High Strain Rate Behavior of Graphene Reinforced Polyurethane Composites

2015 ◽  
Vol 137 (2) ◽  
Author(s):  
Sanjeev K. Khanna ◽  
Ha T. T. Phan
Keyword(s):  
High Strain Rate ◽  
Strain Rate ◽  
High Strain ◽  
Peak Load ◽  
Peak Stress ◽  
Strain Rates ◽  
Peak Strain ◽  
Plateau Stress ◽  
Dynamic Mechanical ◽  
Stress Peak

A compressive split Hopkinson pressure bar (SHPB) was used to investigate the dynamic mechanical behavior of graphene (GR) reinforced polyurethane (PU) composites (GR/PU) at high strain rates ranging from approximately 1500 s−1 to 5000 s−1. Four types of GR/PU composites with different GR contents: 0.25% GR, 0.5% GR, 0.75% GR, and 1% GR were prepared by the solution mixing method and divided into two groups of unheated and postheated specimens. Experimental results show that the GR/PU composite is a strong strain rate dependent material, especially in the high strain rate regime of 3000 s−1–5000 s−1. The dynamic mechanical properties of GR/PU composite in terms of plateau stress, peak stress, and peak load carrying capacity are better than that of pristine PU at most of the applied strain rates. Among the four different GR concentrations used, the 0.5 wt.%-GR specimen shows the highest peak stress, and the 1 wt.% GR specimen has the highest plateau stress; while no significant change in peak strain with changing GR weight fraction was observed. Compared to unheated specimens, the plateau stress, peak stress, and peak strain of postheated specimens are significantly higher.

A New High Strain-Rate Biaxial Experiment to Validate Constitutive Models for Polymers

2016 ◽  
Author(s):  
Sean S. Teller ◽  
Eric C. Schmitt ◽  
Jörgen S. Bergström
Keyword(s):  
Finite Element ◽  
Constitutive Model ◽  
High Strain Rate ◽  
Strain Rate ◽  
High Strain ◽  
Constitutive Models ◽  
Finite Element Simulations ◽  
Strain Rates ◽  
Peak Strain ◽  
Impact Head

We have developed a new high strain rate experiment in biaxial tension that allows for constitutive model validation at engineering strain rates from 50/s to over 1000/s. In the experiment, a flat disk of the material is clamped at a fixed radial distance. A rail-guided impact sled with a hemispherical impact head is released from the desired height and impacts the disk at the center, potentially deforming the sample to failure. Drop height and impact mass can be varied to modify peak strain rate and impact energy, and the wide range of test conditions allow for testing to be performed on many classes of materials, including thermoplastics and elastomers. The stress and strain fields are calculated using finite element simulations with the proposed constitutive model, and the constitutive model is validated by matching the force versus displacement data of the impact head recorded during experiment to the simulation. In this paper, we discuss results from the experiment and finite element simulations of the experiment on PA (polyamide, nylon) and PEEK (polyether ether ketone). The new experiment allows for validation and refinement of constitutive models, including failure, at high strain rates and in a multiaxial stress state.

scholarly journals Experimental Study on Biaxial Dynamic Compressive Properties of ECC

Materials ◽  
2021 ◽  
Vol 14 (5) ◽  
pp. 1257
Author(s):  
Shuling Gao ◽  
Guanhua Hu
Keyword(s):  
Strain Rate ◽  
Lateral Pressure ◽  
Deformation Modulus ◽  
Strain Curve ◽  
Peak Stress ◽  
Pressure Level ◽  
Strain Rates ◽  
Peak Strain ◽  
Stress Strain Curve ◽  
Toughness Index

An improved hydraulic servo structure testing machine has been used to conduct biaxial dynamic compression tests on eight types of engineered cementitious composites (ECC) with lateral pressure levels of 0, 0.125, 0.25, 0.5, 0.7, 0.8, 0.9, 1.0 (the ratio of the compressive strength applied laterally to the static compressive strength of the specimen), and three strain rates of 10−4, 10−3 and 10−2 s−1. The failure mode, peak stress, peak strain, deformation modulus, stress-strain curve, and compressive toughness index of ECC under biaxial dynamic compressive stress state are obtained. The test results show that the lateral pressure affects the direction of ECC cracking, while the strain rate has little effect on the failure morphology of ECC. The growth of lateral pressure level and strain rate upgrades the limit failure strength and peak strain of ECC, and the small improvement is achieved in elastic modulus. A two-stage ECC biaxial failure strength standard was established, and the influence of the lateral pressure level and peak strain was quantitatively evaluated through the fitting curve of the peak stress, peak strain, and deformation modulus of ECC under various strain rates and lateral pressure levels. ECC’s compressive stress-strain curve can be divided into four stages, and a normalized biaxial dynamic ECC constitutive relationship is established. The toughness index of ECC can be increased with the increase of lateral pressure level, while the increase of strain rate can reduce the toughness index of ECC. Under the effect of biaxial dynamic load, the ultimate strength of ECC is increased higher than that of plain concrete.

Study on Dynamic Mechanical Response of TC21 Alloy

2011 ◽  
Vol 88-89 ◽  
pp. 674-678
Author(s):  
Shuang Zan Zhao ◽  
Xing Wang Cheng ◽  
Fu Chi Wang
Keyword(s):  
Flow Stress ◽  
High Strain Rate ◽  
Strain Rate ◽  
Strain Hardening ◽  
High Strain ◽  
Dynamic Flow ◽  
Dynamic Mechanical ◽  
Hardening Effect ◽  
High Strain Rate Deformation ◽  
Binary Morphology

Some results of an experimental study on high strain rate deformation of TC21 alloy are discussed in this paper. Cylindrical specimens of the TC21 alloys both in binary morphology and solution and aging morphology were subjected to high strain rate deformation by direct impact using a Split Hopkinson Pressure Bar. The deformation process is dominated by both thermal softening effect and strain hardening effect under high strain rate loading. Thus the flow stress doesn’t increase with strain rate at the strain hardening stage, while the increase is obvious under qusi-static compression. Under high strain rate, the dynamic flow stress is higher than that under quasi-static and dynamic flow stress increase with the increase of the strain rate, which indicates the strain rate hardening effect is great in TC21 alloy. The microstructure affects the dynamic mechanical properties of TC21 titanium alloy obviously. Under high strain rate, the solution and aging morphology has higher dynamic flow stress while the binary morphology has better plasticity and less prone to be instability under high strain rate condition. Shear bands were found both in the solution and aging morphology and the binary morphology.

Impact tensile behavior and frequency response of 3D braided composites

2011 ◽  
Vol 82 (3) ◽  
pp. 280-287 ◽  
Author(s):  
Xuehui Gan ◽  
Jianhua Yan ◽  
Bohong Gu ◽  
Baozhong Sun
Keyword(s):  
High Strain Rate ◽  
Strain Rate ◽  
Tensile Properties ◽  
High Strain ◽  
Tensile Modulus ◽  
Tensile Failure ◽  
Uniaxial Tensile ◽  
Strain Rates ◽  
Braided Composites ◽  
3D Braided Composites

The uniaxial tensile properties of 4-step 3D braided E-glass/epoxy composites under quasi-static and high-strain rate loadings have been investigated to evaluate the tensile failure mode at different strain rates. The uniaxial tensile properties at high strain rates from 800/s to 2100/s were tested using the split Hopkinson tension bar (SHTB) technique. The tensile properties at quasi-static strain rate were also tested and compared with those in high strain rates. Z-transform theory is applied to 3D braided composites to characterize the system dynamic behaviors in frequency domain. The frequency responses and the stability of 3D braided composites under quasi-static and high-strain rate compression have been analyzed and discussed in the Z-transform domain. The results indicate that the stress-strain curves are rate sensitive, and tensile modulus, maximum tensile stress and corresponding tensile strain are also sensitive to the strain rate. The tensile modulus, maximum tensile stress of the 3D braided composites are linearly increased with the strain rate. With increasing of the strain rate (from 0.001/s to 2100/s), the tensile failure of the 3D braided composite specimens has a tendency of transition from ductile failure to brittle failure. The magnitude response and phase response is very different in quasi-static loading with that in high-strain rate loading. The 3D braided composite system is more stable at high strain rate than quasi-static loading.

Research on Numerical Algorithm of Constitutive Equation under High Speed Deformation in Hadfield Steel

2012 ◽  
Vol 562-564 ◽  
pp. 688-692 ◽  
Author(s):  
Deng Yue Sun ◽  
Jing Li ◽  
Fu Cheng Zhang ◽  
Feng Chao Liu ◽  
Ming Zhang
Keyword(s):  
High Strain Rate ◽  
Strain Rate ◽  
Deformation Behavior ◽  
High Speed ◽  
High Strain ◽  
Equivalent Stress ◽  
Hadfield Steel ◽  
Stress And Strain ◽  
Strain Rates ◽  
The Finite Element Method

The influence of the strain rate on the plastic deformation of the metals was significant during the high strain rate of loading. However, it was very difficult to obtain high strain rate data (≥ 104 s-1) by experimental techniques. Therefore, the finite element method and iterative method were employed in this study. Numerical simulation was used to characterise the deformation behavior of Hadfield steel during explosion treatment. Base on experimental data, a modified Johnson-Cook equation for Hadfield steel under various strain rate was fitted. The development of two field variables was quantified during explosion hardening: equivalent stress and strain rates.

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.

Numerical Simulation of Hot High Strain Rate Torsion Tests for Al-Based Alloys

2019 ◽  
Vol 822 ◽  
pp. 66-71
Author(s):  
Anton Naumov ◽  
Anatolii Borisov ◽  
Anastasiya Y. Doroshchenkova
Keyword(s):  
Numerical Simulation ◽  
High Strain Rate ◽  
Strain Rate ◽  
Visual Analysis ◽  
Physical Simulation ◽  
High Strain ◽  
Torsion Test ◽  
Strain Rates ◽  
Deform 3D

The present research describes the comparison of numerical and physical simulation of hot high strain rate torsion tests for Al-based alloys in order to clarify the accuracy of calculations using basic grades of materials in Deform-3DTM software. A comparative visual analysis of the results is presented. Obtained data on the distribution of temperatures, strains, stresses and strain rates during the torsion test are discussed.

High Strain Rate Blow Formability of Newly Developed Al-Mg-High-Mn Alloy

2012 ◽  
Vol 735 ◽  
pp. 271-277 ◽  
Author(s):  
Tomoyuki Kudo ◽  
Akira Goto ◽  
Kazuya Saito
Keyword(s):  
Grain Size ◽  
High Strain Rate ◽  
Strain Rate ◽  
Mass Production ◽  
High Strain ◽  
Mg Alloy ◽  
Strain Rates ◽  
Fine Grain ◽  
Aa5083 Alloy ◽  
Complex Parts

Blow forming accompanied with superplasticity makes possible the forming of complex parts, which cannot be formed by cold press forming. The conventional superplastic AA5083 alloy ‘ALNOVI-1’ developed by the Furukawa-Sky Aluminum Corp. shows high superplasticity because of its fine grain and is widely used for blow forming. However, for mass production of components, an Al-Mg alloy with finer-sized grains is needed. In this research, the newly developed high Mn version of the Al-Mg alloy ‘ALNOVI-U’ is used, and this material possesses grains finer than those of the conventional AA5083 alloy. The effects of finer grain size on the blow formability at high strain rates over 10-2/s and the properties of the resulting moldings were studied.

Medium to High Strain-Rate Characterization of Lead Free Solder Alloys Through Metal Cutting Experiments

2019 ◽  
Author(s):  
Yuvraj Singh ◽  
Anirudh Udupa ◽  
Srinivasan Chandrasekar ◽  
Ganesh Subbarayan
Keyword(s):  
High Strain Rate ◽  
Strain Rate ◽  
Metal Cutting ◽  
High Strain ◽  
Lead Free ◽  
Strain Rates ◽  
Lead Free Solder ◽  
Orthogonal Metal Cutting ◽  
Free Solder

Abstract Studies on medium to high strain-rate characterization (≥ 0.1s−1) of lead-free solder are relatively few, primarily due to the lack of available methods for testing. Prior work in literature uses Split Hopkinson Bar (SPHB) experiments for high strain-rate characterization (≥ 300s−1) [1,2], while a modified micro-scale tester is used for medium strain-rate characterization (0.005s−1 to 300s−1) [3] and an impact hammer test setup for testing in a strain-rate regime from 1s−1 to 100s−1 [4]. However, there is still limited data in strain-rate regimes of relevance, specifically for drop shock applications. In this paper, we present orthogonal metal cutting as a novel method to characterize lead-free solder alloys. Experiments are carried out using a wedgelike tool that cuts through a work piece at a fixed depth and rake angle while maintaining a constant cutting velocity. These experiments are conducted at room temperature on Sn1.0Ag0.5Cu bulk test specimens with strain-rates varying from 0.32 to 48s−1. The range of strain-rates is only limited by the ball screw driven slide allowing higher strain-rates if needed. The strains and strain-rates are captured through Particle Image Velocimetry (PIV) using sequential images taken from a high-speed camera just ahead of the cutting tool. The PIV enables non-contact recording of high strain-rate deformations, while the dynamometer on the cutting head allows one to capture the forces exerted during the cutting process. Results for the stress-strain response obtained through the experiments are compared to prior work for validation. Orthogonal metal cutting is shown to be a potentially attractive method for characterization of solder at higher strain-rates.

scholarly journals Effect of Stress-Relieving Heat Treatment on the High Strain Rate Dynamic Compressive Properties of Additively Manufactured Ti6Al4V (ELI)

Metals ◽  
2020 ◽  
Vol 10 (5) ◽  
pp. 653
Author(s):  
Amos Muiruri ◽  
Maina Maringa ◽  
Willie du Preez ◽  
Leonard Masu
Keyword(s):  
Plastic Strain ◽  
High Strain Rate ◽  
Strain Rate ◽  
High Strain ◽  
Split Hopkinson Pressure Bar ◽  
Deformation Behaviour ◽  
Test System ◽  
Strain Rates ◽  
Stress Relieving ◽  
Strain Rate Compression

A study was undertaken on the compressive high strain rate properties and deformation behaviour of Direct Metal Laser-Sintered (DMLS) Ti6Al4V (ELI) parts in two separate forms: as-built (AB) and stress relieved (SR). The high strain rate compression tests were carried out using a Split Hopkinson Pressure Bar test system at ambient temperature. The average plastic strain rates attained by the system were 400 s−1 and 700 s−1. Comparative analyses of the performance (flow stresses and fracture strains) of AB and SR specimens were carried out based on the results obtained at these two plastic strain rates. Microstructural analyses were performed to study the failure mechanisms of the deformed specimens and fracture surfaces. Vickers microhardness test values were obtained before and after high strain rate compression testing. The results obtained in both cases showed the strain rate sensitivity of the stress-relieved samples to be higher in comparison to those of as-built ones, at the same value of true strain.

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