Numerical study of dynamic behavior of foams subjected to high- to hyper-velocity impact

2019 ◽  
Author(s):  
Xiaotian Zhang ◽  
Ruiqing Wang ◽  
Q.M. Li
Keyword(s):  
Dynamic Behavior ◽  
Impact Velocity ◽  
Foam Cell ◽  
Numerical Study ◽  
Failure Process ◽  
Failure Mechanisms ◽  
Hypervelocity Impact ◽  
Deformation And Failure ◽  
Set Up ◽  
The Impact

Abstract Hypervelocity tests and numerical studies have been reported in the literature for aluminum foam to show its potential applications in spacecraft shielding against space debris based on “shielding set-up”. Meanwhile the “forward impact” set-up has been widely reported in the literature to study the dynamic behavior of the foam materials in the range of low to intermediate impact velocities. This paper extends the forward impact to high- and hyper-velocity impacts to understand the dynamic deformation and failure mechanisms based on numerical simulation. The focused impact velocity range is from about 1km/s to 6km/s. The cell-based numerical model of the foam material is used along with the Smoothed Particle Hydrodynamics (SPH) method to simulate the deformation and the failure process. The failure of the foam materials in the range of intermediate to high impact velocities is related to the plastic yielding and crushing of the foam cell, while that in the hypervelocity impact regime is related to the cell material erosion. Dynamic effects in different impact velocity ranges also lead to shock and strain-rate effects. Understanding of the dependence of the deformation/failure mechanisms on the impact velocity helps to determine the application of foam materials in the relevant range of impact velocities.

Numerical Study on Influence of Joint Characters on Rock Mechanical Parameters

2011 ◽  
Vol 201-203 ◽  
pp. 2909-2912
Author(s):  
Yan Feng Feng ◽  
Tian Hong Yang ◽  
Hua Wei ◽  
Hua Guo Gao ◽  
Jiu Hong Wei
Keyword(s):  
Rock Mass ◽  
Compression Strength ◽  
Numerical Study ◽  
Process Analysis ◽  
Failure Process ◽  
Deformation Modulus ◽  
Rock Joints ◽  
Structured Surfaces ◽  
Trace Length ◽  
The Impact

Rock mass is the syntheses composed of kinds of structure and structured surfaces. The joint characters is influencing and controlling the rock mass strength, deformation characteristics and rock mass engineering instability failure in a great degree. Through using the RFPA2D software, which is a kind of material failure process analysis numerical methods based on finite element stress analysis and statistical damage theory, the uniaxial compression tests on numerical model are carried, the impact of the trace length of rock joints and the fault throws on rock mechanics parameters are studied. The results showed that with the gradual increase of trace length,compression strength decreased gradually and its rate of variation getting smaller and smaller, the deformation modulus decreased but the rate of variation larger and larger; with the fault throws increasing, the compression strength first increases and then decreases, when the fault throw is equal to the trace length, the deformation modulus is the largest. When the joint trace length is less than the fault throw, the rate of the deformation modulus is greater than that of trace length, but the deformation modulus was not of regular change.

scholarly journals Cratering for Impact of Hypervelocity Projectiles into Granite Targets within a Velocity Range of 1.91–3.99 km/s: Experiments and Analysis

2020 ◽  
Vol 10 (4) ◽  
pp. 1393
Author(s):  
Xiaofeng Wang ◽  
Jingbo Liu ◽  
Biao Wu ◽  
Defeng Kong ◽  
Jiarong Huang ◽  
...  
Keyword(s):  
Impact Velocity ◽  
Scaling Law ◽  
Density Ratio ◽  
Hypervelocity Impact ◽  
Experimental Results ◽  
Tungsten Alloy ◽  
Regression Equations ◽  
Velocity Range ◽  
Predicted Values ◽  
The Impact

To understand and analyze crater damage of rocks under hypervelocity impact, the hypervelocity impact cratering of 15 shots of hemispherical-nosed cylindrical projectiles into granite targets was studied within the impact velocity range of 1.91–3.99 km/s. The mass of each projectile was 40 g, and the length–diameter ratio was 2. Three types of metal material were adopted for the projectiles, including titanium alloy with a density of 4.44 g/cm3, steel alloy with a density of 7.81 g/cm3, and tungsten alloy with a density of 17.78 g/cm3. The projectile–target density ratio (ρp/ρt) ranged from 1.71 to 6.86. The depth–diameter ratios (H/D) of the craters yielded from the experiments were between 0.14 and 0.24. The effects of ρp/ρt and the impact velocity on the morphologies of the crater were evaluated. According to the experimental results, H/D of craters is negatively correlated with the impact velocity, whereas the correlation between H/D and ρp/ρt is weak positive. The crater parameters were expressed as power law relations of impact parameters by using scaling law analysis. The multiple regression analysis was utilized to obtain the coefficients and the exponents of the relation equations. The predicted values of the regression equations were close to the experimental results.

The Impact Analysis of Ground Stability Caused by Exploiting Underground Coal

2011 ◽  
Vol 243-249 ◽  
pp. 3147-3150
Author(s):  
Shu Xian Liu ◽  
Xiao Gang Wei ◽  
Shu Hui Liu ◽  
Li Ping Lv
Keyword(s):  
Numerical Simulation ◽  
Coal Mining ◽  
Impact Analysis ◽  
Shear Failure ◽  
Failure Process ◽  
Wall Rock ◽  
Strong Impact ◽  
Element Analysis ◽  
Deformation And Failure ◽  
The Impact

Disaster caused by exploiting underground coal is due to original mechanical equilibrium of underground rock has been destroyed when underground coal is exploited. And Stress redistribution and stress concentration of wall rock in the goaf happened too. As many complex factors exist such as complex structures of ground, multivariate stope boundary conditions, many stochastic mining factors and so on, it is difficult to evaluate the damage of the geological environment caused the excavation by surrounding underground coal accurately. Besides that, the coexistence of continuous and discontinuous of deformation and failure of wall rock make a strong impact on the ground, and the co-exist of tension, compression and shear failure also pay a great deal contribution to the destroy. Due to the mechanical property and deformation mechanism of goaf are complex , changeable, nonlinear and probabilistic, which changes with in space and time dynamically, it can not be studied analytically by the classical mathematical model and the theory of mechanics computation. Through finite element analysis software ABAQUS, a numerical simulation of the process of underground coal mining have been made. After make a research of the simulation process, it shows the change process of stress environment of wall rock and deformation and failure process of rock mass during the process of coal mining. The numerical simulation of the process can provide theoretical basis and technical support to the protection and reinforcement of laneway the process of coal excavation. Besides that, it also provides a scientific basis and has a great significance to reasonable Excavation and control of mind-out area.

A New Formula for Predicting the Crater Size of a Target Plate Produced by Hypervelocity Impact

2019 ◽  
Vol 17 (01) ◽  
pp. 1844004 ◽  
Author(s):  
Z. L. Zhang ◽  
T. Ma ◽  
D. L. Feng ◽  
M. B. Liu
Keyword(s):  
Impact Velocity ◽  
Hypervelocity Impact ◽  
Model Parameters ◽  
Target Plate ◽  
Sph Method ◽  
Crater Size ◽  
Steady Stage ◽  
Kernel Gradient Correction ◽  
Simulation Results ◽  
The Impact

Hypervelocity impact (HVI) of materials is usually associated with large deformations of structures, big craters, phase transition of materials and scattered debris cloud. It is difficult to predict the size of damage caused by HVI while comprehensively considering all the influencing factors for both experimental and numerical approaches. In this paper, the HVI process is modeled by using the smoothed particle hydrodynamics (SPH) method with Kernel Gradient Correction (KGC) technique. The SPH method with KGC (SPH-KGC) has been demonstrated to have better accuracy and reliability for modeling the HVI problems in our recent work. In this paper, the SPH-KGC method is used to investigate the HVI of a sphere on a target plate. The sizes of the craters produced by HVI at different initial impact velocities are obtained, and the variation of the crater size over the impact velocity is studied. According to the present simulation results, a critical velocity is identified and the increase of the crater size versus the initial impact velocity can be divided into two stages, a varying stage and a steady stage. A new empirical formula is presented for predicting the crater size of the target plate produced by HVI. This formula comprehensively considers the influence of many model parameters, such as the densities of the materials of both the projectile and the target, the sound speed of the target material, the diameter of the projectile and the thickness of the target plate. The results obtained by the presented prediction formula agree well with the experimental observations as well as the present SPH simulation results.

Numerical Study on High-Speed Impact Between a Water Droplet and a Deformable Solid Surface

2012 ◽  
Author(s):  
Yongqiang Han ◽  
Yonghui Xie ◽  
Di Zhang
Keyword(s):  
Solid Surface ◽  
Water Droplet ◽  
High Speed ◽  
Numerical Study ◽  
Contact Radius ◽  
Deformable Solid ◽  
Theoretical Predictions ◽  
Steam Turbine Blade ◽  
Set Up ◽  
The Impact

In this study an axisymmetric model is set up to study the impact of a spherical water droplet with a planar deformable solid surface using the Lagrange-Euler coupling method which is based on a penalty formulation. The diameter and velocity of the droplet are 0.4 mm and 500 m/s respectively, while the solid is a kind of steam turbine blade material. The generated pressure distribution in the droplet and its variation with time, the formation of lateral jet, the deformation and stress distribution in the solid are obtained and investigated. It is shown that the compressibility of the droplet and the solid plays a significant role during the impact. The water-hammer pressure and the maximum contact edge pressure are calculated and in good agreement with the existing theoretical predictions. The calculated contact radius for shock departure is larger than that of the conventional theoretical prediction, which is analyzed and attributable to the radial motion of the liquid in the compressed region. The formation of the high-speed lateral jet is calculated and the time for the observable jetting is much later than that of the shock departure. This delay is discussed and the reason needs more research. The pressure of the contact edge region remains highest even after a considerable time of shock departure and lateral jetting. In the mean time, a saucer-shaped depression is generated in the center of the impact. The stress waves in solid move faster even before shock departure in the liquid. This causes disturbance of the solid surface before the high-speed lateral jetting and provides site for the scouring action of it, and subsequently may cause material damage and erosion.

scholarly journals Dynamic crack arrest capability of some metallic alloys and polymers

2018 ◽  
Vol 183 ◽  
pp. 02002
Author(s):  
Gunasilan Manar ◽  
Norazrina Mat Jali ◽  
Patrice Longère
Keyword(s):  
Impact Velocity ◽  
High Speed ◽  
Shear Failure ◽  
Failure Process ◽  
Shear Bands ◽  
Ductile Failure ◽  
Crack Arrest ◽  
Dynamic Crack ◽  
Impact Tests ◽  
The Impact

We are here interested in the crack arrest capability under impact loading of metals and polymers used as structural and/or protection materials in aerospace engineering. Kalthoff and Winkler-type impact tests are carried out to that purpose on high strength AA7175 aluminum alloy and shock resistant polymethyl methacrylate (PMMA). Impact tests are carried out at impact velocities ranging from 50 m/s to 250 m/s and high speed camera is used to record the different steps of the failure process. For AA7175, early Mode II shear failure followed by late Mode I opening failure are seen. The premature ductile failure of the alloy is shown to result from a preceding stage of dynamic localization in the form of adiabatic shear bands. Impact tests on shock-resistant PMMA evidence the brittle feature of the material failure. It is notably shown that the higher the impact velocity (in the range 50-100 m/s) the larger the number of fragments. Moreover, depending on the impact velocity, changes in the crack path and thus in the mechanisms controlling the PMMA dynamic fracture can be seen.

High Velocity Compaction : Overview of Materials, Applications and Potential

2007 ◽  
Vol 534-536 ◽  
pp. 293-296 ◽  
Author(s):  
Florence Dore ◽  
Ludovic Lazzarotto ◽  
Stephane Bourdin
Keyword(s):  
Impact Velocity ◽  
High Velocity ◽  
New Technology ◽  
Machining Process ◽  
Powder Materials ◽  
Component Shape ◽  
High Velocity Compaction ◽  
Set Up ◽  
The Impact ◽  
Sintered Materials

Since 2000, CETIM has been equipped with a High Velocity Press that can deliver up to 5 shots per second with each blow accurately set up (up to 20000J) thanks to the impact velocity regulation (up to 11m.s-1). Through different projects, CETIM and its scientific and industrial partners have evaluated the potential of this new technology in terms of materials and component shape. Various kinds of powder materials were studied: metals, ceramics and polymers. The HVC process was used with success to manufacture gears, large parts and multilevel components. More than, the green machining process that enables shapes to be produced that would otherwise be impossible to compact is improved by the high density of HVC parts and it is also an opportunity to produce components with very hard sintered materials.

Experimental and numerical study of multi-scale tensile behaviors of Kevlar® 49 fabric

2016 ◽  
Vol 51 (17) ◽  
pp. 2449-2465 ◽  
Author(s):  
Deju Zhu ◽  
Xiaotong Zhang ◽  
Yunfu Ou ◽  
Mengying Huang
Keyword(s):  
Weibull Distribution ◽  
Numerical Study ◽  
Failure Process ◽  
Probabilistic Approach ◽  
Impact Resistance ◽  
Gage Length ◽  
Deformation And Failure ◽  
Size Scale ◽  
Multi Scale ◽  
Structural Size

Kevlar® 49 fabrics have excellent performances such as high elastic modulus and high impact resistance, which are widely used in ballistic systems, aerospace, fabric reinforced composite materials and other fields. The present work studied the multi-scale mechanical behaviors of Kevlar® 49 in the forms of fiber, yarn and fabric subjected to uniaxial tension. The experimental results showed that the material mechanical properties are dependent on structural size scale and gage length of samples. The tensile strengths decrease with increasing gage length and structural size scale from fiber to yarn, and to fabric, and follow Weibull distribution by conducting statistical analysis, which is used to quantify the degree of variability in the tensile strengths of fiber and yarn with different gage lengths. At last, user-defined subroutines (UMAT) in ANSYS were implemented to simulate the tensile behaviors of single yarn and fabric by using the constitutive models of fiber and yarn, respectively, which considered their Weibull distribution in tensile strength. This probabilistic approach can simulate the multi-scale tensile behaviors of Kevlar® 49 accurately and reveal the mechanisms of deformation and failure process based on the various size scales. This approach is also applicable to study the multi-scale behaviors of other fabrics once their properties and Weibull parameters are determined.

Numerical Study on the Impact of Revising the Rainstorm Intensity Formula on the Storm Flood Disaster Prediction in Huinan, Pudong District

2018 ◽  
Vol 7 (1) ◽  
pp. 19 ◽  
Author(s):  
Jing HUANG
Keyword(s):  
Overland Flow ◽  
Numerical Study ◽  
Flood Disaster ◽  
Rainfall Runoff ◽  
Pipe Networks ◽  
Mike Flood ◽  
Drainage Pipe ◽  
Set Up ◽  
The Impact ◽  
Disaster Prediction

The numerical model by MIKE FLOOD software has been set up with coupled the rainfall runoff sub-model and underground network sub-model by MIKE URBAN software and the overland flow sub-model by MIKE 21 software to simulate the storm flood in Huinan, Pudong District. After the calibration and validation, the model is applied to study the impact of revising the rainstorm intensity formula on the local storm flood disaster prediction. And the conclusions are obtained: after the formula revised, the time to appear the maximum waterlogging area would be delayed, and the local storm flood disaster would worsen under the current drainage pipe networks, i.e., the overland flood range and its depth would slightly increase.

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