• The Journal of the Korean dental association
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• v.53 no.5
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• pp.368-376
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• 2015

Purpose : The objective of this research was to develop a more simplified drilling procedure with an enhanced implant drill. Materials and Methods : The drill enhanced design factors enabled implantation of Dia. 5.0mm fixture with only 2 times drilling which is more simplified drilling procedure. The enhanced drill was designed with 2 flutes, 2-phase or 3-phase formed drill tip and 25 degrees of helix angle. The proposed drilling procedure (2 times) was compared with a general drilling process (4 times) in terms of temperature changes, cutting time and ISQ value. Results : The simplified drilling procedure indicated less heat than a conventional drilling procedure (p<0.05). The enhanced drill showed significantly shorter drilling time than a conventional drill (p<0.05). On the other hand, higher insertion torque and ISQ value were observed on the the suggested drilling procedure than the conventional drilling procedure (p<0.05). Conclusion : A simplified drilling procedure with the newly designed drill could provide higher effectiveness and safety of dental implant operations under properly controlled external conditions, such as irrigation and RPM of drilling.

• Journal of Power System Engineering
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• v.3 no.2
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• pp.42-50
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• 1999

In recent years, composite materials like CFRP are increasingly used in various fields of engineering because of their unique properties which offer a high strength/density and high modulus/density. When CFRP structures are manufactured in drilling processes which are frequently practiced in an Industry, they bring on the delaminations sometimes. So, acoustic emission(AE) techniques were used for a condition monitoring of the drilling process in CFRP. In this study, the AE from CFRP estimated the delamination which reduces the strength and load carrying capacity under the drilling process and the initial delamination were well caught and measured by a video camera. From the results, it was found the relationships between failure mechanism of CFRP delamination and AE characteristics as like amplitude and count.

• Special Issue of the Society of Naval Architects of Korea
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• 2017.10a
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• pp.32-37
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• 2017

Due to the nature of semi-submergible drilling rig, various equipments are arranged in a limited space, and therefore the many types of outfitting holes passing through the hull structure are densely arranged and that is required the detailed structural strength evaluation in terms of ULS and FLS by class or client. Particularly, semi-submergible drilling rig has a variety of global load which affects the structure strength around holes compared to general commercial ship, and its response of stress is also complicated, so it is difficult to carry out the prediction design of structural strength evaluation and reinforcement. In this regard, this paper presents a case study on the evaluation of structural strength for the various holes and large openings of semi-submergible drilling rig conducted by our company, as well as an established hole verification procedure.

• Journal of the Korean Society of Safety
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• v.16 no.4
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• pp.47-51
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• 2001

The carbon fiber reinforced plastics(CFRP) have been widely used in aircraft and spacecraft structures as well as sports goods because it has high specific strength, high specific stiffness and low coefficient of thermal expansion. Machining of CFRP poses problems not frequently seen for metals due to the nonhomogeneity, anisotropy, and abrasive characteristics of CFRP. Delamination is a common problem faced while drilling holes in CFRP using conventional drilling. Therefore, AE characteristics related to drilling damage process of unidirectional and [0/90/]s crossply laminate composite was studied. Also drilling damage like the delamination was observed by video camera in real time monitoring technique. From the results, we basically found the relationships between the delamination from drilling and AE characteristics for CFRP composites.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.29 no.11 s.242
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• pp.1542-1550
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• 2005

This paper presents the numerical procedure for calculating non-uniform residual stresses based on relieved displacements obtained from incremental hole drilling. The relationship between the in-plane displacement produced by introducing a blind hole and the corresponding residual stress is established. Finite element calculations are described to evaluate the relieved coefficients required for the determination of non-uniform residual stresses. Validity of the proposed method has been tested through three axisymmetric test examples and two three-dimensional examples. As a result of . simulation on the test examples, it is found that this numerical procedure is well adopted to measuring non-uniform residual stress in the full hole depth range of the hole diameter from the surface. The accuracy of the hole drilling method with displacement measurement is discussed, comparing tile method with strain measurement

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• v.42 no.1
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• pp.9-12
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• 2016

Objectives: In this study we evaluated heat generation during the low-speed drilling procedure without irrigation. Materials and Methods: Ten artificial bone blocks that were similar to human D1 bone were used in this study. The baseline temperature was $37.0^{\circ}C$. We drilled into 5 artificial bone blocks 60 times at the speed of 50 rpm without irrigation. As a control group, we drilled into an additional 5 artificial bone blocks 60 times at the speed of 1,500 rpm with irrigation. The temperature changes during diameter 2 mm drilling were measured using thermocouples. Results: The mean maximum temperatures during drilling were $40.9^{\circ}C$ in the test group and $39.7^{\circ}C$ in the control group. Even though a statistically significant difference existed between the two groups, the low-speed drilling did not produce overheating. Conclusion: These findings suggest that low-speed drilling without irrigation may not lead to overheating during drilling.

• Journal of Periodontal and Implant Science
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• v.53 no.1
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• pp.85-95
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• 2023

Purpose: In recent years, guided implant surgery has been widely used for the convenience of patients and surgeons. Further streamlining the surgical procedure would make implant surgery more convenient. Low-speed water-free conditions are often used in guided implant surgery. Therefore, in this study, we attempted to confirm once again whether drilling was safe at a low speed without water. The main purpose of this study was to evaluate whether a simplified drilling protocol that omits some intermediate steps in the drilling process was safe from the viewpoint of heat generation. Methods: D1 density artificial bone blocks were drilled under 50 rpm, 10 N·cm water-free conditions, and the surface temperature was measured using a digital infrared camera. First, drilling was performed with the sequential drilling method, which is the most widely used technique. Second, for each drill diameter, the temperature change was measured while performing simplified drilling with omission of the previous 1, 2, or 3 steps. Results: In sequential drilling, the heat generated during drilling at all diameters was less than the critical temperature of osteonecrosis (47℃) except for the ⌀2 drill. Statistical significance was observed in all groups when comparing sequential and simplified drilling in the ⌀3.2, ⌀3.8, and ⌀4.3 drills (P<0.001). However, in the simplified drilling procedures, the temperature was below the osteonecrosis threshold temperature (47℃) except for the ⌀4.3 drill with the omission of the previous 3 steps (⌀3.0, ⌀3.2, and ⌀3.8). Conclusions: In general, drilling under low-speed, water-free conditions has shown stable results in terms of heat generation. Simplified drilling showed statistically significantly greater heat generation than sequential drilling. However, most of the diameters and omitted steps seem to be clinically acceptable, so it will be useful if an appropriate selection is made according to the patient's clinical condition.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.22 no.2
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• pp.268-277
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• 1998

The numerical procedure for calculating non-uniform residual stress fields by using relieved strain data from incremental hole drilling method is presented. Finite element calculations are described to evaluate the relieved coefficients required for the determination of residual stresses. From the results of simulations it is found that this numerical method is well adopted to measuring non-uniform residual stress in the hole depth range of 0.8 times of the hole diameter from the surface. In order to examine the practicability of this method, the hole drilling procedure for the four point bending test is performed. This method is applied to the measurement of residual stresses in the cold-rolled steel pipe. It is shown that the magnitude of residual stress in the pipe is not negligible when compared with yield stress and the residual stress should be duly considered in designing structures with this pipes.

• Journal of the Korea Concrete Institute
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• v.17 no.4 s.88
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• pp.645-654
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• 2005

This paper presents a nonlinear finite element procedure for the analysis of reinforced and prestressed concrete shells using the four-node quadrilateral flat shell element with drilling rotational stiffness. A layered approach is used to discretize, through the thickness, the behavior of concrete, reinforcing bars and tendons. Using the smeared-crack method, cracked concrete is treated as an orthotropic nonlinear material. The steel reinforcement and tendon are assumed to be in a uni-axial stress state and to be smeared in a layer. The constitutive models, which cover the loading, unloading, and reloading paths, and the developed finite element procedure predicts with reasonable accuracy the behavior of reinforced and prestressed concrete shells subjected to different types of loading. The proposed numerical method fur nonlinear analysis of reinforced and prestressed concrete shells is verified by comparison with reliable experimental results.

• Korean Journal of Computational Design and Engineering
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• v.17 no.3
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• pp.198-207
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• 2012

This paper presents an overview of automated robotic system for skull drilling, which is performed to access for some neurosurgical interventions, such as brain tumor resection. Currently surgeons use automatic-releasing cranial perforators. The drilling procedure must be performed very carefully to avoid penetration of brain nerve structures; however failure cases are reported. The presented prototype system utilizes both preoperative and intraoperative information. Preoperative CT image is used for robot path planning. A NeuroMate robot with a six-DOF force sensor at the end effector is used for intraoperative operation. Intraoperative cutting force from the force sensor is the key information to revise an initial registration and preoperative path plans. Some possibilities are verified by path simulation but cadaver experiments are required for validation of this prototype.