• Journal of the Korean Society for Precision Engineering
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• v.12 no.12
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• pp.64-71
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• 1995

This investigation evaluates dynamic fracture characteristics of two alloy steels (STD-11 and STS-3) and a gray cast iron (GC-30). The dynamic fracture toughness of crack initiation and some of the dynamic fracturing characteristics were evaluated by using the instrumented Charpy impact testing procedures. It was found from experimental results for three kinds of materials that inertia force is directly proportional to impact velocity. The duration time of inertia force was found to be constant regardless of impact velocities in steel specimens.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.30 no.3
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• pp.220-226
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• 1994

In this paper the failure mechanisms of polypropylene resin composites filled with calcium carbonate particulates have been studied in the temperature range $-50^{\circ}C$ to $-50^{\circ}C$ The fillers used are both untreated and surface treated with stearic acid. The impact fracture toughness is evaluated from the impact energy absorbed divided by the uncut ligament area of the specimen. Impact fracture toughness increases as temperature is raised whether the fillers are coated or not. The static fracture toughness of these particular composites is evaluated based on the linear clastic fracture toughness of these particular composites is evaluated based on the linear clastic fracture mechanics. Static fracture toughess decreases with increasing temperature whether the fillers are coated or not. An extended stress whitened zone are observed through a large number of availabel sites for cavitation/debonding along particle matrix interface and matrix deformation.

• Journal of Korea Foundry Society
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• v.33 no.2
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• pp.63-68
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• 2013

Generally, metal is the most important material used in many engineering applications. Therefore, it is important to understand and predict the damage of metal as result of the impact. The objective of this research is to evaluate the damage criterion on the impact performance of A356 Al-alloy castings. Both experimental method and computational analysis were used to achieve the research objective. In this paper, we performed impact test according to various impact velocities to the A356 cast aluminium specimen for damage prediction. Impact computational simulation was done by applying properties obtained from the tensile test, and damages was predicted according to the damage criteria based plastic work. The good agreement of the results between the experiment and computer simulation shows that the reliability of the proposed FE simulation method to predict fracture of A356 casting components by impact.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2014.11a
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• pp.139-140
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• 2014

The purpose of this study in to evaluate relationship between mechanical properties of materials and fiber type by reinforced fiber with high-velocity impact fracture behavior of fiber reinforced concrete. As a result, for fracture behavior by high-velocity impact, it is considered that impact fracture behavior is not affected by static mechanical properties directly but affected by fiber type and density of the number of fiber. It is necessary to consider type, shape, mechanical properties and the number of fiber with flexural and tensile performance for the evaluation on impact resistance performance of fiber reinforced concrete.

• Structural Engineering and Mechanics
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• v.28 no.6
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• pp.749-765
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• 2008

Free axisymmetric vibrations of layered cylindrical shells of variable thickness are studied using spline function approximation techniques. Three different types of thickness variations are considered namely linear, exponential and sinusoidal. The equations of axisymmetric motion of layered cylindrical shells, on the longitudinal and transverse displacement components are obtained using Love's first approximation theory. A system of coupled differential equations on displacement functions are obtained by assuming the displacements in a separable form. Then the displacements are approximated using Bickley-spline approximation. The vibrations of two-layered cylindrical shells, made up of several types of layered materials and different boundary conditions are considered. Parametric studies have been made on the variation of frequency parameter with respect to the relative layer thickness, length ratio and type of thickness variation parameter.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.26 no.5
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• pp.835-842
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• 2002

In this paper, static and fatigue bending strengths and failure mechanisms of CFRP (carbon fiber reinforced plastics) laminates having impact damages have been evaluated. Composite laminates used for this experiment are CF/EPOXY orthotropy laminated plates, which have two-interfaces $[0^0_ 4/90^0_4]_{ sym}$. A steel ball launched by the air gun collides against CFRP laminates to generate impact damages. The damage growth during bending fatigue test is observed by the scanning acoustic microscope (SAM) and also, the fracture surfaces were observed by using the SEM (scanning electron microscope). In the case of impacted-side compression, fracture is propagated from the transverse crack generated near impact point. On the other hand, fracture is developed toward the impact point from the edge of interface-B delamination in the case of impacted-side tension. Eventually, failure mechanisms have been confirmed based on the observed delamination areas and fracture surfaces.

• Proceedings of the Safety Management and Science Conference
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• 2001.05a
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• pp.311-317
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• 2001

The notched Charpy and Izod impact tests are the most prevalent techniques used to characterize the effects of high impulse loads on ploymeric materials. An analysis method for rubber toughened PVC is suggested to evaluate critical strain energy release rates(Gc) from the Charpy impact energy measurements. An Instrumented Charpy Impact tester was used to extract ancillary information concerning fracture properties in addition to total fracture properties and maximum critical loads. The stress intensity factor Kd was computed for varying amounts of rubber contents from the obtained maximum critical loads and also toughening effects were investigated as well.

• Archives of Craniofacial Surgery
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• v.18 no.1
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• pp.25-29
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• 2017

Background: Many authors have evaluated the post-reduction result of nasal bone fracture through patient satisfaction or postoperative complications. However, these results are limited because they are subjective. The aim of this study was to correlate an objective operation result with patient satisfaction and postoperative complications according to the type of nasal bone fractures. Methods: Our study included 313 patients who had isolated nasal bone fractures and had undergone a closed reduction. Postoperative outcomes were evaluated objectively using computed tomographic (CT) images, while patient satisfaction was evaluated one month after the operation. The correlation of the operation result with patient satisfaction was then evaluated. Results: The correlation between the operation result and patient satisfaction was highest for the lateral impact group type I (LI) type of fracture and lowest for the comminuted fracture group (C) type of fracture. However, there were no statistically significant differences in correlation between the overall result and patient satisfaction by fracture type. The complication rate of lateral impact group type II (LII), C, and frontal impact group type I (FI) fractures were statistically significantly higher than that of frontal impact group type II (FII) and LI fractures. There were no statistically significant relationships between the prevalence of complications and septal fracture or deviation according to the fracture type. In the total group, however, there was a statistically significant difference in complication rate by septal fracture. Conclusion: We found that the CT outcomes correlated with patient satisfaction. The complication rate of LII, C, and FI fractures were statistically significantly higher than that of FII and LI fractures. Septal fracture/deviation increased the postoperative complication in the total group.

• Archives of Craniofacial Surgery
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• v.18 no.1
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• pp.30-36
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• 2017

Background: Nasal fractures have a tendency of resulting in structural or functional complications, and the results can vary according to the type of nasal bone fracture. The aim of this study was to evaluate the objective postoperative results according to the type of nasal bone fractures. Methods: We reviewed 313 patients who had a closed reduction of nasal bone fracture. The classification of nasal bone fracture by Stranc and Robertson was used to characterize the fracture type: frontal impact group type I (FI), frontal impact group type II (FII), lateral impact group type I (LI), lateral impact group type II (LII), and comminuted fracture group (C). For each patient, we tried to use the same axial image section of computed tomographic (CT) scans before and immediately after operation. Postoperative outcomes were classified into 4 grades: excellent (E), good (G), fair (F), and poor (P). We also analyzed postoperative complications by fracture type. Results: Regarding the postoperative CT images, 189 subjects showed E results, 99 subjects showed G, 18 subjects showed F, and 7 subjects showed P reduction. The rate of operation results graded as E by each fracture type was 66.67% in FI, 52.0% in FII, 64.21% in LI, 62.79% in LII, and 21.74% in C. Complications of FI (7.14%), LII (13.95%), and C (13.04%) groups occurred more than in the FII (4.00%) and LI (4.21%) groups. Conclusion: It seems that the operation result by fracture type was better in the FI, LI, and LII type than the FII and C type; after one month, however, LII type showed more complications than other types. The septal fracture can be thought to affect early reduction results in nasal bone fractures.

• Korean Journal of Materials Research
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• v.34 no.7
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• pp.330-340
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• 2024

Al-Mg-Si alloys are light weight and have excellent corrosion resistance, and are attracting attention as a liner material for high-pressure hydrogen containers in hydrogen fuel cell vehicles. Because it has excellent plastic hardening properties, it is also applied to car body panel materials, but it is moderate in strength, so research to improve the strength by adding Si-rich or Cu is in progress. So far, the authors have conducted research on the intergranular fracture of alloys with excessive Si addition from the macroscopic mechanical point of view, such as specimen shape. To evaluate their impact tensile properties, the split-Hopkinson bar impact test was performed using thin plate specimens of coarse and fine grain alloys of Al-Mg-X (X = Cr,Si) alloy. The effect of the shape of the specimen on the characteristics was studied through finite element method (FEM) analysis. As a result, it was found that the intergranular fracture of the alloy with excessive Si depended on the specimen width (W)/grain size (d), which can be expressed by the specimen size and grain size. As W/d decreases, the intergranular fracture transforms into a transgranular fracture. As the strain rate increases, the fracture elongation decreases, and the fracture surface of the intergranular fracture becomes more brittle. It was confirmed that intergranular fracture occurred in the high strain rate region even in materials with small grain sizes.