scholarly journals Numerical Study on the Fatigue Limit of Metallic Glasses under Cyclic Tension-Compression Loading

Materials ◽  
2020 ◽  
Vol 13 (7) ◽  
pp. 1732
Author(s):  
Jinfeng Yan ◽  
Wenjun Meng ◽  
Zhi Chen ◽  
Hong Guo ◽  
Xianguo Yan
Keyword(s):  
Fatigue Life ◽  
Metallic Glass ◽  
Fatigue Limit ◽  
Free Volume ◽  
Strain Amplitude ◽  
Numerical Study ◽  
Hydrostatic Stress ◽  
Shear Banding ◽  
Engineering Application ◽  
Free Volume Theory

Numerical study was performed to determine the fatigue limit of metallic glass under tension-compression cyclic loading. A revised free-volume theory which considers the hydrostatic stress was utilized to make the predictions. Systematical simulations showed that a higher strain amplitude is prone to making the sample completely damaged earlier. However, lower strain fluctuations could result in a longer fatigue life. Shear banding evolution history described by free-volume localization could reasonably explain the mechanical responses of different samples. In addition, compressive loading could give rise to a higher stress than that under tensile loading because of hydrostatic stress contribution. In the end, a correlation between fatigue life and applied strain amplitude was plotted which could supply a guidance for designing the engineering application of metallic glass under periodic loading.

Numerical Determination of Critical Configuration for Mechanical Properties of Metallic Glasses with Notches

2021 ◽  
Vol 13 (2) ◽  
pp. 235-244
Author(s):  
J. F. Yan ◽  
W. J. Meng ◽  
Z. Chen ◽  
H. Guo ◽  
X. G. Yan
Keyword(s):  
Mechanical Properties ◽  
Metallic Glass ◽  
Free Volume ◽  
Numerical Study ◽  
Uniform Elongation ◽  
Shear Banding ◽  
Volume Distribution ◽  
Geometrical Configuration ◽  
Free Volume Theory ◽  
Critical Configuration

A numerical study based on a revised free-volume theory was carried out to determine the critical configuration for mechanical properties in metallic glass with notches. Firstly, parameters being used in constitutive laws were developed and validated to quantitatively describe the asymmetry of tension and compression. Then, systematical simulations under compressive loadings were performed on samples where different horizontal width and vertical distance of two adjacent notches were designed. Engineering stress-strain curves, global strength and uniform elongation were plotted against individual geometrical configuration. Analyses were carried out to reveal the shear banding process of different samples by means of free-volume distribution obtained by simulations. Conclusive illustration recommended a geometrical configuration by which notched samples could display a remarkable plasticity and high strength. It is helpful to material fabrication for metallic glass based porous materials.

scholarly journals Notch Effect on Plastic Deformation of Metallic Glass: A Numerical Study by Revised Free-Volume Theory

2020 ◽  
Vol 2020 ◽  
pp. 1-13
Author(s):  
J. F. Yan ◽  
W. J. Meng ◽  
Z. Chen ◽  
H. Guo ◽  
X. G. Yan
Keyword(s):  
Metallic Glass ◽  
Free Volume ◽  
Numerical Study ◽  
Shear Bands ◽  
Notch Effect ◽  
Volume Distribution ◽  
Free Volume Theory ◽  
Tension And Compression ◽  
Strength Asymmetry ◽  
Strength And Plasticity

By means of a revised free-volume theory, the notch effect on metallic glass was systematically investigated by the numerical method. Simulations on specimens without notches demonstrated that the parameters being determined in this work could reasonably describe the strength asymmetry of tension and compression. Moreover, four samples with different notches were used to numerically investigate the notch effect on global strength and plasticity. A better agreement could also be achieved between current simulations with existing experimental results, compared with another free-volume model. Combined with the free-volume distribution during deformation process, it was proven that the intersection of two major shear bands is the cause for the strength and plasticity enhancement found in sample with two symmetric notches. Besides, strength asymmetry between tension and compression was also found for notched samples. Compressive strengths are accordingly higher than tensile ones. Moreover, with the augment of the aspect ratio, the plasticity for specimens with two symmetric notches was found to increase firstly and then decrease afterwards.

Plastic flow in dynamic compression of a Zr-based bulk metallic glass

2006 ◽  
Vol 21 (6) ◽  
pp. 1570-1575 ◽  
Author(s):  
W.H. Jiang ◽  
F.X. Liu ◽  
D.C. Qiao ◽  
H. Choo ◽  
P.K. Liaw
Keyword(s):  
Metallic Glass ◽  
Bulk Metallic Glass ◽  
Free Volume ◽  
Plastic Flow ◽  
Dynamic Compression ◽  
Maximum Shear Stress ◽  
Shear Banding ◽  
Shear Bands ◽  
Free Volume Model ◽  
Geometrically Constrained

Using geometrically constrained specimens, the plastic flow behaviors of the as-cast and the relaxed Zr52.5Cu17.9Ni14.6Al10.0Ti5.0 bulk metallic glass in the dynamic compression were investigated. Both alloys exhibit a significant plasticity in the dynamic compression. The plastic deformation in both alloys is still inhomogeneous, which is characterized by the serrated plastic flow and the formation of shear bands. Free volumes affect the shear banding and the plastic flow. The reduced free volume results in the deviation of the shear banding direction from the maximum shear stress. The relaxed alloy exhibits the obvious stress overshoot, which is consistent with the theoretical prediction using a free volume model.

Effect of high pressure on glass transition in Zr-Ti-Cu-Ni-Be bulk metallic glass

2002 ◽  
Vol 754 ◽  
Author(s):  
Wei Hua Wang ◽  
Ping Wen ◽  
Yan Hui Zhao ◽  
Ming Xiang Pan ◽  
De Qian Zhao
Keyword(s):  
High Pressure ◽  
Glass Transition ◽  
Transition Temperature ◽  
Glass Transition Temperature ◽  
Metallic Glass ◽  
Bulk Metallic Glass ◽  
Free Volume ◽  
Bulk Glass ◽  
Free Volume Theory ◽  
Glass Forming

ABSTRACTA new method is developed to directly exhibit glass transition in Zr-Ti-Cu-Ni-Be bulk glass-forming alloy under high pressure in metallic glass. Via the method, we derive an increase of glass transition temperature, Tg with pressure of 5.6 K/GPa, and a formation volume (ΔVf) of 6.5 Å3 for diffusion and the migration volume (ΔVm) of 6.5 Å3. The glass transition under high pressure is simulated based on the free-volume theory, and the simulations are consistent with the experimental observations.

scholarly journals Characterization of rate-dependent shear behavior of Zr-based bulk metallic glass using shear-punch testing

2006 ◽  
Vol 21 (1) ◽  
pp. 153-160 ◽  
Author(s):  
L.F. Liu ◽  
L.H. Dai ◽  
Y.L. Bai ◽  
B.C. Wei ◽  
J. Eckert
Keyword(s):  
Metallic Glass ◽  
Strain Rate ◽  
Bulk Metallic Glass ◽  
Shear Banding ◽  
Shear Bands ◽  
Transfer Model ◽  
Free Volume Theory ◽  
Rate Dependent ◽  
Shear Punch ◽  
Shear Punch Testing

In this study, the rate-dependent mechanical behavior of a Zr41.2Ti13.8Cu12.5Ni10Be22.5 bulk metallic glass was studied using quasi-static and dynamic shear-punch testing at room temperature. The results demonstrate that the shear strength of this alloy is insensitive to the applied strain rate. However, the formation of shear bands and the serrated flow exhibits a significant strain rate effect. The shear banding-induced fracture patterns and the fracture-melting phenomenon were analyzed based on the free volume theory and the energy transfer model.

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