scholarly journals Constant Strain Rate Uniaxial Compression of Green Sandstone during SHPB Tests Driven by Pendulum Hammer

2017 ◽  
Vol 2017 ◽  
pp. 1-12 ◽  
Author(s):  
S. H. Li ◽  
W. C. Zhu ◽  
L. L. Niu ◽  
F. Dai
Keyword(s):  
Strain Rate ◽  
Split Hopkinson Pressure Bar ◽  
Constant Strain Rate ◽  
Dynamic Strength ◽  
Curvature Radius ◽  
Strain Rates ◽  
Rate Dependency ◽  
Hopkinson Pressure Bar ◽  
Special Shape ◽  
Special Shape Striker

During the Split-Hopkinson pressure bar (SHPB) tests driven by pendulum hammer, employing a proper special shape striker is an effective way to obtain dynamic stress equilibrium condition and to get constant strain rate of the rock specimen. To find the proper special shape striker, a striker with a cambered surface was introduced and eight geometrically different hammers were designed to analyze the effect of hammer geometry on the waveform of excited incident stress waves. Based on experiments and simulations, parameter effects, including the cambered hammer curvature radius and hammer diameter, length, and impact velocity, on the incident wave shape were examined. These parametric studies provided guidelines for achieving constant strain rates in rock specimens during SHPB tests. The use of different diameter hammers was noted for shaping stress-time curves to follow the stress-strain behavior of green sandstone. Finally, to examine the applicability of using hammer geometry for shaping incident waves to achieve constant strain rate, SHPB tests on green sandstone specimens were conducted. The results demonstrated that a constant strain rate (100 s−1) lasting for 70 μs was achieved with the 8# hammer (3.7 kg; curvature radius, diameter, and length of 100, 70, and 126.3 mm, resp.). In addition, dynamic experiments on green sandstone were carried out under various strain rates and the results showed that the initial tangential modulus was almost unaffected by strain rate. The strain at peak stress tended to increase with rising strain rate and the dynamic strength of green sandstone showed an apparent rate dependency.

One-Dimensional Dynamic Compressive Behavior of EPDM Rubber

2003 ◽  
Vol 125 (3) ◽  
pp. 294-301 ◽  
Author(s):  
B. Song ◽  
W. Chen
Keyword(s):  
Strain Rate ◽  
High Speed ◽  
Dynamic Stress ◽  
Split Hopkinson Pressure Bar ◽  
Constant Strain Rate ◽  
Strain Rates ◽  
Hopkinson Pressure Bar ◽  
Stress Strain ◽  
Epdm Rubber ◽  
One Dimensional

Dynamic compressive stress-strain curves at various strain rates of an Ethylene-Propylene-Diene Monomer Copolymer (EPDM) rubber have been determined with a modified split Hopkinson pressure bar (SHPB). The use of a pulse-shaping technique ensures that the specimen deforms at a nearly constant strain rate under dynamically equilibrated stress. The validity of the experiments was monitored by a high-speed digital camera for specimen edge deformation, and by piezoelectric force transducers for dynamic stress equilibrium. The resulting dynamic stress-strain curves for the EPDM indicate that the material is sensitive to strain rates and that the strain-rate sensitivity depends on the value of strain. Based on a strain energy function theory, a one-dimensional dynamic constitutive equation for this rubber was modified to describe the high strain-rate experimental results within the ranges of strain and strain rates presented in this paper.

scholarly journals Effects of Cu Addition on Mechanical Behaviour, Microstructural Evolution and Anti-Corrosion Performance of TiAl-Based Intermetallic Alloy under Different Strain Rates

Materials ◽  
2021 ◽  
Vol 14 (17) ◽  
pp. 5056
Author(s):  
Cheng-Hsien Kuo ◽  
Tao-Hsing Chen ◽  
Ting-Yang Zeng
Keyword(s):  
Flow Stress ◽  
Strain Rate ◽  
Fracture Strain ◽  
Split Hopkinson Pressure Bar ◽  
Constant Strain Rate ◽  
Rate Sensitivity ◽  
Strain Rates ◽  
Phase Content ◽  
Corrosion Performance ◽  
Hopkinson Pressure Bar

TiAl-based intermetallic alloys are prepared with Cu concentrations of 3–5 at.% (atomic ratio). The mechanical properties and microstructural characteristics of the alloys are investigated under static and dynamic loading conditions using a material testing system (MTS) and split-Hopkinson Pressure Bar (SHPB), respectively. The electrochemical properties of the various alloys are then tested in Ringer’s solution. It is shown that the level of Cu addition significantly affects both the flow stress and the ductility of the samples. For Cu contents of 3 and 4 at.%, respectively, the flow stress and strain rate sensitivity increase at higher strain rates. Furthermore, for a constant strain rate, a Cu content of 4 at.% leads to an increased fracture strain. However, for the sample with the highest Cu addition of 5 at.%, the flow stress and fracture strain both decrease. The X-ray diffraction (XRD) patterns and optical microscopy (OM) images reveal that the lower ductility is due to the formation of a greater quantity of γ phase in the binary TiAl alloy system. Among all the specimens, that with a Cu addition of 4 at.% has the best anti-corrosion performance. Overall, the results indicate that the favourable properties of the TiAlCu4 sample stem mainly from the low γ phase content of the microstructure and the high α2 phase content.

Dynamic Stress-Strain Response and Failure Behavior of PMMA

2003 ◽  
Author(s):  
Paul Moy ◽  
Tusit Weerasooriya ◽  
Wayne Chen ◽  
Alex Hsieh
Keyword(s):  
Strain Rate ◽  
Strain Hardening ◽  
Dynamic Stress ◽  
Split Hopkinson Pressure Bar ◽  
Compressive Loading ◽  
Constant Strain Rate ◽  
High Rate ◽  
Failure Behavior ◽  
Strain Rates ◽  
Hopkinson Pressure Bar

Strain rate response of PMMA was investigated under uniaxial compression at different rates of strain ranging from 0.0001/sec to about 4300/sec. High rate experiments (greater than 1/sec rates) were conducted using a split-Hopkinson Pressure bar (SHPB) with pulse-shaping to impose the compressive loading of the specimen at constant strain rate under dynamic stress equilibrium. At strain rates 1/s and below, intrinsic softening occurred after the initial yield and then followed by the strain hardening. However, at 1/s strain rate, material started to soften further due to thermal softening dominating over strain hardening. For higher strain rates (greater than 1/s), PMMA failed before, during or immediately after the yield depending on the rate of loading. For these high rates, strain to failure decreases with the increase in the strain rates whereas failure stress (except at very high rates where failure occurred before yielding) and modulus increase with increasing strain rate.

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 Dynamic Characteristics of Deep Dolomite Under One-Dimensional Static and Dynamic Loads

2019 ◽  
Vol 101 (1) ◽  
pp. 49-56 ◽  
Author(s):  
Jianguo Wang ◽  
Yang Liu ◽  
Kegang Li
Keyword(s):  
Strain Rate ◽  
Axial Compression ◽  
Split Hopkinson Pressure Bar ◽  
Dynamic Strength ◽  
Strong Positive Correlation ◽  
Hopkinson Pressure Bar ◽  
Irreversible Damage ◽  
One Dimensional ◽  
Rock Structure ◽  
The Impact

AbstractThe failure characteristics of rock subjected to impact disturbance under one-dimensional static axial compression are helpful for studying the problems of pillar instability and rock burst in deep, high geostress surrounding rock under blasting disturbances. Improved split Hopkinson pressure bar equipment was used for one-dimensional dynamic–static combined impact tests of deep-seated dolomite specimens under axial compression levels of 0, 12, 24, and 36 MPa. The experimental results demonstrate that the dolomite specimens exhibit strong brittleness. The dynamic strength always maintains a strong positive correlation with the strain rate when the axial compression is fixed; when the strain rate is close, the dynamic elasticity modulus and peak strength of the specimens first increase and then decrease with the increase in axial compression, and the peak value appears at 24 MPa. The impact resistance of specimens can be enhanced when the axial compression is 12 or 24 MPa, but when it increases to 36 MPa, the damage inside the specimen begins to cause damage to the dynamic rock strength. Prior to the rock macroscopic failure, the axial static load changes the rock structure state, and it can store strain energy or cause irreversible damage.

High Strain Rate Compressive Behavior of Micro-Fibre Reinforced Fine Grained Cementitious Composite

2018 ◽  
Vol 276 ◽  
pp. 140-147
Author(s):  
Martina Drdlová ◽  
Miloslav Popovič ◽  
René Čechmánek
Keyword(s):  
High Strain Rate ◽  
Strain Rate ◽  
High Strain ◽  
Split Hopkinson Pressure Bar ◽  
Compressive Strain ◽  
Fibre Reinforcement ◽  
Strain Rates ◽  
Cementitious Composite ◽  
Compressive Behavior ◽  
Hopkinson Pressure Bar

This paper presents an experimental study on the high strain rate compressive behavior of micro-fibre reinforced ultrahigh performance cementitious composite, which is intended to be used as a matrix for slurry infiltrated fibre concrete (SIFCON). Cementitious composite specimens with 5 different types of microfibres, namely aramid, carbon, wollastonite, polypropylene and glass in amounts of 1.5-2.0% by volume were prepared and investigated. Split Hopkinson pressure bar (SHPB) equipment was used to determine the cementitious composite behavior at strain rates up to 1600 s-1. Quasistatic tests were performed, as well and ratios of these properties at high strain rates to their counterparts at static loading were compared. The dynamic increase factors were calculated. Strain rate sensitivity was observed - compressive strength was found to be increased with strain rate for all tested specimens. Peak stress values, critical compressive strain and post peak behaviour varies for specimens with different micro-fibre reinforcement, which allows to find the optimal reinforcement for high strain rate impacted structures.

scholarly journals Dynamic Constitutive Model of Ultra-High Molecular Weight Polyethylene (UHMWPE): Considering the Temperature and Strain Rate Effects

Polymers ◽  
2020 ◽  
Vol 12 (7) ◽  
pp. 1561 ◽  
Author(s):  
Kebin Zhang ◽  
Wenbin Li ◽  
Yu Zheng ◽  
Wenjin Yao ◽  
Changfang Zhao
Keyword(s):  
Mechanical Properties ◽  
Constitutive Model ◽  
Strain Rate ◽  
Split Hopkinson Pressure Bar ◽  
Plastic Material ◽  
Strain Rates ◽  
Hopkinson Pressure Bar ◽  
Ballistic Performance ◽  
Stress Strain ◽  
Different Temperatures

The temperature and strain rate significantly affect the ballistic performance of UHMWPE, but the deformation of UHMWPE under thermo-mechanical coupling has been rarely studied. To investigate the influences of the temperature and the strain rate on the mechanical properties of UHMWPE, a Split Hopkinson Pressure Bar (SHPB) apparatus was used to conduct uniaxial compression experiments on UHMWPE. The stress–strain curves of UHMWPE were obtained at temperatures of 20–100 °C and strain rates of 1300–4300 s−1. Based on the experimental results, the UHMWPE belongs to viscoelastic–plastic material, and a hardening effect occurs once UHMWPE enters the plastic zone. By comparing the stress–strain curves at different temperatures and strain rates, it was found that UHMWPE exhibits strain rate strengthening and temperature softening effects. By modifying the Sherwood–Frost model, a constitutive model was established to describe the dynamic mechanical properties of UHMWPE at different temperatures. The results calculated using the constitutive model were in good agreement with the experimental data. This study provides a reference for the design of UHMWPE as a ballistic-resistant material.

Studies on the Dynamic Compressive Properties of Open-Celled Aluminum Alloy Foams

2006 ◽  
Vol 306-308 ◽  
pp. 905-910 ◽  
Author(s):  
Zhi Hua Wang ◽  
Hong Wei Ma ◽  
Long Mao Zhao ◽  
Gui Tong Yang
Keyword(s):  
Yield Strength ◽  
Strain Rate ◽  
Split Hopkinson Pressure Bar ◽  
Strain Rates ◽  
Hopkinson Pressure Bar ◽  
Aluminum Foams ◽  
Wide Range ◽  
Split Hopkinson ◽  
Pressure Bar ◽  
Dynamic Loading Conditions

The compressive deformation behavior of open-cell aluminum foams with different densities and morphologies was assessed under quasi-static and dynamic loading conditions. High strain rate experiments were conducted using a split Hopkinson pressure bar technique at strain rates ranging from 500 to 1 2000 − s . The experimental results shown that the compressive stress-strain curves of aluminum foams also have the “ three regions” character appeared in general foam materials, namely elastic region, collapse region and densification regions. It is found that density is the primary variable characterizing the modulus and yield strength of foams and the cell appears to have a negligible effect on the strength of foams. It also is found that yield strength and energy absorption is almost insensitive to strain rate and deformation is spatially uniform for the open-celled aluminum foams, over a wide range of strain rates.

High Strain Rate and High Temperature Behavior of Ti–6Al–4V Alloy Under Compressive Loading

2018 ◽  
Vol 140 (2) ◽  
Author(s):  
Nitin B. Bhalerao ◽  
Suhas S. Joshi ◽  
N. K. Naik
Keyword(s):  
Strain Rate ◽  
Split Hopkinson Pressure Bar ◽  
Dynamic Equilibrium ◽  
Dynamic Properties ◽  
Weight Ratio ◽  
High Rate ◽  
Material Strength ◽  
Strain Rates ◽  
Hopkinson Pressure Bar ◽  
Two Phase

The titanium alloy (grade 5) is a two-phase material, which finds significant applications in aerospace, medical, marine fields, owing to its superior characteristics like high strength-to-weight ratio, excellent corrosion resistance, and good formability. Hence, the dynamic characteristics of the Ti-6Al-4V alloy are an important area to study. A compressive split Hopkinson pressure bar (SHPB) was used to evaluate the dynamic properties of Ti-6Al-4V alloy under various strain rates between 997 and 1898s−1, and at temperatures between −10 °C and 320 °C. It was evident that the material strength is sensitive to both strain rate and temperature; however, the latter is more predominant than the former. The microstructure of the deformed samples was examined using electron back-scattered diffraction (EBSD). The microscopic observations show that the dynamic impact characteristics of the alloy are higher at higher strain rates than at quasi-static strain rates. The SHPB tests show that the force on the transmitter bar is lower than the force on the incident bar. This indicates that the dynamic equilibrium cannot be achieved during high rate of damage evolution. Various constants in Johnson–Cook (JC) model were evaluated to validate the results. An uncertainty analysis for the experimental results has also been presented.

High Strain-Rate Compressive Characteristics of Carbon/Epoxy Laminated Composites in Through-Thickness Direction

2004 ◽  
Vol 1-2 ◽  
pp. 11-16 ◽  
Author(s):  
Takashi Yokoyama
Keyword(s):  
Strain Rate ◽  
Split Hopkinson Pressure Bar ◽  
Laminated Composites ◽  
Fiber Direction ◽  
Strain Rates ◽  
Thickness Direction ◽  
Hopkinson Pressure Bar ◽  
Total Strain Energy ◽  
Split Hopkinson ◽  
Pressure Bar

Compressive stress-strain characteristics of carbon/epoxy laminated composites in the through-thickness direction at strain rates of over 1000/s were evaluated using the standard split Hopkinson pressure bar. Three carbon/epoxy laminated composites (i.e., unidirectional, cross-ply and woven) with almost the same thickness were tested at room temperature. Small solid cylindrical specimens were machined such that the direction of the compression loading was perpendicular to the fiber direction of the laminates. The effects of strain rate and reinforcement geometry on the secant modulus at 1% strain, ultimate compressive strength and strain, and total strain energy to failure were examined in detail.

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