• Proceedings of the KOSOMBE Conference
• /
• v.1997 no.11
• /
• pp.511-514
• /
• 1997

The objective of this study is to propose a finite element based design of the dental implant replacing unction and shape of natural teeth. For this, geometric actors were varied to investigate stress distribution of the alveolar bone around dental implant. In this study, the results were obtained based on the theory of linear elastic, with geometrically axisymmetric assumption. Geometric actors determining implant shape are ranged as 0.2mm-0.6mm, 0.04mm-0.1mm, 0.46mm-0.84mm or height of thread, radius of curvature of thread, and pitch, respectively. The stresses in the alveolar bone caused by biting force playa major role in determining implant stability. Especially, the stress concentration in the cortical bone causes bone resorption and finally makes the implant unstable. Therefore, the stress distributions were investigated on the side of the alveolar bone focusing on the area of cortical bone. The maximum von Mises stress was found to increase up to 6% as the height of thread increases, while its value was to decrease to 19% when the radius of curvature increase within the assigned ranges. For the variation of pitch, the larger size of pitch results in greater maximum von Mises stress when the length of the implant under consideration is fixed. The existence of the neck below the shoulder did not affect the stress distribution in the region of alveolar bone. However, the stresses on the side of the implant near the neck were found to be different by 20% approximately. Therefore, the neck can provide the stability of the implant against continuing biting movement. As a conclusion, the finite element based study shows a potential in designing the dental implant systematically.

• The Journal of Korean Academy of Prosthodontics
• /
• v.35 no.1
• /
• pp.181-210
• /
• 1997

The stress distribution generated in the surrounding bone was calculated and compared for various geometry of the dental implants by means of the finite element methods. The models were designed to represent the screw type endosseous implants(varing the size, shape, direction of the screw thread and the angle of the body) with supporting bone and the cylinder type endosseous implants(varing the lower portion-Round type, tapered type) with supporting bone. Static mean bite forces were applied 100N vertically and 25N horizontally on the center of the implant and three dimensional finite analysis was undertaken using software ANSYS 5.1 Version. The result demonstrated that different implant shape leads to significant variations in stress distribution in the bone. In the case of variation of the screw size, direction and shape the implant model with normally directional and triangular screw implied lower stress than with upper directional or lower directional and quadrangular screw but among models a different screw size, within a variation of 0.2mm there was no meaningful difference in maximum stress. In the case of variation of angle of body the straight implied lower stress than the tapered. As a result of analysis of cylinder type, the implants with larger radius of curvature of the round form and larger diameter of the tapered form implied lower stress.

• Proceedings of the Korean Society of Rheology Conference
• /
• 2001.06a
• /
• pp.11-14
• /
• 2001

Our study have aimed to identify the deformation and breakup mechanism of minor phase in polymer blends under uniaxial enlongational flow. Experimentally, we measured the transient elongational viscosity of PS/HDPE blends using the uniaxial elongational rheometer at two temperatures. And we observed the evolution of blend morphology with elongation time. Morphological change was observed by quenching the specimen after deformation. If the viscosity variation of PS was compared with that of HDPE at each temperature, PS showed larger temperature dependence than HDPE. At 155$^{\circ}C$, the dispersed phase of larger size were easily affected by affine deformation. The initial spherical shape changed to flat ellipsoid at first, then flat ellipsoid to bulbous shape, and bulbous to thin thread and its satellites. But dispersed phase of smaller size showed the change from sphere to ellipsoid. At 175$^{\circ}C$, the dispersed phase were mostly deformed from spherical shape to ellipsoid. As a result, the morphological change of dispersed phase in elongational deformation is affected by chain flexibility and viscosity ratio. We need to further study to make sure the mechanism of elongation of viscoelastic polymer blends.

• Journal of Dental Rehabilitation and Applied Science
• /
• v.22 no.1
• /
• pp.55-74
• /
• 2006

The external contour of an implant can have significant effects on the load transfer characteristics and may result in different bone failure rates for different implant system. The purpose of this study was to investigate the effects of crest module shape and occlusal load direction on bone failure modes of five commercially available dental implant systems. Five different implant systems with internal connection; ITI (Model 1), Astra (Model 2), Bicon (Model 3), Friadent (Model 4), and Paragon (Model 5), comparable in size, but different in thread profile and cest module shapes, were compared using the finite element method. Conclusively, in the internal connection system of the implant-abutment connection methods, the stress-induced pattern at the supporting bone according to the abutment connection form had differenence among them, and implants with narrowing crestal module cross-sections at the top of the cortical bone created more favorable load transfer characteristics in this region. But it is considered that the future study is necessary about how this difference in the magnitude of the stress have an effect on the practical clinic.

• Transactions of Materials Processing
• /
• v.29 no.3
• /
• pp.157-162
• /
• 2020

Blind rivet nuts are increasingly used in automotive for the joining of sheets. Their application, however, requires appropriate design guides to prevent catastrophic events arising from the failure of joints. In this study, the shaft shape of a frequently used M8 blind rivet nut is optimized based on 3D numerical analysis of the blind rivet nut considering the characteristics of thread. The thread needs to be modeled to suitably consider the fastening of the M8 bolt after the crimping process. FE analysis showed that while the friction in the contact between crimp flange and plate has no significant effect on the crimp geometry, shaft thickness (t) and shaft height (h) are the most significant design variables. The parameter study including various combinations of t and h reveals that they affect the gap (the distance between the crimped flange and the plate that develops through riveting) and the load acting on the plate. The gap is an indicator of the tightening force. It is found that t is inversely proportional to the gap, and proportional to the load, whereas h is proportional to the gap and inversely proportional to the load. Based on our FE analysis results, we propose the range 0.062 < t/h < 0.1 to ensure sufficient fastening (high clamping load, small gap) of the M8 blind rivet nut. The design guide for determining the t/h ratio proposed in this study can be used for general quantitative analysis of the size and the t/h ratio of blind rivet nuts.

• Maxillofacial Plastic and Reconstructive Surgery
• /
• v.29 no.5
• /
• pp.429-438
• /
• 2007

Transport distraction osteogenesis has been introduced recently to correct skeletal malformations and discrepancies in the maxillofacial area. To reconstruct 3-dimensitonal mandibular shape, this transport distraction can be considered with the use of reconstruction plate. A 23-years-old male having unilateral mandibular body and angle defects, who had been operated of partial mandibular resection due to unicystic ameloblastoma, was treated by transport distraction procedures with ThreadLock transport $distractor^{(R)}$ (KLS Martin Co., Germany) through the rail of reconstruction plate (Osteomed Co., USA). After being distracted 35 mm defect from mandibular angle to body, and consolidated for 16 weeks, allogenic bone graft on docking site was performed with removal of transgingival pin. For more than 13 weeks follow up period after consolidation period, gradual increase of radiopacity in the radiographic examination was shown, and the curved mandibular continuity according to the reconstruction plate was made firmly. These transport distraction osteogenesis in the mandible was able to be considered as the good and minimally invasive technique for the reconstruction of mandibular discontinuity. Young patient was also very satisfactory for these results.

• 보존과학연구
• /
• s.26
• /
• pp.41-56
• /
• 2005

A set of horse bit from the Eonnam-ri site consists of three parts, pyo , ham , andinsu , and each part takes a shape of a piece of bar. According to current typological study, the pyo is S type, the insu is two-braided line type, and the outer rim of the ham is double rim type, respectively. According to X-ray test, inlaid design seems to have been decorated on the whole surface of the iron bit, originally. However, inlaid pattern partially remained. While the part of bit stopper is designed with flame pattern, the part of rein joint is designed with cloud pattern. According to XRF and XGT analysis of inlaid material, the content of silver is not more than 50%. The line inlay method making grooves on the surface of iron, then in laying a silver thread into them, and grinding the surface in a direction was adoptedin the manufacture of the iron bit.

• Korean Journal of Animal Reproduction
• /
• v.11 no.3
• /
• pp.206-217
• /
• 1987

Testes from the drake and the gander have been examined by the electron microscopy in thin sections in order to examine the spermiogenesis and the structure of spermatozoa. The spermiogenesis can be divided into three stages: early spermatid, nuclear elongation, and matured spermatid. In the early spermatid of the drake, there are thread-like material in the nucleus, a prominent nuclear envelope around the nucleus, and big lumens in the cytoplasm. The shape of the gander's mitochondria in the early spermatid is slender compared to that of the drake, and the inner membrane of the mitochondria is thicker than the outer membrane. The distal centriole of the drake and the gander in the early spermatid is a long hollow cylinder form. In the nuclear elongation stage, elongated nucleus forms two or three cross sections in one spermatid cell and it is surrounded by the amorphous sheath. The nucleus of the matured spermatid is compact and its apical end is covered with acrosome cap and acrosome spine. The axoneme is surrounded by the amorphous material.

• Journal of the Korean Home Economics Association
• /
• v.24 no.3
• /
• pp.59-67
• /
• 1986

The heat of sewing needle is generated through the friction during the needle penetration into and withdrawal from fabrics. Therefore, effects of sewing condition for knitted fabric on the heat generation of needle was examined. The needle size was not the large influence factor of heat generation of needle but the needle point shape significantly affects needle temperature. And the super needle coated with fluoro resin had more effect on reducing the heat of needle. The decrease of sewing speed and the increase of stitch rate had more effect on the reduction in needle temperature. Also the Influence of a sewing thread on the needle temperature was very large compared with bare needle. As expected, an increase in the number of fabric layers result in higher needle temperature.

• Proceedings of the KSR Conference
• /
• 2009.05a
• /
• pp.1613-1617
• /
• 2009

As demand regarding a recent energy-saving rises, the using ratio of the aluminum plate in manufacturing of a railroad vehicle has been increasing. The aluminum structure to be applied to a railroad vehicle is divided to single skin and double skin, and the main aluminum product is mainly Al 6005 extrude and Al 5083 rolled in domestic market. The Al 6005 alloy is applied heat treatment in order to improve the strength of material. Therefore there is the disadvantage that the strength of welding zone decreases compare with base material's if you apply to fusion welding like MIG(metal inert gas) welding. In this paper we tried to apply friction stir welding to solve these problems. In this study we investigated how tensile strength and fatigue strength were changed in case of changing the shoulder diameter of thread tool.