ANSYS Mechanical – Overcoming Convergence Difficulties with Automatic Remeshing (Nonlinear Adaptive Region)

One of the problems we can encounter in a nonlinear structural analysis in ANSYS Mechanical is that elements become so distorted that the solver cannot continue.  We get messages saying the solver was unable to complete, and the solver output will contain a message like this one:

 *** ERROR ***                           CP =      37.969   TIME= 14:40:06
 Element 2988 (type = 1, SOLID187) (and maybe other elements) has become
 highly distorted.  Excessive distortion of elements is usually a       
 symptom indicating the need for corrective action elsewhere.  Try      
 incrementing the load more slowly (increase the number of substeps or  
 decrease the time step size).  You may need to improve your mesh to    
 obtain elements with better aspect ratios.  Also consider the behavior 
 of materials, contact pairs, and/or constraint equations.  Please rule 
 out other root causes of this failure before attempting rezoning or    
 nonlinear adaptive solutions.  If this message appears in the first    
 iteration of first substep, be sure to perform element shape checking. 

The Solution branch will have the telltale red lightning bolts, indicating the solution was not able to complete due to nonconvergence.

If you are not aware, one technique we can use to get past this problem of excessive element distortion is to have ANSYS automatically remesh the model or a portion of the model while the solution is progressing.  The current state of the model is then mapped onto the new mesh, in the currently deflected state.  In this manner we can automatically continue with the solution after a slight pause for this remeshing to occur.  Minimally all we need to do as users is insert a Nonlinear Adaptive Region under the Static Structural branch, and review and specify a few settings (more on this later).

Let’s take a look at a simple example.  This is a wedge portion of a circular hyperelastic part, subject to a pressure load on the top surface.  Other boundary conditions include a fixed support on the bottom and frictionless supports on the two cut faces of the wedge.

For this case, the nonlinear adaptive region is the entire part. 

The initial mesh was setup as a default mesh, although note that for 3D models the nonlinear adaptive capability requires a tetrahedral mesh up through the current version, 2019 R2.

Prior to solving with the nonlinear adaptive region included, this model fails to converge at about 56% of the total load.  With the addition of the nonlinear adaptive region, the model is automatically remeshed at the point of excessive element distortion, and the solution is able to proceed until the full load is applied.  The force convergence graph has a solid vertical orange line at the point where remeshing occurred.  The method can result in multiple remeshing steps although in the sample model shown here, only one remeshing was needed.

The image on the left, below, shows the original mesh at the last converged substep before remeshing occurred.  The image on the right is the first result set after remeshing was completed.

The tabular view of a result item will show in the last column if remeshing has occurred during the solution.

Here is the final deformation, for the full amount of pressure load applied on the top surface.

Next, let’s take a look at the nonlinear adaptive region capability in more detail.

First, multiple substeps must be used for the solution.  If we are performing a nonlinear analysis, this will be the case anyway.  Second, Large Deflection needs to be turned on in the Analysis Settings branch.  Also, results must be stored at all time points (note that time is a tracking parameter in a static analysis, but all static as well as transient results in ANSYS Mechanical are associated with a value of ‘time’).

There are several restrictions on features that CAN’T be in the model, such as cyclic symmetry (hence the frictionless support BC’s on the simple model shown above), Auto Asymmetric Contact, Joints, Springs, Remote Forces and Displacements, etc.  Also certain material properties are excluded, such as Cast Iron plasticity and Shape Memory Alloy.  Also, as mentioned above, for 3D models, the mesh must be tetrahedral.  For a full listing of these restrictions, refer to the ANSYS Mechanical User’s Guide.  A search on ‘nonlinear adaptive’ will take you to the right location in the Help.

Nonlinear Adaptive Regions can be scoped to 3D solid and 2D bodies, or to elements via a Named Selection. 

In the Details view for the Nonlinear Adaptive Region, the main option to be defined is the Criterion by which remeshing will be initiated.  There are three options available in Mechanical:  Energy, Box, and Mesh.

The Energy criterion checks the strain energy of each element within the Nonlinear Adaptive Region.  If the strain energy is above a criterion, remeshing is triggered.  The input is an energy coefficient between zero and one, and is a multiplier on the ratio of total strain energy of the component divided by the number of elements of the component.  Recommended values are 0.85-0.9.  A lower coefficient will tend to cause remeshing to be more likely.

The Box criterion defines a geometry region based on a coordinate system and bounds relative to that coordinate system.  Elements in the Nonlinear Adaptive Region whose nodes have all moved within the box will be remeshed.  The idea is that if it’s known that elements will be highly distorted as they move into a certain region, we can ensure that remeshing will occur there.

The Mesh criterion allows us to specify that remeshing will occur if mesh quality measures drop below certain levels as the mesh distorts.  For 3D models, the available measures are Jacobian Ratio and Skewness.  These are described in the Mechanical User’s Guide in the section on Nonlinear Adaptive Region.

In the example shown above, the Energy criterion was used with an energy coefficient of 0.85.

There are some things to be aware of when you are trying to implement a Nonlinear Adaptive Region to help overcome convergence difficulties.  First, if any of the restricted features mentioned above are included in the model, such as remote displacements, it’s not going to work.  Therefore, it’s important to review the list of restrictions in the Help and make sure none of those are applied in your model.  Second, ‘buckling’ or element distortion due to an unstable structure is not a behavior that Nonlinear Adaptive Regions can help with.  The Nonlinear Adaptive Region capability is more suited to problems like hyperelastic seals being compressed or objects that are undergoing a high degree of bending (but not snapping through). 

Also, a coarse mesh that distorts may not produce a usable remesh.  The remeshing step may occur, but the simulation may not be able to proceed beyond that and stops with an error in element formulation error.  More mesh refinement may be needed in this case.

As a further word of caution, self contact problems may not work very well within the context of Nonlinear Adaptive Regions.  If self contact is needed, consider splitting the bodies into multiple parts to avoid self contact. 

There are some other considerations for the method as discussed in the Help, but hopefully the guidelines and recommendations presented here will allow you to filter potential applications appropriately and setup models that can take advantage of the Nonlinear Adaptive Region capability.  We have a short animation which shows the remeshing step in the sample model. 

If you have nonlinear static structural models with convergence difficulties due to excessive element distortion, please consider using this method to help you get a fully converged solution.

Here is a video to help everyone visualize:

High Frequency Electromagnetic Updates in ANSYS 2019 R2 – Webinar

HFSS (High Frequency Structure Simulator) employs versatile solvers and an intuitive GUI to provide unparalleled performance, as well as deep insight, into a wide variety of 3D electromagnetic (EM) problems. ANSYS HFSS is the premier EM tool for R&D and virtual design prototyping. It reduces design cycle time and boosts your product’s reliability and performance. 

The ANSYS HFSS simulation suite consists of a comprehensive set of solvers to address diverse electromagnetic problems, ranging in detail and scale from passive IC components to extremely large-scale EM analyses. Its reliable automatic adaptive mesh refinement allows users to focus on the design instead of spending time determining and creating the best mesh.

Join PADT’s Lead Electromagnetics Engineer Michael Griesi for a look at what new capabilities are available for HFSS users in ANSYS 2019 R2.

This presentation will include updates for the following topics:

  • Solve speed
  • Electronics Desktop
  • ANSYS Cloud
  • Post processing
  • And much more

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All Things ANSYS 044: Optimize Materials Knowledge & Applications with ANSYS Granta pt. 2

 

Published on: August 14th, 2019
With: Eric Miller, Anthony Dawson, & David Cebon
Description:  

In this episode, the continuation of our discussion on ANSYS Granta, your host and Co-Founder of PADT, Eric Miller is joined by Anthony Dawson, Senior Director of Materials Business Unit Product Operations at ANSYS, and David Cebon, Chief Technologist at ANSYS Granta, as they dive deeper and discuss the history of the company, and the specific tools that make up the Granta family of products.

If you would like to learn more about what’s available in this latest release check out PADT’s webinar on ANSYS Granta here: https://bit.ly/3001IFA

If you have any questions, comments, or would like to suggest a topic for the next episode, shoot us an email at podcast@padtinc.com we would love to hear from you!

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All Things ANSYS 043: Optimize Materials Knowledge & Applications with ANSYS Granta pt. 1

 

Published on: August 12th, 2019
With: Eric Miller, Ward Rand, & John Perek
Description:  

In this episode your host and Co-Founder of PADT, Eric Miller is joined by Ward Rand, one of PADT’s other Co-Founders, and John Perek, Principal Materials Engineer at Honeywell Aerospace to discuss the introduction of Granta to the ANSYS product line, its benefits for materials selection & analysis, and thoughts the Honeywell team has had since implementing it into their workflow.

If you would like to learn more about what’s available in this latest release check out PADT’s webinar on ANSYS Granta here: https://bit.ly/3001IFA

If you have any questions, comments, or would like to suggest a topic for the next episode, shoot us an email at podcast@padtinc.com we would love to hear from you!

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Optimize Materials Knowledge and Applications with ANSYS Granta – Webinar

Every product is made from materials, and in order to correctly select and apply said materials, decisions need to be based on analysis on the right information. ANSYS Granta software ensures accurate, consistent, traceable materials information every time and provides the tools you need to support design, research and teaching.

This toolkit is divided into three main products, each designed to accomplish a variety of different tasks when it comes to enabling smart material choices:

ANSYS GRANTA MI is the leading system for materials information management in engineering enterprises. A single “gold source” for your organization’s materials IP saves time, cuts costs and eliminates risk.

ANSYS CES Selector is the standard tool for materials selection and graphical analysis of materials properties. A comprehensive materials data library, plus unique software tools enable you to use materials to innovate and evolve your products.

ANSYS Materials Data allows users to gain easy access to the material property data you need for structural analysis, from within ANSYS Mechanical. Find coverage of many important materials classes, save time wasted searching for and converting data and gain greater confidence in your data inputs.

Join PADT’s Application Engineer and ANSYS Granta expert, Robert McCathren for a deep dive into the capabilities of this new release and how you can benefit from applying it in your organization.

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All Things ANSYS 042: Mechanical Updates in ANSYS 2019 R2

 

Published on: July 30th, 2019
With: Eric Miller, Ted Harris, & Joe Woodward
Description:  

In this episode your host and Co-Founder of PADT, Eric Miller is joined by PADT’s Simulation Support Manager & Specialist Mechanical Engineer Joe Woodward to discuss the latest additions and improvements made for structural analysis in ANSYS Mechanical 2019 R2.

If you would like to learn more about what’s available in this latest release check out PADT’s webinar on Mechanical Updates Updates in ANSYS 2019 R2 here: https://bit.ly/2OuGmyP

If you have any questions, comments, or would like to suggest a topic for the next episode, shoot us an email at podcast@padtinc.com we would love to hear from you!

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Mechanical Updates in ANSYS 2019 R2 – Webinar

With ANSYS structural analysis software, users are able to solve more complex engineering problems, faster and more efficiently than ever before. Customization and automation of structural solutions is much easier to optimize thanks to new and innovative finite element analysis (FEA) tools available in this product suite. 

Once again, ANSYS is able to cement their role as industry leaders when it comes to usability, productivity, and reliability; adding innovative functionality to an already groundbreaking product offering. ANSYS structural analysis software continues to be used throughout the industry, and for good reason as it enables engineers to optimize their product design and reduce the costs of physical testing. 

Join PADT’s Specialist Mechanical Engineer Joe Woodward, for an in-depth look at what’s new in the latest version of ANSYS Mechanical, including updates regarding: 

  • Software User Interface
  • Topology Optimization
  • Rigid Body Dynamics
  • Post Processing
  • And much more
Natural frequency study of engine block in ANSYS Mechanical

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All Things ANSYS 041: Simulating Additive Manufacturing in ANSYS 2019 R2

 

Published on: July 15th, 2019
With: Eric Miller & Doug Oatis
Description:  

In this episode your host and Co-Founder of PADT, Eric Miller is joined by PADT’s Lead Mechanical Engineer Doug Oatis, to discuss the tools that make up the ANSYS Additive family of products (Additive Suite, Additive Print, & Additive Prep), and how those tools help to make 3D printing more effective and easier to navigate.

If you would like to learn more about what’s available in this latest release check out PADT’s webinar on Additive Manufacturing Updates Updates in ANSYS 2019 R2 here: https://bit.ly/2JHWYxn

If you have any questions, comments, or would like to suggest a topic for the next episode, shoot us an email at podcast@padtinc.com we would love to hear from you!

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Five Takeaways from the New User Interface in ANSYS Mechanical 2019 R2

Ten years is a long time in the life of a software product.  While ANSYS itself has been around since the early 1970’s and what is now known as ANSYS Mechanical is approaching 20 years old, the user interface for ANSYS Mechanical maintained the same look and feel from version 12.0 in 2009 through version 2019 R1 in 2019.  That’s 10 years.  Certainly, there were many, many enhancements over that 10 year period, but the look and feel of the Mechanical window remained the same.

With the release of version 2019 R2, the Mechanical user interface has changed to a more modern ‘ribbon’ window, as shown in the red region here:

After having used the new interface for a while, here are 5 takeaways that are hopefully useful:

  1. It’s easy to use.  Sure, it’s different but the overall process is the same with a simulation tree on the left, details to enter and adjust at lower left, graphics in the middle, message, and graphs at the bottom, and the main menus across the top.
  2. ANSYS, Inc. has helped by providing a 12-slide (some animated) usage tips guide which pops up automatically when you launch ANSYS Mechanical 2019 R2.
  • As in the old menu, the ‘Context’ menu changes based on what you have clicked on in the tree.  For example, if you have clicked on the Mesh branch, the Context menu will display meshing controls across the top of the window.
  • As intuitive as the new ribbon interface is, there are some functionalities that you may have trouble finding.  Not to worry, though, as there is a new Search field at upper right that will likely take you to the right place.  Here I am interested in making a section plane for plotting purposes.  My first thought was that it would appear in the Display menu.  When I didn’t find it there, I simply typed in ‘section’ in the search field and the first hit was the right one.

After clicking “Take me there”:

And the resulting section plot:

  • Some capabilities show up in the File menu other than the expected Save and Save As functionality.  For example, Solve Process Settings is now in the File menu.  However, the main functionality is in the Solution context menu, such as using Distributed solutions and specifying the number of cores.

In short, the 2019 R2 improvements to ANSYS Mechanical allow for easier and faster setup of our simulations.  If you haven’t given it a try, we encourage you to do so.

Automating Subsea Design (or How I Learned to Love Parameters)

In a previous life, I worked in the maritime and offshore energy industries and used ANSYS as part of my daily routine in structural design. I eventually discovered myself in a position where I was designing subsea equipment for use in offshore oil and gas fields. One thing I quickly discovered was that although subsea structures tend to be fairly simplistic looking (think playground equipment…but 10000 feet underwater) there are multiple design factors that can easily cause a domino effect that would require redesign(s). Whether it was a change brought upon by the client, tool manufacturer, or to satisfy the whims of marine warranty companies, there was always a need to evaluate multiple variants of any subsea structure.

Sounds like a very reactive process, right? So how can we bring this process into a more streamlined analysis workflow within ANSYS? Just use parameters with SpaceClaim and ANSYS Mechanical!

So what can parameters do to aid in this process?

  • Remove repetitive tasks
  • Account for geometric changes to CAD models
  • Use a range of values for material properties
  • Create associative connections between CAD models and ANSYS results
  • Allow for automatic goal driven design exploration

Now let’s look at some common use cases for parameters that I’ve run into in the past:

Accelerations for Onboard Equipment and Cargo

Cargo transported on the ocean is subject to the same accelerations that affect the vessel transporting it (surge, sway, heave, pitch, roll, and yaw). These accelerations are then combined into three representative accelerations and applied in multiple loadcases.

Typically, these loadcases are resolved in independent analysis systems but we can remove all that fluff with a simple parameter driven analysis. All one has to do is tag inputs and result items as parameters and then input values for each load case (or Design Point). In this case I have selected the XYZ components of an acceleration input applied to a mass point as well as the total deformation and maximum equivalent stress. With the push of a button ANSYS will then solve all of these design points and will amend the table to show the selected results corresponding with each design point. Results from the Design Points can be uploaded individually but this parametric analysis has made it very easy for us to determine which Design Points / load cases have the greatest influence on the design.

Geometry Influence Study

So one of the questions often asked during the design process is “Will the design work after we change this dimension to compensate for X?” which is often followed by a discussion on robustness (which is then followed by a change order). So let’s skip the discussion middle-man and move to be proactive by using parameters to quantify just how much we can change our geometry before a problem arises.

Here we have an example subsea Pipeline End Termination (PLET) structure and let’s say a client has asked us to verify if this design can work for various pipeline sizes. The PLET has some major parts that can be influenced by this change: The pipeline clamp, cradle, flanges, ball valve, and bulkhead.

Because we can use parameters there’s no need to make a new model. Merely tag items you wish to create parameters for in SpaceClaim:

Then ANSYS Workbench will start to populate its parameter tables accordingly:

We can then make certain parameters dependent on others, or define them via simple expressions. In this way we can enforce clearances and relations between the various bodies in our model.

From here all we have to do is define our variables for our future analyses:

Then tell ANSYS to solve all the design points with a single click. Note that users can create charts and tables before the solve and ANSYS will populate these live during the solution process. Individual design point results and geometries can also be reviewed at any time.

For this particular analysis we provided the same load to each Design Point but a good next step would be to set a goal driven analysis and have a range of loadings on the pipeline end of the PLET to represent various installation conditions.

Parameters are a very powerful tool within the ANSYS toolbox. They can remove repetitive tasks within FEA, easily create loadcases, and address concerns about design robustness by letting ANSYS and SpaceClaim handle CAD model rework.

That’s it for this blog post! I’ll be creating a few offshore industry-specific posts in the future as well so stay tuned!

Simulation for Additive Manufacturing In ANSYS 2019 R2 – Webinar

Additive manufacturing (3D Printing) has been rapidly gaining popularity as a true manufacturing process in recent years. ANSYS’ best-in-class solution for additive manufacturing enables simulation at every step in your AM process, and helps to optimize material configurations, and machine & parts setup before printing begins. 

Through the use of ANSYS tools such as Additive Suite & Additive Print, paired with topology optimization capabilities in ANSYS Mechanical Workbench, the need for physical process of trial-and-error testing has been greatly reduced. 

Join PADT’s Simulation Support and Application Engineer Doug Oatis for an exploration of the ANSYS tools that help to optimize additive manufacturing, and what new capabilities are available within them when upgrading to ANSYS 2019 R2. This presentation includes updates regarding:

  • Archiving materials no longer in use
  • Visualization of AM process
  • AM overhang angles
  • Preview part & support
  • And much more

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All Things ANSYS 040: Live From the 2019 ASME Turbo Expo – CFD Applications for Turbomachinery

 

Published on: July 1st, 2019
With: Eric Miller, Robin Steed of ANSYS, & Chris Robinson of PCA Engineers Limited
Description:  

In this episode your host and Co-Founder of PADT, Eric Miller is joined by ANSYS CFX & Turbo Tools Lead Technical Product Manager Robin Steed, and Managing Director at PCA Engineers Limited, Chris Robinson, live at the 2019 ASME Turbo Expo in Phoenix Arizona, for a discussion on the past, present, and future of ANSYS CFD and its use in the realm of turbomachinery. Both Robin and Chris have multiple years of experience working in this industry, and their expertise provided some fascinating insight into what this tool is all about.

If you would like to learn more about what’s available in the latest CFD update check out PADT’s webinar on Fluids Updates in ANSYS 2019 R2 here: https://bit.ly/2J6l5We

If you have any questions, comments, or would like to suggest a topic for the next episode, shoot us an email at podcast@padtinc.com we would love to hear from you!

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All Things ANSYS 039: Updates for Design Engineers in ANSYS 2019 R2

 

Published on: June 17th, 2019
With: Eric Miller, Ted Harris, & Tom Chadwick
Description:  

In this episode your host and Co-Founder of PADT, Eric Miller is joined by PADT’s Simulation Support Manager Ted Harris, and Senior CFD Engineer Tom Chadwick for a discussion on what new capabilities (beta or otherwise) are available for design engineers in the latest updates made to Discovery Live in ANSYS 2019 R2.

If you would like to learn more about this update and see the tool in action, along with others in the 3D Design family of products (Discovery AIM, SpaceClaim & Live) check out PADT’s webinar on the topic here: https://bit.ly/2KfO0tK

If you have any questions, comments, or would like to suggest a topic for the next episode, shoot us an email at podcast@padtinc.com we would love to hear from you!

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Fluids Updates in ANSYS 2019 R2 – Webinar

ANSYS CFD goes beyond qualitative results to deliver accurate quantitative predictions of fluid interactions and trade-offs. These insights reveal unexpected opportunities for your product — opportunities that even experienced engineering analysts can miss.

Products such as ANSYS Fluent, Polyflow, and CFX work together in a constantly improving tool kit that is developed to provide ease of use improvements for engineers simulating fluid flows and it’s impacts on physical models.

Join PADT’s Simulation Support and Application Engineer, Sina Ghods, for a look at what is new and improved for fluids-related tools in ANSYS 2019 R2. This presentation includes updates regarding:

A new fluent experience

Parallel Mosaic-enabled meshing

Discrete Phase Modeling

Creating high-quality meshes for complex models

Transient elasticity for fluid structure interaction

And much more

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3D Design Updates in ANSYS 2019 R2 – Webinar

When it comes to the exploration of rapid 3D design, simulation provides a more efficient and optimized workflow for design engineers looking to streamline product development and improve product performance. The toolkit of flagship ANSYS 3D design products made up of Discovery SpaceClaim, Discovery Live, and Discovery AIM allow users to build, and optimize lighter and smarter products with an interface easier to use than most other simulation products. 

Users can delve deeper into the details of a design with the same accuracy as other, more robust ANSYS tools, all while refining their concept and introducing multiple physics simulations to better account for real-world conditions.

Join PADT’s Simulation Support Manager Ted Harris, for a look at what’s new for this line of products with the release of ANSYS 2019 R2. Explore updates for these three tools including:

  • Shared Topology
  • Meshing
  • Navigation
  • Modal Supports 
  • Multi-physics Coupling
  • Topology Optimization 
  • And much more

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