Chemical Mechanical Planarization (CMP) is an essential process for device integration and planarization in a semiconductor manufacturing process. The most critical function in the CMP process, is to predict and cover the geometrical characteristics of various sizes and densities, of patterned wafers for local and global planarization. To achieve the wafer-level and die-level planarization, it is necessary to understand the contact mechanism between the CMP pads and the macro-scale patterns. In the macro-scale pattern, pad deformation is divided into two layers: an asperity layer and a bulk pad layer. Through bulk pad deformation, asperity contact distribution within the pattern is predicted. In this paper, the distribution of asperity contact according to the pattern geometrical characteristics was analyzed, through large-area real contact area (RCA) measurement. Bulk pad deformation was predicted by analyzing RCA distribution according to pattern geometry such as pattern size and density, pattern shape and step height according to the polishing time, and applied pressure. Additionally, through the distribution of the contact area and the number of contact points, the rounding phenomenon and planarization characteristics in the pattern CMP were predicted.
In the framework of the 4th industrial revolution, modern machine building rapidly converges with IOT technology. This requires a very high level of precision machining of parts and assemblies, such as electronics, vehicle and components, agricultural and construction machines, optical instruments, and machine tools. However, high precision machinery is considerably expensive, and so a general need for low-cost equipment exists. While many researchers study this, they focus mainly on cutting tools. This study, for its part, focused on compensating errors and enhancing machinery precision, by adding a servo controller to the processing unit. As a result, we designed a fine dual servo system, ensuring 10 nm positioning accuracy and 40 nm of surface roughness.
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
The collaboration of robots and humans sharing workspace, can increase productivity and reduce production costs. However, occupational accidents resulting in injuries can increase, by removing the physical safety around the robot, and allowing the human to enter the workspace of the robot. In preventing occupational accidents, studies on recognizing humans, by installing various sensors around the robot and responding to humans, have been proposed. Using the LiDAR (Light Detection and Ranging) sensor, a wider range can be measured simultaneously, which has advantages in that the LiDAR sensor is less impacted by the brightness of light, and so on. This paper proposes a simple and fast method to recognize humans, and estimate the path of humans using a single stationary 360° LiDAR sensor. The moving object is extracted from background using the occupied grid map method, from the data measured by the sensor. From the extracted data, a human recognition model is created using CNN machine learning method, and the hyper-parameters of the model are set, using a grid search method to increase accuracy. The path of recognized human is estimated and tracked by the extended Kalman filter.
The fundamental flow models of metallic materials at room temperature, including the Ludwik, Hollomon, Swift and Voce models, were evaluated in terms of tensile test with an emphasis on the necking phenomena and post-necking behavior, to emphasize their limitation in satisfying tensile strength and Considère condition as well as the pre-necking and post-necking strain hardening. To resolve this limitation and enhance the applicability of the new proposed flow model to typical strain hardening materials, the Ludwik-Swift blended flow model is proposed after investigation into three blended flow models among the Ludwik, Voce and Swift models. Results revealed that there is no interpolation-based blended flow model of the fundamental flow models for the example flow curve exhibiting typical strain hardening but that the extrapolation-based combination of them can provide an engineering solution when the Ludwik and Swift models are blended. It was revealed that the reason for their good matching lies in the distinct difference in the strain hardening exponent, between the Ludwik and Swift models in the case of metallic materials with typical strain hardening.
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Novel finite element model of analyzing wall thickness during tube drawing considering raw tube’s thickness non-uniformity and die misalignment N. A. Razali, J. B. Byun, M. S. Joun International Journal of Material Forming.2024;[Epub] CrossRef
Movable weir is a major system used to manage water level in a river to secure drinking water, agricultural water, and industrial water. It is critical to safely construct and operate movable weir, in any environmental circumstances. In this study, we performed an unsteady flow analysis, on the movable weir with overflow water depth. The continuity equation, with constant density and incompressible Navier-Stokes equation, were used for the flow analysis. The CFD results were applied for structural analysis, to evaluate the safety of movable weir. According to the analysis results, the movable weir has secured sufficient safety.
The pipe inspection robot using the MFL non-destructive inspection equipment, has high inspection efficiency in the pipe with high magnetic permeability. However, this equipment generates attractive force between the pipe and the permanent magnet, requiring a high driving force for the robot, and sometimes causes the robot to be incapable of driving. In this study, the development of a spiral running type magnetic leakage detection pipe inspection robot system is described. Multi-body dynamics analysis was performed on the designed robot, to confirm the robot"s driving performance. After that, the performance of the robot was verified, by testing the manufactured robot in a standardized test bed.
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The purpose of this study was to design capacitors and a coil, which are components of an electric circuit, for improved performance of multi-stage electromagnetic coil guns. The electromagnetic force generated in the solenoid coil is determined by the magnitude of the current, supplied from the capacitor to the solenoid coil. Since the current flowing in the solenoid coil is not constant, the variability of electromagnetic force becomes larger. Design variables such as the capacitor capacity, coil winding, and firing distance are complicatedly related and determine the coil gun firing rate together. This study sets the number of turns of the solenoid coil, capacitor capacity, and firing distance as design variables for a five-stage coil gun. The electric circuit configuration of the coil gun with the highest velocity in each firing stage, was derived through the design of experiments. The coil gun’s finite element analysis model was constructed using ANSYS Maxwell, an electromagnetic analysis program, and implemented through a transient simulation to calculate the projectile’s velocity. Additionally, a prototype was manufactured based on the derived results to conduct launch experiments, and the experimental and simulation results were compared.
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Enhancing the defense application with ANSYS model of thermoelectric generation for coil gun P. Sreekala, A. Ramkumar, K. Rajesh Sustainable Energy Technologies and Assessments.2022; 54: 102806. CrossRef
The bone scaffold is artificial mechanical support, that is implanted on collapsed bone microstructure. The clinical field has become interested in that, because it is free of immunological rejection. However, few studies have analyzed quantitively the mechanical interaction with the surrounding bone tissue, when the bone scaffold is implanted. Thus, the purpose of this study was to analyze structural behavior variance, according to porous structures of the bone scaffold. This study set the proximal femoral head as the implantation skeletal system, and defined bone scaffolds (i.e. triangular, rectangle, circular, honeycomb) with four porous structures. Then, structural behavior variance was analyzed, caused by the implantation of bone scaffolds. As a result, it was quantitatively confirmed that a porous structure such as a normal bone that can transmit and support an external load is important.
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Computational comparison study of virtual compression and shear test for estimation of apparent elastic moduli under various boundary conditions Jisun Kim, Jung Jin Kim International Journal for Numerical Methods in Biomedical Engineering.2024;[Epub] CrossRef
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