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Title: Creep of 316 stainless steel
Author: Wang, D.
Awarding Body: University College of Swansea
Current Institution: Swansea University
Date of Award: 1994
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Constant stress creep tests were carried out for 316 stainless steel at 550, 600, 650 and 700oC over the stress range of 125 - 500 MPa. Entire creep curves were recorded by computer and creep curve shapes analysed. Within the stress and temperature range of the test matrix, creep curve shapes vary from tertiary dominant at low stress and temperature, to primary dominant at high temperature and mixed type at intermediate temperatures. Traditional parametric methods such as Larson-Miller, Orr-Dorn-Sherby and Manson-Succop methods were applied for the analysis of creep rupture life. The extrapolative capabilities of these parameters are limited because of the uncertainties involved in the estimation of constants, and the variation of these parameters with stress does not show a smooth 'master curve'. In order to model the entire creep curve rather than just a few creep properties, three different constitutive equations, i.e. equations from Continuum Damage Mechanics (CDM), equations proposed by researchers in National Physical Laboratory in development of Crispen mode, and the θ projection concept, were applied for the analysis of experimental data. Predictions by each approach were also compared with independent data from National Engineering Laboratory. Computer programmes were written for the estimation of constants involved in the CDM equations. No systematic trend was found in the variation of these constants with temperature. Therefore extrapolation of creep data by CDM approach can only be carried out on an isothermal basis. For the implementation of Crispen model, a new procedure for the estimation of equation constants was proposed. Using this procedure, the constants obtained were shown to vary systematically with stress and temperature, in a manner similar to the variation of the θ parameters with test conditions. The θ projection concept can accurately describe creep curve shapes and their variation with stress and temperature. Predictions of any creep properties can thus be made from short term test data to long duration.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available