• Transactions of the Korean Society of Mechanical Engineers A
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• v.40 no.5
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• pp.513-523
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• 2016

The stress concentration factors and stress intensity factors for a simple beam and a cantilever are analyzed by using finite element method and phtoelasticity. Using the analyzed results, the estimated graphs on stress concentration factors and stress intensity factors are obtained. To analyze stress concentration factors of notch, the dimensionless notch length H(height of specimen)/h=1.1~2 and dimensionless gap space r(radius at the notch tip)/h=0.1~0.5 are used. where h=H-c and c is the notch length. As the notch gap length increases and the gap decreases, the stress concentration factors increase. Stress concentration factors of a simple beam are greater than those of a cantilever beam. However, actually, the maximum stress values under a load, a notch length and a gap occur more greatly in the cantilever beam than in the simple beam. To analyze stress intensity factors, the normalized crack length a(crack length)/H=0.2~0.5 is used. As the length of the crack increases, the normalized stress intensity factors increase. The stress intensity factors under a constant load and a crack length occur more greatly in the cantilever beam than in the simple beam.

• Structural Engineering and Mechanics
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• v.75 no.5
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• pp.559-569
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• 2020

In the present study, the fracture toughness of U-shaped notches made of aluminum alloy Al7075-T6 under combined tension/out-of-plane shear loading conditions (mixed mode I/III) is studied by theoretical and experimental methods. In the experimental part, U-notched test samples are loaded using a previously developed fixture under mixed mode I/III loading and their load-carrying capacity (LCC) is measured. Then, due to the presence of considerable plasticity in the notch vicinity at crack initiation instance, using the Equivalent Material Concept (EMC) and with the help of the point stress (PS) and mean stress (MS) brittle failure criteria, the LCC of the tested samples is predicted theoretically. The EMC equates a ductile material with a virtual brittle material in order to avoid performing elastic-plastic analysis. Because of the very good match between the EMC-PS and EMC-MS combined criteria with the experimental results, the use of the combination of the criteria with EMC is recommended for designing U-notched aluminum plates in engineering structures. Meanwhile, because of nearly the same accuracy of the two criteria and the simplicity of the PS criterion relations, the use of EMC-PS failure model in design of notched Al7075-T6 components is superior to the EMC-MS criterion.

• Journal of Advanced Marine Engineering and Technology
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• v.31 no.7
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• pp.857-862
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• 2007

A novel compact ultra wideband(UWB) antenna for UWB application is proposed in this paper. The proposed antenna with $22mm{\times}26mm{\times}1.6mm$ covers the entire UWB bandwidth and has band notch characteristic for the frequency band of $5.15{\sim}5.825GHz$ limited by WLAN. The antenna has a concaved ground plane and staircase shape patch to achieve the wide bandwidth, and has an U shape slot with $\lambda/4$ length to notch the band. The return loss and group delay of the proposed antenna are measured.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.7 no.5
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• pp.120-126
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• 1998

Second step shot peening was applied on both smooth specimen and U-notch specimen in order to investigate the stress distribution and the improvement in fatigue strength. Various experiments and measurements such as rotary bending fatigue test and the measurement of compressive residual stress were performed. The results showed that the fatigue strength of second step shot peened specimens increased by 34 percent compared to that of unpeened ones. Compressive residual stress also considerably increased, which resulted in the increase of fatigue strength. finite element analysis showed that shot peening is effective in decreasing the bending stress by external force. The effectiveness of shot peening in reducing the compressive residual stress was anticipated by the superposition of the concentrated stress and the compressive residual stress.

• The Journal of Korean Institute of Electromagnetic Engineering and Science
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• v.16 no.2 s.93
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• pp.199-203
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• 2005

In this paper, a novel compact and frequency band-notch antenna for Ultra-Wideband(UWB) applications is proposed. The designed antenna not only shows good impedance bandwidth for ultra-wideband but has band notch characteristic for the frequency band of $5.15\~5.825\;GHz$ limited by IEEE 802.1la and HIPERLAN/2. To achieve both properties of wide band and band notch, the techniques of a concaved ground plane and inserted U-shaped thin slot into planar radiator are used respectively. A manufactured antenna satisfied VSWR<2 for the frequency band of $2.95\~11.7\GHz$ except the limited band of $4.92\~5.866\;GHz$.

• Structural Engineering and Mechanics
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• v.74 no.5
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• pp.601-609
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• 2020

In this article, the Strain Energy Density (SED) averaged over a well-defined control volume at a notch edge was applied in combination with the Equivalent Material Concept (EMC) to assess the fracture behaviors of some keyhole-notched specimens made of a High-Density Polyethylene (HDPE-PE80) material under mixed-mode loading conditions. An experimental program was performed and 54 new experimental data were totally provided. Additionally, different loading mode ratios were regarded by changing the inclination angles of the notches with respect to the applied load directions. The results obtained from the determined criteria were in good agreement with those of the experimental data.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.25 no.1
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• pp.89-95
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• 2016

This study investigated the design factors of the opening area in order to consider the kinematic stability of a valve plate, conducting an analysis of the reduction effects of pressure pulsation and flow ripple depending on the design factors, using the $SimulationX^{(R)}$ (Germany) hydraulic analysis program. Further, we performed a structure analysis to confirm the kinematic stability of the valve plate in a swash plate type piston pump, and analyzed the effects of pulsation on a 1-step V-type notch, 2-step V-type notch, and 2-step U-type notch to determine the effects of pulsation reduction. Finally, we show the effectiveness of our proposed design of the pre-compression sections on a valve plate in terms of low pulsation by using the hydraulic analysis program, $SimulationX^{(R)}$.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.30 no.1
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• pp.45-52
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• 1994

The study was conducted to evaluate reliability of the longitudinal tensile properties of unidirectional carbon fiber reinforced composites. Two kinds of carbon fiber reinforced composites laminates were tested in order to examine the factors of variability and have the information concerning reliability improvement. Temperature dependence of the strength and its variability were investigated by means of testing at two kinds of temperatures. Statistical distributions of the respective mechanical properties were obtained from the tensile tests. As a result, strength of composites was directly proportional to the ultimate strain and was not proportional to the elastic modulus. The fracture behavior in bending of notched plate was studied for a composite material. The uniform bending tests of notched plates have been carried out for a wide range of notch radii. The experiment shows that the nominal stress at failure decreased with decreasing notch radius and it approaches a constant value when the notch radius is less than about 0.3mm. The critical maximum stress is governed by notch root radius alone in the case of a constant thickness of specimen.

• Journal of electromagnetic engineering and science
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• v.16 no.1
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• pp.35-43
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• 2016

A compact ultra-wide band antenna with a quadruple band-notched characteristic is proposed. The proposed antenna consists of a slotted trapezoid patch radiator, an inverted U-shaped band stop filter, a pair of C-shaped band stop filters, and a rectangular ground plane. To realize the quadruple notch-band characteristic, a U-shaped slot, a complementary split ring resonator, an inverted U-shaped band stop filter, and two C-shaped band stop filters are utilized in this antenna. The antenna satisfies the -10 dB reflection coefficient bandwidth requirement in the frequency band of 2.88-12.67 GHz, with a band-rejection characteristic in the WiMAX (3.43-3.85 GHz), WLAN (5.26-6.01 GHz), X-band satellite communication (7.05-7.68 GHz), and ITU 8 GHz (8.08-8.87 GHz) signal bands. In addition, the proposed antenna has a compact volume of $30mm{\times}33.5mm{\times}0.8mm$ while maintaining omnidirectional patterns in the H-plane. The experimental and simulated results of the proposed antenna are shown to be in good agreement.

• Journal of the Institute of Convergence Signal Processing
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• v.9 no.2
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• pp.141-145
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• 2008

When the current flows to parallel lines with different length, it is researched that the radiation is occured by the common-mode current radiates, and the small light weight antenna composed of dual elements by using the principle is proposed. However, there is a problem in production about this antenna because this liner antenna is structured by combining with wires. In this paper, we improved this liner antenna, and designed the plane antenna composed of dual elements with different length in the plane printed board to produce and to design easily. Furthermore, the antenna with the wide-band characteristic is also designed in the same board. The radiation pattern is similar to the dipole antenna on account of designing the triangular patch S, the notch and two tapers in patch S, the notch and two tapers in the antenna element. In result, it was able to design the antenna working wider band-width(the bandwidth ratio about 58%, $VSWR{\le}2$).