It’s amazing to see these and realize how mainstream this type of analysis has become, and how the graphics and presentation of these results feels familiar, even to the general public. We also marvel at how quickly these types of analysis have been conducted and presented, and how widely democratized they’ve become, with new results and simulations being presented every day.

Sneeze simulation developed as part of Dassault Systèmes' 3DEXPERIENCE Open COVID-19 community.

This is just one more sign that the use of analysis tools to predict product performance has gone from being a niche application only performed by expert users, to something that is routinely done as a standard part of the design process in all industries. The medical device industry is no different, but the design of medical devices does have several unique characteristics that sets it apart in its use of engineering analysis tools.

Analysis Elements Unique to Medical Devices

Complex Material Behavior

Whether you’re trying to model the response of human tissue to your models, or designing a shape-memory alloy for a vascular stent, the types of materials used for medical device design are often complex, and designed to perform very specific demanding tasks. The analysis techniques we use to analyze steel and aluminum structures just won’t cut it here.

Product Release is Glacially Slow

With the testing, clinical trials and documentation needed to release a medical product, it can take several years to get a product to market. Because of this, you can’t rush a minimum-viable product to market and then rapidly design a secondary iteration to optimize and improve it, like you can in other industries. Analysis helps in two ways: it allows you to fully test out a wide range of design ideas to get the released product as optimized as possible, and by spending up-front time in analysis, you can hopefully reduce the number of physical and clinical trial cycles as much as possible.

Failure is Not an Option

The medical device industry is notoriously risk-averse, for good reason. If your toaster breaks, you won’t be happy, but you can go buy a new one—but if your pacemaker quits unexpectedly, the consequences will be much more severe. The industry is well armed for this, with extensive computer analysis, physical testing and clinical trial protocols before any product release, but there are several applications that can’t easily be tested physically, where analysis is used as the sole validation tool.

More Power!

Devices, particularly those involving electronics, are getting smaller and more powerful. Where electronics are involved, that means more heat, and with very strict reliability and touch-temperature requirements to meet, that heat has to be removed safely from the device. Best-guess techniques for thermal management just don’t cut it anymore, and a robust CFD analysis is needed to optimize heat dissipation from the PCB to the environment.

Keep the Noise Down

Electromagnetic noise, that is. Medical devices need to not only be compatible with the radio waves that are generated by other equipment and our cellphones, but also need to limit the amount of electromagnetic interference they emit. This EMI/EMC testing is expensive and complicated in real-life, so being able to predict a successful test is incredibly valuable.

Nonlinear Materials, Everywhere

If there’s one characteristic that rings true for almost any structural analysis of a medical device, it’s that the materials are nonlinear. Most materials in the human body are highly nonlinear in their structural behavior, and most devices that interact with the body are, too. From human tissue, nitinol stents, and elastomeric valves, nonlinear materials are everywhere.

To assess these properly, you’re going to want an analysis software with strong nonlinear capability. This means lots of material models, built-in tools for mapping real-life behavior to those material models, and a robust solver that is able to iterate through challenging problems. One example of a software package that meets all these requirements is SIMULIA Abaqus, which combines one of the most powerful nonlinear solvers in the industry with automated contact modeling and an incredible range of material models.

Test, Test, Then Test Again:

Because the clinical trial and product release process takes so long, medical device companies want to minimize the number of times a device goes through it. Because of this, the released product needs to be fully optimized – the opposite of other industries where an early product can be released to the market and then improved in later versions.

Because of this, you’re going to want to look for analysis solutions that let you fully explore the design space and provide tools for optimizing to an ideal solution.

This product exploration typically has three potential angles:

• Parametric iterations – where certain parameters within the design can be varied, and a large batch of analysis cases run with those variations. Key analysis numerical and graphical outputs can be reviewed for each design iteration to investigate the sensitivity of the device to changing parameters.
• Parametric optimization – similar to the above, but with the ability to home in on the ideal solution to meet a certain design set of design goals by varying those parameters. Tools like this allow an ideal solution to be developed by changing model parameters.
• Topological optimization – where the physical shape of the object is changed to provide the ideal shape to meet the design goal. This technology can be found in tools such as Tosca (and now available within the SOLIDWORKS 3D Creator cloud CAD package) and designers can apply these techniques for structural strength or fluid flow. Topological optimization methods were originally developed by mimicking how the human body grows bone, so applying them for medical devices feels appropriate!

Images before and after topology analysis performed with SIMULIA Tosca.

A good design exploration process often involves all three elements, so medical device designers are increasingly looking for a suite of tools that offer all these options.

Safety First

The impact of a failed medical device can be catastrophic, so designers will do everything they can to minimize the risk of failure. This means that rigorous clinical testing will be employed over many years before a device is released; however, there are aspects of device performance, especially with how a device performs over a long period of time, that just can’t be feasibly tested in a clinical environment.

Expansion analysis of a vascular stent, performed in SIMULIA Abaqus.

Fatigue-life testing for evaluating the functional life of a vascular stent is one area where the use of analysis is becoming more critical. A stent is typically made up of a shape-memory metal alloy, which is compressed and inserted into a patient’s blood vessel, and then expands to its original shape, holding the blood vessel open and improving blood flow. It will remain in the patient forever and needs to continue to perform its function. Increasingly, regulatory bodies, such as the FDA, will accept finite-element stress results as a primary part of the product validation package for a product.

If you review the guidance published by bodies like the FDA, they stress the importance of capturing as many real-life elements as possible, including the temperature-dependent behavior of the material and accounting for the residual stresses created during the manufacturing process. When selecting an analysis package, you should make sure that it can capture all of these real-life aspects.

Keeping Your Cool

Devices are getting smaller and smarter every day, and that leads to big challenges when it comes to keeping electronics cool. All electronic devices give off heat, and the more powerful a device is, the more heat there is to give off. Removing heat is particularly important in the medical device realm, as increased operating temperature normally results in a reduction in reliability, which is unacceptable for most medical applications.

Traditionally, a fan or other forced cooling device was often included to keep things cool, but space, noise or aesthetic concerns increasingly rule this out as an option.

Today, a lot of the cooling strategy starts at the PCB board level, with thermal vias, in-plane heat spreaders or thermo-electric coolers, being employed to get the heat out of the system as efficiently as possible. Newer technologies, such as heat-pipes, are also being employed to aggressively move heat from one area in the system to a place where it can be safely dissipated.

CFD analysis of an electronic device, showing device temperatures and airflow paths.

These thermal problems are so intense that a best-guess approach to a solution is not good enough. Heat management strategies need to be carefully optimized, and a thermal analysis using a computational fluid dynamics (CFD) software package, such as SOLIDWORKS Flow Simulation, is a critical part of that process.

When selecting a software package, you’ll want to make sure that it can model all the heat management strategies you’ll need to employ – both now and in the future. The best of them have dedicated sub-models for things like heat-pipes and TECs, as well as the ability to approximate in-board cooling elements.

Electromagnetic Interference and Compatibility

Electromagnetic testing is one of the most important validation steps in the medical device design process and is often one of the most feared. Simple changes to a system can have major impacts on the electromagnetic interference it generates, as well its vulnerability to outside interference—and wireless transmission is critical to the function of many devices today. On top of that, the testing is expensive and logistically challenging. This combination of complexity and cost make electromagnetics a great candidate for investigation through electro-magnetic analysis.

Being able to test a device for EMI/EMC virtually means that design improvements can be rapidly cycled, giving confidence that a product will pass when subjected to validation testing. When selecting an EMI/EMC analysis package, it’s important to be able to consider all aspects of electromagnetics, so look for the different types of solvers and physics available. For example, CST Studio Suite offers finite element, finite integration and transmission line matrix solver techniques, covers low-frequency and high-frequency, and can optionally include thermal and particle calculations too.

Much has changed in the world of medical devices over the past 20 years, and the adoption of analysis technology has a big role to play in the advancement of that change. These tools allow products to be developed more quickly, safely and cost-effectively than ever before, and over the coming years we’ll see FEA, CFD and electromagnetic analysis tools becoming increasingly mainstream.

To learn more about SOLIDWORKS simulation for product development in health care, check out the whitepaper Simulating for Better Health.

If you’ve answered YES to any or all of those questions, then buckle up, because Visualize Professional in SOLIDWORKS 2019 has got an awesome new feature that you will want to learn about.

Figure 1

Yes gearheads, the latest release of Visualize Professional has a physics-based driving simulator, which you can control with an Xbox controller (or motion path) and create beautiful, photorealistic animations of your car simulation.

This new feature, which is the first of its kind in CAD, is aimed at automotive designers. It’s promising an easy workflow to assist designers with bringing their creations to virtual life, enabling designers to show how their designs will look in the physical world, before having to cut a single piece of metal (or sculpt a single lump of clay, as is the case in the automotive concept world).

In this article, we are going to show you the basics of how to get started with that very task! So, if photorealistic car animations are your thing, then read on.

Getting Started

First up, you’re going to want to start your Visualize Professional software.

Once it is loaded, you should click on the Sample Projects tab to see the sample models that are available to you. You can see how that screen looks in the Figure 2 below.

As this is a driving simulator, we are going to need a set of wheels, and luckily there is an example of some pure American muscle available for you to play with in the sample projects tab.

Go ahead and click the 1969Camaro.svpj icon to open it up.

Figure 2

After you have opened up the Camaro project, then you will be presented with the following screen. This is the main work area of Visualize Professional, and most of your work will be done from here.

Figure 3

Let’s familiarize ourselves with the work area and find out how to navigate before we move onto the simulation and rendering stuff.

Obviously the main area in the middle is your viewing area, where your 3D model is displayed. You can orbit, zoom, pan, and do all the other things that you are used to from the main SOLIDWORKS program. We are going to assume that you already know how to navigate the 3D space in SOLIDWORKS, so there is no need to belabour the point here.

At the very top of the screen, we have our Visualize options, such as File, Edit, View, Project, Tools and Help. This, naturally, is where we load and save our projects, access commands such as Undo, Copy, Paste, add windows to our viewscreen, and access tools such as Snapshot, Render, and Help.

As we want to be animating this thing eventually, we want to add the Timeline to our screen. So go ahead, click View, and then click Show Timeline from the drop-down menu.

The timeline will appear at the lower portion of the screen, as you can see below.

Figure 4

SOLIDWORKS users will recognize this type of timeline from the SOLIDWORKS animation and motion study features. It is a keyframe-based system, exactly the same as in SOLIDWORKS proper. We will look at the timeline in more detail later.

Now, cast your eyes to the top-right-hand side of the screen. You will see five icons on tabs, as you can see in the figure below.

Figure 5

These icons, from left to right, allow you to access the Models, Appearances, Scenes, Cameras, and File Libraries respectively. These icons are fairly self-explanatory, so we will look at them in more depth as we use them though the article.

First, let’s add a Scene. Click the Scene tab, and you’ll see a bunch of backgrounds appear in the right-hand panel.

Double-click the Route 66 icon in the Environment section, and you will see an HDR scene appear in the background, as seen below. You can see more about how to alter the scene and lighting over at this link.

Figure 6

Now that the scene is set, click the Models icon, and click the entry for 1969 Camaro beneath it to open up the model options panel, as you can see below. Now you can see four tabs visible. Go ahead and click the Physics tab, to show you the options for your simulation type in the drop-down menu.

Naturally, we wish to simulate driving a car, so go ahead and select Car from the Simulation Type menu.

Figure 7

Clicking on the Car Simulation Type will open up the Vehicle Setup driving simulation menus. At last!

This is where the fun begins.

As mentioned earlier, Visualize Professional features a physics-based engine, and can add mass, gravity, and motion to your simulations, and the 3D bodies in the simulation will respond to these physical parameters.

The best part of the Driving Simulation is that SOLIDWORKS have added actual vehicle dynamics to the software, so you don’t have to worry about the nightmare of coding vehicle behaviour yourself. Anyone who has worked in vehicle dynamics will know what a major chore that would be!

The result is an easy-to-use, intuitive GUI that bears more resemblance to a videogame (such as the Forza Motorsport series on Xbox) than it does to an actual simulator.

Actually, Forza Motorsport is way more complicated to use, when you really get into it.

Vehicle Setup Parameters

OK, so we have opened up the Physicstab, we have selected Car as our Simulation Type and we can now see the Vehicle Setup options. It’s quite a long panel, so we have cut it in half and displayed each half side-by-side, just for the sake of the article aesthetics.

Figure 8

As you can see in Figure 8 above, we have options to change the mass, acceleration, maximum torque, maximum RPM, drive wheels (FWD, RWD or AWD), brake wheels and steering wheels.

These default values are not befitting a 1969 Camaro, so we will change those values to something a little more accurate.

So we change the values to:

Mass: 1500kg

Acceleration: 1

Peak Torque: 610 Nm

Maximum RPM: 6000

Drive Wheels: Rear

Brake Wheels:Front

Steer Wheels: Front

The next section of the Vehicle Setup options shows the Advanced Properties. We will leave these as the default values for this article. Anyone with experience in vehicle dynamics knows how tweaking these values can have profound effects on the handling of the car…so we will leave well alone!

But just as a summary, these Advanced Properties will change the steering, shock absorber travel, wheel friction, camber angle, and all of those lovely complicated things that will dynamically affect the ride comfort, fuel consumption, and even stability of the vehicle (in real life). Feel free to play with these parameters for yourselves though.

Nearly Ready…

Right, then. Our car parameters have been defined. We just have a couple of little items to help define the simulation, and then we are ready to go.

Scroll back up to the top of the Vehicle Setup panel and locate the Driving Behaviour and Vehicle Wizard buttons.

Figure 9

Vehicle Wizard

The Vehicle Wizard allows you to define the moving parts of your vehicle for the animation and simulation. Here, you can assign parts of your model that will move, such as the wheels and callipers.

We can also set up the direction of travel of the vehicle, because we want it driving forward (+X direction) and not skidding sideward.

You can assign the parts manually, or you can use the automatic function. For the case of this article, we will just select Automatic Mode, and click Next.

You should now see the following image on your screen (Step 1). Go ahead and assign the direction of the vehicle, and click Next.

Figure 10

Now, you should see Step 2.

You can see in Figure 11 below that the software has assigned the wheel parts automatically. If you are happy with the setting, click Next to advance to Step 3.

Figure 11

The final step (Step 3) assigns the parts of your model as callipers.

Figure 12

Now your callipers are set, go and click onApply. Congratulations…your car now has wheels and callipers assigned, and the simulation will recognize those parts as such.

Driving Behaviour

The Driving Behaviour options let you determine how your car will be controlled in the simulation.

We can see four options here. These are:

Controller: This allows you to control with an Xbox controller or the WASD keys.

Turn: This will make the car turn in a circle (no input required)

Straight: Self explanatory

Path: This allows you to specify a path using waypoints in the Path Propertycontrols.

Before we explore these motion options, we will need to open the Simulation Manager. This is at the very bottom of the Vehicle Setup panel, as you can see back in Figure 8. Go ahead and click it, and you will see the following panel appear to the right of the timeline, as you can see below clearly in Figure 13:

Figure 13

If you select Turn orStraight in the Driving Behavior options, and click the PLAY icon in the Simulation Manager, you’ll see your car drive in a circle or straight line respectively. Easy enough, right?

If you want to use the Controller option, or the Path option, it’s a little different.

Go ahead and select Controller from the Driving Behaviour menu.

Controlling the Car Manually

OK, you’ve selected Controller. Now the car is ready for manual input. Now click the PLAY icon on Simulation Manager, and the car will accept your inputs.

Press your W key to go forward, the A key to steer left, D key to steer right, and the S key to reverse. The Q key will activate the brake, and E will activate the handbrake. Just like a video game.

Now, if you want to record the motion (which you definitely will, if you want to render it later), you will need to go onto the timeline, and drag the red bar to the time value that you want, depending on the required length of your animation. You can see in the image of the timeline below, we have dragged the red bar to the 5 second mark. So our simulation in this case will be 5 seconds long…this method is very similar to animating in SOLIDWORKS proper.

Figure 14

Next, you need to press the red RECORD icon in the Simulation Manager to record your inputs.

Go ahead and click the record button, and move your car around with the keyboard or your Xbox controller. When you have finished driving around, click the square STOP button in the Simulation Manager, and you will notice that your timeline has populated with yellow bars, representing the motion of your vehicle components, and their physical position with respect to time.

Figure 15

If you look at the left hand side of the timeline, you will notice another set of icons, similar to the Simulation Manager. You can see another PLAY button here. Go ahead and click that, and you’ll see the simulation played back in the main window.

Figure 16

The bars in the timeline represent the entirety of your simulation/animation.

Let’s go ahead and render it, to see what it looks like.

To access the render settings, you can either go to the menus at the top and select Tools > Render, or else you can go to the panel above the main viewscreen and select the little camera aperture icon, as seen below.

Figure 17

This will bring up the Output Tools menu. Output Tools will allow you to render still images, animations, perform Sun studies, or even put your model on a turntable, just like at a motor show!

In this case, we would like to test render the animation.

So, locate the Animation icon (indicated by the green arrow in the image below.

Now we can see two tabs…one for Animation Options and one for Render Options.

The Animation Options will let you set the file format for your rendered video (we selected MP4) as well as the output directory for your finished file.

The Render Options tab will let you set the quality of the rendered video.

When you are happy with the settings, go ahead and locate the Start Animation Render button at the bottom of the panel, and click it.

Depending on your hardware capabilities and the quality of render, this might take a while.

As we have only selected Preview quality, it doesn’t take long.

Figure 18

You can see our little test render in the video below.

So, those are the basics of manual control, the Simulation Manager, and rendering the animation using the Output Tools.Let’s take a look at using waypoints to create a motion path.

Creating a Path

Head back over to the physics panel on the right-hand side and select Driving Behaviour > Path.

You will see a new set of options (Path Properties) appear underneath, as you can see in Figure 19 below.

Figure 19

Click on Create New Path Point and you will see a white square with a number 1 above it in the main viewing area. Click it again, and you will see a second square appear, with a number 2 above it, as you can see in the image below. You can add as many as you like. When you click the PLAY button in the Simulation Manager, your car will follow the path.

Figure 20

If you wish to edit your path into something a little more curvy, then you can do so by clicking the Object Manipulation Tool in the tool bar just above the main viewing window, then clicking on a waypoint. You will see a transform axis tool appear on the selected object, and you can move it by dragging one of the colored axis handles, as shown below.

Figure 21

You can click the PLAY button on the Simulation Manager to check that your path is looking OK, and when you are ready to record the animation, simply press the RECORD button on the Simulation Manager. Just remember to hit STOP when the path course has been completed, or else it will keep recording in the timeline and you’ll end up with a really long video.

When you are happy with the animation, you can render it out as we did before.

You can see the results in the video below. We have increased the render quality in this video.

That’s All, Folks!

So, in this tutorial, you have learned how to start a project and how to navigate both the software interface and the 3D space with your model.

You now know how to start a simulation, and change the vehicle dynamic characteristics, as well as change the environment scene.

You can control your vehicle with both the keyboard/controller method, and using waypoints, and you also know how to render the video using the Output Tools menu.

Is there anything else? YES! We didn’t show you how to set up the cameras…but setting up cameras properly is beyond the scope of this article, and sadly that’s all we have the time and the space for. And besides, this is an engineering website, not film school! We can show you the basics, but composition and creativity is down to you!

Fortunately, Hawk Ridge Systems have made a video showing you the basics of setting up a camera, which you can see over at this link.

We have hopefully shown you the basics of setting up a simulation, and rendering it into a nice video. Go ahead and experiment yourselves and see what you can come up with.

That’s what we’ve been doing anyway. We had no idea how to use this feature until 2 days ago…

But if that proves anything, it demonstrates how easy it is to make videos for showing off your vehicular creations in the latest release of Visualize Professional.

So go forth and make some sweet videos. Feel free to share the links with us in the comments below.

We would love to see your results! It’s quite likely that you can teach us a thing or two as well!

Until next time…adieu!

The majority of these tools are available from the Evaluate tab of the SOLIDWORKS Command Manager.

Some of these tools must first be activated by enabling the add-in.

There are tools for checking manufacturability, cost, conformance to company standards and even environmental impact in your design:

• DFMXpress can be used to check the manufacturability of a design. This tool ships with all levels of SOLIDWORKS.
• Costing, available in Professional, allows users to instantly get an estimate of the cost of a design—and it offers feedback on which features are most expensive so users can quickly redesign the part to reduce the cost.
• Design Checker is available with Professional and Premium levels. Design Checker allows users to create checks to ensure that designs meet company standards. This tool can also make corrections when a check fails.
• Sustainability can help users evaluate the environmental impact of a design. Sustainability Xpress ships with all levels of the software and works only with parts. Sustainability is available with Premium and will work with parts and assemblies.

There are industry-specific tools for those that work in the mold, plastics or forging industries. With the exception of Plastics, the following tools ship with all versions of the software:

• Draft Analysis, Undercut Analysis, Parting Line Analysis and Thickness Analysis can identify problems in parts or tooling.
• Deviation Analysis, Curvature and Zebra Stripes can show flaws on the faces of a design.
• Check and Geometry Analysis can find flaws in model imported geometry. Import Diagnostics can detect and fix faulty faces and gaps that can cause issues later in a design and prevent the user from being able to create a 3D solid model.
• Compare Documents allows users to compare two separate models, assemblies and drawings and identifies any differences between them. This is useful when it’s necessary to identify changes quickly in a newer version of a file.
• Plastics adds additional tools and capabilities for those working in the plastics industry. Plastics is only available as a separately purchased item.

Many tools are specific to assemblies. Unless noted, these tools are available with all levels of the software:

• Tolerance Stack-up is available with Professional and Premium levels and can prevent manufacturing errors resulting from tolerance stack-up issues.
• Interference Detection will identify interference between components. Coincident faces can be listed as interfering, which can be useful in preventing excessive wear. A selection of parts or an entire assembly can be analyzed and interference in subassemblies can be ignored.
• Clearance Verification checks the gap between parts.
• Collision Detection allows users to check if moving parts collide. Run Interference Detection before Collision Detection, as interference between the selected components will prevent Collision Detection from finding a solution. As with Interference Detection, a selection of parts or an entire assembly can be analyzed. Collision Detection is available in the Move option menu.
• Hole Alignment checks for misaligned holes. The “Hole center deviation” sets the maximum deviation that will be evaluated. Holes that exceed this deviation will be ignored, as will aligned holes.

• Physical Dynamics, like Collision Detection, is available from the Move menu. As components are manually moved, collisions between components are captured and the mates for those components are evaluated to determine how the components should move. The result is realistic motion within an assembly.
• Motion is similar to Physical Dynamics, except that the motion is defined manually. While not actually an analysis tool, this tool can help users understand the intended motion of an assembly. Motion studies are available near the bottom of the window.

• Assembly Visualization allows users to rank parts by mass and quantity, as well as other user-definable criteria. This tool provides a graphical representation of the ranking.

• Top-down design is not so much a tool as a modeling practice. By creating parts in the context of an assembly, users can capture important relations between these parts. This will allow changes in one part to automatically change other related parts.

SOLIDWORKS also includes a number of general tools. Unless noted, these tools are available with all levels of the software:

• The Measure tool allows users to measure distances between faces, edges and vertices. It can also provide the area, perimeter, radius and diameter of a selection(s).
• The Mass Properties tool calculates model properties, such as mass, density, volume and moment of inertia. These values are calculated using the design’s geometry as well as the materials.
• The Center of Mass tool will, as the name implies, identify your design’s center of mass.
• The Sensors feature will provide real-time warnings if a criterion is exceeded. The criteria available include simulation data, mass properties, dimensions, component interference, measured values, proximity of components and costing data.
• Design Study can be used with simulation parameters, Sensors, or user-defined global variables to help optimize a design. Once the criteria for the Design Study are defined, the designer modifies the design until all the criteria are met. Like a Motion Study, a Design Study is available in the pane near the bottom of the window.

• Symmetry Analysis evaluates part or assembly symmetry about a selected plane.

There are also tools available in the Simulation group of tools:

• Simulation is used to predict how a design will perform under loading. The purpose is to determine if a component will fail under a defined load. A design can be optimized using targets such as maximum stress, maximum deviation and factor of safety. Simulation tools are available at the following four levels:

ο Simulation Xpress is available at all levels of the software, but is limited to single body parts and linear materials.

ο Premium includes linear analysis for both parts and assemblies as well as multi-body parts. This level of Simulation also gives the designer greater control over simulation parameters such as the type of load, restraints and mesh density.

ο Simulation Standard adds fatigue analysis, which allows users to estimate the life expectancy of a product. This level of Simulation is only available as a separately purchased item.

ο Simulation Professional adds optimization, frequency, buckling, thermal and drop test analysis. This level of Simulation is only available as a separately purchased item.

ο Simulation Premium adds the ability to run an analysis on nonlinear materials and is also only available as a separately purchased item.

There are additional distinctions between the different levels of Simulation. SOLIDWORKS provides a Simulation Matrix that lists these differences.

• Simulation Flow evaluates fluid flow as well as heat transfer. FloXpress is available with all levels of the software and the full version of Flow is available as a separately purchased item. Electronic Cooling and an HVAC module are also available. Again, SOLIDWORKS provides a matrix that lists the capabilities of the different Flow offerings.

With all of the tools SOLIDWORKS offers to evaluate your design, design errors no longer need to be responsible for manufacturing errors.

About the Author

Joe Medeiros is a senior applications engineer at Javelin Technologies, a SOLIDWORKS reseller servicing customers throughout Canada. Medeiros has been involved with SOLIDWORKS since 1996. He regularly blogs about the product and has won awards for his blogging.

(*Most simulation engineers don’t work 24/7.)

The Chainsaw is the tool you use to cut models in half and then only solve that half. This is applicable whenever parts have symmetry, which they usually do, sometimes even two points or axis symmetry. I know people tend to think of cutting models in half as extra work, but it really isn’t. Consider this: Imagine a model of symmetrical shape, like a rectangle, that has 50,000 nodes. If all loads and fixtures are the same, then the displacements and reactions on the 25,000 nodes on one side will be identical to the other. However, the solver doesn’t know that, so it will assume you need all nodes solved. This means while the program is crunching through the last half of the nodes it actually already has that data solved! Imagine applying that to anything else. I’m asking you, would you like more solve time, or less? Pick less! As for setup, making an assembly cut could not be simpler, and then you just apply a symmetry condition as a fixture on the cut face. Done.

Virtual Reality is the tool you use to simplify difficult-to-mesh connecting hardware such as bolts, bearings, springs or any parts you are not interested in but need the mass effect (remote mass). Virtualizing parts has many benefits. Firstly, you don’t have to mesh them, so that saves time. Secondly, virtualization removes interferences. It is common for things like bolts, pins, bearings and other connectors to interfere due to being modeled larger than the holes they fit into. This makes simulation difficult, as meshing with interference is not possible. Also of benefit is the ability to add in virtual loads, such as a bolt preload or a spring K factor. Lastly, bolts and pins are actually nonlinear in their factors of safety, and thus the most accurate way to calculate them is with the polynomial equation inherent in the virtual connector.

The Transmogrifier is the tool you use to make a model work for finite element analysis (FEA). This means making modifications, configurations and simplifications in order to make simulation feasible. The motto is, “If a simulation model doesn’t work . . . MAKE it work!” For many users, this appears to be a huge obstacle. However, simplification is your friend and is actually quite easy. The trick is mastering the use of configurations, as it will make less of a headache for you, the user. Remember that configurations of parts can be used in a configuration of an assembly, so an FEA configuration of an assembly, referencing FEA versions of parts with modified dimensions, is really all you need. As for the modifications themselves, they usually involve eliminating interference that is created as a result of stacking tolerance in virtual parts, or the opposite (gap). While gaps can be handled easily, interference cannot. Other things include simplifying unnecessary features, such as cosmetic features, or features that serve a purpose other than what is currently being simulated (for example, heatsinks don’t serve any purpose structurally, just suppress them for your strength test and deal with them at a later time).

The Doctor is the tool you use to check on the health of your study. The Doctor comes in many forms, but mostly when simulation engineers talk about health, they mean mesh health. This can easily be determined with the mesh aspect ratio plot, found in the mesh tools. An ideal aspect ratio is 1, which means all sides are equal. Stretched elements, such as tall, skinny ones or short, wide ones, lead to inaccurate force calculations. However, no simulation can have a uniform aspect ratio of 1 or it would be too mathematically complicated to run; instead, we look for ratios ranging between 1 and 10 for good accuracy, 1 and 5 for great accuracy and 1 and 3 for near-perfect accuracy. Another tool you can use is the Energy Norm Error plot, which is a standard stress plot. This result shows where probable errors in the iterations are accumulating and usually coincide with poor mesh; the difference is that this also shows you how the forces are reacting, even in areas with mesh that looks good but is still not refined enough for the amount of energy transfer. The Doctor should realistically always be utilized.

The Reverse-3D Glasses is the tool you use to simplify 3D models into a 2D or even a 1D version that retains their accuracy, while making meshing much, much simpler. Many elements of designs, such as sheet metal, have very thin cross-sections over large spans. Since we have to mesh by the lowest common denominator, making meshes for sheet metal in solid is overly complex. To solve this unnecessary complexity, we have the option to remove a dimension from constant cross-section models and solve only their spans. We also have the option to turn things like beams into 1D models, only solving for length. These assumptions are almost always valid; sheet metal and beams are very often constant cross-sections, and as long as we virtualize it properly, the results will be the same as if it was solid. Also, we have in Sim Pro and above the 2D Simplification tool, which allows us to analyze an entire 3D model as only a 2D cross-section and extrapolate the results; this has the obvious advantage of minimizing mesh complexity. The idea behind it is very similar to the mentality of the Chainsaw, in that if the cross-section is constant, and one slice of it is solved, they really all are solved and you are just repeating the same number crunches over and over.

The Jedi Mind Trick is the tool you use to remove unnecessary parts and replace them with virtual forces. This is different than virtual reality, which deals with things like bolts and other connectors; instead, this is a question of how deep down the rabbit hole do you want to go? For example, we could analyze a design on a laptop satchel to make sure it has a good factor of safety. To do this, we could model the entire satchel, with the laptop, and the person’s shoulder as the strap hangs from it, apply gravity and let it run, but that would take forever to set up and get parameters for. Instead, we can simply run a simulation on one connector, with a fixture, and a force that is close to the force from the scenario above. The cascade model can also be used here. The idea behind the Jedi Mind Trick is to use, for lack of a better term, telekinesis — invisible forces as opposed to complicated contacts and assembly interactions, which will result in the same boundary conditions. Also, I’m aware this is not technically a Jedi Mind Trick (it’s actually Force Move Object or Force Push), but this was a better name. I’m willing to bet you’ll remember it now.

Let’s see some examples of these tools:

Bolted plate

Here we have a simple bolted plate test. We want to know how much force can be applied to that single plate as it is put into tension by a fixture on one side and the plates on the other side tearing it apart. We are assuming the bolts, which are grossly oversized, are not of interest. Having said that, we can use a number of tools on this: the Chainsaw, the Doctor, the Reverse-3D Glasses and the Jedi Mind Trick. The Chainsaw is obvious. We can just cut it in half lengthwise and save on simulation time. We can also take away the thickness of the plate using the Reverse-3D Glasses so we do not have to mesh across the thin cross-section. Lastly, we can eliminate the bolts entirely and just replace them with a force via the Jedi Mind Trick.

Mesh of the bolted plate

You can see how simple this model turns out to be. Notice the symmetry fixture on the edge that is cut; this will make it so results can be extrapolated later and also prevent the model from violating that line of symmetry. Another thing to be wary of when using the Chainsaw is using forces; you have to cut forces in half, as the program will not automatically update like a pressure load would. This is not the case if you use the “Force per Item” option, however, because you’ll have fewer items and thus the same amount less force. As for the Doctor, let’s see a comparison of health versus error.

Checking aspect ratio on a low-quality mesh

Following is a low-quality mesh, with some high aspect ratios. Compare it to the percent error.

High error induced by poor aspect ratios in the mesh elements.

The error plot shows a lot of elements with large errors near that hole. For comparison, our high-quality error looks like the following. Note that the scales are the same, 0 to 15 percent.

Error plot for a higher quality mesh with more appropriate aspect ratio.

Much better. We can trust these stress results because of the low error. As a bonus, the high number of nodes allows us lots of probe points, and thanks to our tricks, the solve time is still only four seconds (the high-quality solid, with mesh one-quarter of this density, took 30 seconds).

Let’s look at a more complicated example.

Thread pull test

In this case, we are interested in seeing if these threads will survive a pull out test. However, this model is not fit for simulation as of now. The threads don’t actually touch each other, and the inside of the female thread has fillets whereas the stud does not, which will cause interference. Let’s use the Transmogrifier tool to help that. It’s not so complicated, really. Just make an FEA configuration.

Adding an FEA configuration

Then change the features and dimensions in any parts you need. In this case, we only need to change one.

Focusing on the right features

Simplifying the threads to 2D

Now that we have our model correctly made for FEA, we will use our Reverse-3D Glasses to make a 2D model, as 3D threads are a real nightmare.

Using the 2D simplification

We use the 2D simplification tool with axi-symmetric selected. This will give us an infinitely thin slice to work with. Now we need to assign no penetration contacts between the teeth; bonded will result in too strong a part to accurately compare it to real life.

Configuring connections

Since the parts are directly touching, we can just set component contacts to global. Let’s see the results from this test.

Results from the 2D simplified mesh

This test looks good. No tooth is at or above yield. However, let’s use our Doctor tool to verify.

Error on the simplified 2D thread mesh

The error in the top and bottom tooth sections is very high, over 25 percent. Clearly, we need more mesh. Let’s look at it again with a fine mesh.

Thread results with a more appropriate mesh

Using this fine mesh, we can see the tip of the bottom tooth is above yield, and the majority of its body is without a good factor of safety. It is very likely this tooth will break, leading to the second tooth becoming the next in line (minus the strength of one tooth), which will also break, and so on. This bolted connection is not safe and is subject to cascade failure. This is a result we did not see in the original and illustrates the importance of a health check in a study.

Error map for the final results

The errors on the tip of the thread are removed (errors on the fixed body and underneath the threaded connection are unimportant).

Now, let’s see an example using all these tools at once.

Reflex engine

This model has a number of built-in interferences due to the hardware. Eventually, we will have to get rid of them, but remember that the Chainsaw should always be your first tool. Reason being . . .

Going to town with the Chainsaw

Now we only have two pins, one bolt and a limited number of interferences to deal with, in addition to the fact that we have less to mesh and define. The interferences are still an issue, and while we could eliminate all of them, we should try to virtualize using Virtual Reality as much as possible. Let’s start with those bolts.

Replacing bolts with a virtual connector

This bolt is now suppressed and replaced with a virtual connector. In SOLIDWORKS Simulation 2015 and above, this can be done automatically by right-clicking the Connections folder and selecting Toolbox Fasteners to Bolts. This eliminates all the interferences the bolt was causing, as well as includes the ability to add preload (something not possible in static analysis without virtualization).

Setting up virtual fasteners

The pins are defined in a similar fashion. Here, I virtualized their stiffness and resistance to movement (they have infinite translation resistance but 50 N*m/rad rotation). That takes care of the fasteners. Now let’s fix the body. Just like before, we’ll make a configuration and adjust dimensions.

Configuration for the body

More configuration setup

This also applies to subassemblies.

Taking care of the shaft

Interferences eliminated

Transmogrification complete. Now to reduce as many thicknesses as possible, use Reverse-3D Glasses.

Mesh of the reflex engine

Notice we did not make one of the blocks a shell. That’s because if you check the above screenshot, you will see the plug part fits into a recess. That recess can’t be modeled with shells (everything has to be constant, remember), so we bite the bullet and run it as a solid. As opposed to putting in complicated pressure loads from flow on the inside of the pipe, instead, we will use thermal expansion to control the displacements from a worst-case scenario.

Calculated deformations for the reflex engine

Here’s our super-deformed model with displacements. Let’s do a health check using the Doctor.The Doctor visits the reflex engine mesh

Our shell mesh looks mostly good, but some elements in that plug are very bad. However, this is acceptable. The reason why is that plug is significantly far away from the areas of large displacement, and in reality, we could probably get rid of it entirely. (It does have heat load applied to it; switch the heat load instead to the faces it directly touches — there’s our example of the Jedi Mind Trick.) We kept it in this case because it has the other hole for the bolt and thus is necessary for our pre-load.

Losing what’s not critical to the analysis

Our error is low. Lastly, thanks to virtualization, we can get results from those pins.Final results on the reflex engine

This is a result that is not easy to get from other studies. It can even predict failure from a factor of safety criteria. This type of operation we just performed is typical for simulation engineers, and these tools along with practice will help you think just like they do about how a problem should be handled in FEA. These are the tools you’re looking for.

About the Author

Michael Kalin has been teaching simulation since 2012. He regularly does presentations for simulation at conventions such as SOLIDWORKS World and SOLIDWORKS User Groups. In his off time, he enjoys building his own 3D printers, playing Shogi, traditional archery and Ghostbusting.

How to Add Topology Optimization to SOLIDWORKS?

ParetoWorks is a SOLIDWORKS add-in that allows engineers to perform topology optimizations on their parts based on stiffness or strength. This software uses simulation and optimization algorithms to lightweight parts without sacrificing the structural integrity of the parts.

ParetoWorks can automate the lightweighting optimization of a part based on stiffness and strength. (All images courtesy of SOLIDWORKS and SciArt.)

The software imports the SOLIDWORKS geometry as an STL file. The program then runs a finite element analysis (FEA) solver and a design optimization engine to give engineers an idea of how to reduce the weight of a part. Though ParetoWorks operates within the SOLIDWORKS framework, it is also a cloud technology available through a browser.

“Design optimization lies at the heart of modern engineering,” said Krishnan Suresh, mechanical engineering professor and CTO of SciArt, makers of ParetoWorks. “It is critical in reducing cost, reducing material, reducing weight and increasing quality, and is a driving force behind innovation. [However], design optimization can be very tricky and difficult for humans to carry out manually.”

To set up the problem, the user needs to input the units of the system, any boundary conditions, the limiting variable for optimization (stiffness or strength) and the forces the part will experience. All of these inputs are made in a simplified field of entry.

“[ParetoWorks’] focus is to make sure these structural loads are done right,” said Praveen Yadav, director of engineering at SciArt, makers of ParetoWorks. “We have the capability of handling thermomechanical loading, transient loading, modal analysis and buckling analysis. We include all of these analyses in the optimization for multi-constrained, multi-material and multi-load optimizations.”

The optimizations can also take constraints into consideration when assessing the part. Some of these constraints include:

• Maximum volume fraction
• Stiffness and displacement constraints
• Manufacturing constraints like casting draw direction
• Assembly constraints like which surfaces to maintain

The Benefits of Subtractive Topology Optimization to Additive Topology Optimization

ParetoWorks isn’t the only topology optimization software out there. However, many of them are based on additive optimization of the part as opposed to subtractive optimizations.

Though additive can give engineers a good starting point for a part based on a design space and loads, it does take a lot of data to perform this optimization. Subtractive optimization, however, requires less data but it will need to start with a part before the optimization can be performed.

Instead of mapping the whole design space, ParetoWorks uses subtractive optimization to modify the geometry, saving data costs.

“[Additive optimizations] try to map out the entire design space, this requires the storage of a lot of data, which gets expensive as you get new designs and you compare to the existing stored variable,” said Yadav. “ParetoWorks, on the other hand, attempts to stay as close as possible to the optimality front. This reduces the requirement of storing data.”

“All we care about is where we are right now and where we are headed,” Yadav clarified. “Based on that, we can choose a suitable search direction and make small increments to update the geometry. Once the geometry is updated we also perform fixed-point filtration to make sure it is robust and stable in that region.”

Since the entire design space isn’t mapped out, engineers might wonder how ParetoWorks handles the constraints. When performing this optimization, if the part hits a constraint made by the engineer, the software will reassess the step size for subsequent iterations in the optimization. This will slow down the changes made to the part and allow for a more detailed localized search for the best design in that region.

For more on ParetoWorks, read this ENGINEERING.com article. To learn more about structural optimizations using simulation, follow this link.

About the Author

Shawn Wasserman (@ShawnWasserman) is the Internet of Things (IoT) and Simulation Editor at ENGINEERING.com. He is passionate about ensuring engineers make the right decisions when using computer-aided engineering (CAE) software and IoT development tools. Shawn has a Masters in Bio-Engineering from the University of Guelph and a BASc in Chemical Engineering from the University of Waterloo.