Continuum damage mechanics modelling incorporating stress triaxiality effect on ductile damage initiation

2020 ◽  
Vol 43 (8) ◽  
pp. 1755-1768 ◽  
Author(s):  
Nicola Bonora ◽  
Gabriel Testa ◽  
Andrew Ruggiero ◽  
Gianluca Iannitti ◽  
Domenico Gentile
Keyword(s):  
Damage Mechanics ◽  
Stress Triaxiality ◽  
Continuum Damage Mechanics ◽  
Ductile Damage ◽  
Continuum Damage ◽  
Damage Initiation

Continuum damage mechanics predictions of creep damage initiation and growth in ferritic steel weldments in a medium bore branched pipe under constant pressure at 590 °C using a five-material weld model

2005 ◽  
Vol 461 (2060) ◽  
pp. 2303-2326 ◽  
Author(s):  
D.R Hayhurst ◽  
R.J Hayhurst ◽  
F Vakili-Tahami
Keyword(s):  
Heat Affected Zone ◽  
Ferritic Steel ◽  
Damage Mechanics ◽  
Constant Pressure ◽  
Creep Damage ◽  
Continuum Damage Mechanics ◽  
Coarse Grained ◽  
Continuum Damage ◽  
Damage Initiation ◽  
Type Iv

The paper reports three-dimensional creep continuum damage mechanics (CDM) analyses of creep failure in a medium bore Cr–Mo–V low alloy ferritic steel welded branched-pressure vessel that has been tested under a constant pressure of 4 MPa, at a uniform temperature of 590 °C. The use of the CDM computer software Damage XXX to analyse the initiation and growth of creep damage and subsequent failure in the branch weld is reported for a five-material model that includes: parent, Type IV, refined heat affected zone (R-HAZ), coarse grained heat affected zone (CG-HAZ) and weld materials. The results of the analyses are presented for two cases: the first without the CG-HAZ; and, the second with the CG-HAZ included. For both cases, lifetimes are conservatively, yet accurately predicted. It is shown that it is necessary to use a Type IV thickness of 0.7 mm to accurately predict the failure location and mode. The results of metallographic examinations of a tested vessel and the predicted damage fields are in close accord. Failure is predicted to take place, by steam leakage, from the interior of the vessel, through the Type IV zone adjacent to the main pipe, connecting through the R-HAZ to the CG-HAZ, where leakage takes place at the weld toe in the crotch plane.

Ductile Damage Assessment Using Continuum Damage Mechanics and Methodology for High Strain-Rate Damage Analysis

2017 ◽  
Author(s):  
Alexander Sancho ◽  
Paul A. Hooper ◽  
Catrin M. Davies
Keyword(s):  
Plastic Deformation ◽  
High Strain Rate ◽  
Strain Rate ◽  
Damage Assessment ◽  
Damage Mechanics ◽  
High Strain ◽  
Continuum Damage Mechanics ◽  
Ductile Damage ◽  
Continuum Damage ◽  
Static Conditions

The interest of this research is to assess the experimental techniques used for ductile damage measurement both in quasistatic and high strain-rate conditions. The results can later be used for the calibration of Continuum Damage Mechanics (CDM) models. A procedure for the evaluation of damage accumulation in quasi-static conditions is presented. The technique used to measure damage is based on the elastic modulus calculation from unloading and reloading cycles performed at different stages of plastic deformation. Tests have been performed in a continuous manner and the strain variations have been recorded using a small gauge extensometer. This methodology includes a second experiment in which the geometry of the specimen is monitored, allowing to extract the true stress-strain behaviour of the material even after necking phenomenon starts. The proposed methodology has been applied to stainless steel 304L. Regarding the high strain-rate conditions, a continuous test cannot be performed due to physical as well as practical difficulties. Therefore, an interrupted methodology has been devised in which the plastic deformation is applied at high strain-rate and the damage measurement is performed separately in quasi-static conditions. An experimental rig has been developed to interrupt high-speed tensile tests at strain-rates up to 103s−1. Its design and preliminary calibration are analysed and its future use for damage assessment discussed.

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