• Journal of the Korea Institute of Military Science and Technology
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• v.25 no.6
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• pp.553-560
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• 2022

This study investigates improvement of torsional strength of special wrench for K-series self-propelled howitzer power-pack maintenance. In order to maintain the power-pack, special wrench is one of the essential tools for assembling/disassemblimg the engine and transmission. However, failures(plastic deformation, fracture phenomenon and etc.) have been frequently reported even though special wrench was used within recommended standard torque range. Therefore, in this study, finite element analysis using ABAQUS was performed and modification of design parameters have been proposed. Prototypes based on the proposed parameters were manufactured and torsional experiment(torque about 130 % of recommend maximum torque) validated the newly proposed design parameters. Special wrench based on this study is applied to mass production and currently used for the maintenance.

• Proceedings of the KSME Conference
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• 2001.11a
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• pp.258-265
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• 2001

Turbine blade is subject to force of three type ; torsional force by torsion-mount, centrifugal force by rotation of rotor and cyclic bending force by steam pressure. Cyclic bending force of them is main factor on fatigue fracture. In the X-ray diffraction method, the change in the values related to plastic deformation and residual stress near the fracture surface mat be determined, and information of internal structure of material can be obtained. Therefore, to find a fracture mechanism of torsion-mounted blade in nuclear plant, based on the information from the fracture surface obtained by fatigue test, the correlation of X-ray parameter and fracture mechanics parameter was determined, and then the load applied to actual broken turbine blade parts was predicted. Failure analysis is performed by finite element method and Goodman diagram on torsion-mounted blade.

• Journal of the korean Society of Automotive Engineers
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• v.13 no.6
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• pp.101-108
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• 1991

During torsional fatigue of externally cracked cylindrical specimen, crack face rubbing may occur. At this time, normal contact forces arise when shear displacements cause the crack faces to be wedged open due to mismatch of the fracture surface asperities. These normal forces, in turn, generate friction force which act in opposition to the applied shear stresses and reduce the effective stress intensity factor. The premise of the proposed work is that friction and wedging can be studied by measuring the shear and normal displacement across the crack mouth. We have measured the crack mouth compliance using the new biaxial extensometer.

• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 2009.05a
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• pp.306-309
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• 2009

The influence of equal-channel angular pressing (ECAP) route on dynamic deformation behavior of ultra-fine grained Al-4.4%Mg alloys was investigated in this study. The 8-pass ECAPed specimens consisted of ultra-fine grains of $0.5{\mu}m$ in size, and contained the considerable amount of second phase particles, which were fragmented and distributed homogeneously in the matrix. The result of dynamic torsional tests indicated that the maximum shear stress and fracture shear strain were lowest in the specimen deformed by ECAP via route A among the 8-pass ECAPed specimens. The formation of adiabatic shear bands was addressed by concepts of critical shear strain, deformation energy required for void initiation, and microstructural homogeneity related to ECAP routes.

• Transactions of the Korean Society of Automotive Engineers
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• v.13 no.5
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• pp.127-133
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• 2005

Rotary swaging is one of the incremental forming process which is a chipless process using the reduction of cross-sections of bars, tubes and wires. The TDS(Tube Drive Shaft) of monobloc used in automotive has been developed by the rotary swaging process. The mechanical characteristics of swaged parts such as the hardness, thickness and roughness are also estimated to conduct experimental analyses of rotary swaging process with the materials of 34Mn5 Furthermore the change in the vibration mode of TDS due to design parameters, which are the tube length, diameter and thickness, has been investigated and analysed. The weight of the TDS product is smaller by about $12.8\%$ than that of SDS with the same performance. It could be evidently found that the TDS is designed to be much lighter than SDS (Solid Drive Shaft). This advantage might give some possibility to improve the NVH (Noise-Vibration-Harshness) characteristics. A maximum torque and a total number of torsional repetitions for the TDS is checked and measured to know the torsional intensity and fatigue strength through the static torsion test and torsional durability test, respectively. A total number of the torsional repetitions up to the fracture for the TDS is greater than 250,000 times.

• Journal of Biomedical Engineering Research
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• v.33 no.4
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• pp.213-222
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• 2012

While much has been learned about the mechanisms of metastatic spread of cancer to bone, there has been little headway in establishing guidelines for monitoring the alteration in bone quality and estimating fracture risk. The aims of this study are, therefore, 1) to evaluate bone quality induced by metastatic bone tumor by analyzing the characteristics on bone microarchitecture and degree of bone mineralization and 2) analyze fracture risk increased secondary to the bone quality changes by metastatic bone tumor through calculating mechanical rigidities based on in-vivo micro CT images. For this study, eighteen female SD rats (12 weeks old, approximate 250 g) were randomly allocated in Sham and Tumor groups. W256 (Walker carcinosarcoma 256 malignant breast cancer cell) was inoculated in the right femur (intraosseous injection) in Tumor group, while 0.9% NaCl (saline solution) was injected in Sham group. The right hind limbs of all rats were scanned by in-vivo micro-CT to acquire structural parameters and degree of bone mineralization at 0 week, 4 weeks, 8 weeks, and 12 weeks after surgery. At the same time, urine was collected by metabolic cages for a biochemical marker test in order to evaluate bone resorption. Then, bone metastasis had been directly identified by positron emission tomography. Finally, axial, bending and torsional rigidities had been calculated based on in-vivo micro CT images for predict fracture risk. The results of this study showed that metastatic bone tumor might induce significant decrease in bone quality and increase of fracture risk. This study may be helpful to monitoring a degree of bone metastasis and predicting fracture risk due to metastatic bone tumor. In addition, this noninvasive diagnostic methodology may be utilized for evaluating other bone metabolic diseases such as osteoporosis.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1997.10a
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• pp.816-819
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• 1997

The operation of femoral non-union after IM(Intramedullary) nailing in distally femoral fractures is considered. Augmentive plate fixation is the management of femoral non-union after IM nailing. The purpose of this study is to compare the bending, torsional stiffness and stress distribution of the two operations by the FEM(Finite Element Method). Augmentive plate fixation is better than IM nail fixation. These results conclude that plate augmentation is a useful method for the unstable femoral non-union after interlocking IM nailing.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2000.11a
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• pp.489-493
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• 2000

Turbine blade has trouble of cracking at root region. Fracture surface of blade root is surveyed by SEM and AFM to clear relation between fracture mechanical parameter and surface parameter (striation width and surface roughness). Service stress is predicted by maximum height roughness $R_{max}$, on fractured surface and stress analysis on turbine blade. It is to thought that turbine blade is fractured by abnormal condition such as incorrect fittings between pin and pin hole but isn't fractured by normal service conditions such as steam pressure, centrifugal force and torsional force.

• Korean Journal of Metals and Materials
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• v.46 no.9
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• pp.563-571
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• 2008

The influence of annealing treatment on dynamic deformation behavior of ultra-fine grained aluminum alloys was investigated in this study. After equal-channel angular pressing at $200^{\circ}C$, most of the grains were considerably reduced to nearly equiaxed grains of $0.3{\mu}m$ in size. With an increment of various annealing treatments for 1 hour, resultant microstructures were found to be fairly stable at temperatures up to $200^{\circ}C$, suggesting that static recovery would be dominantly operative, whereas grain growth was pronounced above $250^{\circ}C$. The tensile test results showed that yield and ultimate tensile strengths decreased, but elongation-to-failure and strain hardening rate increased with increasing annealing temperature. The dynamic deformation behavior retrieved with a series of torsional tests was explored with respect to annealed microstructures. Such mechanical response was analyzed in relation to resultant microstructure and fracture mode.

• Restorative Dentistry and Endodontics
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• v.45 no.2
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• pp.22.1-22.10
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• 2020

Objectives: This study investigated the influence of glide path size and operating kinetics on the time to reach the working length and the fracture resistance of Twisted File (TF) and Endostar E3 files. Materials and Methods: A total of 120 mandibular single-rooted premolars were selected. Two methods of kinetic motion (TF adaptive and continuous rotary motion) and file systems (TF and Endostar E3) were employed. The files were used in root canals prepared to apical glide path sizes of 15, 20, and 25. The time taken to reach the working length and the number of canals used before the instrument deformed or fractured were noted. Fractured instruments were examined with scanning electron microscopy. Results: The TF system took significantly more time to reach the working length than the Endostar E3 system. Both systems required significantly more time to reach the working length at the size 15 glide path than at sizes 20 and 25. A greater number of TFs than Endostar E3 files exhibited deformation, and a higher incidence of instrument deformation was observed in adaptive than in continuous rotary motion; more deformation was also observed with the size 15 glide path. One TF was fractured while undergoing adaptive motion. Conclusions: No significant difference was observed between continuous rotary and adaptive motion. The TF system and adaptive motion were associated with a higher incidence of deformation and fracture. Apical glide path sizes of 20 and 25 required significantly less time to reach the working length than size 15.