• Structural Engineering and Mechanics
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• 제37권3호
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• pp.331-349
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• 2011

This study investigates the use of a vibration correlation technique (VCT) to identify the buckling load of a rectangular thin plate. It is proposed that the buckling load can be determined experimentally using the natural frequencies of plates under tensile loading. A set of rectangular plates was tested for natural frequencies using an impact test method. Aluminum and stainless steel specimens with CCCC, CCCF and CFCF boundary conditions were included in the experiment. The measured buckling load was determined from the plot of the square of a measured natural frequency versus an in-plane load. The buckling loads from the measured vibration data match the numerical solutions very well. For specimens with well-defined boundary conditions, the average percentage difference between buckling loads from VCT and numerical solutions is -0.18% with a standard deviation of 5.05%. The proposed technique using vibration data in the tensile loading region has proven to be an accurate and reliable method which might be used to identify the buckling load of plates. Unlike other static methods, this correlation approach does not require drawing lines in the pre-buckling and post-buckling regions; thus, bias in data interpretation is avoided.

• 한국안전학회지
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• 제29권3호
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• pp.1-7
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• 2014

In this study, for the evaluation of the static and fatigue joining strength of the joint, the geometry of the cross-tension specimen was adopted. The specimens were produced with optimal joining force and fatigue life of the clinch joint specimens was evaluated. The material selected for use in this study was cold rolled mild steel (SPCC) with a thickness of 0.8 mm. The maximum tensile load was 708 N for the specimen with single point. The fatigue endurance limit (=42.6 N) per point approached to 6% of the maximum tensile strength at a load ratio of 0.1, suggesting that the joints are vulnerable to cross-tension loading during fatigue. Compared to equivalent stress and maximum principal stress, the SWT fatigue parameter and equivalent strain can properly predict the current experimental fatigue life. The SWT parameter can be expressed as $SWT=2497.5N^{-0.552)_f$.

• Steel and Composite Structures
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• 제21권3호
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• pp.517-536
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• 2016

Thick steel plate is commonly found with mega steel structures but its properties have not been fully explored. Grade Q345GJ-C steel plate with thickness ranging from 60 mm to 120 mm are studied in this paper. Both the static and cyclic performance of material in different directions (horizontal and through-thickness directions) and locations (outer surface, 1/4 thickness and mid-depth) are experimentally obtained. The accumulative damage during cyclic loading is also calculated by using bilinear mixed hardening (BMH) constitutive relationship together with the Lemaitre's damage model. Results show that the static properties are better at the outer surface of thick steel plates than those at mid-depth. Properties in through-thickness direction are similar to those at mid-depth in the horizontal direction. The cyclic performance at different locations of a given plate is similar within the range of strain amplitude studied. However, when damage parameters identified from monotonic tensile tests are included in the numerical simulation of cyclic loading tests, damage is found accumulating faster at mid-depth than close to outer surface.

• 대한토목학회논문집
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• 제9권4호
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• pp.83-92
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• 1989

강성포장(剛性鋪裝)에 대하여 더 좋은 공용성능(供用性能) 기대를 위한 개발과 파손발생에 대한 파손과정에 관하여 포장상태를 조사하게 된다. 본 논문(論文)은 공용중(供用中)인 시멘트콘크리트 포장(鋪裝)의 피로거동(疲勞擧動)과 탄성특성(彈性特性)에 대한 연구결과이다. 공용중(供用中)인 각(各) 포장(鋪裝)의 평균인장강도(平均引張強度)를 측정하기 위하여 Indirect tensile시험을 실시한 것이다. 변형측정(變形測定)은 이러한 특성의 변화 및 콘크리트의 탄성특성(彈性特性)을 구하기 위한 피로(疲勞)시험을 통하여 이루어진 것이다.

• Steel and Composite Structures
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• 제25권6호
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• pp.685-692
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• 2017

In this study, the effect of various adhesively bonded composite patches on mechanical properties of notched Al-Mg alloy plates was analyzed. For this purpose firstly, the un-notched and notched specimens were fabricated from 5086 Al-Mg alloys which have been used in armor-plated military vehicles. The surface notches as a flaw were machined with circular cutting tool to form notch aspect ratio a/c=0.15 and notch-to-thickness ratios a/t=0.5 in the radial direction on the test specimens. Then, various composite patches which reinforced by glass, carbon and Kevlar fibers were bonded adhesively at elliptically surface notches. Finally, experimental measurements conducted by applying tensile static loading. The experimental results showed that repairing with composite patches with order of carbon, glass and Kevlar fibers have remarkable effect on tensile strength of the notched plate. Also the finite element models were developed using Abaqus/Explicit code to predict the tensile strength and elongation of unrepaired notched specimen and specimen repaired by carbon fiber composite patch. The comparison between numerical and experimental results showed good agreement between them and proved the accuracy of numerical modeling.

• Earthquakes and Structures
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• 제20권2호
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• pp.161-173
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• 2021

The structural behavior of a tensile fabric structure, known as hypar, is investigated. Seismic-induced stresses in the fabric and axial forces in masts and cables are obtained using accelerograms recorded at different regions of the world. Time-history analysis using each recording are performed for the hypar by using finite element simulation. It is found that while the seismic stresses in the fabric are not critical for design, the seismic tensile forces in cables and the seismic compressive forces in masts should not be disregarded by designers. This is important, because the seismic design is usually not considered so relevant, as compared for instance with wind design, for these types ofstructures. The most relevant findings of this study are: 1) dynamic axial forces can have an increase of up to twice the static loading when the TFS is subjected to seismic demands, 2) large peak ground accelerations seem to be the key parameter for significant seismic-induced axial forces, but not clear trend is found to relate such forces with earthquakes and site characteristics and, 3) the inclusion or exclusion of the form-finding in the analysis procedure importantly affects results ofseismic stresses in the fabric, but not in the frame.

• 한국공작기계학회:학술대회논문집
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• 한국공작기계학회 2003년도 추계학술대회
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• pp.283-288
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• 2003

The object of this study is to investigate a fracture characteristics of static tensile test as a function of acoustic emission according to the fiber orientation $\theta=0^{\circ}C$ in carbon/epoxy composites, CFRP. On tensile loading, it was recognized that the fracture characteristics of CFRP in a unidirectional composites. Using the results of the AE analysis(a=2mm), it was found that the amplitude distributions of AE signals corresponding the matrix cracking, fiber debonding or delamination, and fiber breaking are 55~70dB(<200sec), 100dB(200~600sec), and 80dB(>600sec).

• International Journal of Precision Engineering and Manufacturing
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• 제9권3호
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• pp.64-67
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• 2008

This study investigated the influence of composite resins with different elastic moduli and occlusal loading conditions on the stress distribution of restored notch-shaped non-carious cervical lesions (NCCL) using 3D finite element analysis. Two different materials, Tetric Flow and Z100, were used as representative flowable hybrid resins for the restoration of NCCL. A static point load of 500 N was applied at the buccal and palatal cusps. The ratios of stress reduction to energy dissipation were better in the compressive state than the tensile state regardless of the restorative material. The total dissipation ratios for Tetric Flow were 1.5% and 4.2% larger than those for Z100 under compression and tension, respectively. Therefore, tensile stress poses more of a risk for tooth fracture, and Tetric Flow is a more appropriate material for restoration.

• 대한토목학회논문집
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• 제8권1호
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• pp.173-185
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• 1988

철근콘크리트 보의 전단피로거동(剪斷疲勞擧動)에 관(關)해 실험적(實驗的)인 연구(硏究)를 실시하여, 수치해석(數値解析) 결과(結果)와 비교(比較) 검토하였다. 전단실험(剪斷實驗)은 정적실험(靜的實驗)과 피로파괴실험(疲勞破壞實驗)으로 구별하였는데, 정적실험(靜的實驗)에서는 3가지 경우의 시험부재(試驗部材) 4개를 제작하여 실험한 결과, 응력과 스터럽의 변형률 관계를 관찰하였고, 피로파괴실험(疲勞破壞實驗)에서는 4가지 경우의 시험부재(試驗部材) 11개를 제작하여 실험한 결과, 하중-중앙처짐 관계와 하중-인장철근 변형률 관계 그리고, 하중-스터럽의 변형률 관계를 관찰하였다. 100 만회(萬回)에 대한 부재(部材)의 피로강도(疲勞强度)는 정적극한강도(靜的極限强度)의 약 65%임을 확인할 수 있었다.

• 한국항공운항학회지
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• 제20권1호
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• pp.103-111
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• 2012

This study reviews several fracture models for predicting the residual strength of notched composite laminates. Representative experimental results on the residual strength of composite laminates containing a notch subjected to static uniaxial tensile loading have been collected from open literature. And notched strength data for T300/5208 are analyzed. The various parameters associated with the fracture models have been determined for laminates. Notched strength data sets are compared with fracture models and the applicability of the different fracture models in predicting the notched strength of composite laminates is discussed. And static tests have been performed on 2.0mm depth notched specimen. And the test results are compared with analysis models.