Effect of a Surface Constraining Layer on the Plastic Deformation of Au Microspheres

MRS Advances ◽  
2018 ◽  
Vol 3 (8-9) ◽  
pp. 427-432
Author(s):  
AZM Ariful Islam ◽  
Robert J. Klassen
Keyword(s):  
Plastic Deformation ◽  
Small Volume ◽  
Dislocation Nucleation ◽  
Surface Layers ◽  
Loading Rates ◽  
Plastic Deformation Process ◽  
Sputter Deposited ◽  
Yield Force ◽  
Mechanisms Of Plastic Deformation

ABSTRACTSingle crystal Au microspheres, of 3 μm diameter, with sputter-deposited Ni surface layers, of 40 or 80 nm thickness, were tested in compression at three loading rates to investigate the role of thin passive layers on the mechanisms of plastic deformation of small-volume FCC ductile metal samples. The Ni layer resulted in an increase in the incipient yield force by about 10%. Micro-cracking of the Ni layer was observed to occur with incipient yielding. The estimated apparent activation volume of the incipient plastic deformation process was found to be nearly identical for the Ni-coated and the uncoated Au microspheres. This suggests that, while the stress required to initiate incipient plastic deformation was increased by the constraint imposed by the Ni layer, the subsequent plastic flow occurred by a dislocation nucleation and glide mechanism that is essentially the same as that occurring in an unconstrained Au microsphere.

Defect Structure Parameters of Deformed Polycrystals on Micro- and Mesolevel of Grain Sizes

2014 ◽  
Vol 1013 ◽  
pp. 1-6
Author(s):  
Eduard Kozlov ◽  
Natal'ya Popova ◽  
Marina Fedorischeva ◽  
Nina Koneva
Keyword(s):  
Plastic Deformation ◽  
Size Effect ◽  
Defect Structure ◽  
Structure Parameters ◽  
Scalar Density ◽  
Grain Sizes ◽  
Different Types ◽  
Closed Structure ◽  
Mechanisms Of Plastic Deformation

In the paper we consider the size effect of the closed structural formations as the function of accumulation of scalar density dislocations and their components under plastic deformation. The focus is on the role of interfaces of different types. The sizes are determined and the various parameters of the structure defining the micro-and mesolevel are identified at the development of the mechanisms of plastic deformation. The role of statistically stored dislocations (SSD) and geometrically necessary dislocations (GND) in the formation of the defect structure of the material is examined. It has been established that the smaller the size of the closed structure, the greater the GND part and the smaller the SSD component. The work is based on the TEM research of the structure of deformed materials.

scholarly journals Justification of the effect of transitional modes on the quality of ready-made products when their treatment is used by plastic deformation methods from the position of the wave and auto vibration processes

2019 ◽  
pp. 6-16
Author(s):  
A. D. Uchitel ◽  
Yu. A. Malinovskyi ◽  
A. N. Panchenko ◽  
G. V. Danilina ◽  
S. Yu. Datsenko
Keyword(s):  
Plastic Deformation ◽  
Metal Forming ◽  
Dynamic Instability ◽  
Longitudinal Force ◽  
Elastic Base ◽  
Surface Layers ◽  
Tangential Forces ◽  
Definition Of

Purpose. Substantiation of the role of longitudinal and transverse wave processes in the surface layers on the quality of finished products obtained by plastic deformation methods, such as cold rolling, stamping, running in, drawing and others. Research methodology. In the work, to describe the transients at the beginning of the interaction of the tool with the workpiece, a computational model was applied in which the surface layers of the workpiece are represented as a beam on an elastic base, loaded with suddenly applied tangential forces, often exceeding their critical values. The reasons for the occurrence of unstable dynamic states of such a beam, in which the integrity of the surface layers of the workpiece and parts may be disturbed due to the occurrence of supercritical stresses and deformation in the material of the outer layers, are investigated. Findings. The results were obtained on the definition of hazardous states of the surface layers of the workpiece, under the action of suddenly applied loads at the initial moments of the capture of the workpiece, as well as at the moments when the tool slips over the workpiece during the alignment of their speeds. Originality. It consists in the fact that the first dynamic problem was set and solved for the surface layers of the workpiece, represented as a two-support beam on an elastic base loaded with a suddenly applied longitudinal force, which can significantly exceed its critical value. Denoted areas of dynamic instability of the surface layers of the workpiece. The practical value of the work lies in the fact that the modes of operation of the metal forming machine and the parameters of the workpiece were identified under which conditions for obtaining products of insufficient quality may arise. As well as developed recommendations for improving the quality of finished products. Key words: metal forming, transients, longitudinal wave, shear wave, billet, loaded layer, overload coefficient, dynamic buckling, tool, rolling, knurling, drawing, hypothetical beam, impact, elastic wave propagation velocity.

Tunable optoelectronic properties of radio frequency sputter-deposited Sb2Se3 thin films: Role of growth angle and thickness

Solar Energy ◽  
2019 ◽  
Vol 194 ◽  
pp. 716-723
Author(s):  
Alapan Dutta ◽  
Ranveer Singh ◽  
Sanjeev Kumar Srivastava ◽  
Tapobrata Som
Keyword(s):  
Thin Films ◽  
Radio Frequency ◽  
Optoelectronic Properties ◽  
Growth Angle ◽  
Sputter Deposited

Myocardial CO2 buffering: role of transmembrane transport of H+ or HCO3-ions

1976 ◽  
Vol 230 (4) ◽  
pp. 1037-1041 ◽  
Author(s):  
DR Strome ◽  
RL Clancy ◽  
NC Gonzalez
Keyword(s):  
Small Volume ◽  
Coronary Circulation ◽  
Myocardial Cell ◽  
Ringer Solution ◽  
Red Cells ◽  
Transmembrane Transport ◽  
High Degree

Isolated rabbit hearts were perfused with rabbit red cells suspended in Ringer solution. A small volume of perfusate was recirculated for 10 min at Pco2 of 33.4 +/- 0.9 or 150.8 +/- 7.5 mmHg. Hypercapnia resulted in an increase in perfusate HCO3- concentration that was smaller than that observed when isolated perfusate was equilibrated in vitro with the same CO2 tensions (delta HCO-3e = 1.6 mM, P less than 0.01). This difference is consistent with a net movement of HCO3- into or H+ out of the mycardial cell, and cannot be accounted for by dilution of HCO3- in the myocardial interstitium. Recirculation of perfusate through the coronary circulation at normal Pco2 for two consecutive 10-min periods was not followed by changes in perfusate HCO3- concentration. A high degree of correlation (r = 0.81) was observed between intracellular HCO-3e concentration and the corresponding delta HCO-3e in individual experiments. The results suggest that transmembrane exchange of H+ or HCO3- is a buffer mechanism for CO2 in the myocardial cell.

scholarly journals A Dislocation-Based Theory for the Deformation Hardening Behavior of DP Steels: Impact of Martensite Content and Ferrite Grain Size

2010 ◽  
Vol 2010 ◽  
pp. 1-16 ◽  
Author(s):  
Yngve Bergström ◽  
Ylva Granbom ◽  
Dirk Sterkenburg
Keyword(s):  
Plastic Deformation ◽  
Grain Size ◽  
Deformation Process ◽  
Volume Fraction ◽  
High Energy ◽  
Martensite Content ◽  
Plastic Deformation Process ◽  
Deformation Hardening ◽  
Dp Steels ◽  
Ferrite Grain Size

A dislocation model, accurately describing the uniaxial plastic stress-strain behavior of dual phase (DP) steels, is proposed and the impact of martensite content and ferrite grain size in four commercially produced DP steels is analyzed. It is assumed that the plastic deformation process is localized to the ferrite. This is taken into account by introducing a nonhomogeneity parameter, f(ε), that specifies the volume fraction of ferrite taking active part in the plastic deformation process. It is found that the larger the martensite content the smaller the initial volume fraction of active ferrite which yields a higher initial deformation hardening rate. This explains the high energy absorbing capacity of DP steels with high volume fractions of martensite. Further, the effect of ferrite grain size strengthening in DP steels is important. The flow stress grain size sensitivity for DP steels is observed to be 7 times larger than that for single phase ferrite.

Reverse Plasticity in Nanoindentation

2007 ◽  
Vol 1049 ◽  
Author(s):  
Yongjiang Huang ◽  
Nursiani Indah Tjahyono ◽  
Jun Shen ◽  
Yu Lung Chiu
Keyword(s):  
Mechanical Properties ◽  
Plastic Deformation ◽  
Glass Transition ◽  
Single Crystal ◽  
Metallic Glasses ◽  
Deformation Mechanisms ◽  
Glass Transition Temperatures ◽  
Loading Rates ◽  
Nanoindentation Experiment ◽  
Properties Of Materials

AbstractThis paper summarises our recent cyclic nanoindentation experiment studies on a range of materials including single crystal and nanocrystalline copper, single crystal aluminium and bulk metallic glasses with different glass transition temperatures. The unloading and reloading processes of the nanoindentation curves have been analysed. The reverse plasticity will be discussed in the context of plastic deformation mechanisms involved. The effect of loading rates on the mechanical properties of materials upon cyclic loading will also be discussed.

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