• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.24 no.8 s.179
• /
• pp.1917-1922
• /
• 2000

The split Hokinson pressure bar(SHPB) test has been used to find the mechanical property of materials at high strain rate. A tensile split Hopkinson pressure bar test system is developed and the threaded tensile specimen and the split collar are placed between elastic bars. When the compressive elastic wave generated by a striker is transferred from the transmit bar to the incident bar, some elastic wave is reflected at the threaded parts of the specimen and the transmit bar. This reflected wave can interfere with the transmitted wave. A proper length of elastic bars and the location of strain gage in these elastic bars are determined to avoid this interference. In order to avoid the interference of elastic wave reflected at the threaded parts of specimen and elastic bar, the length of transmit bar must be longer than that of incident bar. Strain gage in transmit bar must be located as close as possible from the interface of a transmit bar and specimen. In the developed tensile SHPB test system, A12011-T3 and A17075-T6 are tested to get the true stress-strain relation in the range of strain rate at $10^3/sec$

• Korean Journal of Applied Biomechanics
• /
• v.32 no.4
• /
• pp.128-133
• /
• 2022

Objective: This study was executed to compare and analyze shoulder muscle activation while using an inelastic bar and elastic bar during overhead press exercise. The stability and coordination of shoulder joints will be investigated by measuring and analyzing the EMG of the upper and lower arm muscles. Method: A total of 20 university male students were recruited by dividing into 2 groups; 10 elastic bar participants (age: 20.17 ± 0.41 yrs, height: 174.31 ± 3.34 cm, weight: 74.68 ± 5.65 kg) and 10 inelastic bar participants (age: 20.09 ± 0.23 yrs, height: 173.53 ± 4.11 cm, weight: 75.32 ± 3.31 kg) participated in this study. Results: The EMG analysis results of the four muscles measured in this study showed that there was no difference between the left and right muscles between the groups in Upper Trapezius muscle. In Deltoid, Infraspinatus, and Rectus Abdominis muscles, the elastic bar group was significantly higher than the inelastic bar group between groups, and there was no difference between left and right. Conclusion: Among the four muscles measured in this study, there was no difference between left and right in Deltoid, Infraspinatus, and Rectus Abdominis, but the elastic bar showed significantly higher muscle activity than the inelastic bar. Therefore, it was found that the elastic bar increases muscle activation during exercise than the inelastic bar, and in particular, it further increases muscle activation of the arms and torso, and exercise using the elastic bar can increase neuromuscular stabilization.

• Journal of the Korean Recycled Construction Resources Institute
• /
• v.3 no.2
• /
• pp.159-164
• /
• 2015

This paper presents results on a study of the Rayleigh wave scattering in concrete with a steel bar using transient elastic waves. To study the characteristics of the scattered waves induced by a steel bar in concrete, a three-dimensional finite element method was adopted. A case for elastic wave propagation parallel to the steel bar is discussed. The effect of the cover thickness and steel bar diameter on the Rayleigh wave was studied. To confirm the numerical investigations, a concrete specimen containing a steel bar was made, and corresponding transient elastic wave experiments were conducted. It is believed that the result of this study can serve as an important reference in a nondestructive evaluation of concrete with a steel bar.

• Structural Engineering and Mechanics
• /
• v.49 no.2
• /
• pp.273-283
• /
• 2014

According to deformation features of pre-twisted bar, its elastic bending and torsion buckling equation is developed in the paper. The equation indicates that the bending buckling deformations in two main bending directions are coupled with each other, bending and twist buckling deformations are coupled with each other as well. However, for pre-twisted bar with dual-axis symmetry cross-section, bending buckling deformations are independent to the twist buckling deformation. The research indicates that the elastic torsion buckling load is not related to the pre-twisted angle, and equals to the torsion buckling load of the straight bar. Finite element analysis to pre-twisted bar with different pre-twisted angle is performed, the prediction shows that the assumption of a plane elastic bending buckling deformation curve proposed in previous literature (Shadnam and Abbasnia 2002) may not be accurate, and the curve deviates more from a plane with increasing of the pre-twisting angle. Finally, the parameters analysis is carried out to obtain the relationships between elastic bending buckling critical capacity, the effect of different pre-twisted angles and bending rigidity ratios are studied. The numerical results show that the existence of the pre-twisted angle leads to "resistance" effect of the stronger axis on buckling deformation, and enhances the elastic bending buckling critical capacity. It is noted that the "resistance" is getting stronger and the elastic buckling capacity is higher as the cross section bending rigidity ratio increases.

• 한국기계연구소 소보
• /
• s.17
• /
• pp.99-109
• /
• 1987

Mechanisms with fully elastic members must consider both inertial forces due to the rigid motion of mechanisms and due to the elastic vibration of links. The main objectives of the kineto-elasto static and dynamic analyses are to calculate the quasi-static and the time-domain responses, respectively. An iterative transfer matrix method is used for a four-bar, fully elastic linked mechanism. Houbolt direct integration scheme is incorporated for the inertial effects due to the elastic link vibration. The analytical results are compared with the experimental responses and both responses show in good agreement.

• Architectural research
• /
• v.13 no.3
• /
• pp.41-47
• /
• 2011

A study on the free vibration analysis of elastic bar is described in this paper. In order to determine the natural frequencies of bars, a bar element is developed by using isogeometric formulation. The B-spline is introduced to represent the geometry of bar and the same geometric definition is also used to define its unknown displacement field in isogeometric formulation. Therefore, the stiffness and mass matrices are derived by the order-free B-spline basis function. The efficiency and accuracy of the present isogeometric bar elementis demonstrated by using several numerical tests. From numerical results, it is found to be that the present isogeometric element produces very accurate natural frequencies of bars. Finally, the present isogeometric solutions are provided as future reference solutions.

• Journal of The Korean Society of Integrative Medicine
• /
• v.8 no.2
• /
• pp.109-119
• /
• 2020

Purpose : The purpose of this study was to investigate the effects of a combined exercise program using a ballet bar and elastic bands on the body composition, physical strength, and postural correction of middle-aged women. Methods : The subjects were 28 middle-aged women with no ballet experience. They were divided into an experimental group (n=14; exercise group) and a control group (n=14; non-exercise group) through random sampling. The experimental group underwent an exercise program using a ballet bar and elastic bands for 50 minutes twice a week for 12 weeks, whereas the control group performed no exercise. The subjects in both group had their body composition, physical fitness, and postural angles measured before and after the intervention. A paired t-test was used to compare pre- and post-test values within each group, and a two-way repeated measures ANOVA was employed to compare pre- and post-test changes between the two groups. Results : Regarding body composition, statistically significant differences in BMI (p<.05), body fat percentage (p<.001), and muscle mass (p<.001) were observed between the two groups before and after the intervention. For physical fitness, the experimental group showed statistically significant increases in quick reflexes (p<.001), muscle endurance (p<.001), and muscle strength (p<.001). For postural correction, the experimental group exhibited statistically significant decreases in all variables: the head (p<.001), shoulder (p<.001), cervical tilt (p<.001), right-left pelvic tilt (p<.001), and anterior-posterior pelvic tilt (p<.001). Conclusion : A combined exercise program using a ballet bar and elastic bands had positive effects on the body composition, physical fitness, and postural correction of middle-aged women.

• Computers and Concrete
• /
• v.7 no.4
• /
• pp.317-329
• /
• 2010

The paper describes localization of deformation in a bar under tensile loading. The material of the bar is considered as non-linear viscous elastic and the bar consists of two symmetric halves. It is assumed that the model represents behavior of the quasi-brittle viscous material under uniaxial tension with different loading rates. Besides that, the bar could represent uniaxial stress-strain law on a single plane of a microplane material model. Non-linear material property is taken from the microplane material model and it is coupled with the viscous damper producing non-linear Maxwell material model. Mathematically, the problem is described with a system of two partial differential equations with a non-linear algebraic constraint. In order to obtain solution, the system of differential algebraic equations is transformed into a system of three partial differential equations. System is subjected to loadings of different rate and it is shown that localization occurs only for high loading rates. Mathematically, in such a case two solutions are possible: one without the localization (unstable) and one with the localization (stable one). Furthermore, mass is added to the bar and in that case the problem is described with a system of four differential equations. It is demonstrated that for high enough loading rates, it is the added mass that dominates the response, in contrast to the viscous and elastic material parameters that dominated in the case without mass. This is demonstrated by several numerical examples.

• Journal of The Korean Society of Agricultural Engineers
• /
• v.46 no.1
• /
• pp.41-51
• /
• 2004

FRP re-bar in concrete structures could be used as a substitute of steel re-bars for that cases in which aggressive environment produce high steel corrosion, or lightweight is an important design factor, or transportation cost increase significantly with the weight of the materials. But FRP fibers have only linearly elastic stress-strain behavior; whereas, steel re-bar has linear elastic behavior up to the yield point followed by large plastic deformation and strain hardening. Thus, the current FRP re-bars are not suitable concrete reinforcement where a large amount of plastic deformation prior to collapse is required. The main objectives of this study in to evaluate the tensile behavior and the fracture mode of hybrid FRP re-bar. Fracture mode of hybrid FRP re-bar is unique. The only feature common to the failure of the hybrid FRP re-bars and the composite is the random fiber fracture and multilevel fracture of sleeve fibers, and the resin laceration behavior in both the sleeve and the core areas. Also, the result of the tensile and interlaminar shear stress test results of hybrid FRP re-bar can provide its excellent tensile strength-strain and interlaminar stress-strain behavior.

• Transactions of the Korean Society of Machine Tool Engineers
• /
• v.11 no.4
• /
• pp.82-88
• /
• 2002

Copper bus-bar is made by drawing process and used in many part of industry. Ohen design drawing die for copper bus-bar, design factor is focused on the deformation of die-land by drawing force and shrink fit. In this paper it is analyzed to determine shrink fit value by shrink fit analysis program which is used with APDL/UIDL language in a commercial FEM package, ANSYS. The shrink fit analysis has been developed that enables optimal desist of the dies taking into account the elastic deflections. Elastic deflection is generated in shrink fitting the die inserts and that caused by the stresses generated using DEFORM software for drawing process analysis. This data can be processed as load input data fir a finite element die-stress analysis. Process simulation and stress analysis are thus combined during the drawing die design. The stress analysis of the dies is used to determine optimized dimension of die-land.