• Structural Engineering and Mechanics
• /
• v.86 no.1
• /
• pp.139-156
• /
• 2023

The reinforced concrete lining in the hydraulic pressure tunnel tends to crack during the water-filling process. The lining will be detached from the surrounding rock due to the inner water exosmosis along concrete cracks. From the previous research achievements, the cohesive element is widely adopted to simulate the concrete crack but rarely adopted to simulate the lining-rock interface. In this study, the zero-thickness cohesive element with hydro-mechanical coupling property is not only employed to simulate the traditional concrete crack, but also innovatively introduced to simulate the lining-rock interface. Combined with the indirect-coupled method, the hydro-mechanical coupling algorithm of the reinforced concrete lining in hydraulic pressure tunnels is proposed and implemented in the finite element code ABAQUS. The calculated results reveal the cracking mechanism of the reinforced concrete lining, and match well with the observed engineering phenomenon.

• Journal of Drive and Control
• /
• v.11 no.3
• /
• pp.31-40
• /
• 2014

This paper proposes a multi absorbing wave energy converter design, in which a hydrostatic transmission is used to transfer wave energy to electric energy. The most important feature of this system is its combination of the pressure coupling principle with the use of a hydraulic accumulator to eliminate the effects of wave power fluctuation; this maintains a constant speed of the hydraulic motor. Tilt motion of a floating buoy was employed as the power take-off mechanism. Furthermore, a PID controller was designed to carry out the speed control of the hydraulic motor. The design offers some advantages such as extending the life of the hydraulic components, increasing the amount of energy harvested, and stabilizing the output speed.

• Geomechanics and Engineering
• /
• v.16 no.1
• /
• pp.59-69
• /
• 2018

This study focused on the mechanical and hydraulic characteristics of underwater tunnels based on Mohr-Coulomb (M-C), Hoek-Brown (H-B) and generalized H-B failure criteria. An improved approach for calculating stress, displacement and plastic radius of the circular tunnel considering hydraulic-mechanical coupling was developed. The innovation of this study was that the radius-incremental-approach was reconstructed (i.e., the whole plastic zone is divided into a finite number of concentric annuli by radius), stress and displacement of each annulus were determined in terms of numerical method and Terzaghi's effective stress principle. The validation of the proposed approach was conducted by comparing with the results in Brown and Bray (1982) and Park and Kim (2006). In addition, the Rp-pin curve (plastic radius-internal supporting pressure curve) was obtained using the numerical iterative method, and the plastic radius of the deep-buried tunnel could be obtained by interpolation method in terms of the known value of internal supporting pressure pin. Combining with the theories in Carranza and Fairhurst (2000), the improved technique for assessing the reliability of the tunnel support was proposed.

• Nuclear Engineering and Technology
• /
• v.53 no.5
• /
• pp.1540-1555
• /
• 2021

The plate-type fuel assembly adopted in nuclear research reactor suffers from complicated effect induced by non-uniform irradiation, which might affect its stress conditions, mechanical behavior and thermal-hydraulic performance. A reliable numerical method is of great importance to reveal the complex evolution of mechanical deformation, flow redistribution and temperature field for the plate-type fuel assembly under non-uniform irradiation. This paper is the first part of a two-part study developing the numerical methodology for the thermal-fluid-structure coupling behaviors of plate-type fuel assembly under irradiation. In this paper, the thermal-fluid-structure coupling methodology has been developed for plate-type fuel assembly under non-uniform irradiation condition by exchanging thermal-hydraulic and mechanical deformation parameters between Finite Element Model (FEM) software and Computational Fluid Dynamic (CFD) software with Mesh-based parallel Code Coupling Interface (MpCCI), which has been validated with experimental results. Based on the established methodology, the effects of non-uniform irradiation and fluid were discussed, which demonstrated that the maximum mechanical deformation with irradiation was dozens of times larger than that without irradiation and the hydraulic load on fuel plates due to differential pressure played a dominant role in the mechanical deformation.

• Journal of the Korean Society of Safety
• /
• v.31 no.1
• /
• pp.33-40
• /
• 2016

Coupling systems under train's collision should take the impact by absorbing the impact energy caused from the collision, so the systems are very important parts for the safety of the trains. However, it is not easy to evaluate the performance of the system because it requires a huge testing facility, which is able to control the impact and to handle many safety issues. In this paper, test results are provided, which are obtained from collision tests of a single train having a coupling system in the front, and the results are analyzed in order to understand the characteristics and the dynamic behaviors of energy absorbing materials in the coupling system, such as a hydraulic buffer, and two rubber buffers. The results show that the force of each component could be empirically described by the compression displacement and velocity. The analyzed results will be applied to simulation models, and advanced studies wouuld be available if the simulation models are well validated with the test results.

• Transactions of the Korean Society of Automotive Engineers
• /
• v.18 no.4
• /
• pp.107-114
• /
• 2010

Coupling systems for trains need more complicated buffer equipments than existing systems because the recent tendency of the regulations enforces trains to be safe for collisions even when the driving speed is higher than before. Using hydraulic buffer is an effective way to satisfy the requirement while it causes the increase of the cost for the coupling system. In this study, we introduce the methodology to build a simulation model for the hydraulic buffer, which could be installed into the coupling systems. In the simulation model of the hydraulic buffer, the reacting force is determined by both buffer stroke and speed whereas the elastic buffer model is designed by using only the buffer stroke in other studies. The simulation results with the advanced hydraulic buffer model shows that the simulating results can be close the real experimental results around 10%, and, if we considers friction forces, the simulation calculates the maximum force within 10% comparing to the experimental.

• Nuclear Engineering and Technology
• /
• v.53 no.5
• /
• pp.1556-1568
• /
• 2021

The plate-type fuel assembly adopted in nuclear research reactor suffers from complicated effect induced by non-uniform irradiation, which might affect stress conditions, mechanical behaviors and thermal-hydraulic performance of the fuel assembly. This paper is the Part II work of a two-part study devoted to analyzing the complex unique mechanical deformation and thermal-hydraulic characteristics for the typical plate-type fuel assembly under irradiation effect, which is on the basis of developed and verified numerical thermal-fluid-structure coupling methodology under irradiation in Part I of this work. The mechanical deformation, thermal-hydraulic performance and Mises stress have been analyzed for the typical plate-type fuel assembly consisting of support plates under non-uniform irradiation. It was interesting to observe that: the plate-type fuel assembly including the fuel plates and support plates tended to bend towards the location with maximum fission rate; the hot spots in the fuel foil appeared at the location with maximum thickness increment; the maximum Mises stress of fuel foil was located at the adjacent location with the maximum plate thickness increment et al.

• Tunnel and Underground Space
• /
• v.8 no.3
• /
• pp.184-193
• /
• 1998

In order to dispose radioactive wastes safely, it is needed to understand the mechanical, thermal, fluid behavior of rockmass and physico-chemical interactions between rockmass and water. Also, the knowledge about mechanical and hydraulic properties of rocks is required to predict and to model many conditions of geological structure, underground in-situ stress, folding, hot water interaction, intrusion of magma, plate tectonics etc. This study is based on researches about rock mechanics issues associated with a waste disposal in deep rockmass. This paper includes the mechanical and hydraulic behavior of rocks in varying temperature conditions, thermo-hydro-mechanical coupling analysis in rock mass and deformation behavior of discontinuous rocks. The mechanical properties were measured with Interaken rock mechanics testing systems and hydraulic properties were measured with transient pulse permeability measuring systems. In all results, rock properties were sensitive to temperature variation.

• Tunnel and Underground Space
• /
• v.23 no.6
• /
• pp.470-479
• /
• 2013

Hydraulic fracturing is used as a method for promoting the fluid flow in the rock and, in the energy field such as geothermal development and the development of sales gas, many studies has been actively conducted. In many cases, hydraulic fracturing is not performed in isotropic rock and especially in the case of sedimentary rocks, hydraulic fracturing is conducted in the transverse isotropic rock. The direction of the crack growth on hydraulic fracturing does not necessarily coincides with the direction of maximum principal stress in the transverse isotropic rock. Therefore, in this study, bonded particle model with hydro-mechanical coupling analysis was adopted for analyzing the characteristics of hydraulic fracturing in transverse isotropic rock. In addition, experiments of hydraulic fracturing were conducted in laboratory-scale to verify the validity of numerical analysis. In this study, the crack growth and crack patterns showed significant differences depending on the viscosity of injection fluid, the angle of bedding plane and the influence of anisotropy. In the case of transverse isotropic model, the shear crack growth due to hydraulic fracturing appeared prominently.

• Journal of the Korean Society of Manufacturing Process Engineers
• /
• v.21 no.5
• /
• pp.84-90
• /
• 2022

Hydraulic coupling systems play an important role in easily connecting or disconnecting pipes or hoses that transmit high-pressure fluids without hydraulic oil leakage in hydraulic power transmission equipment. A flat-face hydraulic quick coupler is a recently developed product that can reduce environmental pollution by minimizing hydraulic oil leakage during connection and disconnection. In this study, the influence of the shape of the inner ring of a 3/8" flat-face hydraulic quick coupler on its internal flow characteristics was analyzed and evaluated by numerical analysis based on computational fluid dynamics. The flow velocity distribution, temperature distribution, and optimal shape design of the inner ring were obtained by comparing the results of the flow characteristics, such as the pressure drop.