Structural dynamic system involves random variables conditions such as material property, geometric parameters and applied loads. This uncertainties result from the structural parameter are carefully considered the dynamic structural response in displacement, stress, and natural frequencies. The random vibrational system must be designed to withstand a certain amount of the fluctuation with respect to the uncertainties. Harmonic response of a spring-mass system is mathematically modelled with the probabilistic finite element method using the Monte Carlo simulation. The aim of this paper is to find the optimal lowest frequency for the spring-mass system with random input variables and response parameters to the displacements. The probabilistic design is carried out using ANSYS probabilistic design module in a commercial application software and then the optimal design is sequentially solved. An efficient and practical optimal design evaluation method is proposed for the design of the harmonic system. The numerical results are obtained where the next highest frequency of the system and displacements treated as constraints.
The vibration of wheel is mainly affected by a fault on a wheel contacting with railway when average speed is over 60km/h. When the wheel vibration caused by wheel scratch increase more than a certain criterion, the wheel is shaved to reduce the vibration. This criterion of shaving is determined from the acceleration signal measured from the sensor mounted on the railway. In this study, vibration characteristics of the rolling wheels having a fault is analyzed with experimental approach to verify the acceleration criterion for shaving wheel.
This study describes the effects of polyurethane/loess powder (PU/LP) nanofiber thin films composite produced from electrospun for absorption volatile organic compounds (VOCs) from air. Environmental issue has become a focus with improving people's living quality. The VOCs are one of the factors that affect the environmental safety. So, in order to improve the environment and safety for people, many air cleaning techniques have been investigated. One of the methods is nanofiber filtration technology. In this study, the PU nanofiber thin film has been studied that it has the adsorption of VOCs capacity, and LP nanoparticles (NPs) can be used as an additive to load into PU nanofiber thin film by electrospinning. For studying PU/LP nanofiber thin films's absorption of VOCs capacity, 4 samples (0, 10, 30, and 50 wt% LP with respect to PU) were manufactured, respectively. The results show that PU composite mats containing 30 wt% LP NPs has the highest VOCs absorption capacity, and the adsorption capacity for toluene was the highest compared to benzene and chloroform.
At modern mechanical and automotive industry, the material with light weight proceeds in order to thr environmental issue and high performance. Machine part is fastened with numbers of bolts and nuts. Generally, the metal part at mechanical structure is fastened with bolt and nut through puncturing. But it is difficult to puncture at CFRP with the property of fiber structure like the general metal. In this study, the fracture behavior is investigated by the hole and crack at the plate of the unidirectional CFRP due to ply angle. The thickness of plate is 2 mm. Two laminates with the varied ply angles are layered and eight plies are made. The hole is placed at the center of plate and the cracks with the length of 2 mm are generated on both left and right sides from the hole. The finite element program of ANSYS is carried out in order to analyze the CFRP with fiber layer. As analysis, the maximum reaction force and equivalent stress are investigated due the angle of ply. The reaction force in case of the stacking angle of 90° is shown to be greatest among all specimens.
In order to investigate the low-cycle fatigue behavior of Inconel 718 alloy used for pressure vessels, the strain-controlled fatigue test was performed in the room and high temperatures of 550°C. High temperature test was done using an electric furnace attached on the hydraulic fatigue test system. Tensile strength and elastic modulus of the Inconel 718 alloy at the temperature of 550°C decreased by 8% and 10%, respectively, compared to those at the room temperature. Subjected to the repeated cyclic loading under the strain-control, the material exhibited cyclic softening behavior with decreasing yield strength at both room and high temperatures. The low-cycle fatigue properties determined in this research could be effectively used for the fatigue life estimation of high temperature components made of Inconel 718 alloy.
The study for reducing friction in elevation motion of a large television stand using over 50 inches is performed in this paper. The first study attempted to reduce the frictional force the gas seal lip technology. The second study is for optimized piston structure development by comparison pipe orifice and labyrinth orifice. As the result of the first study, in the gas seal lip technology, the outer-inner diameter of Ø20 × Ø8 in the test result of hollow rod is revealed more proper if the weight of 50 inch television assumed as 30. As the result of the second study, the optimized piston structure development through experiment is fixed orifice specification as labyrinth orifice because pipe orifice is founded slip up/down phenomenon of the Ø0.4~1.0 orifice and the labyrinth orifice is not founded that of the Ø0.4~0.6 orifice both tests on 300 mm intervals.
The water removal characteristics in a PEMFC trapezoidal gas channel are investigated with the volume of fluid (VOF) method. For the case of wall contact angle of 60 degree, liquid water attaches on the top wall and moves toward the exit. In contrast, liquid water moves along the channel side corner or GDL surface irregularly for the higher wall contact angles. The hydrophillic wall contact angle of 60 degrees provides more favorable diffusion of reactants to cathode reaction sites as the GDL surface water coverage ratio approaches zero even if the water flow rate increases.
This transport cask for radioactive materials will be used in the Gijang reactor. It will transport the Ir-192 10,000 Ci or I-131 80 Ci. In this case, the safety evaluation, such as protection of leakage of radioactive material, and radiation shield should be carried out before it is used in the research reactor. The safety regulation requires various tests, such as water spray, free drop, penetration, and water immersion. But this paper considers only the regulations related with thermal-stress and drop impact under the normal conditions because it will be used only in the research reactor building. In this paper, coupled numerical analysis was performed using finite element simulation to investigate the effect of position of tungsten and lead to enhance the safety of transport cask. As a result of simulation, it was verified that the Tungsten-Lead structure is the most durable among the cases considered in the study with a viewpoint of thermal-stress and drop impact.
In this paper, a structural integrity on the test rig with assembly plug to perform intermediate examination is evaluated. Structural analysis results between the test rig with non assembly plug and assembly plug are compared, because the assembly plug has an effect on the flow of the coolant in the test rig. A equivalent stress value on the test rig with assembly plug is increased more than the stress on the test rig with non-assembly plug. A shape optimization of the assembly plug is performed to decrease the stress. Considering a connection with the transport tool, a optimized shape of the assembly plug is presented to minimize the stress on the test rig. Using the optimized assembly plug, the equivalent stress on the test rig with the optimized plug is less than the stress on the test rig with the non-optimized plug.
The heat transfer of Jet impingement is a very effective technique for exchanging high heat fluxs between a heated plate and a fluid. The purpose of current investigation is to carry out the experiment in order to study heat transfer characteristics between a vertical round water jet and a horizontal surface for different flow rates and geometric conditions. The effect of flow rates on heat transfer were investigated. The data obtained in this study are represented in terms of Nusselt number as a function of Reynolds and Peclet numbers. The correlation for the Nusselts number in terms of the Peclet number and was obtained. The proposed correlation predicts the current data of heat transfer very well.
This study investigates the analysis algorithm for developing an optimum hull form with minimum wave resistance by using the practical application of one minus prismatic. In this algorithm the potential-based panel method was adopted to get the wave resistance coefficient as the objective function and SQP method was applied as an optimizer to get the optimum hull form. As an target ship, the series 60(CB=0.6) was taken into account and LBP(length between perpendiculars) of the ship was changed in the direction including a central parallel portion. To verity the validity of this study, the results of the numerical analyses were compared with experimental data.
RTG (Radioisotope Thermoelectric Generator) is a power generation system producing electricity by converting the thermal energy gained from shielding radioisotope. RTG generates power without being charged from outside and as it utilizes radioisotope, RTG mainly serves as an energy source operated for a specific purpose in environment hardly accessible by human. Its design structures vary according to its purpose of operation, thermal source of operation and environment of operation. Since RTG is a power generation system, it should have the highest power efficiency with limited heat source. In this study, heat transfer analysis was implemented to investigate diverse design factors influencing the insulation system of RTG for aerospace use. Design factors considered in this study were silver coating, number of radiation shields inside vacuum insulation and supporter material. As a result, it was found that, depending upon design factors, insulation efficiency increased by 9.3% and finally insulation efficiency of RTG v2.0 was estimated at 84.3%.
Walking method based zero moment position algorithms that can guarantee the stability of the biped walking robot while walking, but it moves the legs for the stability of the walking in a way that is not related to energy conservation. Walking method using ZMP can cause low battery efficiency and load on leg joints. The walking method using the passive walking, which is a natural and efficient method of walking, can reduce the load on the joints of the robot by using the method without using the inertia that occurs when walking and reduced control elements and efficient use of battery. In this paper, a biped robot with an actuator based on the principle of passive dynamic walker mechanism is applied to a passive walking algorithm. In order to solve the problem of stabilization of the posture during walking, the posture was stabilized by using the swing motion of the arm. and the walking movement of the robot was observed using the AHRS sensor applied to the robot .It was confirmed that the posture can be stabilized based on measured values using AHRS.
In this study, The first study attempted to reduce the frictional force the gas seal lip technology. The second study is for specification decision and volume compensation experiment as an apparatus for compensating of the volume of the cylinder is compressed as the volume of piston rod. Consequently, in the gas seal lip technology, the outer-in diameter of ∅20 x ∅8 in the test result of hollow rod is revealed more proper if the weight of 50 inch television assumed as 30 kg. and the result of total consideration in stability problem and performance of volume compensation for specification decision and volume compensation experiment is determined the final speculation of hollow rod ∅8 x ∅4 and riveting system. The spring constant(K) showed an excellent value above the target value of 0.01 to 0.015 N/mm.
A fatigue analysis considering dynamic effects yields a more accurate fatigue life prediction than static fatigue analysis because it considers effects of inertia, flexibility and resonance that occur in the structure up to its natural frequency. However, the dynamic fatigue analysis of bogie frames of the rolling stock is not yet taken into account in the norm EN 13749. Therefore, in order to assure the safety of the rolling stocks, it is important to examine the fatigue analysis of that considering dynamic effects under applied load histories. Moreover, since the bogie frame consists of various welded joints, it is necessary to evaluate fatigue life of that considering welding properties as well as dynamic effects. In this study, under load histories converted from measured acceleration histories, static and dynamic fatigue analysis of the welded bogie frame are performed respectively.
Nondestructive testing is a method of inspecting particular target objects without destructing them in industrial sites. Infrared thermal imaging is one of the nondestructive testing techniques. Among them, lock-in infrared thermography technique is a technique to detect a defect by generating a temperature difference of an object using periodic heat waves. This paper deals with the development of lock-in infrared thermography technique by using numerical analysis model for SM45C metal specimens. As a result, the appropriate frequency was determined for defect detection in SM45C metal specimen by using the established thermal behavior mechanism by periodic heat wave.
In this study, we changed the existing S45C steel shafts applied to the drive shaft for power train of automotive to Al7003-T6 aluminum material. For this purpose, the optimal inner diameter of the aluminium shaft is established. And, analysis of the stresses and vibration characteristics of shafts were analyzed through finite element analysis. The final aluminum drive shaft was evaluated through the static torsional torque test and the frequency test. The Al7003-T6 aluminum drive shaft's weight is 67% comparing from 100% of shaft with existing steel, and with the performance of 3,276 N-m and 236 Hz, it satisfies requirements of the torsional torque of 3,000 N-m and vibration characteristic over 150 Hz required for drive shaft.
In this study, a hot water pipe and a blowing fan were combined for developing zone heating technology for cherry tomato. The concept of this system was that hot air was firstly made by hot water pipe in one layer plastic duct and then a blowing fan made the hot air formed in a duct discharge through a duct hole to a shoot apex or a flower cluster which was temperature-sensitive part of cherry tomato. This system mainly consisted of hot water boiler, thermal tank, heat radiation plastic duct with the function of moving up and down electrically depending on the height of shoot apex. Developed system was applied to the cherry tomato greenhouse located in Jangam Chungcheongnamdo from Dec. 28, 2015 to Feb. 16, 2016 and compared with conventional entire space heating system of cherry tomato greenhouse and looked into cumulative yield for the estimate of growing state and energy saving rate from the conventional consumed energy. The result showed that cumulative yield was 3% higher and consumed energy was 32% lower than those of control greenhouse. The average temperature of shoot apex zone was 0.4~1.1℃ higher and the average relative humidity of shoot apex zone was 2,2~2.3% lower than those of entire space during night time in a shoot apex zone heating greenhouse and the average temperature of shoot apex zone was 0.7~1.4℃ lower and the relative humidity of shoot apex zone was 2.9~8.3% higher than those of entire space during night time in a entire space heating greenhouse.
This study was to develop the products that the Lamp and Ballast are combined for the purpose of easy installation to complement the difficulty of the installation process due to the structure of existing product which the lamp and the Ballast are separated, and that have 8-wavelengths dual-lamp structure such as solar, an advantage of more than 3 times longer life than fluorescent lamp and immediately lighting. This study developed the commercialized products that can prevent the environmental pollution caused by low efficiency and short life time of existing Lamps, and can replace the LED Lighting products which has high Glare index with high price, has also developed the variety of application for industrial, commercial, indoor and military. The applied product are Street lights, Security lights, Flood lights, Indoor lights and lights for fishing. This study solved the optimum distribution and placement of components considering the lightest weight first and thermal interference caused by combination of lamp and ballast by thermal release through applying the double bulkhead design of ballast box, and implemented the high efficiency Eco-friendly products with excellent visibility which can be applied and used for indoor and outdoor both place through high temperature and high humidity test, which has an advantage of 8-wavelengths of same spectrum of solar through the initial trial production.
The brake systems are composed of brake disc, brake pad and caliper and, these three parts play an important role for braking. In this study, heat fluid analysis is conducted for five different ventilated disc models, and two piece brake disc model separated in rotor and housing is used. In this case, each model has a different number of holes and vent shape. The basic heat flux and braking power equations are applied for the heat fluid analysis. The cooling performance with/without the braking operation is also analyzed for given five models where the material properties and boundary conditions are set to be identical. From our analysis results, it is found that the number of disc holes and ventilated pins strongly influences on the cooling performance.