Compressive Response of Pyramidal Lattices Embedded in Foams

2013 ◽  
Vol 81 (1) ◽  
Author(s):  
C. I. Hammetter ◽  
F. W. Zok
Keyword(s):  
Compressive Loading ◽  
Analytical Models ◽  
Compressive Response ◽  
Rule Of Mixtures ◽  
Mass Fractions ◽  
Foam Stabilization ◽  
Equivalent Mass ◽  
Synergistic Behavior ◽  
Constituent Mass ◽  
Deformation Modes

Recent endeavors to combine the desirable energy-absorption characteristics of stochastic foams with the comparatively high strengths of pyramidal lattices have shown promise for creating composites that outperform their constituents alone under compressive loading. Herein we employ numerical and analytical models to identify both the mechanisms by which synergistic behavior is obtained in such composites and the constituent mass fractions that yield maximum benefits. We find that the loading boundary conditions play a crucial role. When, for instance, composites are loaded between plates that are well bonded to the composites, their specific strengths invariably exceed those predicted by a rule-of-mixtures; however, these strengths can always be improved through an optimized lattice of equivalent mass. In contrast, when the composites are loaded between frictionless plates, their specific strengths exceed not only rule-of-mixtures predictions but, in many cases, also that of any mass-equivalent pyramidal lattice alone subject to the same (frictionless) conditions. The origin of this behavior is found to arise from foam-stabilization of lattice bending and splaying: deformation modes that govern strength in the absence of foam. In essence, the foam causes a transition from bend-dominated to stretch-dominated behavior in the lattice.

Energy Absorption of Thin Walled Members Under Axial Compressive Loading

2014 ◽  
Author(s):  
Eboreime Ohioma ◽  
Muhammad Ali ◽  
Khairul Alam
Keyword(s):  
Energy Absorption ◽  
Cross Sections ◽  
Compressive Loading ◽  
Thin Wall ◽  
Analysis Software ◽  
Element Analysis ◽  
Cross Sectional ◽  
Compressive Loads ◽  
Thin Walled ◽  
Deformation Modes

This study was conducted to investigate the effects of cross-sectional geometry on thin wall axial crushing members for the purpose of improved energy absorption. A total of five geometrically equivalent shapes (same wall thickness area, material, and length) were analyzed namely, triangle, rectangle, square, pentagon, and circle. The deformation modes and energy absorption of the members were studied under compressive loads and compared using ABAQUS/Explicit module, finite element analysis software. The simulations revealed that for the five geometrically equivalent cross sections under equal loading conditions, the pentagon shaped member absorbed the highest amount of energy. As compared to baseline rectangle member, the pentagon member absorbed approximately 25–28% more energy.

Study of Energy Absorption Characteristics of Square Tube With Composite Cellular Core

2018 ◽  
Author(s):  
Muhammad Ali ◽  
Eboreime Ohioma ◽  
Khairul Alam
Keyword(s):  
Energy Absorption ◽  
Compressive Loading ◽  
Absorption Capacity ◽  
Structural Members ◽  
Tubular Structures ◽  
Tube Material ◽  
Energy Absorption Capacity ◽  
Core Tube ◽  
Energy Absorbing ◽  
Deformation Modes

Square tubes are primarily used in automotive structures to absorb energy in the event of an accident. The energy absorption capacity of these structural members depends on several parameters such as tube material, wall thickness, axial length, deformation modes, locking strain, crushing stress, etc. In this paper, the work presented is a continuation of research conducted on exploring the effects of the introduction of cellular core in tubular structures under axial compressive loading. Here, the crushing response of composite cellular core tube was numerically studied using ABAQUS/Explicit module. The energy absorbing characteristics such as deformation or collapsing modes, crushing/ reactive force, crushing stroke, and energy curves were discussed. The composite cellular core tube shows promise for improving the crashworthiness of automobiles.

A Dynamic Damage Model for Uniaxial Compressive Response of AD90 Alumina

2007 ◽  
Vol 340-341 ◽  
pp. 289-294
Author(s):  
Hui Lan Ren ◽  
Ping Li
Keyword(s):  
Crack Nucleation ◽  
Damage Model ◽  
Compressive Loading ◽  
Polycrystalline Alumina ◽  
Compressive Response ◽  
Time Histories ◽  
Surface Particle ◽  
Planar Impact ◽  
Impact Experiments ◽  
Dynamic Damage

The dynamic response of polycrystalline alumina were investigated in the pressure range of 0-13Gpa by planar impact experiments. Manganin gauges were employed to obtain the stress-time histories. From the free surface particle velocity profiles indicate the dispersion of the “plastic” wave for alumina. Using path line principle of Lagrange Analysis the dynamic mechanical behaviors for alumina under impact loading are analyzed, such as nonlinear, strain rate dependence, dispersion and declination of shock wave in the material. A damage model applicable to ceramics subjected to dynamic compressive loading is developed. The model is based on the damage micromechanics and established on wing crack nucleation and growth. The results of the dynamic damage evolution model are compared to the experimental results and a good correlation is obtained.

scholarly journals A combustion model sensitivity study for CH4/H2 bluff-body stabilized flame

2007 ◽  
Vol 221 (11) ◽  
pp. 1377-1390 ◽  
Author(s):  
M Hossain ◽  
W Malalasekera
Keyword(s):  
Bluff Body ◽  
Mixture Fraction ◽  
Sensitivity Study ◽  
Combustion Model ◽  
Flamelet Model ◽  
Combustion Models ◽  
Mass Fractions ◽  
Experimental Values ◽  
Constituent Mass ◽  
Laminar Flamelet

The objective of the current work is to assess the performance of different combustion models in predicting turbulent non-premixed combustion in conjunction with the k-∊ turbulence model. The laminar flamelet, equilibrium chemistry, constrained equilibrium chemistry, and flame sheet models are applied to simulate combustion in a CH4/H2 bluff-body flame experimentally studied by the University of Sydney. The computational results are compared to experimental values of mixture fraction, temperature, and constituent mass fractions. The comparison shows that the laminar flamelet model performs better than other combustion models and mimics most of the significant features of the bluff-body flame.

Using Micro-Alloying (0.5Zr-0.4Ce) to Significantly Enhance Hardness, Tensile and Compressive Response of Magnesium

2018 ◽  
Vol 928 ◽  
pp. 177-182
Author(s):  
Sravya Tekumalla ◽  
Wei Yang ◽  
Manoj Gupta
Keyword(s):  
Compressive Loading ◽  
Hot Extrusion ◽  
Optical Microscope ◽  
Deposition Method ◽  
Correlation Studies ◽  
Compressive Response ◽  
Superior Mechanical Properties ◽  
Melt Deposition ◽  
Microstructural Studies ◽  
Strength And Ductility

A ternary micro Mg-0.5Zr-0.4Ce alloy is developed using disintegrated melt deposition method (DMD) followed by hot extrusion. The developed alloy exhibited superior mechanical properties i.e. microhardness, strength and ductility under tensile and compressive loading. In particular, the alloy exhibits excellent ductility (>25%) under both tensile and compressive loading. The mechanisms leading to strengthening and ductilization were examined through microstructural studies involving optical microscope, SEM and XRD texture analysis. Microstructure-property correlation studies are performed to understand these mechanisms.

Numerical and Experimental Investigations on the Expansion Tube Energy Absorber

2012 ◽  
Vol 190-191 ◽  
pp. 115-120 ◽  
Author(s):  
He Mao ◽  
Chang Jie Luo ◽  
Kai He ◽  
Ru Xu Du
Keyword(s):  
Dynamic Compression ◽  
Compressive Loading ◽  
Compressive Load ◽  
Experimental Investigations ◽  
Expansion Tube ◽  
Dynamic Simulations ◽  
Energy Absorber ◽  
Compressive Response ◽  
Crushing Force ◽  
Expansion Tubes

Expansion tube energy absorber is of interest in bumper device on the spacecraft, for example the seat-bumper and its crushing characteristics have shown an excellent performance. This paper contributes to the analysis and investigation of the crushing characteristics of the expansion tube energy absorber, by simulating the response of the 2Al2T4 expansion tube subjected to quasi-static axial compressive loading, using the LS-DYNA finite element code. Corresponding tests were conducted to serve as comparison purpose. Satisfactory level of agreement between simulation and testing results was obtained regarding the main characteristics of the tested expansion tubes such as peak compressive load, energy absorption and the overall compressive response. Formula of the crushing force deduced using plastic mechanic theory was checked. Impact model was also constructed and dynamic simulations were performed to investigate the axial impact response of the expansion tube energy absorber. The simulation results of quasi-static and dynamic compression response of the expansion tube are very similar.

Tensile and Bending Behavior of Sintered Alloys: Experimental Results and Modeling

1998 ◽  
Vol 120 (3) ◽  
pp. 248-255 ◽  
Author(s):  
L. Bertini ◽  
V. Fontanari ◽  
G. Straffelini
Keyword(s):  
Compressive Loading ◽  
Analytical Models ◽  
Uniaxial Tensile ◽  
Stress Strain ◽  
Element Analysis ◽  
Strain Behavior ◽  
Bending Behavior ◽  
Sintered Alloys ◽  
Sintered Materials ◽  
Plastic Stress

Sintered materials show a different stress-strain behavior when subjected to tensile or compressive loading, the response to compression being characterized by a higher elastic modulus, yield stress, and strain hardening rate. These differences tend to make the bending behavior somewhat more complex to analyze, particularly in the elasto-plastic field, as compared to conventional materials, having equal mechanical properties under tension and compression. As a consequence, the use of widely applied test techniques, such as the Three Point Bending (TPB), becomes more difficult for sintered materials, due to the lack of reliable analytical models capable of evaluating elasto-plastic stress-strain distribution as a function of applied load and deflection. In the present investigation, the results of uniaxial tensile-compressive and bending tests conducted on sintered ferrous alloys characterized by different microstructures and porosity are reported and briefly discussed. Then an analytical model, specifically aimed to analyze the elasto-plastic monotonic behavior of a TPB specimen made with a material having different tensile and compressive properties, is presented. Its predictions as regards load-deflection curves and elasto-plastic stress-strain distributions are compared with the results of TPB tests and of numerical (Finite Element) analysis, showing a fairly good agreement.

Compressive Deformation Behaviour of a Closed-Cell Aluminum

2006 ◽  
Vol 510-511 ◽  
pp. 150-153
Author(s):  
Yasuo Yamada ◽  
Takumi Banno ◽  
Zhen Kai Xie ◽  
Cui E Wen
Keyword(s):  
Deformation Mechanism ◽  
Deformation Behaviour ◽  
Compressive Loading ◽  
Peak Stress ◽  
Cell Diameter ◽  
Deformation Bands ◽  
Closed Cell ◽  
A Cell ◽  
Deformation Modes ◽  
Compressive Tests

The mechanical properties of a closed-cell aluminium foam were investigated by compressive tests, and the deformation behaviours of the aluminium foams were studied using Xray microtomography. The results indicate that the deformation of the aluminium foams under compressive loading was localized in narrow continuous deformation bands having widths of order of a cell diameter. The cells in the deformation bands collapsed by a mixed deformation mechanism, which includes mainly bending and minor buckling and yielding. Different fractions of the three deformation modes led to variations in the peak stress and energy absorption for different foam samples with the same density. It was also found that the cell morphology affects the deformation mechanism significantly, whilst the cell size shows little influence.

scholarly journals Size Evolution of Close-in Super-Earths through Giant Impacts and Photoevaporation

2021 ◽  
Vol 923 (1) ◽  
pp. 81
Author(s):  
Yuji Matsumoto ◽  
Eiichiro Kokubo ◽  
Pin-Gao Gu ◽  
Kenji Kurosaki
Keyword(s):  
Radial Profile ◽  
Analytical Models ◽  
Core Mass ◽  
Outer Planets ◽  
The Core ◽  
Size Evolution ◽  
Wide Range ◽  
Mass Fractions ◽  
Giant Impacts ◽  
Impact Phase

Abstract The Kepler transit survey with follow-up spectroscopic observations has discovered numerous super-Earth sized planets and revealed intriguing features of their sizes, orbital periods, and their relations between adjacent planets. For the first time, we investigate the size evolution of planets via both giant impacts and photoevaporation to compare with these observed features. We calculate the size of a protoplanet, which is the sum of its core and envelope sizes, by analytical models. N-body simulations are performed to evolve planet sizes during the giant impact phase with envelope stripping via impact shocks. We consider the initial radial profile of the core mass and the initial envelope mass fractions as parameters. Inner planets can lose their whole envelopes via giant impacts, while outer planets can keep their initial envelopes, because they do not experience giant impacts. Photoevaporation is simulated to evolve planet sizes afterward. Our results suggest that the period-radius distribution of the observed planets would be reproduced if we perform simulations in which the initial radial profile of the core mass follows a wide range of power-law distributions and the initial envelope mass fractions are ∼0.1. Moreover, our model shows that the adjacent planetary pairs have similar sizes and regular spacings, with slight differences from detailed observational results such as the radius gap.

Mechanism of irregular crack-propagation in thermal controlled fracture of ceramics induced by microwave

2020 ◽  
Vol 21 (6) ◽  
pp. 610
Author(s):  
Xiaoliang Cheng ◽  
Chunyang Zhao ◽  
Hailong Wang ◽  
Yang Wang ◽  
Zhenlong Wang
Keyword(s):  
Crack Propagation ◽  
Industrial Application ◽  
Ceramic Materials ◽  
Advanced Technology ◽  
Analytical Models ◽  
Propagation Mechanism ◽  
Unstable Crack ◽  
Fracture Simulation ◽  
Initial Stage ◽  
Controlled Fracture

Microwave cutting glass and ceramics based on thermal controlled fracture method has gained much attention recently for its advantages in lower energy-consumption and higher efficiency than conventional processing method. However, the irregular crack-propagation is problematic in this procedure, which hinders the industrial application of this advanced technology. In this study, the irregular crack-propagation is summarized as the unstable propagation in the initial stage, the deviated propagation in the middle stage, and the non-penetrating propagation in the end segment based on experimental work. Method for predicting the unstable propagation in the initial stage has been developed by combining analytical models with thermal-fracture simulation. Experimental results show good agreement with the prediction results, and the relative deviation between them can be <5% in cutting of some ceramics. The mechanism of deviated propagation and the non-penetrating propagation have been revealed by simulation and theoretical analysis. Since this study provides effective methods to predict unstable crack-propagation in the initial stage and understand the irregular propagation mechanism in the whole crack-propagation stage in microwave cutting ceramics, it is of great significance to the industrial application of thermal controlled fracture method for cutting ceramic materials using microwave.

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