• Transactions of the Korean Society of Mechanical Engineers
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• v.16 no.5
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• pp.910-923
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• 1992

Experimental verification of numerical results is conducted by measuring the dynamic strains of mid-points of the coupler and the lever for the 4-bar linkage mechanism with rigid bearing and flexible bearing, respectively. For the axial strain of lever mid-point, the numerical results including geometric stiffness almost agree with the experimental ones, however, the numerical results excluding geometric stiffness almost agree with the experimental ones for the axial strain of coupler mid-point. It is supposed that these phenomena should be caused by the fact that the motion of the coupler is more complicated than of the lever. The signals of dynamic strains of coupler and lever mid-points, measured by strain gages, are transformed into frequency domain by fast fourier transformer. From this experiment, the lst resonance frequencies of the coupler and the lever are obtained. It is made clear that the former almost agrees with the fundamental and the latter the 2nd mode natural frequency of the mechanism system calculated by numerical analysis.

• Journal of the Korean Society for Precision Engineering
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• v.11 no.6
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• pp.50-56
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• 1994

A DC generator control system was designed to control the torque of a rotating shaft precisely. The control system is composed of a strain gage type torque cell, a torque cell amplifier, a computer, a D/A converter, a error detector, a DC voltage amplifier and a resistor. The response test under unit step input and the dynamic stability test for the designed control system were carried out. It was confirmed that the settling time from the response test is about 4 s and the error from the dynamic stability test is less than 0.06% of rated output of torque cell. The designed control system may be used to control a DC generator which may be used to apply torque to a rotating shaft.

• Transactions of the Korean Society of Mechanical Engineers
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• v.19 no.3
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• pp.688-696
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• 1995

Cemented carbides, best known for their superior mechanical properties such as high strength, high hardness and high wear resistance, have a wide range of industrial applications including metal working tools, mining tools, and wear resistance components. The cobalt has been used as a binder in the WC-based hard composites due to its outstanding wetting and adhesion characteristics even though its expensiveness. Therefore many studies attempted to find a better substitute for cobalt as binder to decrease production costs. This investigation is a pre-step to study dynamic fracture characteristic evaluation of a WC-Co hardmetal were evaluated by using the instrumented Charpy impact testing procedures. It was found that the dynamic characteristics of used strain amplifier were very important experimental factors to extract valid dynamic fracturing data in WC-Co specimens. It was suggested by showing some experimental examples that when we wished to evaluate dynamic fracture toughness for cemented carbide composites by using the instrumented Charpy impact testing procedure, a careful attention must be given to obtain valid results.

• Journal of Biosystems Engineering
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• v.11 no.1
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• pp.24-30
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• 1986

In order to collect the engine performance data accurately, rapidly and reliabily, the microcomputer-based engine performance test system was developed and tested. The system measures engine shaft torque and speed, fuel consumption, exhaust gas temperature, engine shaft power and fuel consumption ratio. The system consisted of 32 channels 8 bit A/D converter, time clock, dynamic strain amplifier and signal conditioning circuits to amplify and filter the electrical signal from transducers. Most of transducers were devised for low cost, easy setting and self-manufacturing. The system has been installed on a small kerosene engine (DAEDONG NA50B).

• The Journal of Korean Academy of Prosthodontics
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• v.45 no.6
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• pp.717-723
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• 2007

Statement of problem. Unreasonable distal cantilevered implant-supported prosthesis can mask functional problems of reconstruction temporarily, but it can cause serious strain and stress around its supported implant and surrounding alveolar bone. Purpose. The purpose of this study was to evaluate strain of implants supporting distal cantilevered fixed prosthesis with two different cantilevered length under distal cantilevered static load. Material and methods. A partially edentulous mandibular test model was fabricated with auto-polymerizing resin (POLYUROCK; Metalor technologies, Stuttgart, Swiss) and artificial denture teeth (Endura; Shofu inc., Kyoto, Japan). Two implants-supported 5-unit screw-retained cantilevered fixed prosthesis was made using standard methods with Type III gold alloy (Harmony C&B55; Ivoclar-vivadent, Liechtenstein, Germany) for superstructure and reinforced hard resin (Tescera; Ivoclar-vivadent, Liechtenstein, Germany) for occlusal material. Two strain gauges (KFG-1-120-C1-11L1M2R; KYOWA electronic instruments, Tokyo, Japan) were then attached to the mesial and the distal surface of each standard abutment with adhesive (M-bond 200; Tokuyama, Tokyo, Japan). Total four strain gauges were attached to test model and connected to dynamic signal conditioning strain amplifier (CTA1000; Curiotech inc., Paju, Korea). The stepped $20{\sim}100$ N in 25 N increments, cantilevered static load 8mm apart (Group I) or 16mm apart (Group II), were applied using digital push-pull gauge (Push-Pull Scale & Digital Force Gauge, Axis inc., Seoul, Korea). Each step was performed ten times and every strain signal was monitored and recorded. Results. In case of Group I, the strain values were surveyed by $80.7{\sim}353.8{\mu}m$ in Ch1, $7.5{\sim}47.9{\mu}m/m$ in Ch2, $45.7{\sim}278.6{\mu}m/m$ in Ch3 and $-212.2{\sim}718.7{\mu}m/m$ in Ch4 depending on increasing cantilevered static load. On the other hand, the strain values of Group II were surveyed by $149.9{\sim}612.8{\mu}m/m$ in Ch1, $26.0{\sim}168.5{\mu}m/m$ in Ch2, $114.3{\sim}632.3{\mu}m/m$ in Ch3, and $-323.2{\sim}-894.7{\mu}m/m$ in Ch4. Conclusion. A comparative statistical analysis using paired sample t-test about Group I Vs Group II under distal cantilevered load shows that there are statistical significant differences for all 4 channels (P<0.05).

• The Journal of Korean Academy of Prosthodontics
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• v.39 no.6
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• pp.709-734
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• 2001

The aims of this experiment were to investigate the strain and temperature changes simultaneously within autopolymerzing acrylic resin specimens. A computerized data acquisition system with an electrical resistance strain gauge and a thermocouple was used over time periods up to 180 minutes. The overall strain kinetics, the effects of stress relaxation and additional heat supply during the polymerization were evaluated. Stone mold replicas with an inner butt-joint rectangular cavity ($40.0{\times}25.0mm$, 5.0mm in depth) were duplicated from a brass master mold. A strain gauge (AE-11-S50N-120-EC, CAS Inc., Korea) and a thermocouple were installed within the cavity, which had been connected to a personal computer and a precision signal conditioning amplifier (DA1600 Dynamic Strain Amplifier, CAS Inc., Korea) so that real-time recordings of both polymerization-induced strain and temperature changes were performed. After each of fresh resin mixture was poured into the mold replica, data recording was done up to 180 minutes with three-second interval. Each of two poly(methyl methacrylate) products (Duralay, Vertex) and a vinyl ethyl methacrylate product (Snap) was examined repeatedly ten times. Additionally, removal procedures were done after 15, 30 and 60 minutes from the start of mixing to evaluate the effect of stress relaxation after deflasking. Six specimens for each of nine conditions were examined. After removal from the mold, the specimen continued bench-curing up to 180 minutes. Using a waterbath (Hanau Junior Curing Unit, Model No.76-0, Teledyne Hanau, New York, U.S.A.) with its temperature control maintained at $50^{\circ}C$, heat-soaking procedures with two different durations (15 and 45 minutes) were done to evaluate the effect of additional heat supply on the strain and temperature changes within the specimen during the polymerization. Five specimens for each of six conditions were examined. Within the parameters of this study the following results were drawn: 1. The mean shrinkage strains reached $-3095{\mu}{\epsilon},\;-1796{\mu}{\epsilon}$ and $-2959{\mu}{\epsilon}$ for Duralay, Snap and Vertex, respectively. The mean maximum temperature rise reached $56.7^{\circ}C,\;41.3^{\circ}C$ and $56.1^{\circ}C$ for Duralay, Snap, and Vertex, respectively. A vinyl ethyl methacrylate product (Snap) showed significantly less polymerization shrinkage strain (p<0.01) and significantly lower maximum temperature rise (p<0.01) than the other two poly(methyl methacrylate) products (Duralay, Vertex). 2. Mean maximum shrinkage rate for each resin was calculated to $-31.8{\mu}{\epsilon}/sec,\;-15.9{\mu}{\epsilon}/sec$ and $-31.8{\mu}{\epsilon}/sec$ for Duralay, Snap and Vertex, respectively. Snap showed significantly lower maximum shrinkage rate than Duralay and Vertex (p<0.01). 3. From the second experiment, some expansion was observed immediately after removal of specimen from the mold, and the amount of expansion increased as the removal time was delayed. For each removal time, Snap showed significantly less strain changes than the other two poly(methyl methacrylate) products (p<0.05). 4. During the external heat supply for the resins, higher maximum temperature rises were found. Meanwhile, the maximum shrinkage rates were not different from those of room temperature polymerizations. 5. From the third experiment, the external heat supply for the resins during polymerization could temporarily decrease or even reverse shrinkage strains of each material. But, shrinkage re-occurred in the linear nature after completion of heat supply. 6. Linear thermal expansion coefficients obtained from the end of heat supply continuing for an additional 5 minutes, showed that Snap exhibited significantly lower values than the other two poly(methyl methacrylate) products (p<0.01). Moreover, little difference was found between the mean linear thermal expansion coefficients obtained from two different heating durations (p>0.05).

• Korean Journal of Agricultural Science
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• v.8 no.1
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• pp.90-96
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• 1981

To design more efficient agricultural machinery, the accurately measuring system among many other factors is essential. A light-beam oscillographic recorder is generally used in measuring dynamic strain but it is not compatible with the extremely high speed measuring system such as 1,000 m/s, also is susceptable to damage due to vibration while using the system in field. The recorder used light sensitive paper for strip chart recording. The reading and analysis of data from the strip charts is very cumbersome, errorneous and time consuming. A microcomputer was interfaced with A/D converter, microcomputer program was developed for measuring, system calibration was done and the strain generated from a cantilever beam vibrator was measured. The results are summarized as follows. 1. Microcomputer program was developed to perform strain measuring of agricultural machine elements and could be controled freely the measuring intervals, no. of channels and no. of data. The maximum measuring speed was $62{\mu}s$. 2. Calibration the system was performed with triangle wave generated from a function generator and checked by an oscilloscope. The sampled data were processed using HP 3000 minicomputer of Chungnam National University computer center the graphical results were triangle same as input wave and so the system have been out of phase distorsion and amplitude distorsion. 3. The strain generated from a cantilever beam vibrator which has free vibration period of 0.019 second were measured by the system controlled to have l.0 ms of time interval and its computer output showing vibration curve which is well filted to theoretical value. 4. Using microcomputer on measuring the strain of agricultural machine elements could not only save analyzing time and recording papers but also get excellent adaptation to field experiment, especially in measurement requiring high speed and good precision.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.2 no.2
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• pp.3-8
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• 2009

The traction system has been mainly used for rehabilitation and correction of patients with spine or gait diseases in orthopedics or at home. Some problems could occur in human body when patients forced their training using the traction system. So it needs to measure a traction force and control the training time. However, most of products on market have no sensor measuring traction force. Thus we designed and made a sensor detecting traction force using strain gauge, amplifier for transition to output signal and experiment devices for performance test. We carried out experiment of a sensor detecting a traction force and measured electric responses of it with respect to traction loads. Maximum error was within about 1% for experiments in static condition and the average error was about 0.7% for experiments in dynamic condition. We concluded that it is possible to use the developed sensor for measurement of traction force since the maximum output variation of a sensor detecting a traction force was about 0.3% in $0^{\circ}C-60^{\circ}C$ temperature condition.