• Journal of Biomedical Engineering Research
• /
• v.21 no.3 s.61
• /
• pp.285-293
• /
• 2000

Age-related changes in the geometry of human lumbar spine would lead to changes of its mechanical behaviors. To investigate the effects of the geometric changes, no age-related changes in the material/mechanical properties were considered. Using the finite element method. two age-related models of lumbar spine segments (L3-L4) were constructed. The annulus of the models was modeled as laminate composite elements with 16 layers and 6 materials. The spinal stiffness and facet reaction of the lumbar spine increased with the age-related geometric changes in various combined loadings. Fiber and transverse tensile strains of the inner annulus. cancellous bone stress and end-plate stress decreased with the age-related geometric changes whereas fiber/layer compressive strains of the annulus. facet reaction. ligament reaction and end-plate rigidity increased. Consequently, it appears that in the normal age-related deterioration of discs, the age-related geometric change contributes to the increase of spinal stiffness (the decrease in range of the motion segment), preventing an excessive deformation of the disc.

• Steel and Composite Structures
• /
• v.21 no.1
• /
• pp.157-175
• /
• 2016

It was found that the lateral stiffness changes obvious at the transfer position of the section configuration from SRC to RC. This particular behavior leads to that the transfer columns become as the important elements in SRC-RC hybrid structures. A comprehensive study was conducted to investigate the seismic behavior of SRC-RC transfer columns based on a low cyclic loading test of 16 transfer columns compared with 1 RC column. Test results shows three failure modes for transfer columns, which are shear failure, bond failure and bend failure. Its seismic behavior was completely analyzed about the failure mode, hysteretic and skeleton curves, bearing capacity deformation ability, stiffness degradation and energy dissipation. It is further determined that displacement ductility coefficient of transfer columns changes from 1.97 to 5.99. The stiffness of transfer columns are at the interval of SRC and RC, and hence transfer columns can play the role of transition from SRC to RC. All specimens show similar discipline of stiffness degradation and the process can be divided into three parts. Some specimens of transfer column lose bearing capacity swiftly after shear cracking and showed weak energy dissipation ability, but the others show better ability of energy dissipation than RC column.

• Journal of the Korean Society of Clothing and Textiles
• /
• v.9 no.3
• /
• pp.35-44
• /
• 1985

This research explored the effects of abrasion, laundering, and abrasion/laundering interaction upon wear of 15 durable nonwoven fabrics. Wear was measured in terms of changes in tensile strength and stiffness. The test materials consisted of nine different dry-laid commercial interfacing fabrics of various fiber contents and six spunbonded poyester and polypropylene fabrics. Three fixed levels of abrasion and four fixed levels of laundering made up the 3$\times$4 factorial analysis used for the experiment and the analysis of variance. Findings revealed that abrasion had a greater effect than laundering on strength and stiffness of the tested fabrics. Laundering seemed related to the particular fibers used and to the fixation quality of fiber bonds. Spunbonded webs performed better than dry-laid webs in retaining tensile strength Stiffness change occurred more readily than strength change. Lighter, flexible, stretchable fabrics seemed less easily abraded than heavier, stiff, less stretchable fabrics. The interfacing fabrics of 70/20/$10\%$ nylon/polyester/rayon blends with high crosswise stretchability effectively resisted wear caused by abrasion and laundering. Further research is recommended to study the effects of longer abrasion periods and additional laundering cycles o,1 wear qualities of nonwoven fabrics. Additional factors such as amount and fixation methods of bonding agents, the effect of shear distortion, seam construction, and drycleaning solvents could also be studied.

• Journal of the Korean Society of Manufacturing Process Engineers
• /
• v.15 no.2
• /
• pp.57-65
• /
• 2016

The suspension system of a subway vehicle is composed of $1^{st}$ and $2^{nd}$ springs. The suspension system is the most important parameter in determining the vibration ride comfort. If the $1^{st}$ suspension spring is designed as a spring with strong stiffness to improve the running stability at high speed, it causes vehicle vibrations. In this paper, by testing and analyzing changes of the characteristics of Chevron springs, which have been the primary suspension springs used for about 20 years, we study how changing the characteristics affects vehicle acceleration and ride comfort. The lateral and longitudinal vibrational ride comfort index levels were lower than the vertical ones. Therefore, as increasing the stiffness of Chevron springs has the greatest effect on the vertical vibrational ride comfort index level, a countermeasure for vertical vibration reduction is needed when the stiffness increases owing to aging. Finally, maintenance guidelines, including the replacement time for the Chevron rubber, were proposed based on these findings.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.31 no.11
• /
• pp.1077-1082
• /
• 2007

We present a micromechanical active amplifier, inspired from the principle of the outer hair cells in cochlea, amplifying both displacement and force. The present micromechanical active amplifier modulates the resonant carrier motion using the variable stiffness spring whose stiffness changes proportionally to the input motion. We design, fabricate, and characterize two types of the amplifiers A and B, each having the variable stiffness spring fur the maximum displacement gain and force gain, respectively. In the experimental study, the amplifier A shows the displacement gain of 5.62, which is 2.15 times larger than that of the amplifier 3. The amplifier B shows the force gain of 10.0, resulting in 1.26 times larger value compared to that of the amplifier A. We experimentally verify that the haircell-inspired micromechanical amplifiers are capable to amplify both displacement and force.

• Journal of the Korean Home Economics Association
• /
• v.31 no.2
• /
• pp.189-203
• /
• 1993

The objective of this study was to investigate the changes of the fabric absorbency, stiffness and antistatic property by using a fabric softner at laundering. The samples selected in this study were cotton and polyester fabrics. The cotton fabric was treated with 1/2 times(0.035%), 1 time(0.07%), 3 times(0.21%) and 10 times(0.7%) of the commercially suggested concentration (0.07%) of the fabric softner. And polyester fabric was done at 1 time(0.07%) of that. In order to examine the effect of the fabric by using a fabric softner, the abstraction of a surface active agent and quantitative analysis was performed by using a UV/VIS Spectroscopy and the correlations among the absorbency, stiffness and antistatic property was analyzed. The results obtained from this study were as follows; 1. In the cotton fabric, fabric softner gave the degradation of absorbency, and stiffness improvement was not shown by repeated fabric softner on the cotton fabric. 2. In the polyester fabric, the absorbency increased and the stiffness in creased very slightly. Specially, it is desirable to use fabric softner on the polyester due to improvement of antistatic property.

• Journal of International Academy of Physical Therapy Research
• /
• v.10 no.3
• /
• pp.1840-1848
• /
• 2019

Background : There is lack of studies on the effects of the bag-carrying style on the shoulder muscles and body alignment in adults with rounded shoulder posture (RSP). Objective: The purpose of this study was to investigate the effects of various bag-carrying styles on muscle tone, muscle stiffness and spinal alignment in 20 adults with RSP as they were walking on a treadmill. Design : Crossover Study Design. Methods: A subject performed treadmill walking for 15 minutes at a speed of 4 ㎞/ｈ while carrying three different types of bags: a backpack, a cross bag, and a shoulder bag. Results : The results showed that the main effect of timing was observed in the muscle tone for all the variables and in muscle stiffness only for the upper and lower trapezius muscles. As for the main effect of timing, the muscle tone of the upper trapezius and the pectoralis major significantly increased in all conditions, while the muscle tone of the lower trapezius significantly decreased in all conditions. The muscle stiffness of the upper trapezius significantly increased in all conditions, while the muscle stiffness of the lower trapezius significantly decreased in all conditions. As for the spinal alignment, the dimple distance data values significantly decreased for the cross-bag style. Conclusions : This study demonstrated that walking with a heavy bag, regardless of the bag-carrying style, increased muscle stiffness around the shoulders in adults with rounded shoulder posture, and walking with a cross-bag also induced changes in spinal alignment.

• Proceedings of the Korean Society for Technology of Plasticity Conference
• /
• 2006.05a
• /
• pp.349-352
• /
• 2006

The plastic deformation of polycrystalline materials is induced by changes of the microstructure when the loading is beyond the critical state of stress. Constitutive models for the crystal plasticity have the common objective which relates microscopic single crystals in the crystallographic texture to the macroscopic continuum point. In this paper, a new consistent tangent stiffness for the anisotropic elasto-viscoplastic analysis of polycrystalline deformation is developed, which can be used in the finite element analysis for the slip-dominated large deformation of polycrystalline materials. In order to calculate the consistent tangent stiffness, the state function is defined based on the consistency condition between the elastic and plastic stress. The rate of shearing increment($\Delta{\gamma}^{\alpha}$) is calculated with satisfying the consistency condition. The consistency condition becomes zero when the trial resolved shear stress($\tau^{{\alpha}^*}$) becomes resolved shear stress($\tau^{\alpha}$) at every step. Iterative method is utilized to calculate the rate of shearing increment based on the implicit backward Euler method. The consistent tangent stiffness can be formulated by differentiating the rate of shearing increment with total strain increment after the instant rate of shearing increment converges. The proposed tangent stiffness is applied to the ABAQUS/Standard by implementing in the ABAQUS/UMAT.

• Earthquakes and Structures
• /
• v.7 no.5
• /
• pp.891-906
• /
• 2014

The purpose of this study is to propose a modification factor to reflect the lateral stiffness modification when a step is located in flat plates. Reinforced concrete slabs with steps have different structural characteristics that are demonstrated by a series of structural experiment and nonlinear analyses. The corner at the step is weak and flexible, and the associated rotational stiffness degradation at the corner of the step is identified through analyses of 6 types of models using a nonlinear finite element program. Then a systematic analysis of stiffness changes is performed using a linear finite element procedure along with rotational springs. The lateral stiffness of reinforced concrete flat plates with steps is mainly affected by the step length, location, thickness and height. Therefore, a single modification factor for each of these variables is obtained, while other variables are constrained. When multiple variables are considered, each single modification factor is multiplied by the other. Such a method is verified by a comparative analysis. Finally, a complex modification factor can be applied to the existing effective slab width.

• Journal of Sensor Science and Technology
• /
• v.32 no.6
• /
• pp.386-390
• /
• 2023

Stiffness-engineered stretchable substrate technology has been widely used to produce stretchable displays, transistors, and integrated circuits because it is compatible with various flexible electronics technologies. However, the stiffness-engineering technology has never been applied to transistor-based stretchable strain sensors. In this study, we developed thin-film transistor-based strain sensors on stiffness-engineered stretchable substrates. We designed and fabricated strain-sensitive stretchable resistors capable of inducing changes in drain currents of transistors when subjected to stretching forces. The resistors and source electrodes of the transistors were connected in series to integrate the developed stretchable resistors with thin-film transistors on stretchable substrates by printing the resistors after fabricating transistors. The thin-film transistor-based stretchable strain sensors demonstrate feasibility as strain sensors operating under strains of 0%-5%. This strain range can be extended with further investigations. The proposed stiffness-engineering approach will expand the potential for the advancement and manufacturing of innovative stretchable strain sensors.