• Korean Journal of Oriental Medicine
• /
• v.14 no.3
• /
• pp.103-111
• /
• 2008

Recently, skin diagnosis has been suggested as a promising tool for discrimination of Sasang Constitution, reported by examining the skin characteristics such as thickness, stiffness, slip, and skin textures like wrinkles and furrows. However, the works had a limitation in that clinical decision on the skin characteristics was made by relying upon oriental medicine doctors' subjective sense of touch. In order to objectify the skin diagnosis and claim its efficacy on the discrimination of the Sasang Constitutions, it is necessary to demonstrate its discrimination capability by providing numerical values in terms of physical quantities obtained from measurements using today's sensors and equipment technologies, which motivated this work as a priliminary step towards objectification of skin diagnosis. The skin characteristics focused in this work is the slip property of the back-hand skin that has been exploited using the dynamic friction measurement system. First, curved geometric effects of the back-hand skin on the measured lateral/vertical force signals were estimated using the artificially designed silicon coated structures, which led to a suggestion on a quality controlled experimental design based upon a empirical analysis model. Second, the experimental design thus suggested has been applied to the measurement of dynamic friction coefficients for two healthy male subjects of Taeumin (TE) and Soyangin (SY), respectively. The result shows that the dynamic friction coefficient is less for the SY subject than for the TE subject around the area of the skin used for diagnosis by the oriental medicine doctor, implying the TE subject's skin is more slippery than the SE subject's that is consistent with the oriental medicine doctor's diagnosis. Hopefully, this work can provide guidelines for obtaining quality data in friction measurement to be collected for discussion on the efficacy of the skin diagnosis and its objectification through statistical analysis.

• Journal of Biomedical Engineering Research
• /
• v.21 no.3 s.61
• /
• pp.295-301
• /
• 2000

It is known that among many factors, relative micromotion at bone/implant interfaces can hinder bone ingrowth into surface pores of an implant. Loading conditions, mechanical properties of spinal materials, friction coefficients at the interfaces and geometry of spinal segments would affect the relative micromotion and spinal stability. A finite clement model of the human lumbar spine segments (L4-L5) was constructed to investigate the mechanical sensitivity at the interfaces between bone and cage. Relative micromotion. Posterior axial displacement. bone stress, cage stress and friction force were predicted in changes of friction coefficients, loading conditions. bone density and age-related material/geometric properties of the spinal segments. Relative micromotion (slip distance in a static loading means relative micromotion in routine activity) at the interfaces increased significantly as the mechanical properties of cancellous bone, annulus fibers or/and ligaments decrease or/and as the friction coefficient at the interfaces decreases. The contact normal force at the interfaces decreased as cancellous bone density decreases or/and as the friction coefficient increases A significant increase of slip distance at anterior annulus occurred with an addition of torsion to compressive preload. Relative micromotion decreased with an increase of disc area. In conclusion. relative micromotion, stress response. Posterior axial displacement and contact normal force are sensitive to the friction coefficient of the interfaces, bone density, loading conditions and age-related geometric/material changes.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.11 no.5
• /
• pp.112-118
• /
• 2003

The friction coefficients of the rubber for clutch master cylinder were experimentally measured in this study. The cylindrical rubber samples for primary cup-seal and secondary cup-seal were tested against the aluminum or the steel plates of master cylinder housing under the various conditions of brake oil temperatures and normal loads. Dry sliding friction coefficients were also measured under various load conditions. The test revealed following results. First, the friction coefficient under fluid lubrication condition in general decreases, as the oil temperature or normal load increases. Second, the steel plate of low surface roughness yielded comparatively low friction coefficient on the range of 0.30∼0.67. On the other hand, the aluminum plate of high surface roughness yielded high friction coefficient on the range of 0.31∼1.15. Third, the friction coefficient of dry surface contact decreases as the normal load increases. This is contrary to the general principle of friction coefficient between metal plates.

• Proceedings of the Korean Society of Tribologists and Lubrication Engineers Conference
• /
• 2001.06a
• /
• pp.55-63
• /
• 2001

Friction and wear properties of brake friction materials containing different metal fibers (Al, Cu or Steel fibers) were investigated using a pad-on-disk type friction tester. Two different materials(gray iron and Al-MMC)) were used for disks rubbing against the friction materials. Results from ambient temperature tests revealed that the friction material containing Cu fibers sliding against cast iron disk showed a distinct negative ${\mu}$-ν (friction coefficient vs. sliding velocity) relation implying possible stick-slip generation at low speed. The negative ${\mu}$-ν relation was not observed when the Cu-containing friction materials were rubbed against the. Al-MMC counter surface. As applied loads increased, friction materials showed higher friction coefficients comparatively. Friction materials slid against cast iron disks exhibited higher friction coefficients than Al-MMC disks during high temperature tests. On the other hand, high temperature test results suggested that copper fibers in the friction material improved fade resistance and the steel fibers were not compatible with Al-MMC disks showing severe material transfer and erratic friction behavior during sliding at elevated temperatures.

• Journal of the Korean Society for Railway
• /
• v.11 no.2
• /
• pp.176-181
• /
• 2008

This paper presents results from experimental analysis of a friction-driven wheel responsible for generating wheel squeal noise. Squeal noise generating mechanism has been examined under the laboratory condition by the model rig on a small scale. Creep characteristics and squeal noise were observed by changing the possible variables, such as relative velocities and friction coefficients in time- and frequency-domain.

• The KSFM Journal of Fluid Machinery
• /
• v.2 no.4 s.5
• /
• pp.57-64
• /
• 1999

The prediction method of the performance and aerodynamic noise from a sirocco fan was developed and compared with measured data. To predict the performance of the sirocco fan, the well-known slip coefficients and various loss models were tested and applied to forward curved sirocco impellers. Using loss models proposed for both impeller and casing, the predicted performance characteristics were in good agreement with measured ones by an ANSI test plenum. Various scaling models for aerodynamic noise from the sirocco fan were evaluated and tested against measured power levels in terms of flow coefficient. It was shown that the turbulent broadband sound power from the sirocco fan can be modeled successfully by trailing edge noise.

• Steel and Composite Structures
• /
• v.2 no.4
• /
• pp.277-296
• /
• 2002

A research investigation of single bolt lap-plate connection load-deformation behavior is presented. Each important characteristic of this behavior is evaluated and two methods for analytically approximating the behavior are developed and presented. The first of these methods is a component method in which the behavior of the connection is modeled as a combination of the behavior of the parts. The second method utilizes a number of parametric relationships that relate the connection parameters to coefficients of two non-linear continuous analytical curves. The test results from four independent experimental programs that investigated the behavior of single bolt lap-plate connections are used in the development and verification of these methods.

• Journal of the Korean Society for Precision Engineering
• /
• v.26 no.6
• /
• pp.106-113
• /
• 2009

A 6-DOF precision stage was developed based on parallel kinematics structure with flexure hinges to eliminate backlash, stick-slip and friction and to minimize parasitic motion coupled with motions in the other-axis directions. For the stage, lever linkage mechanism was devised to reduce the height of system for the enhancement of horizontal stiffness. Frequency response comparison between experimental results and mathematical model extracted from dynamics of the stage was performed to identify the system parameters such as spring constants and damping coefficients of actuation modules, which cannot be calculated accurately by analytic methods owing to their complicated structures. This newly developed precision stage and its identified model will be very useful for precision positioning and control because of its high accuracy and non-coupled movement.

• Journal of Power System Engineering
• /
• v.20 no.6
• /
• pp.71-79
• /
• 2016

This paper introduces the design method of the centrifugal turbo fan and the process of developing the design program of it. The developed design program confirmed the applicability by experimental performance data. Here, we proposed new velocity coefficients and considered various losses such as impeller inlet loss, vane passage flow loss, casing pressure loss, recirculation loss power, and disk friction loss power. Especially, the inlet and outlet widths of the impeller were newly determined by reflecting the experimental results. As a result, this fan design program shows a good performance result regardless of the types of impeller and is expected to be a very useful design tool.

• KSTLE International Journal
• /
• v.3 no.1
• /
• pp.49-53
• /
• 2002

Inconel 690 for nuclear steam generator tube has more chromium than the conventionally used Inconel 600 in order to increase the corrosion resistance. TD evaluate the tribological characteristics under fretting condition the fretting tests as well as sliding tests were carried out in elevated temperature water environment. Fretting tests of the cross-cylinder type were done under various vibrating amplitudes and applied normal loads in order to measure the friction forces and wear volumes. Also, the conventional sliding tests of pin-en-disk type were carried out to compare the test results. In fretting, the friction was very sensitive to the load and the amplitude. The friction coefficient decreased with increasing load and decreasing amplitude. Also, the wear of Inconel 690 can be predictable using the work rate model. Depending on normal loads and vibrating amplitudes, distinctively different wear mechanisms and of ten drastically different wear rates can occur. It was fecund that the fretting wear coefficients in water were increased as increasing the temperature of water.