High-Rate Mechanical Response of Aluminum Using Miniature Kolsky Bar Techniques

2017 ◽  
pp. 147-153 ◽  
Author(s):  
Daniel T. Casem ◽  
Jonathan P. Ligda ◽  
Brian E. Schuster ◽  
Shane Mims
Keyword(s):  
Mechanical Response ◽  
Kolsky Bar ◽  
High Rate

Simultaneous effects of strain rate and temperature on mechanical response of fabricated Mg–SiC nanocomposite

2019 ◽  
Vol 54 (5) ◽  
pp. 659-668 ◽  
Author(s):  
K Rahmani ◽  
GH Majzoobi ◽  
A Atrian
Keyword(s):  
Strain Rate ◽  
Mechanical Response ◽  
Split Hopkinson Pressure Bar ◽  
High Rate ◽  
Dynamic Tests ◽  
Hopkinson Pressure Bar ◽  
Compaction Temperature ◽  
Static Tests ◽  
Split Hopkinson ◽  
Pressure Bar

Mg–SiC nanocomposite samples were fabricated using split Hopkinson pressure bar for different SiC volume fractions and under different temperature conditions. The microstructures and mechanical properties of the samples including microhardness and stress–strain curves were captured from quasi-static and dynamic tests carried out using Instron and split Hopkinson pressure bar, respectively. Nanocomposites were produced by hot and high-rate compaction method using split Hopkinson pressure bar. Temperature also significantly affects relative density and can lead to 2.5% increase in density. Adding SiC-reinforcing particles to samples increased their Vickers microhardness from 46 VH to 68 VH (45% increase) depending on the compaction temperature. X-ray diffraction analysis showed that by increasing temperature from 25℃ to 450℃, the Mg crystallite size increases from 37 nm to 72 nm and decreases the lattice strain from 45% to 30%. In quasi-static tests, the ultimate compressive strength for the compaction temperature of 450℃ was improved from 123% for Mg–0 vol.% SiC to 200% for the Mg–10 vol.% SiC samples compared with those of the compaction at room temperature. In dynamic tests, the ultimate strength for Mg–10 vol.% SiC sample compacted at high strain rate increased remarkably by 110% compared with that for Mg–0 vol.% SiC sample compacted at low strain rate.

AN IMAGE BASED INERTIAL IMPACT TEST TO EXTRACT VISCOELASTIC CONSTITUTIVE PARAMETERS

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.

An Analytical and Computational Investigation of High-Rate Rheometry

1996 ◽  
Vol 118 (3) ◽  
pp. 601-607 ◽  
Author(s):  
R. Feng ◽  
K. T. Ramesh ◽  
A. S. Douglas
Keyword(s):  
Shear Stress ◽  
Numerical Simulations ◽  
Layer Thickness ◽  
Rise Time ◽  
Kolsky Bar ◽  
High Rate ◽  
Lubricant Layer ◽  
Transient Phenomena ◽  
Boundary Velocity ◽  
Kolsky Bar Experiments

This paper examines a class of experimental techniques used to develop constitutive models for lubricants, by simulating the shearing of a thin lubricant layer while accounting for transient phenomena. The complete transient thermal problem with fully nonlinear constitutive relations is solved, and heat conduction is accounted for both in the lubricant layer and into the walls. Numerical simulations are used to examine the shear stress history, the velocity profile, and the temperature profile as functions of time. As a particular example, the high-rate torsional Kolsky bar rheometer (Feng and Ramesh, 1993) is simulated. The computations indicate that the Kolsky bar experiments, which are able to examine the time-histories of the stresses and of the motion, can he used to obtain material properties for lubricants at high shear rates. A full numerical analysis may be required to properly interpret some of the data available from the Kolsky bar experiments, since at longer times (greater than that associated with the peak shear stress) the thermal softening may dominate the response and the velocity field may become strongly inhomogeneous. The numerical simulations are performed using both rate-dependent and limiting stress constitutive laws, and the effects of the layer thickness and the rise time of the relative velocities are examined. The simulations show that the film thickness and the rise time of the relative velocities can have strong effects on the character of the solution when the transient phenomena are included in the analysis. The computations also demonstrate that highly inhomogeneous and even localized flows may occur within rheometers as a result of transient effects. The development of these flows depends on the layer thickness, the rise-time of the boundary velocity, the thermal boundary conditions, and the constitutive behavior of the lubricant.

Dynamic Constitutive and Failure Behavior of a Two-Phase Tungsten Composite

1997 ◽  
Vol 64 (3) ◽  
pp. 487-494 ◽  
Author(s):  
M. Zhou ◽  
R. J. Clifton
Keyword(s):  
Shear Band ◽  
Shear Bands ◽  
Kolsky Bar ◽  
High Rate ◽  
Failure Behavior ◽  
Localized Deformation ◽  
Two Phase ◽  
The Matrix ◽  
Torsional Kolsky Bar ◽  
The Impact

The constitutive response and failure behavior of a W-Ni-Fe alloy over the strain rate range of 10-4 to 5 X 105 s-1 is experimentally investigated. Experiments conducted are pressure-shear plate impact, torsional Kolsky bar, and quasi-static torsion. The material has a microstructure of hard tungsten grains embedded in a soft alloy matrix. Nominal shear stress-strain relations are obtained for deformations throughout the experiments and until after the initiation of localization. Shear bands form when the plastic strain becomes sufficiently large, involving both the grains and the matrix. The critical shear strain for shear band development under the high rate, high pressure conditions of pressure-shear is approximately 1–1.5 or 6–8 times that obtained in torsional Kolsky bar experiments which involve lower strain rates and zero pressure. Shear bands observed in the impact experiments show significantly more intensely localized deformation. Eventual failure through the shear band is a combination of grain-matrix separation, ductile matrix rupture, and grain fracture. In order to understand the effect of the composite microstructure and material inhomogeneity on deformation, two other materials are also used in the study. One is a pure tungsten and the other is an alloy of W, Ni, and Fe with the same composition as that of the matrix phase in the overall composite. The results show that the overall two-phase composite is more susceptible to the formation of shear bands than either of its constituents.

Traumatic Brain Injury: Coupled Experiment/Finite Element Simulation on High Rate Mechanical Response of Porcine Brain

2010 ◽  
Author(s):  
Raj Prabhu ◽  
Mark Horstemeyer ◽  
Michael McCollum ◽  
Wilburn Whittington ◽  
Jean-Luc Bouvard ◽  
...  
Keyword(s):  
Traumatic Brain Injury ◽  
Finite Element ◽  
Brain Injury ◽  
Mechanical Response ◽  
Experimental Studies ◽  
High Rate ◽  
Element Analysis ◽  
Element Simulation ◽  
Professional Boxing

Traumatic Brain Injury (TBI), due to recursive concussions, is prevalent in professional sports. Martland was first to report neuropathological conditions related to recursive TBI in professional boxing; while Omalu et al. were the first to report similar neuropathogical conditions, in NFL professionals [1, 2]. Both Martland and Omalu et al. reported long-term neurodegeneration leading to dementia and Alzheimer’s disease [1, 2]. Professional athletes with recursive TBI were observed to have developed speech difficulties, memory lapses, Parkinsons’s-like syndrome with drooling, tremors, and emotional volatility. Although clinical and experimental studies have been carried out to advance the understanding of pathophysiological mechanisms following TBI, limited progress has been made in understanding the effect of stress waves on the neuropathology of TBI using Finite Element Analysis (FEA).

scholarly journals Nonlinear Magneto-Electro-Mechanical Response of Physical Cross-Linked Magneto-Electric Polymer Gel

2021 ◽  
Vol 8 ◽  
Author(s):  
Xiwen Fan ◽  
Yu Wang ◽  
Bochao Wang ◽  
Longjiang Shen ◽  
Jun Li ◽  
...  
Keyword(s):  
High Performance ◽  
Magnetic Particles ◽  
Mechanical Response ◽  
High Rate ◽  
Dependent Manner ◽  
Polymer Gel ◽  
Resistance Response ◽  
Mechanical Responses ◽  
Rate Dependent ◽  
Electromechanical Performance

This work reports on a novel magnetorheological polymer gel with carbon nanotubes and carbonyl iron particles mixed into the physical cross-linked polymer gel matrix. The resulting composites show unusual nonlinear magneto-electro-mechanical responses. Because of the low matrix viscosity, effective conductive paths formed by the CNTs were mobile and high-performance sensing characteristics were observed. In particular, due to the transient and mutable physical cross-linked bonds in the polymer gel, the electromechanical behavior acted in a rate-dependent manner. External stimulus at a high rate significantly enhanced the electrical resistance response during mechanical deformation. Meanwhile, the rheological properties were regulated by the external magnetic field when magnetic particles were added. This dual enhancement mechanism further contributes to the active control of electromechanical performance. These polymer composites could be adopted as electromechanical sensitive sensors to measure impact and vibration under different frequencies. There is great potential for this magnetorheological polymer gel in the application of intelligent vibration controls.

Sign in / Sign up

Export Citation Format

Share Document