Abstract
Abstract Three-point bending specimen with fixed constraints (TPBSF) can be used to obtain uniaxial creep parameters from small samples of material. Conversion relationships between TPBSF and uniaxial creep data are based on the beam bending model. For large loads and longtime creep test, the specimen deformation can be large, which may be contrary to the small deformation assumption of the beam bending model. So it is necessary to define the critical deformation, below which the beam bending model holds. In this study, a new method to define this critical deformation was proposed by displacement. Based on the relationship between the maximum rotation angle and displacement at the elastic and creep stages, three procedures to determine the critical displacement were first proposed. Then it was verified by the creep test of P91 steel at 566 °C and 66 N. The results show that the critical displacement obtained by finite element method is in good agreement with the experimental result, and the maximum error is 4.5%. Creep parameters were regressed and compared with those in the literature on the basis of critical displacement, it can be seen that creep parameters regressed by the new proposed method are much closer to uniaxial creep than the literature, which indicates that beam bending model holds below this critical displacement. Finally, the finite element method was used to investigate the relationship between the time correction parameter and specimen geometric parameters. It can be found that the specimen width has little influence on the time correction parameter. However, the influence of specimen thickness and span can be significant.
Published Version
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