SYSWELD Complete Finite Element Solution for Simulation of Welding Processes Josef Tejc MECAS ESI s.r.o., CZ
Company introduction Uslavska 10, Pilsen Czech Republic e-mail: info@mecasesi.cz web-page: http://www.mecasesi.cz
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SYSWELD 2003
SYSWELD background SYSWELD is a part of the SYSWORLD Finite Element program family:
SYSWELD background SYSTUS is a general purpose Finite Element product that provides most of the computation capabilities that can be handled with implicit Finite Element technology. Developed through the last 4 decades and born in the Nuclear Industry, it provides excellent non-linear computation capabilities. Most of the features developed for SYSTUS are shared through the SYSWORLD product family, i.e. it is possible to use them in SYSWELD too.
General capabilities SYSWELD 2003 simulates all physical effects that are related to: Welding and Heat treatment Courtesy GM
Architecture of the code
Coupled thermo-metallurgical analysis Modified heat convection equation: i T Pi (ρ C) i Pi i T + Lij ij = t λ i i< j P... phase proportion T... temperatur e t... time i, j... phase indexes L ( T )... latent heat A ij ij... proportion of i j ρ... mass density C... specific heat λ... thermal Q... heat transforma tion of phase i transforme d to sources j in ( T ) A Q conductivi ty time unit
Non-linear computations SYSWELD covers 50 men years of solver development SYSWELD performs non-linear computations with all material properties depending on Temperature Phases / material transformations Proportion of chemical elements Auxiliary variables
Non-linear computations SYSWELD covers all needed nonlinear phenomena Non-linear heat transfer to any extent Non-linear geometry including large strains Isotropic and kinematic strain hardening including phase transformations Transformation plasticity Non-linear mixture rules for the yield stress of phases
Typical applications MIG (metal inert gas) welding WIG / TIG welding Laser welding Electron beam welding Spot welding Friction welding
Main results of a welding simulation Temperature field and gradient Phase proportions Hardness Distortions Residual stresses Plastic strains Yield stress depending on the mixture of metallurgical phases
Simple Example of Welding Simulation Arc Welding of Steel Plate
Part and process data Plate thickness: Plate length: Arc welding Welding Speed: 9mm 120mm 5 mm/s Butt weld with filler material Made of S355_J2G3 construction steel
Formulation of the Problem and Related Input Data
Mesh of the structure
Material properties Thermal properties: Thermal conductivity Specific heat / Enthalpy Mass density Usually, the properties are defined as a function of temperature and metallurgical phases
Density ρ [kg mm -3 ] Austenite Ferrite, Bainite, Martensite T [ C]
Material properties Metallurgical properties = phase transformation kinetics for: Austenitic transformation during heating (TTA diagram) Transformation to Ferrite, Bainite and Martensite during cooling => CCT diagram
Real CCT diagram T [ C] t [s]
Models for phase transformations Leblond s model dp dt. = f T. P eq ( T ) τ ( T ) P P... phase proportion P eq... proportion at phase t... time T... temperature T&... heating/co oling rate equilibriu m for diffusion controlled transformation Koistinen-Marburger law P(T) = 1 exp( b(ms T) ) P... phase for Martensitic transformation proportion b... law coefficien t Ms... Martensite - start temperatur e
Model of the CCT diagram T [ C] Ferrite Bainite Martensite t [s]
Material properties Mechanical properties: Young s modulus Poisson s ratio Thermal strain Yield stress Strain hardening Usually, mechanical properties are defined as a function of temperature and phase proportions
Yield stress σ Y [MPa] Martensite Ferrite Bainite Austenite T [ C]
Model of heat source Double-ellipsoid heat source Heat transfer into the structure (t=20 s)
Clamping conditions Symmetry conditions
Computed Thermometallurgical Results
Temperature field at t=20s
Temperature evolution (movie)
Austenite evolution (movie)
Bainite evolution (movie)
Computed Mechanical Results
Evolution of displacements (movie)
Displacements UZ (with phase transf.) Angular distortion -1.1mm -0.5mm z
Displacements UZ (without phase transf.) Angular distortion -0.5mm -1.1mm -1.4mm z Attention: Different scaling!
Stress σ yy (with phase transf.) y Reduced tensile stress level due to phase transformations
Stress σ yy (without phase transf.) y
Stress σ xx (with phase transf.) x
Stress σ xx (without phase transf.) x
Summary The difference in computed distortions with and without phase transformations is about 30% The difference in computed stresses with and without material transformations is remarkable
Example of an Industrial Application Simulation of Welding of a T-joint Made from AlMgSi
Courtesy of
Process movie (accelerated display)
Description of the task A rectangular hollow profile is welded with 4 joints on a thin-walled plate The computation of distortions during and after welding is extremely sensitive due to general instability of the arrangement The edges of the plate are free The plate is thin-walled and has a low resistance against bending The welding joints influence each other To a certain extent, this is the worst case for simulation engineering
Evolution of the temperature field (accelerated, scaling from 200 C to 650 C)
Displacement UZ after weld 1 (t=5.2s) Positive buckle at the edge parallel to WELD 1 Z
Displacement UZ after weld 2 (t=11.3s) Positive buckles at the edges parallel to WELD1 and WELD2 Z
Displacement UZ after weld 3 (t=17.4s) Positive buckles at the edges parallel to WELD1, WELD2 and WELD3 Z
Displacements UZ after weld 4 (t= 22.10s) Still a positive buckle at the edge parallel to WELD1. However, the contraction of WELD4 decreases the positive buckle of WELD1 and WELD2. Z
Cooling from 22 to 1000 s (movie)
Cooling from 22 to 1000 s (movie) Different scaling!
Process movie - evolution of distortions at the edge parallel to WELD 2
Interpretation of results The computed evolution of the distortions of the edge parallel to WELD2 is nearly coincident with the displacements shown in the process movie The final displacements have been measured to around 6mm The final displacements computed are around 6mm The computed displacements correlate well with the experiment
Some of the New Features of SYSWELD 2003
Interfaces PAM-STAMP/SYSWELD In SYSWELD 2003, it is possible to read and write PAM-STAMP mapping files, in order to: Import results from a stamping simulation in a welding simulation Import results from a welding simulation in a stamping simulation A typical application is the stamping of welded tailored blanks
Door panel - real images fehlerfrei umgeformtes Bauteil Courtesy of AUDI
Interfaces PAM-STAMP/SYSWELD Plastic strains: Min/Max : 0/0.587 Courtesy of AUDI
Welding Assembly simulation During the last 4 years, ESI software has validated with Industrial partners a new methodology to simulate welding assembly - the local/global approach The Welding joints are computed outside the global structure in different local models for which all physical phenomena are simulated Then, the assembly effects in term of global distortions are computed after projection of local models results on the global structure This methodology presents the advantage to allow the simulation of large parts supported by shell-solid models A simplified method is also available to analyse the influence of the sequence effects and the clamping tools on the distortions of assembly
Welding Assembly simulation
Material database V2003 contains an intensively tested standard material database for Welding and Heat Treatment heat_treatment.mat welding.mat The standard databases will be updated continuously An enhanced material database is also available
Material database For Welding, the following materials are available AlMgSi Typical automotive aluminium alloy S355J2G3 (1.0570, St 52-3, Fe 510 D1, Fe 510 D1 FF, CSN 11 523) Typical ship building steel X20CrNi13 (1.4201, Z20C13, AISI 420, CSN 17 022) Stainless steel X5CrNi 18 10 (1.4301, Z7CN18-09, AISI 304, CSN 17 240) Stainless steel DC04 (St 14, St 4, AISI 1008, CSN 11 325) Typical car body / stamping steel, deep drawing quality
s solution of present days SYSWELD: Complete solution for realistic simulation of welding processes Process COMPARISON WITH EXPERIMENTS: In cooperation with industrial partners a number of experimental projects was done to proof tight agreement between results of simulation and reality. Product
s solution of near future Complete manufacturing chain simulation perfectly reflecting the reality Stamping Casting Welding / Joining Structural behavior Fatigue strength Crash