• Journal of Dental Rehabilitation and Applied Science
• /
• v.25 no.2
• /
• pp.109-123
• /
• 2009

The aim of the study was to assess the influence of insertion torque of bone quality and to compare axial force, moment and von Mises stress using finite element analysis of plastoelastic property for bone stress and strain by dividing bone quality to its thickness of cortical bone, density of trabecular bone and existence of lower cortical bone when implant inserted to mandibular premolar region. The $Br{\aa}nemark$ MKIII. RP implant and cylindrical bone finite model were designed as cortical bone at upper border and trabecular bone below the cortical bone. 7 models were made according to thickness of cortical bone, density of trabecular bone and bicortical anchorage and von Mises stress, axial force and moment were compared by running time. Dividing the insertion time, it seemed 300msec that inferior border of implant flange impinged the upper border of bone, 550msec that implant flange placed in middle of upper border and 800msec that superior border of implant flange was at the same level as bone surface. The maximum axial force peak was at about 500msec, and maximum moment peak was at about 800msec. The correlation of von Mises stress distribution was seen at both peak level. The following findings were appeared by the study which compared the axial force by its each area. The axial force was measured highest when $Br{\aa}nemark$ MKIII implant flange inserts the cortical bone. And maximal moment was measured highest after axial force suddenly decreased when the flange impinged at upper border and the concentration of von Mises stress distribution was at the same site. When implant was placed, the axial force and moment was measured high as the cortical bone got thicker and the force concentrated at the cortical bone site. The influence of density in trabecular bone to axial force was less when cortical bone was 1.5 mm thick but it might be more affected when the thickness was 0.5 mm. The total axial force with bicortical anchorage, was similar when upper border thickness was the same. But at the lower border the axial force of bicortical model was higher than that of monocortical model. Within the limitation of this FEA study, the insertion torque was most affected by the thickness of cortical bone when it was placed the $Br{\aa}nemark$ MKIII implant in premolar region of mandible.

• Structural Engineering and Mechanics
• /
• v.18 no.4
• /
• pp.389-410
• /
• 2004

In this study, theoretical and experimental results are presented which were obtained during an investigation of the influence of the $P-{\Delta}$ effect that was caused by the simultaneous changing of the axial load P of the column and the lateral displacement ${\Delta}$ in the external beam-column joints. The increase or decrease of ${\Delta}$ was simultaneous with the increase or decrease of the axial compression load P and caused an additional influence on the aseismic mechanical properties of the joint. A total of 12 reinforced concrete exterior beam-column subassemblies were examined. A new model, which predicts the beam-column joint ultimate shear strength, was used in order to predict the seismic behaviour of beam-column joints subjected to earthquake-type loading plus variable axial load and $P-{\Delta}$ effect. Test data and analytical research demonstrated that axial load changes and $P-{\Delta}$ effect during an earthquake cause significant deterioration in the earthquake-resistance of these structural elements. It was demonstrated that inclined bars in the joint region were effective for reducing the unfavourable impact of the $P-{\Delta}$ effect and axial load changes in these structural elements.

• Korean Chemical Engineering Research
• /
• v.58 no.1
• /
• pp.36-43
• /
• 2020

A biliant stent was fabricated using a magnesium alloy wire, a biodegradable metal. In order to control the fast decomposition and corrosion of magnesium alloys in vivo, magnesium alloy wires were coated with biodegradable polymers such as polycaprolactone (PCL), poly(propylene carbonate) (PPC), poly (L-lactic acid) (PLLA), and poly (D, L-lactide-co-glycolide) (PLGA). In the case of PPC, which is a surface erosion polymer, there is no crack or peeling compared to other polymers (PCL, PLLA, and PLGA) that exhibit bulk erosion behavior. Also, the effect of biodegradable polymer coating on the axial force, which is the mechanical property of magnesium alloy stents, was investigated. Stents coated with most biodegradable polymers (PCL, PLLA, PLGA) increased axial forces compared to the uncoated stent, reducing the flexibility of the stent. However, the stent coated with PPC showed the axial force similar to uncoated stent, which did not reduce the flexibility. From the above results, PPC is considered to be the most efficient biodegradable polymer.

• Structural Engineering and Mechanics
• /
• v.66 no.1
• /
• pp.125-138
• /
• 2018

This paper proposes a transfer matrix method for the bending vibration of two types of tapered beams subjected to axial force, and it is applied to analyze tapered beams with an edge or multiple edge open cracks. One beam type is assumed to be reduced linearly in the cross-section height along the beam length. The other type is a tapered beam in which the cross-section height and width with the same taper ratio is linearly reduced simultaneously. Each crack is modeled as two sub-elements connected by a rotational spring, and the method can evaluate the effect of cracking on the desired number of eigenfrequencies using a minimum number of subdivisions. Among the power series available for the solutions, the roots of the differential equation are computed using the Frobenius method. The computed results confirm the accuracy of the method and are compared with previously reported results. The effectiveness of the proposed methods is demonstrated by examining specific examples, and the effects of cracking and axial loading are carefully examined by a comparison of the single and double tapered beam results.

• Journal of Korean Society of Steel Construction
• /
• v.23 no.3
• /
• pp.327-335
• /
• 2011

This study has two objectives: (1) to evaluate the degradation characteristics of symmetric unbraced steel frames by using analytical approach, and (2) to suggest equation which can approximately estimate the effect of degradation during the schematic design stage. For the analytical approach, the refined plastic hinge method with an arc length algorithm was adopted. The subject of analysis was one story one-bay, multistory one-bay, and multistory three-bay unbraced steel frames. The main parameters of the analytical approach include the stiffness ratio of column to beam and the axial force ratio. The study led to the following conclusions. The normalized stiffness of degradations is affected by both stiffness ratio of column to beam and the axial load ratio; however, the major influence on degradations is the axial force ratio. The equation, which can approximately estimate the effect of degradation, was suggested together with the research results.

• Steel and Composite Structures
• /
• v.27 no.2
• /
• pp.229-242
• /
• 2018

High strength steel is widely used in industrial applications to improve the load-bearing capacity and reduce the overall weight and cost. To take advantage of the benefits of this type of steel in construction, an innovative hybrid fabricated member consisting of high strength steel tubes welded to mild steel plates has recently been developed. Component-scale uniaxial and multiaxial cyclic experiments have been conducted with simultaneous constant or varying axial compression loads using a multi-axial substructure testing facility. The structural interaction of high strength steel tubes with mild steel plates is investigated in terms of member capacity, strength and stiffness deterioration and the development of plastic hinges. The deterioration parameters of hybrid specimens are calibrated and compared against those of conventional steel specimens. Effect of varying axial force and loading direction on the hysteretic deterioration model, failure modes and axial shortening is also studied. Plate and tube elements in hybrid members interact such that the high strength steel is kept within its ultimate strain range to prevent sudden fracture due to its low ultimate to yield strain ratio while the ductile performance of plate governs the global failure mechanism. High strength material also significantly reduces the axial shortening in columns which prevents undesirable frame deformations.

• Structural Engineering and Mechanics
• /
• v.10 no.3
• /
• pp.197-209
• /
• 2000

The effects of weight and axial inertia of a beam are taken into account for studying the nonlinear vibration of the Timoshenko beam due to external loads. The combination of Galerkins method and Runge-Kutta method are employed to obtain the dynamic responses of the beam. A concentrated force and a two-axle vehicle traversing on the beam are taken as two examples to investigate the response characteristics of the beam. Results show that the effect of axial inertia of the beam increases the fundamental period of the beam. Further, both the dynamic deflection and the dynamic moment of the beam obtained with including the effect of axial inertia of the beam are greater than those of the beam without including that effect of the beam.

• The KSFM Journal of Fluid Machinery
• /
• v.9 no.2 s.35
• /
• pp.39-43
• /
• 2006

The magnitude of the axial force acting on turbopump bearings has a great influence on the operational reliability and service life of a turbopump. In the turbopump under current investigation the cavity vanes are introduced to the pump shroud casing to control the axial thrust of the turbopump. To investigate the effect of the cavity vanes, 3D computational flow analyses for a propellant pump stage including an inducer, impeller, volute and secondary flow passages are performed with and without the vanes. The results show that the cavity vanes are very effective in reducing the magnitude of axial thrust without notable changes on the overall performance of the turbopump.

• 유체기계공업학회:학술대회논문집
• /
• 2005.12a
• /
• pp.354-358
• /
• 2005

The magnitude of the axial force acting on turbopump bearings has a great influence on the operational reliability and service life of a turbopump. In the turbopump under current investigation the cavity vanes are introduced to the pump shroud casing to control the axial thrust of the turbopump. To investigate the effect of the cavity vanes, 3D computational flow analyses for a propellant pump stage including an inducer, impeller, volute and secondary flow passages are performed with and without the vanes. The results show that the cavity vanes are very effective in reducing the magnitude of axial thrust without notable changes on the overall performance of the turbopump.

• Journal of The Korean Society For Urban Railway
• /
• v.6 no.4
• /
• pp.383-392
• /
• 2018

This study investigated the change of additional axial stress of rail and reaction force at bridge bearings due to the track-bridge interaction when laying CWR on non-ballasted railway bridges including truss bridges with relatively long span. According to the results of the present study, additional axial stresses of rail and reaction forces at bridge bearings showed a large increase when CWR is installed on the non-ballasted railway bridge. The additional axial stress of rail can be acceptable if sufficient lateral resistance can be obtained. However, if the reaction force increases, there is a risk of damage of the bearing or pier, and therefore, it is necessary to take measures to mitigate the reaction force. It is found that additional axial stress of rail decreases when considering the frictional resistance of the bridge movable support, but its effect on the bearing reaction force is very small. On the other hand, when the longitudinal track restraint decreases, both additional axial stress of rail and bearing reaction force are reduced to a large extent. Also, when the ZLR fastening devices are applied to the region where the additional axial stress of rail is highest, bearing reaction force as well as additional axial stress of rail greatly decreased. Therefore, the application of ZLR fastening devices with the reduction of the longitudinal track restraints is very effective for installing CWR on non-ballasted railway bridges.