The standard ridged uniaxial testpiece: Computed accuracy of creep strain

Abstract

The creep rupture behaviour and the accuracy of the measured strains for the uniaxial tensile testpiece with extensomenter ridges have been studied by use of the Continuum Damage Mechanics (CDM)-based creep finite element solver, DAMAGE XX. Multi-axial creep constitutive equations with multi-damage state variables were used in the computer modelling process. The procedure models the development of failed regions of the testpiece due to the stress concentration in the transition regions from the parallel portion to the extensometer ridges. The accuracy of the creep strain measurement for the testpiece was investigated with the variation of time, gauge length, and stress levels. The computer modelling results show that although the error of the creep strain measurement is a fuction of time, it is dependent upon the stress sensitivity of the material law. For power-law material the maximum error is invariant of the normalized stress, but dependent upon the value of n; and for the sinh-based material law the maximum error is dependent upon the magnitude of the applied stress.

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References

BRITISH STANDARD 3500, Methods for creep and rupture testing of materials, 1969.

Day

M. F.

Harrison

G. F.

Design and calibration of extensometers and transducers, Measurement of High Temperature Mechanical Properties of Materials (Edited by Loveday

M. S.

Day

M. F.

Dyson

B. F.

), 1982, (HMSO, London), 225–240.

Guest

J. C.

Standards in elevated temperature tensile and uniaxial creep testing, Measurement of High Temperature Mechanical Properties of Material (Edited by Loveday

M. S.

Day

M. F.

Dyson

B. F.

), 1982, (HMSO, London), pp. 322–340.

Evans

R. W.

Wilshire

Creep of Metals and Alloys, 1985, (The Institute of Metals, London).

Breakwell

P. R.

Boxall

J. R.

Webster

G. A.

Specimen manufacture, Measurement of High Temperature Mechanical Properties of Material (Edited by Loveday

M. S.

Day

M. F.

Dyson

B. F.

1982 (HMSO, London), pp. 322–340.

Othman

A. M.

Hayhurst

D. R.

Dyson

B. F.

Skeletal point stresses in circumferentially notched tension bars undergoing tertiary creep modelled with physically-based constitutive equations, 1993, Proc. Roy. Soc., in press.

Dyson

B. F.

McLean

Particle-coarsening, σ0, and tertiary creep, Acta. Met., 1983, 30, 17–27.

Ashby

M. F.

Dyson

B. F.

Creep damage mechanics and micromechanisms, ICF Advances in Fracture Research (Edited by Valluri

S. R.

), 1984, (Pergamon Press, Oxford), pp. 3–30.

Tilly

G. P.

Harrison

G. F.

Interpretation of tensile and compressive creep behaviour of two nickel alloys, J. Strain Analysis, 1973, 8, 124–131.

10.

Dyson

B. F.

Creep and fracture of metals: Mechanisms and mechanics, Rev. Phys. Appl., 1988, 23, 605–613.

11.

Dyson

B. F.

Verma

A. K.

Szkopiak

Z. C.

The influence of stress state on creep resistance: Experiments and modelling, Acta Met., 1981, 29, 1573–1580.

12.

Dyson

B. F.

McLean

Creep of Nimonic 80A in torsion and tension, Met. Sci., 1977, 11, 37–45.

13.

Hayhurst

D. R.

Brown

P. R.

Morrison

C. J.

The role of continuum damage in creep crack growth, Phil. Trans. R. Sol. Lond., 1984, A311, 131–158.

14.

Dyson

B. F.

Loveday

M. S.

Creep in structures, IUTAM Symposium, (Edited by Ponter

A. R. S.

Hayhurst

D. R.

) 1981 (Springer-Verlag, Berlin, Germany), pp. 406–421.

15.

Hayhurst

D. R.

Dimmer

P. R.

Morrison

C. J.

Development of continuum damage in the creep rupture of notched bars, Phil. Trans. R. Sol. Lond., 1984, A311, 103–129.

16.

Othman

A. M.

Hayhurst

D. R.

Determination of low-strain multi-axial creep rupture criteria using notch-bar data, European J. Mech., 1993, in press.

17.

Othman

A. M.

Hayhurst

D. R.

Determination of high-strain multi-axial creep rupture criteria using notch-bar data, Int. J. Damage Mech., 1993, in press.