• Design & Manufacturing
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• v.17 no.4
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• pp.8-13
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• 2023

In this study, it was studied whether a new measurement factor "frictional vibration" that occurs due to the material flow of the die and sheet metal in the flange area during deep drawing process, could be measured using an vibration sensor. The blank holder force acting on the flange area during drawing processing acts as a friction force in the opposite direction into which the sheet material flows and causes friction vibration. As the blank holder force increases, the friction force increases, and as the blank holder force decreases, the friction force also decreases. Because of this, friction vibration also increases and decreases in proportion to the size of the blank holder force. According to this theory, whether frictional vibration occurs was measured using a flange simulator and a vibration sensor. The initial pressure was created using a torque wrench, and it was confirmed that the amplitude increased by about 4 times when torque 6 Nm was increased. When the forming velocity was rapidly changed to 300 mm/min, the amplitude increased approximately 4 times. It was confirmed that the amplitude of frictional vibration according to the measurement location was greater the further away from the specimen. It was verified that a new measurement factor "friction vibration" in the flange area can be measured and used for online monitoring.

• Journal of the korean academy of Pediatric Dentistry
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• v.31 no.1
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• pp.66-78
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• 2004

The objective of this study was to apply the vibration technique to reduce the viscosity of bonding adhesives and thereby compare the bond strength and resin penetration in enamel and dentin achieved with those gained using the conventional technique and vibration technique. For enamel specimens, thirty teeth were sectioned mesio-distally. Sectioned two parts were assigned to same adhesive system but different treatment(vibration vs. non-vibration). Each specimen was embedded in 1-inch inner diameter PVC pipe with a acrylic resin. The buccal and lingual surfaces were placed so that the tooth and the embedding medium were at the same level. The samples were subsequently polished silicon carbide abrasive papers. Each adhesive system was applied according to its manufacture's instruction. Vibration groups were additionally vibrated for 15 seconds before curing. For dentin specimen, except removing the coronal part and placing occlusal surface at the mold level, the remaining procedures were same as enamel specimen. Resin composite(Z250. 3M. U.S.A.) was condensed on to the prepared surface in two increments using a mold kit(Ultradent Inc., U.S.A.). Each increments was light cured for 40 seconds. After 24 hours in tap water at room temperature, the specimens were thermocycled for 1000cycles. Shear bond strengths were measured with a universal testing machine(Instron 4465, England). To investigate infiltration patterns of adhesive materials, the surface of specimens was examined with scanning electron microscope. The results were as follows: 1. In enamel the mean values of shear bond strengths in vibration groups(group 2, 4, 6) were greater than those of non-vibration group(group 1, 3, 5). The differences were statistically significant except AQ bond group. 2. In dentin, the mean values of shear bond strengths in vibration groups(group 2, 4, 6) were greater than those of non-vibration groups(group 1, 3, 5). But the differences were not statistically significant except One-Up Bond F group. 3. The vibration group showed more mineral loss in enamel and longer resin tag and greater number of lateral branches in dentin under SEM examination.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.20 no.5
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• pp.523-527
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• 2011

Polycarbonate (PC) polymer is an engineering plastic which has large tensile strength and impact resistance and is wildly used as functional parts like micro mold. Direct machining of PC materials produces lots of burrs and rough surface due to large ductility and weak heat resistance and hence it is very difficult to machine PC materials using cutting tool to make micro-parts. In this study, elliptical vibration cutting (EVC) or 2-dimensional vibration cutting was performed to minimize the size of micro V-grooves on PC material. From the experimental results, it was observed that as the cutting depth and pattern size become smaller, the better machining quality was obtained, which is attributed to the positive effect of EVC that is dependent on the ratio of vibration amplitude to cutting depth. As the height of V-groove becomes less than $1.8{\mu}m$, however, the machining quality becomes lower as the pattern size decreases.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 1997.10a
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• pp.70-73
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• 1997

This paper describes the technique for detecting failure symptom of mold transformer. This study uses the vibration signal analysis method and FEM as the technique. A loading back method is constructed for experiment, accelation sensors are adhered for measurement of vibration signal. Vibration signal measured by this method is analyzed into variation trend of measurement variables by control of control variables. Magnetic field distribution of molded winding is also acquired by FEM considering the design specfication and the characteristics of insulation material, in conclusion, he relation of results between vibration signal and FEM is studied by these methods.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.33 no.11
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• pp.1209-1216
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• 2009

Nano-micro hierarchical structures that nanoprotrusions were formed on the network-type microstructures were fabricated using an ultrasonic vibration forming technology. A commercial ultrasonic welding system was used to apply ultrasonic vibration energy. To evaluate the formability of ultrasonic vibration forming, nickel nano-micro hierarchical mold was fabricated and polyethylene (PE) was used as the replication material. The optimal molding time was 3.5 sec for PE nano-micro hierarchical structures. The molding process was conducted at atmospheric pressure.

• Computers and Concrete
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• v.20 no.6
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• pp.655-661
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• 2017

Fiber reinforced concretes exhibit higher tensile strength depending on the percent and type of the fiber used. These concretes are used to reduce cracks and improve concrete behavior. The use of these fibers increases the production costs and reduces the compressive strength to a certain extent. Therefore, the use of fiber reinforced concrete in regions where higher tensile strength is required can cut costs and improve the overall structural strength. The behavior of fiber reinforced concrete and normal concrete adjacent to each other was investigated in the present study. The concrete used was self-compacting and did not require vibration. The samples had 0, 1, 2 and 4 wt% polypropylene fibers. 15 cm sample cubes were subjected to uniaxial loads to investigate their compressive strength. Fiber Self-Compacting Concrete was poured in the mold up to 0, 30, 50, 70 and 100 percent of the mold height, and then Self-Compacting Concrete without fiber was added to the empty section of that mold. In order to investigate concrete behavior under bending moment, concrete beam samples with similar conditions were prepared and subjected to the three-point bending flexural test. The results revealed that normal Self-Compacting Concrete and Fiber Self-Compacting Concrete may be used in adjacent to each other in structures and structural members. Moreover, no separation was observed at the interface of Fiber Self-Compacting Concrete and Self-Compacting Concrete, either in the cubic samples under compression or in the concrete beams under bending moment.

• Design & Manufacturing
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• v.16 no.4
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• pp.1-6
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• 2022

Fine blanking is a press processing technology that can process most of the product thickness into a smooth surface with a single stroke. In this fine blanking process, shear is an essential step. The punches and dies used in the shear are subjected to impacts of tens to hundreds of gravitational accelerations, depending on the type and thickness of the material. Therefore, among the components of the fine blanking mold (dies), punches and dies are the parts with the shortest lifespan. In the actual production site, various types of tool damage occur such as wear of the tool as well as sudden punch breakage. In this study, machine learning algorithms were used to predict these problems in advance. The dataset used in this paper consisted of the signal of the vibration sensor installed in the tool and the measured burr size (tool wear). Various features were extracted so that artificial intelligence can learn effectively from signals. It was trained with 5 features with excellent distinguishing performance, and the SVM algorithm performance was the best among 33 learning models. As a result of the research, the vibration signal at the time of imminent tool replacement was matched with an accuracy of more than 85%. It is expected that the results of this research will solve problems such as tool damage due to accidental punch breakage at the production site, and increase in maintenance costs due to prediction errors in punch exchange cycles due to wear.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 2004.04a
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• pp.410-415
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• 2004

Heavy-weight head slides may cause excessive inertia impact ＆ moment on the machine tool structure when they move or stop abruptly during operation. Consequently these inertia impact and unbalanced moment bring transient vibrations and rough sliding motions on the machine structure. Machine tool engineers have tried many kind of feed-slide designs in order to solve this problem; for example, the design optimization of the moving structure for minimum weight and maximum stiffness, box-in-box type slide design, and so on. In this article, force and moment equilibrium equations regarding to the inertia force ＆ moment were derived for each one of a mold M/C's head slides. Furthermore, five different design configurations of head slide assembly were reviewed for its design improvement regarding to force ＆ moment calculations and finite element structural analysis results.

• Proceedings of the Korean Society For Composite Materials Conference
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• 1999.11a
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• pp.139-142
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• 1999

Screw rotors are core parts of screw type air compressors, compressors in refrigerating machines and super chargers of automobiles etc. They are composed of a female and a male rotors which have complex section profiles and helically swept geometry. Screw type compressors have advantages of low noise, high efficiency, less needs in maintenance etc. Usually, machining process of screw rotors requires long machining time using CNC machine designed only for screw rotors, which increase the cost of production. In this work, the screw rotors for air-compressors were manufactured with fiber reinforced epoxy composite materials by resin transfer molding process. The mold for the RTM process was made of aluminum and silicon rubber and was designed for release of helical shape products. Composite screw rotors, manufactured by RTM process, have advantages of lightweight, less cost of production, good characteristics of vibration etc.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.11a
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• pp.387-390
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• 2000

The life of transformer is significantly dependent on the thermal behavior in windings. To analyse winding temperature rise, many transformer designer have calculated temperature distribution and hot spot point by finite element method(FEM). Recently, numerical analyses of transformer are studied for optimum design, that is electric field analysis, magnetic field, potential vibration, thermal distribution and thermal stress. Therefore design time and design cost are decreased by numerical analysis. In this paper, the temperature distribution and thermal stress analysis of 50kVA pole cast resin transformer for power distribution are investigated by FEM program. The temperature change according to load rates of transformer also have been investigated. We have carried out temperature rise test and test results are compared with simulation data.