Transient Creep Behavior of γ-TiAl Polycrystals

1996 ◽  
Vol 460 ◽  
Author(s):  
B. Viguier ◽  
J. Bonneville ◽  
P. Spätig ◽  
J. L. Martin
Keyword(s):  
Plastic Strain ◽  
Strain Rate ◽  
Strain Hardening ◽  
Creep Behavior ◽  
Room Temperature ◽  
Constant Strain Rate ◽  
Transient Creep ◽  
Load Relaxation ◽  
Hardening Coefficient ◽  
Good Agreement

ABSTRACTTwo types of transient creep experiments performed along stress-strain curves are described and successfully applied to γ TiAl polycrystals at room temperature. They allow to determine activation volumes in good agreement with those measured through successive load relaxation tests. In addition, the combination of the latter method and the present ones provides relevant values of the plastic strain hardening coefficient. This latter parameter is found to exhibit similar values in transient as well as during constant strain rate tests.

An Experimental Study on the Effect of Prior Plastic Straining on Creep Behavior of 304 Stainless Steel

1993 ◽  
Vol 115 (2) ◽  
pp. 200-203 ◽  
Author(s):  
Z. Xia ◽  
F. Ellyin
Keyword(s):  
Stainless Steel ◽  
Plastic Strain ◽  
Strain Rate ◽  
Creep Behavior ◽  
Test Procedure ◽  
Constant Strain Rate ◽  
304 Stainless Steel ◽  
Creep Model ◽  
Plastic Strain Rate ◽  
Creep Tests

Constant strain-rate plastic straining followed by creep tests were conducted to investigate the effect of prior plastic straining on the subsequent creep behavior of 304 stainless steel at room temperature. The effects of plastic strain and plastic strain-rate were delineated by a specially designed test procedure, and it is found that both factors have a strong influence on the subsequent creep deformation. A creep model combining the two factors is then developed. The predictions of the model are in good agreement with the test results.

An Assessment of the Method Used to Determine Activation Parameters in L12 Alloys

1998 ◽  
Vol 552 ◽  
Author(s):  
B. Matterstock ◽  
G. Saada ◽  
J. Bonneville ◽  
J. L Martin
Keyword(s):  
Mechanical Properties ◽  
Theoretical Analysis ◽  
Plastic Strain ◽  
Strain Rate ◽  
Characteristic Time ◽  
Constant Strain Rate ◽  
Activation Parameters ◽  
Plastic Strain Rate ◽  
Clear Indication ◽  
Load Relaxation

ABSTRACTThe characterisation of dislocation mechanisms in connection with macroscopic mechanical properties are usually performed through transient tests, such as strain-rate jumps, load relaxations or creep experiments. The present paper includes a careful and complete theoretical analysis of the relaxation and the creep kinetics. We experimentally show that the plastic strain-rate is continuous at the transition between constant strain-rate conditions and both load relaxation and creep test. The product of the plastic strain-rate at the onset of the transient test () with the characteristic time (tk) of the transient is found to be independent of , as theoretically expected. This is a clear indication that the assumptions underlying the theoretical analysis are relevant.

Strain rate sensitivity and strain hardening response of DP1000 dual phase steel

2018 ◽  
Vol 115 (5) ◽  
pp. 507
Author(s):  
Onur Çavusoglu ◽  
Hakan Gürün ◽  
Serkan Toros ◽  
Ahmet Güral
Keyword(s):  
Tensile Strength ◽  
Strain Rate ◽  
Strain Hardening ◽  
Strain Rate Sensitivity ◽  
Dual Phase Steel ◽  
Rate Sensitivity ◽  
Dual Phase ◽  
Significant Difference ◽  
Load Carrying ◽  
Hardening Coefficient

In this study, strain hardening and strain rate sensitivity behavior of commercial DP1000 dual phase steel have been examined in detail at temperatures of 25 °C, 100 °C, 200 °C and 300 °C, at strain rates of 0.0016 s−1 and 0.16 s−1. As the strain rate has increased, the yield strength has increased but no significant change in tensile strength and strain hardening coefficient has been observed. As the temperature has increased, the yield and tensile strength has decreased in between 25 and 200 °C but it has showed an increase at 300 °C. The strain hardening coefficient has increased in parallel with temperature increase. It has been seen that the strain rate sensitivity has not been affected by temperature. No significant difference in the hardening rate has appeared in between 25 and 200 °C, but the highest value has been calculated at 300 °C. It has been determined that the fracture behavior has occurred earlier and load carrying capacity on necking has reduced with the increase of strain rate and not significantly affected by temperature.

Strain rate sensitivity of a mild steel at room temperature and strain rates of up to 105s−1

1980 ◽  
Vol 15 (4) ◽  
pp. 201-207 ◽  
Author(s):  
M S J Hashmi
Keyword(s):  
Finite Difference ◽  
Mild Steel ◽  
Strain Rate ◽  
Strain Hardening ◽  
Strain Rate Sensitivity ◽  
Elastic Strain ◽  
Room Temperature ◽  
Numerical Technique ◽  
Rate Sensitivity ◽  
Strain Rates

Experimental results on a mild steel are reported from ballistics tests which gave rise to strain rates of up to 105 s−1. A finite-difference numerical technique which incorporates material inertia, elastic-strain hardening and strain-rate sensitivity is used to establish the strain-rate sensitivity constants p and D in the equation, σ4 = σ1 (1+(∊/D)1/ p). The rate sensitivity established in this study is compared with those reported by other researchers.

Strain Hardening of Annealed 304 Stainless Steel by Creep

1993 ◽  
Vol 115 (4) ◽  
pp. 345-350 ◽  
Author(s):  
Han-Chin Wu ◽  
Chin-Cheng Ho
Keyword(s):  
Stainless Steel ◽  
Strain Hardening ◽  
Kinematic Hardening ◽  
Constant Strain Rate ◽  
Transient Creep ◽  
304 Stainless Steel ◽  
Isotropic Hardening ◽  
Loading Surface ◽  
Before And After ◽  
Strain Hardening Behavior

Combined axial-torsional experiments have been conducted at room temperature on thin-walled tubes to investigate the strain hardening behavior of annealed 304 stainless steel due to creep. The constant strain-rate dynamic loading (or SCISR) surfaces representing the state of material before and after creep have benn determined. It has been found that transient creep essentially causes the loading surface to undergo kinematic hardening with insignificant amount of isotropic hardening for this material. A conclusion is drawn that the loading surface hardened by transient creep is the same as that hardened by plastic deformation. This is true both for specimens with pure tension and pure torsion loading paths. The results confirm assumptions of the overstress theory of viscoplasticity.

scholarly journals The Effect of Test System Misalignment in the Dynamic Tension Test

1982 ◽  
Vol 104 (4) ◽  
pp. 285-290
Author(s):  
Han C. Wu ◽  
T. P. Wang ◽  
M. C. Yip
Keyword(s):  
Plastic Strain ◽  
Strain Rate ◽  
Constant Strain Rate ◽  
Test System ◽  
Tension Test ◽  
Neutral Axis ◽  
Dynamic Tension ◽  
Test Sheet

An analysis of test system misalignment is presented for dynamic tension test. Sheet type rectangular 1100-0 aluminum specimens are used for discussion. For a constant strain rate tension test, the strain rate is constant only on the neutral axis of the specimen. The lower the strain rate is, the more significant the misalignment errors become. The neutral axis will shift away from the centerline of the specimen as the plastic strain increases. But, it will reach a limit and will not completely move back to the centerline.

Tensile Properties of JLF-1 Steel at Elevated Temperature

2012 ◽  
Vol 204-208 ◽  
pp. 3872-3878
Author(s):  
Huai Lin Li
Keyword(s):  
Elevated Temperature ◽  
Strain Rate ◽  
Strain Hardening ◽  
Tensile Properties ◽  
Temperature Increase ◽  
Room Temperature ◽  
Shear Fracture ◽  
Plastic Body ◽  
Elastic Plastic ◽  
Dimple Fracture

In this paper, the tensile properties of JLF-1 steel at strain rate of 0.1%/s and 0.02%/s were studied from room temperature to 873K in vacuum using engineering specimens. The strain rate does not affect YS, UTS and RA as far as the tests performed in this study. Strain hardening of JLF-1 steel decreased significantly above 673 K, RA also increased rapidly above 673 K; and the surface fractography was changed from shear fracture below 673 K to dimple fracture at 773 K and 873 K. That means JLF-1 steel becomes perfect elastic-plastic body (without strain hardening) and ductility improved with temperature increase.

scholarly journals On the Room-Temperature Creep Behavior and Its Correlation with Length Scale of a Litao3 Single Crystal by Spherical Nanoindentation

Materials ◽  
2019 ◽  
Vol 12 (24) ◽  
pp. 4213
Author(s):  
Wei Hang ◽  
Xianwei Huang ◽  
Min Liu ◽  
Yi Ma
Keyword(s):  
Strain Rate ◽  
Single Crystal ◽  
Creep Behavior ◽  
Creep Deformation ◽  
Room Temperature ◽  
Length Scale ◽  
Compression Stress ◽  
Temperature Creep ◽  
Strain And Strain Rate ◽  
Room Temperature Creep

Relying on nanoindentation technology, the room-temperature creep behavior of a LiTaO3 single crystal in the typical orientation (01 1 ¯ 2), i.e., Y-42° plane was investigated. Three kinds of spherical tips with the radii of 0.76, 2.95 and 9.8 μm were respectively applied to detect nanoindentation length scale effect on creep deformation at both elastic and plastic regions. Superficially, both creep displacement and rate were nearly linearly increased with increasing holding depth and independent of tip size, which could be ascribed to the simultaneously enlarged holding strain and deformation volume beneath the indenter. At a similar holding strain, creep deformation, i.e., creep strain and strain rate were more pronounced under smaller spherical tips. Strain rate sensitivities of creep flows under different spherical tips and holding strains were also estimated. The potential room-temperature creep mechanism of LiTaO3 under high shear compression stress was discussed.

Transient creep behaviour of Ni3Al polycrystals

2000 ◽  
Vol 646 ◽  
Author(s):  
Tomas Kruml ◽  
Birgit Lo Piccolo ◽  
Jean-Luc Martin
Keyword(s):  
Strain Rate ◽  
Yield Point ◽  
Work Hardening ◽  
Creep Behaviour ◽  
Constant Strain Rate ◽  
Transient Creep ◽  
Peak Temperature ◽  
Creep Tests ◽  
Repeated Stress ◽  
Deformation Parameters

ABSTRACTRepeated creep tests were used for measuring various constant strain-rate deformation parameters. The results are consistent with those of repeated stress relaxations, although the precision is lower for creep in the present case. The small yield point observed in reloading after the transient is directly related to the amount of exhausted mobile dislocations, i.e. it originates from multiplication processes. During the transient test (180s total), the total exhaustion rate of mobile dislocations can be as high as 99%. It exhibits a maximum at the same T (about 500 K) as the work hardening. This supports the validity of a model which considers the work-hardening peak temperature to correspond to the stress under which incomplete Kear-Wilsdorf locks yield.

Superplasticity in Nanocrystalline Ni3Al and Ti Alloys

2000 ◽  
Vol 634 ◽  
Author(s):  
Sam X. Mcfadden ◽  
Alla V. Sergueeva ◽  
Tomas Kruml ◽  
Jean-Luc Martin ◽  
Amiya K. Mukherjee
Keyword(s):  
Grain Size ◽  
Strain Rate ◽  
Strain Hardening ◽  
Nanocrystalline Materials ◽  
Tensile Elongation ◽  
Constant Strain Rate ◽  
Grain Boundary Sliding ◽  
Simple Extension ◽  
Size Dependent ◽  
Enhanced Properties

ABSTRACTThe advent of nanocrystalline materials has provided new opportunities to explore grain size dependent phenomenon. Superplasticity is such a grain size dependent phenomenon defined by the ability to attain tensile elongation of 200% or more. Superplasticity in microcrystalline materials has been well characterized. The constitutive equations that describe microcrystalline superplasticity predict enhanced properties for nanocrystalline materials. Enhanced properties in such nanocrystalline material include lower superplastic temperature at constant strain rate, higher superplastic strain rate at constant temperature, and lower flow stresses. Investigations with nanocrystalline Ni3Al and ultra-fine grained Ti-6Al-4V alloy have shown a reduction in the superplastic temperature. However, the flow stresses in these materials are significantly higher than expected. The high flow stresses are accompanied by strong strain hardening.Transmission electron microscopy in situ straining of nanocrystalline Ni3Al has shown that grain boundary sliding and grain rotation occurred during straining. The sliding and rotation decreased with strain. Dislocation activity was observed but was not extensive. There was no observable dislocation storage. The parameters of the generalized constitutive equation for superplasticity for nanocrystalline Ni3Al and Ti-6Al-4V are in reasonable agreement with the parameters for microcrystalline material. The rate parameters suggest that nanocrystalline superplasticity shares common features with microcrystalline superplasticity. In contrast, the observed flow stresses and strong strain hardening indicate that nanocrystalline superplasticity is not a simple extension of microcrystalline behavior scaled to finer grain size.

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