Welding is the most widely used technology for manufacturing in the automobile, and shipbuilding industries. Fiber laser welding is rapidly introduced into the field to minimize welding distortion and fast welding speed. Although it is advantageous to use finite element analysis to predict welding distortion and find optimized welding conditions, there are various heat source model for fiber laser welding. In this study, a welding heat source was proposed using a multi-layered heat source model that encompasses most of the existing various welding heat source models: conical shape, curved model, exponential model, conical-cylindrical model, and conical-conical model. A case study was performed through finite element analysis using the radius of each layer and the ratio of heat energy of the layer as variables, and the variables were found by comparing them with the actual experimental results. For case study, by applying Adaptive simulated annealing, one of the global optimization algorithms, we were able to find the heat source model more efficiently.
The role of QR Code robots in smart logistics is great. Cognitive robots, such as logistics robots, were mostly used to adjust routes and search for peripheral sensors, cameras, and recognition signs attached to walls. However, recently, the ease of making QR Codes and the convenience of producing and attaching a lot of information within QR Codes have been raised, and many of these reasons have made QR Codes recognizable as visions and others. In addition, there have been cases in developed countries and Korea that control several of these robots at the same time and operate logistics factories smartly. This representative case is the KIVA robot in Amazon. KIVA robots are only operated inside Amazon, but information about them is not exposed to the outside world, so a variety of similar robots are developed and operated in several places around the world. They are applied in various fields such as education, medical, silver, military, parking, construction, marine, and agriculture, creating a variety of application robots. In this work, we are developing a robot that can recognize its current position, move and control in the directed direction through two-dimensional QR Codes with the same horizontal and vertical sides, and the error is to create a QR Code robot with accuracy to reach within 3mm. This paper focuses a suggestion of control method in QR Code-aware indoor mobility robots.
Building Equipment field is getting important recently which satisfies the requirement for pleasant living environment. But, the noise generated in the machinery room often violates the pleasant living environment of residents in complicated form of airborne noise and soild sound, its seriousness is increasing so that damage of noise can take large percentage of environmental complaints. So, soundproofing and insulation of sound which can minimize such noise and effective countermeasure in case of civil appeal are required, but research materials regarding building equipment are definitely insufficient domestically. In this respect, this study used Zwicker parameter which is applied by psychological and acoustic reactions according to sound quality, analyzed sound quality of 32 kinds of building equipment used in machine room, and analyzed correlation between dB(A) and PSIL which are items of Zwicker parameter and noise valuation based on that. As the results, if valuates altogether loudness and unbiased annoyance which have high correlation with other existing suggested valuating methods, it is considered that it can be utilized as basic data for more reasonable and accurate grasping characteristics of noise from building equipment and for building effective countermeasure in case of civil appeal.
In recent years, our reality is facing a serious risk of air pollution from transport vehicles. In particular, various exhaust emissions from diesel engines are pointed out as a serious cause of environmental pollution. This study attempted to study the potential of biodiesel as an alternative energy for CRDI diesel engines. When biodiesel 30% was applied, the smoke emission was reduced by 40% at 4000rpm compared to diesel. On the other hand, there was no significant difference in output, torque, and energy consumption. However, NOx emissions tended to increase compared to diesel. The applicability of biodiesel to CRDI diesel engines has been demonstrated for the characteristics of output and smoke emissions.
Universal joint damage occurred during the operation of a combat vehicle. Damage to the internal bushing and cracks of the rubber cover occurred, and a design change was promoted based on the cause analysis and improvement measures. The failure of the bushing is due to the occurrence of expansion due to fatigue load when the rotation proceeds in the presence of the assembly clearance of the cross joint. In addition, cracks in the rubber cover are caused by the deterioration of the intermetallic rubber surface. Through this failure mechanism analysis, severe durability factors were selected and accelerated durability tests were conducted. In this paper, the final limit life of universal joints can be evaluated through accelerated endurance tests. Furthermore, the endurance life of the product before the change and the endurance life of the product after the change are compared to prove the improvement effect through design changes.
Roto cap is usually used to diesel engine, especially, big-sized diesel engine such as ship, power plant and so on. Intake and exhaust valves are essential parts of diesel engine and thus roto cap is one of the most important parts of intake and exhaust valves. Roto cap consists of body, disc spring, spring & steel ball, retainer and stop ring. In this study, the body and disc spring in parts of roto cap were simulated using static structural analysis. The purpose of this study is to achieve the data for designing and improving the roto cap. As the results, the body of roto cap showed safety factor of 6.3 in even 2 times of 1370N(target load) and the disc spring showed safety factor of 4.9 in 2370N load.
Due to severe environmental pollution from ships, IMO(International Maritime Organization) is imposing strict controls on pollutant emission in ECA(Emission Control Area). There have been active studies to find fuel that could replace existing fossil fuel and especially in recent times, diverse studies on recycling of coffee ground are in progress. The annual domestic consumption of coffee was 150,000 tons according to the data of 2017 year and 99% of them are coffee ground to be scrapped. Therefore, in this study, coffee ground was mixed with diesel oil to develop alternative fuel. The analysis result showed that when coffee ground and diesel oil were mixed at a rate of 30%, 20% and 10%, the diameter of coffee ground droplet was 49.1μm, 45.9μm and 17.5μm respectively.
Weight-based exercise equipment is unreasonable because of its large weight or volume and has limitations in use at home. On top of that, it is not easy to control the weight of domestic muscular exercise devices such as dumbbells and latex bands. This study proposes a new type of exercise equipment that can be used at home by modifying the exercise equipment used in fitness centers. Home training exercise equipment has been optimized by replacing the weight of strength training equipment, which is the core of weight control, with electric motors. For optimal design, process integration and design optimization (PIANO), a commercial PIDO tool, was analyzed in conjunction with DAFUL, a multi-body dynamics analysis program. When formulating the optimal design, the objective function was to minimize the weight, and the shape of the pinwheel and pulley used in exercise equipment was proposed considering the stress of cables as design constraints. As a result of optimization, design proposals were derived while meeting the design requirements and reduced by 5% compared to the initial model. In this work, we have miniaturized the shape of exercise equipment compared to conventional exercise equipment by optimizing its shape.
In this paper, each controller's unique ID and PICO oscilloscope were used to measure the voltage waveform of each CAN communication line, and compare and analyze the serial decoding results. Using the voltage change level of the CAN communication line, it was possible to check whether the CAN-High line and the Low line were disconnected. And it was possible to infer the circuit disconnection point between the controller and the controller only with the unique ID information of each controller. And when the CAN-High circuit was disconnected, the voltage of the high line was measured at the same voltage level as the Low line.
In this study, the effect of thermal grease and heat sink material of cooler on CPU temperature was measured and compared with LinX(v0.9.6) and HWMonitor.When the computer is booted without thermal grease applied, the CPU temperature rises rapidly, and the CPU temperature reaches 100℃ after 60 seconds for aluminum heat sink and 140 seconds for copper heat sink. The CPU temperature is lower as the thermal conductivity coefficient of thermal grease is higher, and the CPU temperature is lower when the thermal conductivity coefficient of the cooler is higher. In addition, when using a thermal grease and a heat sink with a high coefficient of thermal conductivity, the cooler rpm can be lowered, which is considered to be advantageous in terms of system stability and energy saving.
Recently, the demand for reliability verification is increasing while designing and manufacturing molds using injection molding computer aided engineering(CAE). When performing flow analysis verification, a spiral mold is produced and compared with CAE. Because of the spiral shape, we needed a comparative evaluation with the flow distance of products with different forms. So, we compared the weight and flowed length using CAE. Variables are the change in the width of the spiral shape and the shape of the bar and plate. When the width of the spiral shape is 23mm rather than 15mm, the flow distance flows 30∼70mm more, with a maximum difference of 13%. As a result of comparing the spiral shape and the long square shape with the same width, the spiral shape had a flow distance of 60 to 105mm further, and a difference of up to 28% was found. As a result of comparing the plate shape and the spiral shape with a 15mm width product, the spiral shape has a flow distance of 310∼380mm further, and a difference of up to 82% is different.
The role of QR Code robots in smart logistics is great. Cognitive robots, such as logistics robots, were mostly used to adjust routes and search for peripheral sensors, cameras, and recognition signs attached to walls. However, recently, the ease of making QR Codes and the convenience of producing and attaching a lot of information within QR Codes have been raised, and many of these reasons have made QR Codes recognizable as visions and others. In addition, there have been cases in developed countries and Korea that control several of these robots at the same time and operate logistics factories smartly. This representative case is the KIVA robot in Amazon. KIVA robots are only operated inside Amazon, but information about them is not exposed to the outside world, so a variety of similar robots are developed and operated in several places around the world. They are applied in various fields such as education, medical, silver, military, parking, construction, marine, and agriculture, creating a variety of application robots. In this work, we are developing a robot that can recognize its current position, move and control in the directed direction through two-dimensional QR Codes with the same horizontal and vertical sides, and the error is to create a QR Code robot with accuracy to reach within 3mm. This paper focuses a study on the position recognition control using QR Code during the development of QR Code-aware indoor mobility robots.
Most of speakers, the con-paper (con shape) or vibration plate generate the sound by reciprocating motion which is received vibrating signal from voice coil. On the other hand, the vibration speaker that reproduces sound by attaching a vibration head to some materials such as wood, plastic, glass plate, etc. instead of cone paper or vibration plate generates different sound timbres depending on the attached materials with vibration head. so we can hear a variety of timbres than ordinary speakers. In this study, the characteristics of vibration and sound propagation according to various materials attached to the vibration head of the vibration speaker were experimentally investigated and this sound propagation characteristics were compare with woofer speaker and micro speaker. As a result of sound propagation characteristics of vibration speaker, the reproduction ability of low frequency band wes inferior to compared than woofer speaker and micro speaker. This is judged to be due to the material characteristics of glass and wood which are source of the sound propagation. As compare with 1kHz sine tone, the woofer speaker has not generated the high order harmonic component, but the glass plate and wood plate used with the vibration speaker head have generated the high order harmonic component at a level that can not be ignored. According to above results, the vibration speaker will be had a low articulation of sound because the higher volume to generate the high distortion.
In this study, a welding heat source model was presented and verified during fiber laser welding. The multi-layered heat source model is a model that can cover most of existing studies and can be defined with a simple formula. It consists of a total of 12 parameters, and an optimization algorithm was used to find them. As optimization algorithms, adaptive simulated annealing, multi island genetic algorithm, and Hooke-Jeeves technique were applied for comparative analysis. The parameters were found by comparing the temperature distribution when the STS304L was bead on plate welding and the temperature distribution derived through finite element analysis, and all three models were able to derive a model with similar trends. However, there was a deviation between parameters, which was attributed to the many variables. It is expected that a more clear welding heat source model can be derived in subsequent studies by giving a guide to the relational expression and range between variables and increasing the temperature measurement point, which is the target value.
A Catholic school is a school that spreads religious ideology to students by combining religious education with regular school curriculum. But, most Catholic schools do not have a separate liturgical space, mass is performed in multipurpose spaces such as auditoriums, and are exposed to severe acoustic defects due to the very aging facilities and lack of sound performance suitable for the liturgical space. So, in this study, an improvement plan was proposed using sound simulation after identifying acoustic defects through field measurements in the liturgical space of Haeseong High School in Jeonju. Also, hearing experiment using Acoustic Psychological Analysis was conducted to identify changes in subjective responses felt by students as they improved their acoustic performance. The results of study, before and after sound performance improvement sound pressure level (SPL500Hz) was 64.8dB at 66.7dB, the weighted sound level (SPLdB(A)) was 67.9dB(A) at 75.8dB(A), reverberation time (RT500Hz) was 2.04sec at 2.52sec, definition (D50,500Hz) was 40.2% at 33.5%, clarity (C80.500Hz) was –0.8dB at –1.18dB, and RASTI was 57.7% at 49.2% was evaluated. In addition, the amount of improvement in subjective responses before and after sound performance through psycho-acoustic experiment decreased by “Reverberation” -17.0%, “Loudness” -11.3% and increased by “Clear” 21.3%, “Vivid” 21.3%, “Intimacy” 12.4%, “Warmth” 14.3%, “Stability” 19.3%, “Godliness” 18.8%. Therefore, after improving sound performance, Haesung High School's liturgical space improved satisfaction with subjective sound performance felt by students and teachers to ensure sound performance suitable for the liturgical space.
알루미늄합금 6061-T6 판재에 대하여 마찰교반용접과 텅스텐 이너트 가스 용접의 교차 용접부의 미세조직과 기계적 특성에 있어서 용접 순서의 영향을 분석하기 위한 시험편을 성공적으로 제작하였다. FSW-ED 시험편이 다른 조합들보다 가장 좋은 기계적 특성을 나타내었다. 흥미롭게도, TIG-FSW ED 시험편이 FSW-TIG ED 시험편보다 높은 인장강도를 나타내었다. 용접부 경도의 경우, FSW 시편이 TIG-FSW 및 FSW-TIG 시험편보다 높은 값을 나타내었고, TIG-FSW 시험편이 FSW-TIG 시험편보다 높은 값을 나타내었다. FE-SEM을 이용한 인장 파면에 대한 관찰을 통하여, 모든 시험편에서 연성파괴를 나타내는 다양한 크기의 딤플들이 관찰되었다. FSW-TIG 시험편의 파면에서는 용융지(熔融池) 표면 영역에서 기공들이 관찰되는 반면, TIG-FSW 시험편에서는 기공의 형성은 관찰되지 않았다. 경도와 미세조직의 결과를 통해 TIG-FSW 공정이 FSW-TIG 공정보다 높은 인장강도를 확보할 수 있는 공정임을 확인하였다.
With the recent development of autonomous driving technology, many researchers have studied autonomous mobile robots. Accordingly, they are developing diverse mobile robot actuators. However, most actuators mainly use reducers made of chains, belts, multi-stage gears, etc. So the volume and size of the actuators increase, and power transmission efficiency tends to be relatively low. Therefore, this study has proposed the reducer of the mobile robot actuator using a complex planetary gear train with small volume and high power transmission efficiency, and has confirmed the stability of the proposed reducer through finite element analysis.
In this study, numerical analysis is conducted to understand the flow characteristics of the radial impeller with the design parameters such as the blade shape and position using the ANSYS Fluent software. The shape of blade is divided into two types, a backward curved blade and an airfoil forward curved blade. To examine the fundamental flow characteristics near the blades, a rectangular flow field is modeled and analyzed. On the other hand, for the impeller rotation analysis, the simulation is performed by modeling the rotational region separately. As a result, the airfoil forward curved blade shows higher outlet flow rate than the backward curved blade. In addition, as the depth of the impeller and the attachment angle of blade increase, the higher flow rate appears.
These days, our environmental pollution has been greatly threatened by various exhaust emissions from diesel engines for transportation, and there is a tendency that regulations on this are very strengthened. In this study, when biodiesel and water-cooled EGR are simultaneously applied to common rail diesel engines, which occupy most of passenger diesel engines, the characteristics of exhaust smoke and NOx were investigated. As a result of this experiment, as a result of applying less than 10% EGR to 5% biodiesel mixed fuel, it was found that smoke and NOx emissions can be simultaneously reduced.
This study wanted to optimize the radiator tank's deformation assembled on the automotive engine block. Among the experimental planning methods, the Taguchi method was used to find optimal molding conditions to minimize plastic covers' deformation. The four main factors used in the Taguchi method were selected as the main factors: resin temperature, pressure time, coolant temperature, and cooling time. The number of cycles for each factor was divided into five stages, and a total of 25 experiments were conducted. The experiment used the Moldflow program, an injection molding analysis program. The maximum deformation obtained under the existing molding conditions was about 1.318mm. Still, the deformation of the mold applied with the optimal molding conditions obtained using the Taguchi method was approximately 1.273mm, which showed that the maximum deformation was reduced by 3.4% compared to the existing molding conditions.