Category "Simulation"

There have been quite a few market whispers about MSC Software and its products since the company’s acquisition by Symphony Technologies few years back. It’s flagship pre-processing tool called MSC Patran has been under spotlight since the introduction of new equivalent tool by MSC Software (now Symphony) called MSC Apex.  MSC Software adopted a similar strategy during 2008-09 by introducing a bunch of multi-disciplinary pre-processing tools such as MD Patran and later SimExpert. All these products had a very long gestation period with little luck in making a long term market presence.

Many veteran FEA analysts, particularly in aerospace domain are well familiar with the pains of using MSC Patran in geometry cleaning, meshing and composite modeling environments. The objective of this blog is to take a deep dive into these issues and demonstrate how an alternative product called Femap from Siemens can alleviate many of these unaddressed issues.

Femap has been a part of FEA community since more than 30 years and it was developed with the mission of having a dedicated PC based pre and post processor for engineering FEA. It is solver neutral as well as CAD independent solution that offers high performance modeling and analysis capabilities to solve toughest engineering problems.

  • Mid surface extraction

Almost all FEA pre-processors have this embedded tool but as the geometry becomes more and more complex, many of them fail to extract mid surfaces correctly. The automatic feature of Femap makes this job not only easy with minimum number of clicks but offers higher fidelity as well. User does not need to select opposite faces multiple times in case thickness changes in space. Just enter the maximum thickness value a part has and Femap does the rest for you. Its further possible to combine the mid surfaces so they appear as a single entity in the history tree.

 

  • Tools in the meshing toolbox

Before creating a mesh, the meshing toolbox offers multiple value added features to clean and modify the underlying geometry for a better mesh.

  • Project curve:

This features splits the extracted surface at the boundary of thickness transition so that the underlying elements are able to update the shell thickness property as the thickness changes on either side of the split.

  • Feature removal options

There are many features in CAD that may not be needed in FEA analysis and holes are the prominent ones. It is possible to close holes and similar geometries with just a click, if needed. By default, a point entity is created at the geometric center of the closed holes to make sure a kinematic constraint can be applied at those points, if needed.

  • Pad and washers

These features allow for mesh refinement in the vicinity of holes and depending on the geometry of holes, either a washer (circular) or a pad (square) option may be chosen. The feature creates iso-parametric meshes around the holes based on the distance of influence defined by the user. This is an “on the fly” feature that updates an existing mesh every time this feature is executed instead of creating a new mesh.

  • Dynamic node repositioning

This is a very handy feature to improve mesh quality on the fly. With the mesh quality contour option active, user can dynamically move any node of the mesh either on surface or on a curve until its quality improves which is instantly perceived by the user as element color changes from red to green. The effect of this tool is very local and only a few elements in the vicinity of selected node are considered at a time.

  • API’s for automating repetitive tasks

Most of Nastran based BDF’s include multiple RBE’s. Femap understands the pain of creating these RBE’s manually and applying boundary conditions to them. The custom tools provide an option to create RBE’s by selecting peripheral curves or nodes. The independent nodes are created automatically. Using API’s it is further possible to completely automate the RBE generation process.

The grouping options in custom tools provide an option to automatically define a group for independent nodes of all the RBE2’s in the model. This group can later be used to create constraints on RBE’s without picking each independent node individually.

 

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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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.

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