## Project Management for Non-Linear Dynamics Simulation with ANSYS LS-DYNA

We spend a lot of time writing articles about how to use the very capable tools that are available from Ansys, Inc., but tend to skip over the project management side of simulation. But, project management can be as important, especially for challenging simulations, as the technical aspects.  We recently completed a series of Non-Linear Dynamics simulations with ANSYS LS-DYNA and ended up learning a lesson or two about how to get such projects done on time and on budget.

# What is Non-Linear Dynamics Simulation, and what makes it different?

When materials are deformed so fast that the rate of strain changes material properties, we refer to that as non-linear dynamics. In non-linear structural simulation, the material may be distorting in a non-linear way (usually plasticity), but the non-linear properties are dynamic. Because of this, time gets involved in the equation, as do non-linear material properties.  Think car crash, metal forming, drop, bird impact on windshields and jet engine blades, and bullets going through stuff.

There are various software tools in the Ansys family that can do the non-linear dynamics, but our preferred program is Ansys LS-Dyna.  It is an explicit dynamics solver that solves structural, fluid, thermal, and other physics.  It is an amazing program that does many things. Still, for the class of problem we are talking about here, we only care about time-dependent material non-linearity for structural deformation.

# Setting expectations

Before beginning a project of any type, it is important to establish goals.  Non-linear dynamics is no different. What is different is that you have to be realistic about what goals you can achieve.  The events you are modeling are, by their very nature are very, well, non-linear. The answers you calculate can change drastically with mesh, loads, material properties, and solver parameters.

If you need high accuracy, then you need to set the expectation that it will take longer to solve, and you have to be more careful with your model. If you don’t need accuracy and you may be looking for relative improvements, like seeing if one geometry option makes things better or worse in your design, then you can back off and be less detailed.  This difference can have a large impact on your schedule and overall cost.

So before you plan, before you start gathering information, decide what you expect to get out of your model.

# Planning for the Job

Once you have set your expectations and goals, it’s time to map out the project. It is not that different from most structural or vibration jobs. You still have to get geometry, create a mesh, define loads and constraints, apply material models, run, and post processes.

However, each of those steps can be different for non-linear dynamics.  Here are some critical issues to be aware of when producing a schedule:

• Geometry
If you are working with thin, especially sheet metal, parts, you probably want to use shells. They are more efficient and can be more accurate in many situations. You need to not just have a CAD model, but also a model that has the mid-plane surface defined as well as thicknesses.

You also want to look at removing tiny features that don’t impact the solution.  The run time in an explicit dynamic solver is driven by the smallest element size. If you have tiny features relative to your overall geometry, capturing them can drive up your run times.  So set aside time to remove or simplify them.
• Meshing
As mentioned above, small elements can drive up run time. Also, distorted elements or elements that become distorted can cause your solutions to diverge and fail. You may (probably) need to create a hexahedral (brick) mesh.  All of these things require more time to create the mesh, and from a project standpoint, you need to plan for that.
• Contact
Ansys LS-Dyan rocks at contact.  It is pretty much automatic in most cases. So here, you don’t have to set aside time to define and tweak your contacts to get convergence. But there are many options, including erosion and other fancy options. Understand your contact needs and track and manage them.
Everything in LS-DYNA is time-dependent, and loads are no exception.  If you are lucky, your load or loads are constant over time. But if not, you need to set aside time to characterize those loads and get them specified in the right format.  In addition, loads can be calculated, say the results of an explosion or an airbag deployment. These use Equation of State models to calculate forces on the fly and are a major advantage of the tool.
• Solving
From a project management standpoint, it is very important to plan for relatively long solves, restarts, and if possible, solving several jobs at the same time.  Non-linear dynamics is computationally intense. Do some trade studies on computer resources vs. schedule time.  Is it worth investing in more cores to solve faster or just let it chug away on a smaller computer? Also, don’t assume a single run to get the answer you want. Often you need to run the model multiple times before you understand what is really going on.

• Post-processing
We are solving highly non-linear events, and understanding what the model is telling us is the whole point of the exercise.  Budget time for processing massive amounts of data over time and reducing it into something useful. Also, time is needed to create animations.  The analyst may also find themselves buried in the weeds at the post-processing stage, and project management should take on the role of reviewing the results from a big picture perspective and drive what tables, graphs, plots, and animations are created.

# Keeping the project on the rails when things are literally blowing up and crashing

The dynamic nature of both the events being modeled and the process of creating and running the models make for a less predictable progression for the project.  A project manager needs to pay close attention to what is going on at all times and pull the engineers doing the work back up for air to find out where things are going.

Here are some things to watch out for:

• Building a model that is more complex than needed
• Making sure that the situation being simulated in the model is what the customer needs simulated
• Too much time being spent to fit the model on a limited computer. Get a bigger computer.
• The simulation engineer is fixated on details that don’t impact the solution much
• Oversimplification of components, connections, and loads.
• Science project mode – spending time trying to learn basic information or trying to get something new to work, and not solving a specific problem.

One of, if not the most important roles for the project manager is communication.  Constantly interacting with the engineers (without nagging) and with the customer (the person who will consume the results) is critical.  This is not a throw-it-over-the-wall type of project.  And the more you accomplish, often the more you have new questions.  It may take two weeks or nine months. But either way, the PM needs to be constantly talking to everyone involved.

And yes, here at PADT, we have actually modeled a train car going off the rails. The project, though, stayed on track because we kept a close watch and stayed focus on the specifications. Things did surprise us, and we had to change some of the model when we got the first results, but we planned for that, communicated with the customer, and kept our changes to what was needed to answer the customer’s questions.

Our cars have incredible crash safety, very few planes fail because of bird ingestion, and we create amazing components out of formed sheet metal because of this type of non-linear dynamic simulation, and in most cases, Ansys LS-Dyna. Proper project management that recognizes the challenges and differences for this type of project can make a massive variety of products even better.

## What I use Most from my Engineering Management Masters Degree

Even before finishing my mechanical engineering degree at the University of Colorado, Boulder in 2010, I had an interest in furthering my education. The decision I had at that point was whether the next step would be a graduate degree on the technical side or something more like an MBA. I would end up with the chance to study at the University of Denver (DU), focusing on Computational Fluid Dynamics (CFD), and if that field does not make it clear, my first stint in grad school was technical.

At DU, we sourced our Ansys simulation software from a company called, you guessed it, PADT. After finishing this degree, and while working at PADT, the desire to further my education cropped up again after seeing the need for a well-rounded understanding of the technical and business/management side of engineering work. After some research, I decided that a Master’s in Engineering Management program made more sense than an MBA, and I started the program back at my original alma mater, CU Boulder.

Throughout the program, I would find myself using the skills I was learning during lectures immediately in my work at PADT. It is difficult to boil down everything learned in a 10-course program to one skill that is used most often, and as I think about it, I think that what is used most frequently is the new perspective, the new lens through which I can now view situations. It’s taking a step back from the technical work and viewing a given project or situation from a perspective shaped by the curriculum as a whole with courses like EMEN 5020 – Finance and Accounting for Engineers, EMEN 5030/5032 – Fundamentals/Advanced Topics of Project Management, EMEN 5050 – Leading Oneself, EMEN 5080 – Ethical Decision Making, EMEN 5500 – Lean and Agile Management, and more. It is the creation of this new perspective that has been most valuable and influential to my work as an engineer and comes from the time spent completing the full program.

Okay okay, but what is the one thing that I use most often, besides this new engineering management perspective? If I had to boil it down to one skill, it would be the ‘pull’ method for feedback. During the course Leading Oneself, we read Thanks for the Feedback: The Science and Art of Receiving Feedback Well, Even When it is Off Base, Unfair, Poorly Delivered, and, Frankly, You’re Not In The Mood (Douglas Stone and Sheila Heen, 2014), where this method was introduced. By taking an active role in asking for feedback, it has been possible to head-off issues while they remain small, understand where I can do better in my current responsibilities, and grow to increase my value to my group and PADT as a whole.

## 5 questions we ask before preparing a CFD consulting quote

This post was created based on the expert advice of PADT CFD engineer and Project Lead, Nathan Huber.

Simulating the behavior of liquids and gases has become a standard part of product development in products where fluid behavior plays an important role.  Here at PADT, we have been using Computational Fluid Dynamics, or CFD, for years to model everything from combustion in turbine engines to cooling of electronics, to golf balls. With that experience, our estimates for a given project have become reasonably accurate.

However, we can only estimate accurately if we have complete and accurate information on what you need simulated and what you hope to gain from the simulation. To help everyone arrive at more accurate cost and schedule estimates, even if you are planning a project internally, we offer the following list of five questions we always ask:

## 1: Have we signed a Non-Disclosure Agreement (NDA)?

Before we can do anything, we need to have an agreement in place that clearly defines how both sides handle proprietary information.  When we have tried holding meetings to gather information for a quote before an NDA is in place, we almost always waste time. There is just too much that is proprietary in most products.

We also need to know the physical geometry of your system.  That is why we ask for an accurate and complete CAD model.  We take some time to poke through the files in our software to make sure we can use the geometry, it is accurate, and it has the level of detail required for CFD. Basically, we check to see if we can pull a fluid domain from your CAD models. Remember, we are not simulating the solid part of your product; we are modeling the inverse and therefore need to pull a negative volume from your geometry.

## 3. What are the Boundary Conditions and Material Properties?

Now that the geometric domain is understood, we need to know what is inside that domain, and what is acting upon it.  We will ask you for boundary conditions, and for the material properties of the fluid or fluids you are asking us to model.  The complexity, time variation, and severity of the loads drive the difficulty of setting up and running the simulation. And the material properties can also impact the sophistication of the model as well as its robustness.  Both, therefore, have a significant impact on cost.

## 4. What results do you want to see?

When a simulation finishes, it can be post-processed to get a vast array of plots, figures, animations, pretty pictures, etc.  Those take time to create, so we need to know what you want to see. Also, we set up some post-processing parameters before we start the simulation.

## 5. What do you want to learn from your CFD Simulation?

The whole point of doing a CFD simulation is to study the behavior of your system. We need to know what behavior you need to understand so we can make sure that the simulation we propose answers your questions and guides you in your design process.

We hope you find this review useful when you are planning your internal CFD project as well as those you outsource. And speaking of outsourcing, please consider PADT as your resources for any future simulation projects of any type, not just CFD.  Now, you already know what questions we will ask.

## Phoenix Business Journal: ​Remembering Kelley Johnson, aircraft design icon and project management superstar

One of my engineering idols is Clarence “Kelley” Johnson. He led the design of many of the coolest aircraft ever made, and he was a pioneer in managing large engineering projects.  In “​Remembering Kelley Johnson, aircraft design icon and project management superstar” I talk about why he was such an important figure in technology, and some rules he developed for effective project management. Even if you are not an airplane person, it is worth getting to know his work and his methods.