Category "Dassault Systemes"

Previous few blog articles primarily addressed Abaqus 2020x enhancements. Let’s have a look at the extended products enhancements that include ISight, Tosca and FeSafe.

ISight Enhancements

  • Export of Approximations: Till 2019x release, the export of approximation models was limited to coefficient data or excel spreadsheet format. In 2020x release, the RBF and RSM approximation models can be exported to FMU as well.
  • New components: Functional Mock Up (FMU) and Computer Simulation Technology (CST) components are now available in ISight workflows.

Tosca Enhancements

  • Sensitivities support: Though not essentially an enhancement in 2020x, it is worth mentioning that all four modules of Tosca now accept Abaqus sensitivities for all types of non-linearities. However, supported analysis steps are Static and Frequency only. Inertia relief included.
  • New Response: Plastic strain PEMAG now supported for shape, size and bead optimization.
  • Algorithm stabilized: Higher volume fractions eventually lead to convergence and stability concerns. While convergence is an Abaqus issue, stability of optimization has been improved in topology module with large volume fractions.

Fe-Safe Enhancements in 3DX:

  • App enhancement: While the role is still a separate license called as durability engineer role, the mechanical and structural scenario have been enhanced to include the fatigue interface.

Simultaneous execution: Though it is well understood that any fe-safe analysis requires stress results from a stress analysis, user now has an option to simulate both structural and durability cases at the same time. The backend data management architecture takes care of sequencing and linking.

  • Material enhancement: The entire Fe-safe material database can now be imported in the 3DEXPERIENCE Platform. Surface finish factors supported as well.
  • Element nodal outputs: This is perhaps a KEY enhancement. The fatigue is a surface phenomenon so averaged stresses at the nodes on surface are most appropriate for fatigue analysis. In prior releases of 3DX, only integration point stresses were supported. Starting 2019x FD06, element nodal stresses are available for fatigue.
  • Loading enhancements: Loading blocks now include residual stresses as well as implicit dynamics step. All Fe-Safe algorithms with and without mean stress correction are now supported. Both SN curve as well as EN curve algorithms are now supported in 3DX.
  • Coming Soon!! Linux and COS execution on cloud.

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This is a relatively bigger blog compared to previous ones because of an obvious reason; it covers a broad spectrum of non-linear enhancements which is Abaqus core technology. The blog covers four sections: additive manufacturing, element technology, material enhancements and fracture mechanics along with few other minor enhancements

Additive manufacturing:

  • Pattern based thermo-mechanical analysis: While in many cases laser scan paths are available to simulation users it is not always true. For those situations in which machine users do not wish to share their machine IP’s, a pattern based approach has been introduced which uses a raster scan path instead of a trajectory scan path. Material orientation and Anisotropic behavior are supported but not suitable for detailed microstructure simulation. This application is different from eigen strain simulation.
  • Event series enhancement: 2GB data size limit of event series was removed in 2019xGA and now event series can include up-to 420 million events.
  • Free surface evolution enhancements: In case of tie constraints, algorithm has been enhanced to include ties that are not activated until the underlying element becomes active.
  • Output enhancements: MAXPSCRT has been introduced to include maximum principal stress crack initiation criterion. It is available for both field and history outputs. BLADEINTERFERER has been introduced to predict clash between recoater and printed part. This will be available in 2020xFD01.

Element Technology:

  • Shear panel element update: SHEAR4 was introduced in 209xFD01 to model thin reinforced plates. It supports buckling. Equivalent shear flow output called SQEQ is supported.
  • Pyramid heat transfer element: DC3D5 has been introduced to manage transition between tetrahedral and hexahedral elements in thermal analysis.
  • Fluid pipe element enhancements: These elements now support following Non Newtonian flows as well:

Material enhancements:

  • VUMAT enhancement: A parameter has been added to define alternate bulk and shear modulus that can be used by explicit to find suitable time increment. It is called EFFMOD and visible in viewer. Abaqus CAE support is available from 2020xFD01.
  • Kinematic hardening enhancement: The material model has been enhanced to model stress relaxation behavior for metals subjected to step strain input. Suitable for metals that show viscoelastic like behavior during step inputs.

Creep Laws enhancement: Current creep models have A with dimensionality that creates ambiguity. The strain and time laws have been enhanced as follows to make A dimensionless. These enhancements are applicable to all the creep models.

Viscoelastic material enhancement: The prony series has now been enhanced to include frequency domain as well. Earlier prony series was valid in time domain only.

Yield surface enhancement: The non quadratic yield surface has been introduced in 2019xFD04. It is referred to as Barlat Plasticity. The stress component requires 18 coefficients and 1 exponent.

  • Metallurgical phase enhancement: In prior releases, the effect of additive manufacturing and other heat treatment processes on material properties at microstructural level required USDFLD subroutine. Effective 2020xFD01, this routine has been included on the material definition itself. Inservice performance of printed parts can now be more accurately simulated.

Injection Molding:

  • 3DX injection molding compatibility: The fiber orientation and residual stresses from third party simulation such as Moldflow can now be converted to a SIM file format. That means the 3DX structural simulation apps can now read moldflow results to predict in-service loads and warpage from third party plastic injection results.

Pre-tension enhancements

  • Non linear enhancement: In earlier releases, the direction of pre-tension section normal was not updated even in general step. Effective 2020xGA, the cut section normal direction can be updated in large displacement or large rotation analysis. It is activated as follows in the input file

*PRE-TENSION SECTION, FOLLOWER = (YES/NO)

Fracture Mechanics enhancements

  • Linear elastic fatigue enhancements: Linear elastic fatigue crack model was introduced recently in collaboration with NASA ACC team to model crack propagation for cyclic fatigue cycles. It allows for change in contact conditions as well as non-linear geometry effects. Several enhancements have been made in this model in recent FD’s. In 2019x FD03, an alternative method to smoothening of crack front was introduced. In 2019x FD04, mode dependent stiffness degradation was introduced.
  • Cohesive elements for Multiphysics: Couples temperature-displacement cohesive elements have been introduced to simulate debonding due to thermal expansion as well as hydraulic fracture. These elements are COH2D4T, COHAX4T, COH3D6T, COH3D8T. Coupled temperature-displacement-pore pressure elements available as well to include gap conductance effect. There is no change in the structural response of these elements.

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Increase Competitiveness Through Integrated  Mold & Tool Design

The pressure on mold and tool-makers is relentless. Time is always of the essence, and as cycle times reduce, further demands are made. Mold & tool production that took 4 months last year is now demanded in 3 months this year.  And so it goes on. Even when a part design is delivered late, the completion target for the mold or tool often remains unchanged

With these ever decreasing design-to-manufacturing cycle times and increasing complexity of the parts to be produced, toolmakers need to maximize the efficiency of the complete mold and tool design process

To do this toolmakers need to be able to:

  • Accelerate the design of molds & tools and ensure that that can produce the most complex of parts, reliably and to the required cost and quality targets.
  • Simulate, early in the design process, and compensate for the effect of deformation introduced by the manufacturing process such as material shrinkage, warping or spring-back.
  • Respond quickly to change requests – whether through late changes to the design of the part to be produced, or the need to address problems found during the manufacturing process itself. 

To addresses these challenges, the CATIA Mold & Tool design solution from Dassault Systèmes provides comprehensive and fully integrated capabilities specifically developed to meet the needs of mold and tool designers. These capabilities include the following features:

  • Rapid design of molds and tools
  • Process specific mold & tool design capabilities such as semi-automatic creation of parting surfaces, mold cores, cavities, runners, lifters and inserts.
  • Faster and safer design of complex tool assemblies through ‘smart’ components and standardized resources that embed custom behavior.
  • Advanced simulation & validation: Simulate the part forming process in order to quickly and accurately compensate for material deformation.
  • Integrated change management – Quickly identify the impact of a part change on the mold or tool, with full associativity between the part the mold and tool forming surfaces so that design changes can be propagated to the mold & tool designs.

Many leading companies have gained significant competitive advantage through these capabilities, with typical benefits being:

• Improved the whole mold & tool design process time by 70%.
• Achieved time savings of 30% across the initial mold design process.
• Reduced the time for manufacturability analysis from DAYS to hours
• Accelerated mold core & cavity design by 70 %.

Tata Technologies can help you get set up with CATIA Mold and Tooling. Contact us for a demonstration or visit our website www.tatatechnologies.com

While few of the Abaqus explicit enhancements in 2020x have been discussed in previous blogs on contact, this particular blog article specifically focuses on many more enhancements in explicit, with or without contact.

  • DT based element deletion: While explicit jobs never exit with fatal errors due to lack of convergence, they can still give fatal errors because of severe element distortion. An element deletion criterion has been introduced that allows user to set a trigger for element deletions based on element area, element volume, stable time increment and characteristic length. These triggers can be defined either as absolute or as ratios.
  • Linear Kinematic conversion: This is yet another approach to avoid fatal errors because of severe element distortion. In this approach, the elements are transformed to linear elements based on certain trigger threshold on distortion. It is applicable to most of continuum tetrahedral and hexahedral elements.

Enhanced CEL approach: Conventional CEL approach is good for solids only. When applied to liquids and gases, it may cause leakage especially when fluids create high pressure gradient, when fluids have large tangential velocity or at the location of sharp corners. The enhanced CEL contact formulation fixes this problem and is applicable to both solid and shell meshes. However, this enhanced formulation is more expensive in memory and computation.

Hybrid message parsing (HMP): This is an enhancement in parallel processing that can combine MPI (DMP) based parallelization and Threads (SMP) based parallelization. The solution can utilize thread based parallelism within a node as well as MPI to communicate between the nodes. It results in fine grained dynamic load balancing because when a thread completes its own elements computation work, it helps other threads within the same MPI rank.

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Subsequent to the blog article on few functionalities in Abaqus CAE 20202x, this particular blog article mentions enhancements in Abaqus solver 2020x contacts and constraints. The enhancements would be mentioned in reverse chronological order and few of these have been introduced in FP’s of 2019x as well.

  • Interference fit in Abaqus explicit: This feature has been in waiting list since long by users and its finally available now. Earlier releases of explicit had an option of strain free adjustment only for overclosures. From 2020x, if initial overclosure is “x” and interference is defined as “y”, then strain free adjustment is performed till “x-y” and rest is treated as interference being resolved through a smooth amplitude curve. That means a “two in one advantage” for explicit. Moreover, it is supported in Abaqus CAE.

Change in contact status legend: To make output more meaningful for the users, the contact status has been changed to bonded and “not in contact” as shown below. This is applicable to both standard and explicit.

Rate dependent cohesive damage: The damage initiation and damage evolution laws now have parameters to include rate dependency in cohesive contact for explicit. Earlier this feature was available in cohesive elements approach only. Effective since 2019xFD04.

  • Material based general contact property assignment: The conventional process of property assignment in general contact is a three-step process. First, define sets of elements. Second, use sets to define surfaces. Third, use surfaces in property definition. From 2020x, material can be directly called for surface assignment if that approach helps. This is true for both standard and explicit.

Thermal expansion of rigid bodies: The analytical and discrete rigid bodies have been existing in Abaqus since long. However, when it comes to combined structural and thermal steps, a body very rigid from structural perspective may expand well when heated. To incorporate this effect, thermal expansion of rigid bodies feature is now included in Abaqus standard. This is applicable to kinematic couplings as well as for bodies are not explicitly defined through a CAD geometry.

  • Small sliding in general contact: This is again a BIG enhancement based in users request. Small sliding substantially reduces the contact search time because it is based on flat surface approximation. When used correctly, it results in convergence improvement and less overall solution time. However, its absence in general contact was a bit bothersome. From 2020x, small sliding exists in general contact for standard.

General contact enhancement for Multiphysics: Beam elements have been introduced in general contact for thermal and thermal electrical procedures. This may be helpful in approximating some large size applications such as heat exchangers by modeling pipes as beam elements.

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Computer aided engineering has always been a role of a specialist. This statement is very much evident from the fact that more than 50 percent of analysts today have a graduate degree; either an MS or a PhD. This is because these physics-based simulations are a lot more than collection of icons, toolbars and pull-down menus. Unless the user is well familiar with the core engineering aspect of the problem being solved as well as with the underlying governing equations that solve the problem, he is very likely to make an error in modeling that would lead to erroneous results. In such situations “a stress solver becomes a stress creator.”

If one dissects the subject of computer aided engineering, he would see several branches of it. The main ones are: finite element analysis, computational fluid dynamics, multi-physical simulation as well as multi body dynamics. Each of these branches have several sub-branches of it. For example, finite element analysis can be divided into structural analysis, thermal analysis, coupled analysis. The structural analysis can be further sub-divided into linear static structural, non linear static structural, linear dynamic, non linear dynamic etc. As one moves keeps digging inside, simulation becomes more niche and more specialized. This justifies the need of a specialist with many years of experience with advanced technical and academic credentials.

While we, at TATA Technologies do not provide work experience or academic credentials, we do transfer expertise in computer aided engineering and many other fields of engineering through dedicated technical trainings as well as on the job trainings. We offer software products specific trainings such as Dassault Systemes portfolio, Siemens PLM portfolio, Autodesk portfolio as well as several industry vertical trainings such as modeling of welds and connectors in automotive chassis, design for light weight etc. We do provide small sessions on best practices as well such as effective element selection in Abaqus, overcome convergence problems in non linear simulation etc.

We train people with various levels of experience and knowledge. The student may be a fresh designer out of college who has recently joined his first organization or may be a subject matter expert with years of design or simulation experience and trying to learn something new. As mentioned, we teach both software as well as methodologies and workflows.

If you have a high end engineering software in your organization that seems to be underutilized because of lack of human resource, please get in touch with us.

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Its end of the year 2019 and just like any other prior year DS is ready with new release, both for standalone products as well as 3DX roles. Accordingly, we are ready with our blog series “what’s new in 2020”. So lets start with Abaqus CAE first. The later blog articles will include solver functionality enhancements as well.

  • Partitioning enhancement: The partition method using sweet and extrude has been improved to include multiple disconnected edges at the same time. That means multiple partitions can be done in a single partition operation. Less clicks, less time.
  • Global renumbering: It is now possible to define renumbering in assembly context. And that is true for both dependent and independent part instances. For large assemblies, the user now does not need to switch multiple times between part and assembly modules to perform renumbering. In case of dependent part instances, any renumbering performed on an instance is automatically propagated to associated part at part level mesh.
  • Enhancement in query tool: The queries for points/nodes/distances can now be made with respect to a local coordinate system as well that can be a cartesian, cylindrical or spherical CS. Earlier only global cartesian CS was available for queries.
  • Shrink fit possible in explicit: This is a BIG enhancement for our explicit users. Perhaps those users who have struggled with the convergence of shrink fit in standard would appreciate this feature. Earlier initial overclosures in explicit could only be adjusted strain-free thereby making explicit step ineffective for shrink fit. Now explicit step has option of treating initial overclosures as interference fit. This is applicable for both contact part as well as general contact inexplicit. Big relief.
  • Hyperfoam test data evaluation: Computation of material coefficients using uniaxial and multiaxial test data has been a very useful feature of Abaqus CAE. However this functionality was limited to hyperelasticity and viscoelasticity. Now hyperfoam material evaluation can also be done using curve fitting techniques.

Enhancements in copying models: The copy model feature has been enhanced to include constraints as well. However, if constraints refer to named sets and surfaces, those sets and surfaces should exist in the target model.

BC/Load manager with color coded cells: Lastly, the looks and feel of BC, Load and interaction manager has been enriched by making it color coded as shown below. It matters if this manager has to be used in a simulation report.

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In this series of ‘what’s new in 2019” release we will highlight new features in standalone fe-safe as well as in durability apps of 3D Experience platform. General enhancements as well as specific enhancements in fe-safe/rubber are included.

Durability roles in 3D EXPERIENCE Platform

  • Fatigue specialist role in 3D EXPERIENCE Platform is now available in 2019 GA though it was introduced in 2017x FD05. Perhaps one of the most interesting feature of any role on the platform is its “look and feel” apart from robust functionality behind the scene. Here is how latest fatigue specialist role looks like. The durability app is integrated into structural and mechanical scenario apps. Moreover, unlike standalone Fe-Safe, it is possible to visualize 3D model while creating scenario for durability in 3DX. Structural analysis case job and durability case job can be launched simultaneously from user interface.
  • Fatigue Loading: Number of complex loading scenarios are supported on the platform since 2018x release. These include superposition, sequence of stress or stress-strain frames, mean stress correction etc.
  • Dynamic case supported: There was enough requirement to support durability simulation for dynamic events.  Durability cases of FEA can now be used to define loading on the platform.
  • Surface finish: The Kt factor can be defined directly as a surface finish.
  • Cloud: The role is now available both on premise as well as on cloud.
  • Material properties/algorithms: Now include cast iron, SN curve definition, eN curve definition as well as constant amplitude endurance limit. The algorithms now include finite life, infinite life as well as stress based and strain-based algorithms.

      Enhancements in standalone Fe-Safe

  • Weld fatigue enhancement: No need to have perfectly structured meshes in region below the weld line nodes through the thickness for the calculation of nodal forces and structural stress. However, element faces should be present on the crack surface.
  • Integration of Tosca, Abaqus and Fe-Safe verity for the optimization of chassis sheet thickness with multiple seam welds.
  • Groups and sets created within Fe-Safe are now written out in the Fe-Safe ODB file.
  • A new algorithm called Prismatic Hull infinite life method was introduced in 2018xFD01 that is now available in 2019xGA.
  • Interpolation engine in Fe-safe Rubber: Abaqus Rubber models are computationally extensive and take long time to solve. In many situations full duty cycle takes long time to solve in abaqus. Now user can break up duty cycle in standard series of load combination levels. When imported in Fe-Safe rubber, solver can make interpolations to approximate full duty cycle stresses from standard series of stresses.

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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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