• Nuclear Engineering and Technology
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• v.48 no.2
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• pp.505-517
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• 2016

The structural integrity of a dual-purpose metal cask currently under development by the Korea Radioactive Waste Agency (KORAD) was evaluated, through numerical simulations and a model test, under high-speed missile impact reflecting targeted aircraft crash conditions. The impact conditions were carefully chosen through a survey on accident cases and recommendations from literature. In the impact scenario, a missile flying horizontally hits the top side of the cask, which is freestanding on a concrete pad, with a velocity of 150 m/s. A simplified missile simulating a commercial aircraft engine was designed from an impact loade-time function available in literature. In the analyses, the dynamic behavior of the metal cask and the integrity of the containment boundary were assessed. The simulation results were compared with the test results for a 1:3 scale model. Although the dynamic behavior of the cask in the model test did not match exactly with the prediction from the numerical simulation, other structural responses, such as the acceleration and strain history during the impact, showed very good agreement. Moreover, the containment function of the cask survived the missile impact as expected from the numerical simulation. Thus, the procedure and methodology adopted in the structural numerical analyses were successfully validated.

• International Journal of Ocean System Engineering
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• v.2 no.2
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• pp.92-96
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• 2012

This study presents a rockfall impact analysis of a typical roadway. Dynamic finite element analyses using ANSYS AUTODYN are conducted to determine the effect of the drop heights (5 m, 10 m) on the damage to a roadway model. The Rockfall is modeled as a spherical shape with a weight of 400 kg, and each drop height is converted to a corresponding impact velocity to save computational time. The roadway model is comprised of an asphalt layer, base layer, sub-base layer, and sub-grade layer. In this paper, the asphalt is modeled using a linear elastic model. The base layer, sub-base layer, and sub-grade layer are modeled using a Mohr-Coulomb model. From the analyses, the effects of the drop height on the damages and stresses are examined and discussed.

• Journal of the Korean Society for Precision Engineering
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• v.20 no.7
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• pp.163-170
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• 2003

The back beam for a automotive bumper was roll formed to improve performance, reduce weight and save cost. For the back beams produced by conventional stamping and roll forming, the crashworthiness analyses were carried out by numerical simulation and real impact test. The characteristic properties and applicability of the roll formed back beam are discussed from the results of the analyses.

• Journal of Korean Society for Atmospheric Environment
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• v.15 no.5
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• pp.599-611
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• 1999

Now that the plume of point source was suspected to have strong impact on visibility impairment in Pusan, we evaluated visibility impairment impact of the pulme from Pusan Thermo Electric Power Plant in Pusan. Level-1 and-2 analyses were carried out using VISCREEN(Visual Impact Screen model). The emission rates for this Pusan Thermo Electric Power Plant was projected to be 116g/s of nitrogen oxides(as $NO_2$). The source fails the level-1 test with a Plume perceptibility(ΔE) of 30, nearly 15 times the screeing threshold. To characterize worstcase meteorological conditions for level-2 screening, we obtained meteorological data from Mar., 1996 to Feb., 1997 of Pusan Thermo Electric Power Plant. The source fails the level-2 test with a ΔE of 17, nearly 8.5 times the screening threshold. These analyses indicated that adverse visibility impairment could not be ruled out. Therefore a Level-3 analysis was performed using PLUVUE II(Plume Visibility model). As a result, maximum reduction of visual range for 0900LST in winter was 0.9%. Visual impact of the plume from vast point source was judged to be considerable in terms of background visibility of urban area.

• Composites Research
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• v.29 no.6
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• pp.321-327
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• 2016

In this study, tests and finite element analyses were performed regarding compression after impact strength for laminated composite structures of unidirectional carbon fiber reinforced plastic widely used in structural materials. Two lay-up sequences of composite laminates were selected as test specimens and four impact energy conditions were applied respectively. Impact and compressive strength tests were conducted in accordance with ASTM standards. Impact damages in test specimens were analyzed by using non-destructive inspection method of C-Scan, and compression after impact strengths were calculated with compressive test results. Progressive failure analysis method that can progressively simulate damages and fractures of fiber/matrix/lamina/laminate level was used for impact and compressive strength analyses. All analysis results including contact force, deflection, impact damages, compressive strengths, etc. were compared to test results, and the validity of analysis method was verified.

• Earthquakes and Structures
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• v.3 no.3_4
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• pp.435-455
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• 2012

An impact on the ground surface may represent several phenomena, such as a crash of an airplane or an explosion or the passage of a train. In order to analyze and design structures and equipment to resist such a type of shocks, the response spectra for an impact on the ground must be given. We investigated the half-space motions due to impact using the finite element method. We performed extensive parametric analyses to define a suitable finite element model and arrive at displacement time histories and response spectra at varying distances from the impact point. The principal scope of our study has been to derive response spectra which: (a) provide insight and illustrate in detail the half-space response to an impact load, (b) can be readily used for the analysis of structures resting on a ground subjected to an impact and (c) are a new family of results for the impact problem and can serve as reference for future research.

• Nuclear Engineering and Technology
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• v.35 no.2
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• pp.154-164
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• 2003

The explicit consideration of different pressurization rates in estimating the probabilities of containment failure modes has a profound effect on the confidence of containment performance evaluation that is so critical for risk assessment of nuclear power plants. Except for the sophisticated NUREG-1150 study, many of the recent containment performance analyses (through Level 2 PSAs or IPE back-end analyses) did not take into account an explicit distinction between slow and fast pressurization in their analyses. A careful investigation of both approaches shows that many of the approaches adopted in the recent containment performance analyses exactly correspond to the NUREG-1150 approach for the prediction of containment failure mode probabilities in the presence of fast pressurization. As a result, it was expected that the existing containment performance analysis results would be subjected to greater or less conservatism in light of the ultimate failure mode of the containment. The main purpose of this paper is to assess potential conservatism of a plant-specific containment performance analysis result in light of containment failure mode probabilities.

• Nuclear Engineering and Technology
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• v.52 no.2
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• pp.397-416
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• 2020

Investigations of the commercial aircraft impact effect on nuclear island infrastructures have been drawing extensive attention, and this paper aims to perform the safety assessment of Generation III nuclear power plant (NPP) buildings subjected to typical commercial aircrafts crash. At present Part II, based on the verified finite element (FE) models of aircrafts Airbus A320 and A380, as well as the NPP containment and auxiliary buildings in Part I of this paper, the whole collision process is reproduced numerically by adopting the coupled missile-target interaction approach with the finite element code LS-DYNA. The impact induced damage of NPP plant under four impact locations of containment (cylinder, air intake, conical roof and PCS water tank) and two impact locations of auxiliary buildings (exterior wall and roof of spent fuel pool room) are evaluated. Furthermore, by considering the inner structures in the containment and raft foundation of NPP, the structural vibration analyses are conducted under two impact locations (middle height of cylinder, main control room in the auxiliary buildings). It indicates that, within the discussed scenarios, NPP structures can withstand the impact of both two aircrafts, while the functionality of internal equipment on higher floors will be affected to some extent under impact induced vibrations, and A380 aircraft will cause more serious structural damage and vibrations than A320 aircraft. The present work can provide helpful references to assess the safety of the structures and inner equipment of NPP plant under commercial aircraft impact.

• Aerospace Engineering and Technology
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• v.13 no.1
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• pp.20-26
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• 2014

In this paper, yield stress, tangent modulus and failure strain were varied to ascertain the influence of impact response such as impact force histories and residual energy. And the buckling behavior of FML(Fiber Metal Laminates) were analyzed using numerical method. A number of analyses on FML and aluminum panel were conducted for shear and compression loading to compare the capability of stability. And to evaluate the static performance, static analysis has performed for box beam structure. Low-velocity impact analysis has performed on FML made of aluminum 2024 sheet and glass/epoxy prepreg layers. And the buckling and static performance of FML have been compared to aluminum using the analysis results. For the comparison of structural performance, similar analyses have been carried out on monolithic aluminum 2024 sheets of equivalent weight.

• Structural Engineering and Mechanics
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• v.23 no.5
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• pp.487-504
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• 2006

Several new versatile two-dimensional p-version finite elements are developed. The element matrices are integrated analytically to guarantee the accuracy and monotonic convergence of the predicted solutions of the proposed p-version elements. The analysis results show that the convergence rate of the present elements is very fast with respect to the number of additional Fourier or polynomial terms in shape functions, and their solutions are much more accurate than those of the linear finite elements for the same number of degrees of freedom. Additionally, the new p-version plate elements without the reduced integration can overcome the shear locking problem over the conventional h-version elements. Using the proposed p-version elements with fast convergent characteristic, the elasto-plastic impact of the structure attached with the absorber is simulated. Good agreement between the simulated and experimental results verifies the present p-version finite elements for the analyses of structural dynamic responses and the structural elasto-plastic impact. Further, using the elasto-plastic impact model and the p-version finite element method, the absorber of the T structure on the Qiantang River is designed for its collision protection.