• Transactions of the Korean Society of Mechanical Engineers
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• v.17 no.2
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• pp.313-330
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• 1993

The propagating crack problems under dynamic plane mode in orthotropic material is studied in this paper. To analyze the dynamic fracture problems in orthortropic material, it is important to know the dynamic stress components and dynamic displacement components around the crack tip. Therefore the dynamic stress components of dynamic stress field and dynamic displacement components of dynamic displacement field in the crack tip of orthotropic material under the dynamic load and the steady state in crack propagation were derived. When the crack propagation speed approachs to zero, the dynamic stress component and dynamic displacement components derived in this study are identical to the those of static state. In addition, the relationships between dynamic stress intensity factor and dynamic energy release rate are determinded by using the concept of crack closure closure energy with the dynamic stresses and represented according to physical properties of the orthotrophic material and crack speeds. The faster the crack velocity, the greater the stress value of stress components in crack tip. The stress value of the stress component of crack tip is greater when fiber direction coincides with the crack propagation than when fider direction is normal to the crack propagation.

• Journal of Advanced Marine Engineering and Technology
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• v.33 no.4
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• pp.533-538
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• 2009

The magnitude of constraint effect $A_2$ values on the non-linear elastic plastic fracture toughness was experimentally estimated by using displacement at various measuring positions near crack tip. Constraint effect $A_2$ value was dependent on specimen configuration and on the measured displacement near crack front. The crack tip opening displacement in the vicinity of the crack tip front should be estimated within plastic region when appropriately constraint effect was calculated. It was found that the magnitude of constrain effect |$A_2$| is below 8.0 at the crack tip. But an appropriate location to measure the effective constraint effects $A_2$ at the critical value of J that crack initiation is characterizable by is r = 2mm and ${\theta}=90^{\circ}$ away from original crack tip, and the constraint effect |$A_2$| estimated is 5.3.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• v.27 no.5
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• pp.417-422
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• 2001

Objective: In many TMD cases, deformed and reduced condyle heads were frequently observed. This study was prepared to compare the dimensions between normal and symptomatic condyles, using MR images. Materials: One hundred and twenty one patients with clinical signs and MRI-confirmed diagnosis of disc displacement were selected for this study. Thirty eight TMJs from nineteen asymptomatic volunteers who had no clinical symptoms and no disc displacement on sagittal and coronal view of MRI, were served as normal. Methods: Symptomatic condyles were classified according to the severity of the anterior disc displacement. The amount of anterior disc displacement was evaluated at sagittal section, and they were classified into 4 groups as normal(N), little(G0), mild(G1), moderate(G2) and severe displacement(G3). The dimentions of condyle were measured at the 200% magnified view, by digitizing program. All dimensions were compared among each groups on the central section of sagittal and coronal views, and the statistical analysis was performed. Results: The mean value of anteroposterior length of normal condyle was $0.79{\pm}0.13cm$ at sagittal section and mediolateral length was $2.12{\pm}0.22cm$ on coronal section. The mean value of anteroposterior length of symptomatic condyle was $0.67{\pm}0.16cm$ at sagittal section and mediolateral length was $1.97{\pm}0.28cm$ on coronal section. Conclusions: The size of symptomatic condyle was smaller than normal TMJ. The size of condyle was decreased as the amount of the disc displacement was increased. The dimensional change was found on the anterior articular surface of condyle at the mild or moderate disc displacement. And at the case of severe disc displacement, dimensional change was found on the superior articular surface.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2001.04a
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• pp.756-759
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• 2001

The purpose of this paper is to investigate the buckling and dynamic characteristics for the cylindrical shell under shear loading. To do this, a vibration model tests and analyses and static buckling analyses were performed for the reduced scale model of nuclear reactor vessel. From the results of vibration modal analysis with the pre-shear displacement loads, it is known that the beam vibration mode is not affected by the shear displacement, however shell vibration modes are significantly affected by it. As the pre-shear displacement increases to the critical buckling displacement, the 1st shell vibration frequency in greatly reduces and approaches to zero value.

• Structural Engineering and Mechanics
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• v.29 no.6
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• pp.659-671
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• 2008

A procedure to analyse the space frame structure fixed at base as well as resting on sliding bearing using total or absolute displacement in dynamic equation is developed. In the present method, the effect of ground acceleration is not considered as equivalent force. Instead, the ground acceleration is considered as a known value in the acceleration vector at degree of freedom corresponding to base of the structure when the structure is in non-sliding phase. When the structure is in sliding phase, only a force equal to the maximum frictional resistance is applied at base. Also, in this method, the stiffness matrix, mass matrix and the damping matrix will not change when the structure enters from one phase to another. The results obtained from the present method using absolute displacement approach are compared with the results obtained from the analysis of structure using relative displacement approach. The applicability of the analysis is also demonstrated to obtain the response of the structure resting on sliding bearing with restoring force device.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.5 no.4
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• pp.121-128
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• 1996

In order to examine spindle deformation characteristics that affects the performance of dynmic cutting acuracy due to tool weight variation in a experimental spindle. thermal deformation value of operrative spindle by the axial displacement and the radial run out was measured according to the rise of spindle temperature through the laps of operation time and the change of rotational speed under the tool weight variation. A qualitative summary is as follows ; 1) The results show that the tool weight affcets the spindle temperature variation in a experimental spindle. 2) Radial run out and axial displacement was measured according to the rise of the spindle temperature and the performance of dynamic cutting accuracy was affected by the tool weight variation. 3) Axial displacement is 1.3 times larger than the radial run out in a experimental spindle conditions. 4) Axial displacement is continuously elongated when the tool weight is repeatly exchanged since the spindle themal deformaion, however, when the same tool weight is used. the displacement is still constant.

• The Journal of Advanced Prosthodontics
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• v.14 no.2
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• pp.70-77
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• 2022

PURPOSE. This study evaluated screw loosening and 3D crown displacement after cyclic loading of implant-supported incisor crowns cemented with original titanium bases or with three compatible, nonoriginal components. MATERIALS AND METHODS. A total of 32 dental implants were divided into four groups (n = 8 each): Group 1 used original titanium bases, while Groups 2-4 used compatible components. The reverse torque value (RTV) was evaluated prior to and after cyclic loading (1,200,000 cycles). Samples (prior to and after cyclic loading) were scanned with a microcomputed tomography (micro-CT). Preload and postload files were superimposed by 3D inspection software, and 3D crown displacement analysis was performed using root-mean-square (RMS) values. All datasets were analyzed using one-way ANOVA and Tukey's post hoc analysis. RESULTS. Significant variations were observed in the postload RTV, depending on the titanium base brand (P < .001). The mean postload RTVs were significantly higher in Groups 1 and 2 than in the other study groups. While evaluating 3D crown displacement, the lowest mean RMS value was shown in the original Group 1, with the highest RMS value occurring in Group 4. CONCLUSION. Within the limitations of this in vitro study and under the implemented conditions, it was concluded that the manufacturer brand of the titanium base significantly influenced screw loosening following the fatigue test and influenced 3D crown displacement after cyclic loading.

• Transactions of the Korean Society of Mechanical Engineers
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• v.17 no.2
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• pp.331-341
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• 1993

The propagating crack problems under dynamic antiplane mode in orthotropic material is studied in this paper. To analyze the dynamic fracture problems by theoretical method or experimental method in orthotropic material, it is important to know the dynamic stress intensity factor in the vicinity of crack tip. Therefore the dynamic stress field and dynamic displacement field with dynamic stress intensity factor of orthotropic material in mode III were derived. When the crack propagation speed approachs to zero, the dynamic stress components and dynamic displacement components derived in this paper are identical to the those of static state. In addition, the relationships between dynamic stress intensity factor and dynamic energy release rate are determined by using the concept of crack closure energy with the dynamic stresses and dynamic displacements derived in this paper. Finally, the characteristics of crack propagation are studied with the properties of orthotropic material and crack speed. The variation of angle .alpha. between fiber direction and crack propagating direction and crack propagation speed fairly effect on stress component and displacement component in crack tip. The influence of crack propagation speed on the speed on the stress and displacement is greater in the case of .alpha.=90.deg. than in the case of .alpha.=0.deg. and the faster the crack propagation speed, the greater the stress value and displacement value.

• Structural Engineering and Mechanics
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• v.48 no.3
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• pp.367-382
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• 2013

Different types of long slender pile shall buckle with weak soil and liquefied stratum surrounded. Different from considering single side earth pressure, it was suggested that the lateral earth pressure can be divided into two categories while buckling: the earth pressure that prevent and promotes the lateral movement. Active and passive earth pressure calculation model was proposed supposing earth pressure changed linearly with displacement considering overlying load, shaft resistance, earth pressure at both sides of the pile. Critical buckling load calculation method was proposed based on the principle of minimum potential energy quoting the earth pressure calculation model. The calculation result was contrasted with the field test result of small diameter TC pile (Plastic Tube Cast-in-place pile). The fix form could be fixed-hinged in the actual calculation assuring the accuracy and certain safety factor. The contributions of pile fix form depend on the pile length for the same geological conditions. There exists critical friction value in specific geological conditions that the side friction has larger impact on the critical buckling load while it is less than the value and has less impact with larger value. The buckling load was not simply changed linearly with friction. The buckling load decreases with increased limit active displacement and the load tend to be constant with larger active displacement value; the critical buckling load will be the same for different fix form for the small values.

• Journal of the Korean Society for Precision Engineering
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• v.1 no.1
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• pp.50-58
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• 1984

In the present paper are calculated and compared the stresses on the normal tools and the restricted tools which have three various rake angles by Least Square Method. The results obtained are summerized as follows. The tool displacement at rake angle .alpha. = 12 .deg. and .alpha. = 0 .deg. is positive value in the principal cutting direction and negative value in the feed direction. At rake angle .alpha. = -12 .deg. the displacement is negative value in both of directions. The principal stress of the restricted and normal tool is maximum at the tip of the tool, the shear stress is maximum after a certain distance from the tip. The result of FEM and P.E method shows that in the range of rapid decreasing of normal stress of the tool edge, the shear stress is maintaining a certain value. This is due to the friction characteristic of the chip.