Compacted graphite iron (CGI) has been widely used in the automobile industry because of its good mechanical properties. CGI has better strength as compared to grey iron due to its internal structure. It includes graphite particles, which enhance the adhesion between graphite and iron. However, the material characteristics can negatively affect the machinability. In this study, cryogenic milling was performed for CGI450. It is well known that cryogenic machining is effective in improving the machinability. The process included spraying liquid nitrogen as a cryogenic coolant, and the influences on machinability were experimentally investigated with a focus on the cutting force and surface roughness. When liquid nitrogen was sprayed, the cutting force was slightly increased due to the cold-strengthening effect. On the other hand, surface roughness was dramatically decreased by 44.7% as compared to dry milling because brittleness of work material was increased by cryogenic coolant spraying.
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Tool life assessment of high strength cast iron alloys in dry face milling operations Alcione dos Reis, Gustavo Henrique Nazareno Fernandes, José Aécio Gomes de Sousa, Luiz Leroy Thomé Vaughan, Feliciano Cangue, Álisson Rocha Machado, Wilson Luiz Guesser Journal of Manufacturing Processes.2024; 111: 180. CrossRef
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In this study, a wire electrical discharge milling electrode was developed, and electric discharge machining characteristics were studied by using the electrode. The wire electrical discharge milling electrode is a form, in which the wire is conveyed by using a cylindrical rod with a hemispherical end as a guide, and it also rotates in one direction around the guide axis. If the wire electrical discharge milling electrode is used in electrical discharge machining (EDM), there is no need to consider electrode wear compensation. The EDM characteristics according to capacitance of the RC circuit and the rotational speed of the wire electrical discharge milling electrode were examined. The machining conditions were selected, and a hemispherical shape with good shape accuracy and fine surface finish was fabricated in two stages of roughing and finishing. By applying the wire electrical discharge milling electrode to the electric discharge milling process, straight and curved shapes were successfully machined.
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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.
This paper proposes a simplified path-following control method for an Unmanned Surface Vessel (USV) considering towed Unmanned Underwater Vehicles (UUV). For dealing with an effective USV dynamic model, 1st order of the linear system with time delay and gain value are applied rather than applying a non-linear dynamic model, and it is identified with real vessel data from several straight and turning experiments. Then, USV attitude and velocity are controlled by multi-loop Proportional-Derivative (PD) and proportional controller. A USV guidance scheme is derived through a UUV guidance scheme to support autonomous navigation for towed UUV, and combination of cross track and Line of Sight (LOS) guidance is presented for adaptive path following. Finally, to validate the performance of the proposed USV path-following control method with respect to the towed UUV guidance scheme, the results of simulations are presented.
A fixing frame applied with Foam Cored CFRP Sandwich Composite (FCCSC) that replaces SAPH440 steel used in the fixing frame for hydrogen storage was designed, and its structural safety was evaluated. In the design of the fixing frame, FCCSC was implemented by PMI foam core, a Bakelite mount, and Carbon Fiber Reinforced Plastics (CFRP) using woven carbon fiber prepreg. Unlike the steel fixing frame, the FCCSC-applied fixing frame had a cross-section of hollow-rectangular, and its validity was confirmed through finite element analysis. Structural analysis of the designed FCCSCapplied fixing frame and steel fixing frame was performed. Under the extreme load condition of 9G acceleration, the steel fixing frame showed the lowest safety factor of 1.14 based on the yield strength in the opposite direction of gravity. On the other hand, the FCCSC-applied fixing frame showed a safety factor of 7.6 at the maximum principal stress and 3.15 at the shear stress. Through this result of structural analysis, it was verified that the FCCSC-applied fixing frame, which was 25.8% lighter than the steel fixing frame, was 1.8 times safer.
Structural color refers to a phenomenon, in which white light is influenced by the structure and the color is expressed. It can express various colors depending on the structures and has an advantage in terms of durability compared to the conventional dyeing processes. However, the structural color from a single layer easily varies depending on the light irradiation angle or measurement angle. Hence, numerous studies have been conducted to improve the angle-independency of structural color by fabricating multi-layers with complex nano-patterns. But, they usually require highly controlled processing environments and are not suitable for large-area manufacturing. Therefore, this study aims to develop a fabrication process by utilizing ultra-precision machining and silicon molding. Here, angle-independent structural colors were implemented with multi-layer micro-patterned films. Through the experiments, angle-independency was evaluated by varying the number of silicon films and measurement angles. RGB and HSV values were extracted from the images and applied for quantitative analysis. The suggested fabrication process successfully exhibited the angle-independent structural color with given patterns and film thickness. It is expected that this study can contribute to improving the multi-layer fabrication processes concerning machinability and large-area production.
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Many of the workers are exposed to work that burdens the musculoskeletal system, and musculoskeletal diseases, such as low back pain, are increasing every year. Various muscle support systems, such as wearable robots, have been developed to prevent musculoskeletal diseases at industrial sites, but the system is bulky. Therefore, the total weight is high, it is inconvenient to wear, and the wearer cannot freely perform the activities when power is not supplied. In this paper, in order to compensate for the shortcomings of the hard-type wearable robot system, a soft-type wearable suit using an elastic band was manufactured so that it is light and portable, as it does not require an actuator. The experiment was conducted to verify the effect of muscle strength assistance through an experiment (Measurement of Maximum Waist Torque and Measurement of the Approximate Dose) on the effect of the soft wearable suit. In addition, by making two different types of elastic bands in the wearable suit, it was possible to classify the more effective types for the waist and lower extremities according to the elasticity by comparing the muscle strength assisting effect according to the elastic band.
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One of the problems in inverse dynamics calculation for the inertial measurement unit (IMU)-based joint force and torque estimation is the amplified signal noises of segment kinematic data mainly due to the differentiation procedure and segmental soft tissue artifacts. In order to deal with this problem, appropriate filtering methods are often recommended for signal enhancement. Conventionally, a low-pass filter (LPF) is widely used for the kinematic data. However, the zero-phase LPF requires post-processing, while the real-time LPF causes an unignorable time lag. For this reason, it is inappropriate to use the LPF for real-time joint torque estimation. This paper proposes a Kalman filter (KF) for inverse dynamics of IMUbased joint torque estimation in real time without any time lag, while utilizing the smoothing capability of the KF. Experimental results showed that the proposed KF outperformed a real-time LPF in the estimation accuracy of hip joint force and torque during jogging on the spot by 100 and 29%, respectively. Although the proposed KF requires the process of adjusting covariance according to the dynamic conditions, it can be expected to improve the estimation performance in the field where joint force and torque need to be estimated in real time.
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Recently, industrial manufacturing has developed into additive manufacturing, benefiting from multi-item small-sized production and effective manufacturing. Importantly, Wire Arc Additive Manufacturing, which uses metal wires, is attracting worldwide attention for its high-quality metal product technology. Technological innovation that combines virtual physics with reality through big data communication, such as process variables along with Wire Arc Additive Manufacturing, is an essential task for implementing smart manufacturing technology. Due to the characteristic of Wire Arc Additive Manufacturing, numerous variable conditions exist, making it difficult to standardize robot"s process path data generation algorithms and data application methods, and this data generation method is being studied as a core element technology. The present study generated foundation process implementation, simulation, and generated path data for robots in virtual space using RoboDK, which provides robot libraries from multiple manufacturers, and Python, which is a universal programming language. To implement the experimental data in practice, ABB"s industrial six-axis robots IRB-6700 and Fronius TPS500i were used to control the arcing plasma heat source, and the process path worked the same as simulation. Based on the underlying experimental results, this process can be applied to generation of additive manufacturing in the Wire Arc Additive Manufacturing process for 3D models.
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Artificial Intelligence Technologies and Applications in Additive Manufacturing Selim Ahamed Shah, In Hwan Lee, Hochan Kim International Journal of Precision Engineering and Manufacturing.2025; 26(9): 2463. CrossRef
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