15
© The Author(s), under exclusive license to Springer Nature Switzerland AG 2021
L. Lamberson et al. (eds.), Dynamic Behavior of Materials, Volume 1, Conference Proceedings of the Society
for Experimental Mechanics Series, https://doi.org/10.1007/978-3-030-59947-8_4
Chapter 4
Constitutive Behavior of AA7475-T7351 at High Strain Rate
and Elevated Temperatures
Purnashis Chakraborty, Anoop Kumar Pandouria, M. K. Singha, and Vikrant Tiwari
Abstract The use of Aluminum alloys in the aerospace and defence industries has been rapidly increasing in the last few
decades, due to their high strength-to-weight ratio and high fracture toughness. Mechanical behavior of aluminum alloys at
high temperature and under high strain rate need to be investigated thoroughly to predict the response of structural members
under extreme types of loading conditions like crash, impact, etc. In this chapter, the mechanical behavior of AA7475-T7351
alloy is investigated at elevated temperatures under quasi-static and high strain rate conditions. The present work is carried
out using two distinct setups for loading the specimens quasi- statically and dynamically at a wide range of temperatures.
Cylindrical tensile specimens made of AA7475-T7351 were evaluated under a quasi-static (tensile loading) condition on an
electromechanical universal testing machine (10
−4
–10
−1
s
−1
) subjected to a temperature range 25–250 °C. While Split
Hopkinson Tensile Pressure Bar technique is utilized to obtain the mechanical behavior in the high strain rate range of
500–1500 s
−1
at room temperature. Johnson-Cook constitutive model parameters were evaluated from the experimentally
obtained stress-strain data. The flow stress prediction ability of this phenomenological model is compared with the experimental result in terms of average absolute error and correlation coefficient.
Keywords Constitutive modeling · JC model · AA7475-T7351 · Tensile SHPB
4.1 Introduction
The 7XXX series aluminum alloys are extensively used as structural material in defense, automobile, and aerospace industry
because of their high strength-to-weight ratio, good machinability, and excellent corrosion resistance [1–3]. The use of aluminum alloys in these industries improve the efficiency and performance without any compromise in survivability.
AA7475-T7351 processes highest fracture toughness, low fatigue crack growth, and high strength, which makes it ideal for
use in airframe, fuselage, and wings [4]. Strain rate sensitive dynamic behavior of aluminum alloys is an ongoing hot topic
for several decades. The serviceability of structural component made of high-valued material subjected to high temperature
and rapid loading condition largely depends upon the precision of material characterization. The effects of composition,
temperature, microstructure, and strain rate on the mechanical behavior of aluminum alloys were studied by Higashi et al.
[5]. The mechanical response of aluminum under different strain rate and temperature are reported by number of investigators [6–10]. Oosterkamp et al. [6] studied the response of AA6872-T6 and AA7108-T79 under compressive loading condition at strain rate ranging from 0.1 to 2000 s
−1
. The authors found very small strain rate sensitivity for yield and flow stress
at room temperature. Reyes et al. [7] did tension test on AA7003-T79 and AA7108-T6 at strain rate level 0.1
−3
–10
3
. They
also observed a moderate increase in flow stress with the increase of strain rate. Børvik et al. [8] reported strong positive
strain-rate sensitivity of AA6006-T6 in a wide range of strain rate (0.00078–1200 s
−1
) and temperature (293–573 K). Singh
et al. [9, 10] investigated the tensile and compression behavior of AA6063-T6 in the strain rate range 0.1
−3
–850 s
−1
. Chen
et al. [11] studied the dynamic response of series of extruded aluminum alloys AA6082-T6, AA6060-T6, AA7108-T6, and
AA7003-T6 at a wide range of strain rate. They observed that AA6082-T6 and AA6060-T6 are almost strain rate insensitive,
whereas AA7108-T6 and AA7003-T6 poses a strong strain rate sensitivity. In order to predict the flow stress at high temperature and strain rate, researchers propose various types of constitutive laws. These constitutive models can be broadly divided
P. Chakraborty (*) · A. K. Pandouria · M. K. Singha · V. Tiwari
Department of Applied Mechanics, Indian Institute of Technology Delhi, New Delhi, India
e-mail: maloy@am.iitd.ac.in; tiwariv@am.iitd.ac.in
© The Author(s), under exclusive license to Springer Nature Switzerland AG 2021
L. Lamberson et al. (eds.), Dynamic Behavior of Materials, Volume 1, Conference Proceedings of the Society
for Experimental Mechanics Series, https://doi.org/10.1007/978-3-030-59947-8_4
Chapter 4
Constitutive Behavior of AA7475-T7351 at High Strain Rate
and Elevated Temperatures
Purnashis Chakraborty, Anoop Kumar Pandouria, M. K. Singha, and Vikrant Tiwari
Abstract The use of Aluminum alloys in the aerospace and defence industries has been rapidly increasing in the last few
decades, due to their high strength-to-weight ratio and high fracture toughness. Mechanical behavior of aluminum alloys at
high temperature and under high strain rate need to be investigated thoroughly to predict the response of structural members
under extreme types of loading conditions like crash, impact, etc. In this chapter, the mechanical behavior of AA7475-T7351
alloy is investigated at elevated temperatures under quasi-static and high strain rate conditions. The present work is carried
out using two distinct setups for loading the specimens quasi- statically and dynamically at a wide range of temperatures.
Cylindrical tensile specimens made of AA7475-T7351 were evaluated under a quasi-static (tensile loading) condition on an
electromechanical universal testing machine (10
−4
–10
−1
s
−1
) subjected to a temperature range 25–250 °C. While Split
Hopkinson Tensile Pressure Bar technique is utilized to obtain the mechanical behavior in the high strain rate range of
500–1500 s
−1
at room temperature. Johnson-Cook constitutive model parameters were evaluated from the experimentally
obtained stress-strain data. The flow stress prediction ability of this phenomenological model is compared with the experimental result in terms of average absolute error and correlation coefficient.
Keywords Constitutive modeling · JC model · AA7475-T7351 · Tensile SHPB
4.1 Introduction
The 7XXX series aluminum alloys are extensively used as structural material in defense, automobile, and aerospace industry
because of their high strength-to-weight ratio, good machinability, and excellent corrosion resistance [1–3]. The use of aluminum alloys in these industries improve the efficiency and performance without any compromise in survivability.
AA7475-T7351 processes highest fracture toughness, low fatigue crack growth, and high strength, which makes it ideal for
use in airframe, fuselage, and wings [4]. Strain rate sensitive dynamic behavior of aluminum alloys is an ongoing hot topic
for several decades. The serviceability of structural component made of high-valued material subjected to high temperature
and rapid loading condition largely depends upon the precision of material characterization. The effects of composition,
temperature, microstructure, and strain rate on the mechanical behavior of aluminum alloys were studied by Higashi et al.
[5]. The mechanical response of aluminum under different strain rate and temperature are reported by number of investigators [6–10]. Oosterkamp et al. [6] studied the response of AA6872-T6 and AA7108-T79 under compressive loading condition at strain rate ranging from 0.1 to 2000 s
−1
. The authors found very small strain rate sensitivity for yield and flow stress
at room temperature. Reyes et al. [7] did tension test on AA7003-T79 and AA7108-T6 at strain rate level 0.1
−3
–10
3
. They
also observed a moderate increase in flow stress with the increase of strain rate. Børvik et al. [8] reported strong positive
strain-rate sensitivity of AA6006-T6 in a wide range of strain rate (0.00078–1200 s
−1
) and temperature (293–573 K). Singh
et al. [9, 10] investigated the tensile and compression behavior of AA6063-T6 in the strain rate range 0.1
−3
–850 s
−1
. Chen
et al. [11] studied the dynamic response of series of extruded aluminum alloys AA6082-T6, AA6060-T6, AA7108-T6, and
AA7003-T6 at a wide range of strain rate. They observed that AA6082-T6 and AA6060-T6 are almost strain rate insensitive,
whereas AA7108-T6 and AA7003-T6 poses a strong strain rate sensitivity. In order to predict the flow stress at high temperature and strain rate, researchers propose various types of constitutive laws. These constitutive models can be broadly divided
P. Chakraborty (*) · A. K. Pandouria · M. K. Singha · V. Tiwari
Department of Applied Mechanics, Indian Institute of Technology Delhi, New Delhi, India
e-mail: maloy@am.iitd.ac.in; tiwariv@am.iitd.ac.in