Loading and Unloading Split Hopkinson Tension Bar Technique for Studying Dynamic Microstructure Evolution of Materials

2010 ◽  
Vol 160-162 ◽  
pp. 891-894 ◽  
Author(s):  
Wen Huang ◽  
Zhong Wei Huang ◽  
Xiao Qing Zhou
Keyword(s):  
Microstructure Evolution ◽  
Pure Titanium ◽  
Dynamic Mechanical Properties ◽  
Post Test ◽  
Split Hopkinson ◽  
Adiabatic Curve ◽  
Loading And Unloading ◽  
Different Strains ◽  
Strength And Ductility ◽  
Split Hopkinson Tension Bar

In order to investigate the microstructure evolution of materials, loading and unloading experiments with specimens deformed at different strains are required. In this paper, momentum traps were introduced for rendering the conventional Split Hopkinson Tension Bar suitable for loading-unloading experiment. The new technique allows a specimen to be loaded to a preset strain for post-test characterization. This technique was applied to study the dynamic mechanical properties of pure titanium. The results show that: 1) the twinning density of titanium increases rapidly as the strain increases. 2) The strength and ductility of titanium exhibited on the adiabatic curve are much smaller then those exhibited on the isothermal curve, which may be caused by the adiabatic heat generated during the transient deformation process.

Dynamic Constitutive Relation and Fracture Model of Q235A Steel

2013 ◽  
Vol 274 ◽  
pp. 463-466 ◽  
Author(s):  
Li Lin ◽  
Feng Fan ◽  
Xu Dong Zhi
Keyword(s):  
Fracture Strain ◽  
Stress Triaxiality ◽  
Rate Sensitivity ◽  
Experimental Tests ◽  
Model Parameters ◽  
Element Calculation ◽  
Tension Tests ◽  
Split Hopkinson ◽  
Strength And Ductility ◽  
Split Hopkinson Tension Bar

Strength and ductility data for Q235A steel from 20 oC to 950 oC was obtained from a series of experimental tests. The stress rate sensitivity was studied by conducting Split-Hopkinson Tension Bar (SHTB) test and uniaxial tension test on smooth cylindrical specimens while the influence of stress triaxiality on ductility was revealed by conducting upsetting tests, tension tests on pre-notched cylinder specimens and torsion tests on SASs. Slightly modified versions of the two Johnson–Cook (J–C) models describing flow stress and fracture strain are presented to characterize the properties of Q235A steel as function of strain rate, temperature and stress triaxiality. Corresponding model parameters were calibrated based on the test data and with the help of finite element calculation. It was found that the modified Johnson–Cook (MJC) models give more close predictive results compared with the original J–C models.

Parameters Identification of Johnson-Cook Constitutive Equation for Aluminum Brass

2014 ◽  
Vol 887-888 ◽  
pp. 1032-1035 ◽  
Author(s):  
Chang Chun Di ◽  
Kai Bo Cui ◽  
Jun Qi Qin ◽  
Da Lin Wu
Keyword(s):  
Testing Machine ◽  
Strain Curve ◽  
High Strength ◽  
Dynamic Mechanical Properties ◽  
Model Parameters ◽  
Strain Rates ◽  
Stress Strain Curve ◽  
Method Of Least Squares ◽  
Different Temperatures ◽  
Split Hopkinson

Aluminum brass HAL66-6-3-2 is abrasion-resistant alloy with high strength, hardness and wear resistance, corrosion resistance is also well, commonly used in the field of marine and ordnance industry. The quasi static and dynamic mechanical properties were tested through the use of electronic universal testing machine and Split Hopkinson Tension Bar (SHTB). Meanwhile, the material stress-strain curve at different temperatures and different strain rates is also obtained. Based on Johnson-Cook constitutive model, using the method of least squares fitting the experimental data to determine the model parameters, fitting and experimental results agree well.

scholarly journals Development of a True-Biaxial Split Hopkinson Pressure Bar Device and Its Application

Materials ◽  
2021 ◽  
Vol 14 (23) ◽  
pp. 7298
Author(s):  
Shumeng Pang ◽  
Weijun Tao ◽  
Yingjing Liang ◽  
Shi Huan ◽  
Yijie Liu ◽  
...  
Keyword(s):  
Stress Wave ◽  
Impact Loading ◽  
Split Hopkinson Pressure Bar ◽  
Axial Stress ◽  
Dynamic Mechanical Properties ◽  
Stress Waves ◽  
Hopkinson Pressure Bar ◽  
Dynamic Mechanical ◽  
Split Hopkinson ◽  
Pressure Bar

Although highly desirable, the experimental technology of the dynamic mechanical properties of materials under multiaxial impact loading is rarely explored. In this study, a true-biaxial split Hopkinson pressure bar device is developed to achieve the biaxial synchronous impact loading of a specimen. A symmetrical wedge-shaped, dual-wave bar is designed to decompose a single stress wave into two independent and symmetric stress waves that eventually form an orthogonal system and load the specimen synchronously. Furthermore, a combination of ground gaskets and lubricant is employed to eliminate the shear stress wave and separate the coupling of the shear and axial stress waves propagating in bars. Some confirmatory and applied tests are carried out, and the results show not only the feasibility of this modified device but also the dynamic mechanical characteristics of specimens under biaxial impact loading. This novel technique is readily implementable and also has good application potential in material mechanics testing.

scholarly journals Stress Transfer Mechanism of Flange in Split Hopkinson Tension Bar

2020 ◽  
Vol 10 (21) ◽  
pp. 7601
Author(s):  
Hyunho Shin ◽  
Sanghoon Kim ◽  
Jong-Bong Kim
Keyword(s):  
Stress Transfer ◽  
Transfer Mechanism ◽  
Explicit Finite Element ◽  
Impact Theory ◽  
Quantitative Basis ◽  
Split Hopkinson ◽  
One Step ◽  
The One ◽  
The Impact ◽  
Split Hopkinson Tension Bar

To reveal the stress transfer mechanism of the flange in a split Hopkinson tension bar, explicit finite element analyses of the impact of the hollow striker on the flange were performed across a range of flange lengths. The tensile stress profiles monitored at the strain gauge position of the incident bar are interpreted on a qualitative basis using three types of stress waves: bar (B) waves, flange (F) waves, and a series of reverberation (Rn) waves. When the flange length (Lf) is long (i.e., Lf > Ls, where Ls is the striker length), the B wave and first reverberation wave (R1) are fully separated in the time axis. When the flange length is intermediate (~Db < Lf < Ls, where Db is the bar diameter), the B and F waves are partially superposed; the F wave is delayed, then followed by a series of Rn waves after the superposition period. When the flange length is short (Lf < ~Db), the B and F waves are practically fully superposed and form a pseudo-one-step pulse, indicating the necessity of a short flange length to achieve a neat tensile pulse. The magnitudes and periods of the monitored pulses are consistent with the analysis results using the one-dimensional impact theory, including a recently formulated equation for impact-induced stress when the areas of the striker and bar are different, equations for the reflection/transmission ratios of a stress wave, and an equation for pulse duration time. This observation verifies the flange length-dependent stress transfer mechanism on a quantitative basis.

scholarly journals Microstructure evolution of commercial pure titanium during equal channel angular pressing

2010 ◽  
Vol 527 (3) ◽  
pp. 789-796 ◽  
Author(s):  
Y.J. Chen ◽  
Y.J. Li ◽  
J.C. Walmsley ◽  
S. Dumoulin ◽  
P.C. Skaret ◽  
...  
Keyword(s):  
Equal Channel Angular Pressing ◽  
Microstructure Evolution ◽  
Pure Titanium ◽  
Angular Pressing ◽  
Commercial Pure Titanium

scholarly journals The Nucleation and the Intrinsic Microstructure Evolution of Martensite from 332113β Twin Boundary in β Titanium: First-Principles Calculations

Metals ◽  
2019 ◽  
Vol 9 (11) ◽  
pp. 1202 ◽  
Author(s):  
Chen ◽  
Ma ◽  
Wang
Keyword(s):  
Twin Boundary ◽  
Microstructure Evolution ◽  
First Principles ◽  
Atomic Scale ◽  
Clear Understanding ◽  
Intermediate Structure ◽  
First Principles Calculations ◽  
Ti Alloys ◽  
Α Phase ◽  
Strength And Ductility

A clear understanding on the inter-evolution behaviors between 332113β twinning and stress-induced martensite (SIM) α″ in β-Ti alloys is vital for improving its strength and ductility concurrently. As the preliminary step to better understand these complex behaviors, the nucleation and the intrinsic microstructure evolution of martensite α″ from 332113β twin boundary (TB) were investigated in pure β-Ti at atomic scale using first-principles calculations in this work. We found the α″ precipitation prefers to nucleate and grow at 332113β TB, with the transformation of 332113β TB→130310α” TB. During this process, α″ precipitation firstly nucleates at 332113β TB and, subsequently, it grows inwards toward the grain interiors. This easy transition may stem from the strong crystallographic correspondence between 332113β and 130310α” TBs, and the region close to the 332113β TB presents the characteristics of intermediate structure between β and α″ phases. Kinetics calculations indicate the α″ phase barrierlessly nucleates at 332113β TB rather than in grain interior, where there is higher critical driving energy. Our calculations provide a unique perspective on the “intrinsic” microstructure evolution of martensite α″ from 332113β TB, which may deepen our understanding on the precipitation of martensite α″ and the inter-evolution behaviors between 332113β twinning and martensite α″ in β-Ti alloys at atomic scale.

EBSD Investigation of Cold Rolled and Recrystallized Titanium

2013 ◽  
Vol 753 ◽  
pp. 289-292
Author(s):  
Mariusz Jedrychowski ◽  
Jacek Tarasiuk ◽  
Brigitte Bacroix
Keyword(s):  
Thermomechanical Treatment ◽  
Microstructure Evolution ◽  
Texture Evolution ◽  
Pure Titanium ◽  
Commercially Pure Titanium ◽  
Topological Maps ◽  
Air Atmosphere ◽  
Commercially Pure ◽  
Cold Rolled

EBSD investigation of texture and microstructure evolution during a complete thermomechanical treatment of commercially pure titanium (HCP-Ti) is presented. Titanium was cold rolled to reach various degrees of thickness reduction: 20%, 40% and 60%. Next, annealing in air atmosphere was conducted at different conditions to achieve the recrystallized state. EBSD topological maps were measured on RD-TD and RD-ND surface of each sample. Strong heterogeneity of deformed titanium microstructures is described with focus on the important role of twinning mechanisms. Texture evolution in investigated titanium appears to be limited, especially in recrystallized state. However some subtle mechanisms are discussed.

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