This study presents a distortion analysis of a welded T-joint by using the virtual manufacturing (VM). Two different nonlinear 3D FEM-based VM systems, namely the general purpose MSC Marc/Mentat and the specialized Simufact.Welding software are compared and verified with the experiment. Both simulations are conducted based on an uncomplicated procedure without considering enormously on the weldment shape and resulting transient temperature distribution. Within this VM procedure, the heat source is modeled following Goldak’s double ellipsoid and the flow curve as one of the material properties of low carbon steel S235 is added with only one strain rate (0.001 s) based on non-linear isotropic plasticity model and von-Mises yield stress criterion. As the final outcome, the simplified procedures, weld geometry, and material properties will reduce the pre-processing without deteriorating the distortion results tremendously. Welding provides more structured and clearer simulation steps with more precise results of the angular distortion (Average of 7.25%) compared to the general purpose MSC Marc/Mentat (Average of 14.5%). This simplified simulation procedure without heat source and temperature calibration as well as complex material properties can be recommended for implementation if the time matter is constrained and the results are expected to be moderate.
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Investigating the effect of varying multi-pass welding sequence and plate thickness with manhole on plate distortion Ahmed B Salman, Abd Elhamid I Gomaa, Sallam A Kourietm Journal of Physics: Conference Series.2025; 3058(1): 012020. CrossRef
Numerical Simulation and Experimental Investigation of Temperature and Residual Stress Distributions in a Circular Patch Welded Structure Mato Perić, Sandro Nižetić, Zdenko Tonković, Ivica Garašić, Ivan Horvat, Ivanka Boras Energies.2020; 13(20): 5423. CrossRef
In this study, pyrolytic graphite was applied to overcome the conventional cooling system. Pyrolytic graphite is an anisotropic material with high thermal conductivity in the X-Y direction and low thermal conductivity in the Z direction. The advantage of high thermal conductivity in the plane direction is applied to improve the performance of the cooling capacity transceiver module housing made of aluminum. In comparison with the housing using the aluminum, the housing applied to the PGS plate shows a higher cooling performance on the average temperature of chips and the temperature variations by 2.79% and 49.98%. The heat dissipation performance was investigated according to the thickness of the PGS and the via the shape. When the factor of thickness in PGS plate was “0.375”, the average temperature of the chip was the lowest, and the temperature variation decreased due to increasing the factor of thickness in the PGS plate. In the case of the via shape, the “separation plate” showed the lowest average temperature of chips and the “plate” showed the lowest temperature variation.
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Hybrid battery thermal management system coupled with paraffin/copper foam composite phase change material Seunghoon Lee, Hyoseong Lee, Yong Joo Jun, Hoseong Lee Applied Energy.2024; 353: 122043. CrossRef
Research on advanced cooling system design is significant in achieving a high turbine inlet temperature in the gas turbine industry. The higher turbine inlet temperature of the gas turbine increases thermal efficiency. However, it also aggravates the gas turbine deterioration, lifespan, and efficiency. In this study, a numerical model is developed for simulating the cooling performance of the gas turbine vane with the turbine inlet temperature of 1528 K. The impact of the coolant air flow rate and hole-shape were investigated. The expanded hole shape had better cooling performance than the general cylindrical shape, and showed higher cooling efficiency. We suggest that there is a relationship between the shape of the film cooling holes and the cooling air flow rate that achieves the desired cooling effectiveness.
Snow removal equipment in Korea has been developed to remove snow from roads by pushing it away with snow shovels or dispersing it into the air with snow blowers. However, in urban areas, it is difficult to use snow blowers. And piled snow on sidewalks not only hinder pedestrians from walking by, but also melt onto the roads during the day and freeze at night, causing traffic accidents. As a solution to this, there has been a need to develop a machine which melts snow on the place where high priority is given for snow clearing such as airports, roads of frequent black ice occurrence, and main traffic facilities. This paper describes the main design points and experimental results in developing the snow melting system composed of the burner, blower, water tank, etc. Hot air from the burner spouts into the water tank and some of it rises through the outer jacket where hot air is mixed with water in the tank, heating it. Hot air spouted to the bottom of water tank and hot water pouring from the head of the outer jacket are two sources of snow melting in designing the equipment.
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Study on Thermal Efficiency and Heat Transfer Analysis due to the Application of Snowmelting Deck of Carbon Fiber Heating Wire Jeong-Keun Kim, Hong-Gun Kim, Hee-Jun Eun, Lee-Ku Kwac Journal of the Korean Society of Manufacturing Process Engineers.2023; 22(2): 39. CrossRef
Recently, applying nanoscale functional materials, there have been great advances in the flexible sensor system, which provides a large number of applications for soft electronics, such as skin-attachable sensors, artificial electronic skins, and soft robotic systems. Here, we developed a highly sensitive and flexible device on the basis of polymeric piezoelectric nanofibers and elastomeric packing structures. To produce the nanofibers, we applied the electrospinning process with a representative piezoelectric co-polymer, poly (vinylidenefluoride-co-trifluoroethylene) (PVDF-TrFE). Unlike the conventional electrospinning, we applied an anisotropic fiber collection system, which could obtain uniaxially aligned nanofiber array. The aligned nanofibers were sandwich-packed with bridge-shaped PDMS substrates, thereby integrating the flexible piezoelectric sensor. As an external force made a deflection of the bridge in the sensor, the embedded nanofibers generated piezoelectricity in a longitudinal direction of the fibers. The piezoelectric sensor generated good discernable outputs versus the varied mechanical input deflection from tens of micrometers to the sub-micrometer. With this great sensing ability, we could monitor heart pulse signals on the wrist skin by measuring tiny deflections generated from the expansion of the radial artery underneath the skin. Our study suggests a potential application of flexible sensor in the field of wearable health-monitoring medical systems.
Superhydrophobicity and anisotropic wettability can be simultaneously achieved by simple groove pattern on a surface. To verify those characteristics experimentally, we fabricated the micro-grooved surfaces with four different groove widths. Static contact angles were measured with the sessile drop method to investigate the apparent wettability and wetting states. All four surfaces exhibited the static contact angles well fitted to those estimated on the Cassie-Baxter state in which favorable water-repellency was expected. The static contact angles measured perpendicular to grooves were higher than those measured parallel to grooves. This anisotropic wettability was also observed with the sliding angle at the onset of the droplet moving when the surfaces were tilted. The sliding angles measured perpendicular to grooves were much higher than those measured on the smooth surface without micro-grooves. Conversely, the sliding angles measured parallel to grooves were smaller than those measured on the smooth surface. Because the sliding angle as well as the contact angle hysteresis reflect the water-repellency, the micro-grooves clearly made the surfaces anisotropic water-repellent.
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Wettability and Collision Behavior of a Droplet on Anisotropic Micro-pillar Array Surface Sanghyun Lee, Sangmin Lee Journal of the Korean Society of Manufacturing Process Engineers.2023; 22(1): 1. CrossRef
This paper proposes a myoelectric hand prosthesis with an easy control strategy to apply more conveniently with just two EMG sensors. The myoelectric hand prosthesis is composed of a multi-DOF finger mechanism, a controller, and an intuitive control algorithm. The developed hand prosthesis has 6-DOFs and can perform eight hand motions using the intuitive control algorithm. The proposed intuitive control algorithm classifies four grip motions and four gesture motions; we used the thumb position of the hand prosthesis and three EMG signals (Co-contraction, flexion, and extension) generated from the two EMG sensors. From the experimental results, we demonstrated that the proposed myoelectric hand prosthesis is applicable to amputees as a hand prosthesis.
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Development of Multifunctional Myoelectric Hand Prosthesis System with Easy and Effective Mode Change Control Method Based on the Thumb Position and State Sung-Yoon Jung, Seung-Gi Kim, Joo-Hyung Kim, Se-Hoon Park Applied Sciences.2021; 11(16): 7295. CrossRef
Development of multi-degree-of-freedom hand prosthesis cover with sensory recognition Sung Yoon JUNG, Hyo Jong YOO, Seung Gi KIM, Se Hoon PARK, Jin Kuk PARK, Joo-Hyung KIM, Hyunjun SHIN Journal of Biomechanical Science and Engineering.2021; 16(2): 21-00076. CrossRef
Along with the recent spread of 3D printing technology, researchers have developed various materials and equipment, now widely disseminated among individuals and industries. However, most of the current metal 3D printers generate the cutting paths using cutting software only, which doesn’t consider heat input of the plasma or laser. In the wire arc additive manufacturing (WAAM) system, a projection algorithm is created through the CATIA application programming interface. Different from the existing cutting algorithm, this algorithm converts a two-dimensional (2D) image into a three-dimensional (3D) structure by orthogonal projection and a voxel algorithm that expresses a 3D finite volume element. To fix the (x, y) coordinates and the z (Height) coordinate to be on the 2D plane, the projection algorithm models the 3D geometry orthogonal to the 2D plane. The bead modeling data and the step-over values generating the laminate shape were determined. The core of the voxel algorithm that models the free-shape lamination obtains the point location of the wire arc, considering the bead size and the distance between the layer spacing and the voxel center point (According to the processing conditions). Finally, the correct projection and voxel algorithms are selected using a lamination path-acquisition strategy.
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Analysis of Endmill Cutting Characteristics Based on the Machining Path during Postprocessing of Wall-shaped Structures
Fabricated by Wire Arc Additive Manufacturing Hwi Jun Son, Seok Kim, Young Tae Cho Journal of the Korean Society of Manufacturing Process Engineers.2024; 23(3): 44. CrossRef
Parameter Optimization of WAAM with Pulsed GMAW for Manufacturing Propeller-Shaped Blade Sang-Woo Han, Hojin Yoo, Seungcheol Shin, Hansol Kim, Geonho Lee, Jongho Jeon, Sangjun Han, Jungho Cho International Journal of Precision Engineering and Manufacturing.2023; 24(7): 1103. CrossRef
A Study on the Implementation of Virtual Motion Control in Wire Arc Additive Manufacturing Process Using Robot Simulator Chang Jong Kim, Seok Kim, Young Tae Cho Journal of the Korean Society for Precision Engineering.2022; 39(1): 79. CrossRef
The measurement temperature characteristics in a semi-opened furnace used for performance evaluation of medium/low temperature ceramic fuel cells were experimentally examined. Temperature measurement positions were classified into two cases with the attached condition (A thermocouple is in contact with fuel cell surface) and the floated condition (A thermocouple is apart from the fuel cell surface). Compared to the floated condition, the attached condition exhibits the characteristics of higher measurement temperature and better temperature stability. When the measurement temperature of the attached and floated conditions based on calibrated temperatures were controlled to 250°C, the peak power density of ceramic fuel cells with yttrium-doped barium zirconate thin-film electrolyte was measured at approximately 50% smaller for the attached condition comparison with the floated condition. Comparison of the ohmic area specific resistance for ceramic fuel cells with yttria-stabilized zirconate substrate electrolyte showed that, for the performance evaluation reliability, the attached condition is more appropriate than the floated condition.
Since IBM introduced the first hard disk drive (HDD) with 5 MB capacity in 1956, tremendous advances have been achieved in HDD technology and business. The areal density has increased 650 million times in the last 60 years. To implement the digital servo systems for high capacity HDD, elaborate servo patterns should be written on the disk surface during manufacturing processes. This process is called servo track writing (STW). When the servo track pitch reaches 50 nano-meter, the position error resolution should be less than 5 nano-meter for the drive servo and STW operations. The STW technology is in the realm of nano-mechatronics and should address precision motion control and manufacturing issues. Initially, all STW process were conducted inside the clean-room using special STW equipment. With ever-increasing track density, as well as the STW time and manufacturing costs, the industry has developed the STW technology that could move the STW operation to the outside of the clean-room and eliminate special equipment. Many innovative STW technologies have been invented and successfully implemented such as conventional STW, multi-disk writers, printed magnetic printing STW, spiral STW and spiral-seeded STW. With the successful implementation of these state-of-the-art technologies, HDD production has become more efficient and flexible.
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An Optimal Approach to Auto-tuning of Multiple Parameters for High-Precision Servo Control Systems Nam Guk Kim Journal of the Korean Society of Manufacturing Process Engineers.2022; 21(7): 43. CrossRef
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