• Korean Journal of Metals and Materials
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• v.49 no.7
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• pp.541-548
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• 2011

Thermomechanical fatigue (TMF) behavior of heat resistant austenitic stainless steel was evaluated in the temperature range from 100$^{\circ}C$ to peak temperatures of 600 to 800$^{\circ}C$; The fatigue lives under TMF conditions were plotted against the plastic strain range and the dissipated energy per cycle. In the expression of the inelastic strain range versus fatigue life, the TMF data obtained at different temperature ranges were located close to a single line with a small deviation; however, when the dissipated energy per cycle, calculated from the area of the stress-strain hysteresis loops at the half of the fatigue life, was plotted against the fatigue life, the data showed greater scattering than the TMF life against the inelastic strain range. A noticeable stress relaxation in the stress-strain hysteresis curve took place at the peak temperatures higher than 700$^{\circ}C$, but all specimens in this study exhibited cyclic hardening behavior with TMF cycles. Recrystallization occurred during the TMF cycle concurrent with the formation of fine subgrains in the recrystallized region, which is considered to cause the cyclic hardening of the steel.

• Journal of The Korean Astronomical Society
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• v.37 no.5
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• pp.477-482
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• 2004

Shock waves form in the intergalactic space as an ubiquitous consequence of cosmic structure formation. Using N-body/hydrodynamic simulation data of a ACDM universe, we examined the properties of cosmological shock waves including their morphological distribution. Adopting a diffusive shock acceleration model, we then calculated the amount of cosmic ray energy as well as that of gas thermal energy dissipated at the shocks. Finally, the dynamical consequence of those cosmic rays on cluster properties is discussed.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1995.10a
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• pp.747-750
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• 1995

As railway trains run faster high performance braking system are necessary because more energy needs to be dissipated due to increased kinetic energy. In this work a portable computer based prediction system for emergency braking distance has been developed. The algorithm for the system is based on braking theory and empirical results of actual braking test. The computer is connected to the sensors to measure the velocity and the braking pressure in real train. It is expected that this system will be utilized to predict emergency braking distance during actual operation of the train

• Journal of the Computational Structural Engineering Institute of Korea
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• v.33 no.1
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• pp.25-33
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• 2020

In this study, parametric analyses are performed using the coupled Eulerian-Lagrangian scheme for the collision behaviors of a vessel and an underwater slope that constitutes part of an artificial protective island. The vessel parameters considered in the analysis are bow angle, stem angle, draft, and impact velocity. The gradient of the slope, the friction coefficient between the bow and the slope, and soil strength are considered as parameters of the slope. For each parameter, the dissipated collision energy and the collision force are estimated from the behavior of the vessel, and the energy dissipation mechanism is identified in terms of the ground deformation. The collision force is assumed as an exponential function, and the effects of the parameters are estimated. As a result, only two parameters, the gradient of the slope and the friction coefficient between the vessel and the soil, can affect the exponential coefficient of the function. The dissipated energy by the soil can thus be estimated adequately. The relationship between the volume of the soil pushed out by the bow and the dissipated collision energy is estimated as a linear function. This relationship is independent of the magnitude of the collision energy, and affected more by the friction coefficient and the soil strength than by the parameters of the vessel.

• Structural Engineering and Mechanics
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• v.31 no.1
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• pp.93-112
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• 2009

In this study seismic analyses of steel structures were carried out to examine the effect of ground motion characteristics and structural properties on energy demands using 100 earthquake ground motions recorded in different soil conditions, and the results were compared with those of previous works. Analysis results show that ductility ratios and the site conditions have significant influence on input energy. The ratio of hysteretic to input energy is considerably influenced by the ductility ratio and the strong motion duration. It is also observed that as the predominant periods of the input energy spectra are significantly larger than those of acceleration response spectra used in the strength design, the strength demand on a structure designed based on energy should be checked especially in short period structures. For that reason framed structures with buckling-restrained-braces (BRBs) were designed in such a way that all the input energy was dissipated by the hysteretic energy of the BRBs, and the results were compared with those designed by conventional strength-based design procedure.

• Steel and Composite Structures
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• v.6 no.6
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• pp.479-491
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• 2006

Structures in seismic regions are designed to dissipate seismic energy input through inelastic deformations. Structural or component failure occurs when the hysteretic energy demand for a structure or component subject to an earthquake ground motion (EQGM) exceeds its hysteretic energy dissipation capacity. This paper presents a study on identifying the hysteretic energy demand and distribution throughout the height of regular steel moment resisting frames (SMRFs) subject to severe EQGMs. For this purpose, non-linear dynamic time history (NDTH) analyses were carried out on regular low-, medium-, and high-rise steel SMRFs. An ensemble of ninety EQGMs recorded on different soil types was used in the study. The results show that the hysteretic energy demand decreases from the bottom stories to the upper stories and for high-rise structures, most of the hysteretic energy is dissipated by the bottom stories. The decrease is quite significant, especially, for medium- and high-rise structures.

• Advances in concrete construction
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• v.13 no.6
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• pp.423-431
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• 2022

Although the influence of moisture content on the mechanical properties of concrete has been studied for a long time, research related to its influence on the damping and energy dissipation property of concrete structure is still very limited. In this paper, the relationship between damping property and moisture content of concrete using cyclic uniaxial compression is firstly presented, and the mechanism of the influence of moisture content on concrete damping and energy dissipation capacity is analyzed. Based on the experimental research, moisture-related damping and energy dissipation model is proposed. Results show that the dissipated energy of concrete and loss factor increase as the moisture content increasing. The energy dissipation coefficient reflecting the influence of stress level of concrete under cyclic load, decreases first and then increases as the moisture content increasing. The mechanism of moisture-related energy dissipation behavior can be divided into the reactive force of water, the development of the internal micro cracks and the pore water pressure. Finally, the proposed moisture-related damping and energy dissipation model are verified.

• Proceedings of the Earthquake Engineering Society of Korea Conference
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• 2003.03a
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• pp.275-285
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• 2003

Pinching is an important property of reinforced concrete member which characterizes its cyclic behavior. In the present study, numerical studies were performed to investigate the characteristics and mechanisms of pinching behavior and the energy dissipation capacity of flexure-dominated reinforced concrete members. By analyzing existing experimental studies and numerical results, it was found that energy dissipation capacity of a member is directly related to energy dissipated by re-bars rather than concrete that is a brittle material, and that it is not related to magnitude of axial compressive force applied to the member. Therefore, for a member with specific arrangement and amount of re-bars, the energy dissipation capacity remains uniform regardless of the flexural strength that is changed by the magnitude of axial force applied. Due to the uniformness of energy dissipation capacity pinching appears in axial compression member. The flexural pinching that is not related to shear force becomes conspicuous as the flexural strength increases relatively to the uniform energy dissipation capacity. Based on the findings, a practical method for estimating energy dissipation capacity and damping modification factor was developed and verified with existing experiments.

• International Journal of Computer Science & Network Security
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• v.21 no.9
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• pp.230-238
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• 2021

A sensor network is made up of many sensors deployed in different areas to be monitored. They communicate with each other through a wireless medium. The routing of collected data in the wireless network consumes most of the energy of the network. In the literature, several routing approaches have been proposed to conserve the energy at the sensor level and overcome the challenges inherent in its limitations. In this paper, we propose a new low-energy routing protocol for power grids sensors based on an unsupervised clustering approach. Our protocol equitably harnesses the energy of the selected cluster-head nodes and conserves the energy dissipated when routing the captured data at the Base Station (BS). The simulation results show that our protocol reduces the energy dissipation and prolongs the network lifetime.

• Computers and Concrete
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• v.22 no.4
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• pp.395-405
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• 2018

In this paper, the performance of post-installed adhesive bonded anchor embedded in concrete is assessed using numerical simulations. This study aims at studying the influence of parameters on the performance of a chemically bonded anchorage system. Non-linear finite element modelling and simulations are carried out by properly using the material properties and phenomenon. Materials parameters such as characteristic length, fracture energy, damage criteria, tension retention and crack width of concrete and interface characteristics are carefully assigned so as to obtain a most realistic behaviour of the chemical anchor system. The peak strength of two different anchor systems obtained from present numerical studies is validated against experimental results. Furthermore, validated numerical models are used to study the load transferring mechanism and damage progression characteristics of various anchors systems where strength of concrete, strength of epoxy, and geometry and disposition of anchors are the parameters. The process of development of strain in concrete adjacent to the anchor and energy dissipated during the course of damage progression are analysed. Results show that the performance of the considered anchorage system is, though a combined effect of material and geometric parameters, but a clear distinction could be made on the parameters to achieve a desired performance based on strength, slip, strain development or dissipated energy. Inspite the increase in anchor capacity with increase in concrete strength, it brings some undesirable performance as well. Furthermore, the pullout capacity of the chemical anchor system increases with a decrease in disparity among the strength of concrete and epoxy.