• Clinics in Shoulder and Elbow
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• v.21 no.4
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• pp.234-239
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• 2018

Background: In elbow fracture-dislocation, partial excision of the comminuted radial head fracture that is not amenable to fixation remains controversial considering the accompanying symptoms. This study was undertaken to evaluate the results of radial head partial excision when the comminuted radial head fracture involved <50% of the articular surface in all-arthroscopic repair of elbow fracture-dislocation. Methods: Patients were divided into two groups based on the condition of the radial head fracture. In Group A, the patients had a radial head comminuted fracture involving <50% of the articular surface, and underwent arthroscopic partial excision. Group B was the non-excision group comprising patients with stable and non-displacement fractures. Follow-up consultations were conducted at 6 weeks and at 3, 6, 12, and 24 months after surgery. Results: In all, 19 patients (Group A: 11; Group B: 8) met the inclusion criteria and were enrolled in the study. At the final follow-up, all 19 patients showed complete resolution of elbow instability. No significant differences were observed in the range of motion, visual analogue scale score, and Mayo elbow performance score between groups. Radiological findings did not show any complications of the radiocapitellar joint. However, nonunion of the coracoid fracture was observed in 3 patients (Group A: 1; Group B: 2), without any accompanying instability and clinical symptoms. Conclusions: Considering that the final outcome is coronoid fracture fixation and lateral collateral ligament complex repair for restoring elbow stability, arthroscopic partial excision for radial head comminuted fractures involving <50% of articular surface is an effective and acceptable treatment for elbow fracture-dislocation.

• Composites Research
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• v.16 no.5
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• pp.15-20
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• 2003

In this paper, the fracture strength of the surface damaged laminates was predicted by applying the fracture strengths of the unflawed and flawed laminates. For prediction, the theoretical equation about the fracture strength of laminates was simplified applying classical laminate theory and was applied to the surface damaged laminates. Lagace's and Tsai's experimental data were used for verifying the theoretical equation. Moreover, to verify the theoretical prediction, an experiment was performed. Surface unflawed laminate and flawed laminates were fabricated and the experiments were made and these results were compared with theoretical predictions. The specimens' fiber direction was same to the tensile direction and the theoretical predictions and the experimental results were showed good agreement. Therefore, by this equation, the fracture strength of structures made of composites will be able to be predicted when the surface of the structures was damaged.

• Journal of Welding and Joining
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• v.2 no.2
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• pp.54-61
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• 1984

Construction of welding structure is greatly dependent upon welding heat cycle. Fracture toughness is decreased remarkablely due to coarse grained HAZ and inequal residual stress of three dimensions to originate in welding. Post weld heat treatment(PWHT) is carried out to increase the fracture toughness of HAZ and to remove the residual stress. There occur some problem such as toughness decrement and stress relief cracking(SRC) in the coarse grained HAZ subject to the effect of tempering treatment. Therefore, in this paper, the effect of heat inputs affecting cooling rate and PWHT under the no stress on fracture toughness were evaluated by crack opening displacement (COD), SEM and micro-hardness test. Experimental results are as follows; 1. Fracture toughness of weld HAZ is dependent upon weld heat cycle and it is decreased with increment of heat input, but the degree of improvement of fracture toughness after PWHT was linearly increased with heat input. 2. Hardness of the parent metal is not changed, but the softening of coarse grained HAZ is remarkable due to PWHT. 3. Fracture surface of as-weld show the perfect brittle fracture with the cleavage fracture, but after PWHT they appear the ductile fracture surface with dimple.

• Transactions of the Korean Society of Automotive Engineers
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• v.7 no.8
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• pp.248-261
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• 1999

The fatigue life of mechanical components and structures has been influenced by mechanical, material and environmental conditions. It is important to search out the load type and size for accurate cause of fracture at the damaged surface of material. The fractographic method by x-ray diffraction can utilize residual stress $\sigma$_r and half-value breadth B and find out the types and the mechanical conditions of fracture. This study showed the relationship between fracture mechanical parameters $\Delta$K, $K_{max}$ and X-ray residual stress $\sigma$_r for normalized SS41 steel with homogeneous crystal structure and M.E.F. dual phase steel(martensite encapsulated islands of ferrite). The fatigue crack propagation tests were carried out under stress ratios 0.1 and 0.5. The x-ray diffraction technique according to crack propatation direction was applied to fatigue fractured surface. Residual stress $\sigma$_r was independent on stress ratios by arrangement of $\Delta$K. The equation of $\sigma$_r$\Delta$K was established by the experimental data. Therefore, fracture mechanical parameters can be estimated can be estimated by the measurement of X-ray parameters.

• Journal of the Korean Arthroscopy Society
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• v.2 no.1
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• pp.93-96
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• 1998

We treated 10 cases of the medial malleolar fracture of the ankle by open reduction and internal fixation from June 1997 to December 1997. After the rigid internal fixation, we measured the gap of the fracture site and the step off of the articular surface by special instrument under the ankle arthroscopy whether it was reduced anatomically or not. And we tried to know the necessity of the arthroscopically assisted reduction and fixation in the medial malleolar fracture of the ankle. Under the arthroscopic view, all 10 cases were anatomically reduced as less than 1 mm of gap of the fracture site and less than 1mm of step off of the articular surface after open reduction and internal fixation in the medial malleolar fractures. In conclusion, through the arthroscopic management, it has advantage in finding and treating the accompanying intraarticular lesion, but also has disadvantage in setting the arthroscope and prolonging the operation time.

• Tribology and Lubricants
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• v.15 no.2
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• pp.141-149
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• 1999

Fracture, fatigue and wear characteristics of Al-Si alloy used for compressor are experimentally studied. Plane strain fracture toughness test is carried out using three point bending specimen. Fatigue test is performed under constant loading condition and wear test is carried out as a function of sliding velocity and applied load. To obtain the crack propagation characteristics and wear mechanism of Al-Si alloy, fracture and worn surfaces are investigated using SEM. It is verified that fracture and fatigue strength of Al-Si alloy are improved by the fine microstructure of alloy. The wear behavior and specific wear amount of Al-Si alloy are not dependent on the microstructure but on a function of the silicon content. Anodizing on the surface of Al-Si alloy, surface hardness and wear characteristics are improved.

• Proceedings of the Korea Concrete Institute Conference
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• 2004.11a
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• pp.595-602
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• 2004

In this study, the roughness of fracture surfaces in cementitious material has been characterized by roughness number (RN). A systematic experimental investigation was carried out to examine the dependency of fracture parameters on the aggregate sizes as well as the loading rates. Three aggregate sizes (0.1875 in, 0.5 in, and 0.75 in) and two loading rates (slow and fast loading rate) were used. A total of 52 compression tests and 53 tension tests were performed. All fracture parameters exhibited an increase, to varying degrees, when aggregates were added to the mortar matrix. The fracture surfaces of the specimens were digitized and analyzed. Fracture roughness was monotonically increased as maximum aggregate sizes increase.

• Journal of the Korean Society for Precision Engineering
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• v.17 no.12
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• pp.76-81
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• 2000

Analysis on failure of the panel glass under mechanical shock is the main topic of this study. Since the glass for the LCD panel is thin, it needs to be designed to have enough toughness against mechanical shock. In this paper, a process of estimating fracture of the panel glass is proposed to guarantee reliability of the product. The fracture toughness of the panel glass is used as a criterion of the fracture based on an experimental approach. The stress intensity factor was calculated considering a model with the largest initial crack size on a cut surface and with the boundary force obtained from a dynamic finite element analysis. Critical surface roughness on the cut surface of a typical glass panel, to prevent fracture in case of bending mode, is obtained.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.11
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• pp.2771-2776
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• 2000

In this work, the effect of surface treatment of prepreg on the mode I fracture behavior was studied. Unidirectional (0-deg) double cantilever beam (DCB) specimens were used for fracture tests. Two groups of DCB specimens were made: the first group was made of prepregs surface-treated by Ar(sup)+ ion beam under oxygen environment and the second group was made of regular prepregs. For both groups, fracture resistance curve (R-curve) was determined and compared to each other, Results showed that resistance behavior of the first group is better than that of the second group. That is, mode I fracture toughness, G(sub)Ic of the first group is 24% larger than that of the second group. SEM examination shows that the improvement of G(sub)Ic is due to the increase of interfacial strength between plies.

• The Journal of Korean Academy of Prosthodontics
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• v.39 no.2
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• pp.171-183
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• 2001

The purpose of this study was compare the fracture strength of the IPS Empress ceramic crown according to the occlusal depth (1.5mm, 2.0mm, 2.5mm) and axial inclination ($4^{\circ},\;8^{\circ},\;12^{\circ}$) of the upper first molar. After 10 metal dies were made for each group, the IPS Empress ceramic crowns were fabricated and were cemented with resin cement. The cemented crowns mounted on the testing jig were inclined 30 degrees and a universal testing machine was used to measure the fracture strength. The results of this study were as follows: 1. The fracture strength of the ceramic crown with 2.5mm depth and $8^{\circ}$ inclination was the highest (1393N). Crowns of 1.5mm depth and $4^{\circ}$ inclination had the lowest strength (1015N) 2. There were no significant differences of the fracture strength according to occlusal depth and axial inclination. 3. Most fracture lines began at the loading area and extended through proximal surface perpendicular to the margin, irrespective of occlusal depth. 4. There was positive correlation between the fracture strength and the fracture surface area of crowns.