Transportation industries, such as aerospace and automotive demand high efficiency using lightweight parts. Carbon Fiber Reinforced Plastics (CFRP) present promising materials for transportation industry parts due to their lightweight and highstrength properties. Forming and machining processes are required to manufacture parts from carbon fiber composite materials. The near-net shaping process forms the parts, and the final accurate shape and hole are accomplished using the machining process. However, high-strength carbon fiber chips and dust from the machining process cause cutting tool wear and low productivity. The hybrid CRD (Cutting, Routing and Drilling)/water-jet machine improves tool life and productivity because its water-jet process, employed before the mechanical machining process cuts roughly without chips and dust. In this study, the hybrid CRD/water-jet machine we developed was introduced and its machining performance was evaluated using a drilling process. The delamination factor and surface roughness of drilled holes were compared with the results from a conventional machine tool.
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Effect of Vacuum Suction on Dust and Exit Burr Removal in FRP Drilling Jong-Hyun Baek, Su-Jin Kim Journal of the Korean Society of Manufacturing Process Engineers.2022; 21(11): 29. CrossRef
Multistep Workpiece Localization with Automated Symmetry Identification for Aerospace Carbon Fiber Reinforced Plastic Components Minh Duc Do, Mingeon Kim, Duy Hung Nguyen, Soonyoung Han, Van Huan Pham, Hae-Jin Choi International Journal of Precision Engineering and Manufacturing-Green Technology.2022; 9(4): 1133. CrossRef
Drill bit with clip-edges based on the force control model for reducing the CFRP damage Jiaxuan Hao, Fuji Wang, Meng Zhao, Yu Bai, Zhenyuan Jia Journal of Reinforced Plastics and Composites.2021; 40(5-6): 206. CrossRef
Since becoming highly functional, complex and flexible, the machining system of CFRP(Carbon Fiber Reinforced Plastic) has recently become highly functional, complex and flexible, its has its controllers are changing into open and distributed structures. These, and need controlling to be controlled to maintain good quality of for a quality of machined parts. In particularSpecifically, an open controller is required urgently needed to apply the optimal processing program for each material and development of embedded SW, which enables after-production of CFRP, CFRP-metal stack material, waterjet processing, inspection, and modification. As theThe characteristics of CFRP materials may create processing defects such as stratified material stripping and un-cut., a A process monitoring module that can minimize or prevent the defects this technology needs to should be applied to hence reducinge tool wear causedthrough by high hardness carbon fiber. Since CFRP is mostly made from additive forming, there are many drilling processes, that require precision measurement techniques and process signal monitoring technology, exist. Tsince the cutting force load and various signals generated during processing are weaker than those during metal processing. An open controller for process control and monitoring of a CFRP processing system was therefore developed. The system will then It is going to develop open controller SW structural design and open platform, multi-channel signal processing algorithm and sensor system, process specific functions (CFRP process control, boundary detection, etc.) and mount drilling tool parent monitoring algorithm on open platform.
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Comparative Analysis and Monitoring of Tool Wear in Carbon Fiber Reinforced Plastics Drilling Kyeong Bin Kim, Jang Hoon Seo, Tae-Gon Kim, Byung-Guk Jun, Young Hun Jeong Journal of the Korean Society for Precision Engineering.2020; 37(11): 813. CrossRef
The demand for inspection of high-speed systems for machined Carbon Fiber Reinforced Plastics parts for automobileindustry and aviation industry is constantly rising. One of the factors that degrade the performance of an inspection system is micro-vibration from the ground or structure where is placed. Various isolation systems that suppress the vibration have been studied classified as either passive or active system. The passive system is composed of a spring and a damper while the active system suppresses the vibration through an electronic control system using sensors and actuators. In this study, a voice coil motor (force constant 55N/A) acting as the actuator is optimally designed using permeance method and sequential quadratic programming algorithm to suppress the vibration and reaction force by a specimen moving stage. The two optimized voice coil motors are attached to a pneumatic mount that has an advantage in design based on the force and size constraints required by the user for an active vibration isolator with velocity sensors (GS-11d). The active vibration isolation system with the four active vibration isolators -23 dB and -20 dB at resonance frequencies in horizontal and vertical transmissibility performs better than a passive vibration isolation system.
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Carbon Fiber Reinforced Plastic (CFRP) materials which are superlight in weight and have high strength have recently been applied in the automobile and aerospace industry, etc. to achieve high fuel efficiency. CFRP is termed as ‘difficult to cut material’ due to its unique material properties. It’s considered to be highly sensitive in processing due to its laminated structure which would pose some challenges such as delamination, Pull-out, Burr and Uncut. Due to this, it’s maintenance and treatment costs are high. There are also limitations in the conventional Gantry Machine in 3D shape cutting of CFRP materials. To counter this challenge, a robotic abrasive waterjet system with the following features has been developed and installed on site; a high-pressure pump, monitoring system and a catcher for 3D Shape cutting., It’s performance has been successfully proved. Based on the result, we discovered that a 6 axes robot could execute 3D shape cutting of car hood due to its high movement flexibility. In the future it is projected to fulfill more kinds of CFRP materials cutting test on many car brands.
The gear ratio variable topology of a magnetic gear with an integrated harmonic modulator is analyzed using a magnetic permeance model. A dynamic characteristic equation is derived in consideration of the gear ratio between each layer constituting the magnetic gear: the driving side, the driven side, and the control side layer. Based on derived transfer function, the frequency characteristic between driving torque and angular speed of the driving side is analyzed. Theoretic model is compared with an experimental test result using the in-house dynamometer. In the general magnetic gears, the gear ratio is variable so that speed between each layer decelerates with gear ratio, but transmission torque is constant regardless of gear ratio. In this study, these characteristics are also verified through theoretical methods and experimental results, respectively.
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Gas turbine, the core equipment of the power plant, is capable of rapid starting operation and has less carbon dioxide emission than coal power plant. So it has the advantage of being eco- friendly. In order to increase the efficiency of these gas turbines, the turbine inlet temperature has steadily increased and to ensure the safety of the gas turbine, means for protecting parts exposed to high temperatures have also been developed. Protective coating technology is one of them, which plays the role of lowering the temperature of the base metal and preventing oxidation and corrosion. In this paper, thermal fatigue test simulating the operation environment was conducted using the Amdry 9951 protective coating powder applied to the HPT Heat Shield for the Alstom GT 24 gas turbine and the performance before and after the thermal fatigue test was evaluated and examined by adhesive strength test and SEM (EDS) analysis.
Due to urbanization, it is difficult to secure a large knuckle crane workspace. To solve this problem, we developed a small knuckle crane combined with a one-ton truck. In this study, the safety of small knuckle cranes is evaluated through Finite Element Analysis. Shape optimization was performed using the Design of Experiment for parts speculated to have failed from fatigue. As a result, maximum equivalent stress of a plate in link speculated to have failed from fatigue was reduced by approximately 84.2%.
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Bedridden patients develop pressure sores, as a result of poor blood circulation and excessive humidity. Conventional bedsore mattresses are designed to vary interface pressure zones, between the body and mattress for improved blood flow. Another approach is to control interface humidity, by forced air circulation. An ideal solution may be interface humidity control, in addition to pressure zone control. In this paper, a thin and flexible structure is suggested for forced air ventilation, that can be placed atop pressure zone controlled mattresses. With fabric covers, drying performances are evaluated for a range of air flow rates.
FE analyses have been performed to characterize triaxiality of Eco-Al7021-T6, one of representative environmentally-friendly materials with lightweight effect, in this study. Also, a novel shape specimen with double notched and a central hole, i.e., DNC specimen, was suggested to obtain two different values of triaxiality from one trial simultaneously. Tensile tests for the standard type specimen were conducted and true stress-true strain relationship, as well as force-displacement curve were obtained. It was revealed that two different values of triaxiality were successfully achieved from the novel DNC specimen, and the number of tests for triaxiality can be reduced with the use of the DNC specimen.
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Linear roller bearings are often used for linear positioning systems due to high load-carrying capacity, precision, and durability. In this paper, guide rail deformation of linear roller bearings under vertical and horizontal loads, has been experimentally investigated. An experimental system was made to measure displacement of the carriage and guide rail deformation of a bearing with varying load. Guide rail deformation inaccessible inside the carriage, was estimated by measured carriage displacement subtracted from calculated carriage displacement from a commercial program, that does not consider flexibility of guide rail and base. In addition to estimated deformation, guide rail deformation outside the bearing carriage was measured to make a complete guide rail deformation curve due to external loads. Results revealed deformations occurring in guide rail and base are significant, as to affect bearing accuracy. Thus, deformations in guide rail and base should be considered, to estimate stiffness and motion accuracy of linear roller bearing under external loading conditions.
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A new technique based on the reversal method, is suggested to measure squareness error of the two-linear axes system. The technique uses the L-type steel bar, a capacitive sensor, and three experimental installations required to measure squareness error and two horizontal straightness errors. Profile and squareness of the L-type steel bar are estimated, by using the principle of the reversal method. Also, setup errors inevitable at installation, are separated from measured data using the least square method. Multi-DOF errors of two-linear axes system are measured and analyzed, using the suggested technique. Also, the reference mirror with flatness of 30 nm is used to verify the suggested measurement technique. Difference between the two measurement methods is 3.25 arcsec, a value within measurement repeatability.
Recently, there are numerous studies on robots to function with smoother movement and high efficiency. It is difficult to develop robots with smooth movement and high efficiency. To solve this problem, the Series Elastic Actuator (SEA) is used. It is an actuator that gives compliance to a general actuator. Presence of compliance will bring to advantages. First, robots can reduce external impact force with high compliance. Second, the force of SEA can be controlled more precisely, than a normal actuator. Some SEAs have been developed with many functions, but the structure is complicated. So, in this study, the SEA with compact and simple structure was proposed. Shape of the SEA is cylindrical, and its diameter, height and weight are 70mm, 338mm, and 2.5kg respectively. The SEA was modeled in a two-degree of freedom mass spring damper system. To demonstrate travel response characteristics of the SEA, experiments were conducted and the result revealed design of the SEA is validated.
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