Physical constitutive equations for plastic deformation of FCC metals subjected to high strain rate loading

2015 ◽  
Vol 232 (2) ◽  
pp. 106-120 ◽  
Author(s):  
E Etemadi ◽  
J Zamani ◽  
M Jafarzadeh
Keyword(s):  
High Strain Rate ◽  
Strain Rate ◽  
Entropy Generation ◽  
Constitutive Equations ◽  
High Strain ◽  
Velocity Shear ◽  
Viscous Drag ◽  
Shear Strain Rate ◽  
Face Centered Cubic ◽  
Fcc Metals

This paper develops a new physically based model to investigate face centered cubic (FCC) metals and alloys under high strain rate loadings (\gt104 s−1) which includes kinematics and constitutive equations for the propagation of elastic and steady plastic waves. The model’s formulations are based on the rate of the conservation energy law that includes the rate of the input energy, internal energy, and entropy generation. This formulation is obtained by incorporating the viscous drag effects and associating the entropy generation to the generation, glide, and annihilation of dislocations. The model is used for 6061-T6 aluminum alloys and the results are verified with the published theoretical models and experimental tests. Also, the effect of different parameters, such as the particle velocity, shear flow stress, shear strain rate and temperature are investigated. As a result, the presented model shows good capability in describing the mentioned parameters.

scholarly journals A New Set-Up to Investigate Plastic Deformation of Face Centered Cubic Metals in High Strain Rate Loading

2014 ◽  
Vol 8 (2) ◽  
Author(s):  
Ehsan Etemadi ◽  
Jamal Zamani ◽  
Alessandro Francesconi ◽  
Mohammad V. Mousavi ◽  
Cinzia Giacomuzzo
Keyword(s):  
Plastic Deformation ◽  
High Strain Rate ◽  
Strain Rate ◽  
High Strain ◽  
Face Centered Cubic ◽  
Cubic Metals ◽  
Face Centered ◽  
Set Up ◽  
Strain Rate Loading

scholarly journals Dynamic Mechanical Properties and Microstructure of an (Al0.5CoCrFeNi)0.95Mo0.025C0.025 High Entropy Alloy

Entropy ◽  
2019 ◽  
Vol 21 (12) ◽  
pp. 1154
Author(s):  
Bingfeng Wang ◽  
Chu Wang ◽  
Bin Liu ◽  
Xiaoyong Zhang
Keyword(s):  
Mechanical Properties ◽  
Shear Band ◽  
High Strain Rate ◽  
Strain Rate ◽  
High Strain ◽  
Dynamic Mechanical Properties ◽  
High Entropy Alloy ◽  
Face Centered Cubic ◽  
High Entropy ◽  
Dynamic Mechanical

The dynamic mechanical properties and microstructure of the (Al0.5CoCrFeNi)0.95Mo0.025C0.025 high entropy alloy (HEA) prepared by powder extrusion were investigated by a split Hopkinson pressure bar and electron probe microanalyzer and scanning electron microscope. The (Al0.5CoCrFeNi)0.95Mo0.025C0.025 HEA has a uniform face-centered cubic plus body-centered cubic solid solution structure and a fine grain-sized microstructure with a size of about 2 microns. The HEA possesses an excellent strain hardening rate and high strain rate sensitivity at a high strain rate. The Johnson–Cook plastic model was used to describe the dynamic flow behavior. Hat-shaped specimens with different nominal strain levels were used to investigate forced shear localization. After dynamic deformation, a thin and short shear band was generated in the designed shear zone and then the specimen quickly fractured along the shear band.

scholarly journals Validation of a Microstructure-Based Model for Predicting the High Strain Rate Flow Properties of Various Forms of Additively Manufactured Ti6Al4V(ELI) Alloy

Metals ◽  
2021 ◽  
Vol 11 (10) ◽  
pp. 1628
Author(s):  
Amos Muiruri ◽  
Maina Maringa ◽  
Willie du Preez
Keyword(s):  
Mechanical Properties ◽  
Flow Stress ◽  
High Strain Rate ◽  
Strain Rate ◽  
Physical Model ◽  
High Strain ◽  
Critical Role ◽  
Viscous Drag ◽  
Flow Properties ◽  
Average Grain Size

To increase the acceptance of direct metal laser sintered Ti6Al4V(Extra Low Interstitial—ELI) in industry, analytical models that can quantitatively describe the interrelationships between the microstructural features, field variables, such as temperature and strain rate, and the mechanical properties are necessary. In the present study, a physical model that articulates the critical microstructural features of grain sizes and dislocation densities for use in predicting the mechanical properties of additively manufactured Ti6Al4V(ELI) was developed. The flow stress curves of different microstructures of the alloy were used to obtain and refine the parameters of the physical model. The average grain size of a microstructure was shown to influence the athermal part of yield stress, while the initial dislocation density in a microstructure was seen to affect the shape of the flow stress curve. The viscous drag effect was also shown to play a critical role in explaining the upturn of flow stress at high strain rates. The microstructure-based constitutive model developed and validated in this article using experimental data showed good capacity to predict the high strain rate flow properties of additively manufactured Ti6Al4V(ELI) alloy.

High Strain Rate Behavior of Metals

1990 ◽  
Vol 43 (5S) ◽  
pp. S9-S22 ◽  
Author(s):  
R. J. Clifton
Keyword(s):  
Flow Stress ◽  
High Strain Rate ◽  
Strain Rate ◽  
High Strain ◽  
Rate Sensitivity ◽  
Strong Increase ◽  
Strain Rates ◽  
Shear Strain Rate ◽  
High Strain Rates ◽  
Strain Rate Change

Experimental results on the high strain rate response of polycrystalline metals are reviewed, with emphasis on the behavior of pure metals. A strong increase in flow stress with increasing strain rate is reported for strain rates of approximately 105s−1 and higher. This increase is observed in pressure-shear plate impact experiments at nominally constant strain rates from 105s−1 to 106s−1. To improve understanding of the increased rate sensitivity at high strain rates, pressure-shear, strain-rate-change experiments have been conducted on OFHC copper specimens. These experiments have been analyzed using a conventional viscoplasticity formulation and an internal variable formulation in which the hardening rate depends on the rate of deformation. Only the latter formulation is successful in describing the observed response to the change in strain rate. This observation is discussed in terms of its implications for interpreting other dynamic plasticity experiments and for improved understanding of the underlying dislocation mechanisms. The enhanced rate sensitivity at high strain rates is concluded to be related primarily to the rate sensitivity of strain hardening, not the rate sensitivity of the flow stress at constant structure.

scholarly journals Characterizations of STF-Treated Aramid Fabrics Using Picture Frame Test

2014 ◽  
Vol 611-612 ◽  
pp. 344-348 ◽  
Author(s):  
Hyun Chul Ahn ◽  
Won Jin Na ◽  
Sung Jin Han ◽  
Philip Harrison ◽  
Jong Kyoo Park ◽  
...  
Keyword(s):  
High Strain Rate ◽  
Strain Rate ◽  
Shear Strain ◽  
High Strain ◽  
Shear Thickening ◽  
Shear Strain Rate ◽  
Shear Properties ◽  
Aramid Fabrics ◽  
Picture Frame ◽  
Picture Frame Test

Shear thickening fluid (STF) is a non-Newtonian fluid featuring the increased viscosity upon high strain rate applied. Recently, STF-treated aramid fabrics have been researched to enhance the bulletproof efficiency maintaining the lightweight, however their shear properties including tow shearing, which significantly contribute to the bulletproof properties, have not been characterized, in particular under high shear strain rates. In this study, the shear properties of STF-treated aramid fabrics are characterized using a picture frame test. For this purpose, STF is prepared using polyethylene glycol and silica colloids and coated onto aramid fabrics. Varying the shear strain rate by controlling the pulling speed of the picture frame, the effect of STF on the shear properties of the aramid fabric is investigated. Finally, the shear properties of STF-treated aramid fabrics are predicted a multi-scale energy model and compared with the experiments. This prediction is then extended to cover such a high strain-rate situation as the bullet impacts, enabling to determine the mechanism behind the improved bulletproof performance of the STF-treated fabric.

Strengthening of FCC Metals at High Strain Rates

2014 ◽  
Vol 566 ◽  
pp. 73-79
Author(s):  
Hervé Couque
Keyword(s):  
Strain Rate ◽  
Thermal Activation ◽  
High Strain ◽  
Viscous Drag ◽  
Strain Rates ◽  
Face Centered Cubic ◽  
High Strain Rates ◽  
Cubic Metals ◽  
Face Centered ◽  
Rate Threshold

The influence of strain rate over domains involving the thermal activation and the viscous drag behavior of the dislocations has been investigated for a series of face centered cubic metals. The effect of grain size on the strain rate threshold delimitating the two domains in compression was examined with grains sizes ranging from 0.1 to 100 μm for nickel and copper. The tensile strengthening occurring at high strain rates for an austenitic stainless steel was also investigated.

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