• Journal of Dental Rehabilitation and Applied Science
• /
• v.21 no.1
• /
• pp.1-14
• /
• 2005

The purpose of this study was to assess the loading distributing characteristics of implant prosthesis of internal connection system(ITI system) according to position and direction of load, under vertical and inclined loading using finite element analysis (FEA). The finite element model of a synOcta implant and a solid abutment with $8^{\circ}$ internal conical joint used by the ITI implant was constructed. The gold crown for mandibular first molar was made on solid abutment. Each three-dimensional finite element model was created with the physical properties of the implant and surrounding bone. This study simulated loads of 200N at the central fossa in a vertical direction (loading condition A), 200N at the outside point of the central fossa with resin filling into screw hole in a vertical direction (loading condition B), 200N at the centric cusp in a $15^{\circ}$ inward oblique direction (loading condition C), 200N at the in a $30^{\circ}$ inward oblique direction (loading condition D) or 200N at the centric cusp in a $30^{\circ}$ outward oblique direction (loading condition E) individually. Von Mises stresses were recorded and compared in the supporting bone, fixture, and abutment. The following results have been made based on this study: 1. Stresses were concentrated mainly at the ridge crest around implant under both vertical and oblique loading but stresses in the cancellous bone were low under both vertical and oblique loading. 2. Bending moments resulting from non-axial loading of dental implants caused stress concentrations on cortical bone. The magnitude of the stress was greater with the oblique loading than with the vertical loading. 3. An offset of the vertical occlusal force in the buccolingual direction relative to the implant axis gave rise to increased bending of the implant. So, the relative positions of the resultant line of force from occlusal contact and the center of rotation seems to be more important. 4. In this internal conical joint, vertical and oblique loads were resisted mainly by the implant-abutment joint at the screw level and by the implant collar. Conclusively, It seems to be more important that how long the distance is from center of rotation of the implant itself to the resultant line of force from occlusal contact (leverage). In a morse taper implant, vertical and oblique loads are resisted mainly by the implant-abutment joint at the screw level and by the implant collar. This type of implant-abutment connection can also distribute forces deeper within the implant and shield the retention screw from excessive loading. Lateral forces are transmitted directly to the walls of the implant and the implant abutment mating bevels, providing greater resistance to interface opening.

• Journal of the Korean Society of Industry Convergence
• /
• v.26 no.2_2
• /
• pp.285-291
• /
• 2023

In this paper, in order to secure the safety and productivity of pine cone harvest, modeling and structural analysis of the hammering system for pine cone harvest drone that can easily access pine cone of Pinus koraiensis and collide with them to harvest them was performed. It calculate the equivalent stress for the structure of the hammering system and the yield strength of the applied material by applying the shear force of the stalk at which the pine cone is separated from the branch, and it is to verify the safety of the structure and propose an optimal design through appropriate factor of safety and design change. The shear force of the stalk at which the pine cone was separated from the branch was 468 N, and was applied to both ends of the hammering system. The yield strength of SS400 steel used in the hammering system is 245 ㎫, and the design change and structural analysis were performed so that the Von Mises stress could be less than 122.5 ㎫ by applying the factor of safety of 2.0 or more. As a result of the structural analysis of the frist modeling, the Von Mises stress was 220.3 ㎫, the factor of safety was 1.12, and the stress was concentrated in the screw fastening holes. As a result of the design change of the screw fastening holes, the Von Mises stress was 169.4 ㎫, the factor of safety was 1.45, and the stress was concentrated on the side part. As a result of the design change by changing screw fastening holes and adding ribs, the Von Mises stress was 121.6 ㎫, and the factor of safety was 2.02. The safety of the hammering system was secured with an optimal design with little change in mass. There was no deformation or damage as a result of experimenting on pine cone harvest by manufacturing the hammering system with an optimal design.

• Proceedings of the KSR Conference
• /
• 2011.10a
• /
• pp.261-267
• /
• 2011

The test fit has commonly used for the evaluation of the railbed condition, and indirect methods by using the compressional wave are also studied. the direct evaluation method by penetration test has not been studied. For the measurement of in-situ cone tip resistance of the railbed with minimizing the disturbance of the upper railbed. the cone penetrometer with the helical type outer rod(CPH) was developed. The outer rod, which has helical screw, is penetrated through the gravel layer and provides the reaction force for cone penetration testing. the cone tip resistances are measured by the mini cone penetrometer, where diameter is 15mm. For the developing the mini cone, strain gauge installation, circuit configuration, penetration rates and calibration process are considered. For the easy penetration of the screw rod in the field, the reaction force stepping plate and guide column are arranged. The screw rod are penetrated through the gravel layer. And the mini cone was pushed into the subgrade railbed at the penetration rate of 1mm/sec. The penetration test shows that the cone tip resistance increases along the depth. In addition, the subgrade condition is evaluated. This study demonstrates that the CPH may be effectively used for the evaluation of subgrade method any damage of the gravel layer.

• Journal of Technologic Dentistry
• /
• v.35 no.4
• /
• pp.303-312
• /
• 2013

Purpose: In this research, non-linear three dimensional finite element models with contact elements were constructed. For the investigations of the distributions of contact stresses, 3 units fixed partial dentures model were studied, especially on the interface of the gold screw and cylinder, abutment screw. Methods: 3 types of models were constructed ; the basic fixed partial denture in molar region with 3 units and 3 implants, the intermediate pontic fixed partial denture model with 3 units and 2 implants, and the extension pontic fixed partial denture model with 3 units and 2 implants. For all types, the external loading due to chewing was simulated by applying $45^{\circ}$ linguo-buccal loading of 300 N to the medial crown. For the simulation of the clamping force which clinically occurs due to the torque, thermal expansion was provided to the cylinder as a preload. Results: Under 300 N concentrated loading to the medial crown, the maximum contact stress between abutment screw and gold screw was 86.85~175.86MPa without preload, while the maximum contact stress on the same area was 25.59~57.84MPa with preload. Conclusion: The preloading affected the outcomes of the finite element stress analysis. Reflecting the clinical conditions, the preloading conditions should be considered for other practical study utilizing FEA. For the study of the contact stresses and related motions, various conditions, such as frictional coefficient changes, gap between contact surfaces, were also varied and analyzed.

• Proceedings of the Korea Crystallographic Association Conference
• /
• 2002.11a
• /
• pp.3-3
• /
• 2002

Many studies on crystal growth mechanisms of the hen egg-white lysozyme protein crystals have mainly performed by optical microscopy and atomic force microscopy (AFM). As results, two types of growth mechanisms, which are a two-dimensional nucleation mechanism and a spiral growth mechanism, were identified. However, there was no direct evidence of grown-in screw dislocations at the spiral sites. We first observed the screw dislocations in tetragonal lysozyme crystals using synchrotron X-ray topography. In addition, to confirm the characteristics of dislocations, we have observed some elastic constants in lysozyme crystals in terms of the sound velocity measurement by pulse echo methods. Tetragonal hen egg-white lysozyme crystals were grown by the concentration gradient method. The crystals were grown in test tubes, with an inner diameter of 8 ㎜ and 80 ㎜ in length, held vertically. The test tubes were kept at 23C for 2 weeks. The maximum size of crystals were 3×3×4 ㎟. The high quality crystals were examined by Laue topography with a water filter using synchrotron radiation. Figure is a X-ray topograph. Several straight screw dislocations were observed. We also determined Burgers vector to be a [110] direction. The measurement of sound velocity was performed by the digital signal processing method. the crystals were placed in stainless steel vessel, which was filled with lysozyme solution used for crystal growth. We observed the longitudinal sound velocity along the [110] direction in the tetragonal is obtained to be 1817 ㎧. Therefore, Young modulus and shear modulus were evaluated to be 2.70 Gpa and 1.02 Gpa, respectively, if we assumed Poisson ratio is 0.33. These results will be discussed at the meeting.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.24 no.1
• /
• pp.16-23
• /
• 2016

The EWB(electronic wedge brake) is one in which the braking force is developed in a wedge and caliper system and applied to a disk and wedge mechanism. The advantage of the wedge structure is that it produces self-reinforcing effect and hence, utilizes minimal motor power, resulting in reduced gear and current. The extent of use of clamping force sensors and protection from failure of the EWB system directly depends on the level of vehicle mass production. This study investigated the mathematical equations, simulation modeling, and failsafe control algorithm for the clamping force sensor of the EWB and validated the simulations. As this EWB system modeling can be applied to motor inductance, resistance, screw inertia, stiffness, and wedge mass and angle, this study could improve the accuracy of simulation of the EWB. The simulation results demonstrated the braking force, motor speed, and current of the EWB system when the driver desired to the step and pulse the brake force inputs. Moreover, this paper demonstrated that the proposed failsafe control algorithm accurately detects faults in the clamping force sensor, if any.

• Transactions of Materials Processing
• /
• v.14 no.9 s.81
• /
• pp.756-763
• /
• 2005

The applicability and productivity of hydroforming process can be increased by combining pre- and post-forming processes such as the bending, piercing and embedding process. For the fabrication of automotive parts, the hollow bodies with connecting nuts are widely used to connect parts together. Hollow body with connecting nuts has been conventionally fabricated by welding nuts or screwing in autobody screws. It requires multiple steps and devices fur the welding and/or screwing Therefore in this study, hydro-embedding process that combines the hydraulic embedding of connecting element(nut) with hydroforming process is investigated. Studies on the hydro-embedding technology have been performed to optimize the shape of the connecting element by analyzing the deformed mode of the embedded tube The effects of the shape of the screw tip, screw thread and shape of thread on the connection force between the tube and the connecting element have been investigated to optimize the shape of connecting element. Finite element analysis has also been performed to provide deformation behaviors of the tube surrounding a hole produced by hydro-embedding.

• Proceedings of the Korean Society for Technology of Plasticity Conference
• /
• 2009.05a
• /
• pp.180-184
• /
• 2009

A novel set of experimental test tooling for measuring pulling and holding forces for drawbeads on binders inclined at a wide range of angles is introduced. A mechanical design featuring a single load cell, a male-female draw bead set, translation and rotation degrees of freedom, and a screw-driven clamping system has been incorporated into a standard tensile test machine. On a real time basis, restraining and holding force data with respect to draw-in displacement may be directly downloaded into a PC for data processing. The proposed experimental system represents a significant breakthrough in drawbead simulation technology due to its relatively low cost, clever design, and versatility. The system is shown to yield excellent experimental data suitable for verifying theory and numerical model predictions.

• Journal of Korean Neurosurgical Society
• /
• v.30 no.2
• /
• pp.131-136
• /
• 2001

Object : The clinical uses of screws are increasing with broader applications in spinal disorders. When screws are inserted repeatedly to achieve optimal position, tips of screw pitch may become damaged during insertion even though there are significant differences in the moduli of elasticity between bone and titanium. The effect of repeated screw insertion on pullout resistance was investigated. Methods : Three different titanium screws(cortical lateral mass screw, cancellous lateral mass screw and cervical vertebral body screw) were inserted into the synthetic cancellous material and then extracted axially at a rate of 2.4mm/min using Instron(Model TT-D, Canton, MA). Each set of screws was inserted and pulled out three times. There were six screws in each group. The insertional torque was measured with a torque wrench during insertion. Pullout strength was recorded with a digital oscilloscope. Results : The mean pullout force measurements for the cortical lateral mass screws($185.66N{\pm}42.60$, $167.10N{\pm}27.01$ and $162.52 N{\pm}23.83$ for first, second and third pullout respectively : p=0.03) and the cervical vertebral body screws($386.0N{\pm}24.1$, $360.2N{\pm}17.5$ and $330.9N{\pm}16.7$ : p=0.0024) showed consecutive decrease in pullout resistance after each pullout, whereas the cancellous lateral mass screws did not($194.00N{\pm}36.47$, $219.24N{\pm}26.58$ and 199.49N(36.63 : p=0.24). The SEM after insertion and pullout three times showed a blunting in the tip of the screw pitch and a smearing of the screw surface. Conclusions : Repetitive screw insertion and pullout resulted in the decrease of pullout resistance in certain screws possibly caused by blunting the screw tip. This means screw tips suffer deformations during either repeated insertion or pullout. Thus, the screws that have been inserted should not be used for the final construct.

• The Journal of Korean Academy of Prosthodontics
• /
• v.43 no.5
• /
• pp.671-683
• /
• 2005

Statement of problem: The most commonly reported problem associated with dental implant restoration is the loosening of the screws. Purpose: This study compared the efficacy of an implant system incorporating an anti-rotational locking sleeve(Anti-Rotating Inner Post Screw System(ARIPS-system)) with other, traditional implant systems as a means of minimizing vibration loosening. Materials and methods: Three implant systems were examined; the conventional external hex type, the ARIPS-system, and the internal taper type implant system 30 specimens(10 samples per group)were fabricated and each abutment screw was secured to the implant future with 32Ncm of torque force and loosening torque was measured using a Torque Gauge. The procedure was repeated 3 times, recording initial loosening torque each time. The re-tightened abutment screw was subjected to a cyclic load having a maximum forte of 200N and minimum of 20N at 2Hz over a period of 12,600 cycles. after which the loosening torque was measured. Measured values were calaulated for statistical analysis. Analysis of measured value was performed by 3 methods: (i) as a percentage average of the initial 3 loosening-torque values(initial loosening value) to the tightening torque of 32Ncm, (ii) as a percentage of the loosening torque value after a load of 200N(experimental value) to the initial loosening value, and (iii) as a percentage of the experimental value to the 32Ncm of tightening torque. The analyses shows the amount of initial loosening at the screw, loosening by repetitive load and the the final loosening value. Results: The results of this study were as follows (1) Percentage of initial loosening value to tightening-torque was increased in order of external hex, ARIPS-system and internal taper and all values between each groups showed statistical significance (p<0.05). (2) Percentage of experimental value to initial loosening value was increased in order of external hex, ARIPS-system and internal taper. Value of internal taper showed significant difference with those of external hex and ARIPS-system (p<0.05). (3) Percentage of experimental value to tightening torque was increased in order of external hex, ARIPS-system and internal taper and all values between each groups showed statistical significance (p<0.05). Conclusion: The results of the analysis of the final loosening level value, which are closely correlated to clinical use, show that the ARIPS-system can be a useful means of minimizing abutment screw loosening when compared to the external hex type system. Although further clinical studies need to be made, the ARIPS-system should be considered to maximize the long-term success of the implant prosthesis.