• Journal of the Korea Institute of Military Science and Technology
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• v.17 no.1
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• pp.135-141
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• 2014

In order to guide a flying object which uses a seeker(SKR) and an inertial navigation system(INS) properly, we should confirm that axes of both equipments are aligned in the scope expected. In this paper we have proposed a method to measure the misaligned angle between a SKR and an INS during the system integration procedure. And we expanded this method to measure misalignments between several SKRs and an INS in case of captive flight test.

• International Journal of Fluid Machinery and Systems
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• v.8 no.3
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• pp.132-141
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• 2015

This paper presents a CFD-based methodology for the prediction of guide vane torque in hydraulic turbine distributor for aligned and misaligned configurations. A misaligned or desynchronized configuration occurs when the opening angle of one guide vane differs from the opening angle of all other guide vanes, which may lead to a torque increase on neighbouring guide vanes. A fully automated numerical procedure is presented, that automates computations for a complete range of operation of a 2D or 3D distributor. Results are validated against laboratory measurements.

• Proceedings of the Korean Society For Composite Materials Conference
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• 2003.04a
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• pp.211-214
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• 2003

This paper presents the microscopic observation results from the picture frame test using five-harness satin weave fabric composite. Aligned and misaligned specimens are observed to verify the exact tow deformation pattern such as tow interval and change in tow amplitude. To observe the micro-deformation of the fabric structure, appropriate specimens from picture frame test are sectioned and observed under the microscope. From the observation results, it is found that a picture frame test with a misaligned fibre orientation angle shows large differences in deformation between tensile and compressive tow directions.

• Tribology and Lubricants
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• v.36 no.2
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• pp.82-87
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• 2020

In thrust bearings, the thrust collar and bearing surface need to be parallel to each other to ensure that all pads share the same load. In rotating machines, the shaft system cannot achieve perfect alignment. Misalignment of the thrust collar results in some pads supporting a higher load than others and excessive loads being placed on some pads. Consequently, high loads and high temperatures may occur in the bearing. Thus, in this study, we aim to analytically evaluate the performance of a misaligned non-equalizing direct lubricated tilting pad thrust bearing. We define the oil film thickness of the misaligned thrust bearing using the Byrant angle. Additionally, we calculate the pressure distribution and temperature distribution of the thrust bearing using the generalized Reynolds equation and energy equation. The design limit of the thrust bearing is defined by the load and temperature. Therefore, we evaluate the allowable misalignment angle as the limit of the maximum load and temperature. The analysis results demonstrate that an increase in the speed and load corresponds to a smaller allowable misalignment angle. However, as this is not the same for all thrust bearings, evaluating the allowable misalignment angle at each thrust bearing is essential.

• Tribology and Lubricants
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• v.33 no.4
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• pp.168-186
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• 2017

This paper presents a wear analysis procedure for calculating the wear of journal bearings during the start-up and coast-down cycles of a motoring stripped-down single cylinder engine operating with a tilted shaft. In order to decide whether the lubrication state of a journal bearing is in the mixed-elasto-hydrodynamic lubrication regime, we utilize lift-off speed and MOFT (most oil film thickness) under mixed-elasto-hydrodynamic lubrication regime at the corresponding aligned shaft. We formulate an equation for the modified film thickness in a misaligned journal bearing considering the additional wear volume described in Part I of this study. For this, we use the calculation results of the degree of misalignment and tilting angle obtained after finding the eccentricities of the two bearings supporting the crankshaft of a single cylinder engine. In this Part II, we calculate the wear of journal bearings using the fractional film defect coefficient, the asperity load sharing factor, and the modified specific wear rate for the application of mixed-elasto-hydrodynamic lubrication regime. We show that the accumulated wear volume after turning the ignition switch on and off once, increases to ${\sigma}=39{\mu}m$ and then decreases from ${\sigma}=39{\mu}m$ with increasing in surface roughness.

• Tribology and Lubricants
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• v.33 no.4
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• pp.153-167
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• 2017

The aim of this study is to find the change in trend in the eccentricities of two journal bearings supporting the crankshaft of a single cylinder engine and the degree of misalignment of the shaft. We analyze the change in oil film thickness considering the wear scar under mixed-elasto-hydrodynamic lubrication regime at potential wear regions. For this, we first calculate the central eccentricities of the two journal bearings by using the mobility method. Then we calculate the outer end eccentricity by using the geometry of the bearings. Further, the tilting angle and degree of misalignment of the shaft are calculated by using the eccentricities of the two bearings. We show that the eccentricity of bearing #1, on which higher load is applied, increases at the beginning of the start-up cycle and during the coast-down cycle. However, the eccentricity of bearing #2, on which lower load is applied, decreases at the beginning of the start-up cycle and increases during the coast-down cycle. From the results of the analysis of oil film thickness, we show that the mixed-elasto-hydrodynamic lubrication regime for a misaligned shaft is at the initial stages of the start-up cycle for both bearing #1 and #2 and at the final stage of the coast-down cycle for only bearing #1.

• Composites Research
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• v.18 no.2
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• pp.13-19
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• 2005

In this paper deformation of micro-mechanical parameters such as tow interval, tow thickness and change in tow amplitude are investigated by using dry fabrics (Five-harness satin weave) under shear deformation. To evaluate the observation results according to the generated in-plane forces in the material, bias extension, biaxial test results are compared with. It was found that a picture frame test with a misaligned fibre orientation angle shows large differences in deformation between tensile and compressive tow directions.

• KIEE International Transaction on Electrical Machinery and Energy Conversion Systems
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• v.3B no.1
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• pp.59-64
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• 2003

This paper presents a new rotor position estimation method for brushless DC motors. The estimation error of the rotor position clearly provokes the phase shift angle misaligned between the phase current and the back-EMF waveforms, which causes torque ripple in brushless DC motor drives. Such an estimation error can be reduced with the help of the proposed neutral-voltage-based estimation method, which is structured as a closed loop observer. A neutral voltage appearing during the normal mode of the inverter operation is found to be an observable and control table measure, which can be used for estimating an exact rotor position. This neutral voltage is obtained from the DC-link current, the switching logic, and the motor speed values. The proposed algorithm, which can be easily implemented by using a single DC-link current and the motor terminal voltage sensors, is verified by simulation and experiment results.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.39 no.3
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• pp.245-251
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• 2015

In an electrical reliability test of a printed circuit board (PCB), the impact of the micro probing pins on the PCB needs to be checked to ascertain the quality of the circuit. In this study, the impact of the dynamic movement of the probing pin on the pad was observed. As a misaligned pin can exert horizontal force on the pad of the PCB, this study focused on the behavior of a misaligned probing pin. The parameters of observation were the circular and flat edges of the probing pin. The effects of the speed of movement, diameter, and the length of projection of the probing pin were also investigated. The results demonstrated that slippage angle is strongly affected by the shape of the edge of the probing pin, and that projection length is an important factor affecting pin slippage. In contrast, the speed of movement of the probing pin was able to double the slippage angle.

• Tribology and Lubricants
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• v.36 no.1
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• pp.27-33
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• 2020

Self-equalizing tilting pad thrust bearings are usually employed in turbomachines to achieve high stability and reliability. A tilting pad bearing can incorporate self-equalizing links to handle the misalignment between the bearing and the thrust collar. In this popular design method, the pads sit on the upper-level plates and the lower-level plates stay on the retainer base. With misalignment, the pads that are heavily loaded are pushed down. Consequently, the link pushes up the pads on the opposite side, keeping the bearing surface parallel to the thrust collar surface. The self-equalizing link is used to handle the misalignment from the thermal and mechanical effects. In this study, the experimental investigation deals with the performance of self-equalizing tilting pad thrust bearings. The test rig for evaluating the performance of bearing is developed which can control the misalignment angle. Simultaneous measurements are taken for the force acting on each pad. Pad metal temperature and oil film thickness are functions of the shaft speed, bearing load, misalignment angle, and design of leveling plates. The effect of misalignment on bearing performance is discussed. The results demonstrate that the load on each pad depends on the test conditions(especially misalignment angle), and the load influences the performance of bearings.