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Research Papers: Materials and Fabrication

An Accelerated Method for Creep Prediction From Short Term Stress Relaxation Tests

[+] Author and Article Information
J. Q. Guo, F. Li, H. C. Shi, W. Z. Meng

Laboratory of Mechanical Structural Strength,
Anyang Institute of Technology,
1 Yellow-River Avenue,
Anyang, Henan 455000, China

X. T. Zheng

Hubei Provincial Key Laboratory of Chemical
Equipment Intensification and Intrinsic Safety,
Wuhan Institute of Technology,
Wuhan 430205, China
e-mail: xiaotaozheng@163.com

1Corresponding author.

Contributed by the Pressure Vessel and Piping Division of ASME for publication in the JOURNAL OF PRESSURE VESSEL TECHNOLOGY. Manuscript received May 11, 2015; final manuscript received November 23, 2015; published online February 5, 2016. Assoc. Editor: Marina Ruggles-Wrenn.

J. Pressure Vessel Technol 138(3), 031401 (Feb 05, 2016) (5 pages) Paper No: PVT-15-1096; doi: 10.1115/1.4032109 History: Received May 11, 2015; Revised November 23, 2015

Abstract

With the development of ultrasupercritical power generation technology, creep strength of high-temperature materials should be considered for safety evaluation and engineering design. However, long-time creep testing should be conducted by traditional creep assessment methods. This paper established a high-efficient prediction method for steady creep strain rate and creep strength based on short-term relaxation tests. Equivalent stress relaxation time and equivalent stress relaxation rate were defined according to stress relaxation characteristics and the Maxwell equation. An accelerated creep prediction approach from short-term stress relaxation tests was proposed by defining the equivalent relaxation rate as the creep rate during the steady stage. Stress relaxation and creep tests using high-temperature material 1Cr10NiMoW2VNbN steel were performed to validate the proposed model. Results showed that the experimental data are in good agreement with those predicted solutions. This indicates that short-term stress relaxation tests can be used to predict long-term creep behavior conveniently and reliably, and the proposed method is suitable for creep strength design and creep life prediction of 9–12%Cr steel used in ultrasupercritical unit at 600 °C.

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Figures

Fig. 1

Stress relaxation curve

Fig. 2

Sketch of equivalent stress relaxation time

Fig. 3

Stress relaxation testing specimen (mm)

Fig. 4

Stress relaxation testing curves at different initial stresses at 600 °C

Fig. 5

Creep curves at different stress levels

Fig. 6

Comparison of creep curves between the converted results (line) and experimental data (dot)

Fig. 7

Translated curve of equivalent relaxation rate versus stress

Fig. 8

Comparison of steady creep rates between the converted results and testing data

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