• Structural Engineering and Mechanics
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• v.91 no.1
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• pp.75-86
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• 2024

In this paper, the porous metal PM-35 is proposed as the filler material of filled thin-walled tubes (FTTs), and a series of experimental study is conducted to investigate the dynamic behavior and energy absorption performance of PM-35 filled thin-walled tubes under impact loading. Firstly, cylinder solid specimens of PM-35 steel are tested to investigate the impact mechanical behavior by using the Split Hopkinson pressure bar set (SHP); Secondly, the filled thin-walled tube specimens with different geometric parameters are designed and tested to investigate the feasibility of PM-35 steel applied in FTTs by the orthogonal test. According to the results of this research, it is concluded that PM-35 steel is with the excellent characteristics of high energy absorption capacity and low yield strength, which make it a potential filler material for FTTs. The micron-sizes pore structure of PM-35 is the main reason for the macroscopic mechanical behavior of PM-35 steel under impact loading, which makes the material to exhibit greater deformation when subjected to external forces and obviously improve the toughness of the material. In addition, PM-35 steel core-filled thin-wall tube has excellent energy absorption ability under high-speed impact, which shows great application potential in the anti-collision structure facilities of high-speed railway and maglev train. The parameter V0 is most sensitive to the energy absorption of FTT specimens under impact loading, and the sensitivity order of different variations to the energy absorption is loading speed V0>D/t>D/L. The loading efficiency of the FTT is affected by its different geometry, which is mainly determined by the sleeve material and the filling material, which are not sensitive to changes in loading speed V0, D/t and D/L parameters.

• Advances in concrete construction
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• v.9 no.3
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• pp.313-326
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• 2020

Glass fiber-reinforced polymer (GFRP) bars have been introduced as an effective alternative for the conventional steel reinforcement in concrete structures to mitigate the costly consequences of steel corrosion. However, despite the superior performance of these composite materials in terms of corrosion, the effect of replacing steel reinforcement with GFRP on the seismic performance of concrete structures is not fully covered yet. To address some of the key parameters in the seismic behavior of GFRP-reinforced concrete (RC) structures, two full-scale beam-column joints reinforced with GFRP bars and stirrups were constructed and tested under two phases of loading, each simulating a severe ground motion. The objective was to investigate the effect of damage due to earthquakes on the service and ultimate behavior of GFRP-RC moment-resisting frames. The main parameters under investigation were geometrical configuration (interior or exterior beam-column joint) and joint shear stress. The performance of the specimens was measured in terms of lateral load-drift response, energy dissipation, mode of failure and stress distribution. Moreover, the effect of concrete damage due to earthquake loading on the performance of beam-column joints under service loading was investigated and a modified damage index was proposed to quantify the magnitude of damage in GFRP-RC beam-column joints under dynamic loading. Test results indicated that the geometrical configuration significantly affects the level of concrete damage and energy dissipation. Moreover, the level of residual damage in GFRP-RC beam-column joints after undergoing lateral displacements was related to reinforcement ratio of the main beams.

• Nuclear Engineering and Technology
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• v.55 no.7
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• pp.2697-2711
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• 2023

In this study, the validity of reducing the number of gas turbine stages designed for a nitrogen Brayton cycle coupled to a sodium-cooled fast reactor was assessed. The turbine performance was evaluated through computational fluid dynamics (CFD) simulations under different off-design conditions controlled by a reduced flow rate and reduced rotational speed. Two different multistage gas turbines designed to extract almost the same specific work were selected: two- and three-stage turbines (mid-span stage loading coefficient: 1.23 and 1.0, respectively). Real gas properties were considered in the CFD simulation in accordance with the Peng-Robinson's equation of state. According to the CFD results, the off-design performance of the two-stage turbine is comparable to that of the three-stage turbine. Moreover, compared to the three-stage turbine, the two-stage turbine generates less entropy across the shock wave. The results indicate that under both design and off-design conditions, increasing the stage loading coefficient for a fewer number of turbine stages is effective in terms of performance and size. Furthermore, the Ellipse law can be used to assess off-design performance and increasing exponent of the expansion ratio term better predicts the off-design performance with a few stages (two or three).

• Journal of Environmental Science International
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• v.9 no.4
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• pp.351-367
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• 2000

Air-lift biofilm reactor should be an admirable process substituting conventional activated sludge process, because of its small area requirement as well as high volumetric loading capacity and stability against loading and chemical shocks. However most of the past research on the performance of ABR was focused on the sewage treatment. This research studied the applicability of ABR to treat high strength wastewater. A bench-scale ABR was operated to treat high strength synthetic wastewater, tannery wastewater and petrochemical wastewater, and its applicability was conclusive In case of synthetic wastewater, ABR showed good performance in which the substarate removal efficiency was higher that 80% even under short HRT(1.4 hr) and high volumetric loading rate(9.3 kgCODcr/$m^3$.day). When ABR was applied to treat tannery wastewater, it was suggested that the maximum volumetric loading rate and F/M ratio should be 7.7kgCODcr/$m^3$.day, 0.76 $day^{-1}$, respectively. And high substrate removal efficiency over than 90 % was observed with 4,000 mgCODcr/L of petrochemical wastewater. Even though effluent concentration was quite high, ABR should be applicable to treat the high strength wastewater, because of its high loading capacity.

• Journal of Periodontal and Implant Science
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• v.35 no.1
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• pp.65-76
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• 2005

This retrospective study evaluates the clinical performance of the recently introduced $XiVE^{(R)}$ implant(Dentsply-Friadent) with a new macro-design to improve primary stability. A total of 208 $XiVE^{(R)}$ implants (101 in the maxilla and 107 in the mandible) were placed in 71 patients. The average age of the patients was 49 years. Of the 208 implants, 190 (91.3%) were posterior implants and 82 (39.4%) were placed in compromised sites (grafted sites). Clinical and radiographic evaluation were made at second stage surgery for exposure and after functional loading. 192 implants in 64 patients were evaluated at exposure and 146 implants in 50 patients were loaded (average 170 days-loading) and evaluated after functional loading. Of 192 implants available for evaluation before loading, 3 implants failed (early failure) ; 1 before exposure, 1 at exposure and 1 during prosthetic procedure. 2 implants were in the maxilla and 1 was in the mandible. The success rate before loading was 98.4%. After functional loading, no implant failure was occurred in 146 implants evaluated during this period (100% interval success rate). This preliminary data with a new implant showed excellent success rate although the majority of implants evaluated in this study were placed in the posterior region of the jaw and compromised sites.

• Structural Engineering and Mechanics
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• v.17 no.5
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• pp.627-639
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• 2004

The objective of this research was to evaluate the performance of metal-plate-connected truss joints subjected to cyclic loading conditions that simulated seismic events in the lives of the joints. We also investigated the duration of load factor for these joints. We tested tension splice joints and heel joints from a standard 9.2-m Fink truss constructed from $38-{\times}89-mm$ Douglas-fir lumber: 10 tension splice joints for static condition and for each of 6 cyclic loading conditions (70 joints total) and 10 heel joints for static condition and for each of 3 cyclic loading conditions (40 joints total). We evaluated results by comparing the strengths of the control group (static) with those of the cyclic loading groups. None of the cyclic loading conditions showed any strength degradation; however, there was significant stiffness degradation for both types of joint. The results of this research show that the current duration of load factor of 1.6 for earthquake loading is adequate for these joints.

• Smart Structures and Systems
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• v.30 no.4
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• pp.353-369
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• 2022

In this paper, a new sensor chip with frequency reconstruction range of 2.252 GHz ~ 2.450 GHz is designed and fabricated. On this basis, a self-designed "T-shaped" shell is added to overcome the disadvantage of uneven deformation of the traditional steel shell, and the range of the sensor chip is expanded to 0 kN ~ 96 kN. The liquid metal antenna is used to carry out a step-by-step loading test, and the relationship between the antenna resonance frequency and the pressure load is analyzed. The results show that there is a good linear relationship between the pressure load and the resonant frequency. Therefore, the liquid metal antenna can be regarded as a pressure sensor. The cyclic loading and unloading experiments of the sensor are carried out, and different loading rates are used to explore the influence on the performance of the sensor. The loading and unloading characteristic curves and the influence characteristic curves of loading rate are plotted. The experimental results show that the sensor has no residual deformation during the cycle of loading and unloading. Moreover, the influence of temperature on the performance of the sensor is studied, and the temperature correction formula is derived.

• Proceedings of the Korea Concrete Institute Conference
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• 1999.10a
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• pp.311-314
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• 1999

This study is aim to evaluate of the flexural performance of specialty cellulose fiber reinforced concrete. Flexural test is proceeded by third-point loading method and the size of the test specimens is 15$\times$15$\times$55cm. The rate of loading was 0.006mm/min. The effects of differing fiber volume fraction(0.08%, 0.1%, 0.15%) were studied. The results of test on the specialty cellulose fiber reinforced concrete were compared with plain and polypropylene fiber reinforced concrete. Results indicated that specially cellulose fiber reinforcement showed an improvement of flexural performance.

• Proceedings of the Korean Powder Metallurgy Institute Conference
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• 2006.09b
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• pp.887-888
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• 2006

The present study describes the wear and mechanical behaviour of carbide composites in cyclic loading applications (blanking of sheet metal). Adhesive wear as well as fatigue endurance were tested, complemented by XRD studies. It was found that the blanking performance of a carbide composite is controlled by its resistance to adhesion wear and fatigue sensitivity. XRD studies revealed that fatigue damage is preceded by plastic strain in both phases of the composites

• Journal of Mechanical Science and Technology
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• v.20 no.4
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• pp.482-493
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• 2006

The carbody structure of a high speed train passing through a tunnel is subjected to pressure fluctuation. Fatigue strength of the carbody structure against the fluctuating pressure loading should be proved in the design stage for safety. In this study, to get the useful information on the pressure fluctuation in the tunnel, measurement has been conducted during test running of KHST on the high speed line for two years. The measured results were analyzed and arranged to be used for carbody design. A prediction method for the magnitude and frequency of pressure change was proposed and the propagating characteristics of pressure wave was investigated. By statistical analysis for the measured results, a pressure loading spectrum for the high speed train was given. The proposed method can also be used to estimate the pressure loading spectrum for new high speed line at design stage combined with the results of train performance simulation.