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.

An Investigation of Transient Creep by Means of Endochronic Viscoplasticity and Experiment

1995 ◽  
Vol 117 (3) ◽  
pp. 260-268 ◽  
Author(s):  
Han C. Wu ◽  
Chin C. Ho
Keyword(s):  
Stainless Steel ◽  
Strain Rate ◽  
Creep Strain ◽  
Constant Strain Rate ◽  
Transient Creep ◽  
Constant Stress ◽  
Stress Rate ◽  
304 Stainless Steel ◽  
Unified Approach ◽  
Creep Tests

Creep of metals has been investigated by means of the endochronic constitutive equation. This is a unified approach. Transient creep tests have been conducted on 304 stainless-steel specimens with carefully monitored precreep loading stage, either loaded at a prescribed constant strain-rate or at a constant stress-rate. It has been found that, for the same hold stress, the creep strain is larger for test with a constant stress-rate preloading than that for a constant strain-rate preloading. This is an effect of plasticity-creep interaction. In all cases, the initial creep strain rate is a continuation of the preloading strain rate. The theory satisfactorily describes the experimental results.

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.

scholarly journals The Mechanical Properties of Single Crystals of Pure Ice

1969 ◽  
Vol 8 (54) ◽  
pp. 463-473 ◽  
Author(s):  
S. J. Jones ◽  
J. W. Glen
Keyword(s):  
Mechanical Properties ◽  
Strain Rate ◽  
Single Crystals ◽  
Fracture Stress ◽  
Constant Strain Rate ◽  
Tensile Creep ◽  
Stress Dependence ◽  
Creep Tests ◽  
Dislocation Multiplication ◽  
Compressive Tests

AbstractResults obtained from tensile and compressive tests on pure ice single crystals at various temperatures down to −90°C are reported. At −50°C tensile creep tests give a continually increasing creep rate until fracture, as observed at higher temperatures. The stress dependence of the strain-rate is discussed. Fracture stress increases with decreasing temperature. Results from constant strain-rate compressive tests are compared with theoretical curves computed from Johnston’s (1962) theory of dislocation multiplication. A dislocation velocity of the order of 0.5×10−8 m s−1 is deduced for ice at −50°C.

High Temperature Plastic Behaviour of Icosahedral AlCuFe Quasicrystals.

2000 ◽  
Vol 643 ◽  
Author(s):  
Jan Fikar ◽  
Joël Bonneville ◽  
Nadine Baluc ◽  
Pierre Guyot
Keyword(s):  
Strain Rate ◽  
Constant Strain Rate ◽  
Friction Stress ◽  
Dislocation Model ◽  
Compression Tests ◽  
Creep Tests ◽  
Flow Strength ◽  
Stress Strain ◽  
Softening Effect ◽  
Dislocation Interaction

AbstractIcosahedral AlCuFe poly-quasicrystalline specimens were deformed in constant strain rate compression tests at temperatures ranging between 300K - 1020K. Below nearly 0.7 Tm (Tm is the melting temperature) the specimens were brittle. Above the brittle-to-ductile transition temperature, after the elastic stage the stress-strain curves exhibit a marked yield-point followed by a stage of strain softening only. Transient creep tests were performed at different given stress/strain levels after interrupting the constant strain-rate deformation tests. After the transient tests, the flow strength of the specimens was investigated anew at constant strain rate. The results are interpreted in the framework of a dislocation model, where two effects opposing dislocation movement are considered: firstly, the usual elastic dislocation interaction, yielding a work-hardening contribution, and, secondly, a friction stress specific to the quasiperiodic lattice, leading to a softening effect.

Uniaxial Constant Compressive Stress Creep Tests on Sea Ice

1995 ◽  
Vol 117 (4) ◽  
pp. 283-289 ◽  
Author(s):  
N. K. Sinha ◽  
C. Zhan ◽  
E. Evgin
Keyword(s):  
Compressive Strength ◽  
Sea Ice ◽  
Strain Rate ◽  
Compressive Stress ◽  
Axial Strain ◽  
Acoustic Emissions ◽  
Constant Strain Rate ◽  
Rate Sensitivity ◽  
Load Test ◽  
Creep Tests

First-year columnar-grained sea ice from Resolute Passage (74° 42′ N, 94° 50′ W), off Barrow Strait in the Canadian High Arctic, was tested under constant uniaxial compressive stress applied normal to the length of the columns. Creep tests were performed at 263 K, 253 K, and 243 K in the stress range of 0.7 to 2.5 MPa, using prismatic samples with dimensions of 50 mm × 100 mm × 250 mm. Because three-dimensional creep data are extremely useful for developing constitutive equations, axial strain was measured in conjunction with the measurements of two lateral strains and acoustic emissions. The deformations were measured using displacement gages mounted on the samples. A description of the experimental procedures and the observations are presented here. One-to-one correspondence has been obtained between the present results on the dependence of minimum creep rate on stress and previous data on the dependence of uniaxial compressive strength on strain rate under constant strain rate. The strain-rate sensitivity of compressive strength can, therefore, be obtained from creep tests which can be performed by using simple dead-load test systems.

In situ SEM Observations of the Tensile-Creep Deformation Behavior and Fracture Mechanisms of a γ-TiAl Intermetallic Alloy at Low and High Stresses.

2012 ◽  
Vol 1516 ◽  
pp. 65-70
Author(s):  
R. Muñoz-Moreno ◽  
M. T. Pérez-Prado ◽  
E.M. Ruiz-Navas ◽  
C. J. Boehlert ◽  
J. Llorca
Keyword(s):  
Crack Propagation ◽  
Strain Rate ◽  
Crack Nucleation ◽  
Constant Strain Rate ◽  
Intermetallic Alloy ◽  
Tensile Creep ◽  
Creep Tests ◽  
Secondary Cracks ◽  
Secondary Stage

ABSTRACTThe effect of stress on the deformation and crack nucleation and propagation mechanisms of a γ-TiAl intermetallic alloy (Ti-45Al-2Nb-2Mn (at.%) - 0.8v.%TiB2) was studied by means of in situ tensile (constant strain rate) and tensile-creep (constant load) experiments performed at 973 K inside a scanning electron microscope (SEM). The evolution of the microstructure and the nucleation and propagation of cracks was tracked during the high temperature mechanical tests in the SEM. Colony boundary crack nucleation was found to be activated during the secondary stage in creep tests at 300 MPa and 400 MPa and during the tertiary stage of the creep tests performed at higher stresses and at constant strain rate. Interlamellar ledges were only observed during the high stress tensile-creep tests (σ>400 MPa) and during the constant strain rate test. Quantitative measurements of the nature of the crack propagation path along secondary cracks and along the primary crack were carried out. It was found that colony boundaries were preferential sites for crack propagation under all the conditions investigated. The frequency of interlamellar cracking increased with increasing stress.

Study on Hot Deformation Behavior and Constitutive Relation of Cr-77.5Nb Alloy

2014 ◽  
Vol 898 ◽  
pp. 72-75
Author(s):  
Wen Wen Han ◽  
Shi Qiang Lu ◽  
Li Ping Deng
Keyword(s):  
Strain Rate ◽  
Constitutive Relation ◽  
Hot Deformation ◽  
Deformation Behavior ◽  
Stepwise Regression ◽  
Constant Strain Rate ◽  
Isothermal Compression ◽  
Hot Deformation Behavior ◽  
Deformation Parameters ◽  
Temperature Strain

Isothermal compression test at constant strain rate for Cr-77.5Nb alloy were performed on Gleeble simulator with conditions of deformation temperature from 800 to 1200°C and strain rate from 0.001s-1to 0.1s-1. The influence of deformation parameters including temperature, strain rate and strain related with flow stress during hot deformation were investigated and the constitutive relation of Cr-77.5Nb alloy was established by stepwise regression method. The result of error analysis shows that the constitutive relation established has high accuracy and can well characterize the hot deformation behavior of this alloy.

scholarly journals The Mechanical Properties of Single Crystals of Pure Ice

1969 ◽  
Vol 8 (54) ◽  
pp. 463-473 ◽  
Author(s):  
S. J. Jones ◽  
J. W. Glen
Keyword(s):  
Mechanical Properties ◽  
Strain Rate ◽  
Single Crystals ◽  
Fracture Stress ◽  
Constant Strain Rate ◽  
Tensile Creep ◽  
Stress Dependence ◽  
Creep Tests ◽  
Dislocation Multiplication ◽  
Compressive Tests

Abstract Results obtained from tensile and compressive tests on pure ice single crystals at various temperatures down to −90°C are reported. At −50°C tensile creep tests give a continually increasing creep rate until fracture, as observed at higher temperatures. The stress dependence of the strain-rate is discussed. Fracture stress increases with decreasing temperature. Results from constant strain-rate compressive tests are compared with theoretical curves computed from Johnston’s (1962) theory of dislocation multiplication. A dislocation velocity of the order of 0.5×10−8 m s−1 is deduced for ice at −50°C.

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