Long term stress relaxation modelling

Stefan Holmström, Pertti Auerkari, Valerie Friedmann, Andreas Klenk, Benjamin Leibing, P. Buhl, Mike Spindler, Andrea Riva

    Research output: Chapter in Book/Report/Conference proceedingConference article in proceedingsScientificpeer-review


    Data assessments, materials modelling and development as well as recommendations for model selection have been a main objective of the ECCC Working Group 1. This paper describes the latest inter-comparison round robin on relaxation modelling. Most models found in the public domain are limited in either strain range or temperature. Here the bolting steel 1Cr-0.5Mo-0.25V steel tested by NIMS, Japan is assessed by a number of assessors striving to define models capable of predicting the relaxation in the full data range, i.e. in both strain (0.1-0.25% total strain) and temperature (450-550°C). The assessors use methods of their own preference giving all model parameters to enable interpolation/extrapolation and calculation of prediction errors within the range of data. The methods include forward creep with different creep strain models as base, classical relaxation models, parametric (Time-Temperature-Parameter curve families) solutions and entirely new modelling approaches. The main target is the general overall model for prediction of relaxed stress up to 3 000 h hold time. However, the model robustness is tested by fitting to a drastically culled data set consisting of only the short term data with durations of 0.1 to 10h. The predictive performance of the models optimised for the short term data are compared with the long term data as well as the long term models. Conclusions and recommendations are given on model interpolation performance, extrapolation ability and model complexity.
    Original languageEnglish
    Title of host publicationECCC 2014: Creep & fracture in high temperature components
    Subtitle of host publicationDesign & life assessment
    Number of pages15
    ISBN (Electronic)978-88-7484-510-1
    Publication statusPublished - 2014
    MoE publication typeA4 Article in a conference publication
    Event3rd International ECCC Conference, ECCC 2014: ECCC 2014 Creep & Fracture in High Temperature Components, Design & Life Assessment - Rome, Italy
    Duration: 5 May 20147 May 2014
    Conference number: 3


    Conference3rd International ECCC Conference, ECCC 2014
    Abbreviated titleECCC 2014


    • stress relaxation
    • modelling


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