• Design & Manufacturing
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• v.16 no.4
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• pp.17-23
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• 2022

Recently, several studies are being conducted to achieve a curvature of 180° or more for the edge of the display glass. The thermocompression molding process is applied to the manufacture of curved glass, and high hardness G5 graphite is used as the mold material to withstand the impact applied to the mold. G5 graphite has high hardness and strong brittleness, which makes tool wear and surface damage easy during machining. Therefore, the demand for diamond-coated tools with good mechanical properties is increasing in the G5 machining field. In this study, the optimal cutting conditions and machinability of a nanodiamond (NCD) coated ball end mill being developed by a tool manufacturer were analyzed and evaluated. For this purpose, the same test was performed on the microdiamond (MCD) coated ball end mill and compared together. In summary, the machinability of MCD and NCD coated tools showed better cutting performance at a cutting speed of 282 m/min, a feed rate of 1,400 mm/min, and a radial depth of cut of 0.08 to 0.1 mm.

• Korean Journal of Applied Biomechanics
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• v.15 no.2
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• pp.41-55
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• 2005

In this study, weight carrying pattern analysis and comparison method of four foot region were suggested. We used three types of club(driver, iron7, pitching wedge). This analysis method can compare between top class golfer and beginner. And the comparison data can be used to correct the swing pose of trainee. If motion analysis system, which can measure the swing speed and instantaneous acceleration at the point of hitting a ball, is combined with this plantar foot force analysis method, new design development of golf shoes to increase comfort and ball flight distance will be available. 1. Regional change of force acting, in address, is evenly distributed on both feet. In back swing top, 76% on right foot, 75% on left foot as impact, and 86% on left foot as finish. As regional force acting, in address, pros get high marks on rare and inside of right foot and rare and outside for amateurs. In back swing top, it is higher as fore and inside of left foot, pros as rare part of right foot and amateurs as forefoot. In impact, it is higher for pros and amateurs in outside and rare part of left foot and fore and inside of right foot. In finish, for both pros and amateurs, it is higher for outside and rare parts of left foot. 2. For each club, forces are evenly distributed on both feet in address. In back swing top, the shorter a club is, the higher impact on right foot and the higher finish distribution on left foot. For all the clubs used, in each region, pros get higher on rare and inside of right foot and as amateurs on rare and outside of left foot in address. In back swing top, for all clubs, pros get higher on rare and outside of right foot as fore and outside for amateurs. In impact acting, for all clubs, rare and outside of left foot get higher. In finish, force concentrates on rarefoot. 3. On both feet force, right foot forces of amateurs is higher than those of pros in back swing top. In impact and finish, pros get higher on left foot.

• Transactions of the Korean Society of Automotive Engineers
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• v.14 no.1
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• pp.79-85
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• 2006

CFRP(Carbon Fiber Reinforced Plastics) of the advanced composite materials as structural materials for vehicle, has a wide application in light-weigh structural materials of airplanes, ships and automobiles because of high strength and stiffness, However, there is a design variable to be considered in practical application of the laminate composite materials, these materials are vulnerable to transverse impact. This paper is to study the effects of stacking sequence and curvature on the penetration characteristics of composite laminate shell. They are stacked to $[0_3/90_3]S,\;[90_3/0_3]s\;and\;[0_2/90_3/0]s,\;[90_2/0_3/90]s$ and their interlaminar number two and four. They are manufactured to various curvature radius (R=100, 150, 200mm and $\infty$), When the specimen is subjected to transverse impact by a steel ball, the velocity of the steel ball was measured both before and after impact by determing the time for it to pass two ballistics-screen sensors located a known distance apart. The critical penetration energy of specimen A and B with less interfaces were a little higher than those of C and D. As the curvature increases, the critical penetration energy increases linearly because the resistance to the in-plane deformation as well as bending deformation increases, which need higher critical penetration energy. The specimen A and C have higher critical penetration energy than B and D because of different stacking sequences. We examined crack length through a penetration test. For the specimen A with 2interfaces, the longest circumferential direction crack length were observed on the first interface from the impact point. For the specimen B 4-interface, the longest circumferential direction crack length were observed on the second interface from the impact point.

• Physical Therapy Rehabilitation Science
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• v.9 no.1
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• pp.25-35
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• 2020

Objective: To compare the effects of joint mobilization, gym ball exercises, and breathing exercises on breathing pattern disorders and joint position sense in persons with chronic lower back pain. Design: Three-group pretest-posttest design. Methods: Thirty-six individuals with chronic low back pain who were undergoing a postural correction and vertebral movement at a rehabilitation center participated in this study. The subjects were randomly divided into the joint mobilization group (n=12), gym ball exercises group (n=12), and the breathing exercises group (n=12). The exercises were applied for 40 minutes a day, twice a week for a total of 12 weeks. Measurement tools included the end-tidal CO₂ (ETCO₂), respiration rate (RR), breath hold time, Nijmegen Questionnaire (NQ), excursion, and joint position error (JPE). Results: The groups showed significant differences in the ETCO₂, RR, NQ, Excursion and JPE test before and after the intervention (p<0.05). The differences between the groups were significant in the group that received the gym ball and breathing exercises in ETCO₂ and RR (p<0.05). The differences between the groups were most significant in the group that received breathing exercises in NQ and excursion (p<0.05). The differences between the groups were significant in the group that received the gym ball and breathing exercises in JPE Lt. and Rt. (p<0.05). Conclusions: All three interventions had a significant impact on the biomechanical changes, respiratory variables, and joint position sense in participants with chronic lower back pain. Breathing exercises were found to be particularly effective in improving respiratory parameters.

• 제어로봇시스템학회:학술대회논문집
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• 2002.10a
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• pp.36.6-36
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• 2002

$\textbullet$ Human motion consists of continual impact with environment $\textbullet$ External impulse model of kicking motion $\textbullet$ Models of aerodynamic forces $\textbullet$ Analysis of external impulse according to posture $\textbullet$ Simulation of a soccer ball trajectory

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.24 no.6
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• pp.483-492
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• 2014

Uncomfortable feelings of occupants by indoor floor impact noise in a residential building are not accurately represented by the floor impact noise from a standard impact source. It is due to the characteristics of standard impact sources, which are different from the impact forces produced by occupants. It varies significantly by impact source, and it is not easy to be replicated for testing. As a result, the indoor floor impact noise under different acoustic conditions cannot be directly compared. Using frequency response function(FRF), which represents the input-output relationships of a dynamic system, it is possible to examine the characteristics of the system. Especially, FRF can predict the response of a linear dynamic system subjected to various excitation. To determine the relationship between impact force and the corresponding response of dynamic system in residential building, the acceleration response of a concrete slab and the floor impact noise in the living room, produced by bang-machine and rubber-ball excitation, were measured. The test results are compared to the estimates based on FRF and impact force spectrum.

• Proceedings of the Korea Concrete Institute Conference
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• 1995.04a
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• pp.350-354
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• 1995

This paper is about impact behavior of cylinder container, made of steel fiber reinforced polymer-impregnated concrete(SFPIC), for intermediate and low level radwaste disposal. In order to obtain the material properties of the SFPIC, steel ball impact tests were done to SFPIC beams and its simulation by finite element method was performed. By using the material properties in finite element impact analysis of the SFPIC concrete cylinder, we obtained impact behavior of the cylinder.

• Proceedings of the KSME Conference
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• 2007.05a
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• pp.183-188
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• 2007

In this paper, we propose a 2D-FE model in single impact with combined physical factors to obtain a unique residual stress by shot peening. Applied physical parameters include elastic-plastic deformation of shot ball, material damping coefficients, strain rate, dynamic friction coefficients. Single impact FE model consists of 2D axisymmetric elements. The FE model with combined factors showed converged and unique distributions of surface stress, maximum compressive residual stress and deformation depth. Further, in contrast to the FE models with rigid shot and elastic deformable shot, FE model with plastic deformable shot produces residual stresses very close to experimental solutions by X-ray diffraction. We therefore validated the 2D FE model with combined peeing factors and plastic deformable shot. This FE model will be a base of the 3D FE model for residual stresses by multi-impact shot peening.

• Transactions of the Korean Society of Automotive Engineers
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• v.21 no.6
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• pp.8-15
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• 2013

Wide range frequency pulses occur in a car crash test. Until now, low frequency under 400Hz has been used to determine an airbag deployment criteria. Also, FIS (Front Impact Sensor) has been used to detect the crash pulse in early stage. Nowadays, technology to determine an airbag delpoyment criteria by using a high frequency crash pulse without FIS is being focused on. In this paper, the signal transmissibility of high frequency pulse for two different cars was studied. Also, signal transfer test of high frequency pulse was done by using a high speed ball impact. Signal runtime of the frontal impact is compared with that of the side impact. The signal transmissibility difference due to the car structure difference was discussed and structure change for improving the signal transmissibility was proposed.

• Transactions of the Korean Society of Mechanical Engineers
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• v.19 no.3
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• pp.623-630
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• 1995

The impulse response functions (force-strain relations) for Euler-Bernoulli and Timoshenko beams are considered. The response of a beam to a transverse impact force is numerically obtained with the convolution approach using the impulse response function obtained by Laplace transform. Using this relation, the impact force history is determined in the time domain and results are compared with those from Hertz's contact law. The parameters of timpact force model are identified using the recovered force and compared with the Hertz's contact model. In order to verify the proposed algorithm, measurements were done using an impact hammer and a steel ball drop test and these results are also compared with the simulated values.