A Code of Practice for conducting notched bar creep tests and for interpreting the data

In this investigation finite element calculations have been performed to obtain the creep stress distributions generated in circumferentially notched bar test-pieces. They have also been made to determine the relation between axial extension and notch throat diameter changes. It has been found that an approximate skeletal point can be identified where the stress state is insensitive to the power law stress dependence of creep. Consistent trends in skeletal point stress ratios to those given in an existing Code of Practice for notch bar creep testing have been obtained. Nevertheless up-dated values, particularly for sharp notches, are proposed and these have now been inserted into a new version of the Code of Practice. In contrast the link between extension and notch throat diameter changes has been found to depend on the creep stress index as well as the notch geometry. It is anticipated that the analysis can be used to establish the multi-axial creep stress deformation and rupture behaviour of materials.

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“…The geometry of notched bar specimens examined corresponded with that recommended in the revised Code of Practice 5 and shown in Fig. 1.…”

Section: Calculationsmentioning

confidence: 99%

Finite element analysis of notched bar skeletal point stresses and dimension changes due to creep

Webster

Nikbin

Biglari

2004

Fatigue Fract Eng Mat Struct

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“…R55 mm), is prescribed by the code of practice for conducting notched bar creep tests, as (dzR)510 mm. 15 Therefore, for the dimensions used in this investigation, the stress concentration factor due to a notch was not affected by presence of another notch and the two notches were behaving independently.…”

Section: Fea Resultsmentioning

confidence: 98%

Effect of notch root radius on tensile behaviour of 316L(N) stainless steel

Kumar

Nandagopal

Laha

et al. 2014

Materials at High Temperatures

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Type 316L(N) stainless steel (SS) is used as the major structural material for high temperature components of sodium cooled fast reactors. The influence of notch root radius on the tensile behaviour of 316L(N) SS under multi-axial stress state was investigated. Double U-notches with five different kinds of notch geometry were incorporated symmetrically into the tensile testing specimens by changing the notch root radius while keeping the gross diameter, net diameter and notch depth as the same for all the notches. The notch root radius was varied as 0?25, 0?5, 1?25, 2?5 and 5 mm. Tensile tests were carried out on the notched specimens at room temperature (298 K) and at 923 K at a constant strain rate of 3610 23 s 21 . The tensile strength and yield strength of notched specimen of 316L(N) SS increased with decrease in notch radius at both the temperatures and the notch severity was less pronounced at high temperature. The fractured notch surface was analysed using scanning electron microscope and unfractured notch was sliced along the axis and observed under optical microscope. Finite element analysis was performed on the models of notched specimens with various notch root radii. These results showed that Von Mises equivalent stress which was derived from triaxial stresses decreased with decrease in notch radius. The shift of location of peak values of maximum principal stress and hydrostatic stress towards the axis of the specimen, leading to formation of cracks, occurred at a lower nominal stress when the notch radius was increased.

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“…The gauge length of the creep test specimen is five times greater than its diameter, which meets the minimum requirement as given in [12]. Specimen 1 received no pre-strain.…”

Section: Materials and Experimentalmentioning

confidence: 99%

Internal strains between grains during creep deformation of an austenitic stainless steel

Chen

Wang

et al. 2015

J Mater Sci

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Internal strains that develop between grains during creep of an austenitic stainless steel were measured using in situ neutron diffraction. The secondary creep prestrained test specimens were considered. Measurements were undertaken before, during and post creep deformation at 550°C. There was no measurable change of internal strains between grains during in situ creep for 4 h at 550°C. In addition, the effect of increasing/reducing temperatures in a range from 470 to 550°C on the internal strains was measured and interpreted with respect to contributions from thermal expansion/contraction. No further internal misfit strains between grains were created when specimen crept during the dwell time at 530, 510, 490 and 470°C. Results are discussed with respect to (i) the general structure of self-consistent models and (ii) the optimised use of neutron sources for creep studies.

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A Code of Practice for conducting notched bar creep tests and for interpreting the data

Cited by 98 publications

References 27 publications

Finite element analysis of notched bar skeletal point stresses and dimension changes due to creep

Finite element analysis of notched bar skeletal point stresses and dimension changes due to creep

Effect of notch root radius on tensile behaviour of 316L(N) stainless steel

Internal strains between grains during creep deformation of an austenitic stainless steel

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