• The Journal of Korean Academy of Prosthodontics
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• v.43 no.4
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• pp.544-561
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• 2005

Purpose : This study was to assess the loading distributing characteristics of implant systems with internal connection or external connection under vertical and inclined loading using finite element analysis. Materials and methods : Two finite element models were designed according to type of internal connection or external connection The crown for mandibular first molar was made using cemented 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 centric cusp tip in a 15$^{\circ}$ inward inclined direction (loading condition B), or 200N at the centric cusp tip in a 30$^{\circ}$ outward inclined direction (loading condition C) respectively. Von Mises stresses were recorded and compared in the supporting bone, fixture, abutment and abutment screw. Results : 1. In comparison with the whole stress or the model 1 and model 2, the stress pattern was shown through th contact of the abutment and the implant fixture in the model 1, while the stress pattern was shown through the abutment screw mainly in the model 2. 2. Without regard to the loading condition, greater stress was taken at the cortical bone, and lower stress was taken at the cancellous bone. The stress taken at the cortical bone was greater at the model 1 than at the model 2, but the stress taken at the cortical bone was much less than the stress taken at the abutment, the implant fixture, and the abutment screw in case of both model 1 and model 2. 3. Without regard to the loading condition, the stress pattern of the abutment was greater at the model 1 than at the model 2. 4. In comparison with the stress distribution of model 1 and model 2, the maximum stress was taken at the abutment in the model 1. while the maximum stress was taken at the abutment screw in the model 2. 5. The magnitude of the maximum stress taken at the supporting bone, the implant fixture, the abutment, and the abutment screw was greater in the order of loading condition A, B and C. Conclusion : The stress distribution pattern of the internal connection system was mostly distributed widely to the lower part along the inner surface of the implant fixture contacting the abutment core through its contact portion because of the intimate contact of the abutment and the implant fixture and so the less stress was taken at the abutment screw, while the abutment screw can be the weakest portion clinically because the greater stress was taken at the abutment screw in case of the external connection system, and therefore the further clinical study about this problem is needed.

• Journal of the Korean Society for Precision Engineering
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• v.27 no.3
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• pp.80-88
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• 2010

A simple computational model for modeling of subsurface crack growth under cyclic contact loading is presented. In this model, it is assumed that the initial fatigue crack will initiate in the region of the maximum equivalent stress at certain depth under the contacting surface. The position and magnitude of the maximum equivalent stress are determined by using the equivalent contact model, which is based on the Hertzian contact conditions with frictional forces. The virtual crack extension method is used for simulation of the fatigue crack growth from the initial crack up to the formation of the surface pit due to contact fatigue. The relationships between the stress intensity factor and crack length are then determined for various combinations of equivalent contact radii and loadings.

• Journal of the Korea institute for structural maintenance and inspection
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• v.15 no.2
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• pp.98-106
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• 2011

The deck of steel box girder bridges is composed of deck plate, longitudinal rib, and transverse ribs. The orthotropic steel decks have high possibility to fatigue damage due to numbers of welded connection part, the heavy contact loadings, and the increase of repeated loadings. Generally, the local stress by the repeated loadings of heavy vehicles causes the orthotropic steel deck bridge to fatigue cracks. The increase of traffic volume and heavy vehicle loadings are promoted the possibility of fatigue cracks. Thus, it is important to exactly evaluate the structural behavior of bridge considering the contact loading area of heavy vehicles and real load patterns of heavy trucks which have effects on the bridge. This study estimated the effect of contact area of design loads and real traffic vehicles through the finite element analysis considering the real loading conditions. The finite element analysis carried out 4 cases of loading patterns in the orthotropic steel deck bridge. Also, analysis estimated the influence of contact area of real truck loadings by the existence of diaphragm plate. The result of finite element analysis indicated that single tire loadings of real trucks occurred higher local stress than one of design loadings, and especially the deck plate got the most influence by the single tire loading. It was found that the diaphragm attachment at joint part of longitudinal ribs and transverse ribs had no effects on the improvement of structural performance against fatigue resistance in elastic analysis.

• Korean Journal of Applied Biomechanics
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• v.14 no.2
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• pp.105-119
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• 2004

To enhance our understanding of the loads on the foot during treadmill running, we have used a pressure-sensitive insole system to determine pressure, rate of loading and impulse distributions on the plantar surface during treadmill running, both in minimally cushioned footwear and in cushioned shoes. This report includes pressure, rate of loading, impulse and contact time data from a study of ten subjects running on a treadmill at 4.0m/s. Among heel-toe runners, the highest peak pressures and highest rates of loading were observed under the centre of the heel and in the medial forefoot. The arch regions were only lightly loaded. Contact time was greater in the forefoot than in the heel. Two-thirds of the impulse recorded during the step was the result of forces applied through the forefoot, mostly in the region of the metatarsal heads. The distribution of loads in the shoe suggests that the load distributing properties of the cushioning system are most important in the centre of the heel, under the metatarsal heads and great toe. Shock attenuation is primarily required under the centre of the heel and to lesser extent under the metatarsal heads. Some energy dissipation may be desirable in the heel region because it causes shock to be absorbed with less force. All the 'propulsive' effort is applied through the forefoot. Therefore, this region should as resilient as possible.

• Tribology and Lubricants
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• v.20 no.6
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• pp.322-329
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• 2004

Recently, a load/unload(L/UL) system is adopted to the hard disk drive(HDD) due to its advantages such as lower power consumption, larger data zone, simpler fabrication of disk due to no bumped parking zone, and rarer contact between slider and media. An analysis of the transient motion for the slider is very important to design an air bearing surface(ABS) of the slider to secure the stable performance of the system. During the L/UL process, however, there are several issues occurred such as contact or collision between slider and media. Sometimes this will cause the system failure. In this study, the dynamics of a pico slider during the loading process are investigated through numerical simulation using FEM analysis and experiment. Ramp profile and angular velocity of the swing arm actuator are very important parameters for the design of L/UL system to avoid collision between slider and disk.

• Advances in Computational Design
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• v.8 no.2
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• pp.97-112
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• 2023

The Finite Element (FE) modeling of Reinforced Concrete (RC) under seismic loading has a sensitive impact in terms of getting good contribution compared to experimental results. Several idealized model types for simulating the nonlinear response have been developed based on the plasticity distribution alone the model. The Continuum Models are the most used category of modeling, to understand the seismic behavior of structural elements in terms of their components, cracking patterns, hysteretic response, and failure mechanisms. However, the material modeling, contact and nonlinear analysis strategy are highly complex due to the joint operation of concrete and steel. This paper presents a numerical simulation of a chosen RC column under monotonic and cyclic loading using the FE Abaqus, to assessthe hysteretic response and failure mechanisms in the RC columns, where the perfect bonding option is used for the contact between concrete and steel. While results of the numerical study under cyclic loading compared to experimental tests might be unsuccessful due to the lack of bond-slip modeling. The monotonic loading shows a good estimation of the envelope response and deformation components. In addition, this work further demonstrates the advantage and efficiency of the damage distributions since the obtained damage distributions fit the expected results.

• Composites Research
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• v.15 no.2
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• pp.1-10
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• 2002

The strength of glass/epoxy fabric joints under pin-loading is estimated based on the characteristics length method and experiment. To investigate the effect of finite element idealization for the contact between pin and laminate, three modeling cases are analyzed; assuming the cosine load distribution around the contact area, constraining the radial displacement at the hole boundary, and using the contact element. To study the effect of failure criteria, Tsai-Wu and Yamada-Sun methods are applied on the characteristic curve. The results of the nonlinear analysis using the contact element showed good agrements with experimental data in both laminates made of uni-directional prepreg tapes and fabrics. In terms of failure criteria, Tsai-Wu method showed better agreement with experimental results than the one by Yamada-Sun laminate.

• Journal of Mechanical Science and Technology
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• v.19 no.8
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• pp.1554-1567
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• 2005

When multiple robotics systems with several sub-chains grasp a common object, the inherent force redundancy provides a chance of utilizing internal loading. Analysis of grasping space based internal loading is proposed in this work since this method facilitates understanding the physical meaning of internal loadings in some applications, as compared to usual operational space based approach. Investigation of the internal loading for a triple manipulator has been few as ,compared to a dual manipulator. In this paper, types of the internal loading for dual and triple manipulator systems are investigated by using the reduced row echelon method to analyze the null space of those systems. No internal loading condition is derived and several load distribution schemes are compared through simulation. Furthermore, it is shown that the proposed scheme based on grasping space is applicable to analysis of special cases such as three-fingered and three-legged robots having a point contact with the grasped object or ground.

• Journal of the Computational Structural Engineering Institute of Korea
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• v.23 no.4
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• pp.403-407
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• 2010

Gecko adhesion system consists of beam-shaped seta and spatula which has the role of adhesive pad. In this paper, adhesion mechanism of gecko adhesion system is performed by using adhesive beam contact model. this model has a feature of non-uniform stress profile on the contact surface and adhesion/detachment mechanism is determined by the tensile stress of the contact region. a spatula tip pad has the role of reduction of maximum tensile stress and adhesive force is increased due to this effect. As for a reverse loading case, maximum compressive stress drops by the spatula effect and this cause unsymmetric loading conditions between adhesion and detachment forces. In this study, finite element method is used for the analysis of adhesive beam contact model and the results for spatula effect are presented.

• Journal of Dental Rehabilitation and Applied Science
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• v.19 no.4
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• pp.257-268
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• 2003

The purpose of this study was to assess the loading distributing characteristics of implant prosthesis according to position and direction of load, under vertical and inclined loading using FEA analysis. The finite element model was designed according to standard fixture (4.1mm restorative component x 11.5mm length). The crown for mandibular first molar was made using UCLA 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 usp 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 screw. The following results have been made based on this study: 1. Stresses were concentrated mainly at the ridge crest around implant in both vertical and oblique loading but stresses in the cancellous bone were low in 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. 4. The relative positions of the resultant line of force from occlusal contact and the center of rotation seems to be more important. 5. The magnitude of the stress in the supporting bone, fixture and abutment screw was greater with the outward oblique loading than with the inward oblique loading and was the greatest under loading at the centric cusp in a $30^{\circ}$ outward oblique direction. Conclusively, this study provides evidence that bending moments resulting from non-axial loading of dental implants caused stress concentrations on cortical bone. But it seems to be more important that how long is the distance from center of rotation of the implant itself to the resultant line of force from occlusal contact(leverage). The goal of improving implants should be to avoid bending of the implant.