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What’s New

Marc 2020Presented by: Matthew Kokaly, Product Manager and Bhoomi Gadhia, Product Marketing Manager

July 22nd, 2020

We will start momentarily…


What’s New

Marc 2020Presented by: Matthew Kokaly, Product Manager and Bhoomi Gadhia, Product Marketing Manager

July 22nd, 2020


MARC 2020 Contents:

• New and Expanded Workflows

• Elastomer Fatigue Life Calculation

• Creep Material Data Fitting

• Induction Heating Improvements

• Co-Simulation Compatibility

• Smarter Solve

• Contact Enhancements

• Iterative Solver GPU Support

• Analysis Statistics Reporting

• Smarter Simulation Environment

• Model Dimension

• Ease of Use Enhancements


New and Expanded Workflows


Elastomer Fatigue Life Calculation

• Prior to this release, Marc built-in capabilities for modeling damage in rubber components were limited to the Mullins effect

• Mullins Effect – Degrading behavior until a stabilized cycle is reached (Miehe, Ogden-Roxburgh)

• There has been a large number of requests for fatigue damage modeling

• In response, we have developed an elastomer fatigue capability

• Experimental life curves for uniaxial tension and torsion tests are entered as a table or represented via a Wohler curve

• Supports constant amplitude, block or rainflow counting of an actual load history

• Fully compatible with adaptive remeshing (mapped to original mesh)

• Damage accumulation for variable amplitude via Palmgren-Miner rule:

Images and Chart from: WIT Transactions on The Built

Environment, Vol 97, www.witpress.com, ISSN 1743-3509

(on-line) High Performance Structures and Materials IV

285doi:10.2495/HPSM080301

𝑁𝑓 = 𝐴 𝜀𝑝,𝑚𝑎𝑥𝑛

𝐷 =𝑛1𝑁1𝑓

+𝑛2𝑁2𝑓

+𝑛3𝑁3𝑓

+⋯ ≤ 1

Simulation uses Maximum Principal Green-Lagrange

Strain or Maximum Principle Logarithmic Strain


Marc Solution: Elastomer Fatigue Life Calculation

Only visible if there is a material with

fatigue properties in the model

Options which are not

applicable are hidden

• As mentioned before, user must

request Principal Values of Logarithmic

Strain

• Added New Output For:

• Number of Cycles to Failure;

Log10(Number of Cycles to

Failure)

• Fatigue Damage

• Fatigue Life; Log10(Fatigue Life)

Fatigue Parameters Job Definition Fatigue Loading Fatigue Output


Marc Solution: Elastomer Fatigue Life Calculation Examples

Engine Mount with Axial and Radial Loading

Test Specimen Modeled with Axisymmetric


Creep Simulation

• Marc has multiple methods of defining the creep behavior including Maxwell creep (spring and dashpot in series)

• Marc uses the following equation to define the Maxwell creep behavior:

ሶ𝜀𝑐 = 𝐴𝑓 𝜎 𝑔 𝜀𝑐 ℎ 𝑇 𝑘′ 𝑡

• Stress dependence, 𝑓 𝜎 may be in the form of a power, exponential or hyperbolic law

• Creep Strain dependence is generally defined by: 𝑔 𝜀𝑐 = 𝜀𝑐𝑛, 𝑛 is a material constant ≥ 0

• Temperature dependence is generally defined as either:

ℎ 𝑇 = 𝑇𝑝, 𝑝 is a material constant ≥ 0 or

ℎ 𝑇 = 𝑒−𝑄

𝑅𝑇, Q is activation energy, R is universal gas constant

• Time dependence is generally defined by: 𝑘 𝑡 = 𝑡𝑞, 𝑞 is a material constant ≥ 1

• These parameters are usually determined from extensive testing and manual fitting

• Obtaining the associated material parameters can be a significant endeavor and subject to manual error during calculation


Marc Solution: Creep Experimental Data Fitting

• Added creep option for experimental data fitting capability in Mentat

• Significantly decreases the user effort required and improves robustness

• Process:

Prepare ragged table of

experimental data and define

the independent variable types


Marc Solution: Creep Experimental Data Fitting Example

2219 Aluminum at s = 130 MPa at Temp= 458, 438, 418K 2219 Aluminum at Temp=418 K and s = 170,150 and 130 MPa


Electomagnetics (E-M) Simulation in Manufacturing

• Marc has primarily focused on electromagnetic heating using induction coils

• The refinement of this application has continued in the Marc 2020 release

• In earlier releases, for 3-D we required a body of revolution be used for the coil shape. We have expanded the capability to now include arbitrary coil shapes

• The method used to determine the induced current was time intensive in simulations with 3-D models and/or nonlinear behavior. We have improved the speed by reformulating the calculation.


Marc Solution: Arbitrary Coil Shapes and Efficient Calculation of Induced Current

• To define an arbitrary coil, you assign the two terminal at the ends of the coil

• The new, more efficient calculation of the induction current has also been added as the new default.


Marc Solution: Arbitrary Coil Shapes and Efficient Calculation of Induced Current Examples

Part # of elements

Copper 21480 (hex8)

Air 177390 (tet4)

Plate 23040 (plate)

• 3-D example:

• Performance Improvement (Axisymmetric shown)

Marc 2019

FP1

Marc

2020Reduction

# of cycles 401 120 70%


Co-Simulation Across Multiple Domains

• Some problems require parallel use of domain specific tools to achieve the accuracy desired

• These include:

• Structural Mechanics

• Multi-Body Dynamics

• Computational Fluid Dynamics

• Etc.

• Prior focus for MSC Co-Sim:

• coupling two simulations

• Cutbacks isolated to one application

• Focus for upcoming release:

• Three-way coupling of simulations

• Cutback result in re-solving of new time step in all simulations in case of convergence issues


MSC Co-Sim Solution Example

Seismic Fragility Assessment of Steel Liquid Storage Tanks -

Scientif ic Figure on ResearchGate. Available from:

https://www.researchgate.net/figure/Elephants-Foot-Buckling-

failure-mode_fig1_301450886 [accessed 11 May, 2020]


Smarter Solve


Segment-to-Segment Stress-Free Initial Contact

• It is not uncommon that geometry or meshing results in small, unintended gaps

• To compensate and close these artificial gaps, Marc has a stress-free initial contact adjustment

• Previous algorithm used for Segment-to-Segment Stress-Free projection:

• did not allow the user to observe the magnitude and location of the adjustment

• adjustment was lost when subjected to large scale sliding.

• Node-to-segment stress-free initial contact did not have these issues.


Reformulated Segment-to-Segment Stress Free Projection

• In Marc 2020, stress-free initial contact for segment-to-segment contact was enhanced:

• Nodes are projected (like for the node-to-segment algorithm),

• Resulting polyline/polygon offsets are computed (generally small)

• This allows for the adjustment to be visualized and retained during large scale sliding of segment-to-segment contact

• This is the new default!


Linear Contact Formulation Added

• In some cases, a Marc user may want to prescribe contact similar to the Nastran “linear contact” capability

• This capability can be more efficient with minimal effect on accuracy provided the following assumptions:

• Contact throughout the simulation can be described by the initial configuration (no new nodes or patches come into contact)

• Sliding is small and does not result in nodes/patches changing the segment they contact

• Common scenarios include :

• Aerospace applications involving small strain “inertia relief” analyses

• Contact with infinitesimal displacements and rotations, e.g. engine block analysis

• Preloaded bolted joints subjected to primarily shear loading.

Similar Results

16% Less time

Confidential Model

Large areas in contact, stacks bolted together

Wall Time Reduction of 80% Similar results


Inefficiencies in Solution Convergence with Node to Segment

• Current iteration process for an increment with node to segment contact:

• Contact separation check at nodes are checked for contact after error criteria is satisfied.

• Potentially, separation check done in an earlier iteration may show that the iteration would need to be restarted due to contact changes

Iteration 1 Error =25%

Iteration 2 Error =16%

Iteration 3 Error = 8%




Iteration 7 Error =0.3456% Criteria met

Separation Check shows change in contact

Reset Iteration count to 1 and continue iterating

Time of actual

separation changes


A More Efficient Solution for Contact Checks in Node to Segment

• In Marc 2020, the Accelerated Check forces Marc to check for separation if the maximum residual force becomes less than 10% of the maximum reaction force

• This will force recycling of an iteration if the contact condition changes and residual force error is under 10%

• This is not a default behavior, to turn it on you must select the “accelerated” option for the check

• A significant savings in the number of iterations required and hence wall runtime is possible

Default:

137 iterations

Accelerated:

83 iterations


More Efficient Method for Contact Nodal Projection

Wall Time Reduction of 18%

Similar results

Wall Time Reduction of 45%

Similar results

Confidential Model #1

24 less iterations, 1 less cutback



3 less iterations



15 less iterations



18 less iterations



GPU and Performance

• GPUs can be used to accelerate the performance in some simulations

• Typically involve minimal I/O to and from the GPU

• Result in massively parallel computations within the GPU core

• In previous Marc versions, GPU support was limited to the Multi-frontal direct solver (Solver 8)

• Recent evaluations showed that a GPU could be used effectively on larger (>500K) models using an iterative solver By HanyNAR - Own work, CC0, https://commons.wikimedia.org/w/index.php?curid=89062959


Iterative Solver GPU Performance

• In Marc 2020, the Iterative Sparse solver (Marc Solver 2) now supports GPU calculations

• The default tolerance for the Sparse Iterative Solver has been changed from 10−3 to 10−4

Model Available Details Matrix Solution

Speedup

Walltime Speedup

Model 1 570k Nodes, 360k Elements (Tetra10) 6.7 3.5

Model 2 718k Nodes, 452k Elements (Hex8, Tetra10) 1.6 1.5

Model 3484K Nodes, 406K Elements (Hex8, Penta6),

Transformation, Multiple Materials 1.7 1.4

Model 41806K Nodes, 849K Elements (Tetra4), RBE2,

Elastic-plastic5.6 2.6

Model 5960K Nodes, 920K Elements (Hexa8), Element

deactivation, RBE2, Elastic-Plastic3.2 1.1

Model 6

1494k Nodes, 1620K Elements (Tetra4, Tetra10,

Hexa8),RBE2, Servo links, transformation,

temperature

1.5 1.5

Model 6

Model 3


Analysis Statistics Reporting

• The existing Marc Job Monitor provides basic feedback on the convergence progress of a running job

• There is a significant amount of additional useful information not shown that would be helpful to the user to see within the job monitor


Additional Data in Analysis Statistics Reporting

• Two additional runtime data of value:

• In a contact analysis, the Iterative Penetration Check Procedure (to avoid penetration of contact bodies) may cause scaling of the iterative displacement vector and introduce extra Newton-Raphson iterations

• The number of warning messages printed in the output file; the user would not know about it unless the output file would be opened to search for them

• In Marc Mentat 2020, both the Total Number of Warning Messages and the Fraction of the Increment Completed can be monitored

If this goes to 1 slowly, the

load increments may be

large, or the contact

tolerance may be small

Number of warning

messages throughout

the Marc output file


Smarter Simulation Environment


Mentat Model Dimension Confusion

• In previous releases of Mentat, no distinction in the interface was made in the dimensionality of the model and the relevant model definitions

• This resulted in confusion as menus were defined in context of 3-D regardless of the intended model dimension

Same 6 DOF menu

regardless of 3-D, Axisymmetric or 2-D Analysis


Mentat is Now Context Sensitive for Model Dimensionality

• User sets Model Dimensionality

• Menus are now context sensitive in terms of dimension chosen

• If a user switches between dimensions, menus will change and existing data moved to appropriate value


Other Mentat Examples of Dimension Based Context Sensitive

• Bolt Control Node Boundary Condition no longer requires you to specify a DOF

• Definition of Geometric Contact Bodies (Curves for 2-D, Surfaces for 3-D)

• Orthotropic and Anisotropic Material Properties

• Servo Links between different DOF

A Total of 106 Menus were adjusted


Large Scale Changes to Tables

• Tables are extremely powerful but it can be challenging to modify large sections of a table

• We have added two new options to make it easier:

• Subdividing Segments and Reducing Data Points can now be either done by modifying the existing table or by optionally creating a new table

• A new option has been added to remove a range of data points

Initial Table New Tables


Predefined Commonly Used Table Shapes

• Predefined Table Shapes• Linear Ramp

• Linear Ramp up and down

• Linear Ramp to Constant Value

• Smooth Ramp to Constant Value

• Constant Value

• Triangular

• Periodic Step

• The independent Variable is Time or Normalized Time

• The default name of the table is automatically related to its shape

• When using Data Points, the Extrapolation Flag is switched off


Efficient Navigation of Increments Using Time

• During Post Processing, a new option called Skip To Timehas been added:

• Will skip to the increment with the time nearest to the user specified time

• Can e.g. be useful if images at know time stations will be created using procedure files, cutbacks occur or automatic time stepping is used

Before Marc 2020, Results File Increment Menu

or Forward/Back buttons to find 1.20 sMarc 2020 Skip to Time directly to 1.20s


Improved Rendering of Solids

• Parasolid Bodies can be rendered with more accuracy resulting in improved images

Before After


Default Names for Copies Prior to Marc 2020


Default Names for Copies in Marc 2020


Appropriate Default for a Nonlinear Simulation Tool

• When creating a new Job (with a structural pass), the Large Strain option is switched on by default

Prior to Marc 2020 Change in Marc 2020

Note location

change as well


Miscellaneous Ease of Use Enhancements

➢ Parasolid Bodies:

• Clear distinction between 3-D Solids, Sheet and Wire Bodies

• A Quad Sheet Body can now be defined in the global 3-D space (instead of limited to the local XY-plane), similar to the NURBS based Quad Surface


Thank You

Documents

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