• Transactions of the Korean Society of Mechanical Engineers A
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• v.25 no.3
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• pp.381-389
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• 2001

The objective of this paper is to evaluate the fracture resistance characteristics of SA508 Cl.1a to SA508 Cl.3 welds manufactured for the reactor coolant loop piping system of nuclear power plants. The effect of the crack plane orientation to the welding process orientation and the preheat temperature on the fracture resistance characteristics were discussed. Results of the fracture resistance test showed that the effect of the crack plane orientation to the welding process orientation of the fracture toughness is significant, while that of preheat temperature on the fracture toughness is negligible. The micro Vickers hardness test, the metallographic observation and the fractography analysis were conducted to analyse the crack jump phenomenon on the L-R crack plane orientation in the multi-pass welding zone. As these results, it is shown that the crack jump phenomenon was produced because of the inhomogeneity between welding beads and the crack plane orientation must be considered for the safety of the welding zone in the piping system.

• Clinics in Shoulder and Elbow
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• v.12 no.2
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• pp.240-244
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• 2009

Purpose: This study examined the outcomes of closed reduction and fixation of the coracoid process fracture using a suture anchor in a patient with combined acromioclavicular dislocation for which the coraco-clavicular ligament was intact. Materials and Methods: A 26 year-old male patient with a coracoid process fracture that was associated with a type III acromioclavicular joint dislocation was operated on with anchor suture fixation. This is the first trial of this operative procedure. Results: At the postoperative follow-up at 3 months, complete union of the coracoid process fracture was seen. The shoulder had a full range of motion and the shoulder function was normal. Conclusion: Closed reduction and fixation using one suture anchor for treating coracoid process fracture is a safe, effective procedure.

• Transactions of Materials Processing
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• v.7 no.6
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• pp.562-569
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• 1998

The limit drawing ratio (LDR) is a major process parameter in the process design of deep drawing. If the actual drawing ratio is greater than the LDR for a particular stage then an intermediate stage has to b added the process sequence to avoid failure during the drawing operation and the optimal process design considering for the first-drawing and redrawing by using finite element method combined with ductile fracture criterion. From the results of finrte element analysis the optimal value of drawing ratio is obtained which contributes to the more uniform distribution of thickess and the smaller values of the ductile fracture infinal cup.

• Journal of the Korean Society for Precision Engineering
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• v.15 no.5
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• pp.110-119
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• 1998

Dynamic cutting force variations in milling process were measured indirectly using spindle motor current. Magnitude of the spindle motor current is independent of cutting direction. Quasi-static sensitivity of the spindle motor current is higher than that of the feed motor current. Dynamic sensitivity of the spindle motor current is lower but cutting force was correctly represented by spindle RMS current in rough milling. In rough milling, chipping and tool fracture were well detected by the proposed tool fracture index using spindle motor current.

• Computers and Concrete
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• v.24 no.1
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• pp.51-61
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• 2019

Compressive ability is one of the most important mechanical properties of concrete material. The compressive failure process of concrete is pretty complex with internal tension, shear damage and friction between cracks. To simulate the complex fracture process of concrete at meso level, methodology for meso-structural analysis of concrete specimens is developed; the zero thickness cohesive elements are pre-inserted to simulate the crack initiation and propagation; the constitutive applied in cohesive element is established to describe the mechanism of crack separation, closure and friction behavior between the fracture surfaces. A series of simulations were carried out based on the model proposed in this paper. The results reproduced the main fracture and mechanical feature of concrete under compression condition. The effect of key material parameters, structure size, and aggregate content on the concrete fracture pattern and loading carrying capacities was investigated. It is found that the inner friction coefficient has a significant influence on the compression character of concrete, the compression strength raises linearly with the increase of the inner friction coefficient, and the fracture pattern is sensitive to the mesostructure of concrete.

• Structural Engineering and Mechanics
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• v.71 no.1
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• pp.65-75
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• 2019

In this article, the dynamic fracture instability characteristics, including dynamic crack propagation and crack branching, in PMMA brittle solids under dynamic loading are investigated using the discrete element method (DEM) simulations. The microscopic parameters in DEM are first calibrated using the comparison with the previous experimental results not only in the field of qualitative analysis, but also in the field of quantitative analysis. The calibrating process illustrates that the selected microscopic parameters in DEM are suitable to effectively and accurately simulate dynamic fracture process in PMMA brittle solids subjected to dynamic loads. The typical dynamic fracture behaviors of solids under dynamic loading are then reproduced by DEM. Compared with the previous experimental and numerical results, the present numerical results are in good agreement with the existing ones not only in the field of qualitative analysis, but also in the field of quantitative analysis. Furthermore, effects of dynamic loading magnitude, offset distance of the initial crack and initial crack length on dynamic fracture behaviors are numerically discussed.

• Journal of the Korean Society for Precision Engineering
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• v.13 no.3
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• pp.94-101
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• 1996

This paper presents an investigation of the ability of the scheme to simultaneously accomplish both prediction of fracture initiation and analysis of deformation in cold forged products. The Cockcroft-Latham criterion which is successfully applied to a variety of loading situations is used in the present investigation to estimate if and where surface and internal fracture occur during the deformation process. The numerical predictions and experimental results of two types of fundamental cold metal forming process taken into account are compared. Finite element simulation combined with fracture criterion has successfully predicted the site of surface or internal fracture initiation and corresponding to level of deformation observed experimentally.

• Transactions of the Korean Society of Mechanical Engineers
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• v.17 no.5
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• pp.1172-1182
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• 1993

In orthogonal machining a quantitative model for burr formation process and fracture when tool exits workpiece is proposed. When no fracture during burr formation burr formation process is divided by three parts; Initiation, Development and Final burr formation. According to the properties of workpiece fracture will happen or not after initiation of burr formation. Considering the fact that fracture depends on the ductility of workpiece, the fracture strain obtained from ductile fracture criterion is used for prediction. It is verified that the fracture strain from tension test can be used as fracture criterion in burr formation without large error. For detailed observation of burr formation an experimental stage for micro orthogonal cutting inside SEM (Scanning Electron Microscope) is built. Through the comparison between model prediction and experimental result from orthogonal machining in milling machine the model is verified.

• Proceedings of the KSME Conference
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• 2001.11a
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• pp.87-92
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• 2001

In this paper, high strength pressure vessel steels having the same chemical compositions were manufactured by the two different steel-making processes, such as vacuum degassing(VD) and electro-slag remelting(ESR) methods. After the steel-making process, they were normalized at $955^{\circ}C$, quenched at $843^{\circ}C$, and finally tempered at $550^{\circ}C$ or $450^{\circ}C$, resulting in tempered martensitic microstructures with different yielding strengths depending on the tempering conditions. Low-cycle fatigue(LCF) tests, fatigue crack growth rate(FCGR) tests, and fracture toughness tests were performed to investigate the fatigue and fracture behaviors of the pressure vessel steels. In contrast to very similar monotonic, LCF, and FCGR behaviors between VD and ESR steels, a quite difference was noticed in the fracture toughness. Fracture toughness of ESR steel was higher than that of VD steel, being attributed to the removal of impurities in steel-making process.

• Journal of the Korean Society for Precision Engineering
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• v.17 no.4
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• pp.22-28
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• 2000

By using the finite element method, the Oyane's ductile fracture integral I was calculated from the histories of stress and strain according to every element and then the forming limit of hydroforming process could be evaluated. The fracture initiation site and the forming limit for two typical hydroforming processes, tee extrusion and bumper rail under different forming conditions are predicted in this study. For tee extrusion hydroforming process, the pressure level has significant influence on the forming limit. When the expansion area is backed by a supporter and bulged, the process would be more stable and the possibility of bursting failure is reduced. For bumper rail, the ductile fracture integral i is not only affected by the process parameters, but also by the shape of preforming blank. Due to no axial feeding on the end side of the blank, the possibility of cracking in hydroforming of the bumper rail is influenced by the friction condition more strongly than that of the tee extrusion. All the simulation results show reasonable plastic deformation, and the applications of the method could be extended to a wide range of hydroforming processes.