This study is to deal with the cause analysis and improvement ideas for breakage to hydraulic pipes mounted on self-propelled howitzers. Hydraulic piping is one of the core components of a hydraulic system. This is because in the case of devices that use hydraulic pressure as a power source, hydraulic oil is supplied through hydraulic piping to operate. Compared to the main hydraulic assembly, its importance is low, so there are not many studies or failure analysis cases on it. However, contrary to this, cases of hydraulic pipe failure account for a significant proportion of the total number of failures, requiring in-depth technical review. In this study, we aim to analyze the causes of failures in hydraulic pipes of self-propelled guns operated by the military and propose improvement measures. It is expected that this study will aid as a reference for problem solving when similar failures occur in the future.

In order to prevent disconnection of the hydraulic pump EDV cable, this study judged the vibration generated by the pump as the greatest effect on disconnection, and confirmed the vibration effect. And it had a structure that was vulnerable to vibration because of the wire flow space inside the EDV cable connector. After applying the improved adapter, vibration analysis, excitation test, and bending strength test were performed to confirm the effectiveness of design change and improvement. As a result of vibration analysis, the amount of vibration was reduced by about 10 times compared to the existing product, and the strength increased by about 4 times in the bending strength test was confirmed to increase the effect of preventing disconnection due to vibration.

Alluvial beds are intimately associated with electrical properties related to soil types, including clay mineral content, porosity, and water content. The hydraulic property governs water movement and storage in alluvial beds. This study revealed electrical resistivity and hydraulic properties in space and time in relation to the hydrogeological data, groundwater pumping, and rainfall infiltration into the alluvial bed located in Daesan-myeon, Changwon City. An electrical resistivity survey with electrode spacings of 2 and 4m using a dipole-dipole array indicates that electrical resistivity changes in the alluvial bed depend on groundwater pumping and rainfall events. Additionally, rainfall infiltration varies with hydraulic conductivity in the shallow zone of the alluvial bed. The 2 m electrode spacing survey confirms that electrical resistivity values decrease at shallow depths, corresponding with rainfall and increased water content in the soil, indicating rainfall infiltration approximately 1-2 m below the land surface. The 4m electrode spacing survey reveals that hydraulic conductivity (K) values and electrical resistivity (ρ) values display an inverse relationship from the surface to the water table (approximately 9 m) and at deeper levels than the water table. Notably, ρ values are impacted by pumping around the depth of the water table at 9 m. This study suggests that time-lapsed electrical resistivity surveys in space and time could be effective tools for detecting the impact of rainfall and pumping, as well as hydraulic conductivity in shallow alluvial beds.

The main hydraulic pump is a device that generates the hydraulic pressure needed for the K2 tank. It is a pressure-compensated swash plate piston pump that generates the hydraulic power necessary to drive the hydraulic device. Hydraulic pump design changes were made due to frequent failures of the hydraulic pump. As a result of checking the operation records of the hydraulic pump, about 71% of the total engine operation time was in a stationary state where hydraulic pressure was not needed. This has the problem of constantly running when the engine is started, consuming unnecessary endurance time, and generating high noise. In this study, ISG(Idle Stop & Go) was applied to improve operation method. When applying ISG, the pressure can be reduced to about 85% or less in an environment where the operation of the main hydraulic pump is not necessary. So, the lifespan of the main hydraulic pump increases as a result of ISG application, thereby reducing the waste of national funds due to maintenance costs. Also, it is expected to contribute to improving combat power by reducing crew fatigue due to noise reduction.

Hydraulic turbines can convert tidal current energy into electric energy, and the addition of a deflector cover to the turbine can improve the efficiency of the turbine's energy harvesting. The angle of the inlet section and the angle of the outlet section of the deflector will further affect the final energy-acquisition efficiency.A threedimensional numerical model for turbine flow field analysis is established, and the RNG k-ε turbulence model is selected by CFD method, and the best angles of inlet section and outlet section are analysed by the method of sliding mesh to obtain the best angle of inlet section and outlet section separately, and then three groups of angles are selected near the best angle of inlet section and outlet section to make orthogonal comparisons. The energy acquisition efficiency of the turbine is calculated at different angles of the inlet and outlet sections of the deflector, and the turbine streamline distribution, velocity and pressure maps are analysed with and without the deflector.The study shows that the deflector can play the role of convergence of the downstream flow, which can improve the efficiency of the turbine energy acquisition, and the maximum energy acquisition efficiency is at the inlet angle of 29° and the outlet angle of 40 °, and the maximum energy acquisition efficiency can be improved by about 32 percent.

The design of buried underground flexible pipes proposed in domestic standards does not properly reflect changes in ground characteristics. Overseas standards suggest that pipe deflection must be considered while designing them. Therefore, in this study, the structural behavior of underground polyvinyl chloride pipes was investigated through experiments and the finite element analysis. In addition, when the pipe deflection occurred at 3% and 5%, the hydraulic characteristics of the polyvinyl chloride pipe showed a slight difference compared to the round pipe.

In this study, the change in the mold opening stroke of important functional parts according to the 20, 50, 80, and 100% increase in the injection speed of a hydraulic 150 ton hydraulic injection molding machine was studied to verify the accuracy of the injection speed and mold opening stroke and the reproducibility of the standard deviation. The null and alternative hypotheses were confirmed by conducting hypothesis verification according to the experimental condition change using the experimental design method.

Hydraulic cylinders are hydraulic system parts widely used in various industries such as construction machinery, machine tools, robots, automobiles, and automation systems. The maximum capacity of vane pumps used in machine tools is 70bar, but the actual operating pressure is less than 50bar. The allowable pressure of a commercial hydraulic cylinder is 140 - 210 bar, so it is heavy and uneconomical because it uses thick and strong materials. In this paper, we intend to develop a small and lightweight hydraulic cylinder suitable for the allowable pressure of 50bar or less so that it can be used in the hydraulic system field. In order to develop a compact hydraulic cylinder, flow analysis, and structural analysis were conducted under piston forward and backward conditions. The analyzed flow rate value was calculated to be suitable for the operation of the hydraulic cylinder. As a result of comparing the stress calculated under the forward/backward condition of the piston with the yield stress of the material, the safety factor was calculated to be more than 2.5.

In order to analyze the pressure drop of the fluid passing through the hydraulic coupler, a flow model using the Computational Fluid Dynamics (CFD) analysis technique was developed and the fluid flow rate and pressure distribution inside the coupler were analyzed. The analysis model was corrected by comparing the pressure drop measurement using a 6.35mm hydraulic coupler with the ISO reference value and the simulation prediction value. Using the calibrated model, the flow rate and pressure drop of 13 types of hydraulic couplers distributed on the market were analyzed, and their performance was determined by comparing them with ISO reference values. In the case of type A coupler, the pressure drop was generally higher than the ISO reference value, and in the case of type B coupler, the pressure drop was similar to or lower than the ISO reference value. It was confirmed that the complex flow analysis inside the hydraulic coupler could be easily performed through computational fluid dynamics (CFD) modeling, and based on this, problems could be identified and performance could be improved performance.

The waterpower generation of the dam generates electricity by revolving the turbine through a water pipe using the difference of high/low of water, the revolving turbine makes an occurrence a terribly loud noise. Accordingly, in the water turbine generator room located on such hydroelectric generator, since a mutual communication is not establish properly when working, they are suffering many difficulties, and it is real state that such noise damages even to those workers in the office of power plant. Since the most of dam water turbine generator room built in domestic country had used the finishing materials of a huge volume and a high reflexibility, it is carrying more amplifying function with the turbine noise arising when generates the electricity. Therefore, there is not only a difficulty for mutual communication among those workers in the workplace, but also it becomes an obstruction factor for working even to the workers in the adjacent office, and because they are suffering the mental and physical damages, it is actual state that a noise-reduction measure is urgently needed. As a result of the study, on the object with the dam hydraulic turbine dynamo room in which an acoustic defect is being occurring, this Study has conducted the Psycho-Acoustics Experiment about the Delivery of Voice Information using Auralization Technique that can experience the Virtual Acoustic Field. It is considering that such study result could be used usefully for improvement of the Voice Definition when construction the dam hydraulic turbine dynamo room, in the future.

월파된 파도를 이용한 파력발전시스템을 월파수류형 파력발전기 OWEC(Overtopping Wave Energy Converter)라고 한다. OWEC의 성능은 발전 시스템은 특성상 파도의 파고와 주기의 영향을 받는다. 파도는 해양에 따라 파고, 주기, 파도 방향 등의 특성이 다르고 이러 한 파도의 다양한 특성 때문에 OWEC는 안정적인 전력을 생산하기 어렵다. 따라서 각 바다의 특성에 따른 OWEC의 적절한 형상에 관한 연구가 필요하다. 본 연구에서는 SPH(Smoothed Particle Hydrodynamics) 입자법을 사용하여 OWEC의 램프 설계가 hydraulic efficiency에 미치 는 영향을 확인했다. 총 10개의 모델을 설계하였으며, 선택된 매개변수에 따라 램프의 설계 파라미터를 선택하고 사면의 형상을 변경하여 시뮬레이션을 수행하였다. 해석 결과로부터 구한 유량을 기초로 hydraulic efficiency를 산출하였다. 계산된 hydraulic efficiency를 바탕으로 각 변수가 사면의 형상에 따른 월파 성능에 미치는 영향을 확인하였다. 본 연구에서는 특정 해역에 따른 OWEC 램프의 적절한 형상에 대한 방향을 제시하였다.

해양플랜트는 발주처와 선급에서 요구하는 다양한 항목들을 설계할 시에 반영하여야 한다. 특히, 해양구조물에 탑재되는 Topside Module의 경우 육상플랜트와는 다르게 공간적 제약이 크고 구조물의 움직임과 같은 해상 환경조건 및 안전과 관련된 요구사항들이 많아 그 설계 과정이 매우 까다롭다. 본 연구에서는 Topside Module에 들어가는 주요장비 중 하나인 HPU(Hydraulic Power Unit) 구조물에 작용하는 하중을 DNVGL 규칙에 따라 계산하고, 각 하중조건에 따른 구조안전성 평가를 진행하였고 개발된 제품의 구조 신뢰성을 향상하고자 하였다. 구조해석은 범용프로그램인 MSC 소프트웨어를 사용하였고, 총 5가지 하중 조건으로 구조해석을 진행하여 다양한 움직임에 대한 안전성을 검토하였다. 그 결과 선미 방향 Pitching 상태(Load Case 5)에서 최대 응력이 발생하였고, 응력 수준은 허용응력의 약 85 % 수준이고, 최대변위는 허용치의 약 5 % 수준으로 구조안전성이 확인되었으며 부재 간 간섭은 발생하지 않았다.

Hydro-electric power is a method of generating electricity from the rotational force of turbine blades by using the potential energy of a river or reservoir water. Recently, the necessity of small hydropower development is expanding due to the development and support of renewable energy, and because of the difficulty and environmental problems of huge dams. The purpose of this paper is to deal with a method of increasing the efficiency of small water turbine that can be adopt in low head condition. In order to improve the turbine efficiency, channel shape is optimized in order to minimize head loss using computational fluid dynamics. The angle values for the contraction and enlargement part of the channel where the turbine is located are found from the analyses. Additionally, three-dimensional analysis is applied to the optimized channel shape in order to confirm the optimized pipe.