분석하 여, 벽체 바탕의 제작기술과 원재료의 특성을 규명하고자 하였다. 부석사 조사당 벽화 벽체 바탕의 구성요소는 가시새, 외가지, 외엮기 줄로 확인되었다. 벽체 바탕 요소 중 가시새는 졸참나무류(Prinus Section)로 식별되었으며, 일정 규격의 직사각형 각재로 가공하여 벽화별로 6∼11개가 설치되었다. 가시새의 배치 구조는 상⋅하부는 조밀하게 중앙 부분은 넓게 배치한 특이점이 확인되었다. 외가지 는 소나무류(Hard pines)로 식별되었으며, 단면 지름 20mm 이내의 나뭇가지를 그대로 사용하거나 유사한 규격으로 가공하여 비교적 일정한 간격으로 설치되었으며, 설외와 눌외 배치간격의 차이점은 없었다. 외엮기 줄은 볏짚으로 만든 새끼줄이 사용되었고 가시새와 외가지를 대각선으로 엮어 벽체 바탕을 안정적으로 고정하였다. 방사성탄소연대 분석 결과, 벽체 바탕 재료의 보정연대는 13∼14세 기로 조사당 건축연대로 추정되는 14세기 말과 밀접한 관련이 있음을 확인하였다.

This study analyzed the materials and structure of the wooden wall framework of a mural painting at the Josadang Shrine of Buseoksa Temple to identify the manufacturing techniques and characteristics of the used raw materials. The observed components of the wooden wall framework included Gasisae, laths, and straw ropes. The Gasisae wood species was identified as belonging to the Prunus section. Its shape was confirmed to be rectangular and processed into uniform dimensions, with the number of installed pieces ranging from 6 to 11. The arrangement of Gasisae exhibited a distinctive feature: dense placement in the upper and lower parts and wider spacing in the central part. The wood species of the laths was identified as hard pines with branches of 20 mm or less in diameter, used either in their natural form or processed, and arranged at relatively uniform intervals. The spacing between the vertical and horizontal laths was similar. The straw rope was identified as an Oryza-type plant material used to diagonally tie the Gasisae and laths, providing stable reinforcement for the wooden wall framework. Radiocarbon dating analysis confirmed that the calibrated age of the wooden wall framework was between the 13th and 14th centuries. This finding encompasses the 14th century, the construction period of the Josadang Shrine, indicating a close temporal relationship between the two.

The purpose of this study is to analyze the architectural technical characteristics of the Walker House as UN military facilities built in the Busan capital of the Korean War. Walker House was constructed by collecting and accumulating various kinds of stone fragments without using unitized or standardized materials widely used from modern period. It is a Japanese-style roof structure despite the fact that it is a United Nations military facility where the US military is the main force. The materials and structural characteristics of these masonry structures and Japanese-style roof are technical historical records that can refer to the supply and demand of material, the difficulty of systematic performance design, and the participation of Korean engineers during the war.

보물 쌍자총통은 조선 중기에 사용하던 유통식 개인용 소용화기(小用火器)로 선조 16년(1583 년)에 제작되었다. 이 연구는 동아대학교 석당박물관 소장 쌍자총통을 중심으로 제작기법에 대해 조사한 내용을 정리한 것이다. 쌍자총통은 전체 길이 53.3 cm, 구경 1.5 cm이다. 총구 2개가 연결된 몸통에는 6개의 약선혈이 있고 2개의 죽절이 관찰된다. 모병에는 사용법과 제작시기에 대한 명문이 새겨져 있다. 총구와 모병의 연결부에는 주조로 인한 어긋남이 있고, 측면에서는 주조 후 연마한 연마흔과 요철형 연결부도 관찰된다. 내부구조 조사 결과 쌍자총통의 내부의 주조기포가 확인되었 고, 주물시 주물틀을 고정시키기 위해 사용하는 채플릿(chaplet)으로 보이는 6곳이 관찰되었다. 채플 릿으로 확인되는 부분의 표면 분석결과 철(Fe) 수치가 높게 나타났다. 성분 분석 결과, 쌍자총통의 주성분은 구리(Cu)–주석(Sn)–납(Pb)을 주원료로 하는 3원계합금인 청동으로 판단된다.

The Ssangja Chongtong Gun, manufactured in the 16th year of King Seonjo’s reign (1583), is a small tubular personal firearm used during the mid-Joseon Dynasty. This study investigated gun-manufacturing techniques focusing on the Ssangja Chongtong Gun owned by the Seokdang Museum of Dong-A University. The Ssangja Chongtong Gun is 53.3 cm in total length and 1.5 cm in diameter. There are six fuse holes and two rings, similar to bamboo nodes, on the double barrels. The handle is engraved with inscriptions describing the gun’s use and production period. There is misalignment between the barrel and handle of the gun that is due to casting; on the side, polishing marks and uneven joints formed after casting are observed. Research on its internal structure confirmed the presence of casting bubbles inside the Ssangja Chongtong Gun. Six parts that appear to be chaplets used to fix the casting mold during casting were also observed. Surface analysis of the parts identified as chaplets showed a high level of iron (Fe). Based on component analysis, the primary component of the Ssangja Chongtong Gun was determined to be bronze, a ternary alloy with copper (Cu), tin (Sn), and lead (Pb) as primary components.

Modularization is an important benefit to overall project cost, such as construction period, manpower and logistics. In order to establish a successful modularization strategy, the optimum cost can be realized based on the Envelope Size which is allowed to be transferred to the plant site through analysis of each shape of the module. Through the analysis of the plant structure, the Envelope Size that can be transported on site in units of sizes suitable for maritime and onshore is provided, and finite element method is applied to the existing materials (A36, A572) and domestic materials (SS400, SM490, SWH400) and analyzed the results of the analysis to obtain domestic materials applicable to the plant structure frame.

In this study, the square members which were composed of the aluminum. And the hat- shaped members composed of CFRP and hybrid were used as the specimens. On the lightweight design aspect, the collapse characteristic and energy absorption capability of the each member were analyzed and compared. As the result of this study, the collapse mode of square aluminum member was mixed as axially symmetric and asymmetric mode. The energy was absorbed as the stable collapse mode. The energy was absorbed as the stable collapse mode. The square CFRP and the hat- shaped member became unstable due to the brittle failure with the folding mode. The square hybrid member was stably collapsed with compound folding mode combined two modes. The hat-shaped hybrid member was collapsed with compound mode combined outer CFRP hat-shaped member was collapsed stably by entering the fiber in the folding of square aluminum member and fragmentation mode of CFRP.

본 연구에서는 수렵무늬 접이식 경상(KS-1)과 무궁화무늬 접이식 경상(KS-2) 두 점을 대상으로 제작 기법과 재료 특성을 비교하였다. 근대기 나전칠기의 제작 기법과 재료 운용 특성을 파악하기 위하여 구조 분석과 재질 분석을 실시하였다. X-ray 및 CT 촬영을 통해 내부 목재 구조와 결구 방식을 조사하였으 며, 광학현미경 관찰을 통해 목재 수종을 식별하였다. 또한 FT-IR 분광분석을 통해 도막의 유기 성분을 분석하고, 휴대용 X선 형광분석(P-XRF)을 통해 바탕칠층과 안료의 무기 원소 조성을 확인하였다. 아울러 KS-2 천판 종이층에 대해서는 방사성 탄소 연대 측정을 실시하였다. 분석 결과 두 기물은 팔족안 형식의 다리 구조와 전통 목가구에서 사용되는 짜맞춤 결구 방식을 공유하는 동일한 구조 계통에 속하는 것으로 확인되었다. KS-1은 목재 기질 위에 토분과 호분을 혼합한 광물성 바탕칠층과 우루시올(urushiol) 기반 옻칠 도막으로 이루어진 전통적인 칠기 구조를 보였다. 반면 KS-2는 합판 기질과 중간 종이층이 포함된 구조를 나타냈으며, FT-IR 분석 및 P-XRF 분석 결과 카슈계 도료가 사용되었을 가능성이 제기되었다. 또한 KS-2 천판 종이층의 방사성 탄소 연대 측정 결과 AD 1950년 이후의 modern carbon 값이 확인되었다. 이처럼 두 기물이 동일한 구조 체계를 공유함에도 불구하고 도막 재료와 바탕칠층 구성에서 차이를 보이 는 것은 근대기 나전칠기 제작 시기에 따라 옻칠 공정과 재료 사용에 있어서 기술적 전환 양상을 반영하고 있음을 시사한다.

This study compared the manufacturing techniques and material characteristics of two folding Najeon (mother-of-pearl) lacquered tables: a hunting-pattern (KS-1) and a hibiscus-pattern (KS-2). Structural and material analyses were conducted to understand the production techniques and material application of modern Najeon lacquerware. Internal wooden structures and joinery methods were examined using X-ray and CT, while wood species were identified through optical microscopy. Furthermore, organic components of the coatings were analyzed via FT-IR spectroscopy, and inorganic elements of the ground layers and pigments were identified using portable X-ray fluorescence (P-XRF). Radiocarbon dating was also performed on the tabletop paper layer of KS-2. Results confirmed both objects belong to the same structural lineage, sharing a Paljokan-type leg frame and traditional mortise-and-tenon joinery. KS-1 showed a traditional lacquer structure consisting of a wooden substrate, a mineral ground layer of mixed clay and calcium carbonate, and a urushiol-based coating. Conversely, KS-2 included a plywood substrate and an intermediate paper layer, with FT-IR and P-XRF suggesting the possible use of cashew-based coatings. Radiocarbon dating of this paper layer confirmed a modern carbon value post-dating AD 1950. Despite sharing the same structural system, differences in coating materials and ground-layer composition indicate a technological transition in lacquering processes and material usage during the modern period of Najeon lacquerware production.

In order to revitalize the marine leisure industry, researches on various leisure vessels have been widely conducted in Korea. In particular, in the field of leisure sports, researches and developments for improving the performance of high-speed motorboats are actively progressing. For reducing the weight of motorboats various composite materials are applied to the hull, and these composite materials must ensure structural safety. In this study, the material properties of composite materials applied to tunnel-type motorboats, used in the OSY(Outboard Stock Yamato)-400 race, were evaluated and the structural analysis was performed to examine the safety of the motorboat hull. Material tests were conducted according to Korean Industrial Standard and structural analysis of finite elements model of the motorboat hull was performed under longitudinal bending and torsional load conditions, respectively. By comparing the analysis results with the material test results, it was confirmed that the applied composite material meets the required strength.

본 연구는 압축을 받는 사각부재의 표면에 섬유보강재로 보강했을 때, 횡보강에 의한 구속효과를 파악하기 위해 실험적 연구를 수행하였다. 보강에 사용된 섬유보강재는 바잘트섬유(Basalt fiber)와 PEN섬유(Polyethylene Naphthalate fiber)이다. 바쟐트섬유는 2겹, 4겹, 6겹으로 보강하였으며, PEN섬유는 1겹, 2겹, 3겹으로 보강하였다. 150mm x 150mm인 정사각형 단면이며, 높이는 300mm로 계획하였다. 실험결과, 바잘트 섬유 및 PEN 섬유로 보 강한 실험체는 파괴시 취성파괴가 발생하지 않고, 초기 최대강도 이후 강도가 다소 감소하는 경향을 보이다가 다 시 강도가 상승하는 경향을 보여주어 연성이 크게 증가하였다.

In this study, an experimental study was conducted to understand the lateral constraint effect by transverse reinforcement when reinforcing with fiber reinforcement on the surface of a square member. The fiber reinforcement materials used for test specimens are basalt fiber and polyethylene Naphthalate fiber. Basalt fiber was reinforced with two layers, four layers, and six layers, and PEN fiber was reinforced with one layer, two layers, and three layers. It is a square cross-section with 150mm x 150mm, and the height was planned to be 300mm. As a result of the experiment, the experiment reinforced with bazalt fiber and PEN fiber showed no brittleness destruction during destruction, and the strength tended to decrease slightly after the initial maximum strength, and then increased the strength again, resulting in a significant increase in ductility.

In this study, a thermal-fluid-structure coupled analysis was performed to improve the thermal performance of a burner for a coal gasification power plant. After combustion analysis, an average temperature of 1,400°C was obtained, closely matching the actual coal gasification system environment. The highest burner tip surface temperature, 887°C, was achieved at the analysis variable, a coal fines inflow velocity of 8m/s. This temperature was mapped to a thermal-structural analysis model, and by increasing the radius of the cooling channel inside the burner to 5 mm, the analysis confirmed a reduction in thermal stress of approximately 20%. In particular, changing the material to HP50-Nb resulted in significantly superior cooling efficiency compared to Inconel 718 without any cooling channel design. The results of this study will be useful for the optimal design of coal gasification facilities as well as for improving the durability of the facilities.

Hexagonal bolt, nut, fittings, and high-pressure valves with special alloy play an important role in many industrial products, for instance, such as semiconductor facilities, hydrogen stations and fuel cell electric vehicles. The purpose of this study is to investigate the structural stability of turning wheel using the reaction force of roller in variable hexagonal rolling die. As the results, the bearing groove had the possibility of damage in turning wheel, especially, in case of Bottom condition. Furthermore, the turning wheel showed structural instability by using safety factor but structural stability using strength, respectively, as a safety criterion.

본 연구는 표준실험체인 전단보강근이 없는 철근콘크리트 보 실험체(SSS)와 전단보강근이 있는 철근콘크리트 보 실험체(BSS), 성능개선 실험체인 전단보강근이 없는 철근콘크리트 보에 섬유 혼입율을 변화시킨 고로슬래그미분말이 함유된 고인성섬유 복합모르타르를 타설한 실험체(SHFSC시리즈)로 총 6개의 실험체를 실물크기의 1/2로 축소 제작하여 단조하중을 주어 실험하였다. 실험을 통하여 얻어진 결과를 비교분석하여 하중-변위, 파괴형태, 최대내력, 전단응력 등을 규명함으로써 구조성능을 평가하였다. 고로슬래그미분말이 함유된 고인성섬유 복합모르타르를 활용한 철근콘크리트 보 실험체(SHFSC시리즈)의 경우 전단보강근이 없는 표준실험체(SSS)보다 전단응력은 20%, 연성능력은 5.75배 증가하는 결과를 나타내었다.

In this study, six reinforced concrete beams, without stirrup, using new fiber composite material with ground granulated blast furnace slag(SHFSC Series) and standard specimens without or with stirrup(SSS, BSS) were constructed and tested under monotonic loading. Experimental programs were carried out to evaluate the structural performance of such test specimens, such as the load-displacement, the failure mode, the maximum strength, and the shear strength. All the specimens were modeled in one-half scale size. Test results showed that reinforced concrete beams using new fiber composite material and ground granulated blast furnace slag specimens without stirrup(SHFSC Series) was increased the shear strength carrying capacity by 20%, and the ductility capacity by 5.75 times in comparison with the standard specimen without stirrup(SSS).

Finite Element analysis were carried out to investigate the deformation behaviours of a buckled automotive seat frames made of three different types of materials, i.e., SAPH440, Al6082-T6 and Al7021-T7, when they were subject to external load, based on the ECE R14 regulation to achieve lightweight structure. Also, several thicknesses were applied to the seat frame structures of each material for characterising deformations. It was found that light weight seat frame structure was obtained compared to conventional steel structure when it was made of aluminium under the condition of satisfying ECE R14 regulation. Interpretation result, when changing from SAPHH440 material has a thickness of 1.5mm to Al material has a thickness of 3.0mm, that could checking weight lightening about 47%.

In this paper, as the transport cask was moved in the reactor, the structural integrity on the cask had to be evaluated in the normal transport condition. The drop height of the cask was determined by the weight of the cask in the normal transport condition by regulations about assessment test. It was determined that the drop height of the cask was 1.2 m by regulations. The velocity of the drop impact was calculated to perform the drop impact analysis by the principle of the conservation of energy. Using results of the simulation about the drop impact analysis, the structural integrity assessment on the transport cask was performed by ASME Boiler and Pressure Vessel Code.

본 연구는 표준실험체(BSS), 강판 보강 실험체(BS30), 탄소섬유판 보강 실험체(BCPF, BCPK), 탄소섬유쉬트 보강 실험체(BCFS), 매입형 FRP봉 보강 실험체(BCR 시리즈)로 총 8개의 실험체를 실물크기의 1/2로 축소 제작하여 단조하중을 주어 실험하였다. 실험을 통하여 얻어진 결과를 비교분석하여 하중-변위, 파괴형태, 최대내력, 연성능력 등을 규명함으로써 구조성능의 개선정도를 평가하였다. 실험결과, 매입형 FRP봉 보강 실험체(BCR 시리즈)의 경우 표준실험체(BSS)보다 최대내력은 21~55%, 연성능력은 1.23배 증가하는 결과를 나타내었다. 또한, 부착슬립, 피복분리 형태로 파괴되었지만, 다른 보강재료 보다 연성적인 거동을 나타내었다.

In this study, seven R/C beams, retrofitted steel plate(BS30), carbon fiber plate(BCPF, BCPK), carbon fiber sheet(BCFS), embedded FRP rod(BCR series), and standard specimen(BSS) were constructed and tested under monotonic loading. Experimental programs were carried out to improve and evaluate the structural performance of such test specimens, such as the load-displacement, the failure mode, the maximum strength, and the ductility capacity. All the specimens were modeled in one-half scale size. Test results showed that test specimens, embedded FRP rod(BCR series) were increased the maximum load carrying capacity by 21~55%, and the ductility capacity by 1.23 times in comparison with the standard specimen BSS. And test specimens BCR series were failed with the adhesion slip and concrete cover separation. But it showed enough ductile behavior.