• The korean journal of orthodontics
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• v.38 no.4
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• pp.228-239
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• 2008

Objective: The aim of this study was to evaluate the strain induced in the cortical bone surrounding an orthodontic microimplant during insertion. Methods: A 3D finite element method was used to model the insertion of a microimplant (AbsoAnchor SH1312-7, Dentos Co., Daegu, Korea) Into 1 mm thick cortical bone with a pre-drilled hole of 0.9 mm in diameter. A total of 1,800 analysis steps was used to simulate the 10 turns and 5 mm advancement of the microimplant. A series of remesh in the cortical bone was allowed to accommodate the change in the geometry accompanied by the implant insertion. Results: Bone strains of well higher than 4,000 microstrain, the reported upper limit for normal bone remodeling, was observed in the bone along the whole length of the microimplant. At the bone in the vicinity of the screw tip, strains of higher than 100% was recorded. The insertion torque was calculated at approximately 1.2 Ncm which was slightly lower than those measured from the animal experiment using rabbit tibias. Conclusions: The insertion process of a microimplant was successfully simulated using the 3D finite element method which showed that bone strains from a microimplant insertion might have a negative impact on physiological remodeling of bone.

• The korean journal of orthodontics
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• v.39 no.4
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• pp.203-212
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• 2009

Objective: The aim of this study was to evaluate the strain induced in the cortical bone surrounding an orthodontic microimplant during insertion in a self-drilling manner. Methods: A 3D finite element method was used to simulate the insertion of a microimplant (AbsoAnchor SH1312-7, Dentos Co., Daegu, Korea) into 1 mm thick cortical bone. The shape and dimension of thread groove in the center of the cortical bone produced by the cutting flute at the apical of the microimplant was obtained from animal test using rabbit tibias. A total of 3,600 analysis steps was used to calculate the 10 turns and 5 mm advancement of the microimplant. A series of remesh in the cortical bone was allowed to accommodate the change in the geometry accompanied by the implant insertion. Results: Bone strains of well higher than 4,000 microstrain, the reported upper limit for normal bone remodeling, were observed in the peri-implant bone along the whole length of the microimplant. Level of strains in the vicinity of either the screw tip or the valley part were similar. Conclusions: Bone strains from a microimplant insertion in a self-drilling manner might have a negative impact on the physiological remodeling of cortical bone.

• Proceedings of the KSME Conference
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• 2005.11a
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• pp.220.2-220.2
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• 2005

• Journal of Sensor Science and Technology
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• v.9 no.1
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• pp.22-27
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• 2000

Amorphous FeCoSiB films with high saturation magnetostriction and excellent soft magnetic properties have been studied to evaluate their strain sensitivity. Films were subjected to a strain by bending of their substrates, which caused a change in the magnetic anisotropy of films via magnetoelastic coupling. Films were exhibited a figure of merit $F=({\Delta}{\mu}/{\mu})/{\varepsilon}$ (change in film permeability $\mu$ per unit strain $\varepsilon$) of $1.2{\times}10^5$, which is comparable with that of amorphous ribbons. To make a study of application of magnetostrictive films as strain sensor elements, we have prepared a micro-patterned film by means of the photolithography and ion milling processes. Impedance change in the patterned films, when strain was applied, was measured over the frequency range from 1 MHz to 1 GHz. Reflecting a large value of figure of merit F, a variation of 46% impedance of films was shown at 100 MHz frequency when a strain of $300{\times}10^{-6}$ was applied.

• Journal of the Microelectronics and Packaging Society
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• v.9 no.4
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• pp.61-68
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• 2002

Thermal shock testing was used to evaluate reliability that appeared in the solder joints of electronic devices when they were subjected to thermal cycling. Recently, mobile devices have come smaller and multi-functional, with the increasing need for high-density packaging, BGA or CSP has become the main trend for surface mounting technology, and therefore mechanical stress life for solder joints in BGA/CSP type packages has required. Reliability of BGA/CSP solder joints was evaluated with electric resistivity change of daisy chain pattern and stress-strain curve measured using strain gage attached on the surface of PCB under mechanical impact loading. In this report, applications of PCB Universal Testing Machine we have developed and experimental datum of SONY estimating dynamic behavior of mechanical stress in BGA/CSP solder joints are introduced.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• v.y2005m4
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• pp.381-385
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• 2005

Recently, spacecraft technology trends can be expressed three words, i.e. 'faster, cheaper and smaller'. Among these systems, micro propulsion device is an essential component. Also micro nozzle is the most important part in the micro propulsion device. In case of cold-gas thruster, micro nozzle converts the stored energy in a pressurized gas into kinetic energy through expansion ratio. In this paper we report characteristics of micro nozzle with throat expansion ratio and ratio of specific heats. We measure thrusts using strain gauge based thrust measurement system. We can estimate the micro nozzle performance through experiments.

• Journal of the Korean Society of Propulsion Engineers
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• v.11 no.6
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• pp.42-49
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• 2007

In this study, we analyzed flow characteristics of micro-nozzles for basic research to develop micro propulsion system. Cold gas propulsion system was used, and micro-nozzles having nozzle throat diameters of 1.0, 0.5, 0.25 mm were fabricated with EDM method. Thrust was measured through the use of plate-spring and strain gage based thrust measurement system, and flow characteristics of micro-nozzles were analyzed under ambient condition and vacuum condition. We used argon and nitrogen gases as propellant, and compared experimental results with CFD analysis. From the result, we verified the flow losses of viscosity and back-pressure caused by minimization of nozzle.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1995.10a
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• pp.247-250
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• 1995

The development and empirical validation of a mathematical model for predicting the depth of deformed layer in a machined surface are presented. The main assumption for develioping this model is that there is a linear relationship between plastic strain and the depth to which it extends. The model relates the work required to shear the workpice material to the work needed to compress the workpiece material ahead of the cutting tool. The results show that the percent difference between the calculated and the measured depth of deformed layer ranges form 4 percent to 19 percent. An improvement of the model is suggested through application of actual distribution data of plastic strain.

• Journal of Sensor Science and Technology
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• v.12 no.5
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• pp.199-204
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• 2003

This paper describes on the fabrication and characteristics of a ceramic thin-film pressure sensor based on Ta-N strain-gauges for harsh environment applications. The Ta-N thin-film strain-gauges are sputter-deposited onto a micromachined Si diaphragms with buried cavity for overpressure protectors. The proposed device takes advantages of the good mechanical properties of single-crystalline Si as diaphragms fabricated by SDB and electrochemical etch-stop technology, and in order to extend the operating temperature range, it incorporates relatively the high resistance, stability and gauge factor of Ta-N thin-films. The fabricated pressure sensor presents a low temperature coefficient of resistance, high-sensitivity, low non-linearity and excellent temperature stability. The sensitivity is $1.097-1.21\;mV/V{\codt}kgf/cm^2$ in the temperature range of $25-200^{\circ}C$ and the maximum non-linearity is 0.43%FS.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.4
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• pp.578-583
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• 2017

This paper presents a 3D touch pad technology that uses force touch sensors as a next-generation method for mobile applications. 3D touch technology requires detecting the location and pressure of touches simultaneously, as well as multi-touch function. We used metal foil strain gauges for the touch recognition sensor and detected the weak touch signals using Wheatstone bridge circuit at each strain gauge sensor. We also developed a touch recognition system that amplifies touch signals, converts them to digital data through a microprocessor, and displays the data on a screen. In software, we designed a touch recognition algorithm with C code, which is capable of recognizing two-point touch and differentiating touch pressures. We carried out a successful experiment to display two touch signals on a screen with different forces and locations.