• Structural Engineering and Mechanics
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• v.65 no.5
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• pp.557-572
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• 2018

The academic research works about liquid storage tanks are reviewed for the purpose of providing valuable reference to the engineering practice on their aseismic design. A summary of the performance of tanks during past earthquakes is described in this paper. Next, the seismic response of tanks under unidirectional earthquake is reported, supplemented with the dynamic response under multidirectional motions. Then, researches on the influence of soil-structure interaction are brought out to help modify the seismic design approach of tanks in different areas with variable properties of soils. Afterwards, base isolation systems are reported to demonstrate their effectiveness for the earthquake-resistant design of liquid storage tanks. Further, researches about the liquid-structure interaction are reviewed with description of simplified models and numerical analytical methods, some of which consider the elastic effect of tank walls. Moreover, the liquid sloshing phenomenon on the hydrodynamic behaviors of tanks is presented by various algorithms including grid-based and meshfree method. And then the impact of baffles in changing the dynamic characteristics of the liquid-structure system is raised, which shows the energy dissipation by the vortex motion of liquid. In addition, uplifting effect is given to enhance the understanding on the capacity of unanchored tanks and some assessment of their development. At last, the concluding remarks and the aspects of extended research in the field of liquid storage tanks under seismic loads are provided, emphasizing the thermal stress analysis, the replaceable system for base isolation, the liquid-solid interaction and dynamic responses with stochastic excitations.

• Advances in Computational Design
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• v.2 no.2
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• pp.107-119
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• 2017

The Micro circular diaphragm (MCD) is the mechanical actuator part used in the micro electro-mechanical sensors (MEMS) that combine electrical and mechanical components. These actuators are working under harsh mechanical and thermal conditions, so it is very important to study the mechanical and thermal behaviors of these actuators, in order to do with its function successfully. The objective of this paper is to determine the thermo-mechanical behavior of MCD by developing the traditional bulge test technique to achieve the aims of this work. The specimen is first pre-stressed to ensure that is no initial deflection before applied the loads on diaphragm and then clamped between two plates, a differential pressure (P) and temperature ($T_b$) is leading to a deformation of the MCD. Analytical formulation of developed bulge test technique for MCD thermo-mechanical characterization was established with taking in-to account effect of the residual strength from pre-stressed loading. These makes the plane-strain bulge test ideal for studying the mechanical and thermal behavior of diaphragm in both the elastic and plastic regimes. The differential specimen thickness due to bulge effect to describe the mechanical behavior, and the temperature effect on the MCD material properties to study the thermal behavior under deformation were discussed. A finite element model (FEM) can be extended to apply for investigating the reliability of the proposed bulge test of MCD and compare between the FEM results and another one from analytical calculus. The results show that, the good convergence between the finite element model and analytical model.

• Journal of Ocean Engineering and Technology
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• v.6 no.1
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• pp.78-86
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• 1992

The creep behaviors of 1%Cr-Mo-V and 12%Cr steam turbine rotor steels under static or cyclic load were examined at 600 and $700^{\circ}C$. The relationship between these two kinds of phenomena was studied and the experimental results were summarized as follows: 1) It is confirmed that the cyclic creep strain dependent on time is more available for creep, behavior analysis according to frequency change than that dependent on number of cycles, and the static creep, the special case of cyclic creep with stress ratio of 1 can be also more effectively analyzed by time-dependence. 2) The steady cyclic creep rate vs. the steady static creep rate, increases according to the increase of stress ratio, and this phenomena may occur on occasion of the decrease of the internal stress. 3) The initial strain affects on all the creep properties of the transient region, the steady state region and the rupture time in cyclic creep as well as static creep, and the quantitative relationships among them exist.

• Transactions of the Korean Society of Mechanical Engineers
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• v.16 no.7
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• pp.1341-1350
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• 1992

This paper addresses the practical problem of finding a useful strain energy function of the incompressible rubberlike materials. It examines methods by which the form of the functions are determined and shows how the selection of experimental data influences the resulting form of the functions. From this information, an optimal choice of the form of energy functions becomes possible. Phenomenological theories used in this paper are limited to elastic, incompressible material models. Due to the nature of the phenomenological methods, these theories are accurate only for the materials treated. However, they serve as a starting basis for the study of more complicated material behaviors.

• Journal of Power System Engineering
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• v.13 no.4
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• pp.43-48
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• 2009

The purpose of this study is to show how to eliminate the noises and to obtain the data related with the relationship between AE signal characteristics and mechanical behaviors for the pressure vessel steel. Various kinds of noises are introduced into the AE data in the course of experiments. Accordingly, real AE data have to be obtained after tests. AE test was carried out under four point bending load. Among AE signals, counts and signal strength are used to find out the differences of AE characteristics between the basemetal and weldment. After tests, this paper shows the procedures of filtering the noises against basemetal of the pressure vessel steel to obtain the real data around crack tip. Relationships between plastic zone size and cumulative AE counts are shown also. AE signals were absent within an elastic region, regardless of the specimens. Most of AE signals are produced in the process of plastic deformation. The deformation and fracture modes of basemetal and weldment are quiet different.

• Journal of Ocean Engineering and Technology
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• v.8 no.1
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• pp.33-40
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• 1994

Welding of structure produces welding residual stresses which influence buckling strength, brittle fracture strength and cold crack on the weld parts. Therefore, it is very important to accurately analyze the residual stress before welding in order to guarantee the safety of weldment. If the weld length is long enough compared to the thickness and the breadth of plate, thermal and mechanical behaviors in the middle portion of the plate are assumed to be uniform along the thickness direction(z-axis). Thus, the following conditions(so-called plane deformation) can be assumed for the plate except near its end;1) distributions of stress and strain are independent on the z-axis;2) plane normal to z-axis before deformation remains plane during and after deformation. In this paper, plane-deformation thermal elasto-plastic problem is formulated by being based on the finite element method. Moreover special regards and paid to the fact that material properties in elastic and plastic region are temperature-dependence. And the method to solve the plane-deformation thermal elasto-plastic problem is shown by using the incremental technique. From the results of analysis, the characterisics of distribution of welding residual stress and plastic strain with the production mechanism are clarified.

• Journal of Power System Engineering
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• v.6 no.3
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• pp.24-30
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• 2002

The deformation and fracture behaviors of both Al2O3 and Ni 4.5wt.%Al plasma thermal spray coating were investigated by an acoustic emission method. Plasma thermal spray coating is formed by a process in which melted particles flying with high speed towards substrate, then crash and spread on the substrate surface cooled and solidified in a very short time, stacking of the particles makes coating. A tensile test is conducted on notch specimens in a stress range below the elastic limit of substrate. A bendind test is done on smooth specimens. The waveforms of AE generated from the both test coating specimens can be classified by FFT analysis into two types which low frequency(type I) and high frequency(type II). The type I waveform is considered to corresponds exfoliation of coating layers and type II waveform corresponds the plastic deformation of notch tip. The fracture of the coating layers can estimate by AE event and amplitude, because AE features increase when the deformation generates.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.24 no.6 s.177
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• pp.1456-1469
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• 2000

Mechanical behaviors of uniaxially fiber-reinforced metal matrix composites under transverse loading conditions were studied at room and elevated temperatures. A mono-filament composite was selecte d as a representative analysis model with perfectly bonded fiber/matrix interface assumption. The elastic-plastic and visco-plastic models were investigated by both theoretical and numerical methods. The product of triaxiality factor and effective strain as well as stress components and strain energy was obtained as a function of location to estimate the failure sites in fiber-reinforced metal matrix composite. Results showed that fiber/ matrix interfacial debond plays a key role for local failure at the room temperature, while void creation and growth in addition to the interfacial debond are major concerns at the elevated temperature. It was also shown that there would be an optimal diameter of fiber for the strong fiber-reinforced metal matrix composite.

• Journal of Korean Society of Steel Construction
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• v.18 no.3
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• pp.301-310
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• 2006

If arches are braced by lateral restraints, the ultimate strength of arches is determined by in-plane buckling and plastic bending collapse. This paper is conducted to investigate the in-plane nonlinear elastic and inelastic buckling behavior and the strength of fixed parabolic arches in uniform compresion, as well as to study arch behaviors against non-uniform in-plane compression and bending. As shown by the results, the limit slenderness ratio is suggested to classify the bucklingmode. Buckling strength of fixed parabolic arches under uniform compresion are evaluated using buckling curve for a straight column. Finally, an interaction e quation for arches under combined axial compresion and bending action is proposed.

• Wind and Structures
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• v.5 no.2_3_4
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• pp.329-336
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• 2002

The along-wind response of a surface-mounted elastic fence under the action of wind was investigated numerically. In the computations, two sets of equations, one for the simulation of the unsteady turbulent flow and the other for the calculation of the dynamic motion of the fence, were solved alternatively. The resulting time-series tip response of the fence as well as the flow fields were analyzed to examine the dynamic behaviors of the two. Results show that the flow is unsteady and is dominated by two frequencies: one relates to the shear layer vortices and the other one is subject to vortex shedding. The resulting unsteady wind load causes the fence to vibrate. The tip deflection of the fence is periodic and is symmetric to an equilibrium position, corresponding to the average load. Although the along-wind aerodynamic effect is not significant, the fluctuating quantities of the tip deflection, velocity and acceleration are enhanced as the fundamental frequency of the fence is near the vortex or shedding frequency of the flow due to the occurrence of resonance. In addition, when the fence is relatively soft, higher mode response can be excited, leading to significant increases of the variations of the tip velocity and acceleration.