EFFECT OF MICROSTRUCTURES ON THE DYNAMIC DEFORMATION BEHAVIOR OF Ti-6Al-4V ALLOY

2008 ◽  
Vol 22 (09n11) ◽  
pp. 1221-1227
Author(s):  
JIN-YOUNG KIM ◽  
IN-OK SHIM ◽  
SOON-HYUNG HONG
Keyword(s):  
Strain Rate ◽  
Strain Hardening ◽  
Volume Fraction ◽  
Split Hopkinson Pressure Bar ◽  
Dynamic Deformation ◽  
Testing Machine ◽  
Hydraulic Testing ◽  
Deformation Condition ◽  
Strain Hardening Exponent ◽  
Hopkinson Pressure Bar

The effects of microstructures of Ti -6 Al -4 V alloy on the flow stresses and fracture behaviors at quasi-static and dynamic deformation conditions were investigated. Specimens of different sizes and fractions of α globules in equiaxed and bimodal structures were compressed at the strain rate of 2×10−3/ s and 3×103/ s using hydraulic testing machine and split Hopkinson pressure bar, respectively. The a globule size in equiaxed structure changed the level of flow stresses, but did not affect the strain hardening characteristics. Meanwhile, the volume fraction of α globule (or lamellar phase) in bimodal structures influenced both the flow stress and strain hardening exponent at quasi-static and dynamic deformation conditions. Bimodal structure of 50% lamellar fraction is considered to be more favorable in dynamic deformation condition at strain rate regime of 3×103/ s than equiaxed or bimodal one having higher lamellar fraction.

The Sensitivity of Strain Rate and Size Effect with Different Particle Volume Fraction in SiCp/Al Composite

2009 ◽  
Vol 631-632 ◽  
pp. 513-518 ◽  
Author(s):  
Dong Feng Cao ◽  
Li Sheng Liu ◽  
Hai Mei ◽  
Qing Jie Zhang
Keyword(s):  
Size Effect ◽  
Strain Rate ◽  
Volume Fraction ◽  
Split Hopkinson Pressure Bar ◽  
Particle Volume Fraction ◽  
Testing Machine ◽  
Hopkinson Pressure Bar ◽  
Particle Volume ◽  
Al Composite ◽  
Universal Material Testing Machine

In this paper the sensitivity of strain rate and size effect with different particle volume fraction in SiCp/Al Composite were studied through the experiment. Specimens with 40% and 30% SiC particle volume fraction were made. There are three types of particle sizes in each volume fraction. The sensitivity of strain rate and the effect of particle size in Al matrix composites reinforced with the different volume fraction were investigated, using the split Hopkinson pressure bar and Instron5882 universal material testing machine. The surface microstructure of the specimens in each composite was examined using optical microscopy and SEM. Through the strain-stress curves, the sensitivity of strain rate can be obtained. The experimental results show that the sensitivity of strain rate increases with the increasing of particle volume fraction. At the same volume fraction, the size effect were observed obviously and higher flow stresses were obtained in the composites reinforced with small particles than that in the composite with large particles.

scholarly journals Quasi-Static and Dynamic Compressive Behavior of Gum Metal: Experiment and Constitutive Model

2021 ◽  
Author(s):  
Karol Marek Golasiński ◽  
Jacek Janiszewski ◽  
Judyta Sienkiewicz ◽  
Tomasz Płociński ◽  
Maciej Zubko ◽  
...  
Keyword(s):  
Strain Rate ◽  
Strain Hardening ◽  
Strain Softening ◽  
Split Hopkinson Pressure Bar ◽  
Testing Machine ◽  
Compressive Behavior ◽  
Hopkinson Pressure Bar ◽  
Softening Effect ◽  
Kink Bands ◽  
Gum Metal

AbstractThe quasi-static and high strain rate compressive behavior of Gum Metal with composition Ti-36Nb-2Ta-3Zr-0.3O (wt pct) has been investigated using an electromechanical testing machine and a split Hopkinson pressure bar, respectively. The stress–strain curves obtained for Gum Metal tested under monotonic and dynamic loadings revealed a strain-softening effect which intensified with increasing strain rate. Moreover, the plastic flow stress was observed to increase for both static and dynamic loading conditions with increasing strain rate. The microstructural characterization of the tested Gum Metal specimens showed particular deformation mechanisms regulating the phenomena of strain hardening and strain softening, namely an adiabatic shear band formed at ~ 45 deg with respect to the loading direction as well as widely spaced deformation bands (kink bands). Dislocations within the channels intersecting with twins may cause strain hardening while recrystallized grains and kink bands with crystal rotation inside the grains may lead to strain softening. A constitutive description of the compressive behavior of Gum Metal was proposed using a modified Johnson–Cook model. Good agreement between the experimental and the numerical data obtained in the work was achieved.

scholarly journals Dynamic Impact Response of Ultrafine Grained AA5052 Aluminum Alloy Processed Via Multiaxial Forging at Cryogenic Temperature

2021 ◽  
Vol 12 (3) ◽  
pp. 5082-5094
Author(s):  
O. J. Ajao Et. al.
Keyword(s):  
Aluminum Alloy ◽  
High Strain Rate ◽  
Strain Rate ◽  
Strain Hardening ◽  
High Strain ◽  
Split Hopkinson Pressure Bar ◽  
Strain Hardening Exponent ◽  
Hopkinson Pressure Bar ◽  
Average Grain Size ◽  
Aa5052 Aluminum Alloy

In this study, high strain rate mechanical test was conducted on ultrafine-grained AA5052 aluminum alloy using the Split-Hopkinson Pressure Bar experiment. The AA5052 aluminum alloy was processed via multiaxial forging under cryogenic condition at two different cycles  to achieve grain refinement and ultimately, increase in strength of the material. The average strain rates that the specimens were subjected to during the Split-Hopkinson Pressure Bar experiment ranges from 1000 s-1 to 5000 s-1 at an increment of 1000 s-1. The EBSD map shows that the average grain size of the AA5052 aluminum alloys for the samples processed at 4-cycles is approximately ~900 nm while the samples processed at 6-cycles have a lower average grain size of approximately ~700 nm due to being subjected to more plastic deformation during the processing. The high strain rate deformation process of both specimens was dominated by thermal softening with minima strain hardening effect. During the deformation, the maximum flow stress experienced by samples that was processed at 4-cycles is 410 MPa at 5000 s-1 strain rate while samples processed at 6-cycles has 494 MPa at 3000 s-1. Strain hardenability is not dominant in the deformation mechanism but relative to AA5052 CF (4-cycles), AA5052 CF (6-cycles) has a better strain hardening exponent as the strain rate increases. Both specimens have the highest strain hardening exponent at 1000 s-1 which is 0.1544 and 0.134 for AA5052 CF (4-cycles) and AA5052 CF (6-cycles), respectively. Our results show that AA5052 CF (6-cycles) possesses better mechanical properties under high strain rate in comparison with AA5052 CF (6-cycles).

scholarly journals High Strain-Rate Compressive Properties of Carbon/Epoxy Laminated Composites – Effects of loading direction and temperature

2018 ◽  
Vol 183 ◽  
pp. 02011
Author(s):  
Kenji Nakai ◽  
Tsubasa Fukushima ◽  
Takashi Yokoyama ◽  
Kazuo Arakawa
Keyword(s):  
High Strain Rate ◽  
Strain Rate ◽  
Elevated Temperatures ◽  
High Strain ◽  
Split Hopkinson Pressure Bar ◽  
Slenderness Ratio ◽  
Testing Machine ◽  
Negative Temperature ◽  
Hopkinson Pressure Bar ◽  
Instron Testing Machine

The high strain-rate compressive characteristics of a cross-ply carbon/epoxy laminated composite in the three principal material directions or fibre (1-), in-plane transverse (2-) and throughthickness (3-) directions are investigated on the conventional split Hopkinson pressure bar (SHPB) over a range of temperatures between 20 and 80 °C. A nearly 10 mm thick cross-ply carbon/epoxy composite laminate fabricated using vacuum assisted resin transfer molding (VaRTM) was tested. Cylindrical specimens with a slenderness ratio (= length/diameter) of 0.5 are used in high strain-rate tests, and those with the slenderness ratios of 1.0 and 1.5 are used in low and intermediate strain-rate tests. The uniaxial compressive stress-strain curves up to failure at quasi-static and intermediate strain rates are measured on an Instron testing machine at elevated temperatures. A pair of steel rings is attached to both ends of the cylindrical specimens to prevent premature end crushing in the 1-and 2-direction tests on the Instron testing machine. It is shown that the ultimate compressive strength (or failure stress) exhibits positive strainrate effects and negative temperature ones over a strain-rate range of 10–3 to 103/s and a temperature range of 20 to 80 °C in the three principal material directions.

Strain-Rate Relationship of Aluminum Matrix Composites Predicted by Johnson-Cook Model

2011 ◽  
Vol 704-705 ◽  
pp. 935-940
Author(s):  
De Zhi Zhu ◽  
Wei Ping Chen ◽  
Yuan Yuan Li
Keyword(s):  
Strain Rate ◽  
Volume Fraction ◽  
Split Hopkinson Pressure Bar ◽  
Dynamic Compression ◽  
Aluminum Matrix ◽  
Rate Sensitivity ◽  
Aluminum Matrix Composites ◽  
Matrix Composites ◽  
Hopkinson Pressure Bar ◽  
Cook Model

Strain-rate sensitivities of 55-65vol.% aluminum 2024-T6/TiB2composites and the corresponding aluminum 2024-T6 matrix were investigated using split Hopkinson pressure bar. Results showed that 55-65vol.% aluminum 2024-T6/TiB2composites exhibited significant strain-rate sensitivities, which were three times higher than that of the aluminum 2024-T6 matrix. The strain-rate sensitivity of the aluminum 2024-T6 matrix composites rose obviously with reinforcement content increasing (up to 60%), which agreed with the previous researches. The aluminum 2024-T6/TiB2composites showed hybrid fracture characteristics including particle cracking and aluminum alloy softening under dynamic loading. The flow stresses predicted by Johnson-Cook model increased slowly when the reinforcement volume fraction ranged in 10%-40%. While the reinforcement volume fraction was over 40%, the flow stresses of aluminum matrix composites increased obviously and the strains dropped sharply. Keywords: Composite materials; Dynamic compression; Stress-strain relationship

Size Effect Analysis during Material Deformation with High Strain Rate

2013 ◽  
Vol 589-590 ◽  
pp. 198-203
Author(s):  
Feng Jiang ◽  
Lan Yan ◽  
Zhong Wei Hu ◽  
Yi Ming(Kevin) Rong
Keyword(s):  
Shear Stress ◽  
Size Effect ◽  
Strain Rate ◽  
Split Hopkinson Pressure Bar ◽  
Failure Strain ◽  
Testing Machine ◽  
Hopkinson Pressure Bar ◽  
Dynamic Impact ◽  
Impact Tests ◽  
Material Deformation

The goal of this study is to analyze the material deformation behavior in the micron level by quasi-static and dynamic impact tests of hat shaped specimen. Three type of specimen with different shear ring thicknesses (800μm, 400μm, 50μm) were designed. The quasi-static and dynamic impact tests were performed by electronic universal testing machine and split Hopkinson pressure bar (SHPB) respectively. During the material deformation in the SHPB test, the value scope of strain is 0 to 9 while the value scope of strain rate is 0.001s-1 to 400000s-1. The size effect phenomenon on shear stress and failure strain with different shear ring thickness was investigated. The shear stress and failure strain of material increases with the decrease of shear ring thickness. And the size effect phenomenon was weakened with the increase of strain rate.

Dynamic Deformation Behavior of Rubber under High Strain Rate Compressive Loading

2003 ◽  
Vol 17 (08n09) ◽  
pp. 1415-1420 ◽  
Author(s):  
Ouk Sub Lee ◽  
Myun Soo Kim ◽  
Kyoung Joon Kim ◽  
Si Won Hwang ◽  
Kyu Sang Cho
Keyword(s):  
Strain Rate ◽  
Deformation Behavior ◽  
Split Hopkinson Pressure Bar ◽  
Dynamic Deformation ◽  
Compressive Loading ◽  
Hopkinson Pressure Bar ◽  
Split Hopkinson ◽  
Transition Points ◽  
Dynamic Deformation Behavior ◽  
Pressure Bar

A specific experimental method, the split Hopkinson pressure bar (SHPB) technique is used to determine the dynamic material properties under the impact compressive loading condition with strain-rate of the order of 103/s~104/s. The dynamic deformation behavior of rubber materials widely used for the isolation of vibration from varying structures under dynamic loading is determined by using the Split Hopkinson Pressure Bar technique. The relationships between the stresses at transition points of rubber materials and the strain rate are found to be bilinear. However, an interesting relationship between the strains at transition points of rubber materials and the strain rate, which needs further investigation, is noted.

Study of the Microstructure of AZ31B Magnesium Alloy under High Strain Rate Deformation

2011 ◽  
Vol 686 ◽  
pp. 325-331 ◽  
Author(s):  
Ping Li Mao ◽  
Zheng Liu ◽  
Chang Yi Wang ◽  
Zhi Wang
Keyword(s):  
Magnesium Alloy ◽  
High Strain Rate ◽  
Strain Rate ◽  
High Strain ◽  
Volume Fraction ◽  
Split Hopkinson Pressure Bar ◽  
Prismatic Slip ◽  
Hopkinson Pressure Bar ◽  
Az31b Magnesium Alloy ◽  
High Strain Rate Deformation

In order to investigate the microstructure evolution under high strain rate deformation of magnesium alloy, AZ31B magnesium alloy was impacted by Split Hopkinson Pressure Bar within the strain rates of 496s-1 to 2120s-1, then the specimens were observed by optical microscopy. The results show that when the strain rate are relatively low (496s-1-964s-1), the microstructure is predominated by high density of twinning, while increase the strain rate to 2120s-1 the volume fraction of twins is decreased. This implies that at relatively lower strain rate the deformation mechanism of AZ31B magnesium alloy under impact loading is twinning; increasing the strain rate the prismatic slip and pyramidal slip may be active besides twinning.

Dynamic Testing at High Strain Rates of AZ31 Magnesium Alloys on SHPB Equipment

2013 ◽  
Vol 303-306 ◽  
pp. 2648-2651
Author(s):  
Xu Qing Chang ◽  
Tie Hua Ma
Keyword(s):  
Strain Rate ◽  
Optical Microscopy ◽  
Strain Hardening ◽  
High Strain ◽  
Split Hopkinson Pressure Bar ◽  
Mg Alloy ◽  
Strain Rates ◽  
Hopkinson Pressure Bar ◽  
High Strain Rates ◽  
Az31 Mg Alloy

The mechanical behaviour of as-cast AZ31 Mg alloy has been investigated at strain rates up to 2.0×103s-1. Dynamic tests were carried out at room temperature using a Split Hopkinson Pressure Bar (SHPB) apparatus. Microstructural characteristic were analysed by Image MAT A1 optical microscopy. The results demonstrated that AZ31 Mg alloy exhibited obvious yield phenomena and strain hardening behaviour at high strain rates. The basically same curvature of stress-strain curves exhibited an similar strain hardening rate. The dynamic yield strength changes little and the peak stress increases with the strain rates. An examination by optical microscopy after high strain rate deformation reveals the occurrence of twinning and twin area percentage increases with the strain rate increasing.

Effect of Foam Structure on Impact Compressive Properties in Foamed Polyethylene Film

2016 ◽  
Vol 715 ◽  
pp. 159-164 ◽  
Author(s):  
Kohei Tateyama ◽  
Hiroyuki Yamada ◽  
Nagahisa Ogasawara
Keyword(s):  
Flow Stress ◽  
Strain Rate ◽  
Split Hopkinson Pressure Bar ◽  
Testing Machine ◽  
Polyethylene Film ◽  
Elastic Response ◽  
Hopkinson Pressure Bar ◽  
Compressive Properties ◽  
Foam Structure ◽  
The Impact

The purpose of this study is to elucidate the effect of foam structure on the impact compressive properties of foamed polyethylene film. Three types of foamed PE film were prepared, which have different foam structure: base type, spheral type and dense type. A quasi-static test was performed using a universal testing machine at the strain rate of 10-3~10-1s-1. Impact tests were carried out using a drop-weight testing machine at the strain rate of 101~102s-1 and using a split Hopkinson pressure bar method at the strain rate of approximately 103s-1. It was confirmed that the foamed PE film shows an increase of the flow stress with increasing of the strain rate, regardless of the specimen type. In the spheral type specimen, the elastic response is observed immediately after compression because the cell shape of this specimen has high bending resistance in comparison with the other two specimens. In addition, it is confirmed that the relative density and cell size affects the flow stress in the foamed PE film.

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