• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• v.27 no.2
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• pp.111-117
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• 2001

There are three designs of thread form in screw type implants: V-thread, Reverse buttress thread and Square thread. The purpose of this study was to find out how thread form designs have an influence on the equivalent stress, equivalent strain, maximum shear stress and maximum shear strain and which design of thread form generates more maximum equivalent stress and strain. 3-D finite element analysis was used to evaluate the stress and strain patterns of three tread types. The results of this study were as follow. 1. Under the 200N of axial load, the value of maximum equivalent stress is smallest in square thread and there is no significant difference between that of V thread and reverse buttress thread. 2. Under the 200N of axial load, the value of maximum equivalent strain is largest in V thread and smallest in square thread. 3. Under the 200N of axial load, the value of maximum shear stress is smallest in square thread and there is no significant difference between that of V thread and reverse buttress thread. 4. Under the 200N of axial load, the value of maximum equivalent strain is largest in V thread and there is no significant difference between that of square thread and reverse buttress thread. 5. Above results show that the square thread has special advantages in stress and strain compared with other thread types, especially in shear stess which is most determinant to implant-bone interface. Considering the superior biomechanical properties of square form implant, we presume that square form implant has better clinical results than the other types of implants in the same clinical conditions.

• Journal of Dental Rehabilitation and Applied Science
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• v.21 no.2
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• pp.153-167
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• 2005

The purpose of this study was to compare the v-shape thread with the square shape thread of fixture in the view of stress distribution pattern using finite element stress analysis. The finite element model was designed with the parallel placement of two standard fixtures(4.0 mm diameter ${\times}$ 11.5 mm length) on the region of mandibular 1st and 2nd molars. Three dimensional finite element model was created with the components of the implant and surrounding bone. This study simulated loads of 200 N at the central fossa in a axial direction (load A), 200 N at the buccal offset load that is 2 mm apart from central fossa in a axial direction (load B), 200 N at the buccal offset load that was 4 mm apart from central fossa in a axial direction (load C). These forces of load A',B',C' were applied to a $15^{\circ}$ inward oblique direction at that same site with 200 N. Von Mises stress values were recorded and compared in the supporting bone, fixture, and abutment screw. The following results have been made based on this study : 1. The highest stress concentration occurred at the cervical region of the implant fixture. 2. Von Mises stress value of off-site region was higher than that of central fossa region. 3. Square shape thread type showed more even stress distribution in the vertical and oblique force than V-shape thread type. 4. Stress distribution was the most effective in the case of buccal offset load (2, 4 mm distance from central fossa) in the square shape thread type. 5. V-shape thread type revealed higher von Mises stress value than square shape thread type in all environmental condition. The results from numerical analyses concluded that square shape thread type had the lower destructive stress and more stress distribution between the fixture and bone interface than V-shape thread type. Therefore, square shape thread type was regarded as optimal thread configuration in biomechanical concepts.

• Journal of the Korea Institute of Military Science and Technology
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• v.10 no.1
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• pp.144-149
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• 2007

Behaviour of a thread joint of a rocket motor case show complex structural characteristics. Pre-torque must be applied to the threads to prevent the loosening of the interface from the additional pressure load. During the pressurization of the rocket motor case, the jointing face may be opened if the pre-torque were not set properly or the structure may be failed if the local concentrated stress exceeds the strength of the material. In this paper, the structural behaviour of a thread joint of a rocket motor case were analyzed by the finite element method and the results were compared to the experimental ones. A method to set a pre-torque for a thread joint were proposed to ensure the structural safety.

• Journal of Advanced Marine Engineering and Technology
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• v.24 no.2
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• pp.8-16
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• 2000

The thread load distribution as applied to large stud bolts for steam turbines is investigated using the finite element method. The stress concentration in tapered threads is studied with varying prestress and taper angle. Based upon the thread load distribution, the optimal taper angles to reduce the stress concentration are determined for various prestresses. The presented finite element model is validated by comparing results of the calculated thread load with analytic ones. The optimal taper angles obtained from this research can be used in designing tapered threads of large stud bolts for steam turbines.

• Transactions of Materials Processing
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• v.19 no.3
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• pp.160-166
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• 2010

In this paper, the process parameters of thread rolling were designed based on the numerical analysis results. Firstly, the effective analysis conditions that guarantee the reliability of the analysis results were found. To find the effective analysis conditions, the analyses were carried out for various numbers of teeth. And then, the effects of the process parameters such as tool shape and temperature on the thread rolling performance were investigated. The formability in thread rolling process was evaluated in terms of Cockcroft-Latham damage value. In order to evaluate formability, Cockcroft-Latham damage value was normalized by the critical damage value which was obtained from the analysis of uniaxial tensile test. The analyses were carried out using DEFORM-3D. The results showed that the flank angle and crest round had an effect on the thread rolling load. It was also shown that temperature had significant effects on the effective strain distribution, rolling load, and damage. With the reduced formability of stainless steel at higher temperature, it was shown that the normalized damage values increased as the process temperature.

• The Journal of Korean Academy of Prosthodontics
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• v.51 no.1
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• pp.1-10
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• 2013

Purpose: The purpose of this study was to find an inclination slope of the screw thread that is favorable in distributing the stresses to alveolar bone by using three dimensional finite element analysis. Materials and methods: Three types modelling changed implant thread with fixed pitch of 0.8 mm is the single thread implant with $3.8^{\circ}$ inclination, double thread implant with $7.7^{\circ}$ inclination and the triple thread implant with $11.5^{\circ}$ inclination. And three types implant angulation is the $0^{\circ}$, $10^{\circ}$ and $15^{\circ}$ on alveolar bone. The 9 modelling fabricated for three dimensional finite element analysis that restored prosthesis crown. The crown center applied on 200 N vertical load and $15^{\circ}$ tilting load. Results: 1. The more tilting of implant angulation, the more Von-Mises stress and Max principal stress is increasing. 2. Von-Mises stress and Max principal stress is increasing when applied $15^{\circ}$ tilting load than vertical load on the bone. 3. When the number of thread increased, the amount of Von-Mises stress, Max principal stress was reduced since the generated stress was effectively distributed. 4. Since the maximum principal stress affects on the alveolar bone can influence deeply on the longevity of the implants. When comparing the magnitude of the maximum principal stress, the triple thread implant had a least amount of stress. This shows that the triple thread implant gave a best result. Conclusion: A triple thread implant to increase in the thread slope inclination and number of thread is more effective on the distribution of stress than the single and double thread implants especially, implant angulation is more tilting than $10^{\circ}$ on alveolar bone. Thus, effective combination of thread number and thread slope inclination can help prolonging the longevity of implant.

• Journal of Dental Rehabilitation and Applied Science
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• v.24 no.1
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• pp.67-76
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• 2008

Implant requires long lasting, strong osseointegration using bio-mechanical interlocking by bone ingrowth. In regarding the size level for bone ingrowth, the micro-patterning would enhance bone response. Micro-patterning can increase the area contacting the bone tissues. Therefore, it may distribute the load to the surrounding bone tissue, more effectively. This study compared and analyzed the load distributing effect with the shape and number of micro-patterning. For the optimal comparison of threads, the assumptions different from general finite element analysis model were made. It was assumed that the implant was axisymmetric and infinitely long. The implant was assumed to be completely embedded in the infinitely long cortical bone and to have 100% bone apposition. The implant-bone interface had completely fixed boundary conditions and received an infinitely big axial load. The condition of threads were as follows. The reference model 1 had conventional thread. Model 2 had 2 micro-patterns on the upper flank of the thread. Model 3 had 2 micro-patterns on the lower flank of the thread. Model 4 had 2 micro-patterns on the upper and lower flanks of the thread. Model 5 had 3 micro patterns on the upper and lower flanks of the thread. The results were as follows: 1. The thread with micro-patterns distributed stress better than the conventional thread. 2. The thread with micro-patterns on the lower flank distributed stress better than that with micro-patterns on the upper flank. 3. The thread with 3 micro-patterns distributed stress better than that with 2 micro-patterns, However, an area with stress concentration occurred.

• Proceedings of the IEEK Conference
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• summer
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• pp.39-41
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• 2004

In this paper, I propose a thread scheduling policy for faster packet processing on the network processors with multithreaded multiprocessor architecture. To implement the proposed policy, I derived several basic parameters related to the thread scheduling and included a new parameter representing the packet contents and the features of the multithreaded architecture. Through the empirical study using a network processor, I proved the proposed scheduling ploicy provides better throughput and load balancing compared to the generally used thread scheduling policy.

• The Journal of Korean Academy of Prosthodontics
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• v.38 no.4
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• pp.526-543
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• 2000

Finite element analyses were performed to study effects on stress distribution generated in jaw bone for various shapes of dental implants: plateau type, plateau with small radius of curvature, triangular thread screw type in accordance with ISO regulations and square thread screw filleted with small radius partially. It was found that square thread screw filleted with small radius was more effective on stress distribution than other dental implants used in analyses. Additional analyses were performed on the implant with square thread screw filleted with small radius for very-ing design parameters, such as the width of thread end, the height of the thread of the implant and load direction, to determine the optimum dimensions of the implant. The highest stress concentration occurred at the region in jaw Pone adjacent to the first thread of the implant. The maximum effective stress induced by a 15 degree oblique load of 100 N was twice as high as the maximum effective stress caused by an equal amount of vertical load. Stress distribution was more effective in the case when the width of thread end and the height of thread were p/2 and 0.46p, respectively, where p is the pitch of thread. At last, using tensile force calculated from the possible insert torque without breading bone thread, finite element analysis was performed on the implant to calculate pre-stress when the primary fixation of the implant was operated in jaw bone. The maximum effective stress was 136.8 MPa which was proven to be safe.

• The Journal of the Institute of Internet, Broadcasting and Communication
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• v.22 no.2
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• pp.71-76
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• 2022

Round-robin is widely used for the scheduling of large-scale parallel workloads in the computing units of GPGPU. Round-robin is easy to implement by sequentially allocating tasks to each computing unit, but the load balance between computing units is not well achieved in multi-workload environments like cloud. In this paper, we propose a new thread block scheduling policy to resolve this situation. The proposed policy manages thread blocks generated by various GPGPU workloads with multiple queues based on their computation loads and tries to maximize the resource utilization of each computing unit by selecting a thread block from the queue that can maximally utilize the remaining resources, thereby inducing load balance between computing units. Through simulation experiments under various load environments, we show that the proposed policy improves the GPGPU performance by 24.8% on average compared to Round-robin.