The role of shear stresses and shear strains in transformation-toughening

1991 ◽  
Vol 64 (4) ◽  
pp. 879-902 ◽  
Author(s):  
David M. Stump
Keyword(s):  
Shear Stresses ◽  
Transformation Toughening ◽  
Shear Strains

Role of Ce2Zr3O10 Phase on the Microstructure and Fracture Toughness of ZTA Composites

2016 ◽  
Vol 840 ◽  
pp. 57-60 ◽  
Author(s):  
Nik Akmar Rejab ◽  
Zhwan Dilshad Ibrahim Sktani ◽  
Afifah Mohd Ali ◽  
Zainal Arifin Ahmad
Keyword(s):  
Fracture Toughness ◽  
Experimental Results ◽  
Mixing Process ◽  
Transformation Toughening ◽  
Simple Route ◽  
Zirconia Toughened Alumina

Despite the impressive development in understanding transformation toughening, tailoring the toughness of zirconia toughened alumina (ZTA) ceramics remained a major challenge. In our research, a simple route based on the powders mixing process of ZTA powders with varying CeO2 additions (0 - 10 wt.%) is developed to investigate this issue. The experimental results clearly reveal that the fracture toughness of ZTA ceramics can be tailored by mixing of ZTA starting powders.

Structural transformations and improved ductility in ordered FeCo and ZrCo intermetallics

2006 ◽  
Vol 980 ◽  
Author(s):  
Maja Krcmar ◽  
Chong Long Fu ◽  
James R. Morris
Keyword(s):  
Phase Transformation ◽  
Structural Transformation ◽  
First Principles ◽  
Structural Phase ◽  
High Stress ◽  
Energy Structure ◽  
Shear Stresses ◽  
First Principles Calculations ◽  
Transformation Toughening ◽  
Feco Alloys

AbstractUsing the first-principles calculations, we find that Fe-Co has a tendency for a structural transformation to a lower symmetry sheared L10 phase under the applied shear stresses. This tendency for structural transformation can have a significant influence on the mechanical properties of FeCo, as it might be closely connected with the intrinsic brittleness of Fe-rich and stoichiometric FeCo alloys and with the improved ductility of Co-rich FeCo alloys. We suggest that improved ductility in Co-rich FeCo alloys may originate from transformation toughening due to the B2→L10 structural transformation near the regions of high stress concentration, as the stress energy is fully dissipated by the decrease in the electronic energy due to the structural phase transformation into a lower energy structure. Similarly, in ZrCo, our first-principles calculations find that a B2→B33 martensitic phase transformation can occur under the applied shear stress, which may contribute to the good ductility of this alloy, despite the fact that ZrCo is a strongly ordered line compound.

scholarly journals Cyclic and Permanent Shear Strains of a Soft Cohesive Soil Subjected to Combined Static and Cyclic Loading

2020 ◽  
Vol 10 (23) ◽  
pp. 8433
Author(s):  
Hernán Patiño ◽  
Rubén Galindo ◽  
Claudio Olalla Marañón
Keyword(s):  
Simple Shear ◽  
Cohesive Soil ◽  
Mediterranean Coast ◽  
Vertical Stress ◽  
Experimental Program ◽  
Shear Stresses ◽  
Shear Tests ◽  
Cyclic Shear ◽  
Shear Strains ◽  
Number Of Cycles

This paper refers to cyclic shear strains (γc) and permanent shear strains (γp) of a soft cohesive soil, when both monotonic shear stresses (τo) and cyclic shear stresses (τc) are applied. The research is backed by an extensive experimental program with 139 cyclic simple shear tests that included identification and classification tests. These cyclic simple shear tests were conducted under different levels of stresses, τo, before the cyclic phase. Laboratory tests were carried out on undisturbed samples from the Port of Barcelona, located in Spain on the Mediterranean coast, and characterized by a monotonic strength (τmax) approximately equal to 30% of the initial effective vertical stress (σ′ov). The samples were taken at depths between 29 and 52 m and correspond to an initial effective vertical stress between 277 and 413 kPa, respectively. In general, the results indicate that: (a) the combination of τo and τc controls the generation of γc and γp, (b) it is not always true that when τo/σ′ov + τc/σ′ov ≈ τmax/σ′ov, the soil reaches failure cyclically, and (c) empirical relations useful for design can be established between γc, γp, and the number of cycles (N), for different relationships varying (τo/σ′ov) between 0% and 25%.

Stiffness of the pleural surface of the chest wall is similar to that of the lung

2003 ◽  
Vol 95 (6) ◽  
pp. 2345-2349 ◽  
Author(s):  
Andrew Gouldstone ◽  
Richard E. Brown ◽  
James P. Butler ◽  
Stephen H. Loring
Keyword(s):  
Chest Wall ◽  
Elastohydrodynamic Lubrication ◽  
Geometric Standard Deviation ◽  
Parietal Pleura ◽  
Shear Stresses ◽  
Membrane Tension ◽  
Similar Extent ◽  
Spatial Uniformity ◽  
Pleural Surface

To address the role of the parietal pleura in reduction of mesothelial shear stresses during breathing, we measured the stiffness of the parietal pleural surface of mammalian chest walls using microindentation. The pleural surface was indented over ribs and intercostal spaces with rigid flat punches (tip radii of 0.01, 0.02, and 0.1 cm) to probe stiffness at length scales comparable with those of surface asperities. We found a tissue shear modulus of 6,700 dyn/cm2 and pleural membrane tension of 4,900 dyn/cm, with a geometric standard deviation of 0.42. These values are similar to those measured for the lung by Hajji et al., using indentation (Hajji MA, Wilson TA, and Lai-Fook SJ. J Appl Physiol Respirat Environ Exerc Physiol 47: 175–181, 1979). Surprisingly, the pleural surface over ribs and intercostal spaces exhibited similar stiffness. In addition, caudal regions exhibited lower stiffness than cranial regions. In the context of elastohydrodynamic lubrication, these results suggest that shear-induced pressures during breathing deform the chest wall and lung surfaces to a similar extent, promoting spatial uniformity of pleural fluid thickness and reducing shear stresses.

scholarly journals A dynamical model of a crystal structure. III

1949 ◽  
Vol 196 (1045) ◽  
pp. 182-194 ◽  
Keyword(s):  
Repulsive Interaction ◽  
Shear Stresses ◽  
Displacement Curve ◽  
Plastic Yielding ◽  
Maximum Shear Strain ◽  
Perfect Lattice ◽  
Interaction Terms ◽  
Shear Strains ◽  
Sine Law ◽  
Small Shear

A calculation of the maximum shear strain under which a two-dimensional close-packed lattice is stable has been carried out in terms of the forces between the lattice components. Two types of force were used; those between floating bubbles, which enabled a comparison with experiments on actual rafts of bubbles to be made, and also the forces derived from a potential V = Ae β r 2 , which form has been frequently proposed as an approximation to the repulsive interaction terms between metal ions. The conclusion reached is that this maximum strain may be considerably less than that deduced from a simple sine law approximation to the shear force versus displacement curve. Detailed consideration is given to edge effects in bubble rafts, and reasonable agreement with experimental results obtained. The overall result is that the formation of dislocations and consequent plastic yielding can occur in an initially perfect lattice only at quite large shear strains. The analogy with metals is discussed, and we conclude that the low strengths of metallic single crystals are explicable only on the assumption that they are not perfect and that dislocations already exist in them and move under very small shear stresses.

Recent developments in modeling ice sheet deformation

2020 ◽  
Author(s):  
Felicity McCormack ◽  
Roland Warner ◽  
Adam Treverrow ◽  
Helene Seroussi
Keyword(s):  
Ice Sheets ◽  
Ice Sheet ◽  
Vertical Shear ◽  
Shear Stresses ◽  
Polar Ice ◽  
Ice Flow ◽  
Polar Ice Sheets ◽  
Basal Shear ◽  
The Impact

<p>Viscous deformation is the main process controlling ice flow in ice shelves and in slow-moving regions of polar ice sheets where ice is frozen to the bed. However, the role of deformation in flow in ice streams and fast-flowing regions is typically poorly represented in ice sheet models due to a major limitation in the current standard flow relation used in most large-scale ice sheet models – the Glen flow relation – which does not capture the steady-state flow of anisotropic ice that prevails in polar ice sheets. Here, we highlight recent advances in modeling deformation in the Ice Sheet System Model using the ESTAR (empirical, scalar, tertiary, anisotropic regime) flow relation – a new description of deformation that takes into account the impact of different types of stresses on the deformation rate. We contrast the influence of the ESTAR and Glen flow relations on the role of deformation in the dynamics of Thwaites Glacier, West Antarctica, using diagnostic simulations. We find key differences in: (1) the slow-flowing interior of the catchment where the unenhanced Glen flow relation simulates unphysical basal sliding; (2) over the floating Thwaites Glacier Tongue where the ESTAR flow relation outperforms the Glen flow relation in accounting for tertiary creep and the spatial differences in deformation rates inherent to ice anisotropy; and (3) in the grounded region within 80km of the grounding line where the ESTAR flow relation locally predicts up to three times more vertical shear deformation than the unenhanced Glen flow relation, from a combination of enhanced vertical shear flow and differences in the distribution of basal shear stresses. More broadly on grounded ice, the membrane stresses are found to play a key role in the patterns in basal shear stresses and the balance between basal shear stresses and gravitational forces simulated by each of the ESTAR and Glen flow relations. Our results have implications for the suitability of ice flow relations used to constrain uncertainty in reconstructions and projections of global sea levels, warranting further investigation into using the ESTAR flow relation in transient simulations of glacier and ice sheet dynamics. We conclude by discussing how geophysical data might be used to provide insight into the relationship between ice flow processes as captured by the ESTAR flow relation and ice fabric anisotropy.</p>

New Interpretation of the Influence of Various Parameters on Texture Evolution in Damascene Cu Interconnect Lines

2005 ◽  
Vol 495-497 ◽  
pp. 1449-1454 ◽  
Author(s):  
Kabir Kumar Mirpuri ◽  
Jerzy A. Szpunar
Keyword(s):  
Dislocation Density ◽  
Texture Evolution ◽  
Shear Stresses ◽  
Principal Stresses ◽  
Line Spacing ◽  
Role Of Principal ◽  
New Interpretation ◽  
Cu Interconnect ◽  
Interconnect Lines

The article takes into account various factors which effect the texture evolution in the Cu lines. We propose here an explanation for the formation of {111}<110> and {111}<112> texture in the Cu lines. The explicit role of principal stresses, shear stresses and dislocations is discussed. The influence of line spacing on strength of the {111}<110> and {111}<112> texture components is also demonstrated in relation to the dislocation density.

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