Earticle

Due to the development of the industry, the machinery of plant facilities becomes large and operates at high speed and high power. Workers at plant facility sites are exposed to high noise and impact noise, and the number of people with noise-induced hearing loss is increasing every year. Therefore, in order to minimize such damage, many efforts have been made to reduce the noise of large machines in production facilities. Measures, education, and recommendation of wearing hearing protectors are needed to protect the hearing of workers in high noise industries. In addition, it is urgent to reduce noise sources by blocking noise propagation paths, such as installing noise boxes and silencers, and installing facilities and equipment that generate less noise. It is necessary to repair the noise reduction device of the large machine of the plant or to study the noise reduction device when designing the plant.

In the present study, to investigate the cooling characteristics of the multi-heat pump with 3 indoor units, 7 indoor unit combinations and 3 setting temperatures are selected to study the cooling characteristics during steady-state operation. The cooling capacity, power consumption, COP, compressor high and low pressure of the heat pump are tested under the cooling standard temperature conditions using an air enthalpy multi-calorimeter. The experimental results show that, except for an operation with an indoor unit capacity of 30% or less, the cooling capacity, power consumption, and compressor operation frequency increase as the capacity of the indoor unit increases and the setting temperature of the indoor unit decreases. COP increases or decreases according to the compressor frequency, and is the best at 50-80% capacity of the indoor unit. As the compressor frequency increases, the compressor outlet pressure increases by about 30%.

The flange spreader has been used to withdraw gaskets and valves during butterfly valve maintenance. When using the conventional flange spreader, an excessive working space (pipe separation distance) appears, and the pipe and flange are damaged by the load. Also, the equipment can’t be operated safely when the pipe has eccentric fitting. To solve the problems, a valve easy out tool with collet was developed for safely fixing and spreading flange. By using Ansys Workbench 2021 R2, the structural analysis of the original collet was performed, and shape design of the collet was carried out to improve structural safety.

Hydrogen infrastructure, for instance, such as hydrogen stations, supply chain network, is important in society of hydrogen economy. Special alloy are frequently used to prevent the hydrogen embrittlement in hydrogen vehicles, semiconductor factories and so on. Because special alloy including Monel material has high strength and high hardness, it is known as the hard-to-cut or roll material. This paper aims to investigate the characteristics and safety on bearing and shaft, which consist of key parts of rolling unit, through structural analysis. As the results, it showed that the bearing was weaker than shaft. Further the bearing was safe up to 20.4 ton, which was about 2 times of maximum of roller reaction force in case of considering as static load. However, the bearing was safe up to 10.2 ton in case of considering as repeated load.

Climatologists have warned rapid climate change of the earth and it will cause a big disaster worldwide. the rapid climate change is mostly due to emission of greenhouse gases. To reduce greenhouse gases, many countries have prepared protocols, agreements, and treaties. IMO(International Maritime Organization) have established the protocol to decrease ship’s greenhouse gases emission and they consider the nuclear power source is an option to replace fossils fuels. Our study focused on elemental technologies related to a nuclear powered ship and, the passive residual heat removal system(PRHRS) is one of topics in our study. As the mandatory of the post Fukushima accident, PRHRS for a nuclear powered ship has been studied. We invented the new concepts of PRHRS which is optimized to a nuclear powered ship. The numerical analysis results indicated that the system is very reasonable. Based on the numerical analysis, an experiential loop was set and we preliminary tested the performance of the system under the reduced scale. The experimental results came with the numerical analysis results well.

In this study, two ventilation holes were considered to prevent condensation in the circular column supporting the provision crane on a training ship(Saenuri) for Mokpo National Maritime University. The ventilation holes could be understood as the most simple and inexpensive way to prevent condensation because it was formed only by drilling. If sufficient ventilation is provided, the insulation and corrosion of an electric motor can be improved, and a comfortable state can be ensured in the circular column. The circular column had an electric motor for driving the provision crane so that the basic principle was to utilize the kinetic energy for the flow field from a cooling fan in the circular column. The ventilation holes attenuated the low-velocity area in the circular column and contributed to internal flow circulation with updrafts. The results were discussed through numerical analysis based on computational fluid dynamics.

The lane departure warning device can not detect the lane to be driven in the future by sensing the departure of the lane passing by during driving and warning the driver. Considering the safe operation of the truck, it is also expected that the departure of the future lanes according to the dynamic weight and speed of the current truck should be predicted. This study attempted to predict whether or not to deviate from the lanes of curved roads to be driven in the future according to the current dynamic driving weight and speed in consideration of the safe driving of trucks.

This study compares and analyzes the drogue shape applied to aerial refueling with the U.S. Navy drog shape through basic analysis of the model based on the flying fish shape, a marine creature. Flying fish is a creature that is advantageous for non-powered downhill, and this shape is applied to the probe feeding method to minimize the burden on the pilot and the need for refueling technology, which are disadvantages of the probe method. To this end, the results through analysis of basic studies were confirmed, and the superiority and insufficiency of the flying fish shape model and the US Navy drogue model were compared. Therefore, as confirmed through analysis, the flying fish model had a 14.1% lower maximum air pressure and a 9.1% faster maximum speed. Based on this, it is hoped that the advantages and disadvantages of flying fish shape models will be confirmed through actual flight tests in the future.

Test of the operating characteristics and energy saving performance of a container cooling system that reduces the operating energy of a refrigeration system using a loop thermosyphon heat exchanger that removes heat by temperature difference between outdoor and indoor was performed. As a result of the experiments, when the loop thermosyphon and the refrigeration system were operated simultaneously, the refrigeration system operated intermittently by reducing the heat load. As the temperature difference between indoor and outdoor increased, the operating time of the refrigeration system decreased and the energy efficiency rate increased. Energy efficiency rate showed a tendency to increase with increasing temperature difference, and the predicted correlation of energy efficiency rate using the performance of the loop thermosyphon heat exchanger and the refrigeration system was relatively consistent with the experimental value.

In this study, the noise reduction effect of the steam vent silencer was investigated by performing a transient flow analysis applying the Loss Model, a porous flow analysis model, and calculating the noise intensity from the pressure fluctuation according to the time change. As a result of flow analysis, it was confirmed that the noise intensity decreased as the number of diffusers and the number of splitters made of foamed aluminum increased. In the case of three-stage diffusers, the noise intensity decreased by up to 33.4 dB when six foamed aluminum with a thickness of 150mm were installed.

This research is to study the solution to the defects in maintenance and inspection that can be predicted/prevented in advance among human factors that account for more than 70% of the causes of aviation accidents. Traditionally, mechanics have performed visual inspections of aircraft exteriors. Due to this, there were factors that affect the human ability of mechanics in aircraft maintenance and inspection, safety problems when performing the upper part of the aircraft inspection, and the difficulty of precise inspection. To improve these problems, we conduct a study on an AI drone inspection system that has deep-learned samples on aircraft damage/defects. In this paper, we describe the aircraft maintenance inspection checklist, non-destructive inspection types, types of aircraft damage and defects, deep-learning highly reliable AI drone inspection systems, and the expected effects of this technology and future applications. Through this system research, it is expected that mechanics will efficiently inspect the aircraft through the optimization of aircraft maintenance system technology to prevent aviation accidents in advance and reduce time and economic costs.

Motor-operated valve functions to block or connect the flow of fluid in nuclear power plant and especially safety-related valves are evaluated with operability margin calculations, that should have positive value in both open and close stroke. Although all actuators have inertia force which increase operating margin of valve closing stroke, inertia force, after control switch operation in actuator is not considered in evaluating operability margin calculation process. In this paper, the hidden margin by inertia force of each actuator model in closing stroke was studied quantitatively.

In order to cope with climate change, the UN Climate Summit announced a policy to reduce carbon emissions to 0% by 2050. As a result, hydrogen energy is attracting attention as a new energy. Hydrogen energy is one of the future clean energy sources and is the most abundant and ideal fuel on Earth that does not emit pollutants. On the other hand, there is a risk of wide explosion range, easy ignition, and fast flame speed. As a result, There is limited use of hydrogen gases, and research is being conducted to safely use hydrogen gases. However, the localization rate of hydrogen-related equipment parts is low and dependence on foreign countries is high. In order to reduce dependence on foreign countries, this study designed and analysis a model of ultra-high pressure relief valve, which is a safety device for hydrogen charging stations. In order to evaluate the structural stability, a spring, a valve disk, a valve guide, and a valve spindle, which are components of an ultra high pressure relief valve, were applied with pressure resistance test and water pressure test criteria according to KS B ISO 19880-3, and analyzed using an Ansys workbench 2021 R1. Through the analysis results, the structural stability of the relief valve under the water pressure test and the pressure resistance test conditions confirmed.

The Alkali-Metal Thermal to Electric Converter (AMTEC) can be used as a next-generation power generation technology related with a large thermal energy storage. In particular, this technology is expected for the higher efficiency by a cascade power generation with the thermoelectric generator(TEG), and the temperature distribution becomes a very important design parameter in this case. In this study, the temperature distribution of the AMTEC unit was analyzed through CFD analysis, and design points were discussed based on the results.

Ball stud parts are manufactured by a cold forging process, and fastening with other parts is secured through a head part cutting process. In order to improve process quality, stabilization of the forging quality of the head is given priority. To this end, in this study, a predictive model was developed for the purpose of improving forging quality. The prediction accuracy of the model based on 450 data sets acquired from the manufacturing site was low. As a result of gradually multiplying the data set based on FE simulation, it was expected that it would be possible to develop a predictive model with an accuracy of about 95%. It is essential to build automated labeling of forging load and dimensional data at manufacturing sites, and to apply a refinement algorithm for filtering data sets. Finally, in order to optimize the ball stud manufacturing process, it is necessary to develop a quality prediction model linked to the forging and cutting processes.

In the present study, the experimental study was conducted using a multi-calorie meter, to investigate the cooling performance and cycle operation changes of the multi-heat pump (3 indoor units) for the low outside temperature in summer. The test temperature condition was the low cooling temperature, and the normal performance and dynamic behavior of 3 rooms, 2 rooms, and 1 room were measured to understand the operating characteristics of seven 7 indoor unit combinations. As a result of the experiment, the cooling capacity and COP of the multi-heat pump at low cooling temperature were about 10% and 6% higher than those of the cooling standard temperature. In addition, the dynamic behavior of the indoor units of 3 and 2 rooms was observed differently due to the load difference according to the indoor unit combinations and the non-uniformity of the refrigerant amount. And, when starting the heat pump, the compressor had a maximum peak value and stabilized by repeating the decrease and increase for each indoor unit combination.

For a plastic diffusion lens to uniformly diffuse light, it is important to minimize deformation that may occur during injection molding and to minimize deformation. It is essential to control the injection molding condition precisely. In addition, as the number of meshes increases, there is a limitation in that the time required for analysis increases. Therefore, We applied machine learning algorithms for faster and more precise control of molding conditions. This study attempts to predict the deformation of a plastic diffusion lens using the Decision Tree regression algorithm. As the variables of injection molding, melt temperature, packing pressure, packing time, and ram speed were set as variables, and the dependent variable was set as the deformation value. A total of 256 injection molding analyses were conducted. We evaluated the prediction model's performance after learning the Decision Tree regression model based on the result data of 256 injection molding analyses. In addition, We confirmed the prediction model's reliability by comparing the injection molding analysis results.

In this paper, numerical simulations were conducted to secure both flow distribution and uniform flow discharge through a wall mount type air sterilizer. In order to increase the reliability of the simulation results where there is no well-known validation case for air sterilizer, mesh sensitivity study was performed under the constraint that y+ set to one for k-w SST turbulent modeling for both the air sterilizer and the fan. The installation of various guides and structures was reviewed in the point of flow distribution and pressure drop inside the sterilizer, and the exhaust pressure conditions were predicted to secure uniform flow discharge at outlets. This study has been done based on the computational analysis during the development stage of the air sterilizer, and the results will be verified through physical testing after production of prototype.

CFD was used to study the change in the operation of the governor to check the effect of response delay due to residual air in the governor cylinder, which adjusts the pump RPM of the Turbine Driven Aux. Feed Water Pump(TD AFWP) in the Nuclear power plant. As a result of analysis, as the amount of internal air increased, the time delay also increased proportionally, and a time delay of up to 0.2 sec. occurred. As in the theory, it was confirmed that the cylinder operation delay occurred depending on the presence or absence of a compressive fluid such as air, but the time delay wat not enough to significantly affect the pump operation.

The main noise of a large machine can be divided into the noise generated during the work process and the noise of the equipment used in the work. The main noise in the noisy area is the air propagation sound caused by the operation of the rotating body. This is not fixed, but changes depending on the situation at the time of measurement. Workplaces exposed to noise can harm workers' health and cause related industrial disasters, resulting in many complaints and social problems, and eventually lead to a lot of damage in terms of productivity. Large machines that need noise reduction the most are motors, pumps, fans, blowers, and compressors. To reduce noise, mechanical structure or material changes are most effective. In this study, the noise reduction method and noise management method of large machines were investigated. To measure noise, the same method as ISO 3744 in Europe and JISA 8305 in Japan was used as KS A ISO 3744, KS A ISO 3746, which is a method of measuring the acoustic power level of machinery.

The Moving Particle Semi-implicit (MPS) method is one of most famous method in the particle-based computational fluid dynamics field. The MPS, the state-of-art method, is simple but intuitive methodology including multi-phase and complex structure interactions problems. However, the concept of particle method may contain the physical weakness. In order to avoid physical violence, the particle number density and kernel function were employed. Despite all the efforts, the microscopic problems were not easily resolved yet. In this study, the surface tension model was developed and added into the MPS method to strengthen physical phenomena and physics laws. The simulation result with new MPS method including surface tension model was compared with corresponding theoretical results and they show good-agreement.

The need for research on a sensor system that can monitor the dynamic load of a commercial vehicle in real-time is emerging because the development of autonomous vehicles is actively progressing worldwide. In this study, dynamic load measuing system of commercial vehicles was developed using the MEMs inclinometer attached to the leaf spring suspension. Test vehicle’s driving test was accomplished by changing speed and payload weight in several stages. Using the dynamic load measurement system, it was possible to check the weight shift and the change of stopping distance. When a driving speed increases from 30km/h to 80 km/h, the stopping distance increases from about 25m to 80m.

In this paper, we propose a dynamic stability prediction method for heavy vehicles based on Lateral Load Transfer Ratio. The key factors influencing vehicle roll motion are the vehicle's load, the position of the center of mass, the tread and the vehicle speed. Using these factors, we derive the lateral load transfer ratio (LTR) formula. In addition, we investigated LTR changes and vehicle rollover of heavy vehicles in various scenarios using TruckSim. As a result, the threshold value of the change rate of the LTR at which the vehicle rolls over was 0.68-0.72. Finally, we performed a numerical experiment to prevent rollover by calculating the optimal speed in the rollover situation.

Additive manufacturing is a new approach to design and production. This applies in particular to processes such as repair and rework of selected components. Additive manufacturing can produce almost any shape, and from an MRO part perspective, additive manufacturing offers tremendous advantages. The special feature of additive manufacturing is that it is particularly economical for small-volume production as the number of units is irrelevant compared to the existing manufacturing process. The purpose of this study was started from the MRO point of view, and it Identify changes and respond to the Blisk It is a study on the effect of changing the conditions on the path of the toolpath and the CAM during additive manufacturing using CAM after finding suitable conditions. metal powder.The metal powder withstands various corrosive environments and age hardening occurs very slowly. Inconel 718, which can be used in various applications such as nuclear facility-related parts, aerospace, oil facilities, turbines, and valves, was used. This is SUS 316L with good high temperature strength. The variable of the laser used in the study is the laser power, and the variables on the CAM are Operation, Stepover, Pattern, etc. In the relation between laser power and feed, when feed is specified as 500mm/min, laser power of 700W was most suitable. As for the conditions on NX CAM, ADDITIVE PROFILE Stepover was 0.8mm for Operation, and Infills and Finish for Pattern. When stacking, each layer should be overlapped with the result. Therefore, the stepover should be smaller than the laser spot size and reprocessing should be done in terms of repair, so infills and finish were applied to work larger than the actual product shape.

In this study, the following results were obtained by designing a high-efficiency hydrogel and colloid fusion applicator and checking production speed(hydrogel) and working setting time(coating time) by promoting the starting product. As a result of performing a product production test by manufacturing a starting product based on the process automation design, the production volume increased by about three times from 4m per minute to an average of 11m per minute. The working setting time(coating time) of the fusion applicator was shortened from the target of 10minutes to 1.69minutes, which had the effect of reducing the loss of work time.

Burr occurs at the bottom of the material as the material breaks during shearing, and sliver occurs in shear droop that occurs when a punch penetrates the surface of the material. Sliver refers to the shape of a long and thin thread, and it is an important defect that can cause a short when assembled into electronic parts other than a defect in the appearance of a product, an assembly defect in the post-process, and an injury to the operator. Sliver does not occur when the molding is completed only by the main shearing without pre-shearing, but sliver occurs when the main shearing is performed after the pre-shearing. The purpose of this study is to study the sliver generation mechanism that occurs during main shearing after pre-shearing. Using the material phosphor bronze C5210-EH(HP), the sliver was observed with the dimensions and stripping force of the pre-shearing as variables, and the effect of the pre-shearing on the sliver was studied. The product used in the experiment is a terminal, a press product that is assembled on a 0.4mm pitch FPC connector. Three experimental variables were selected: the X-axis allowance, the Y-axis length, and the stripping force in the dimensions of the pre-shearing. As a result of 12 experimental conditions, the X-axis allowance had a greater effect on sliver generation than the Y-axis length and stripping force. The cause of sliver during pre-shearing is that the shear droop part is elongated due to bending when the punch is lowered due to the hole in the bottom due to pre-shearing.

The global power generation industry is becoming a key power generation industry with gas power generation and renewable energy solar power generation. This research aims to focus on solving two problems as a method to improve the solar light collection efficiency among fixed variable deformation methods. Maintaining the proper temperature of the water injection device through automatic temperature detection to solve efficiency degradation, and establishing an automatic operation system by finding the optimal angle for each season, are intended to derive a value that can represent the optimal power generation.

Level 3 driving, which enters full-fledged autonomous driving, is becoming more common. And research on autonomous driving is growing rapidly. Therefore, there is a need for a hardware platform to implement autonomous driving, but the actual vehicle price is too high and the implementation conditions are very limited, so its usability is inevitably reduced. In this study, by providing an easy-to-access hardware platform for anyone to support autonomous driving research, compatibility with software platforms can be increased. As a result of this study, it is possible to conduct hardware platform and software platform education at the same time. Through this, trial and error due to errors in each of the two platforms can be reduced. In addition, various sensors, such as camera sensors and LiDAR sensors, were installed on the hardware platform, and a hardware platform capable of testing autonomous driving for education and R&D was conducted not only outdoors but also indoors with little external environmental impact.

This study was evaluated based on the items of KS B 6389. The study on the calculation of angular error and measurement uncertainty of HRc hardness measurement using statistical techniques using Rockwell measurement specimens with different hardness values ​​was analyzed, and the results were derived according to the change in the angle of the indenter part of the hardness tester and the specimen. As a result of the experiment, the test statistic P values ​​for angle changes such as 0°, 1°, and 2° were all 0.000 using the HRc 30 and 40 measurement specimens, so it was confirmed through the experiment that a significant difference occurred between them. In addition, the extended uncertainty value was calculated as 0.612 at the 95.45% confidence level, and the fact that the hardness test value came out smaller than the existing test value as the inclination angle increased was verified through experiments.

Screws are the closest and most familiar mechanical elements of everyday life, and are generally used so widely that there is no machine without screws. Screws are used to make it easier to combine objects with objects, and are also used to transfer large forces from machines. The most influential factor in the coupling of these screws is the effective diameter. If the effective diameter is not accurate, the support cannot be finished or endured, leading to a major accident. The importance of these screws cannot be ignored, so in this study, the effective diameter was measured using the three-wire method, the screw micrometer method, and the projector method, and the one-way factor design method was applied to determine the exact method compared to the KS standard.