Category "Simulation"

2019 solver has number of enhancements that spans from fracture mechanics to element formulation to material formulation. Let’s start with what’s there on the fracture mechanics side:

Fracture mechanics enhancements

  • Introduction of new linear elastic fatigue crack growth procedure: Allows for change in contact conditions while loading, allows non-linear geometry behavior, mixed mode fatigue loading and viewer improvement. It is currently available for constant amplitude loading only. The input deck for mixed mode behavior looks as follows:
  • Improvements in contour integrals pre-processing and solving time. This applies to both J-integrals as well as K-integrals.
  • XFEM improvement to increase smoothness of 3D non-planar crack front. This is achieved by introducing non-local stress averaging algorithms to predict crack direction. Also limit new crack propagation direction to a certain angle from previous direction.
  • Symmetric cohesive elements have been introduced. Plane of symmetry must be perpendicular to one of the global axis though.
  • Introduction of UDMGINI subroutine to incorporate varied crack initiation criteria for different enrichment zones.

Element technology enhancements

  • Poro-elastic acoustic elements have been introduced to study wave propagation in coupled isotropic poro-elastic medium. It is only available in steady state dynamics analysis.
  • Displacement acoustics pressure elements have been introduced: C3D8A, C3D6A, C3D4A. Primary unknows are structural displacement and pore pressure. Same shape function used for displacement and pressure.
  • Shear panel element SHEAR4 in Abaqus has been introduced to model thin reinforced panels such as in fuselage. Intended to model response of buckled plate. Use is limited to linear elastic only.
  • Variable beam radius element formulation now available in Abaqus that can be well visualized in viewer as well.

Material enhancements

  • Low density foam has been introduced in Abaqus standard in 2019x FD01. This material has already been present in explicit. This material is useful in modeling highly compressible elastomeric foams.
  • Output variable SROCK for rock mechanics effective stress.
  • Enhancements to super-elastic materials to improve convergence and performance of material model. This application would be of interest in healthcare industry. An environment variable should be introduced to activate the model. Available from 2018x FD04.
  • Transverse shear stiffness modulus has been introduced for shell and beam sections. This now obviates the user material model to deal with plates of spatially varying thickness or plates made of composites.
  • Damage in concrete due to plasticity can now be modeled by defining failure criteria and element deletion criteria.
  • Two new outputs introduced in explicit for cohesive elements: equivalent nominal strain NEEQ and equivalent nominal strain rare NEEQR

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Contacts and Constraints

While we introduce new functionalities in Abaqus 2019 in contacts and constraints like we have done for other functionalities in similar blogs, I would retrospect into 2018 and clarify an important point: what’s the difference between FD and FP (hot fix). Believe it or not, they are not the same and the table below clarifies it for 2018 release.

Now let’s look at enhancements

  • One of the biggest enhancement in contact is that 2D and axisymmetric models are now supported in general contact for explicit. This general contact capability was already available in standard. This has been done on many customer requests in the past. Please note that 3DX platform does not support 2D axisymmetric models yet.
  • Another major enhancement is that analytical rigid surfaces are now supported in general contact for standard. This capability was already available in explicit general contact. Most common benefit of analytical rigid surface is precise geometrical data of simple surfaces.
  • Threaded interface approximation has undergone correction to include effects of right handed or left handed threads. This is an enhancement to existing capability in *clearance, bolt keyword entry. The image below shows the effect of thread direction on contact normal.

Further enhancements have been made to differentiate between one way and two-way threads. A two-way thread can resist both tension as well as compression unlike one way thread.

  • Another major enhancement is the introduction of general contact in pure heat transfer as well as coupled thermal-electrical step. Moreover, general contacts defined in any one of these steps can be carried forward and used in subsequent steps such as general static.
  • New Output Variable: CEDGEACTIVE: Dynamic feature edge criteria. It is now possible to visualize active feature edges at any stage of the simulation. This can be of great use in explicit analysis for applications such as air bag deployment.

CSLIPEQ: Relative equivalent tangential slip while in contact. It was present in explicit but now has been introduced in standard as well.

CSLIP_PL: Introduced to quantify plastic slip when shear stress exceeds critical frictional stress.

CICPS: Integral of contact pressure over the surface. It is different from CFN because normal direction is not considered.

Perhaps key differentiator is the situation below in which CFN output is zero due to symmetry but CICPS has a finite value.

  • Moment correction due to shell offset: When shell offset is defined, nodes shift from shell midplane and so does any forces acting on shell edge thereby creating a false moment about the midplane. This affect has been corrected by introducing a counter moment at the nodal force location so that effective location of edge force is at the shell midplane.
  • Deprecate old contact controls: Changes in certain contact controls by user will now result in fatal error by default. These controls are approach, automatic tolerances, Lagrange Multiplier etc. It has been observed that changes in such controls often results in performance degradation. In earlier releases only warning messages were issued that users have tendency to ignore. The default settings can be changed by the user.
  • Initial contact stress: The initial contact stress is now equal to stress of underlying elements instead of being zero. This now obviates the use of penetrations and sliding to generate contact stresses. The feature can be of much use in geotechnical applications.
  • FRIC_COEF enhancement: This subroutine has been enhanced to pass user defined, solution dependent state variables. Now coefficient of friction can be defined as a function of user defined state variable. GETVRC utility routine can be accessed from within FRIC_COEF to access various state variables to define friction coefficient.

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Do any of the questions below apply to your organization:

  • Do you own existing Dassault Systemes software products and are up to date with maintenance?
  • Do you need to transform your digital engineering processes?
  • Are you interested in implementing the true Digital Twin concept?
  • Is the technology that you are using for Digital Product Definition out of date?
  • Does your company have strategic initiatives like Lean Manufacturing, Flawless Launch, Model Based Engineering or similar?
  • Is your company expanding or looking to put new products on the market?

If the answer to any of these questions is Yes, then you should be looking at the Customer Transformation Program (CTP) from Dassault Systemes.

Dassault Systemes  launched a Customer Transformation Program for 2019 which is designed to transform the businesses of all their existing customers. This is a limited-time sales initiative program starting January 21, 2019 and ending December 31, 2019.

The program offers existing customers a voucher that makes them eligible for a discount on qualified new purchases of software from Dassault Systemes extensive range of productivity enhancing solutions. Customers can earn up to 35% off purchase of qualified new software – an exciting incentive to get up to date with the latest technology.

The future focus of Dassault Systèmes is on the innovative 3DEXPERIENCE platform, a disruptive technology that can completely transform your business. As a result, the largest discounts are for platform products, on premise or in the cloud.

As an example, a customer may have an existing Dassault Systemes CATIA V5 software and his installed base entitles them to a voucher good for 35% discount on a new product up to an amount 0f $35,000. Assume a new opportunity arises and the customer requires SIMULIA to run advanced simulations. If the list price of what is required is $100,000, then this can be purchased for $65,000 by applying the voucher.

As a trusted advisor, Tata Technologies can help navigate through the CTP program. Dassault Systemes has been investing billions into innovative technologies and helping organizations face business challenges. Please engage us to discover how your business can be transformed.

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Does your organization build mutiple prototypes for physical testing and verification? Do you feel that you could leverage more CAE and simulation technology? Is getting simulation results a bottleneck in your engineering process? If the answer is yes, you could benefit from a Simulation Benchmark.

The Simulation Benchmark assessment captures the opinions of senior and knowledgeable personnel in your organization on the current state and future Simulation requirements for your business. In addition, a priority for improvement and an assessment of current effectiveness is recorded. It centers on 17 key Simulation “Pillars” ranging from Physical Prototypes, through to Best Practices. The pillars are listed below:

  1. Simulation Tools and Technology
  2. Physical Prototypes and Testing
  3. Complexity of Physical Prototyping
  4. Regulatory Requirements
  5. Materials Library
  6. Simulation Automation
  7. Management of Simulation Data
  8. Simulation Process
  9. Simulation organization
  10. Optimization Tools
  11. Stiffness and Deflection
  12. Durability and Fatigue
  13. Crash or Drop
  14. Fluid Dynamics
  15. Thermal
  16. Simulation demand
  17. Best Practices

After the 17 pillars have been covered, senior and knowledgeable personnel are also invited to “spend” an assumed benefit in value areas within your business. The areas identified are improving time to market, increasing the portfolio of the company and improving product quality.

Finally, the tool produces a comprehensive report showing the customer’s current state of maturity and a benchmark comparison with the industry.

Participants have found this process to be very useful as it allows them to prioritize their initiatives, gives a high-level view of their roadmap to success and provides them with industry benchmark information.

From solver perspective, number of enhancements have been made but as additive manufacturing is gaining popularity these days, let’s start with what’s new is available at AM front.

Additive manufacturing functionality enhancement

  • Until past release, number of basic AM simulation features were not a part of main solver and required specific configuration to access. Starting 2018x all AM is in FD05 and in 2019x all AM is in GA.
  • Eigen strain has been added as an input/output in AM that can be accesses using existing subroutine UEPACTIVATIONVOL that now has eigenstrain as an argument. The material orientations can be defined as well as modified. As eigen strain is treated as instantaneous load, it can cause convergence problem. In such cases, eigen strain can be applied as a ramp input.

 

  • The conventional displacement of nodal output includes displacement prior to activation as well. New output variables UACT and URACT contain translational and rotational displacement only after activation.

  • Improved convergence of heat transfer analysis when linear elements are used with temperature dependent material properties.
  • The event series data is no longer limited to 53 million events. It has now been extended to 420 million events. Available from 2019xGA.
  • Property and parameter tables now available for Abaqus explicit as well starting 2019xFD01. Earlier this functionality was limited to standard only.
  • Number of heat energy outputs have been added for non-uniform moving flux. These are element internal heat energy called as EHUMDFLUX and element internal heat energy density called as EHUMDFLUXDEN. Both field and history outputs are available.
  • 2D and axisymmetric elements are not available that support *FILM parameter as well for convective heat transfer.

This blog is a part of series “what’s new in SIMULIA 2019”. Please follow our blog site regularly for next blog article on this topic.

Every year around this time, SIMULIA comes up with official declaration of new releases. That news is followed by discussion and buzzes around new functionalities and features. Last year we released a series of blog articles on new features in 2018 suite of products and we are following a similar pattern this year starting with Abaqus CAE.

  • Translation of parts and instances: Additional parameters have been introduced to ease this operation. Earlier CAE prompted to pick a start and end points to define direction vector. Now it possible to define the direction by picking global or local coordinate axis, datum axis as well as any straight edge. Moreover, the start and end point method is supplemented by a local coordinate system, if needed. Here is how user interface looks like:
  • CAE support for CAXA/SAXA element types: CAXA/SAXA element types are very useful in modeling structures that have axisymmetric geometry but not axisymmetric load. These element types are present in solver since long time but only option to use them was through manual keyword input. Now these element types are part of Abaqus CAE.
  • Optimization enhancement for additive manufacturing: Overhands can be difficult to print and they require support structures as well. It is advisable not to have overhand structures in the part subjected to AM process. Now an additional geometric restriction is available in optimization module of CAE to prevent overhangs formation.
  • Other optimization enhancements:
  • Shape optimization is often used after topology optimization to reduce hotspots. Earlier only controller based algorithm was supported for shape optimization that imposed many restrictions on choice of design responses. Now sensitivity based algorithm is also available in CAE for shape optimization. Moreover, for all types of optimization schemes, it is not possible to export the output in IGES format as well. Earlier this output feature was available only in form based native TOSCA GUI.
  • The envelop contours can not be created for complex stress values as well. Three types of complex stress contours are supported as shown below:
  • Another significant enhancement in viewer is the visualization of variable beam radius. This is applicable to the output of TOSCA sizing when beam elements are present in the structure. The name of field variable is BRADIUS.

This blog is a part of series “what’s new in SIMULIA 2019”. Please follow our blog site regularly for next blog article on this topic.

This year 2019 Abaqus release has seen number of potential enhancements in Abaqus explicit. Some are general purpose while others are tied to specific procedure and application. Let’s have a look at what’s new in the explicit basket.

  • Lumped Kinetic Molecular model: This model has been developed to simulate behavior of gases that can be of much use in air bag deployment simulation. The method is based on kinetic theory of gases which states that pressure exerted by a gas in closed chamber is a result of collisions between gas molecules as well as between gas and chamber surface. These collisions are perfectly elastic in nature. As number of molecules in a mole of gas is equal to Avogadro number (6.023e23) which is very large from computational perspective, lumped mass approach is used in Abaqus in which a gas particle is defined as a collection of many molecules. The method has been validated with analytical approaches. This method now replaces the Unified Pressure Method that cannot capture the change in pressure as the airbag expands. However, LKM is computationally more expensive than UPM. Best approach might be to use LKM during airbag expansion when pressure variation is large and then switch to UPM method. Switching time should be defined in such a case. Most expensive method is still CEL.

  • C3D10 element has been introduced in explicit that is a true second order element that offers larger stable time increment compared to C3D10M or linear element. It supports all the loads and BC’s supported by conventional continuum elements in explicit.
  • Limiting stop feature: It is not possible to stop the explicit analysis when a certain output parameter reaches a limiting value. These physical parameters may be node based such as reaction forces or element based such as equivalent plastic strains. The keyword is *FILTER.
  • Improved performance: Substantial decrease in solver time when performing large system level crash simulation over high performance cluster. Below is the example of a 5M DOF crash model on multiple cores.

This blog is a part of series “what’s new in SIMULIA 2019”. Please follow our blog site regularly for next blog article on this topic.

One of the noticeable change that has been made in 2019 solver is its capability to handle large models. SIMULIA has noticed that in recent past customers have shown increased interest in dealing with very large models with 2M degrees of freedom or more. There are multiple reasons for this requirement. First is scalability. More and more customers are interested in large system level simulations compared to part or assembly level. Second is fidelity and accuracy. Mesh size is getting finer to capture behavior at micro level instead of macro level.

When it comes to solving very large models, iterative solver has many advantages compared to direct solver such as less memory consumption, scalability and speed. A new hybrid iterative solver scheme has been introduced that offers more flexibility for choosing number of MPI ranks and number of threads per rank for a given node. These parameters can be defined in the abaqus_v6 environment file. This is equivalent to DMP+SMP allowing efficient memory management.

The iterative solver is available in 3DExperience 2018x FD05 and 2019x FD01 release. It supports many more Abaqus features compared to conventional iterative solver such as gaskets, friction, plasticity, creep, periodic boundary conditions etc.

This blog is a part of series “what’s new in SIMULIA 2019”. Please follow our blog site regularly for next blog article on this topic.

Simulations in Aerospace and Defense companies have a well-defined workflow. They have two separate teams for composites products: one for design and other for simulation. Composites ply design is primarily done by design engineers. These are the folks that determine the composites material as well as ply thicknesses and stackings in different regions of the composites part. CATIA composites design and manufacturing workbench has all sorts of tools to help designers achieve their objectives. We have discussed these workbenches in past.

However, because of FAA and other regulations in place, design has to be validated with FEA simulation and for most of the non linear workflows, Abaqus is the right solver choice. Though CATIA does provide an environment for Abaqus pre-processing, the preferred method in Aerospace industry is to use Abaqus CAE user interface. This is because of two reasons. First reason is better meshing capabilities offered by Abaqus CAE and second is tight coupling of Abaqus CAE with underlying solver. The obvious questions that arises is “how to move the ply information from CATIA to Abaqus CAE.”

The answer is composites link in collaboration with composites modeler for Abaqus CAE. The composites link exports the ply data from CATIA in form of layup file. Based on workflow, three options are possible.

  • Export only the ply data: When mesh is already in Abaqus CAE environment.
  • Export ply data with CATIA mesh: When meshing has been done in CATIA Analysis environment.
  • Export ply with external mesh file: When Abaqus input file needs to be merged with ply data.There are further options to export data either with or without taking change in orientations due to wrinkling into account as done by composites fiber modeler. Once the mesh and layup comes in Abaqus CAE environment, it is possible to explode the shell data based on ply thickness and create solid elements from shells. Abaqus CAE automatically creates section properties and assignments based on modified ply orientations. It is further possible to visualize ply orientations on each ply as well as ply stack plots on element by element bases. Once the data transfer and visualization is complete, the entire advanced analysis set up such as bird strike, fracture or delamination can be defined in Abaqus for analysis.

The structural model creation app of 3D Experience 2017x is primarily the pre-processing application for structural models that is available in Structural Analysis Engineer (DRD) and Mechanical Analyst (SMU) roles. This article briefly explains the meshing algorithms available in the given app. The mesh creation module of structural model creation app looks like this:

This meshing algorithm is simplest and easiest to use to create continuum linear/quadratic tetrahedral meshes. Global mesh specifications can be applied to control overall mesh size and local mesh specifications can be used to make finer or coarser mesh regions of the model. Few advanced parameters such as minimum mesh size and quality control factors are available.

 

 

In this technique the surface of geometry is meshed with triangular meshes which then fill the inside volume with solid elements using the specified volume growth parameter. Basic parameters such as mesh size, element order and absolute sag are available in this method. This technique captures the surface geometry of the model more precisely than the Octree Tetrahedron mesh method. Accordingly, the mesh appears a lot smoother.

 

 

This algorithm fills solid geometry with tetrahedral elements working inwards from an existing surface mesh. The approach is like tetrahedron mesh. However, in this approach support is an existing surface mesh instead of solid geometry. The order of filled element type is independent of the order of surface element type.

 

 

This meshing scheme is a big bonanza for Abaqus CAE users, specifically those users who have been using Abaqus CAE for computationally fluid dynamics applications. Unlike other FEA pre-processors, 3D Experience platform offers one click linear hexahedral meshing of complex geometries through this meshing technique. For CFD applications, this includes boundary layer as well. Moreover, no fluid domain geometry needed to create CFD mesh. Application computes fluid domain automatically based on certain input/output parameters. The ratio of Hexahedral elements to other elements depends on the complexity of geometry. Higher the geometry complexity, lower is the ratio.

Many more meshing techniques exist such as beam mesh, surface triangle mesh, octree triangle mesh for shapes of varied topologies. To know more, please contact us.

 

 

 

 

 

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