• Proceedings of the Korean Society for Technology of Plasticity Conference
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• 1995.10a
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• pp.172-180
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• 1995

Isothermal interrupted deformation behavior of 10vol.%SICp/AI-Si composites was investigated by hot torsion test at the temperature ranges from 27$0^{\circ}C$ to 43$0^{\circ}C$ and at strain rate range of 1.26X10-2~2.16X10-1/sec. With increasing pass strain, flow stresses were high compared to continuous deformation condition. Fractional softening was increased with temperature imterruption time and pass strain. Fractional softening of 10vol.%SiCp/AI-Si composites was lower than that of AI-Si matrix at 37$0^{\circ}C$. However at high temperature of 43$0^{\circ}C$, SiC particle promoted static softening, diminishing the dislocation density at the interface of AI-Si matrix and reinforcements, then this resulted in higher fractional softening in composites. Both of failure strain improved reducing the fracture of SiC particle and Si precipitates above 32$0^{\circ}C$, however at low temperature of 27$0^{\circ}C$, the softening effect by interrupted deformation was found to be negligible.

• Journal of Advanced Navigation Technology
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• v.16 no.2
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• pp.367-374
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• 2012

A dynamic simulation and test of frame with thin walled closed section beams considering warping conditions have been performed. When a beam is subjected under torsional moment, the cross section will deform an warping as well as twist. For some thin-walled sections warping will be large, and accompanying warping restraint will induce axial and shear stresses and reduce the twist of beam which stiffens the beam in torsion. This paper presents that an warping restraint factor in finite element model effects the behavior of beam deformation and dynamic mode shape. The computer modelling of frame is discussed in linear beam element model and linear thin shell element model, also presents a correlation between computer predicted and actual experimental results for static deflection, natural frequencies and mode shapes of frame.

• Transactions of the Korean Society of Automotive Engineers
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• v.20 no.5
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• pp.65-70
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• 2012

Torque fluctuation of engine generate gear rattle noise of transmission and many researches have been studied to decrease rattle noise by adjusting clutch damper system. So design optimization of clutch system is very important to decrease rattle noise and need knowing clutch dynamic torque at real vehicle driving condition. This makes it possible to measure clutch dynamic torque by using a small-size magnetic sensor. We install a small-size magnetic sensor on the input shaft of the transmission and measure the relative angular displacement between clutch hub and disc plate. We can obtain the clutch torque correspond to the angular displacement in the clutch torsional characteristics test. The object of this research is to measure clutch dynamic torque on real vehicle condition. Therefore, Clutch dynamic torque is very useful for investigating operating range of clutch according to engine torque and predicting the damping performance of torsional vibration on the powertrain.

• Journal of The Korean Society of Integrative Medicine
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• v.8 no.2
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• pp.75-88
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• 2020

Purpose : Dysmenorrhea can be caused by misalignment of the pelvis. Since pilates stabilization exercise is a methods that affects pelvic alignment by inducing contraction of abdominal muscles, the purpose of this study is to determine whether dysmenorrhea is reduced when pilates stabilization exercise is applied. Methods : 47 dysmenorrhea patients were randomly divided into experimental (n=23) and control (n=24) groups. The experimental group performed pilates stabilization exercise three times a week for 12 weeks, and the control group did not perform any intervention. Abdominal muscle thickness, lumbar pelvic alignment, and dysmenorrhea were measured before intervention, 6 weeks, and 12 weeks after intervention to determine the mean change over time and the effect of group and factor interactions (repeated measured ANOVA and contrast test for each period). Results : In the experimental group, the thickness of the transverse abdominis, internal oblique, and external oblique muscles were increased significantly by group and period (p<.05). The pelvic torsion, lordosis and dysmenorrhea were also significantly decreased by group and period. But the control group did not change significantly in any of the variables. Conclusion : Applying pilates stabilization exercise to women with dysmenorrhea may be an effective intervention that contributes to relieving dysmenorrhea by correcting the stability and alignment of the lumbar pelvis.

• Transactions of Materials Processing
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• v.3 no.4
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• pp.427-439
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• 1994

The high temperature deformation behavior of $SiC_p/Al-Si$ composites and Al-Si matrix was studied by hot torsion test in a range of temperature from $270^{\circ}C$ to $520^{\circ}C$ and at strain rate range of $1.2{\times}10_{-3}~2.16{\times}10_{-1}/sec$. The hot restoration mechanisms for both matrix and composites were found to be dynamic recrystallization(DRX) from the investigation of flow curves and microstructural evolutions. The Si precipitates and SiC particles promoted DRX, and the peak strain$({\varepsilon}_p)$ of the composites was smaller than that of the matrix. Flow stresses of $SiC_p/Al-Si$ composites were found to be generally higher than the matrix, but the difference was quite small at higher temperature due to the decrease of capability of load transfer by SiC particles. With increasing temperature, failure strain of matrix and composites are inclined to increase, the increasing value of failure strain for the $SiC_p/Al-Si$ composites was small compared to that of matrix. The stress dependence of both materials on strain rate() and temperature(T) was examined by hyperbolic sine law, $\.{\varepsilon}=A_1[sinh({\alpha}{\cdot}{\sigma})]_n$exp(-Q/RT)

• Transactions of the Korean Society of Mechanical Engineers A
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• v.30 no.9 s.252
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• pp.1041-1048
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• 2006

The pulley is one of core mechanical elements in the power steering system for vehicles. The pulley operates under both the compressive loading and the torque. Therefore, to assure the safety of the power steering system, it is very important to investigate the durability and the optimization of the pulley. In this study, the applied stress distribution of the pulley under high tension and torsion loads was obtained by using finite element analysis. Based on these results the fatigue life of the pulley with the variation of the fatigue strength was evaluated by a durability analysis simulator. The results at 50% and 1% for the failure probability were compared with respect to the fatigue life. In addition to the optimum design for the fatigue life is obtained by the response surface method. The response function utilizes the function of the life and weight factors. Within range for design life condition the minimization of the weight, one of the formulation, is obtained by the optimal design. Moreover the optimum design by considering its durability and validity is verified by the durability test.

• Korean Journal of Applied Biomechanics
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• v.28 no.4
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• pp.219-225
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• 2018

Objective: Epidemiological research shows that 47 to 73% of athletes suffer from recurrent ankle sprains. Joint mobilization techniques (JMT) implemented in correcting may be beneficial in the management of ankle injuries. The purpose of this study is to examine the immediate JM on ankle complex as clinical measures in individuals with chronic ankle instability (CAI) through intervention. Method: Thirteen subjects with CAI (8 males and 5 females) participated in this study. Each subject tried total four alignments (Navicular drop test: NDT, Standing rearfoot angle: SRA, Tibia torsion: TT, and dorsiflexion range of motion: DFROM). The participants were performed the 10 meter shuttle run after JMT for post-task. Finally, it was tried to compare between pre-post tasks after shuttle run. Results: SRA and DFROM after intervention showed significant differences. SRA (p=.026), and DFROM (p=.034). Conclusion: We concluded that the JMT has resulted in improvement in SRA, DFROM. Increased DFROM and varus shapes of foot would be closed kinetic chain, indicating that reduce the risk factors of ankle sprain. Future study needs to be conducted in order to measure the effects of prolonged intervention of JMT.

• Journal of The Korean Society of Integrative Medicine
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• v.7 no.3
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• pp.181-188
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• 2019

Purpose: This study was performed to determine the effects of a gluteus maximus strengthening exercise on both spinal alignment and dynamic balance in subjects with kyphosis. Methods: We measured the kyphosis angle of 150 subjects and selected those whose kyphosis angle was > $50^{\circ}$. The participants included 10 male and 12 female college students. After a gluteus maximus strengthening exercise was applied, the subjects were measured by the formetric 4D and Biorescue systems. The collected data were analyzed by a paired t-test with the SPSS (Ver. 21) program for spinal alignment and dynamic balance comparisons both before and after the gluteus maximus strengthening exercise was completed. Results: The results regarding spinal alignment showed statistically significant decreases in pelvic tilt, kyphotic angle, and lordotic angle after the intervention (p < .05). However, trunk imbalance, pelvic torsion, surface rotation, and lateral deviation were not significantly different after the exercise. The results of the dynamic balance showed statistically significant increases in limits of stability after the exercise (p < .05). Conclusion: The above results suggest that the implemented gluteus maximus strengthening exercise may be effective for spinal alignment and dynamic balance in subjects with kyphosis.

• Journal of International Academy of Physical Therapy Research
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• v.10 no.2
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• pp.1810-1817
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• 2019

Background: Effect of cervical and lumbar tractions on the reduction in the angle of curvature and the effect of a correction exercise or a general traction method on balance, muscle strength, pain, and body alignment, however insufficient research has been undertaken on self traction exercises targeting patients with scoliosis. Purpose: To determine the effect of cervical and lumbar tractions on the reduction in the angle of curvature and the effect of a correction exercise or a general traction method on balance, muscle strength, pain, and body alignment. Design: Randomized controlled clinical trial (single blinded) Methods: Twelve adults(20s) with scoliosis were included in this study and performed a traction program that was composed of a 5-min warm-up exercise, a 15-min main exercise, and a 5-min cool-down exercise (25 minutes in total), three times a week for four weeks. The Chiro traction machine was used for the self-traction exercise. Vertebral alignment, muscle strength, and flexibility were compared before and after the intervention using the paired T-test. Results: The scoliosis angle, pelvic torsion, and lumbar extensor were significantly changed by intervention; however, there was no significant difference in flexibility. Conclusion: The results revealed that self-traction exercise activated blood flow through the extension and contraction of muscles, effectively increasing the function of the muscles around the vertebrae.

• Steel and Composite Structures
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• v.44 no.3
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• pp.407-421
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• 2022

Prefabricated hybrid wind turbine towers (WTTs) are promising due to height increase. This study proposes the use of ultra-high performance concrete (UHPC) to develop a new type of WTT without the need to use reinforcement. It is demonstrated that the UHPC WTT structure without reinforcing bars could achieve performance similar to that of reinforced concrete WTTs. To simplify the design of WTT, a design approach for the calculation of stresses at the horizontal joints of a WTT is proposed. The stress distribution near the region of the horizontal joint of the WTT structure under normal operating conditions and different load actions is studied using the proposed approach, which is validated by the finite element method. A further parametric study shows that the degree of prestressing and the bending moment both significantly affect the principal stress. The shear-to-torsion ratio also shows a significant influence on the principal tensile stress.