scholarly journals FE Analysis of Critical Testing Parameters in Kolsky Bar Experiments for Elastomers at High Strain Rate

Materials ◽  
2019 ◽  
Vol 12 (23) ◽  
pp. 3817
Author(s):  
Chaudhry ◽  
Czekanski
Keyword(s):  
Finite Element ◽  
High Strain Rate ◽  
Strain Rate ◽  
Pulse Shaping ◽  
High Strain ◽  
Kolsky Bar ◽  
Specimen Geometry ◽  
Strain Rates ◽  
Butadiene Rubber ◽  
Testing Apparatus

The main aim of this research is to present complete methodological guidelines for dynamic characterization of elastomers when subjected to strain rates of 100/s–10,000/s. We consider the following three aspects: (i) the design of high strain rate testing apparatus, (ii) finite element analysis for the optimization of the experimental setup, and (iii) experimental parameters and validation for the response of an elastomeric specimen. To test low impedance soft materials, design of a modified Kolsky bar is discussed. Based on this design, the testing apparatus was constructed, validated, and optimized numerically using finite element methods. Furthermore, investigations on traditional pulse shaping techniques and a new design for pulse shaper are described. The effect of specimen geometry on the homogeneous deformation has been thoroughly accounted for. Using the optimized specimen geometry and pulse shaping technique, nitrile butadiene rubber was tested at different strain rates, and the experimental findings were compared to numerical predictions.

SIF Evaluation Using XFEM and Line Spring Models Under High Strain Rate Environment for Leadfree Alloys

2011 ◽  
Author(s):  
Pradeep Lall ◽  
Mandar Kulkarni ◽  
Sandeep Shantaram ◽  
Jeff Suhling
Keyword(s):  
Stress Intensity Factor ◽  
Finite Element ◽  
Stress Intensity ◽  
Intensity Factor ◽  
High Strain Rate ◽  
Strain Rate ◽  
High Speed ◽  
High Strain ◽  
Strain Rates ◽  
Fracture Properties

In this paper, fracture properties of Sn3Ag0.5Cu leadfree high strain-rate solder-copper interface have been evaluated and validated with those from experimental methods. Bi-material Copper-Solder specimen have been tested at strain rates typical of shock and vibration with impact-hammer tensile testing machine. Models for crack initiation and propagation have been developed using Line spring method and extended finite element method (XFEM). Critical stress intensity factor for Sn3Ag0.5Cu solder-copper interface have been extracted from line spring models. Displacements and derivatives of displacements have been measured at crack tip and near interface of bi-material specimen using high speed imaging in conjunction with digital image correlation. Specimens have been tested at strain rates of 20s−1 and 55s−1 and the event is monitored using high speed data acquisition system as well as high speed cameras with frame rates in the neighborhood of 300,000 fps. Previously the authors have applied the technique of XFEM and DIC for predicting failure location and to develop constitutive models in leaded and few leadfree solder alloys [Lall 2010a]. The measured fracture properties have been applied to prediction of failure in ball-grid arrays subjected to high-g shock loading in the neighborhood of 12500g in JEDEC configuration. Prediction of fracture in board assemblies using explicit finite element full-field models of board assemblies under transient-shock is new. Stress intensity factor at Copper pad and bulk solder interface is also evaluated in ball grid array packages.

Finite Element Modelling of a Modified Kolsky Bar Developed for High Strain Rate Testing of Elastomers

2015 ◽  
Author(s):  
M. S. Chaudhry ◽  
R. Carrick ◽  
A. Czekanski
Keyword(s):  
Finite Element ◽  
Strain Rate ◽  
High Strain ◽  
Soft Materials ◽  
Kolsky Bar ◽  
Strain Rates ◽  
Pulse Shaper ◽  
Hyperelastic Materials ◽  
High Strain Rate Testing ◽  
Split Hopkinson

Elastomers are finding a wide variety of dynamic applications in aerospace, automobile and biomedical industries. The response of these complex material is based on the loading conditions and the strain rate at which the loading is applied. To suit the designer’s requirement, there is an ever increasing need to characterize this application specific, dynamic behavior under high strain rates. The Kolsky bar apparatus, also known as the Split Hopkinson Bar, is the most common apparatus used to test engineering materials at strain rates between 100/s and 10000/s. In this paper a modified Kolsky bar to characterize soft material is numerically modeled using Finite Element Method. The focus of the study is to numerically analyze the modifications made to a conventional Kolsky bar to specifically test nonlinear hyperelastic, soft materials. The challenge for testing low strength materials is the impedance mismatch between the bar and specimen interfaces, which results in a very weak distorted signal. One of the solution is to use a hollow transmission bar instead of solid one. With the use of FEM it can be numerically verified that using a hollow bar increases the amplitude of the transmitted signal up to several times. It is known that the rise time of the elastic wave can be increased by using a copper pulse shaper. Different dimensions of pulse shaper are modeled and the effect on the incident pulse is analyzed. The main aim of this study is to provide a detailed numerical analysis on the testing parameters, and to model one way wave propagation in Kolsky bar experiment for hyperelastic materials. The constitutive equations used to model the parts of the apparatus are also discussed.

Strain rate effects of tensile behaviors of 3-D orthogonal woven fabric: Experimental and finite element analyses

2012 ◽  
Vol 83 (4) ◽  
pp. 337-354 ◽  
Author(s):  
Yangqing Hou ◽  
Lili Jiang ◽  
Baozhong Sun ◽  
Bohong Gu
Keyword(s):  
Finite Element ◽  
High Strain Rate ◽  
Strain Rate ◽  
High Strain ◽  
Woven Fabric ◽  
Strain Rates ◽  
High Strain Rates ◽  
Stress Strain ◽  
Two Phase ◽  
Tensile Stiffness

The tensile behaviors of 3-D woven fabric under high strain-rate states, i.e. tensile impact behaviors, are important for the design of the fabrics and the reinforced composites under impulsive loading. This paper reports the testing and the numerical simulation of the impact tension behaviors of 3-D woven fabric under high strain rates compared with those under quasi-static tension. The tensile behaviors of 3-D orthogonal woven fabric (3DOWF) were investigated using a MTS 810.23 material testing system and a self-designed split Hopkinson tension bar apparatus, under a wide range of strain rates (0.003–2308/s). The tensile stress–strain curves obtained from the quasi-static and high strain rates were used to analyze the rate-sensitivity of 3DOWF tensile behaviors. It was found that both the tensile strength and the failure strain increased with increases in the strain rate. The two-phase tensile stiffness phenomenon of 3DOWF under high strain rates has been observed experimentally. A microstructure model combined with finite element analysis was established to explain the tensile failure mechanisms of 3DOWF under high strain rates. It was found that the fabric architecture influences the stress wave propagation, thus leading to the two-phase tensile stiffness phenomenon in the stress–strain curve under high strain-rate tensions.

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 Dynamic constitutive relation of 5083P-O aluminium alloy and its influence on energy-absorbing structure

2018 ◽  
Vol 10 (10) ◽  
pp. 168781401880733
Author(s):  
Yue Feng ◽  
Shoune Xiao ◽  
Bing Yang ◽  
Tao Zhu ◽  
Guangwu Yang ◽  
...  
Keyword(s):  
Finite Element ◽  
Strain Rate ◽  
Aluminium Alloy ◽  
Constitutive Relation ◽  
High Strain ◽  
Deformation Mode ◽  
Strain Rates ◽  
Strengthening Effect ◽  
Element Simulation ◽  
Energy Absorbing

Dynamic and quasi-static tensile tests of 5083P-O aluminium alloy were carried out using RPL100 electronic creep/fatigue testing machine and the split Hopkinson tension bar, respectively. The dynamic constitutive relation of the material at high strain rates was studied, and the constitutive model in accordance with Cowper–Symonds form was established. At the same time, a method to describe the constitutive relation of material using the strain rate interpolation method which is included in LS-DYNA software was proposed. The advantages and accuracy of this method were verified by comparing the results of the finite element simulation with the fitting results of the Cowper-Symonds model. The influence of material strain rate effect on squeezing force, energy absorption and deformation mode of the squeezing energy-absorbing structure based on the constitutive models of 5083P-O were studied by means of finite element simulation. The results show that when the strain rate of the structure deformation is low, the material strain rate strengthening effect has little influence on the structure. However, with the increase of the strain rate, the strengthening effect of the material will improve the squeezing force and the energy absorption of the structure, and will also influence the deformation mode, that is, the decrease of the deformation with high strain rates while the increase of the deformation with low strain rates.

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.

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.

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