Quantification and assessment of the error associated with engineering stress-strain analysis in stress accelerated creep tests in 316H stainless steel

ABSTRACT

Historically, reduction of area has been neglected during uniaxial creep tests, and engineering rather than true stress-strain and strain rate have been considered. In high load accelerated tests, there is an increasing error associated with the engineering stress and strain, hence this assumption is no longer valid. In this work, uniaxial creep tests on Type 316H austenitic stainless steel at 480–550 °C have been analysed for both engineering and true stress–strain and strain rate. Significantly higher stresses and lower minimum strain rates were determined from true stress-strain rate relationships for as-received 316H. These differences diminish as the material is strain hardened, limiting plastic loading strains and reducing creep ductility. The true stress-strain rate analysis method is shown to be more accurate, however, the engineering stress-strain analysis predicts higher creep strain rates for a given stress and is the more conservative measure for component lifetime assessments.

KEYWORDS:

• Accelerated creep test
• creep strain
• austenitic stainless steel
• pre-compression
• true stress and true strain

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

The work was supported by the EDF Energy EDF Energy Research and Development Engineering and Physical Sciences Research Council [2434261]; Engineering and Physical Sciences Research Council [EP/V038079/1].