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Effect of Strain Rate on Constitutive Behavior of AA-5052 H34

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Key Engineering Materials
Authors:
Prince Sharma at Indian Institute of Technology Delhi
Prince Sharma
Pradeep S Chandel at TBRL, CHANDIGARH
Pradeep S Chandel
  • TBRL, CHANDIGARH
Vikas Mangla
Vikas Mangla
Vikas Mangla
  • This person is not on ResearchGate, or hasn't claimed this research yet.
Puneet Mahajan at Indian Institute of Technology Delhi
Puneet Mahajan
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Abstract

This paper presents the experimental results to analyze the strain rate sensitivity of aluminium alloy AA-5052 H34. The experiments were carried out under uniaxial tension as well as compression. Tensile tests were carried out with UTM (Zwick Z-250) in the strain rate range of 10-4 to 10-1 s-1 using standard ASTM specimen with gauge length 50mm. Compression tests were carried out in the strain rate range of 10-4 to 103 s-1 using UTM and Split Hopkinson Pressure Bar. Cylindrical specimens of 10mm diameter and 10mm thickness were used for compression experiments. The material showed negative strain rate sensitivity in strain rate from 10-4 to 1 s-1 but showed positive strain rate sensitivity when strain rate increased to 103 s-1. The material was found to be susceptible to Portevin–Le Chatelier effect.
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Effect of Strain Rate on Constitutive Behavior of AA-5052 H34
Prince Sharma
1, a
, Pradeep Chandel
1
, Vikas Mangla
1
Puneet Mahajan
2
and Manjit Singh
1
1
Terminal Ballistics Research Laboratory, Sector 30C, Chandigarh, India
2
Department of Applied Mechanics, IIT Delhi, Hauz Khas, New Delhi, India
a
prince.drdo@gmail.com
Keywords: Negative strain rate sensitivity, Portevin–Le Chatelier effect, Al-Mg alloys
Abstract. This paper presents the experimental results to analyze the strain rate sensitivity of
aluminium alloy AA-5052 H34. The experiments were carried out under uniaxial tension as well as
compression. Tensile tests were carried out with UTM (Zwick Z-250) in the strain rate range of 10
-4
to 10
-1
s
-1
using standard ASTM specimen with gauge length 50mm. Compression tests were carried
out in the strain rate range of 10
-4
to 10
3
s
-1
using UTM and Split Hopkinson Pressure Bar.
Cylindrical specimens of 10mm diameter and 10mm thickness were used for compression
experiments. The material showed negative strain rate sensitivity in strain rate from 10
-4
to 1 s
-1
but
showed positive strain rate sensitivity when strain rate increased to 10
3
s
-1
. The material was found
to be susceptible to Portevin–Le Chatelier effect.
Introduction
AA5052 is one of the higher strength non-heat-treatable and weldable aluminium alloys. It has a
high fatigue strength and excellent corrosion resistance, particularly in marine atmospheres. It is
hardened by cold work. The chemical composition of AA 5052 is given in Table 1. The present
material under investigation was under H34 tempering condition which means that the material was
Strain hardened and then stabilized (1/2 hard). Since AA5052 is frequently used in marine
applications, it can be exposed to high strain rate loading conditions such as ballistic impact. It is
therefore essential to study the effect of strain rate on the constitutive behavior of material.
It has already been established that plastic flow stress is a function of strain, strain rate and
temperature [1]. Although, a large number of constitutive models have been proposed by various
researchers, only a few have been used practically because of the difficulties in determining the
material constants. One of the most popular and frequently used models is Johnson-Cook (J-C)
model [2], which has only five material parameters to be determined experimentally. The
phenomenological model proposed by Johnson-Cook is:
]
*
1][
*
ln1][[
m
TC
n
BA −++=
εεσ
(1)
where
σ
is the plastic flow stress,
ε
is the plastic strain,
*
ε
is a dimensionless plastic strain rate
and T* is a dimensionless homologous temperature. A, B, C, n and m are unknown material
parameters which are to be determined experimentally. The parameters ‘A’ represents the yield
stress, ‘B’ and ‘n’ represents the effect of strain hardening, ‘C’ is the strain rate hardening
coefficient and ‘m’ is the thermal softening coefficient. It can be observed from the Eq. 1 that
plastic flow stress increases with strain rate on a logarithmic scale. So, J-C model assumes positive
strain rate sensitivity for metals which is usually the case for most metals. But this phenomenon is
not true for all metals. Some researchers [3, 4, 5, 6] have reported negative strain rate sensitivity for
aluminium 5*** series aluminium alloys. Although the alloys studied in these references are not
exactly the same as in the present study, but they all have magnesium as the same major alloying
element.
Key Engineering Materials Online: 2013-01-11
ISSN: 1662-9795, Vols. 535-536, pp 60-63
doi:10.4028/www.scientific.net/KEM.535-536.60
© 2013 Trans Tech Publications Ltd, Switzerland
All rights reserved. No part of contents of this paper may be reproduced or transmitted in any form or by any means without the written permission of Trans
Tech Publications Ltd, www.scientific.net. (Research Gate for subscription journals-11/02/24,13:20:51)
... The material and thermal properties and JC parameters of each target material are listed in Tables 2 and 3 , respectively. The JC parameters were obtained from extant studies [6,[41][42][43][44][45][46][47][48][49] . The target material was modeled into discrete elements so that the element size was gradually decreased with approaching impact site. ...
... Therefore, these results clearly indicate that Eqs. (35) and (42) are valid up to 60 m/s when the indentation sizes formed by the impactors 1 and 2 are comparable to each other. In the case of the impact velocity of 180 m/s, some errors might be caused by the assumptions expressed as Eqs. ...
... In the case of the impact velocity of 180 m/s, some errors might be caused by the assumptions expressed as Eqs. (35) and (42) due to the concentration of the ̄ at the edge of the indentation. However, as shown in Fig. 6 , the distribution of the ̄ , except the vicinity of the edge at 180 m/s, almost corresponds to that at other impact velocities. ...
Simple estimation method for strain rate sensitivity based on the difference between the indentation sizes formed by spherical-shaped impactors
Article
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The Johnson-Cook (JC) flow stress model is widely used in finite element analysis (FEA) in various fields to express the deformation behavior of metallic materials under high strain rate conditions. There is a need to facilitate an easier estimate of the JC parameter C, which is a material constant in the JC model associated with strain rate sensitivity. In this study, a simple estimation method for the JC parameter C, based on the difference between the indentation sizes formed by two spherical-shaped impactors, was proposed. The proposed method allows us to estimate the JC parameter C only by measurement of the indentation sizes formed via a high-velocity impact test, a drop impact test, or an indentation test. The fundamental equation was theoretically derived based on the energy conservation during the impact process of the impactor and the expanding cavity model, combined with the JC model and the equation of thermal conduction. To validate the proposed method, FEA was conducted using ten types of target materials under five impact velocity conditions, from 6 × 10⁻⁶ to 180 m/s. Based on the indentation depths obtained from FEA, the JC parameter C was estimated and compared with that input into FEA. As a result, it was confirmed that the estimated C is in agreement with that input into FEA within the relative errors of 10% under all impact velocity and target material conditions, except the target material of Ti6Al4V. From the results, it was demonstrated that the proposed method can easily estimate the JC parameter C, that is, the strain rate sensitivity, in the wide range of strain rate from 10² to 10⁵ s⁻¹.
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... They observed that by increasing the loading rate, an increase would be seen in the yield stress, the ultimate tensile strength, and the elongation. Sharma et al. 16 found the effect of the loading rate on mechanical properties of the AA-5052-H34 aluminum alloy. They observed that the ultimate tensile strength and the elongation decreased by increasing the loading rate. ...
Sensitivity analysis of mechanical properties and ductile/brittle behaviors in aluminum‐silicon alloy to loading rate and nano‐particles, considering interaction effects
Article
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Aluminum‐silicon alloys have been widely used in automotive industries. To know mechanical properties of such materials is essential for engineers to have a superior design for components. Therefore, in this article, the sensitivity analysis of mechanical and fracture features in the aluminum alloy has been performed to find the effect of the loading rate and nano‐particles. For this objective, tensile tests were performed on casting standard specimens. Then, obtained experimental data were analyzed by the Minitab software, using the factorial method. In addition, the interaction between the effect of the loading rate and the addition of nano‐particles, on mechanical properties and ductile/brittle behaviors, was also investigated. Obtained results indicated that the yield stress, the elastic modulus and the elongation were sensitive to the interaction of both factors (the multiply of the nano‐particle addition and the loading rate). Besides, the fracture surface illustrated that by increasing the loading rate and the addition of nano‐particles, the brittleness of the material increased.
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Expanding Cavity Model Combined With Johnson–Cook Constitutive Equation for the Dynamic Indentation Problem
Article
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The indentation formed on a metallic component by the high-velocity impingement of a small object can fracture the component, and this is known as foreign object damage. In this type of dynamic indentation, it is necessary to consider the effects of work hardening, strain rate hardening, and thermal softening in the impinged material. In this study, in order to consider these effects, the expanding cavity model based on a spherical formulation is modified via the Johnson–Cook constitutive equation for the dynamic indentation problem. Additionally, an equation is developed based on energy conservation and the modified expanding cavity model to predict the size of the indentation formed by an impingement of a solid sphere (EPIS). The distributions of equivalent plastic strain, equivalent plastic strain rate, temperature, and equivalent von Mises stress obtained via the expanding cavity model were in good agreement with the data obtained from the finite element analysis. Furthermore, it was demonstrated that EPIS accurately predicted the indentation size formed on various metallic materials at several impingement velocities in the range of 50–300 m/s. Consequently, EPIS can be effectively applied to an impingement problem of a hard sphere onto a sufficiently thick ductile material within 300 m/s without any help of FEA.
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Thermo-Mechanical Behavior and Bulk Texture Studies on AA5052-H32 Under Dynamic Compression
Article
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  • MAT SCI ENG A-STRUCT
In this paper, the thermo-mechanical response of commercially important AA5052-H32 alloy was investigated under dynamic compression over a wide range of strain rates and temperatures. Very high strain rate experiments were conducted using a miniaturized Kolsky bar to reach a peak strain rate of 105 s−1. Dynamic flow stress was found to increase by 180 MPa at this peak strain rate, which was twice the value obtained under quasi-static loading. At room temperature the material showed negative strain rate sensitivity under quasi-static loading with serrated flow behavior and positive strain rate sensitivity under dynamic loading. The strain rate transition occurred around a strain rate of 6000 s−1. Furthermore, thermal softening under dynamic compression was investigated up to a temperature of 0.75Tm at a constant strain rate. It was found that the flow stress decreased linearly with temperature indicating that thermal activation dominates the deformation over this temperature range. Detailed study of microstructure of the deformed specimens showed that the texture development was less under high strain rate as well as high temperature loading when compared to the quasi-static room temperature deformation. Based on the stress vs. strain curves, a comparison between two constitutive models, Johnson-Cook and Voyiadjis-Almasri, was made to capture the flow stress behavior as a function of strain rate.
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Hopkinson bar experimental technique: A critical review
Article
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A critical review of three classic papers by B Hopkinson, RM Davies, and H Kolsky, and the state-of-the-art in Hopkinson bar experimental techniques is presented. The validity and applicability of the assumption made in the 1D Hopkinson bar theory are discussed. Fundamentals of the Hopkinson bar experimental procedure are outlined including bar calibration, specimen design, pulse shaping, and data analysis following the essential dispersion correction methodology. Additional data tables necessary for dispersion correction are provided to cover a wide range of Poisson's ratio. In addition to the elastic-plastic metals, methodologies for soft and hard materials are also discussed. This paper provides the necessary information for conducting a Hopkinson bar experiment and analyzing the experimental data. This review article cites 61 references.
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The morphology of Portevin-Le Chatelier bands: Finite element simulation for Al-Mg-Si
Article
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  • ACTA MATER
A constitutive model for dynamic strain ageing together with a three-dimensional finite element analysis were used to simulate discontinuous yielding behaviour associated with the Portevin–Le Chatelier effect. The deformation behaviour of both flat and round specimens of a dynamically strain ageing material was simulated, utilizing constitutive parameters for an Al–Mg–Si alloy. Finite element simulations showed the occurrence of propagative zones of localized deformation and provided insight into the strain rate distribution in the zones, characterized by a sharp strain rate peak. The localized deformation zones in round specimens were found to have a diffuse double cone morphology. Propagative deformation bands in flat strip specimens were planar and inclined with respect to the tensile axis by approximately 35°. The dependence of the morphology of the localized deformation zones on specimen geometry and deformation conditions, as well as the serrated stress–time curves obtained, are in good agreement with experimental measurements in Al–Mg–Si.
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Influences of strain rate and grain size on yield and serrated flow in commercial Al-Mg alloy 5086
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Much attention has been paid to the rather special stress-strain characteristics of Al-Mg alloys. Beginning with the pioneering work of Portevin and LeChatelier in 1923, the focus has been on the appearance of tensile band-type deformation markings that are observed coincident with the appearance of serrated flow in stress-strain curves. The serrations are the result of dynamic strain aging (DSA). A major influence of the DSA phenomenon is to produce both a higher flow stress and, very importantly, greater strain hardening at lower strain rates than for higher ones at which serrations do not appear. Physically-based constitutive equations, for example, of Zerilli-Armstrong type, that are derived for thermally-activated dislocation-lattice or dislocation-dislocation interactions, are susceptible to interference from DSA. For this reason, clarification of the importance of strain aging in accounting for laboratory tests of the stress-strain behavior of the alloy has been investigated. Of special interest was the solute influence on the combined yield and strain hardening behavior.
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Deep drawability of type 5083 aluminium–magnesium alloy sheet under various conditions of temperature and forming speed
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The effects of forming speed and temperature on the deep drawability were investigated for a fine-grain Al–Mg alloy (5083-O) sheet by performing cylindrical deep drawing tests at various forming speeds (0.2–500 mm min−1) at die temperatures of 293–453 K (the die was heated, whilst the punch was water-cooled during the tests). In order to examine the mechanical properties of this Al–Mg alloy sheet, uniaxial tensile tests were also performed at a wide range of strain rates of 5.6×10−5–5.3×10 s−1 at various temperatures from 273 to 523 K. It was found that the limiting drawing ratio (LDR) mostly increases with increasing die temperature, because the deformation resistance in flange shrinkage decreases with temperature rise. The LDR becomes lower with increasing forming speed at all temperatures, since the flow stress of the heated blank (at the flange) increases with increasing strain rate, and moreover, the cooled blank at the punch corner becomes less ductile.
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Flow and fracture characteristics of aluminium alloy AA5083-H116 as function of strain rate, temperature and triaxiality
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This paper presents a part of an on-going study of light-weight shelters made of aluminium alloy AA5083–H116. A necessary prerequisite for numerical simulations of impact behaviour of such shelters is a calibrated numerical model. Slightly modified versions of the two Johnson–Cook models describing flow stress and fracture strain are applied. In addition to ordinary quasistatic tests with smooth specimens, these models demand tests at elevated temperatures and strain rates, and different triaxiality ratios. All tests to be presented in this paper are uniaxial tension tests performed in servohydraulic test machines or a Split–Hopkinson bar. The test programme involves approximately 100 specimens, and includes coupons from three different directions of the plate material, thereby taking account for the anisotropy. The AA5083 alloy is susceptible to dynamic strain ageing, and this phenomenon is shown to result in serrated stress–strain curves and negative strain rate sensitivity for a rather wide range of strain rates. In particular, the specimen geometry seems to have a strong influence on the serrated curves. The calibration shows that the Johnson–Cook–type models represent most of the observed material behaviour reasonably well, although the negative strain rate sensitivity is not adequately described.
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