To accurately assess mechanical properties of micro- and nano-sized specimens, a reliable material testing system is indispensable. However, due to small sizes of these test specimens, in-situ measurement of their mechanical behavior necessitates installing the tester within high-magnification microscopes such as SEM. Traditionally, researchers have used wired methods by placing the tester inside the SEM chamber and connecting it to an external controller via electrical feedthrough. Unfortunately, this approach is cumbersome. In addition, it limits its compatibility with other SEMs. In this study, we developed a compact controller capable of driving 3-axis piezoelectric actuators with nanometer-level displacement control resolution via Bluetooth communication. This innovative setup enables wireless control and data acquisition from outside the closed confines of an SEM chamber. To validate the versatility of our tester, we conducted both a nanoindentation test on a fused silica specimen using a Berkovich indenter in a wired configuration and a copper micropillar compression test wirelessly using a flat punch indenter within an SEM. By installing this tester in various measurement systems, researchers could observe deformation patterns in real time, making it a valuable tool for investigating deformation mechanisms of diverse micro- and nano-sized specimens.
In the existing machine tool field, the focus was on the displacement of the feed system from the viewpoint of the motion of the machine tool. The displacement of the tool or spindle of a machine tool is useful for developing various functions. In this study, using the acceleration data of the spindle, we proposed an algorithm that tracked the displacement of the spindle with respect to the pseudo-step waveform motion. In order to solve the bandwidth problem of the pseudo-step waveform, the displacement data measured by the motor encoder of the feed system was used. In addition, in order to solve the drift problem due to double integration, a new drift removal filter was proposed and a displacement estimation algorithm was implemented. In order to examine the performance and possibility of the proposed spindle displacement estimation algorithm, it was applied to a gantry-type engraver and its excellent performance was confirmed compared to other algorithms.
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A Review of Intelligent Machining Process in CNC Machine Tool Systems Joo Sung Yoon, Il-ha Park, Dong Yoon Lee International Journal of Precision Engineering and Manufacturing.2025; 26(9): 2243. CrossRef
Passenger ride comfort is an integral component of any road vehicle. Ride comport is impacted by vibration resulting from road roughness of low frequency, and also engine vibration of high frequency. The engine mount is an essential component, which acts as a vibration isolator from unwanted vibration. However, vibration isolation requires conflicting design criterion, such as high damping in low frequency range, and low damping in high frequency range. The purpose of this study was to develop a new optimal damping design method for engine mounts based on minimizing H∞-norm. The damping minimizes H∞-norm of displacement and force transmissibilities in the wide-frequency vehicle operating range. The proposed optimal damping control was applied to a Magnetorheological (MR) engine mount, to investigate the vibration isolation performance. The feasibility of the proposed method is verified, with some numerical simulation examples.
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Influence of Magnetic-Viscous Friction on the Properties of a Magnetorheological Hydraulic Mount A. V. Vanyagin, B. A. Gordeev, A. I. Ermolaev, S. N. Okhulkov, A. S. Plekhov Russian Engineering Research.2024; 44(10): 1425. CrossRef
Magnetic bearings use electromagnetic force to support the rotating shaft without any mechanical contact and actively control shaft vibration; hence, there is no mechanical friction and wear due to contact during the operation, and it has a semi-permanent lifespan. Because magnetic bearings are unstable by themselves, a gap sensor is necessary to stably control the position of objects. However, there is a limit to the improvement in control performance because the sensor is installed on one side of the bearing and is not aligned with the electromagnet. This paper presents a newly developed collocated eddy-current PCB displacement sensor for magnetic bearings. The PCB sensor is designed and built to install between the poles of a magnetic bearing and to minimize the electromagnetic interference. A sensor calibration test is performed to evaluate the sensitivity and noise of the collocated PCB sensor. In addition, the control performance of the collocated PCB sensor is evaluated by measuring the closed-loop sensitivity function of a 1 DOF magnetic suspension test rig. The collocated PCB sensor has noise within ±1 μm and excellent vibration suppression performance.
The large gas turbine rotor used for power generation has a structural characteristic comprising a shaft, disk, and blade assembled to the disk. Because the start/stop is repeated, the tightening force may be reduced in the process of repeating the tightening force between the tie rod and the disk. When the tightening force falls below the threshold, changing the critical speed, increasing the vibration, or in extreme cases, the rotor may loosen and cause a major accident. Also, it is imperative to continuously maintain the proper tightening force because the thread of the tie rod is damaged when the tightening force exceeds the yield stress condition of the tie rod. In this paper, the gas turbine rotor system is modeled and simplified to identify the control variable of the tightening force of the tie rod bolts of the rotor. For verification, a simplified model of the gas turbine rotor was designed, manufactured, and verification tests were conducted to confirm the adequacy of the calculation method. As a result, the tightening force decreased as the stiffness of the pressing disk decreased, so the stiffness of the pressing disk should have a stiffness range similar to that of the tie rod.
Displacement ductility and rotational ductility are used, to verify the performance of blast doors subjected to explosive loads. The values of these performance items are calculated by measuring the maximum elastic displacement in the laboratory, and the maximum displacement during the explosion test. To attain the maximum elastic displacement, the finite element analysis and the load distribution method are applied. In applying the load distribution method, the behavior of a blast door along a width direction is converted to a cantilever beam and along a height direction to a simply supported beam. The results by the load distribution method are verified by a finite element analysis and compared with those by a plate theory.
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Design of Frame Type Blast Door Reflecting Explosion Proof Test Kwan Bo Shim, Taek Sung Lee Journal of Korean Society of Steel Construction.2020; 32(2): 67. CrossRef
Optimized Design of Grid Type Explosion-Proof Door Using Load Distribution Method Kwan Bo Shim, Byeong Jin Kim, Hyunjoo Koo Journal of Korean Society of Steel Construction.2020; 32(6): 397. CrossRef
Design of Concrete Filled Steel Plate Door by Design of Experiment in Load Distribution Method Kwan Bo Shim, Byeong Jin Kim, Taek Sung Lee Journal of Korean Society of Steel Construction.2020; 32(6): 351. CrossRef
This study focuses on these issues and includes the static fracture experiments with two forms of specimens; aluminum foam DCB and TDCB bonded with the type of mode III, a simulation static analysis to verify this experiment, and analysis of fracture behavior of adhesive interface of structures attached with aluminum foam by shape and thickness. The thickness of DCB and TDCB specimens designed in this study are set as variable t, and each thickness is t = 35 mm, 45 mm, 55 mm. According to forced displacements, the maximum reaction forces of DCB specimens due to thickness were approximately 0.35 kN, 0.45 kN, 0.54 kN, and the maximum reaction force of TDCB were approximately 0.4 kN, 0.52 kN, and 0.63 kN respectively. We expect the data according to variables to be easily investigated without a separate testing process, and effective analysis of the mechanical characteristics of aluminum foam DCB and TDCB.
Displacement estimation based on inertial sensor signals is usually performed in aid of global positioning systems or barometers. However, due to low accuracy estimation capabilities of such aiding sensors, inertial sensor-based displacement estimation is difficult to achieve high accuracy. This paper will show that it is possible to determine the vertical displacement of a link connected by a joint with higher accuracy while only using the inertial sensor. The proposed method utilizes a predetermined position vector from the joint center to the sensor and link orientation. By combining the joint constraint, accuracy of the orientation estimation is ensured even in highly dynamic conditions, and thus, the vertical displacement estimation with high accuracy can be achieved. Experimental results show that the proposed method outperformed the method by fusing inertial sensor and barometer signals as well as the method using inertial sensor signals only without constraint combination.
This study investigated the role of multi-layer lever type flexure hinges for high magnification of piezoelectric actuators and their optimal design. In order to obtain a displacement higher than 700 μm with a common PZT actuator of displacement less than 15 μm, the magnification ratio of a flexure hinge must be at least 50 or higher. Under a limited compact space, a multi-layer lever structure represents a useful alternative. Restricting the important design parameters to the number of layers and rotational stiffness of notch, the maximum required input displacement/force and the maximum output displacement were analyzed according to the number of layers. The two-layer structure was selected as the best option for large magnification ratio because the required input displacement was drastically reduced. FEM analysis revealed that the lever thickness should be larger than 12 mm to exhibit a rigid body behavior. The output displacement was 664 μm, which was less than 704 μm expected in the design stage. It might be attributed to elastic deformation of the notches of 1st and 2nd layers, which was not considered in the design stage.
Rotary tables are often used to fix and support work-pieces in machine tools. Because the deformation of the rotary table is known to significantly affect the precision in the work of the machine tool, it is very important to accurately predict the static displacements of the rotary table subjected to internal and external loads. This paper deals with modeling and experimental verification of the static displacements of a large-size rotary table supported by a thrust cylindrical roller bearing (T-CRB) and a double row cylindrical roller bearing (D-CRB). To this end, a rotary table model was developed along with the quasi-static models for T-CRB and D-CRB. The equilibrium equation of the rotary table was derived, and solved one by one in the looping manner, to overcome its statically indeterminate characteristics. The proposed modeling method was verified by means of comparing to the experimental results. Finally, an extensive simulation was carried out to investigate the deflection of the rotary table subjected to cutting forces.
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Absolute Inductive Angular Displacement Sensor for Position Detection of YRT Turntable Bearing Yangyang Wang, Yi Qin, Xihou Chen, Qifu Tang, Tianheng Zhang, Liang Wu IEEE Transactions on Industrial Electronics.2022; 69(10): 10644. CrossRef
Study on the Guide Rail Deformation in Linear Roller Bearings Subjected to External Loading Jun-Ho Heo, Sun-Woong Kwon, Seong-Wook Hong Journal of the Korean Society for Precision Engineering.2019; 36(1): 79. CrossRef
In mobile phone cameras, usually a voice coil motor (VCM) is used as a micro-positioning device for the image autofocus (AF) because of its low cost, simplicity, and reliability. Measuring the actual displacement of the VCM is important when we assemble the camera and test the AF performance for distant objects. In this paper, we propose using a confocal displacement sensor for calibrating the VCM displacement, where the axial chromatic aberration of a confocal objective lens is used to measure the target position. The tolerance angle for the dynamic tilt of a VCM increased up to ±15o because of the large numerical aperture of the confocal objective lens, which increased the stability of the repeatable in-line inspection. We compared the measurement robustness of the confocal displacement sensor with that of the laser displacement sensor in a mass production line to verify its performance superiority.
Recently, Laser Direct Imaging (LDI) has been used to replace lithography in Flexible Printed Circuit Board (FPCB) manufacturing. However, repeated motion of a linear motor caused residual vibration in the granite on which the workpiece was placed when the motor either accelerated or decelerated. Because the residual vibration made positioning less accurate, there were more defective products and worse productivity. This paper proposes a way to reduce vibration in the granite during the precision stage. First, the frequency domain of the vibrations of a pneumatic vibration isolator is identified. Second, we present the design of the mechanism using a voice coil actuator and a capacitive displacement sensor. Third, we apply a feedback control algorithm based on PID to cancel displacement. Consequently, we are able to propose an optimal way to reduce vibration for the laser direct imaging equipment. The amount of vibration reduction is evaluated in terms of amplitude and settling time.
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Reaction Force Compensator for High‐Speed Precision Stage of Laser Direct Imaging Process Chang-hoon Seo, Yong ho Jeon, Hyung-ku Lee, Hyo-young Kim, Moon G. Lee, Francesco Franco Shock and Vibration.2018;[Epub] CrossRef
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