scholarly journals Research on Impact Process of Lander Footpad against Simulant Lunar Soils

2015 ◽  
Vol 2015 ◽  
pp. 1-24 ◽  
Author(s):  
Bo Huang ◽  
Zhujin Jiang ◽  
Peng Lin ◽  
Daosheng Ling
Keyword(s):  
Numerical Model ◽  
Element Model ◽  
Reduction Factor ◽  
Model Tests ◽  
Impact Process ◽  
Scale Reduction ◽  
Axial Forces ◽  
Lunar Soils ◽  
Impact Kinetic Energy ◽  
The Impact

The safe landing of a Moon lander and the performance of the precise instruments it carries may be affected by too heavy impact on touchdown. Accordingly, landing characteristics have become an important research focus. Described in this paper are model tests carried out using simulated lunar soils of different relative densities (called “simulant” lunar soils below), with a scale reduction factor of 1/6 to consider the relative gravities of the Earth and Moon. In the model tests, the lander was simplified as an impact column with a saucer-shaped footpad with various impact landing masses and velocities. Based on the test results, the relationships between the footpad peak feature responses and impact kinetic energy have been analyzed. Numerical simulation analyses were also conducted to simulate the vertical impact process. A 3D dynamic finite element model was built for which the material parameters were obtained from laboratory test data. When compared with the model tests, the numerical model proved able to effectively simulate the dynamic characteristics of the axial forces, accelerations, and penetration depths of the impact column during landing. This numerical model can be further used as required for simulating oblique landing impacts.

Non-Linear Analysis of AP1000 Auxiliary and Shield Building Subjected to Combined Accident Thermal and Seismic Loadings

2014 ◽  
Author(s):  
J. Jennifer Zhang ◽  
Lee J. Tunon-Sanjur
Keyword(s):  
Reinforced Concrete ◽  
Thermal Loading ◽  
Structural Response ◽  
Nonlinear Behavior ◽  
Element Model ◽  
Reduction Factor ◽  
Axial Forces ◽  
Wall Stiffness ◽  
Seismic Loadings ◽  
The Impact

Under the combined accident thermal and seismic loadings, the structural response of the AP1000 Auxiliary and Shield Building (ASB) is numerically investigated. A nonlinear Finite Element Model (FEM) of the AP1000 ASB is developed, in which the rebar in the reinforced concrete is explicitly described and the nonlinear behavior of the concrete is considered. The numerical modeling method and material models used by the reinforced concrete are validated by the testing results published in the literature. The propagation of the thermal loading-induced concrete cracks along the wall thickness is studied. Furthermore, the effects of thermal cracks on the wall stiffness, the development of the thermal stress and the axial forces acting on the reinforcement are fully discussed. The impact of thermal concrete cracks on the design demand of the rebar is also investigated. It is worthy of being further studied how to incorporate the appropriate reduction factor caused by concrete cracks into the linear structural design.

Fractality of Simulated Fracture

2009 ◽  
Vol 409 ◽  
pp. 154-160 ◽  
Author(s):  
Petr Frantík ◽  
Zbyněk Keršner ◽  
Václav Veselý ◽  
Ladislav Řoutil
Keyword(s):  
Numerical Model ◽  
Elastic Plate ◽  
Model Simulation ◽  
Element Model ◽  
The Other ◽  
Particle Model ◽  
Discrete Element Model ◽  
Fractal Nature ◽  
Discrete Elements ◽  
The Impact

The paper is focussed on numerical simulations of the fracture of a quasi-brittle specimen due to its impact onto a fixed rigid elastic plate. The failure of the specimen after the impact is modelled in two ways based on the physical discretization of continuum: via physical discrete elements and pseudo-particles. Advantages and drawbacks of both used methods are discussed. The size distribution of the fragments of the broken specimen resulting from physical discrete element model simulation follows a power law, which indicates the ability of the numerical model to identify the fractal nature of the fracture. The pseudo-particle model, on the other side, can successfully predict the kinematics of the fragments of the specimen under impact failure.

Crash simulation of fuselage section in the rebound process and the secondary-impact process

2020 ◽  
Vol 92 (8) ◽  
pp. 1245-1256
Author(s):  
Zibo Jin ◽  
Daochun Li ◽  
Jinwu Xiang
Keyword(s):  
Finite Element ◽  
Three Dimensional ◽  
Element Model ◽  
Structural Vibration ◽  
Dynamic Simulations ◽  
Content Type ◽  
Secondary Impact ◽  
Impact Process ◽  
Impact Surface ◽  
The Impact

Purpose This paper aims to investigate the rebound process and the secondary-impact process of the fuselage section that occurs in the actual crash events. Design/methodology/approach A full-scale three-dimensional finite element model of the fuselage section was developed to carry out the dynamic simulations. The rebound process was simulated by removing the impact surface at a certain point, while the secondary-impact process was simulated by striking the impact surface against the fuselage bottom after the first impact. Findings For the rebound process, the fuselage structure restores deformation due to the springback of the fuselage bottom, and it results in structural vibration of the fuselage section. For the secondary-impact process, the fuselage deformation is similar with that of the single impact process, indicating that the intermittent impact loading has little influence on the overall deformation of the fuselage section. The strut failure is the determining factor to the acceleration responses for both the rebound process and the secondary-impact process. Practical implications The rebound process and the secondary-impact process, which is difficult to study by experiments, was investigated by finite element simulations. The structure deformations and acceleration responses were obtained, and they can provide guidance for the crashworthy design of fuselage structures. Originality/value This research first investigated the rebound process and the secondary-impact process of the fuselage section. The absence of the ground load and the secondary-impact was simulated by controlling the impact surface, which is a new simulating method and has not been used in the previous research.

Traumatic Events in Human Head: Biomechanical Insight by Means of a Finite Element Model

2006 ◽  
Author(s):  
Giovanni Belingardi ◽  
Giorgio Chiandussi ◽  
Ivan Gaviglio
Keyword(s):  
Finite Element ◽  
Numerical Model ◽  
Finite Element Model ◽  
Brain Injuries ◽  
Head Injuries ◽  
Traumatic Events ◽  
Traumatic Injury ◽  
Human Head ◽  
Element Model ◽  
The Impact

Head injuries due to traumatic events in case of head impact are one of the main causes of death or permanent invalidity in vehicle crash. The main purpose of the present work is to evaluate pressure and stress distributions in bones and brain tissues of a human head due to an impact by means of numerical simulations. Pressures and stresses in the different zones of the head can be related to the main brain injuries as verified by head traumatology doctors. The availability of a numerical model of head allows to quantify the relationship between type and intensity of the impact and the possible head injury. This capability represents a relevant step torward an effective traumatic injury prevention. The proposed numerical model is quite complex although some simplifications have been introduced like modeling all the inner organs as a continuum without sliding interfaces or fluid elements. Geometrical characteristics for the finite element model have been extracted from CT (Computer Tomography) and MRI (Magnetic Resonance Image) scanner images, while material mechanical characteristics have been taken from literature. The model has been validated by comparing the numerical results and the experimental results from literature. The protecting action of the ventricles and of several membranes (dura mater, tentorium and falx) has been evaluated.

scholarly journals A Model for the Thermal Behaviour of an Offshore Cable Installed in a J-Tube

Proceedings ◽  
2020 ◽  
Vol 58 (1) ◽  
pp. 31
Author(s):  
Jeremy Arancio ◽  
Ahmed Ould El Moctar ◽  
Minh Nguyen Tuan ◽  
Faradj Tayat ◽  
Jean-Philippe Roques
Keyword(s):  
Sensitivity Analysis ◽  
Numerical Model ◽  
Thermal Behaviour ◽  
Energy Production ◽  
Power Transmission ◽  
Temperature Fields ◽  
Sobol Indices ◽  
Lumped Element ◽  
Thermal Phenomena ◽  
The Impact

In the race for energy production, supplier companies are concerned by the thermal rating of offshore cables installed in a J-tube, not covered by IEC 60287 standards, and are now looking for solutions to optimize this type of system. This paper presents a numerical model capable of calculating temperature fields of a power transmission cable installed in a J-tube, based on the lumped element method. This model is validated against the existing literature. A sensitivity analysis performed using Sobol indices is then presented in order to understand the impact of the different parameters involved in the heating of the cable. This analysis provides an understanding of the thermal phenomena in the J-tube and paves the way for potential technical and economic solutions to increase the ampacity of offshore cables installed in a J-tube.

Finite Element Analysis of the Distributed Vibration Absorbers for Structural Noise Control

2005 ◽  
Author(s):  
Ashwini Gautam ◽  
Chris Fuller ◽  
James Carneal
Keyword(s):  
Finite Element ◽  
Numerical Model ◽  
Base Plate ◽  
Element Model ◽  
Fe Model ◽  
Vibration Absorbers ◽  
Element Analysis ◽  
Poroelastic Media ◽  
Hexahedral Elements ◽  
Component Models

This work presents an extensive analysis of the properties of distributed vibration absorbers (DVAs) and their effectiveness in controlling the sound radiation from the base structure. The DVA acts as a distributed mass absorber consisting of a thin metal sheet covering a layer of acoustic foam (porous media) that behaves like a distributed spring-mass-damper system. To assess the effectiveness of these DVAs in controlling the vibration of the base structures (plate) a detailed finite elements model has been developed for the DVA and base plate structure. The foam was modeled as a poroelastic media using 8 node hexahedral elements. The structural (plate) domain was modeled using 16 degree of freedom plate elements. Each of the finite element models have been validated by comparing the numerical results with the available analytical and experimental results. These component models were combined to model the DVA. Preliminary experiments conducted on the DVAs have shown an excellent agreement between the results obtained from the numerical model of the DVA and from the experiments. The component models and the DVA model were then combined into a larger FE model comprised of a base plate with the DVA treatment on its surface. The results from the simulation of this numerical model have shown that there has been a significant reduction in the vibration levels of the base plate due to DVA treatment on it. It has been shown from this work that the inclusion of the DVAs on the base plate reduces their vibration response and therefore the radiated noise. Moreover, the detailed development of the finite element model for the foam has provided us with the capability to analyze the physics behind the behavior of the distributed vibration absorbers (DVAs) and to develop more optimized designs for the same.

scholarly journals Driven Pile Effects on Nearby Cylindrical and Semi-Tapered Pile in Sandy Clay

2021 ◽  
Vol 11 (7) ◽  
pp. 2919
Author(s):  
Massamba Fall ◽  
Zhengguo Gao ◽  
Becaye Cissokho Ndiaye
Keyword(s):  
Coupling Effect ◽  
Lateral Displacement ◽  
Bending Moment ◽  
Adaptive Mesh ◽  
Pile Driving ◽  
Arbitrary Lagrangian Eulerian ◽  
Axial Forces ◽  
Tapered Pile ◽  
Driven Pile ◽  
The Impact

A pile foundation is commonly adopted for transferring superstructure loads into the ground in weaker soil. They diminish the settlement of the infrastructure and augment the soil-bearing capacity. This paper emphases the pile-driving effect on an existing adjacent cylindrical and semi-tapered pile. Driving a three-dimensional pile into the ground is fruitfully accomplished by combining the arbitrary Lagrangian–Eulerian (ALE) adaptive mesh and element deletion methods without adopting any assumptions that would simplify the simulation. Axial forces, bending moment, and lateral displacement were studied in the neighboring already-installed pile. An investigation was made into some factors affecting the forces and bending moment, such as pile spacing and the shape of the already-installed pile (cylindrical, tapered, or semi-tapered). An important response was observed in the impact of the driven pile on the nearby existing one, the bending moment and axial forces were not negligible, and when the pile was loaded, it was recommended to consider the coupling effect. Moreover, the adjacent semi-tapered pile was subjected to less axial and lateral movement than the cylindrical one with the same length and volume for taper angles smaller than 1.0°, and vice versa for taper angles greater than 1.4°.

scholarly journals Investigation of the Thickness Differential on the Formability of Aluminum Tailor Welded Blanks

Metals ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 875
Author(s):  
Jie Wu ◽  
Yuri Hovanski ◽  
Michael Miles
Keyword(s):  
Experimental Data ◽  
Finite Element ◽  
Numerical Model ◽  
Plastic Strain ◽  
Finite Element Model ◽  
Equivalent Plastic Strain ◽  
Element Model ◽  
Dome Height ◽  
Tailor Welded Blanks ◽  
Simulation Results

A finite element model is proposed to investigate the effect of thickness differential on Limiting Dome Height (LDH) testing of aluminum tailor-welded blanks. The numerical model is validated via comparison of the equivalent plastic strain and displacement distribution between the simulation results and the experimental data. The normalized equivalent plastic strain and normalized LDH values are proposed as a means of quantifying the influence of thickness differential for a variety of different ratios. Increasing thickness differential was found to decrease the normalized equivalent plastic strain and normalized LDH values, this providing an evaluation of blank formability.

Investigation on the free vibration behavior of sandwich conical shells with reinforced cores

2021 ◽  
pp. 109963622110204
Author(s):  
Mehdi Zarei ◽  
Gholamhossien Rahimi ◽  
Davoud Shahgholian-Ghahfarokhi
Keyword(s):  
Free Vibration ◽  
Orientation Angle ◽  
Element Model ◽  
Filament Winding ◽  
Vertex Angle ◽  
Sandwich Shell ◽  
Cross Sectional ◽  
Conical Shells ◽  
Vibration Behavior ◽  
Axial Forces

The free vibration behavior of sandwich conical shells with reinforced cores is investigated in the present study using experimental, analytical, and numerical methods. A new effective smeared method is employed to superimpose the stiffness contribution of skins with those of the stiffener in order to achieve equivalent stiffness of the whole structure. The stiffeners are also considered as a beam to support shear forces and bending moments in addition to the axial forces. Using Donnell’s shell theory and Galerkin method, the natural frequencies of the sandwich shell are subsequently derived. To validate analytical results, experimental modal analysis (EMA) is further conducted on the conical sandwich shell. For this purpose, a method is designed for manufacturing specimens through the filament winding process. For more validation, a finite element model (FEM) is built. The results revealed that all the validations were in good agreement with each other. Based on these analyses, the influence of the cross-sectional area of the stiffeners, the semi-vertex angle of the cone, stiffener orientation angle, and the number of stiffeners are investigated as well. The results achieved are novel and can be thus employed as a benchmark for further studies.

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