Experiments and Numerical Simulations on Thin Metallic Plates Subjected to an Explosion

Submitted to a sudden and a transient loading, a metallic structure quickly evolves toward viscoplastic behavior, including high strain rates. After generalities about the specific loading and the description of the experimental setup, a numerical simulation based on the F.E.M. using an explicit scheme is presented. Three different constitutive laws are discussed: the Perzyna, the Bodner-Partom, and that of Chaboche. The identification of constitutive parameters is made using unidirectional tests on the studied material (aluminum alloy 5754). A comparison between numerical simulations and experiments shows that the method is relevant.

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AN IMAGE BASED INERTIAL IMPACT TEST TO EXTRACT VISCOELASTIC CONSTITUTIVE PARAMETERS

10.12783/asc36/35811 ◽

2021 ◽

Author(s):

ANDREW MATEJUNAS ◽

LLOYD FLETCHER ◽

LESLIE LAMBERSON

Keyword(s):

Strain Rate ◽

Polymer Matrix ◽

Mechanical Response ◽

High Strain ◽

High Rate ◽

Strain Rates ◽

High Strain Rates ◽

Full Field ◽

Viscoelastic Parameters ◽

Constitutive Parameters

Polymer matrix composites often exhibit a strong strain rate dependance in their mechanical response. In many of these materials, the viscoelastic behavior of the polymer matrix drives the rate dependence in the composite, however identifying these parameters at high strain rate presents a significant challenge. Common high-rate material characterization techniques such as the Kolsky (split-Hopkinson pressure) bar require a large test matrix across a range of strain rates. Kolsky bars also struggle to identify constitutive parameters prior to the yield due to inertial effects and the finite period of time required to reach force equilibrium. The Image Based Inertial Impact (IBII) test has been successfully used to identify linear elastic constitutive behavior of composites at high strain rates, but, to date, has only been used to extract constitutive properties at a single nominal strain rate in each test. Here, we propose an adaptation of the IBII test to identify viscoelastic parameters at high strain rates using full-field displacement data and the nonlinear virtual fields method (VFM). We validate the technique with finite element simulations of an IBII test on a model viscoelastic material that is characterized with a Prony series formulation of the generalized Maxwell model. The nonlinear VFM is then used to extract the Prony pairs for dynamic moduli and time constants from the full-field deformation data. The nonlinear viscoelastic identification allows for characterization of the evolution of mechanical response across a range of strain rates in a single experiment. The experimentally identified viscoelastic parameters of the matrix can then be used to predict the behavior of the composite at high strain rates. This approach will also be validated experimentally using a single-stage gas-gun to characterize the high-rate viscoelastic response of PMMA.

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Approaches to Synchronise Conventional Measurements with Optical Techniques at High Strain Rates

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.70.75 ◽

2011 ◽

Vol 70 ◽

pp. 75-80 ◽

Cited By ~ 3

Author(s):

Duncan A. Crump ◽

Janice M. Dulieu-Barton ◽

Marco L. Longana

Keyword(s):

Polymer Composites ◽

High Speed ◽

High Strain ◽

Image Correlation ◽

Test Machine ◽

Strain Rates ◽

High Strain Rates ◽

Optical Techniques ◽

Specific Loading ◽

Military Applications

Polymer composites are increasingly being used in high-end and military applications, mainly due to their excellent tailorability to specific loading scenarios and strength/stiffness to weight ratios. The overall purpose of the research project is to develop an enhanced understanding of the behaviour of fibre reinforced polymer composites when subjected to high velocity loading. This is particularly important in military applications, where composite structures are at a high risk of receiving high strain rate loading, such as those resulting from collisions or blasts. The work described here considers an approach that allows the collection of full-field temperature and strain data to investigate the complex viscoelastic behaviour of composite material at high strain rates. To develop such a data-rich approach digital image correlation (DIC) is used to collect the displacement data and infra-red thermography (IRT) is used to collect temperature data. The use of optical techniques at the sampling rates necessary to capture the behaviour of composites subjected to high loading rates is novel and requires using imaging systems at the far extent of their design specification. One of the major advantages of optical techniques is that they are non-contact; however this also forms one of the challenges to their application to high speed testing. The separate camera systems and the test machine/loading system must be synchronised to ensure that the correct strain/temperature measurement is correlated with the correct temporal value of the loading regime. The loading rate exacerbates the situation where even at high sampling rates the data is discrete and therefore it is difficult to match values. The work described in the paper concentrates on investigating the possibility of the high speed DIC and synchronisation. The limitations of bringing together the techniques are discussed in detail, and a discussion of the relative merits of each synchronisation approach is included, which takes into consideration ease of use, accuracy, repeatability etc.

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Phenomenological Theories of Elastoplasticity and Strain Localization at High Strain Rates

Applied Mechanics Reviews ◽

10.1115/1.3121388 ◽

1992 ◽

Vol 45 (3S) ◽

pp. S19-S45 ◽

Cited By ~ 51

Author(s):

Sia Nemat-Nasser

Keyword(s):

Strain Localization ◽

Finite Deformation ◽

High Strain ◽

Large Strain ◽

Kinematic Hardening ◽

Stress Deviator ◽

Strain Rates ◽

High Strain Rates ◽

Plastic Spin ◽

Constitutive Parameters

In this paper certain fundamental concepts underlying the phenomenological theories of elastic-plastic deformations at finite strains and rotations are presented, and some of the commonly discussed theories are summarized, emphasizing the constitutive parameters which influence strain localization and material instability often observed in finite deformation of ductile materials. Particular attention is paid to the thermodynamic basis of inelastic deformation. Conditions for the existence of inelastic potentials are discussed. The results are presented in terms of a general material strain and its conjugate stress, and then specialized for particular applications, emphasizing quantities and theories which are reference- and strain measure-independent. Rate-independent and rate-dependent elastoplasticity relations are developed, starting from a finite deformation version of the J2-plasticity with isotropic and kinematic hardening, and leading to theories which include dilatancy, pressure sensitivity, frictional effects, and the noncoaxiality of the plastic strain and the stress deviator. A class of commonly used deformation plasticity theories is then examined and its relation to nonlinear elasticity is discussed. The question of plastic spin, and its relation to the decomposition of the deformation gradient into elastic and plastic constituents, is reviewed in some detail, and it is shown that this decomposition yields explicit relations which uniquely define all spins in terms of the velocity gradient and the elastic and plastic deformation rates, hence requiring no additional constitutive relations for the plastic spin. The phenomenon of strain localization at high strain rates is illustrated and discussed, and a series of numerical results are given. Finally, a recent breakthrough in elastoplastic explicit computational algorithms for large-strain, large-strain-rate problems is briefly reviewed.

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Mechanical Properties of 35CrMoA Steel at High Strain Rate Loading

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.791-793.338 ◽

2013 ◽

Vol 791-793 ◽

pp. 338-342

Author(s):

Wen Jun Hu ◽

Xi Cheng Huang ◽

Fang Ju Zhang ◽

Li Ming Wei

Keyword(s):

Mechanical Properties ◽

Strain Rate ◽

High Strain ◽

Strain Rate Range ◽

Strain Rates ◽

Experimental Apparatus ◽

Metallurgical Structure ◽

Fracture Appearance ◽

Strain Rate Loading ◽

Constitutive Parameters

The tensile properties of alloy steel 35CrMoA were measured by dynamic tension experimental apparatus, and the stress-strain curves of the material at strain rate range from 10-2/s to 103/s were obtained. The fracture appearance and metallurgical structure were observed for the recovered specimens. The influence of strain rates on mechanical properties and microstructure of the 35CrMoA steel was analyzed. Based on the experimental data of mechanical properties, the JC constitutive parameters were fitted for 35CrMoA.

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Solid Solution Effects and Deformation Micros trueture of Shock-Loaded Iron Manganese Alloys

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100069090 ◽

1970 ◽

Vol 28 ◽

pp. 420-421

Author(s):

A. Christou ◽

J. V. Foltz ◽

N. Brown

Keyword(s):

Solid Solution ◽

Shock Loading ◽

High Strain ◽

Local Stress ◽

Strain Rates ◽

Local Stress Concentration ◽

Bcc Metals ◽

Manganese Alloys ◽

Iron Manganese ◽

Transmission Microscope

In general, all BCC transition metals have been observed to twin under appropriate conditions. At the present time various experimental reports of solid solution effects on BCC metals have been made. Indications are that solid solution effects are important in the formation of twins. The formation of twins in metals and alloys may be explained in terms of dislocation mechanisms. It has been suggested that twins are nucleated by the achievement of local stress-concentration of the order of 15 to 45 times the applied stress. Prietner and Leslie have found that twins in BCC metals are nucleated at intersections of (110) and (112) or (112) and (112) type of planes.In this paper, observations are reported of a transmission microscope study of the iron manganese series under conditions in which twins both were and were not formed. High strain rates produced by shock loading provided the appropriate deformation conditions. The workhardening mechanisms of one alloy (Fe - 7.37 wt% Mn) were studied in detail.

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