• Journal of Biosystems Engineering
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• v.1 no.1
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• pp.64-72
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• 1976

This experimental work was carried out to investigate the fatigue bending strength on various shapes and sizes of notches of the domestically manufactured steel plate. The notch types tested were a circular hole, U-and V-notches. The S-N diagram for different notch shapes were discussed in relation to plan bending strength and stress concentration factor of notches .The results of the experiments are summarized as follows : (1) The difference between stress concentration factor and notch factor was greater as the radium of notch root became smaller, and these values approached to an identical value as the radium of notch root increased. (2) It was shown that the plane bending fatigue limit of bar without notch for the hotrolled steel having the tensile strength of 33.1kg/$mm^2$was 17.0kg/$mm^2$. (3) U-and V-notch had a greater effect of stress concentration factor on the endurance limit, but O-hole showed the same effect only for $\o\pm2mm$. (4) For the same radius of notch root, U-notch showed a lower value of fatigue limit compared to V-notch and O-hole.

• Tunnel and Underground Space
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• v.17 no.3 s.68
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• pp.216-224
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• 2007

Blasting, using shock and dynamic energy of explosive, is very effective tunnel excavation method. But it had serious problem which is the blast vibration and over-break. In recent study, pre-cracked excavation method using notch hole reduced blast vibration and over-break in tunnel, so we performed study about developing notch bit system for making notch hole. In order to make notch hole effectively we had perform drilling experiments changing length and height of notch and in order to improve speed and precision of drilling we had developed notch bit system which consists of drilling bit, notch bit, adapter and notch guide.

• Journal of the Korean Society for Precision Engineering
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• v.33 no.10
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• pp.865-873
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• 2016

The aim of this study was to examine the validity of fracture criterion for PMMA plates that have a V-notch with an end hole. The predicted stress intensity factors and crack initiation angles by the fracture criterion based on the maximum circumferential stress and the novozhilov's criteria were compared with the experimental results. By increasing the radius of end hole, the differences of predicted stress intensity factors and experimental results increased, possibly due to the plastic zone size. The results indicated that when the radius of end hole is < 1 mm, the fracture criterion would be useful.

• Explosives and Blasting
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• v.26 no.1
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• pp.57-66
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• 2008

It has been proven that the pre-cracking notches in a blasting hole are applicable to control crack growth along specific direction. This study compared the roughnesses of the fracture plane resulting from test blasts using a regular charge hole and notched charge hole to investigate the effect of the notches of charge hole on the formation of fracture plane. A notch bit system was used to drill the notched hole in the rock specimens. The surfaces of the fracture planes were reconstructed as Digital Elevation Model (DEM) using digital photogrammetric method and the roughnesses of the surfaces were estimated with Surface Roughness Profile Index (SRp).

• Proceedings of the KSME Conference
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• 2001.11a
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• pp.278-285
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• 2001

Aluminum/Aramid Fiber Reinforced Plastic(Al/AFRP) laminates are applied to the fuselage-wing intersection. The main objective of this study was to evaluate the delamination zone behavior of Al/AFRP with a saw-cut and circular hole using average stress criterion and the effect of notch geometry. Mechanical tests were carried out to determine the cyclic-bending moment and delamination zone observed ultrasonic C-scan pictures. In case of Al/AFRP containing saw-cut specimen, the shape and size of the delamination zone formed along the fatigue crack. However, in case of Al/AFRP containing circular hole specimen, the shape and size of delamination zone formed two types. first type, delamination zone formed along the fatigue crack. Second type, not observed fatigue crack. Therefore, delamination zone was formed dependently of the circular hole shape.

• Journal of the Korea Convergence Society
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• v.9 no.2
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• pp.177-182
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• 2018

In this paper, the fracture behaviour at CFRP laminated structure due to the vertical falling impact of the fight drone frame composed of CFRP was investigated through the analytical study. As CFRP consists of fiber differently from the existing plastic material, the fracture behaviour becoms complex. So, the preceding study is important through the analytical study before this experiment. By comparing with the existing study model at the same condition as the result of this study, the applied stress value is shown to decrease greatly at the analysis model with the center notch hole of the laminated CFRP drone frame. On the basis of this study result, the esthetic sense can be shown as the foundation data about the notch hole of drone frame are grafted onto the convergence technique.

• Tunnel and Underground Space
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• v.20 no.1
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• pp.65-72
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• 2010

Crack-controlled blasting method which utilizes notched charge hole has been proposed in order to achieve smooth fracture plane and minimize the excavation damage zone. In this study, the blast models, which have a notched charge hole, were analyzed using dynamic fracture process analysis software to investigate the effect of the geometry of a notched charge hole and decoupling indexes of the charge hole on crack growth control in blasting. As a result, crack extension increased and damage crack decreased with the notch length. Ultimately, stress increment factors and resultant fracture patterns with different notch length and width were analyzed in order to examine the effect factors on the crack growth controlling in rock blasts using a notched charge hole.

• Structural Engineering and Mechanics
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• v.81 no.2
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• pp.243-258
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• 2022

In this paper, tensile behavior of joint filling has been investigated under experimental test and numerical simulation (particle flow code). Two concrete slabs containing semi cylinder hole were prepared. These slabs were attached to each other by glue and one cubic specimen with dimension of 19 cm×15 cm×6 cm was prepared. This sample placed in the universal testing machine where the direct tensile stress can be applied to this specimen by implementing a special type of load transferring device which converts the applied compressive load to that of the tensile during the test. In the present work, two different joint filling thickness i.e., 3 mm and 6 mm were prepared and tested in the laboratory to measure their direct tensile strengths. Concurrent with experimental test, numerical simulation was performed to investigate the effect of hole diameter, length of edge notch, filling thickness and filling length on the tensile behavior of joint filling. Model dimension was 19 cm×15 cm. hole diameter was change in four different values of 2.5 cm, 5 cm, 7.5 cm and 10 cm. glue lengths were different based on the hole diameter, i.e., 12.5 cm for hole diameter of 2.5 cm, 10 cm for hole diameter of 5 cm, 7.5 cm for hole diameter of 7.5 cm and 5 cm for hole diameter of 10 cm. length of edge notch were changed in three different value i.e., 10%, 30% and 50% of glue length. Filling thickness were changed in three different value of 3 mm, 6 mm and 9 mm. Tensile strengths of glue and concrete were 2.37 MPa and 6.4 MPa, respectively. The load was applied at a constant rate of 1 kg/s. Results shows that hole diameter, length of edge notch, filling thickness and filling length have important effect on the tensile behavior of joint filling. In fixed glue thinks and fixed joint length, the tensile strength was decreased by increasing the hole diameter. Comparing the results showed that the strength, failure mechanism and fracture patterns obtained numerically and experimentally were similar for both cases.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2010.05a
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• pp.1339-1340
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• 2010

• Journal of Welding and Joining
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• v.16 no.3
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• pp.64-73
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• 1998

This paper is concerned with defects detection and evaluation of heat affected zone (HAZ) in austenitic stainless steel type 304 by ultrasonic wave and neural network. In experiment, the reflected ultrasonic defect signals from artificial defects (side hole, vertical hole, notch) of HAZ appears as beam distance of prove-defect, distance of probe-surface, depth of defect-surface on CRT. For defect classification simulation, neural network system was organized using total results of ultrasonic experiment. The organized neural network system was learned with the accuracy of 99%. Also it could be classified with the accuracy of 80% in side hole, and 100% in vertical hole, 90% in notch about ultrasonic pattern recognition. Simulation results of neural network agree fairly well with results of ultrasonic experiment. Thus were think that the constructed system (ultrasonic wave - neural network) in this work is useful for defects dection and classification such as holes and notches in HAZ of austenitic stainless steel 304.