Dynamic Failure Mechanisms in Beryllium-Bearing Bulk Metallic Glasses

1998 ◽  
Vol 554 ◽  
Author(s):  
David M. Owen ◽  
Ares J. Rosakis ◽  
William L. Johnson
Keyword(s):  
Crack Initiation ◽  
Shear Band ◽  
Metallic Glasses ◽  
Impact Loading ◽  
High Speed ◽  
Failure Mechanisms ◽  
Shear Bands ◽  
Dynamic Crack ◽  
Dynamic Failure ◽  
Asymmetric Impact

AbstractThe understanding of dynamic failure mechanisms in bulk metallic glasses is important for the application of this class of materials to a variety of engineering problems. This is true not only for design environments in which components are subject to high loading rates, but also when components are subjected to quasi-static loading conditions where observations have been made of damage propagation occurring in an unstable, highly dynamic manner. This paper presents preliminary results of a study of the phenomena of dynamic crack initiation and growth as well as the phenomenon of dynamic localization (shear band formation) in a beryllium-bearing bulk metallic glass, Zr41.25Ti13.75Ni10Cu12.75Be22.5. Pre-notched and prefatigued plate specimens were subjected to quasi-static and dynamic three-point bend loading to investigate crack initiation and propagation. Asymmetric impact loading with a gas gun was used to induce dynamic shear band growth. The mechanical fields in the vicinity of the dynamically loaded crack or notch tip were characterized using high-speed optical diagnostic techniques. The results demonstrated a dramatic increase in the crack initiation toughness with loading rate and subsequent crack tip speeds approaching 1000 m s−1. Dynamic crack tip branching was also observed under certain conditions. Shear bands formed readily under asymmetric impact loading. The shear bands traveled at speeds of approximately 1300 m s−1 and were accompanied by intense localized heating measured using high-speed full-field infrared imaging. The maximum temperatures recorded across the shear bands were in excess of 1500 K.

FRACTURE BEHAVIOR OF Zr-BASED BULK METALLIC GLASS UNDER IMPACT LOADING

2006 ◽  
Vol 20 (25n27) ◽  
pp. 4359-4364 ◽  
Author(s):  
HYUNG-SEOP SHIN ◽  
KI-HYUN KIM ◽  
SANG-YEOB OH
Keyword(s):  
Fracture Toughness ◽  
Crack Initiation ◽  
Fracture Energy ◽  
Impact Loading ◽  
Static Loading ◽  
Fracture Behavior ◽  
Loading Rate ◽  
Shear Bands ◽  
Maximum Load ◽  
Cu Alloy

The fracture behavior of a Zr -based bulk amorphous metal under impact loading using subsize V-shaped Charpy specimens was investigated. Influences of loading rate on the fracture behavior of amorphous Zr - Al - Ni - Cu alloy were examined. As a result, the maximum load and absorbed fracture energy under impact loading were lower than those under quasi-static loading. A large part of the absorbed fracture energy in the Zr -based BMG was consumed in the process for crack initiation and not for crack propagation. In addition, fractographic characteristics of BMGs, especially the initiation and development of shear bands at the notch tip were investigated. Fractured surfaces under impact loading are smoother than those under quasi-static loading. The absorbed fracture energy appeared differently depending on the appearance of the shear bands developed. It can be found that the fracture energy and fracture toughness of Zr -based BMG are closely related with the extent of shear bands developed during fracture.

Dynamic indentation response of ZrHf-based bulk metallic glasses

2007 ◽  
Vol 22 (2) ◽  
pp. 478-485 ◽  
Author(s):  
Ghatu Subhash ◽  
Hongwen Zhang
Keyword(s):  
Shear Band ◽  
Metallic Glasses ◽  
Amorphous Alloys ◽  
Shear Bands ◽  
Indentation Hardness ◽  
Strain Rates ◽  
Dynamic Indentation ◽  
Confinement Pressure ◽  
Static Indentation ◽  
Deformation Features

Static and dynamic Vickers indentations were performed on ZrHf-based bulk amorphous alloys. A decrease in indentation hardness was observed at higher strain rates compared with static indentation hardness. For equivalent loads, dynamic indentations produced more severe deformation features on the loading surface than static indentations. Using bonded interface technique, the induced shear band patterns beneath the indentations were studied. In static indentations, the majority of the deformation was primarily accommodated by closely spaced semicircular shear bands surrounding the indentation. In dynamic indentations two sets of widely spaced semicircular shear bands with two different curvatures were observed. The observed shear band patterns and softening in hardness were rationalized based on the variations in the confinement pressure, strain rate, and temperature within the indentation region during dynamic indentations. It is also proposed that free volume migration and formation of nano-voids leading to cracking are favored due to adiabatic heating and consequently cause the observed softening at high strain rates.

scholarly journals High-speed X-ray visualization of dynamic crack initiation and propagation in bone

2019 ◽  
Vol 90 ◽  
pp. 278-286 ◽  
Author(s):  
Xuedong Zhai ◽  
Zherui Guo ◽  
Jinling Gao ◽  
Nesredin Kedir ◽  
Yizhou Nie ◽  
...  
Keyword(s):  
Crack Initiation ◽  
High Speed ◽  
Dynamic Crack ◽  
Crack Initiation And Propagation ◽  
X Ray ◽  
Initiation And Propagation

Shear Band Feature in Two Bulk Metallic Glasses with Different Inherent Plasticity

2013 ◽  
Vol 703 ◽  
pp. 20-23
Author(s):  
Jian Sheng Gu ◽  
Hui Feng Bo ◽  
Hong Li ◽  
Zhan Xin Zhang
Keyword(s):  
Plastic Deformation ◽  
Shear Band ◽  
Temperature Rise ◽  
Metallic Glasses ◽  
Shear Banding ◽  
Shear Bands ◽  
Significant Difference ◽  
Coating Method ◽  
Deformation Ability

Shear banding characterization of Zr64.13Cu15.75Ni10.12Al10 and Zr65Cu15Ni10Al10 BMGs was studied by using Rockwell indention method. The significant difference in plastic deformation ability can be ascribed to different shear banding features. Meanwhile, by using the fusible coating method, thermal effect on shear bands was investigated. We did not see apparently temperature rise in shear bands of these two BMGs through Rockwell indentation.

Microfracture Observation of Zr-Based Bulk Metallic Glasses

2007 ◽  
Vol 345-346 ◽  
pp. 645-648
Author(s):  
Jung G. Lee ◽  
Kee Sun Sohn ◽  
Sung Hak Lee ◽  
Nack J. Kim ◽  
Choong Nyun Paul Kim
Keyword(s):  
Shear Band ◽  
Metallic Glasses ◽  
Fracture Resistance ◽  
Shear Bands ◽  
Stable Crack Growth ◽  
Curve Analysis ◽  
Fracture Properties ◽  
Apparent Fracture Toughness ◽  
Crack Blunting

Microfracture mechanisms of Zr-based bulk metallic glass (BMG) alloy containing ductile crystalline particles were investigated by directly observing microfracture processes using an in situ loading stage. Strength of the BMG alloy containing crystalline particles was lower than that of the monolithic BMG alloy, while ductility was higher. According to the direct microfracture observation, crystalline particles initiated shear bands, acted as blocking sites of shear band or crack propagation, and provided the stable crack growth which could be confirmed by the R-curve analysis, although they negatively affected apparent fracture toughness. This increase in fracture resistance with increasing crack length improved overall fracture properties of the alloy containing crystalline particles, and could be explained by mechanisms of blocking of crack or shear band propagation, formation of multiple shear bands, crack blunting, and shear band branching.

DEFORMATION BEHAVIORS OF Zr-BASED BULK METALLIC GLASS UNDER IMPACT INDENTATION

2008 ◽  
Vol 22 (09n11) ◽  
pp. 1775-1782 ◽  
Author(s):  
HYUNG-SEOP SHIN ◽  
SOON-NAM CHANG ◽  
DO KYUNG KIM
Keyword(s):  
Metallic Glasses ◽  
Impact Loading ◽  
Shock Loading ◽  
Shear Bands ◽  
Amorphous Metal ◽  
High Yield ◽  
Spherical Indentation ◽  
Loading Conditions ◽  
Structural Applications ◽  
Deformation Behaviors

Metallic glasses are amorphous meta-stable solids and are now being processed in bulk form suitable for structural applications under impact loading. Bulk metallic glasses have many unique mechanical properties such as high yield strength and fracture toughness, good corrosion and wear resistance that distinguish them from crystalline metals and alloys. However, only a few studies could be found mentioning the dynamic response and damage of metallic glasses under impact or shock loading. In this study, we employed a small explosive detonator for the dynamic indentation to a Zr -based bulk amorphous metal in order to evaluate the damage behavior of bulk amorphous metal under impact or shock loading conditions. Results were compared with those of spherical indentation under quasi-static and impact loading and were discussed. The interface bonded specimen method was adopted in order to observe the subsurface damage, especially the formation of shear bands induced during indentation under different loading conditions.

scholarly journals Dynamic Crack Initiation Toughness of Shale under Impact Loading

Energies ◽  
2019 ◽  
Vol 12 (9) ◽  
pp. 1636
Author(s):  
Guoliang Yang ◽  
Xuguang Li ◽  
Jingjiu Bi ◽  
Shuaijie Cheng
Keyword(s):  
Crack Initiation ◽  
Impact Loading ◽  
Loading Rate ◽  
Split Hopkinson Pressure Bar ◽  
Bedding Plane ◽  
Initiation Toughness ◽  
Dynamic Crack ◽  
Crack Arrester ◽  
Crack Divider ◽  
The Impact

The impact loading of a notched semi-circular bend (NSCB) specimen of outcrop shale in Changning Sichuan was carried out using a split Hopkinson pressure bar (SHPB) to study the effect of shale bedding on the dynamic crack initiation toughness. Three loading configurations were tested: Crack-divider, Crack-splitter and Crack-arrester loading. Bedding plane has a significant effect on the crack initiation of shale. Under the Crack-divider and Crack-splitter modes, shale had lower dynamic crack initiation toughness. The dynamic crack initiation toughness of the shale was affected by the loading rate for all three loading configurations. The correlation between loading rate and dynamic crack initiation toughness was most significant for the Crack-arrester mode, while the Crack-splitter mode was the weakest. When loading was carried out on Crack-arrester, the bedding plane could change the direction of crack growth. In the Crack-splitter mode, only a small impact energy was needed to achieve effective expansion of a crack. The research results provide a theoretical basis for shale cracking.

A Technique for High-Speed Microscopic Imaging of Dynamic Failure Events and Its Application to Shear Band Initiation in Polycarbonate

2021 ◽  
pp. 1-28
Author(s):  
Pinkesh Malhotra ◽  
Sijun Niu ◽  
Vikas Srivastava ◽  
Pradeep R. Guduru
Keyword(s):  
Shear Band ◽  
High Speed ◽  
Computational Simulation ◽  
Constitutive Models ◽  
Deformation Field ◽  
Shear Instability ◽  
Large Field ◽  
Dynamic Failure ◽  
Dominant Band ◽  
Notch Tip

Abstract An experimental technique is reported, which can image the deformation fields associated with dynamic failure events at high spatial and temporal resolutions simultaneously. The technique is demonstrated at a spatial resolution of ~1 μm and a temporal resolution of 250 ns, while maintaining a relatively large field of view (≈ 1.11 mm × 0.63 mm). As a demonstration, the technique is used to image the deformation field near a notch tip during initiation of a shear instability in polycarbonate. An ordered array of 10 μm diameter speckles with 20 μm pitch, and deposited on the specimen surface near the notch tip helps track evolution of the deformation field. Experimental results show that the width of the shear band in polycarbonate is approximately 75 μm near the notch-tip within resolution limits of the experiments. The measurements also reveal formation of two incipient localization bands near the crack tip, one of which subsequently becomes the dominant band while the other is suppressed. Computational simulation of the experiment was conducted using a thermo-mechanically coupled rate-dependent constitutive model of polycarbonate to gain further insight into the experimental observations enabled by the combination of high spatial and temporal resolutions. The simulation results show reasonable agreement with the experimentally observed kinematic field and features near the notch-tip, while also pointing to the need for further refinement of constitutive models that are calibrated at high strain rates (~105/s) and also account for damage evolution.

scholarly journals Dynamic crack arrest capability of some metallic alloys and polymers

2018 ◽  
Vol 183 ◽  
pp. 02002
Author(s):  
Gunasilan Manar ◽  
Norazrina Mat Jali ◽  
Patrice Longère
Keyword(s):  
Impact Velocity ◽  
High Speed ◽  
Shear Failure ◽  
Failure Process ◽  
Shear Bands ◽  
Ductile Failure ◽  
Crack Arrest ◽  
Dynamic Crack ◽  
Impact Tests ◽  
The Impact

We are here interested in the crack arrest capability under impact loading of metals and polymers used as structural and/or protection materials in aerospace engineering. Kalthoff and Winkler-type impact tests are carried out to that purpose on high strength AA7175 aluminum alloy and shock resistant polymethyl methacrylate (PMMA). Impact tests are carried out at impact velocities ranging from 50 m/s to 250 m/s and high speed camera is used to record the different steps of the failure process. For AA7175, early Mode II shear failure followed by late Mode I opening failure are seen. The premature ductile failure of the alloy is shown to result from a preceding stage of dynamic localization in the form of adiabatic shear bands. Impact tests on shock-resistant PMMA evidence the brittle feature of the material failure. It is notably shown that the higher the impact velocity (in the range 50-100 m/s) the larger the number of fragments. Moreover, depending on the impact velocity, changes in the crack path and thus in the mechanisms controlling the PMMA dynamic fracture can be seen.

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