Creep Lifetime Under Constant Load and Constant Stress: Theory and Experiment

1996 ◽  
Vol 24 (4) ◽  
pp. 212 ◽  
Author(s):  
DR Petersen ◽  
RE Link ◽  
J Aktaa ◽  
B Schinke
Keyword(s):  
Constant Load ◽  
Constant Stress ◽  
Stress Theory ◽  
Theory And Experiment

High-Temperature Creep Tests of Two Creep-Resistant Materials at Constant Stress and Constant Load

2019 ◽  
Vol 827 ◽  
pp. 246-251
Author(s):  
Vàclav Sklenička ◽  
Květa Kuchařová ◽  
Marie Kvapilová ◽  
Luboš Kloc ◽  
Jiří Dvořák ◽  
...  
Keyword(s):  
Creep Behaviour ◽  
Constant Load ◽  
Complex Stress ◽  
Constant Stress ◽  
Fracture Mechanisms ◽  
Stress Tests ◽  
Creep Tests ◽  
Deformation And Fracture ◽  
Dependent Component ◽  
The Difference

Creep is defined as a time dependent component of plastic deformation. Creep tests can be performed either at constant load or at constant applied stress. Engineering creep tests carried out at constant load are aimed at determination of the creep strength or creep fracture strength, i.e. the data needed for design. The constant stress tests are important as a data source for fundamental investigations of creep deformation and fracture mechanisms and for finite element modelling of more complex stress situations. For some materials, the difference between the two type of testing can be very small, while for other materials is large, depending on the creep plasticity of the material under testing. The paper aims to compare the creep results of two different creep-resistant materials: the advanced 9%Cr martensitic steel (ASME Grade P91) and a Zr1%Nb alloy obtained by both testing methods and to clarify the decisive factors causing observed differences in their creep behaviour.

An Empirical Creep Law From a Single Test

1962 ◽  
Vol 84 (2) ◽  
pp. 236-238
Author(s):  
Iain Finnie
Keyword(s):  
Strain Rate ◽  
Creep Test ◽  
Constant Load ◽  
Constant Stress ◽  
Single Test ◽  
Creep Tests ◽  
Stress Strain ◽  
Strain And Strain Rate ◽  
Single Constant

A method is described by which an empirical creep law, relating stress, strain, and strain rate, may be obtained from a single constant-load creep test. An example to illustrate the method is given, and the empirical creep law is compared with the results of several constant stress creep tests.

Design of Apparatus for Constant-Stress or Constant-Load Creep Tests

1962 ◽  
Vol 84 (2) ◽  
pp. 287-293 ◽  
Author(s):  
F. Garofalo ◽  
O. Richmond ◽  
W. F. Domis
Keyword(s):  
Constant Load ◽  
Constant Stress ◽  
Large Strains ◽  
Creep Tests ◽  
Specimen Length ◽  
Ductile Metals ◽  
Initial Specimen ◽  
Load Axis ◽  
Initial Setting ◽  
Made In

Apparatus has been designed and built for conducting creep tests under constant-stress or constant-load conditions. An exact mathematical solution describing the shape of the cam lever for constant stress is given. This solution applies for the large strains usually found for ductile metals and alloys, as long as the strain is uniform. The initial specimen length employed in a constant-stress creep test ordinarily is fixed by the dimensions of the cam system used. It is shown by the present analysis that the initial specimen length may be changed if an approximate adjustment is made in the initial setting of a properly designed cam lever. The direction of the load axis remains fixed and therefore the apparatus has the advantage of a more complex level-beam machine. The results of a number of creep tests under constant-stress conditions are reported.

Comparison of Constant-Load and Constant-Stress Tensile Creep Data for an Aluminium-0.07 Percent Titanium Alloy at 250°C

1967 ◽  
Vol 9 (2) ◽  
pp. 81-85 ◽  
Author(s):  
J. Fairbairn
Keyword(s):  
Experimental Data ◽  
Titanium Alloy ◽  
Power Law ◽  
Constant Load ◽  
Time Function ◽  
Constant Stress ◽  
Tensile Creep ◽  
Creep Data

Constant-stress tensile creep data were obtained from an aluminium-0.07 per cent titanium alloy at 250°C and correlated using a power law of the form: To obtain a better fit to the experimental data in the higher strain regions a modified time function was selected and the experimental data correlated using an equation of the form: This equation was used to obtain theoretical constant-load curves which are compared with experimental constant-load data previously obtained from the same billet of material.

scholarly journals Longitudinal Strain Pulse Propagation in Wide Rectangular Bars: Part 2—Experimental Observations and Comparisons With Theory

1963 ◽  
Vol 30 (1) ◽  
pp. 61-69 ◽  
Author(s):  
O. E. Jones ◽  
A. T. Ellis
Keyword(s):  
Plane Stress ◽  
Pulse Propagation ◽  
Step Function ◽  
Pressure Loading ◽  
Stress Theory ◽  
Second Mode ◽  
Fringe Patterns ◽  
Strain Pulse ◽  
Thickness Mode ◽  
Theory And Experiment

The plane-stress theory presented in Part 1 is shown to predict qualitatively the warping of plane sections observed in transient fringe patterns obtained using birefringent coatings and in dynamic photoelastic pictures obtained in other investigations. Measurements using conventional techniques are described in which wide rectangular bars were subjected to a longitudinal step-function pressure loading produced by a shock tube. Comparisons show that the gross features of the experimental records for the head of the pulse are qualitatively predicted by the theory. Both theory and experiment show that short-wavelength, second-mode disturbances arrive very early. Experimentally it is observed that these disturbances are accomplished by thickness-mode activity which cannot be accounted for by the plane-stress theory.

Impression creep of lead

1994 ◽  
Vol 9 (4) ◽  
pp. 903-908 ◽  
Author(s):  
Donyau Chiang ◽  
J. C. M. Li
Keyword(s):  
Creep Test ◽  
Elevated Temperatures ◽  
Constant Load ◽  
Constant Stress ◽  
Tensile Creep ◽  
Indentation Creep ◽  
Impression Creep ◽  
Creep Tests ◽  
Creep Measurements ◽  
Cylindrical Punch

The impression creep behavior of lead was investigated using a 100 μm diameter punch at ambient and elevated temperatures (433 K-563 K) under punching stresses of 6–70 MPa. The results were compared with the data obtained from conventional creep tests reported in the literature. Unlike the indentation creep test, the impression creep test showed a steady-state velocity after a short transient period when the flat-end cylindrical punch was pushed against the lead surface by a constant load. Both the temperature and stress dependences were comparable to those of the constant stress tensile creep tests under similar conditions. A master curve for lead was established by collecting data from the impression creep tests and the constant stress tensile creep tests. The indentation creep measurements for lead were included also. However, the indentation data depend on the load applied.

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