• Proceedings of the Korean Society of Precision Engineering Conference
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• 2003.06a
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• pp.1479-1482
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• 2003

The shock absorber is a part having a direct influence on the ride comfort, stability and dynamic load prediction of a vehicle. Thus, a rationally modeled shock absorber should be required in the dynamic analysis of vehicles. This thesis presents a modified model, based on Worden's hyperbolic tangent function, in order to fit experimental data on the velocity-damping force of a shock absorber. The hyperbolic tangent function correctly indicates the characteristics of a shock absorber. and has the advantage of containing physical causality. To evaluate the method, comparative evaluations of the linear model. the 5th polynomial model and Worden's model were carried out. The function presented in this paper is not only simple but also makes it possible to estimate the function coefficients easily and visually. In addition, it has the advantage of containing physical causality. Lastly, it effectively models the damping force of a shock absorber.

• Journal of the Korean Society for Precision Engineering
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• v.10 no.1
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• pp.114-125
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• 1993

Thermoelastoplastic analysis of a typical device consisting of fixed tube and movable case having an inital clearance in between, which is subjected to pressure and thermal load, has been carried out to examine the cause of malfunction mainly at high temperature condition, and to improve the design. Stresses, deformed shape, interface state and their effects on normal function of case are discussed by using finite element method. The extraction energy can be remarkably reduced by changing the configuration of tube from the present design (Parallel type) to the improved design (Tapered type). This effect has been proved by sustained cyclic function test.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1994.10a
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• pp.815-819
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• 1994

In this paper, the tensile strength in aluminum alloy 5052, Kevlar 49-fiber reinforced aluminum alloy laminates, and Glass-fiber reinforced aluminum alloy laminates, is statistically evaluated. Prepregs manufactured in Han Kuk Fiber is used and FRMLs is cured by Hot-Press. Standard statistical are used to determine the distribution function which best fits FRMLs strength data. The normal,lpg-normal, and two-parameter Weibull distrbuttion are evaluated using the Kolmogoorov-Smirnov goodness-of-fit test. At the 5% significance level, none of these distribution is rejected. The strength of Aluminum alloy 5052 is best fits to a normal distribution. However, the strength of Kevlar 49-fiber reinforced aluminum alloy laminates and Glass-fiber reinforced aluminum alloy laminates is best fits to a two-parameter Weibull distribution.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2006.05a
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• pp.525-526
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• 2006

The products designed by human sensibility and ergonomics are given good impression. Especially the touch feeling on the human skin is very useful sensibility for quality of products. Elasticity and viscosity of human skin is very important element in product design based on ergonomics. In this paper, we describe a sophisticated method for measurement of dynamic viscoelasticity characteristics of human skin. For this measurement, we developed a measurement system assembled with load cell, actuator, amplifier and data acquisition system. The $MATLAB^{TM}$ is used to analyze the data and fit a approximation curves.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2006.05a
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• pp.629-630
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• 2006

This paper present a design experience of supervisory control system platform for agile and intelligent manufacturing(AIM). Embodied integrated environment that can do in place that do work direction, analysis command file generation, achievement using Petrinet-type Graphical Language(PGL) in proposed Supervisory Control System. Also, embodying whole system software in Modular done form, did to have extensity to fit in developer's requirement.

• Journal of the Korean Society for Precision Engineering
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• v.18 no.2
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• pp.126-131
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• 2001

One of the major obstacles in testing or evaluating precisely the thermal behavior of a machine tool is the difficulty in measuring the heat transfer coefficients on the surfaces by a conventional method. This paper presents a new approach based on the inverse method to identify the values of heat transfer coefficients by using temperature changes measured on the surfaces of a machine tool during a short period in its operating. In the present method, a machine tool structure is modeled by the finite element method and the characteristic curves of the temperature change at several points on machine tool surfaces are theoretically derived in the form that they contain the heat transfer coefficient as an unfixed heat source are approximated so that the theoretical characteristic curves of temperature change fit the measured ones as closely as possible.

• Journal of the Semiconductor & Display Technology
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• v.6 no.1 s.18
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• pp.31-36
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• 2007

Effect of coulomb friction and backlash on the single loop position control has been studied for the precision position control. We have showed the limit cycle on the single loop system which used a ball screw that had the backlash. Also, we have made an inner loop with a classical velocity and torque controller which was forcing the current of d axis to be zero by using a permanent-magnet synchronous motor and composed the outer loop with linear encoder for sensing a position of the loader. Also, we have used least squares fit(LSF) observer for reducing noise when we got velocity from position outputs. We have shown a good result by using the dual loop through simulation and experiment.

• Journal of the Korean Society for Precision Engineering
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• v.13 no.3
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• pp.132-140
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• 1996

This paper developes a torsional vibration model of heavy duty truck drive line for simulation of a driving rattle, which causes very annoying noise to driver at the full load driving condition. Test results show a peak in the fit plots at the frequency of the 2nd harmonics of propeller shaft revolution. A 10 d.o.f. lumped parameter nonlinear torsional vibration model is constructed and engine torque variation is calculated from P- .theta. diagram. Time responses are simulated and compared with the test results, which show fairly good agreement. The effects of paramenter change are investigated, and the optimum configuration is proposed.

• Journal of the Korean Society for Precision Engineering
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• v.11 no.5
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• pp.75-87
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• 1994

The demand for automatic manufacturing systems is increasing. One of the crucial obstacles to the Flexible Manufacturing System(FMS) is the lack of excellent strategies for efficient operations. The aim of this research is constructing an automaton scheme in the low level of factories where various machineries are involved. An operating strategy is established for an automation unit named as a cell which resides between the upper level computers and manufacturing shop floor. The cell is defined to fit into the total manufacturing system. The defined cell has more functions than conventional cells. A scheduling scheme is adopted for the shop floor operations. A set of software has been developed and tested through simulations and shop floor experiments.

• The Journal of Advanced Prosthodontics
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• v.13 no.2
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• pp.89-99
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• 2021

PURPOSE. This study aimed to compare the accuracy (trueness and precision) of interim crowns fabricated using DLP (digital light processing) according to post-curing time. MATERIALS AND METHODS. A virtual stone study die of the upper right first molar was created using a dental laboratory scanner. After designing interim crowns on the virtual study die and saving them as Standard Triangulated Language files, 30 interim crowns were fabricated using a DLP-type 3D printer. Additively manufactured interim crowns were post-cured using three different time conditions-10-minute post-curing interim crown (10-MPCI), 20-minute post-curing interim crown (20-MPCI), and 30-minute post-curing interim crown (30-MPCI) (n = 10 per group). The scan data of the external and intaglio surfaces were overlapped with reference crown data, and trueness was measured using the best-fit alignment method. In the external and intaglio surface groups (n = 45 per group), precision was measured using a combination formula exclusive to scan data (10C2). Significant differences in accuracy (trueness and precision) data were analyzed using the Kruskal-Wallis H test, and post hoc analysis was performed using the Mann-Whitney U test with Bonferroni correction (α=.05). RESULTS. In the 10-MPCI, 20-MPCI, and 30-MPCI groups, there was a statistically significant difference in the accuracy of the external and intaglio surfaces (P<.05). On the external and intaglio surfaces, the root mean square (RMS) values of trueness and precision were the lowest in the 10-MPCI group. CONCLUSION. Interim crowns with 10-minute post-curing showed high accuracy.