FEA-plattform för realistisk modellering av WPS och dess inverkan på den strukturella integriteten

Transcription

1 GEOMETRY MATERIAL VALIDATION WELD PROCESS FEA-plattform för realistisk modellering av WPS och dess inverkan på den strukturella integriteten Per Lindström, industridoktorand, IWE, teknologie licentiat Huvudhandledare: professor Lars-Erik Svensson Handledare: professor Lennart Josefson (Chalmers)

2 Introduction The project started around year 2000 (few years after the M/S Estonia, M/S MSC Carla and M/S Erika disasters) in order to satisfy my demand of a tool to be used at assessment of in-service repair welding projects Computational Welding Mechanics CWM CWM Platform in current use by DNV GL Materials Laboratory The CWM platform is used to predict realistic displacements, strains and stresses Large strain theory Strains at welding o Thermal γ γ o o Plastic Elastic γ 5 grains µm γ 2

3 Improved platform - thermo-mechanical staggered coupled approach 3

4 2D CWM versus IIW Round Robin macropicture 4

5 3D- and 2D CWM versus neutron diffraction measurements 5

6 3D- and 2D CWM versus yield strength profile 6

7 Fracture mechanics study The crack driving force (CTOD CDF ) for a ductility dip crack (DDC) hot crack in ER316LSi weld metal is studied, DDC is created at % of T S. 7

8 Design crack vs. Room temp. crack and DDC CTOD mat CTOD PWHT 8

9 LS-Dyna weld head model 9

10 3D Weld heat source model The 3D weld heat power is distributed by a double ellipsoidal Goldak weld heat source Q Φ3D = Q Φ3Df + Q Φ3Dr Q Φ3Df = 6 3f 3x fp 2 w abc 1 π π e a 2 e 3y2 b 2 e 3(z+vt)2 c 2 1 Q Φ3Dr = 6 3f 3x ap 2 w abc 2 π π e a 2 e 3y2 b 2 e 3(z+vt)2 c 2 2 f f + f r = 2 10

11 Improved 2D Weld heat source model Gaussian distribution of the 2D weld heat flux Weld heat flux distribution in the xy-plane as a function of the time 11

12 Improved 2D Weld heat flux density load curve 1. The equivalent 2D weld heat flux (PL-Q Φ2D ) facilitates a more detailed and physical correct modelling of the thermal transients compared to previous methods 2. The resultant weld heat flux in the cross section plane is analysed by 3D CWM 3. The PL-Q Φ2D load curve is created by scaling of the resultant 3D weld heat flux in relation to the 2D weld heat energy 12

13 Improved weld filler material s initiation temperature 13

14 Plastic hardening modulus (h) - Plastic strain based 14

15 Acknowledgement The financial support and the support in the form of material and services from the following organisations is acknowledged: DNV GL KK-stiftelsen (SiCoMaP) Dynamore Nordic AB and LSTC Forsmark Kraftgrupp AB Outokumpu Stainless AB Sheffield Fracture Mechanics Håkan Nilsson Consulting & Maskinteknik i Kil AB Westinghouse Electric Sweden AB SSAB Oxelösund ESAB Lincoln Electric 15

16 EXTRA MATERIAL TO BE USED IN CASE OF DISCUSSION 16

17 Secant versus Tangent 17

18 316LNSPH 18

19 Improved CWM platform Novel 64 Core CWM HPC Nonlinear implicit FE-solver - MPI solver Quasi dynamic transient nonlinear thermo-mechanical staggered coupled FEA approach Large strain theory (Conservative) - 1st Order element formulation Realistic 3D weld head manipulation of the Goldak weld heat source Novel elastic-plastic CWM material model with residual stress release function at the solution annealing temperature Improved 2D weld heat source Improved 2D weld heat flux model Novel fully 3D nonlinear fracture mechanics FEA γ γ γ γ 5 grains µm 19

20 Large strain theory ε true > 15 % (SSM 2009:16) 1 st Order selective reduced element formulation 20

21 Material models Strain hardening and WRS are released at a specified temperature The base and weld material can only retain and build up WRS at temperatures below the WRS release temperature Weld material to be activated in a later sequence of a multi-pass weld simulation, so called quiet material, is also described by the material models 21

22 Residual stress release 22

23 Plastic strain based h v.s. Elastic strain based h This small value of tangent modulus is used to avoid convergence issues during the numerical analysis Bhatti, A.C., Barsoum, Z.A.B, Murakawa, H.C., Barsoum, I.,2015, Influence of thermomechanical material properties of different steel grades on welding residual stresses and angular distortion, Materials and Design 65 (2015), pp