scholarly journals A Classification of flow-Stress Anomalies, and the Specific Role of Strain Rate Sensitivity

1996 ◽  
Vol 06 (C2) ◽  
pp. C2-189-C2-198 ◽  
Author(s):  
F. Louchet
Keyword(s):  
Flow Stress ◽  
Strain Rate ◽  
Strain Rate Sensitivity ◽  
Rate Sensitivity ◽  
Specific Role

Anomalous Strain Rate Sensitivity of Flow Stress in Ni3Ge Single Crystals. The role of Point Defects

2017 ◽  
Vol 60 (3) ◽  
pp. 494-501
Author(s):  
Yu. V. Solov’eva ◽  
V. A. Starenchenko ◽  
O. D. Pantyukhova ◽  
S. V. Starenchenko ◽  
A. N. Solov’ev ◽  
...  
Keyword(s):  
Flow Stress ◽  
Strain Rate ◽  
Single Crystals ◽  
Strain Rate Sensitivity ◽  
Point Defects ◽  
Rate Sensitivity

The Simulation and Role of Discontinuous Yield Behaviors of Material

2010 ◽  
Vol 163-167 ◽  
pp. 4590-4594
Author(s):  
Shao Wei Hu
Keyword(s):  
Strain Rate ◽  
Strain Rate Sensitivity ◽  
Rate Sensitivity ◽  
Stress Rate ◽  
Instability Criterion ◽  
Stress Strain ◽  
Dynamic Behaviors ◽  
Jerky Flow ◽  
Thermal Origin

Discontinuous yield of material as Jerky flow was explained. Then, the strain rate sensitivity (SRS) and instability criterion was given out. Some tests were carried out at constant stress rate, so Jerky flow is manifested as a discontinuity in the stress-strain curves in form of strain bursts. Finally, the dynamic behaviors of specimens during instability of thermal origin were simulated with COLSYS software, whose results are good with test ones.

The strain-rate sensitivity of the hardness in indentation creep

2007 ◽  
Vol 22 (4) ◽  
pp. 926-936 ◽  
Author(s):  
A.A. Elmustafa ◽  
S. Kose ◽  
D.S. Stone
Keyword(s):  
Flow Stress ◽  
Strain Rate ◽  
Strain Rate Sensitivity ◽  
Rate Sensitivity ◽  
Hertzian Contact ◽  
Indentation Creep ◽  
Proportionality Factor ◽  
Element Analysis ◽  
Elastic Deformations ◽  
The Relationship

Finite element analysis is used to simulate indentation creep experiments with a cone-shaped indenter. The purpose of the work is to help identify the relationship between the strain-rate sensitivity of the hardness, νH, and that of the flow stress, νσ in materials for which elastic deformations are significant. In general, νH differs from νσ, but the ratio νH/νσ is found to be a unique function of H/E* where H is the hardness and E* is the modulus relevant to Hertzian contact. νH/νσ approaches 1 for small H/E*, 0 for large H/E*, and is insensitive to work hardening. The trend in νH/νσ as a function of H/E* can be explained based on a generalized analysis of Tabor’s relation in which hardness is proportional to the flow stress H = k × σeff and in which the proportionality factor k is a function of σeff/E*.

scholarly journals Strain Rate Sensitivity of Alloys 800H and 617

2013 ◽  
Author(s):  
J. K. Wright ◽  
J. A. Simpson ◽  
R. N. Wright ◽  
L. J. Carroll ◽  
T. L. Sham
Keyword(s):  
High Temperature ◽  
Flow Stress ◽  
Strain Rate ◽  
Strain Rate Sensitivity ◽  
Rate Sensitivity ◽  
Temperature Limit ◽  
Applied Strain ◽  
Alloy 800H ◽  
Alloy 617 ◽  
Temperature Heat

The flow stress of many materials is a function of the applied strain rate at elevated temperature. The magnitude of this effect is captured by the strain rate sensitivity parameter “m”. The strain rate sensitivity of two face–center cubic solid solution alloys that are proposed for use in high temperature heat exchanger or steam generator applications, Alloys 800H and 617, has been determined as a function of temperature over that range of temperatures relevant for these applications. In addition to determining the strain rate sensitivity, it is important for nuclear design within Section III of the ASME Boiler and Pressure Vessel Code to determine temperature below which the flow stress is not affected by the strain rate. This temperature has been determined for both Alloy 800H and Alloy 617. At high temperature the strain rate sensitivity of the two alloys is significant and they have similar m values. For Alloy 617 the temperature limit below which little or no strain rate sensitivity is observed is approximately 700°C. For Alloy 800H this temperature is approximately 650°C.

Strain Rate Dependence of the Flow Stress and Work-Hardening of Single Crystals of NI3(Al,Hf)B

1994 ◽  
Vol 364 ◽  
Author(s):  
S. S. Ezz ◽  
Y. Q. Sun ◽  
P. B. Hirsch
Keyword(s):  
Flow Stress ◽  
Strain Rate ◽  
Temperature Dependence ◽  
Single Crystals ◽  
Yield Stress ◽  
Strain Rate Sensitivity ◽  
Work Hardening ◽  
Room Temperature ◽  
Rate Sensitivity ◽  
Controlling Mechanism

AbstractThe strain rate sensitivity ß of the flow stress τ is associated with workhardening and β=(δτ/δln ε) is proportional to the workhardening increment τh = τ - τy, where τy is the strain rate independent yield stress. The temperature dependence of β/τh reflects changes in the rate controlling mechanism. At intermediate and high temperatures, the hardening correlates with the density of [101] dislocations on (010). The nature of the local obstacles at room temperature is not established.

Microstructure and Plasticity of Hot Deformed 5083 Aluminum Alloy Produced by Rapid Solidification and Hot Extrusion / Badania Mikrostruktury I Plastyczności Odkształcanego Na Gorąco Szybko-Krystalizowanego I Wyciskanego Stopu Aluminium 5083

2012 ◽  
Vol 57 (4) ◽  
pp. 1253-1259 ◽  
Author(s):  
T. Tokarski ◽  
Ł. Wzorek ◽  
H. Dybiec
Keyword(s):  
Aluminum Alloy ◽  
High Temperature ◽  
Flow Stress ◽  
Strain Rate ◽  
Strain Rate Sensitivity ◽  
Rate Sensitivity ◽  
Temperature Range ◽  
Rapidly Solidified ◽  
5083 Aluminum Alloy ◽  
Conventionally Cast

The objective of the present study is to analyze the mechanical properties and thermal stability for rapidly solidified and extruded 5083 aluminum alloy (RS). Compression tests were performed in order to estimate flow stress and strain rate sensitivity relation for 5083 alloy in the temperature range of 20°C to 450°C. For the comparison purposes, conventionally cast and extruded industrial material (IM) was studied as well. Deformation tests performed at room temperature conditions show that rapidly solidified material exhibits about 40% higher yield stress (YS=320 MPa) than conventionally cast material (YS=180 MPa), while the deformation at 450°C results in significant decrease of flow stress parameters for RS material (YS=20 MPa) in comparison to IM material (YS=40 MPa). Strain rate sensitivity parameter determined for high temperature conditions indicates superplasticity behavior of RS material. Structural observations show that under conditions of high-temperature deformation there are no operating recrystallization mechanisms. In general, grain size below 1µm and size of reinforcing phases below 50 nm is preserved within the used deformation temperature range.

Onset of the Portevin-Le Chatelier Effect: Role of Synchronization of Dislocations

2014 ◽  
Vol 783-786 ◽  
pp. 198-203 ◽  
Author(s):  
Tatiana Lebedkina ◽  
Nikolay P. Kobelev ◽  
Mikhail Lebyodkin
Keyword(s):  
Flow Stress ◽  
Strain Rate ◽  
Collective Motion ◽  
Rate Sensitivity ◽  
Plastic Instability ◽  
Strain Rate Range ◽  
Dislocation Dynamics ◽  
Transient Kinetics ◽  
Kinetic Measurements

The problem of the onset of the Portevin-Le Chatelier (PLC) effect is revised by combining a study of the kinetics of the flow stress evolution upon abrupt changes in the applied strain rate and acoustic emission (AE) accompanying plastic deformation of an AlMg alloy. The kinetic measurements allow evaluating the strain-rate sensitivity of the flow stress and the time characteristics of transient processes as functions of plastic strain. Using known criteria of plastic instability, domains of instability are constructed in the (strain, strain rate) plane. A particular accent is put on the strain-rate range corresponding to the so-called “inverse” behavior. The comparison of such maps with experimental data on the critical strain testifies to the insufficiency of these criteria for explaining the onset of the PLC effect. Moreover, the slow transient kinetics contradicts observations of the fast development of stress drops. The AE measurements bear witness that the stress serrations are associated with bursts in duration of acoustic events generated by the collective motion of dislocations. The possible role of synchronization of dislocation dynamics on the onset of plastic instability is discussed.

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