• 대한기계학회논문집A
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• 제21권10호
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• pp.1589-1597
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• 1997

The high-velocity impact forging process with eccentric loading condition is analyzed using the explicit time integration finite element method. In order to consider the strain hardening, strain rate hardening and thermal softening effects, which are frequently observed in high-velocity deformation phenomena, the Johnson-Cook constitutive model is applied to model the workpiece. It is assumed that the material response of the dies is elastic in the study. As a result of the eccentric loading simulation, it is found that the increase of the eccentric ratio and the allowable tilting angle cause the decrease of the maximum forging load and the blow efficiency, and it is also found that the forging load and the blow efficiency generated in the high-velocity impact forging process with three-dimensional geometry can be obtained efficiently.

• 한국소음진동공학회논문집
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• 제23권3호
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• pp.234-239
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• 2013

There are many types of speed reducer for industrial uses. However the cycloid speed reducer is widely used in manipulators based on excellent performance of low backlash, high reduction ratio and compact size. It is essential to use precision speed reducer for accuracy of position controls on robot systems and electric vehicles. The cycloid speed reducer has a eccentric rotating motion and offset to avoid some problem of assembly, so it has a disadvantage for vibration. In this paper, a multi-body dynamic model is developed for a cycloid speed reducer and the dynamic behaviors of the reducer are investigated. The cycloid speed reducer consists of cycloidal plate gears, housing gear, input shaft, output pin and shaft, and eccentric bearings. Using a CAD program, each component of cycloid reducer is modeled based on the offset and eccentric. Multi-body simulations using Recurdyn and test using a rig tester are performed. As a result, the pin reaction force and the amplitude of housing displacement are increased by the larger offset and smaller eccentric value of cycloid reducer.

• Journal of Electrical Engineering and Technology
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• 제10권3호
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• pp.1025-1034
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• 2015

This paper presented an improved analytical method for calculating the open-circuit magnetic field in the surface-mounted permanent magnet machines accounting for slots and eccentric magnet pole. Magnetic field produced by radial and parallel permanent magnet is equivalent to that produced by surface current according to equivalent surface-current method of permanent magnet. The model is divided into two types of subdomains. The field solution of each subdomain is obtained by applying the interface and boundary conditions. The magnet field produced by equivalent surface current is superposed according to superposition principle of vector potential. The investigation shows harmonic contents of radial flux density can be reduced a lot by changing eccentric distance of eccentric magnet poles compared with conventional surface-mounted permanent-magnet machines with concentric magnet poles. The FE(finite element) results confirm the validity of the analytical results with the proposed model.

• Steel and Composite Structures
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• 제23권1호
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• pp.87-94
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• 2017

Steel structures often require strengthening due to the increasing life loads, or repair caused by corrosion or fatigue cracking. Carbon Fiber Reinforced Polymers (CFRP) is one of the materials used to strengthen steel structures. Most studies on strengthening steel structures have been carried out on steel beams and steel columns under centric compression load. No independent article, to the author's knowledge, has studied the effect of CFRP strengthening on steel columns under eccentric compression load, and it seems that there is a lack of understanding on behavior of CFRP strengthening on steel columns under eccentric compression load. However, this study explored the use of adhesively bonded CFRP flexible sheets on retrofitting square hollow section (SHS) steel columns under the eccentric compression load, using numerical investigations. Finite Element Method (FEM) was employed for modeling. To determine ultimate load of SHS steel columns, eight specimens with two types of section (Type A and B), strengthened using CFRP sheets, were analyzed under different coverage lengths, the number of layers, and the location of CFRP composites. Two specimens were analyzed without strengthening (control) to determine the increasing rate of the ultimate load in strengthened steel columns. ANSYS was used to analyze the SHS steel columns. The results showed that the CFRP composite had no similar effect on the slender and stocky SHS steel columns. The results also showed that the coverage length, the number of layers, and the location of CFRP composites were effective in increasing the ultimate load of the SHS steel columns.

• Steel and Composite Structures
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• 제22권6호
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• pp.1487-1505
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• 2016

This paper presents the results of an experimental study on the behavior of a new type of composite FRP-concrete-steel member subjected to bi-axial eccentric loading. This new type of composite member is in the form of concrete-filled square steel tube slender columns with inner CFRP (carbon fiber-reinforced polymer) circular tube, composed of an inner CFRP tube and an outer steel tube with concrete filled in the two tubes. Tests on twenty-six specimens of high strength concrete-filled square steel tube columns with inner CFRP circular tube columns (HCFST-CFRP) were carried out. The parameters changed in the experiments include the slenderness ratio, eccentric ratio, concrete strength, steel ratio and CFRP ratio. The experimental results showed that the failure mode of HCFST-CFRP was similar to that of HCFST, and the specimens failed by local buckling because of the increase of lateral deflection. The steel tube and the CFRP worked together well before failure under bi-axial eccentric loading. Ductility of HCFST-CFRP was better than that of HCFST. The ultimate bearing capacity of test specimen was calculated with simplified formula, which agreed well with test results, and the simplified formula can be used to calculate the bearing capacity of HCFSTF within the parameters of this test.

• Structural Engineering and Mechanics
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• 제71권3호
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• pp.211-221
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• 2019

To study the eccentric compression behavior of ultra-high performance fiber reinforced concrete (UHPFRC) columns, six UHPFRC columns and one high-strength concrete (HSC) column were tested. Variation parameters include load eccentricity, volume of steel fibers and stirrup ratio. The crack pattern, failure mode, bearing capacity, and deformation of the specimens were studied. The results showed that the UHPFRC columns had different failure modes. The large eccentric compression failure mode was the longitudinal tensile reinforcements yielded and many horizontal cracks appeared in the tension zone. The small eccentric compression failure mode was the longitudinal compressive reinforcements yielded and vertical cracks appeared in the compressive zone. Because of the bridging effect of steel fibers, the number of cracks significantly increased, and the width of cracks decreased. The load-deflection curves of the UHPFRC columns showed gradually descending without sudden dropping, indicating that the specimens had better deformation. The finite element (FE) analysis was performed to stimulate the damage process of the specimens with monotonic loading. The concrete damaged plasticity (CDP) model was adopted to characterize the behaviour of UHPFRC. The contribution of the UHPFRC tensile strength was considered in the bearing capacity, and the theoretical calculation formulas were derived. The theoretical calculation results were consistent with the test results. This research can provide the experimental and theoretical basis for UHPFRC columns in engineering applications.

• Computers and Concrete
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• 제27권5호
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• pp.437-445
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• 2021

Retrofitting of structures has gained importance over the recent years. Particularly, Reinforced Cement Concrete (RCC) column strengthening has become a challenge to the structural engineers, owing to the risks and complexities involved in it. There are several methods of RCC column strengthening viz. RCC jacketing, steel jacketing and Fiber Reinforced Polymer (FRP) wrapping etc., FRP wrapping is the most promising alternative when compared to the others. The large research database shows FRP wrapping, through lateral confinement, improves the axial load carrying capacity of the columns under concentric loading. However, its confining efficiency reduces under eccentric loading. Hence a relative newer technique called Near Surface Mounting (NSM), in which Carbon FRP (CFRP) strips are epoxy grouted to the precut grooves in the cover concrete of the columns, has been thrust domain of research. NSM technique strengthens the column nominally under concentric load case while significantly under eccentric case. A novel configuration of NSM in which the vertical NSM (VNSM) strips are being connected by horizontal NSM (HNSM) strips was numerically investigated under both concentric and eccentric loading. It was found that the configuration with 6 HNSM strips performed better under eccentric loading than under concentric loading, while the configuration with 3 HNSM strips performed better under concentric loading than under eccentric loading. Hence an optimum of 4 HNSM strips is recommended as strengthening measure for the given column specifications. It was also found that Aluminum alloy cannot be used instead of CFRP in NSM applications owing to its lower mechanical properties.

• PNF and Movement
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• 제12권1호
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• pp.33-37
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• 2014

Purpose: In this research, the properties of the shoulder joint were measured through eccentric resistive exercise with the patients who have rotator cuff tear of shoulder joints as the targets. Methods: 23 patients who have pain due to the rupture of rotator cuff on shoulder joints were selected and divided into Exercise group (12) and Control group (11). Two groups executed exercise for 30 minutes 3 days a week. Exercise group had executed eccentric resistive exercise, and the Control group executed Complex exercise. Results: In external rotation $180^{\circ}/s$, $240^{\circ}/s$, the Exercise group showed to be an average of 8% higher than the Control group. For Internal rotation $90^{\circ}/s$, $180^{\circ}/s$, $240^{\circ}/s$ the Exercise group showed to be an average of 30% higher that the Control group. Conclusion: To lessen the rupture of rotator cuff on shoulder joints, muscles strengthening is very important across various methods of eccentric exercise programs which are external/internal rotators of the shoulder joint needed for throwing. This is effective in preventing injury and improving rotation.

• 운동영양학회지
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• 제23권1호
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• pp.48-54
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• 2019

[Purpose] The combined effect of different types of post-exercise treatment has not been fully explored. We investigated the effect of combined cold water immersion (CWI) and compression garment (CG) use after maximal eccentric exercise on maximal muscle strength, indirect muscle damage markers in the blood, muscle thickness, and muscle soreness score 24 h after exercise. [Methods] Ten men performed two trials (CWI + CG and CON) in random order. In the CWI + CG trial, the subjects performed 15 min of CWI (15℃), followed by wearing of a lower-body CG for 24 h after exercise. In the CON trial, there was no post-exercise treatment. The exercise consisted of 6 × 10 maximal isokinetic (60°·s^-1) eccentric knee extensions using one lower limb. The maximal voluntary contraction (MVC) and maximal isokinetic (60°·s^-1) strength during knee extension, as well as the indirect muscle damage markers, were evaluated before exercise and 24 h after exercise. [Results] The maximal muscle strength decreased in both trials (p < 0.001), with no difference between them. The exercise-induced elevation in the myoglobin concentration tended to be lower in the CWI + CG trial than in the CON trial (p = 0.060). The difference in the MVC, maximal isokinetic strength, muscle thickness, and muscle soreness score between the trials was not significant. [Conclusion] CWI followed by wearing of a CG after maximal eccentric exercise tended to attenuate the exercise-induced elevation of indirect muscle damage markers in the blood.

• PNF and Movement
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• 제21권3호
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• pp.291-298
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• 2023

Purpose: This study aimed to suggest an effective exercise for treating anterior cruciate ligament (ACL) and hamstring injuries based on the dynamic control ratio (DCR) for the hamstring and quadriceps during eccentric hamstring exercises. Methods: Twenty-four healthy participants participated in this study. The participants performed three eccentric hamstring exercises, including the Nordic exercise, the supine leg curl, and single-leg deadlifts. During the eccentric hamstring exercises, the vastus medialis oblique (VMO), vastus lateralis (VL), biceps femoris (BF), and semitendinosus (ST) were measured using surface electromyography. Results: The DCR was significantly lower during the supine leg curl and single-leg deadlift than during the Nordic exercise (p < 0.05). The activity of the VMO and VL was significantly greater during the supine leg curl than during the Nordic exercise and the single-leg deadlift (p < 0.05). VL activity was significantly higher during the single-leg deadlift than during the Nordic exercise (p < 0.05). ST activity was significantly higher during the supine leg curl and Nordic exercise than during the single-leg deadlift (p < 0.05). BF activity was significantly higher during the supine leg curl than during the Nordic exercise and single-leg deadlift (p < 0.05). Finally, the BF showed significantly higher activity during the Nordic exercise compared to during the single-leg deadlift (p < 0.05). Conclusion: Based on the DCR ratio and quadriceps activity, the supine leg curl should be introduced early in rehabilitation for ACL injuries.