Constitutive modelling of primary creep for age forming an aluminium alloy

This paper presents an extension of the Ramaswamy, Stouffer, and Laflen unified elastic–viscoplastic theory which uses internal state variables to represent a strain rate insensitive aluminium alloy namely 7050-T7451 alloy. The model constants are evaluated from the results of a uniaxial tensile test, with strain hold at saturation, and a fatigue loop. Strain holds in the saturated region of tensile monotonic curves resulted in significant amounts of stress relaxation. The material response is cyclically stable and reveals a strong Bauschinger effect. There is a significant reduction in the yield stress between the initial yield and the subsequent tensile yield stress observed after a fully reversed fatigue cycle. All of these material characteristics were predicted successfully.

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The investigation of primary creep regeneration for 10%Cr martensitic steel: Unified constitutive modelling

International Journal of Mechanical Sciences ◽

10.1016/j.ijmecsci.2020.106044 ◽

2021 ◽

Vol 190 ◽

pp. 106044

Author(s):

X. Li ◽

S.R. Holdsworth ◽

E. Mazza ◽

E. Hosseini

Keyword(s):

Martensitic Steel ◽

Primary Creep ◽

Constitutive Modelling

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Investigation of Tensile and Compressive Creep Behaviour of AA2050-T34 during Creep Age Forming Process

Key Engineering Materials ◽

10.4028/www.scientific.net/kem.716.323 ◽

2016 ◽

Vol 716 ◽

pp. 323-330 ◽

Cited By ~ 1

Author(s):

Yong Li ◽

Zhusheng Shi ◽

Yo Lun Yang ◽

Jian Guo Lin

Keyword(s):

Power Law ◽

Creep Behaviour ◽

Primary Creep ◽

Constitutive Modelling ◽

Ageing Process ◽

Forming Process ◽

Creep Equation ◽

Compressive Creep ◽

Creep Stress ◽

Creep Age Forming

The tensile and compressive creep behaviour of aluminium alloy 2050 with T34 initial temper (AA2050-T34) during creep-ageing process has been experimentally investigated and analysed in detail. Both tensile and compressive creep-ageing tests under various stress levels (ranging from 100 MPa to 187.5 MPa) have been carried out at a temperature of 155 °C for 18 hours. The results show that creep strains under tensile stresses are much larger than those under the same levels of compressive stresses and a new “double primary creep feature” with five-stage creep behaviour has been observed in the alloy during the creep-ageing tests. The conventional power-law creep equation was applied to analyse the new creep behaviour of the alloy at the steady-state creep stage. Furthermore, the power-law relationship between the applied stress and the corresponding creep strain rate was found to be effective in all creep-ageing stages of the alloy and was used for further analysis. These analyses indicate that the dislocation and diffusion mechanisms may both contribute to this new creep behaviour and may play different roles in different creep-ageing stages. Moreover, the evolution of the creep resistance or threshold creep stress of the alloy during the creep-ageing process was quantitatively investigated by the proposed relationship. These results help to not only understand the new creep behaviour of AA2050-T34 during the creep-ageing process, but also facilitate further constitutive modelling of this new creep behaviour for its creep age forming applications.

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