High Temperature, Low Cycle Fatigue Characterization of P91 Weld and Heat Affected Zone Material

2014 ◽  
Vol 136 (2) ◽  
Author(s):  
T. P. Farragher ◽  
S. Scully ◽  
N. P. O'Dowd ◽  
C. J. Hyde ◽  
S. B. Leen

The high temperature low cycle fatigue behavior of P91 weld metal (WM) and weld joints (cross-weld) is presented. Strain-controlled tests have been carried out at 400 °C and 500 °C. The cyclic behavior of the weld material (WM) and cross-weld (CW) specimens are compared with previously published base material (BM) tests. The weld material is shown to give a significantly harder and stiffer stress–strain response than both the base material and the cross-weld material. The cross-weld tests exhibited a cyclic stress–strain response, which was similar to that of the base material. All specimen types exhibited cyclic softening but the degree of softening exhibited by the cross-weld specimens was lower than that of the base material and all-weld tests. Finite element models of the base metal, weld metal and cross-weld test specimens are developed and employed for identification of the cyclic viscoplasticity material parameters. Heat affected zone (HAZ) cracking was observed for the cross-weld tests.

Author(s):  
T. P. Farragher ◽  
S. Scully ◽  
N. P. O’Dowd ◽  
S. B. Leen

The high temperature low cycle fatigue behaviour of P91 weld metal (WM) and weld joints (cross-weld) is presented. Strain-controlled tests have been carried out at 400 °C and 500 °C. The cyclic behaviour of the weld material (WM) and cross-weld (CW) specimens are compared with previously published base material (BM) tests. The weld material is shown to give a significantly harder and stiffer stress-strain response than both the base material and the cross-weld material. The cross-weld tests exhibited a cyclic stress-strain response which was similar to that of the base material. All specimen types exhibited cyclic softening but the rate of softening exhibited by the CW specimens was lower than that of the base and all-weld tests. Finite element models of the base metal, weld metal and CW test specimens are developed and employed for identification of the cyclic viscoplasticity material parameters. HAZ cracking was the primary mode of failure for the cross-weld tests.


Author(s):  
S. B. Leen ◽  
M. Li ◽  
R. A. Barrett ◽  
S. Scully ◽  
D. Joyce ◽  
...  

This paper presents a study on high temperature cyclic plasticity of a welded P91 T-joint under cyclic internal pressure, in the context of high temperature low cycle fatigue (HTLCF) performance of such connections. In the present work, attention is focused on the development of a multi-material model for high temperature cyclic plasticity, including the effects of the different weld-related material zones, namely, parent metal, weld metal and heat-affected zone. The cyclic plasticity behaviour of the three zones is identified from previously-published high temperature, low cycle fatigue test results on uniaxial test specimens, including parent metal, weld metal and cross-weld specimens, obtained from a specially fabricated pipe girth weld, using ex-service P91 material. The cyclic plasticity material model includes the effects of kinematic hardening and cyclic softening. A three-dimensional finite element model of the welded T-joint is developed, incorporating the three sets of identified cyclic plasticity constants. The study is limited to isothermal conditions of 500°C, with a view to understanding the complex effects of multiple material zones with inhomogeneous cyclic plasticity behaviour. The heat affected zone is shown to play a key role in the development of plastic strains and localised stresses. The particular T-joint geometry is the subject of an investigation due to premature failure in a combined cycle gas turbine plant.


2019 ◽  
Vol 287 ◽  
pp. 02002
Author(s):  
Marina Franulovic ◽  
Kristina Markovic ◽  
Zdravko Herceg

Gears are mechanical components which experience high dynamic loading during their exploitation period. Therefore, their load carrying capacity together with life expectancy are often the main research interest in various studies. The research presented in this paper is focused on the materials response in spur gears tooth root, with the attention given to the repeated overloads during gears operation. In order to simulate low cycle fatigue by using numerical modeling of stress - strain relationship within material, the material model which takes into account isotropic and kinematic hardening is used here. Material response of specimens produced out of steel 42CrMo4 in different loading conditions is used for the calibration of material model, which is then applied to simulate damage initiation and materials stress - strain response in gears tooth root. The results show that materials response to the given loading conditions non-linearly change through the loading cycles.


2008 ◽  
Vol 30 (3) ◽  
pp. 538-546 ◽  
Author(s):  
G.V. Prasad Reddy ◽  
R. Sandhya ◽  
M. Valsan ◽  
K. Bhanu Sankara Rao

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