The Role of Rate Effects and of Thermomechanical Coupling in Shear Localization

1997 ◽  
Vol 119 (4) ◽  
pp. 322-331 ◽  
Author(s):  
Y. Estrin ◽  
A. Molinari ◽  
S. Mercier
Keyword(s):  
Numerical Simulations ◽  
Strain Localization ◽  
Mechanical Energy ◽  
Shear Banding ◽  
Rate Sensitivity ◽  
Thermomechanical Coupling ◽  
Face Centered Cubic ◽  
Adiabatic Shear Banding ◽  
Thin Walled Tube ◽  
Face Centered

A dislocation density related constitutive model that accounts for the strain-rate sensitivity of the flow stress and, notable, of the strain-hardening coefficient was applied to describe adiabatic shear banding in face centered cubic metals. The parameter values of a prototype material, for which numerical simulations were carried out, are close to those of copper. The effect of the material parameters, especially of those reflecting the two rate sensitivities, on the occurrence of strain localization in a thin-walled tube under torsion containing a geometrical defect was investigated systematically. The results obtained provide some guidance with respect to design of materials with high resistance to strain localization and high mechanical energy absorption. Another outcome of this study is the recognition that for the problem in question linear stability analysis cannot provide a reliable criterion even for the onset of strain localization, and that numerical simulations have to be invoked.

Orientation dependence of shear banding in face-centered-cubic single crystals

2012 ◽  
Vol 60 (8) ◽  
pp. 3415-3434 ◽  
Author(s):  
N. Jia ◽  
P. Eisenlohr ◽  
F. Roters ◽  
D. Raabe ◽  
X. Zhao
Keyword(s):  
Single Crystals ◽  
Shear Banding ◽  
Orientation Dependence ◽  
Face Centered Cubic ◽  
Face Centered

A Large Deformation Plasticity Model With Rate Sensitivity and Thermal Softening

1984 ◽  
Vol 106 (4) ◽  
pp. 388-392
Author(s):  
D. W. Nicholson ◽  
K. C. Kiddy
Keyword(s):  
Large Deformation ◽  
Shear Banding ◽  
Small Deformation ◽  
Rate Sensitivity ◽  
Thermal Softening ◽  
Dynamic Loads ◽  
Extended Model ◽  
Adiabatic Shear Banding ◽  
Deformation Plasticity ◽  
Applied Stresses

In this paper, a previously published small deformation constitutive model with rate sensitive plasticity and thermal softening is extended to large deformation. The extended model appears suitable for describing a deleterious thermoplastic process manifested by adiabatic shear banding in materials such as titanium under severe dynamic loads. The nature of the instability admitted by the model is described. Also, calculations are reported on the rapid extension of a titanium strip. For applied stresses several times the yield stress, a deleterious temperature is attained in times of the order of 10−2 s.

scholarly journals Recreating Ductility-Dip Cracking via Gleeble®-Based Welding Simulation

2021 ◽  
Vol 100 (01) ◽  
pp. 27-39
Author(s):  
SAMUEL LUTHER ◽  
◽  
BOIAN ALEXANDROV
Keyword(s):  
Elevated Temperature ◽  
Nuclear Power ◽  
Large Scale ◽  
Mechanical Energy ◽  
Austenitic Stainless Steels ◽  
Face Centered Cubic ◽  
Experimental Procedure ◽  
Thermomechanical Cycling ◽  
310 Stainless Steel ◽  
Face Centered

Face-centered cubic alloys, such as nickel-based alloys and austenitic stainless steels, are important to many industries, notably nuclear power generation and petrochemical. These alloys are prone to ductility-dip cracking (DDC), an inter-mediate-temperature, solid-state cracking phenomenon. They experience an abnormal elevated-temperature ductility loss, which leads to cracking upon applying sufficient restraint. A unified mechanism for DDC has been elusive. To learn more about DDC, an experimental procedure has been designed and evaluated for use in future studies. It is a thermomechanical test that replicates welding conditions via simulated strain ratcheting (SSR) using the Gleeble thermomechanical simulator. This study evaluates SSR and aims to establish the procedure is reproducible and adequately optimized for producing DDC. A design of experiments was created with four alloys tested at varying preloads, elevated temperature strains, and a number of thermomechanical cycles. Mechanical energy imposed within the DDC temperature range was used for quantification of the effect of thermomechanical cycling on the DDC response. The materials tested were 310 stainless steel and Nickel 201 base metals as well as nickel-based filler metals 52M and 52MSS. The SSR successfully recreated DDC while maintaining higher fidelity to actual production conditions than past laboratory tests and offered a more controlled environment than large-scale weld tests. Therefore, the SSR will provide a viable experimental procedure for learning more about the DDC mechanism.

scholarly journals On the Size Effect of Strain Rate Sensitivity and Activation Volume for Face-Centered Cubic Materials: A Scaling Law

Crystals ◽  
2020 ◽  
Vol 10 (10) ◽  
pp. 898
Author(s):  
Xiazi Xiao ◽  
Hao Liu ◽  
Long Yu
Keyword(s):  
Size Effect ◽  
Strain Rate ◽  
Strain Rate Sensitivity ◽  
Indentation Depth ◽  
Activation Volume ◽  
Scaling Law ◽  
Rate Sensitivity ◽  
Face Centered Cubic ◽  
Cubic Materials ◽  
Face Centered

In a recent experimental study of indentation creep, the strain rate sensitivity (SRS) and activation volume v* have been noticed to be dependent on the indentation depth or loading force for face-centered cubic materials. Although several possible interpretations have been proposed, the fundamental mechanism is still not well addressed. In this work, a scaling law is proposed for the indentation depth or loading force-dependent SRS. Moreover, v* is indicated to scale with hardness H by the relation ∂ln(v*/b3)/∂lnH=−2 with the Burgers vector b. We show that this size effect of SRS and activation volume can mainly be ascribed to the evolution of geometrically necessary dislocations during the creep process. By comparing the theoretical results with different sets of reported experimental data, the proposed law is verified and a good agreement is achieved.

Voids in Irradiated Tungsten and Molybdenum

1969 ◽  
Vol 27 ◽  
pp. 190-191
Author(s):  
Robert C. Rau ◽  
Robert L. Ladd
Keyword(s):  
Melting Point ◽  
Fast Neutron ◽  
Neutron Irradiation ◽  
Elevated Temperatures ◽  
Irradiation Temperature ◽  
The Body ◽  
Face Centered Cubic ◽  
Body Centered Cubic ◽  
Cubic Metals ◽  
Face Centered

Recent studies have shown the presence of voids in several face-centered cubic metals after neutron irradiation at elevated temperatures. These voids were found when the irradiation temperature was above 0.3 Tm where Tm is the absolute melting point, and were ascribed to the agglomeration of lattice vacancies resulting from fast neutron generated displacement cascades. The present paper reports the existence of similar voids in the body-centered cubic metals tungsten and molybdenum.

A study of interface sliding at F.C.C.-B.C.C. boundaries in a Cu-Zn alloy

1978 ◽  
Vol 36 (1) ◽  
pp. 422-423
Author(s):  
F. Monchoux ◽  
A. Rocher ◽  
J.L. Martin
Keyword(s):  
Face Centered Cubic ◽  
Creep Tests ◽  
High Voltage Electron Microscopy ◽  
Diffusion Treatment ◽  
Voltage Electron ◽  
The Face ◽  
Face Centered ◽  
Interface Sliding ◽  
Zn Alloy ◽  
Made In

Interphase sliding is an important phenomenon of high temperature plasticity. In order to study the microstructural changes associated with it, as well as its influence on the strain rate dependence on stress and temperature, plane boundaries were obtained by welding together two polycrystals of Cu-Zn alloys having the face centered cubic and body centered cubic structures respectively following the procedure described in (1). These specimens were then deformed in shear along the interface on a creep machine (2) at the same temperature as that of the diffusion treatment so as to avoid any precipitation. The present paper reports observations by conventional and high voltage electron microscopy of the microstructure of both phases, in the vicinity of the phase boundary, after different creep tests corresponding to various deformation conditions.Foils were cut by spark machining out of the bulk samples, 0.2 mm thick. They were then electropolished down to 0.1 mm, after which a hole with thin edges was made in an area including the boundary

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