• Geomechanics and Engineering
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• v.22 no.4
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• pp.329-337
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• 2020

Polyacrylamide (PAM) possesses high water absorption capacity and a unique pH-dependent behavior that confer large potential to enhance the engineering performance of clays. In this study, calcium bentonite was treated with a nonionic PAM. Flexible-wall permeability test and the consolidation test were performed at different pH values to evaluate the effects of PAM treatment on the hydraulic and consolidation properties. Test results demonstrate that index properties are affected by the adsorbed PAM on clay surface: a decrease in specific gravity, a decrease in net zeta potential, and an increase in liquid limit are observed due to the PAM treatment. At a given pH, the compressibility of the treated clay is greater than that of the untreated clay. However, the compression indices of untreated and treated clays can be expressed as a single function of the initial void ratio, regardless of pH. Hydraulic conductivity is reduced by PAM treatment about 5 times at both neutral and alkaline pH conditions under similar void ratios, because of the reduction in size of the water flow channel by PAM expansion. However, at acidic pH, the hydraulic conductivity of the treated clay is slightly higher than the untreated clay. This reflects that the treated bentonite with PAM can be beneficially used in barrier system for highly alkaline residues.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.25 no.5
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• pp.850-856
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• 2001

Even though the hydraulic servo system has been widely used in industrial and military equipments since it has a lot of advantages, it is not easy to design controller due to the high nonlinearities and the parametric uncertainties. The dynamic behavior of the real process in the hydraulic servo system differs from that described by its model because the model is linearized. Another reason of the difference is caused by the variety of parameters, since the system parameters of the dynamic equation are affected by the operating conditions such as temperature and pressure. In this study, the designing process of the MRNC with a PID compensator is introduced and applied to the load sensing hydraulic servo system. The results show that the designed controller guarantees the robust control performance despite of both the nonlinearities and the parametric uncertainties.

• Transactions of The Korea Fluid Power Systems Society
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• v.6 no.1
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• pp.10-16
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• 2009

Automatic power transmission systems consisted of a torque converter and several planetary gear sets, clutches and brakes are controlled by a hydraulic shift control circuit and an electronic transmission control unit. The hydraulic circuit serves for the operation of the torque converter and lubrication oil supply of the transmission system as well as for the actuation of clutches for the automatic gear shift. The complicated hydraulic control circuit constructed by many spools, solenoids, orifices and flow passages are integrated into one small valve block and it is powered by one hydraulic pump. In this paper, a test equipment was developed to measure the oil consumption of each component at various wide operating conditions. Test data about 730 sets acquired from five test items are analyzed and discussed on the oil capacity of the circuit.

• Journal of Drive and Control
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• v.15 no.2
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• pp.22-31
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• 2018

This study deals with verifying the design feasibility, of an independently driving hydraulic system for disaster response purposes, through an analytical approach. The development target is a system in which four traveling motors are driven independently, and must be easy to operate even under conditions in which different loads are applied to the traveling motors. In order to be suitable for complex work, the hydraulic system was designed using the main control valve with a pressure compensation function. If we can develop an analytical model that reflects the specifications and functions of the parts through the analysis program, we can verify the validity of the design before we make the prototype. The purpose of this study therefore, is to verify the feasibility of designing an independent drive hydraulic system through the development of an analysis model from the viewpoint of complex work. The analysis program uses Simulation X.

• Journal of the Korean Society for Precision Engineering
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• v.33 no.9
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• pp.723-730
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• 2016

This paper presents a cable-driven hydraulic actuator named Cable Rod Hydraulic Actuator (CRHA). The cable actuating system is attractive for designing a compact joint in robotic applications since it can be installed remotely from the joint. Recently, cable rods have been used in pneumatic area for inertia reduction. However, designing cable rods in hydraulics is challenging because it is difficult to achieve flexibility and endurance simultaneously under high pressure conditions. In this paper, the cable rod, which consists of a cable and jacket, is proposed to meet both requirements. To design the CRHA, we determined the design parameters, such as cylinder size, and selected the cable rod's material by friction and leakage test. Finally, comparisons experiments about step and frequency responses with conventional hydraulic actuators were performed to assess feasibility for robotic joints, and the results show that the proposed system has good bandwidth and fast response as robotic joints.

• Geomechanics and Engineering
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• v.25 no.1
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• pp.31-40
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• 2021

Injection grouting is one of the most common ground improvement practice to increase the strength and reduce the hydraulic conductivity of soils. Owing to the environmental concerns of conventional grout materials, such as cement-based or silicate-based materials, bio-inspired biogeotechnical approaches are considered to be new sustainable and environmentally friendly ground improvement methods. Biopolymers, which are excretory products from living organisms, have been shown to significantly reduce the hydraulic conductivity via pore-clogging and increase the strength of soils. To study the practical application of biopolymers for seepage and ground water control, in this study, we explored the injection capabilities of biopolymer-based grout materials in both linear aperture and particulate media (i.e., sand and glassbeads) considering different injection pressures, biopolymer concentrations, and flow channel geometries. The hydraulic conductivity control of a biopolymer-based grout material was evaluated after injection into sandy soil under confined boundary conditions. The results showed that the performance of xanthan gum injection was mainly affected by the injection pressure and pore geometry (e.g., porosity) inside the soil. Additionally, with an increase in the xanthan gum concentration, the injection efficiency diminished while the hydraulic conductivity reduction efficiency enhanced significantly. The results of this study provide the potential capabilities of injection grouting to be performed with biopolymer-based materials for field application.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.19 no.10
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• pp.31-35
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• 2020

Hydraulic winches for transportation and logistics in the shipbuilding and marine plant fields require multi-stage planetary gear modules with high gear ratios. Due to environmental conditions in the ship, durability is crucial. Further, we are currently relying on foreign products. The development of domestic technology will reduce cost, save time, and improve the export market. Thus, we developed a multi-stage planetary gear module for a hydraulic winch and evaluated its performance through several tests of the hydraulic brake torque, maximum torque, and load endurance.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.43 no.6
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• pp.749-762
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• 2023

A depth-integrated model with an approximate Riemann solver for flux computation of the shallow water equations was applied to hydraulic jump experiments. Due to the hydraulic jump, different flow regimes occur simultaneously in a single channel. Therefore, the Weisbach resistance coefficient, which reflects flow conditions rather than the Manning roughness coefficient that is independent of depth or flow, has been employed for flow resistance. Simulation results were in good agreement with experimental results, and it was confirmed that Manning coefficients converted from Weisbach coefficients were appropriately set in the supercritical and subcritical flow reaches, respectively. Limitations of the shallow water equations that rely on hydrostatic assumptions have been revealed in comparison with hydraulic jump experiments, highlighting the need for the introduction of a non-hydrostatic shallow-water flow model.

• Journal of Biosystems Engineering
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• v.34 no.5
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• pp.331-341
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• 2009

A double-end rod hydraulic cylinder is widely used with a steering valve for the steering control system in large tractors. For the development of automatic steering controller, the feasibility of using a proportional control valve replacing the conventional manual steering valve to control the position of hydraulic steering cylinder was investigated in terms of the max. overshoot, the steady-state error and the rise time. A simulation model for the electrohydraulic steering system with load using AMESim package was developed to be valid so that the proper control algorithm could be chosen through the computer simulation. It could be concluded that the P-control algorithm was sufficient to control the electrohydraulic steering system, where the control frequency should be no greater than 20 Hz at the P-gain of 5. In particular, the performance of the developed steering controller was satisfactory even at the conditions of varying flow rates and loads.

• Journal of The Korean Society of Agricultural Engineers
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• v.54 no.6
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• pp.101-109
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• 2012

Silt curtains are constructed for minimizing pollution of sediment dispersion in water bodies. In spite of wide uses of the silt curtains, there are few studies for analyzing the effectiveness of them with respect to their dimension and hydraulic characteristics. Currently, the market of silt curtains does not provide the various dimension of them due to the limit of information regarding its effectiveness on reducing sediment pollution. In this study, a series of experiments were conducted to investigate hydraulic characteristics around the silt curtains under the different flow conditions. For this study, a silt curtain was fabricated and an open channel with 30cm of width and 40cm of depth was used. The results indicated that the silt curtain was not effective in preventing dispersion at flow velocities over 0.5m/s in real conditions. Based on the experimental results, it is required that approaching velocity should be minimized and the weight of bottom be increased in order to reduce deformation. The results of this study will provide information required to design appropriate dimension of silt curtains in various water environment such as velocity and water depths.