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Abaqus Welding Analysis Presented by: Philip Williams ([email protected]) SIMULIA Roadshow 21st and 22nd July 2015

Copyright © 2015 Simutech Solution Corp. All Rights Reserved.

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Overview • Introduction • Adding Weld Material • Multi-Physics Capabilities • Material Properties With Temperature • The Abaqus Welding Interface (AWI) • Methodology • Using AWI Tool


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Welding Analysis in Abaqus

• Join sections together at high temperature during an analysis • Add material during analysis • Interaction between temperature and stress/displacement • Temperature dependent properties

• Assess the residual stresses and distortion of the model


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Adding Weld Material • In Abaqus, we cannot create elements during an analysis • Define all elements in initial model • Remove using *model change, remove • Add back in when required using *model change, add

Initial Model

*Model Change, Remove

Pass 1

Pass 2

Pass 3

Pass 4

Pass 5

Pass 6


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Adding Weld Material • Simulate a continuous procedure • Separate weld into smaller chunks – progressively add chunks over several steps • Gets confusing as model gets bigger • Use the AWI plug-in to help set up model

• Lay down a complete pass in one step • Use subroutines to update material properties and loading conditions as function of time or position • Material properties (UFIELD or USDFLD) • Moving heat flux to represent moving torch (DFLUX) • Film coefficients (FILM) • Conduction of heat between weld and base materials (GAPCON) • Defining subroutine is more advanced • Requires Fortran programming Copyright © 2015 Simutech Solution Corp. All Rights Reserved.

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Multi-Physics Capabilities Sequentially coupled thermal-stress analysis

• Temperature fields are calculated first and read into stress analysis • Thermal analysis not affected by displacements

Fully-coupled thermal-stress analysis

• Temperatures and stresses calculated simultaneously • Thermal analysis can be affected by displacements

Coupled thermal-electrical analysis followed by stress analysis Fully-coupled thermal-electrical-stress analysis


• Electric potential and temperature fields solved simultaneously then temperatures read into stress analysis • Thermal-electrical analysis not affected by displacements

• Stress/displacement, electric potential and temperature fields solved simultaneously • Thermal-electrical analysis can be affected by displacements

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Multi-Physics Capabilities Multi-pass weld: Sequentially Coupled Thermal-Stress Analysis

Spot weld: Thermal-Electrical-Stress Analysis

Multi-pass Weld – Thermal-Structural Analysis

Kobayashi and Mihara, 2014

For this presentation we will consider sequentially-coupled thermal-stress analysis Copyright © 2015 Simutech Solution Corp. All Rights Reserved.

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Material Properties With Temperature • Accuracy depends on quality of material properties • May be temperature dependent • Thermal analysis • Conductivity • Specific heat • Stress analysis • Density • Elastic • Expansion • Plastic

• Anneal temperature • Latent heat Copyright © 2015 Simutech Solution Corp. All Rights Reserved.

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Material Properties – Anneal Temperature • Models effect of melting and resolidification • Above the anneal temperature: • Material loses hardening memory • Equivalent plastic strain drops to zero • Assumes perfectly plastic behaviour

• Requires Mises, Johnson-Cook or Hill plasticity Plastic strain

With Anneal temperature definition Without Anneal temperature definition Copyright © 2015 Simutech Solution Corp. All Rights Reserved.

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Material Properties – Anneal Temperature Plastic strain

With Anneal temperature definition: Reduction in plastic strain in region being heated Without Anneal temperature definition: Plastic strain is not reduced Copyright © 2015 Simutech Solution Corp. All Rights Reserved.

First pass completed. Heat base material and existing weld before start of next pass.

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Material Properties – Latent Heat • Large change in internal energy during phase change • Analysis becomes non-linear • Requires density definition • Define: • Latent heat per unit mass (mJ/tonne), • Solidus temperature, • Liquidus temperature

Temperature (°C)

With Latent Heat definition: As weld cools, it must change state from liquid to solid. This releases energy, and so the model cools more slowly.

Without Latent Heat definition: Model cools more quickly


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The Abaqus Welding Interface • The Abaqus Welding Interface (AWI) is a useful tool for setting up a welding analysis • Plug-In for Abaqus CAE • AWI Tree • Takes the user step by step through the process of defining weld chunks and passes • Tasks have to be done in order

• Colour-coding of beads, chunks and passes • Operate on thermal analysis model • Stress analysis model is created at end and is a copy of thermal analysis model


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AWI Methodology • Sequentially-coupled thermal-static analysis • Thermal analysis first • Read temperatures into stress analysis

• Weld beads are broken down into discrete chunks and added over several steps • Approximates the continuous flow over time

• Can consider multiple welds and multiple passes


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Methodology – Thermal Analysis

Remove welds • Step 1 • *Model change, remove

Simulate weld torch • Transient heat transfer step • Heat region to which chunk will be added • Base material and/or previously added weld material


Activate weld chunk • *Model change, add • Weld material initially at melting temperature • Film and radiation surfaces updated

Optional cooling • At the end of pass • Transient cooling or • Steady state heat transfer step cooling to constant temperature

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Methodology – Thermal Analysis • (video)

Single pass weld

Pipe weld with multiple passes

Multi-pass weld Copyright © 2015 Simutech Solution Corp. All Rights Reserved.

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Using AWI Tool Create or import CAE model Model creation Weld creation Pass controls assignment Pass creation Job control assignment Job creation Copyright © 2015 Simutech Solution Corp. All Rights Reserved.

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Using AWI Tool

– Create or import CAE model

• 3D or 2D planar model Create or import CAE model

• 3D welds ideally swept or extruded

Model creation

• Base material and welds must all be in one part

Weld creation Pass controls assignment Pass creation

• Nodes are shared between base material and weld

• Partition the part as required • Include partitions for individual beads and chunks if possible (welds can be defined using elements or geometry)

• Create and assign model and section properties. Job control assignment Job creation

• Weld material properties must be defined over a range of temperatures, including melt temperature and torch temperature

• Assemble and position the model as required • Create mesh on whole model and assign element types


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Using AWI Tool Create or import CAE model Model creation Weld creation Pass controls assignment

– Model creation

• Choose Abaqus model and part to use • Assign base material and section • Specify British or SI units (sets defaults for some parameters)

Pass creation Job control assignment Job creation


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Using AWI Tool

– Weld creation

• Assign weld temperature Create or import CAE model

• Assign regions of model to weld beads

Model creation

• Multiple welds can be defined (in same part)

Weld creation

• Each weld may have multiple beads

Pass controls assignment Pass creation Job control assignment Job creation


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Using AWI Tool

– Weld creation

For swept or extruded geometry: Create or import CAE model Model creation Weld creation Pass controls assignment Pass creation Job control assignment

• Cell extrusion • Pick cell face and specify number of cells in chunk

• Element extrusion by cell face • Pick cell face and specify number of elements in chunk

• Element extrusion by element face • Pick element faces for each bead and specify number of elements in chunk

Job creation

If geometry not swept, or weld not continuous: • Cell/Element picking • Pick individual cells/elements for each chunk


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Using AWI Tool

– Weld creation

• Colour-coding tool to identify beads and chunks Create or import CAE model

Use highlighting tool to show beads and chunks

Model creation Weld creation Pass controls assignment Pass creation Job control assignment Job creation


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Using AWI Tool

– Pass controls assignment

Create or import CAE model Model creation Weld creation Pass controls assignment Pass creation Job control assignment

• Apply Torch step Job creation

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Specify analysis controls

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Specify torch application ramp or ramp and hold


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Using AWI Tool

– Pass controls assignment

Create or import CAE model Model creation Weld creation Pass controls assignment Pass creation Job control assignment

• Film and radiation properties Job creation

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Surfaces for beads and base material are updated in each step

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Film properties applied to other surfaces remain constant


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Using AWI Tool Create or import CAE model Model creation Weld creation

– Pass creation

• A weld pass is a number of weld chunks being laid down in a step • Multiple beads or chunks from a single or multiple welds can be laid down in a single pass • For 2D models, a pass is one or more entire weld beads

• Assign weld beads to weld passes Pass controls assignment

• Manually pick cells or elements to select chunks

Pass creation

• Pass Manager

Job control assignment

• Once passes have been generated, we can add additional analysis steps as required

Job creation


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Using AWI Tool

– Pass creation

Pass Manager Create or import CAE model Model creation Weld creation Pass controls assignment Pass creation Job control assignment Job creation

Pass chunk selection Passmanager managerwith withautomatic individual chunkchunk selection selection by bead weld


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Using AWI Tool

– Job control assignment

• Specify job names Create or import CAE model Model creation

• Choose element types • Specify bead removal for stress model • Pass level

Weld creation Pass controls assignment Pass creation Job control assignment

• Elements stay in analysis with low stiffness until activated • Remove then activate elements in each pass

• Model level • All weld elements removed at start of stress analysis • Activate elements in each pass

Job creation


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Using AWI Tool – Job creation • Builds stress model Create or import CAE model Model creation Weld creation

• Defines steps for heat transfer model •

Model change definitions

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Thermal loads

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Film and radiation interactions

• Defines steps for stress model Pass controls assignment Pass creation Job control assignment

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Model change definitions

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Temperature field definitions from heat transfer analysis

• Further changes can be made to models •

For example: add boundary conditions to stress model

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These changes may be lost if the job creation is run again

Job creation


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Advantages Of Using AWI • Methodology requires: • Many steps to introduce weld gradually over time, with additional cooling steps • Each time a chunk is added, model requires definition of: • Separate element sets • 1 or 2 heating steps • 1 or 2 steps for model change • New film and radiation surfaces on weld and base material

• As the model gets larger, quickly becomes unmanageable • Manual definition is time-consuming and errorprone • Tasks are repetitive – ideally suited to plug-in


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Summary • Analyse welding process to get accurate prediction of residual stresses and distortion due to temperature gradients • There are options within Abaqus for: • Conducting multi-physics analyses • Adding material during an analysis • Including nonlinear, temperature dependent material properties

• The Abaqus Welding Interface (AWI) will guide you through the procedure, reduce the set-up time and automate many of the repetitive tasks


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