Dynamic Constitutive and Failure Behavior of a Two-Phase Tungsten Composite

1997 ◽  
Vol 64 (3) ◽  
pp. 487-494 ◽  
Author(s):  
M. Zhou ◽  
R. J. Clifton
Keyword(s):  
Shear Band ◽  
Shear Bands ◽  
Kolsky Bar ◽  
High Rate ◽  
Failure Behavior ◽  
Localized Deformation ◽  
Two Phase ◽  
The Matrix ◽  
Torsional Kolsky Bar ◽  
The Impact

The constitutive response and failure behavior of a W-Ni-Fe alloy over the strain rate range of 10-4 to 5 X 105 s-1 is experimentally investigated. Experiments conducted are pressure-shear plate impact, torsional Kolsky bar, and quasi-static torsion. The material has a microstructure of hard tungsten grains embedded in a soft alloy matrix. Nominal shear stress-strain relations are obtained for deformations throughout the experiments and until after the initiation of localization. Shear bands form when the plastic strain becomes sufficiently large, involving both the grains and the matrix. The critical shear strain for shear band development under the high rate, high pressure conditions of pressure-shear is approximately 1–1.5 or 6–8 times that obtained in torsional Kolsky bar experiments which involve lower strain rates and zero pressure. Shear bands observed in the impact experiments show significantly more intensely localized deformation. Eventual failure through the shear band is a combination of grain-matrix separation, ductile matrix rupture, and grain fracture. In order to understand the effect of the composite microstructure and material inhomogeneity on deformation, two other materials are also used in the study. One is a pure tungsten and the other is an alloy of W, Ni, and Fe with the same composition as that of the matrix phase in the overall composite. The results show that the overall two-phase composite is more susceptible to the formation of shear bands than either of its constituents.

scholarly journals An Insight into Amorphous Shear Band in Magnetorheological Solid by Atomic Force Microscope

Materials ◽  
2021 ◽  
Vol 14 (16) ◽  
pp. 4384
Author(s):  
Mohd Aidy Faizal Johari ◽  
Asmawan Mohd Sarman ◽  
Saiful Amri Mazlan ◽  
Ubaidillah U ◽  
Nur Azmah Nordin ◽  
...  
Keyword(s):  
Stress Relaxation ◽  
Shear Band ◽  
Shear Bands ◽  
Test Duration ◽  
Phase Imaging ◽  
Force Microscopy ◽  
Atomic Force ◽  
The Matrix ◽  
Relaxation Stress ◽  
Band Deformation

Micro mechanism consideration is critical for gaining a thorough understanding of amorphous shear band behavior in magnetorheological (MR) solids, particularly those with viscoelastic matrices. Heretofore, the characteristics of shear bands in terms of formation, physical evolution, and response to stress distribution at the localized region have gone largely unnoticed and unexplored. Notwithstanding these limitations, atomic force microscopy (AFM) has been used to explore the nature of shear band deformation in MR materials during stress relaxation. Stress relaxation at a constant low strain of 0.01% and an oscillatory shear of defined test duration played a major role in the creation of the shear band. In this analysis, the localized area of the study defined shear bands as varying in size and dominantly deformed in the matrix with no evidence of inhibition by embedded carbonyl iron particles (CIPs). The association between the shear band and the adjacent zone was further studied using in-phase imaging of AFM tapping mode and demonstrated the presence of localized affected zone around the shear band. Taken together, the results provide important insights into the proposed shear band deformation zone (SBDZ). This study sheds a contemporary light on the contentious issue of amorphous shear band deformation behavior and makes several contributions to the current literature.

scholarly journals Shear Band Characterization of Clayey Soils with Particle Image Velocimetry

2020 ◽  
Vol 10 (3) ◽  
pp. 1139
Author(s):  
Kwak ◽  
Park ◽  
Kim ◽  
Chung ◽  
Baek
Keyword(s):  
Particle Image Velocimetry ◽  
Spatial Distribution ◽  
Shear Band ◽  
Particle Image ◽  
Shear Bands ◽  
Side Wall ◽  
Failure Behavior ◽  
Clayey Soils ◽  
Initial State ◽  
Image Velocimetry

Identifying the spatial distribution of deformation and shear band characteristics is important for accurately modeling soil behavior and ensuring the safety of nearby geotechnical structures. However, most research on the shear behavior of soils has focused on granular soil and clay-rich rocks, with little focus on clayey soil, and the entire shearing process from the initial state to failure has not been observed. This study evaluated the spatial distribution and evolution of deformation in clayey soils from the initial state to the post-failure state and the shear band characteristics. Plane strain tests were performed on normally consolidated and over-consolidated clay specimens, and digital images were captured through a transparent side wall for particle image velocimetry (PIV) analysis. PIV was performed to evaluate the displacement and deformation of soil particles. The results show that the shear-strain behaviors of two clays during the shearing process could be divided into four stages: initial, peak, softening, and steady state. Shear bands were observed to form in the softening stage, and the shear band slopes were compared to values in the literature. These results can be used to characterize shear bands in clay as well as predict failure behavior and guide reinforcement at actual sites with soft ground.

scholarly journals On Adequacy of Two-point Averaging Schemes for Composites with Nonlinear Viscoelastic Phases

10.14311/658 ◽  
2004 ◽  
Vol 44 (5-6) ◽  
Author(s):  
J. Zeman ◽  
R. Valenta ◽  
M. Šejnoha
Keyword(s):  
Finite Element ◽  
Shear Bands ◽  
Material Model ◽  
Finite Element Simulations ◽  
Composite Medium ◽  
Viscoelastic Response ◽  
Two Phase ◽  
Nonlinear Viscoelastic ◽  
The Matrix ◽  
Macroscopic Response

Finite element simulations on fibrous composites with nonlinear viscoelastic response of the matrix phase are performed to explain why so called two-point averaging schemes may fail to deliver a realistic macroscopic response. Nevertheless, the potential of two-point averaging schemes (the overall response estimated in terms of localized averages of a two-phase composite medium) has been put forward in number of studies either in its original format or modified to overcome the inherited stiffness of classical ”elastic” localization rules. However, when the material model and geometry of the microstructure promote the formation of shear bands, none of the existing two-point averaging schemes will provide an adequate macroscopic response, since they all fail to capture the above phenomenon. Several examples are presented here to support this statement. 

FORMATION FEATURES OF ADIABATIC SHEAR BANDS DURING HOT COMPRESSION OF VTI-4 ALLOY AND SUBSEQUENT ANNEALING

2020 ◽  
pp. 14-22
Author(s):  
A.V. Zavodov ◽  
◽  
P.N. Medvedev ◽  
N.A. Nochovnaya ◽  
◽  
...  
Keyword(s):  
Shear Bands ◽  
Central Zone ◽  
Orthorhombic Phase ◽  
Hot Compression ◽  
High Rate ◽  
Recrystallization Annealing ◽  
Adiabatic Shear Bands ◽  
Deformation Bands ◽  
Localized Deformation ◽  
Compression Texture

Textural and macrostructural changes in the intermetallic titanium alloy VTI-4 based on the orthorhombic phase (Ti2AlNb) during hot high-rate compression and subsequent recrystallization annealing where studied. The main attention is paid to the formation features of localized deformation bands (LDB) in the central zone of the compressed sample, which are one of the signs of unstable and nonuniform deformation. It is shown that recrystallization annealing after hot compression does not eliminate the LDB and the compression texture. Reasons for this behavior of the material are studied applying the analysis of the solid solution state.

Formation of Deformation Twins and Related Shear Bands in Copper Single Crystals Pressed by ECAP

2010 ◽  
Vol 654-656 ◽  
pp. 1231-1234
Author(s):  
Takumi Ikeda ◽  
Hiroyuki Miyamoto ◽  
Toshiyuki Uenoya ◽  
Satoshi Hashimoto ◽  
Alexei Vinogradov
Keyword(s):  
Shear Band ◽  
Grain Boundaries ◽  
Single Crystals ◽  
Pure Copper ◽  
Shear Bands ◽  
Large Angle ◽  
Deformation Twins ◽  
Crystallographic Feature ◽  
The Matrix ◽  
Copper Single Crystals

The pure copper single crystals with specific crystallographic orientated were subjected to ECAP for one pass at room temperature. Two types of shear bands were observed. Type 1 shear bands were constructed with clusters of distorting micro shear bands and matrix. Micro shear band and matrix were delineated by large-angle grain boundaries, and these two orientations are in a twinning relationship. Parallel sets of deformation twins were observed in the matrix. Type 2 shear bands had no crystallographic feature, and shear band and matrix were considered as low-angle grain boundaries. Deformation twin was not observed both in matrix and the shear bands.

Failure Susceptibility in Thin Films with Extensive Incompatibility in Thermo-Elastic Material Properties

2015 ◽  
Vol 665 ◽  
pp. 225-228
Author(s):  
Igor Dobovšek
Keyword(s):  
Elastic Material ◽  
Material Properties ◽  
Flexible Substrate ◽  
Volume Element ◽  
Failure Behavior ◽  
Phase System ◽  
Spatial Averaging ◽  
Two Phase ◽  
External Temperature ◽  
The Impact

We discuss the impact of residual stresses, caused by variation in external temperature fielddue to mismatch in thermal and elastic material properties in dissimilar two-phase system composedof a thin film and a flexible substrate, on failure behavior of the system. In the process of modeling, arepresentative volume element of the system is defined as a heterogeneous two-phase layered elementbonded at an interface in a sense of coherent bi-layer with classical interface conditions, which canbe described as a sharp interface. We use a spatial averaging technique in transversal direction ofthe element with particular form of strain field that satisfies compatibility equations in the bulk andat the interface. With developed methodology we are able to determine residual stress distributionthrough thickness of the representative volume element. With known distribution of the stress field,we formulate a corresponding failure criterion in the form of characteristic failure surfaces.

Transition alpha structure in beta-isomorphous Nb-Hf alloys

1987 ◽  
Vol 45 ◽  
pp. 232-233
Author(s):  
R.W. Carpenter ◽  
Changhai Li ◽  
David J. Smith
Keyword(s):  
Solid Solution ◽  
Solution Phase ◽  
Miscibility Gap ◽  
Large Strains ◽  
Solid Solution Phase ◽  
Two Phase ◽  
Diffuse Intensity ◽  
Metastable Form ◽  
The Matrix ◽  
Equilibrium Morphology

Binary Nb-Hf alloys exhibit a wide bcc solid solution phase field at temperatures above the Hfα→ß transition (2023K) and a two phase bcc+hcp field at lower temperatures. The β solvus exhibits a small slope above about 1500K, suggesting the possible existence of a miscibility gap. An earlier investigation showed that two morphological forms of precipitate occur during the bcc→hcp transformation. The equilibrium morphology is rod-type with axes along <113> bcc. The crystallographic habit of the rod precipitate follows the Burgers relations: {110}||{0001}, <112> || <1010>. The earlier metastable form, transition α, occurs as thin discs with {100} habit. The {100} discs induce large strains in the matrix. Selected area diffraction examination of regions ∼2 microns in diameter containing many disc precipitates showed that, a diffuse intensity distribution whose symmetry resembled the distribution of equilibrium α Bragg spots was associated with the disc precipitate.

Using crystallographic symmetry in diffraction and contrast analysis

1989 ◽  
Vol 47 ◽  
pp. 504-505
Author(s):  
U. Dahmen ◽  
K.H. Westmacott
Keyword(s):  
Electron Microscopy ◽  
High Symmetry ◽  
Two Phase ◽  
Tem Analysis ◽  
Crystallographic Symmetry ◽  
The Matrix ◽  
Contrast Analysis ◽  
Practical Tool ◽  
Convergent Beam ◽  
Beam Diffraction

Despite the increased use of convergent beam diffraction, symmetry concepts in their more general form are not commonly applied as a practical tool in electron microscopy. Crystal symmetry provides an abundance of information that can be used to facilitate and improve the TEM analysis of crystalline solids. This paper draws attention to some aspects of symmetry that can be put to practical use in the analysis of structures and morphologies of two-phase materials.It has been shown that the symmetry of the matrix that relates different variants of a precipitate can be used to determine the axis of needle- or lath-shaped precipitates or the habit plane of plate-shaped precipitates. By tilting to a special high symmetry orientation of the matrix and by measuring angles between symmetry-related variants of the precipitate it is possible to find their habit from a single micrograph.

Impact Strength, Flexural Modulus and Wear Rate of PMMA Composites Reinforced by Eggshell Powders

2020 ◽  
Vol 38 (7A) ◽  
pp. 960-966
Author(s):  
Aseel M. Abdullah ◽  
Hussein Jaber ◽  
Hanaa A. Al-Kaisy
Keyword(s):  
Impact Strength ◽  
Wear Rate ◽  
Flexural Modulus ◽  
Matrix Material ◽  
Weight Fraction ◽  
Pure Pmma ◽  
Calcination Process ◽  
The Matrix ◽  
The Impact ◽  
Interface Bond

In the present study, the impact strength, flexural modulus, and wear rate of poly methyl methacrylate (PMMA) with eggshell powder (ESP) composites have been investigated. The PMMA used as a matrix material reinforced with ESP at two different states (including untreated eggshell powder (UTESP) and treated eggshell powder (TESP)). Both UTESP and TESP were mixed with PMMA at different weight fractions ranged from (1-5) wt.%. The results revealed that the mechanical properties of the PMMA/ESP composites were enhanced steadily with increasing eggshell contents. The samples with 5 wt.% of UTESP and TESP additions give the maximum values of impact strength, about twice the value of the pure PMMA sample. The calcination process of eggshells powders gives better properties of the PMMA samples compared with the UTESP at the same weight fraction due to improvements in the interface bond between the matrix and particles. The wear characteristics of the PMMA composites decrease by about 57% with increases the weight fraction of TESP up to 5 wt.%. The flexural modulus values are slightly enhanced by increasing of the ESP contents in the PMMA composites.

Others' participation rate influences an individual's charitable behavior: Others' similarity as a moderator

2017 ◽  
Vol 45 (10) ◽  
pp. 1607-1618 ◽  
Author(s):  
Seung Yun Lee ◽  
Sunho Jung ◽  
Sangdo Oh ◽  
Seong Hoon Park
Keyword(s):  
Undergraduate Students ◽  
Participation Rate ◽  
High Rate ◽  
Charitable Behavior ◽  
High Participation ◽  
Negative Effect ◽  
The Impact ◽  
And Diffusion ◽  
High Participation Rate ◽  
Diffusion Of Responsibility

We proposed that a moderator, others' similarity, would determine the impact of high participation rates of others on an individual's charitable behavior, and aimed to show that this moderator would work through the diffusion of responsibility motive. Participants (N = 152 undergraduate students) completed measures of charitable behavior and diffusion of responsibility, after being assigned to 1 of 2 conditions where a set percentage of other students (manipulated as either similar undergraduate students or dissimilar graduate students) were stated to have already donated to a charitable campaign (high contribution condition = 70% participation, low contribution condition = 30% participation). Our results showed that the high participation rate of others increased an individual's charitable behavior when the others in question were similar to that individual, but not when the others were dissimilar. In addition, the high rate of participation by others increased the diffusion of responsibility motive when the others in question were dissimilar to that individual, leading to a negative effect on that individual's charitable behavior.

Sign in / Sign up

Export Citation Format

Share Document