Mechanism of the Strain Rate Effect of Metal Foams with Numerical Simulations of 3D Voronoi Foams during the Split Hopkinson Pressure Bar Tests

2015 ◽  
Vol 12 (04) ◽  
pp. 1540010 ◽  
Author(s):  
B. Yang ◽  
Z. J. Liu ◽  
L. Q. Tang ◽  
Z. Y. Jiang ◽  
Y. P. Liu
Keyword(s):  
Strain Rate ◽  
Numerical Simulations ◽  
Strain Rate Sensitivity ◽  
Split Hopkinson Pressure Bar ◽  
Rate Sensitivity ◽  
Metal Foams ◽  
Hopkinson Pressure Bar ◽  
Matrix Metal ◽  
The Matrix ◽  
Pressure Bar

With the demand of lightweight structure, more and more metal foams were employed as impact protection and efficient energy absorption materials in engineering fields. But, results from different impact experiments showed that the strain rate sensitivity of metal foams were different or even controversial. In order to explore the true hiding behind the controversial experimental data about the strain rate sensitivity of metal foams, numerical simulations of split Hopkinson pressure bar (SHPB) tests of the metal foams were carried out by finite element methods. In the analysis, cell structures of metal foams were constructed by means of 3D Voronoi, and the matrix metal was assumed to be no strain rate sensitivity, which helps to learn the strain rate effects quantitatively by the foam structures. Numerical simulations showed that the deformation of the metal foam specimen is not uniform during the SHPB tests along the specimen, and the strain–stress relations of the metal foams at two ends of the specimen are different; there exists strain rate sensitivity of the metal foams even the matrix metal has no strain rate sensitivity, when the strain of the metal foams is defined by the displacement difference between the ends of the specimen; localized deformation of the metal foams and the inertia effect of matrix metal are the two main contributions to the strain rate sensitivity of the metal foams.

Effect of Surface Modification on Strain Rate Sensitivity of Polypropylene/Muscovite Layered Silicate Composites

2014 ◽  
Vol 803 ◽  
pp. 343-347
Author(s):  
M.F. Omar ◽  
Nur Suhaili Abd Wahab ◽  
Hazizan Md Akil ◽  
Zainal Arifin Ahmad ◽  
Mohd Fadli Ahmad Rasyid ◽  
...  
Keyword(s):  
Surface Modification ◽  
Ion Exchange ◽  
Strain Rate ◽  
Strain Rate Sensitivity ◽  
Split Hopkinson Pressure Bar ◽  
Layered Silicate ◽  
Rate Sensitivity ◽  
Hopkinson Pressure Bar ◽  
Split Hopkinson ◽  
Pressure Bar

Surface modification is one of the treatment methods that can be implemented to improve the strain rate sensitivity of composite materials. In this study, both untreated and treated polypropylene/muscovite layered silicate composites were tested under static and dynamic loading up to 1100 s-1 using the universal testing machine and the split Hopkinson pressure bar apparatus, respectively. Muscovite particles were treated with lithium nitrate and cetyltrimethylammonium bromide as a surfactant through ion exchange treatment. Results show that the treated polypropylene/muscovite specimens with fine state of dispersion level shows better rate of sensitivity as compared to untreated polypropylene/muscovite specimens under a wide range of strain rate investigated. Apart from that, the rate of sensitivity of both tested polypropylene/muscovite layered silicate composites also show great dependency on the strain rate sensitivity was steadily increased with increasing strain rate. Unfortunately, the thermal activation values show contrary trend. Key words: Ion exchange treatment; Strain rate sensitivity; Muscovite particles; Split Hopkinson pressure bar apparatus; Strain rates

scholarly journals Study on the dynamic properties of AM-SLM AlSi10Mg alloy using the Split Hopkinson Pressure Bar (SHPB) technique

2018 ◽  
Vol 183 ◽  
pp. 04005 ◽  
Author(s):  
Bar Nurel ◽  
Moshe Nahmany ◽  
Adin Stern ◽  
Nahum Frage ◽  
Oren Sadot
Keyword(s):  
Strain Rate ◽  
Split Hopkinson Pressure Bar ◽  
Dynamic Properties ◽  
Rate Sensitivity ◽  
Strain Rate Range ◽  
Strain Rates ◽  
Hopkinson Pressure Bar ◽  
Static Mechanical ◽  
Split Hopkinson ◽  
Pressure Bar

Additive manufacturing by Selective Laser Melting of metals is attracting substantial attention, due to its advantages, such as short-time production of customized structures. This technique is useful for building complex components using a metallic pre-alloyed powder. One of the most used materials in AMSLM is AlSi10Mg powder. Additively manufactured AlSi10Mg may be used as a structural material and it static mechanical properties were widely investigated. Properties in the strain rates of 5×102–1.6×103 s-1 and at higher strain rates of 5×103 –105 s-1 have been also reported. The aim of this study is investigation of dynamic properties in the 7×102–8×103 s-1 strain rate range, using the split Hopkinson pressure bar technique. It was found that the dynamic properties at strain-rates of 1×103–3×103 s-1 depend on a build direction and affected by heat treatment. At higher and lower strain-rates the effect of build direction is limited. The anisotropic nature of the material was determined by the ellipticity of samples after the SHPB test. No strain rate sensitivity was observed.

scholarly journals Epoxy-glass Microballoon Syntactic Foams for Blast Mitigating Applications

2018 ◽  
Vol 68 (2) ◽  
pp. 210 ◽  
Author(s):  
A.V. Ullas ◽  
P. K. Sharma ◽  
P. Chandel ◽  
P. Sharma ◽  
D. Kumar ◽  
...  
Keyword(s):  
Strain Rate ◽  
Split Hopkinson Pressure Bar ◽  
Hollow Spheres ◽  
Rate Sensitivity ◽  
Syntactic Foams ◽  
Hopkinson Pressure Bar ◽  
Split Hopkinson ◽  
Static Regime ◽  
Pressure Bar ◽  
Blast Loadings

Polymeric syntactic foams refer to a class of cellular material created using preformed hollow spheres bound together with a polymeric matrix. These cellular materials possess exceptional ability to respond against high impact dynamic loads. This paper is an attempt to fabricate polymeric syntactic foams of epoxy containing hollow glass microballoon at varying loading (40 % - 60 %) and explore their potential towards blast mitigation. The tensile, compressive and flexural strength were found to be inversely proportional to the microballoon loading in the quasi-static regime. The strain rate sensitivity of the foams was confirmed by performing high strain rate studies using split hopkinson pressure bar. The flow stress of these foams was found to increase with increasing strain rates. The syntactic foams were subjected to controlled transient blast loadings using a shock tube. The samples remained intact and no strain was observed on the strain gauge, even under a blast load of ~ 90 psi, which clearly highlight their potential as core materials for blast mitigating applications.

High Strain Rate Compressive Behaviour of Selective Laser Melted Ti-6Al-4V

2017 ◽  
Vol 890 ◽  
pp. 323-326 ◽  
Author(s):  
Maziar Ramezani ◽  
Emmanuel Flores-Johnson ◽  
Lu Ming Shen ◽  
Thomas Neitzert
Keyword(s):  
High Strain Rate ◽  
Strain Rate ◽  
Strain Rate Sensitivity ◽  
Shear Failure ◽  
High Strain ◽  
Split Hopkinson Pressure Bar ◽  
Rate Sensitivity ◽  
Melting Process ◽  
Mechanical Tests ◽  
Hopkinson Pressure Bar

Ti-6Al-4V alloy is one of the most important engineering alloys, combining attractive properties with inherent workability. The aim of this study is to investigate the effect of strain rate on the compressive mechanical properties of Ti6Al4V alloy manufactured by a selective laser melting process. The mechanical tests were performed by means of a compression split Hopkinson pressure bar apparatus under high strain rate ranging from 1400 s-1 to 4500 s-1. The true stress-strain curves obtained from static and dynamic compressive tests show strain rate sensitivity from quasi-static (peak strength 1300MPa) to high strain rate (peak 1500 MPa). Within the high strain rate range tested, the strain rate sensitivity is not remarkable. The fractographic analysis shows a relatively smooth and smeared fractured surface along with a dimple like structure. The observation of elongated dimples confirms the operation of a dynamic shear failure mechanism for the additively manufactured Ti-6Al-4V parts.

Effect of Strain Rate on Constitutive Behavior of AA-5052 H34

2013 ◽  
Vol 535-536 ◽  
pp. 60-63 ◽  
Author(s):  
Prince Sharma ◽  
Pradeep Chandel ◽  
Vikas Mangla ◽  
Puneet Mahajan ◽  
Manjit Singh
Keyword(s):  
Strain Rate ◽  
Strain Rate Sensitivity ◽  
Split Hopkinson Pressure Bar ◽  
Rate Sensitivity ◽  
Tensile Tests ◽  
Strain Rate Range ◽  
Gauge Length ◽  
Compression Tests ◽  
Hopkinson Pressure Bar ◽  
Rate Range

This paper presents the experimental results to analyze the strain rate sensitivity of aluminium alloy AA-5052 H34. The experiments were carried out under uniaxial tension as well as compression. Tensile tests were carried out with UTM (Zwick Z-250) in the strain rate range of 10-4 to 10-1 s-1 using standard ASTM specimen with gauge length 50mm. Compression tests were carried out in the strain rate range of 10-4 to 103 s-1 using UTM and Split Hopkinson Pressure Bar. Cylindrical specimens of 10mm diameter and 10mm thickness were used for compression experiments. The material showed negative strain rate sensitivity in strain rate from 10-4 to 1 s-1 but showed positive strain rate sensitivity when strain rate increased to 103 s-1. The material was found to be susceptible to Portevin–Le Chatelier effect.

Stress wave propagation effects in split Hopkinson pressure bar tests

1995 ◽  
Vol 449 (1936) ◽  
pp. 187-204 ◽  
Keyword(s):  
Wave Propagation ◽  
Strain Rate ◽  
Stress Wave ◽  
Split Hopkinson Pressure Bar ◽  
Rate Sensitivity ◽  
Stress Wave Propagation ◽  
Hopkinson Pressure Bar ◽  
Propagation Effects ◽  
Split Hopkinson ◽  
Pressure Bar

Studies of the properties of materials at high strain rates by the split Hopkinson pressure bar suggest that most materials show a sharp increase in strain rate sensitivity at high rates. In this paper, analytical and numerical evidence is presented which shows that his apparent increase in the strain rate sensitivity reported in the literature may result from stress wave propagation effects present in the test. A one-dimensional analytical solution has been developed for a rate independent bi-linear material tested in a split Hopkinson pressure bar apparatus. The solution, which is based on a stress wave reverberation model, shows that there is an apparent increase in the strain rate sensitivity of the material which can only be explained in terms of large propagating plastic wave fronts in the specimen. Numerical modelling of the same test geometry for the same input material model is in excellent agreement showing conclusively that stress wave propagation effects are inevitable at high impact velocities. The assumption of uniform stress and strain distribution within a split Hopkinson pressure bar specimen is therefore incorrect at high impact velocities. The formulation of the novel numerical code used in the present work, which is based on the finite volume technique, is also presented.

STUDY ON DYNAMIC FAILURE MODEL OF LEAD-FREE SOLDERS USING SHPB TECHNIQUES

2008 ◽  
Vol 22 (09n11) ◽  
pp. 1117-1122 ◽  
Author(s):  
XIAOYAN NIU ◽  
GUOZHENG YUAN ◽  
ZHIGANG LI ◽  
XUEFENG SHU
Keyword(s):  
Yield Strength ◽  
Strain Rate ◽  
Split Hopkinson Pressure Bar ◽  
Rate Sensitivity ◽  
Material Model ◽  
Lead Free ◽  
Plastic Behavior ◽  
Hopkinson Pressure Bar ◽  
Pressure Bar ◽  
Lead Free Solders

The dynamic compressive properties of 96.3 Sn 3 Ag 0.7 Cu and 99.3 Sn 0.7 Cu solders were studied by means of a split Hopkinson pressure bar at strain rates ranging from 500 to 2000 s−1. Tests were conducted at room temperature and under uniaxial compressive conditions. Eutectic SnPb solders were used as the reference. From the data of tests, it was found that yield strength and flow stress increased remarkably with the increase of strain rate. On logarithmic scales, the yield strength increased linearly with strain rate. These lead-free solders revealed certain visco-plastic behavior and strain rate sensitivity, which predicted using Johnson-Cook material model. Related parameters in the model were determined from the experiment. Compared with the typical Pb -containing solder Sn63Pb37 , these lead-free solders showed some fine properties and could substitute some Pb -containing solder alloys in microelectronic components packaging and interconnects.

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