Damage potential: A dimensionless parameter to characterize soft aircraft impact into robust targets

Lili E. Hlavicka-Laczák,László P. Kollár,György Károlyi 국제구조공학회 2021 Structural Engineering and Mechanics, An Int'l Jou Vol.78 No.1

To investigate numerically the effect of all parameters on the outcome of an aircraft impact into robust engineering structures like nuclear power plant containments is a tedious task. In order to reduce the problem to a manageable size, we propose a single dimensionless parameter, the damage potential, to characterize the main features of the impact. The damage potential, which is the ratio of the initial kinetic energy of the aircraft to the work required to crush it, enables us to find the crucial parameter settings that need to be modelled numerically in detail. We show in this paper that the damage potential is indeed the most important parameter of the impact that determines the time-dependent reaction force when either finite element (FE) modelling or the Riera model is applied. We find that parameters that do not alter the damage potential, like elasticity of the target, are of secondary importance and if parameters are altered in a way that the damage potential remains the same then the course of the impact remains similar. We show, however, that the maximum value of the reaction force can be higher in case of elastic targets than in case of rigid targets due to the vibration of the target. The difference between the Riera and FE model results is also found to depend on the damage potential.

ABCD 파라미터를 활용한 PT의 고주파 전달특성 측정 및 분석

나완수,김형주,김광호,박민혜,심선주,최종기 대한전기학회 2022 전기학회논문지 Vol.71 No.5

This paper presents a measurement setup and network parameter-based analysis methodology for high-frequency transmission characteristics analysis between the primary and secondary sides of a PT (potential transformer). The raw data was extracted by measuring a scattering parameter (S-parameter) using a vector network analyzer. ABCD parameters were obtained using the measurement data to analyze the transmission characteristics of the transformer, and the source-transformer-load model was introduced to define the voltage and current gains considering the terminating impedance and input impedance applied to the transformer. Representative sine wave and square wave was applied to analyze the high-frequency transmission characteristics. In order to analyze the surge transmitted to the secondary system when applied to the actual system, the waveform of the IEC standard was generated and applied. When the load resistance is 1 MΩ, the voltage gain converted from the ideal turns ratio is applied to the input signal was confirmed that the maximum value of surge corresponding to about 1.9 times was formed.

Effect of applied electric potential and micro length scale parameters on the electroelastic analysis of three-layered shear deformable micro-shell

Yang Yang,Keyong Shen,Gholamreza Ghasemian Talkhunche,Mohammad Arefi 국제구조공학회 2021 Smart Structures and Systems, An International Jou Vol.28 No.3

This paper uses higher-order shear deformation theory and modified couple stress theory (MCST) to the electroelastic results of FG micro-shell integrated with piezoelectric thin sheets subjected to electrical and mechanical loads rested on Pasternak's foundation. Third-order shear deformation theory (TSDT) is used for the description of the displacement field. Effect of micro-size is applied using MCST with the introduction of one micro-length scale parameter. Governing equations are derived based on the principle of virtual work. Micro-shell is composed of a FG micro core and two piezoelectric hollow shells. The numerical results are obtained for the simply-supported boundary conditions. Longitudinal and radial displacements are presented in terms of important parameters such as applied electric potentials, micro length scale parameter, dimensionless geometric parameters and two parameters of Pasternak's foundation.

Determination of elastic parameters of the deformable solid bodies with respect to the Earth model

Guliyev, Hatam H.,Javanshir, Rashid J.,Hasanova, Gular H. Techno-Press 2018 Geomechanics & engineering Vol.15 No.5

The study of behavior and values of deformations in the geological medium makes the scientific basis of the methodology of synthesis of true values of parameters of its physico-mechanical and density properties taking into account the influence of geodynamic impacts. The segments of continuous variation of homogeneous elastic uniform deformations are determined under overall compression of the medium. The limits of these segments are defined according to the criteria of instability (on geometric form changes and on "internal" instability). Analytical formulae are obtained to calculate current and limiting (critical) values of deformations within the framework of various variants of small and large initial deformations of the non-classically linearized approach of non-linear elastodynamics. The distribution of deformation becomes non-uniform in the medium while the limiting values of deformations are achieved. The proposed analytical formulae are applicable only within homogeneous distribution of deformations. Numerical experiments are carried out for various elastic potentials. It is found that various forms of instability can precede phase transitions and destruction. The influence of these deformation phenomena should be removed while the physico-mechanical and density parameters of the deformed media are determined. In particular, it is necessary to use the formulae proposed in this paper for this purpose.

Prediction of the Upper and Lower Bounds of Magnetic Vector Potentials in a Linear Magnetostatic Field with Uncertain-but-Bounded Parameters

Pengbo Wang,Jingxuan Wang 한국자기학회 2018 Journal of Magnetics Vol.23 No.1

Uncertainty is ubiquitous in practical engineering and scientific research. The uncertainties in parameters can be treated as interval numbers. The prediction of upper and lower bounds of the response of a system including uncertain parameters is of immense significance in uncertainty analysis. This paper aims to evaluate the upper and lower bounds of magnetic vector potentials in a linear magnetostatic field efficiently with uncertainbut- bounded parameters. The uncertain-but-bounded parameters are represented by interval notations. By performing Taylor series expansion on the magnetic vector potentials obtained from the equilibrium governing equation and by using the properties of interval mathematics, we can calculate the upper and lower bounds of the magnetic vector potentials of a linear magnetostatic field. In order to evaluate the accuracy and efficiency of the proposed method, two numerical examples are used. The results illustrate that the precision of the proposed method is acceptable for engineering applications, and the computation time of the proposed method is significantly less than that of the Monte Carlo simulation, which is the most widely used method related to uncertainties. The Monte Carlo simulation requires a large number of samplings, and this leads to significant runtime consumption.

슬러그류 액상속도 측정용 전류형식 전자기유량계 개발

강덕홍(Deok-Hong Kang),안예찬(Yeh-Chan Ahn),김종록(Jong-Rok Kim),오병도(Byung Do Oh),김무환(Moo Hwan Kim) 대한기계학회 2004 대한기계학회 춘추학술대회 Vol.2004 No.4

The transient nature and complex flow geometries of two-phase gas-liquid flows cause fundamental difficulties when measuring flow velocity using an electromagnetic flowmeter. Recently, a current-sensing flowmeter was introduced to obtain measurements with high temporal resolution (Ahn et al.). In this study, current-sensing flowmeter theory was applied to measure the fast velocity transients in slug flows. To do this, the velocity fields of axisymmetric gas-liquid slug flow in a vertical pipe were obtained using Volume-of-Fluid (VOF) method and the virtual potential distributions for the electrodes of finite size were also computed using the finite volume method for the simulated slug flow. The output signal prediction for slug flow was carried out from the velocity and virtual potential (or weight function) fields. The flowmeter was numerically calibrated to obtain the cross-sectional liquid mean velocity at an electrode plane from the predicted output signal. Two calibration parameters are required for this procedure: a flow pattern coefficient and a localization parameter. The flow pattern coefficient was defined by the ratio of the liquid resistance between the electrodes for two-phase flow with respect to that for single-phase flow, and the localization parameter was introduced to avoid errors in the flowmeter readings caused by liquid acceleration or deceleration around the electrodes. These parameters were also calculated from the computed velocity and virtual potential fields. The results can be used to obtain the liquid mean velocity from the slug flow signal measured by a current-sensing flowmeter.

Smart analysis of doubly curved piezoelectric nano shells: Electrical and mechanical buckling analysis

Mohammad Arefi 국제구조공학회 2020 Smart Structures and Systems, An International Jou Vol.25 No.4

Stability analysis of three-layered piezoelectric doubly curved nano shell with accounting size dependency is performed in this paper based on first order shear deformation theory and curvilinear coordinate system relations. The elastic core is integrated with sensor and actuator layers subjected to applied electric potentials. The principle of virtual work is employed for derivation of governing equations of stability. The critical electrical and mechanical buckling loads are evaluated in terms of important parameters of the problem such as size-dependent parameter, two principle angle of doubly curved shell and two parameters of Pasternak's foundation. One can conclude that mechanical buckling loads are decreased with increase of nonlocal parameter while the electrical buckling loads are increased.

Parameter Selecting in Artificial Potential Functions for Local Path Planning

Dong Hun Kim 한국지능시스템학회 2005 INTERNATIONAL JOURNAL of FUZZY LOGIC and INTELLIGE Vol.5 No.4

Artificial potential field (APF) is a widely used method for local path planning of autonomous mobile robot. So far, many different types of APF have been implemented. Once the artificial potential functions are selected, how to choose appropriate parameters of the functions is also an important work. In this paper, a detailed analysis is given on how to choose proper parameters of artificial functions to eliminate free path local minima and avoid collision between robots and obstacles. Two kinds of potential functions: Gaussian type and Quadratic type of potential functions are used to solve the above local minima problem respectively. To avoid local minima occurred in realistic situations such as 1) a case that the potential of the goal is affected excessively by potential of the obstacle, 2) a case that the potential of the obstacle is affected excessively by potential of the goal, the design guidelines for selecting appropriate parameters of potential functions are proposed.

Parameter Selecting in Artificial Potential Functions for Local Path Planning

Kim, Dong-Hun Korean Institute of Intelligent Systems 2005 INTERNATIONAL JOURNAL of FUZZY LOGIC and INTELLIGE Vol.5 No.4

Artificial potential field (APF) is a widely used method for local path planning of autonomous mobile robot. So far, many different types of APF have been implemented. Once the artificial potential functions are selected, how to choose appropriate parameters of the functions is also an important work. In this paper, a detailed analysis is given on how to choose proper parameters of artificial functions to eliminate free path local minima and avoid collision between robots and obstacles. Two kinds of potential functions: Gaussian type and Quadratic type of potential functions are used to solve the above local minima problem respectively. To avoid local minima occurred in realistic situations such as 1) a case that the potential of the goal is affected excessively by potential of the obstacle, 2) a case that the potential of the obstacle is affected excessively by potential of the goal, the design guidelines for selecting appropriate parameters of potential functions are proposed.

변수 최적화 기법을 이용한 미소중력 상황에서 발생하는 추진제 움직임의 모델링에 관한 연구

이동연,탁민제 한국항공우주학회 2015 한국항공우주학회 학술발표회 논문집 Vol.2015 No.11

본 논문에서는 미소 중력 상황에서 발생 할 수 있는 추진제 움직임의 모델링에 관한 연구를 수행한다. 자유롭게 움직이는 유체를 적절히 표현하기 위해서 포텐셜 필드 기법을 활용하여 유체의 영향력을 나타내었으며, 영향력이 유체가 처해진 상황에 따라 적절히 변화하도록 관련 변수를 정의하였다. 이러한 변수들은 모델링이 유체를 적절히 표현할 수 있도록 변수 최적화 기법을 이용하여 정해지며, 사용된 변수 최적화 기법은 빠른 연산시간을 가지는 PSO 알고리즘이다. 최적화는 아리안 5 ECA 발사체의 상단에서 나타날 수 있는 환경을 기반으로 이루어지며, 최종적으로 얻어진 모델링 변수에 대해서 CFD 데이터를 비교하여 성능에 대한 검증을 수행하였다. In this paper, the research about the modeling of propellant motion in micro-gravity condition is conducted. In order to describe the freely moved fluid, the potential field method is used for the influence field of fluid. And, the parameters related to the influence field are defined and changed according to the condition of fluid. These parameters are determined by parameters optimization algorithm to represent the fluid condition properly, the parameters optimization algorithm used in this paper is PSO algorithm having fast calculation ability. The optimization based on the environments which can be generated in Ariane 5 ECA Launch Vehicle Upper Stage is performed. Finally, the verification about the performance of modeling parameters is conducted using CFD data comparison.