Key Process Phenomena in the Laser Fusion of Metals

Metal 3D printing involves a combination of complex interacting phenomena at a range of length and time scales. In this blog post, I discuss three of these that lie at the core of the laser fusion of metals: phase changes, residual stresses and solidification structure (see Figure 1). I describe each phenomenon briefly and then why understanding it matters. In future posts I will dive deeper into each one of these areas and review what work is being done to advance our understanding of them.

Fig. 1 Schematic showing the process of laser fusion of metals and the four key phenomena of phase changes, melt pool behavior, thermomechanical effects and microstructure evolution
Fig. 1 Schematic showing the process of laser fusion of metals and the three key phenomena of phase changes, residual stresses and solidification structure

Phase Changes

Phases and the mechanisms by which they transition from one to the other
Fig. 2 Phases and the mechanisms by which they transition

Phase changes describe the transition from one phase to another, as shown in Figure 2. All phases are present in the process of laser fusion of metals. Metal in powder form (solid) is heated by means of a laser beam with spot sizes on the order of tens of microns. The powder then melts to form a melt pool (liquid) and then solidifies to form a portion of a layer of the final part (solid). During this process, there is visible gas and smoke, some of which ionizes to plasma.

The transition from powder to melt pool to solid part, as shown in Figure 3, is the essence of this process and understanding this is of vital importance. For example, if the laser fluence is too high, defects such as balling or discontinuous welds are possible and for low laser fluence, a full melt may not be obtained and thus lead to voids. Selecting the right laser, material and build parameters is thus essential to optimize the size and depth of the liquid melt pool, which in turn governs the density and structure of the final part. Finally, and this is more true of high power lasers, excessive gas and plasma generation can interfere with the incident laser fluence to reduce its effectiveness.

Primary phase changes from powder to melt pool to solid part
Fig. 3 Primary phase changes from powder to melt pool to solid part

Residual Stresses

Residual stresses are stresses that exist in a structure after it reaches equilibrium with its environment. In the laser metal fusion process, residual stresses arise due to two related mechanisms [Mercelis & Kruth, 2006]:

  • Thermal Gradient: A steep temperature gradient develops during laser heating, with higher temperatures on the surface driving expansion against the cooler underlying layers and thereby introducing thermal stresses that could lead to plastic deformation.
  • Volume Shrinkage: Shrinkage in volume in the laser metal fusion process occurs due to several reasons: shrinkage from a powder to a liquid, shrinkage as the liquid itself cools, shrinkage during phase transition from liquid to solid and final shrinkage as the solid itself cools. These shrinkage events occur to a greater extent at the top layer, and reduce as one goes to lower layers.
Fig. 4 Residual stresses resulting from thermal gradients and volume changes
Fig. 4 Residual stresses resulting from thermal gradients and volume changes

After cooling, these two mechanisms together have the effect of creating compressive stresses on the top layers of the part, and tensile stresses on the bottom layers as shown in Figure 4. Since parts are held down by supports, these stresses could have the effect of peeling off supports from the build plate, or breaking off the supports from the part itself as shown in Figure 4. Thus, managing residual stresses is essential to ensuring a built part stays secured on the base plate and also for minimizing the amount of supports needed. A range of strategies are employed to mitigate residual stresses including laser rastering strategies, heated build plates and post-process thermal stress-relieving.

Solidification Structure

Solidification structure refers to the material structure of the resulting part that arises due to the solidification of the metal from a molten state, as is accomplished in the laser fusion of metals. It is well known that the structure of a metal alloy strongly influences its properties and further, that solidification process history has a strong influence on this structure, as does any post processing such as a thermal exposure. The wide range of materials and processing equipment in the laser metal fusion process makes it challenging to develop a cohesive theory on the nature of structure for these metals, but one approach is to study this on four length scales as shown in Figure 5. As an example, I have summarized the current understanding of each of these structures specifically for Ti-6Al-4V, which is one of the more popular alloys used in metal additive manufacturing. Of greatest interest are the macro-, meso- and microstructure, all of which influence mechanical properties of the final part. Understanding the nature of this structure, and correlating it to measured properties is a key step in certifying these materials and structures for end-use application.

FIg. 5 Four levels of solidification structure and the typical observations for Ti-6Al-4V
FIg. 5 Four levels of solidification structure and the typical observations for Ti-6Al-4V

Discussion

Phase changes, residual stresses and solidification structure are three areas where an understanding of the fundamentals is crucial to solve problems and explore new opportunities that can accelerate the adoption of metal additive manufacturing. Over the past decade, most of this work has been, and continues to be, experimental in nature. However, in the last few years, progress has been made in deriving this understanding through simulation, but significant challenges remain, making this an exciting area of research in additive manufacturing to watch in the coming years.

References

  1. Mercelis, P., & Kruth, J. (2006). Residual stresses in selective laser sintering and selective laser melting. Rapid Prototyping Journal, 12(5), 254-265.
  2. Simonelli, M., Tse, Y.Y., Tuck, C., (2012) Further Understanding of Ti-6Al-4V selective laser melting using texture analysis, SFF Symposium
  3. King, W. E. and Anderson, A. T. and Ferencz, R. M. and Hodge, N. E. and Kamath, C. and Khairallah, S. A. and Rubenchik, A. M., (2015) Laser powder bed fusion additive manufacturing of metals; physics, computational, and materials challenges, Applied Physics Reviews, 2, 041304

Constitutive Modeling of 3D Printed FDM Parts: Part 2 (Approaches)

In part 1 of this two-part post, I reviewed the challenges in the constitutive modeling of 3D printed parts using the Fused Deposition Modeling (FDM) process. In this second part, I discuss some of the approaches that may be used to enable analyses of FDM parts even in presence of these challenges. I present them below in increasing order of the detail captured by the model.

  • Conservative Value: The simplest method is to represent the material with an isotropic material model using the most conservative value of the 3 directions specified in the material datasheet, such as the one from Stratasys shown below for ULTEM-9085 showing the lower of the two modulii selected. The conservative value can be selected based on the desired risk assessment (e.g. lower modulus if maximum deflection is the key concern). This simplification brings with it a few problems:
    • The material property reported is only good for the specific build parameters, stacking and layer thickness used in the creation of the samples used to collect the data
    • This gives no insight into build orientation or processing conditions that can be improved and as such has limited value to an anlayst seeking to use simulation to improve part design and performance
    • Finally, in terms of failure prediction, the conservative value approach disregards inter-layer effects and defects described in the previous blog post and is not recommended to be used for this reason
ULTEM-9085 datasheet from Stratasys - selecting the conservative value is the easiest way to enable preliminary analysis
ULTEM-9085 datasheet from Stratasys – selecting the conservative value is the easiest way to enable preliminary analysis
  • Orthotropic Properties: A significant improvement from an isotropic assumption is to develop a constitutive model with orthotropic properties, which has properties defined in all three directions. Solid mechanicians will recognize the equation below as the compliance matrix representation of the Hooke’s Law for an orthortropic material, with the strain matrix on the left equal to the compliance matrix by the stress matrix on the right. The large compliance matrix in the middle is composed of three elastic modulii (E), Poisson’s ratios (v) and shear modulii (G) that need to be determined experimentally.
Hooke's Law for Orthotropic Materials (Compliance Form)
Hooke’s Law for Orthotropic Materials (Compliance Form)

Good agreement between numerical and experimental results can be achieved using orthotropic properties when the structures being modeled are simple rectangular structures with uniaxial loading states. In addition to require extensive testing to collect this data set (as shown in this 2007 Master’s thesis), this approach does have a few limitations. Like the isotropic assumption, it is only valid for the specific set of build parameters that were used to manufacture the test samples from which the data was initially obtained. Additionally, since the model has no explicit sense of layers and inter-layer effects, it is unlikely to perform well at stresses leading up to failure, especially for complex loading conditions.  This was shown in a 2010 paper that demonstrated these limitations  in the analysis of a bracket that itself was built in three different orientations. The authors concluded however that there was good agreement at low loads and deflections for all build directions, and that the margin of error as load increased varied across the three build orientations.

An FDM bracket modeled with Orthotropic properties compared to experimentally observed results
An FDM bracket modeled with Orthotropic properties compared to experimentally observed results
  • Laminar Composite Theory: The FDM process results in structures that are very similar to laminar composites, with a stack of plies consisting of individual fibers/filaments laid down next to each other. The only difference is the absence of a matrix binder – in the FDM process, the filaments fuse with neighboring filaments to form a meso-structure. As shown in this 2014 project report, a laminar approach allows one to model different ply raster angles that are not possible with the orthotropic approach. This is exciting because it could expand insight into optimizing raster angles for optimum performance of a part, and in theory reduce the experimental datasets needed to develop models. At this time however, there is very limited data validating predicted values against experiments. ANSYS and other software that have been designed for composite modeling (see image below from ANSYS Composite PrepPost) can be used as starting points to explore this space.
Schematic of a laminate build-up as analyzed in ANSYS Composite PrepPost
Schematic of a laminate build-up as analyzed in ANSYS Composite PrepPost
  • Hybrid Tool-path Composite Representation: One of the limitations of the above approach is that it does not model any of the details within the layer. As we saw in part 1 of this post, each layer is composed of tool-paths that leave behind voids and curvature errors that could be significant in simulation, particularly in failure modeling. Perhaps the most promising approach to modeling FDM parts is to explicitly link tool-path information in the build software to the analysis software. Coupling this with existing composite simulation is another potential idea that would help reduce computational expense. This is an idea I have captured below in the schematic that shows one possible way this could be done, using ANSYS Composite PrepPost as an example platform.
Potential approach to blending toolpath information with composite analysis software
Potential approach to blending toolpath information with composite analysis software

Discussion: At the present moment, the orthotropic approach is perhaps the most appropriate method for modeling parts since it is allows some level of build orientation optimization, as well as for meaningful design comparisons and comparison to bulk properties one may expect from alternative technologies such as injection molding. However, as the application of FDM in end-use parts increases, the demands on simulation are also likely to increase, one of which will involve representing these materials more accurately than continuum solids.

Constitutive Modeling of 3D Printed FDM Parts: Part 1 (Challenges)

As I showed in a prior blog post, Fused Deposition Modeling (FDM) is increasingly being used to make functional plastic parts in the aerospace industry. All functional parts have an expected performance that they must sustain during their lifetime. Ensuring this performance is attained is crucial for aerospace components, but important in all applications. Finite Element Analysis (FEA) is an important predictor of part performance in a wide range of indusrties, but this is not straightforward for the simulation of FDM parts due to difficulties in accurately representing the material behavior in a constitutive model. In part 1 of this article, I list some of the challenges in the development of constitutive models for FDM parts. In part 2, I will discuss possible approaches to addressing these challenges while developing constitutive models that offer some value to the analyst.

It helps to first take a look at the fundamental multi-scale structure of an FDM part. A 2002 paper by Li et. al. details the multi-scale structure of an FDM part as it is built up from individually deposited filaments all the way to a three-dimensional part as shown in the image below.

Multiscale structure of an FDM part
Multiscale structure of an FDM part

This multi-scale structure, and the deposition process inherent to FDM, make for 4 challenges that need to be accounted for in any constitutive modeling effort.

  • Anisotropy: The first challenge is clear from the above image – FDM parts have different structure depending on which direction you look at the part from. Their layered structure is more akin to composites than traditional plastics from injection molding. For ULTEM-9085, which is one of the high temperature polymers available from Stratasys, the datasheets clearly show a difference in properties depending on the orientation the part was built in, as seen in the table below with some select mechanical properties.
Stratasys ULTEM 9085 datasheet material properties showing anisotropy
Stratasys ULTEM 9085 datasheet material properties showing anisotropy
  • Toolpath Definition: In addition to the variation in material properties that arise from the layered approach in the FDM process, there is significant variation possible within a layer in terms of how toolpaths are defined: this is essentially the layout of how the filament is deposited. Specifically, there are at least 4 parameters in a layer as shown in the image below (filament width, raster to raster air gap, perimeter to raster air gap and the raster angle). I compiled data from two sources (Stratasys’ data sheet and a 2011 paper by Bagsik et al that show how for ULTEM 9085, the Ultimate Tensile Strength varies as a function of not just build orientation, but also as a function of the parameter settings – the yellow bars show the best condition the authors were able to achieve against the orange and gray bars that represent the default settings in the tool.  The blue bar represents the value reported for injection molded ULTEM 9085.
Ultimate Tensile Strength of FDM ULTEM 9085 for three different build orientations, compared to injection molded value (84 MPa) for two different data sources, and two different process parameter settings from the same source. On the right are shown the different orientations and process parameters varied.
Ultimate Tensile Strength of FDM ULTEM 9085 for three different build orientations, compared to injection molded value (84 MPa) for two different data sources, and two different process parameter settings from the same source. On the right are shown the different orientations and process parameters varied.
  • Layer Thickness: Most FDM tools offer a range of layer thicknesses, typical values ranging from 0.005″ to 0.013″. It is well known that thicker layers have greater strength than thinner ones. Thinner layers are generally used when finer feature detail or smoother surfaces are prioritized over out-of-plane strength of the part. In fact, Stratasys’s values above are specified for the default 0.010″ thickness layer only.
  • Defects: Like all manufacturing processes, improper material and machine performance and setup and other conditions may lead to process defects, but those are not ones that constitutive models typically account for. Additionally and somewhat unique to 3D printing technologies, interactions of build sheet and support structures can also influence properties, though there is little understanding of how significant these are. There are additional defects that arise from purely geometric limitations of the FDM process, and may influence properties of parts, particularly relating to crack initiation and propagation. These were classified by Huang in a 2014 Ph.D. thesis as surface and internal defects.
    • Surface defects include the staircase error shown below, but can also come from curve-approximation errors in the originating STL file.
    • Internal defects include voids just inside the perimeter (at the contour-raster intersection) as well as within rasters. Voids around the perimeter occur either due to normal raster curvature or are attributable to raster discontinuities.
FDM Defects: Staircase error (top), Internal defects (bottom)
FDM Defects: Staircase error (top), Internal defects (bottom)

Thus, any constitutive model for FDM that is to accurately predict a part’s response needs to account for its anisotropy, be informed by the specifics of the process parameters that were involved in creating the part and ensure that geometric non-idealities are comprehended or shown to be insignificant. In my next blog post, I will describe a few ways these challenges can be addressed, along with the pros and cons of each approach.

Click here to see part 2 of this post

7 Reasons why ANSYS AIM Will Change the Way Simulation is Done

ANSYS-AIM-Icon1When ANSYS, Inc. released their ANSYS AIM product they didn’t just introduce a better way to do simulation, they introduced a tool that will change the way we all do simulation.  A bold statement, but after PADT has used the tool here, and worked with customers who are using it, we feel confident that this is a software package will drive that level of change.   It enables the type of change that will drive down schedule time and cost for product development, and allow companies to use simulation more effectively to drive their product development towards better performance and robustness.

It’s Time for a Productivity Increase

AIM-7-old-modelIf you have been doing simulation as long as I have (29 years for me) you have heard it before. And sometimes it was true.  GUI’s on solvers was the first big change I saw. Then came robust 3D tetrahedral meshing, which we coasted on for a while until fully associative and parametric CAD connections made another giant step forward in productivity and simulation accuracy. Then more recently, robust CFD meshing of dirty geometry. And of course HPC improvements on the solver side.

That was then.  Right now everyone is happily working away in their tool of choice, simulating their physics of choice.  ANSYS Mechanical for structural, ANSYS Fluent for fluids, and maybe ANSYS HFSS for electromagnetics. Insert your tool of choice, it doesn’t really matter. They are all best-in-breed advanced tools for doing a certain type of physical simulation.  Most users are actually pretty happy. But if you talk to their managers or methods engineers, you find less happiness. Why? They want more engineers to have access to these great tools and they also want people to be working together more with less specialization.

Putting it all Together in One Place

AIM-7-valve2-multiphysicsANSYS AIM is, among many other things, an answer to this need.  Instead of one new way of doing something or a new breakthrough feature, it is more of a product that puts everything together to deliver a step change in productivity. It is built on top of these same world class best-in-bread solvers. But from the ground up it is an environment that enables productivity, processes, ease-of-use, collaboration, and automation. All in one tool, with one interface.

Changing the Way Simulation is Done

Before we list where we see things changing, let’s repeat that list of what AIM brings to the table, because those key deliverables in the software are what are driving the change:

  • IAIM-7-pipe-setupmproved Productivity
  • Standardized Processes
  • True Ease-of-Use
  • Inherent Collaboration
  • Intuitive Automation
  • Single Interface

Each of these on their own would be good, but together, they allow a fundamental shift in how a simulation tool can be used. And here are the seven way we predict you will be doing things differently.

1) Standardized processes across an organization

The workflow in ANSYS AIM is process oriented from the beginning, which is a key step in standardizing processes.  This is amplified by tools that allow users, not just programmers, to create templates, capturing the preferred steps for a given type of simulation.  Others have tried this in the past, but the workflows were either too rigid or not able to capture complex simulations.  This experience was used to make sure the same thing does not happen in ANSYS AIM.

2) No more “good enough” simulation done by Design Engineers

Ease of use and training issue has kept robust simulation tools out of the hands of design engineers.  Programs for that group of users have usually been so watered down or lack so much functionality, that they simply deliver a quick answer. The math is the same, but it is not as detailed or accurate.  ANSYS AIM solves this by give the design engineer a tool they can pick up and use, but that also gives them access to the most capable solvers on the market.

3) Multiphysics by one user

Multiphysics simulation often involves the use of multiple simulation tools.  Say a CFD Solver and a Thermal Solver. The problem is that very few users have the time to learn two or more tools, and to learn how to hook them together. So some Multiphysics is done with several experts working together, some in tools that do multiple physics, but none well, or by a rare expert that has multi-tool expertise.  Because ANSYS AIM is a Multiphysics tool from the ground up, built on high-power physics solvers, the limitations go away and almost any engineer can now do Multiphysics simulation.

AIM-7-study4) True collaboration

The issues discussed above about Multiphysics requiring multiple users in most tools, also inhibit true collaboration. Using one user’s model in one tool is difficult when another user has another tool. Collaboration is difficult when so much is different in processes as well.  The workflow-driven approach in ANSYS AIM lends itself to collaboration, and the consistent look-and-feel makes it happen.

5) Enables use when you need it

This is a huge one.  Many engineers do not use simulation tools because they are occasional users.  They feel that the time required to re-familiarize themselves with their tools is longer than it takes to do the simulation. The combination of features unique to ANSYS AIM deal with this in an effective manner, making accurate simulation something a user can pick up when they need it, use it to drive their design, and move on to the next task.

6) Stepping away from CAD embedded Simulation

The growth of CAD embedded simulation tools, programs that are built into a CAD product, has been driven by the need to tightly integrate with geometry and provide ease of use for the users who only occasionally need to do simulation. Although the geometry integration was solved years ago, the ease-of-use and process control needed is only now becoming available in a dedicated simulation tool with ANSYS AIM.

7) A Return to home-grown automation for simulation

AIM-7-scriptIf you have been doing simulation since the 80’s like I have, you probably remember a day when every company had scripts and tools they used to automate their simulation process. They were extremely powerful and delivered huge productivity gains. But as tools got more powerful and user interfaces became more mature, the ability to create your own automation tools faded.  You needed to be a programmer. ANSYS AIM brings this back with recording and scripting for every feature in the tool, with a common and easy to use language, Python.

How does this Impact Me and or my Company?

It is kind of fun to play prognosticator and try and figure out how a revolutionary advance in our industry is going to impact that industry. But in the end it really does not matter unless the changes improve the product development process. We feel pretty strongly that it does.  Because of the changes in how simulation is done, brought about by ANSYS AIM, we feel that more companies will use simulation to drive their product development, more users within a company will have access to those tools, and the impact of simulation will be greater.

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To fully grasp the impact you need to step back and ponder why you do simulation.  The fast cars and crazy parties are just gravy. The core reason is to quickly and effectively test your designs.  By using virtual testing, you can explore how your product behaves early in the design process and answer those questions that always come up.  The sooner, faster, and more accurately you answer those questions, the lower the cost of your product development and the better your final product.

Along comes a product like ANSYS AIM.  It is designed by the largest simulation software company in the world to give the users of today and tomorrow access to the power they need. It enables that “sooner, faster, and more accurately” by allowing us to change, for the better, the way we do virtual testing.

The best way to see this for yourself is to explore ANSYS AIM.  Sign up for our AIM Resource Kit here or contact us and we will be more than happy to show it to you.

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Free ANSYS AIM Resource Kit — Expert Advice, Insights and Best Practices for Multiphysics Simulation

ANSYS-AIM-Icon1We have been talking a lot about ANSYS AIM lately.  Mostly because we really like ANSYS AIM and we think a large number of engineers out there need to know more about it and understand it’s advantages.  And the way we do that is through blog posts, emails, seminars, and training sessions.  A new tool that we have started using are “Resource and Productivity Kits,” collections of information that users can download.

Earlier in the year we introduced several kits, including ANSYS Structural, ANSYS Fluids, and ANSYS ElectroMechanical.  Now we are pleased to offer up a collection of useful information on ANSYS AIM.  This kit includes:

  • “Getting to know ANSYS AIM,” a video by PADT application engineer Manoj Mahendran
  • “What I like about ANSYS AIM,” a video featuring insights on the tool
  • Six ANSYS AIM demonstration videos, including simulations and a custom template demonstration
  • Five slide decks that provide an overview of ANSYS AIM and describe its new features
  • An exclusive whitepaper on effectively training product development engineers in simulation.

You can download the kit here.

If you need more info, view the ANSYS AIM Overview video or read about it on our ANSYS AIM page.

Watch this blog for more useful content on AIM in the future.


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Presentation: Leveraging Simulation for Product Development of IoT Devices

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Yours truly going over the impact of Simulation on IoT Product Development

The local SEMI chapter here in Arizona held a breakfast meeting on Monetizing Internet of Things (IoT) and PADT was pleased to be one of the presenters. Always a smart group, this was a chance to sit with people making the sensors, chips, and software that enable the IoT and dig deep in to where things are and where they need to be.

The event was hosted by one of our favorite customers, and neighbor right across the street, Freescale Semiconductor.  Speakers included IoT experts from Freescale, Intel, Medtronics, ASU, and SEMICO Research.

Not surprisingly I talked about how Simulation can play a successful role in product development of IoT devices.

You can download a copy of the presentation here: PADT-SEMI-IOT-Simulation-1.pdf

UPDATE (11/9/2015): Great write-up by Don Dingee on this event in the SemiWiki. Click here to read it. It includes a great summary of the other speakers.

You can also see more details on how people use Simulation for this application on the ANSYS, Inc. website here.  We also like this video from ANSYS that shows some great applications and how ANSYS is used with them:

A couple of common themes resonated across the speakers:

  1. Price and size need to come down on the chips used in IoT (this was a semiconductor group, so this is a big part of their focus)
  2. Lowering power usage and increasing power density in batteries is a key driver
  3. The biggest issue in IoT is privacy and security. Keeping your data private and keeping people from hacking in to IoT devices.
  4. Another big problem is dealing with all the data collected by IoT devices. How to make it useful and how to store it all.  One answer is reducing the data on the device, another is only keeping track of what changes.
  5. It is early, standards are needed but they are still forming.

If you look at this list, the first two problems are addressable with simulation:

SEMI-AZ-IoT-2

PADT has a growing amount of experience with helping customers simulate and design IoT devices as well as the chips, sensors, and antenna that go in to IoT devices.  To learn more, shoot us an email at info@padtinc.com or call 480.813.4884.

 

Free Training and Evaluation for ANSYS AIM

AIM_City_CFDPADT is hosting a series of free training classes to introduce users to ANSYS AIM.  We have pasted the invitation below.  You can register here.  We are very excited about this new tool from ANSYS, Inc. and are eager to share it with everyone. Look for more AIM information on this blog in the near future.

Free Training and Evaluation for ANSYS® AIM™.
Register Today – Seats Are Limited.

Discover how to design your next product
better… and faster

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ANSYS AIM: Integrated Multiphysics Simulation Environment
for All Engineers

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Free Training and Evaluation for ANSYS® AIM™ – An Integrated Multi-physics Simulation Environment for All Engineers

As a special offer, PADT Inc. is offering FREE “Jump Start” training and hands-on evaluation for ANSYS® AIM™. Design engineers, method engineers and managers seeking to learn the latest simulation software, boost adoption and usability for the occasional user, or extend their existing CAD-based tool’s limited functionality will benefit from this no-obligation course.

Register Today – Seats are limited and will be filled on a first-come, first-served basis. On completion of the class, you’ll be qualified to receive and use a FREE 30-day ANSYS AIM download for evaluation.

All classes will be held from 9:00 a.m. – 4:00 p.m. local time and include a complimentary lunch.

PADT’s support team of ANSYS experts will help attendees understand where ANSYS AIM fits in to their organization and workflow. The class will address both situations and how ANSYS AIM provides the integration of CAD based systems and the ease of use of a modern tool in a product that steps the occasional user through the process without limiting functionality.

Watch this short video to learn more about the capabilities and benefits of ANSYS® AIM™ for the simulation of 3-D physics and multiphysics

Contact our ANSYS experts 1-800-293-PADT, info@padtinc.com

CoresOnDemand: Helping Engineers Do Their Magic

CoresOnDemand-Logo-120hEngineers Do Magic

In the world of simulation there are two facts of life. First, the deadline of “yesterday would be good” is not too uncommon. Funding deadlines, product roll-out dates, as well as unexpected project requirements are all reliable sources for last minute changes. Engineers are required to do quality work and deliver reliable results in limited time and resources. In essence perform sorcery.

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Second, the size and complexity of models can vary wildly. Anything from fasteners and gaskets to complete systems or structures can be in the pipeline. Engineers can be looking at any combination of hundreds of variables that impact the resources required for a successful simulation.

Required CPU cores, RAM per core, interconnect speeds, available disk space, operating system and ANSYS version all vary depending on the model files, simulation type, size, run-time and target date for the results.

Engineers usually do magic. But sometimes limited time or resources that are out of reach can delay on-time delivery of project tasks.

At PADT, We Can Help

PADT Inc. has been nostrils deep in engineering services and simulation products for over 20 years. We know engineering, we know how to simulate engineering and we know ANSYS very well. To address the challenges our customers are facing, in 2015 PADT introduced CoresOnDemand to the engineering community.

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CoresOnDemand offers the combination of our proven CUBE cluster, ANSYS simulation tools and the PADT experience and support as an on demand simulation resource. By focusing on the specific needs of ANSYS users, CoresOnDemand was built to deliver performance and flexibility for the full range of applications. Specifics about the clusters and their configurations can be found at CoresOnDemand.com.

CoresOnDemand is a high performance computing environment purpose built to help customers address numerical simulation needs that require compute power that isn’t available or that is needed on a temporary basis.

Call Us We’re Nice

CoresOnDemand is a new service in the world of on-demand computing. Prospective customers just need to give us a call or send us an inquiry here to get all of their questions answered. The engineers behind CoresOnDemand have a deep understanding of the ANSYS tools and distributed computing and are able to asses and properly size a compute environment that matches the needed resources.

Call us we’re nice!

Two Halves of the Nutshell

The process for executing a lease on a CoresOnDemand cluster is quite straight forward. There are two parts to a lease:

PART 1: How many cores & how long is the lease for?

By working with the PADT engineers – and possibly benchmarking their models – customers can set a realistic estimate on how many cores are required and how long their models need to run on the CoresOnDemand clusters. Normally, leases are in one-week blocks with incentives for longer or regular lease requirements.

Clusters are leased in one-week blocks, but we’re flexible.

Part 2: How will ANSYS be licensed?

An ANSYS license is required in order to run on the CoresOnDemand environment.  A license lease can be generated by contacting any ANSYS channel partner. PADT can generate license leases in Arizona, Colorado, New Mexico, Utah & Nevada. Licenses can also be borrowed from the customer’s existing license pool.

An ANSYS license may be leased from an ANSYS channel partner or borrowed from customer’s existing license pool.

Using the Cluster

Once the CoresOnDemand team has completed the cluster setup and user creation (takes a couple of hours for most cases), customers can login and begin using the cluster. The CoresOnDemand clusters allow customers to use the connection method they are comfortable with. All connections to CoresOnDemand are encrypted and are protected by a firewall and an isolated network environment.

Step 1: Transfer files to the cluster:

Files can be transferred to the cluster using Secure Copy Protocol which creates an encrypted tunnel for copying files. A graphical tool is also available for Windows users (& it’s freeJ). Also, larger files can be loaded to the cluster manually by sending a DVD, Blu-ray disk or external storage device to PADT. The CoresOnDemand team will mount the volume and can assist in the copying of data.

Step 2: Connect to the cluster and start jobs

Customers can connect to the cluster through an SSH connection. This is the most basic interface where users can launch interactive or batch processing jobs on the cluster. SSH is secure, fast and very stable. The downside of SSH is that is has limited graphical capabilities.

Another option is to use the Nice Software Desktop Cloud Visualization (DCV) interface. DCV provides enhanced interactive 2D/3D access over a standard network. It enables users to access the cluster from anywhere on virtually any device with a screen and an internet connection. The main advantage of DCV is the ability to start interactive ANSYS jobs and monitor them without the need for a continuous connection. For example, a user can connect from his laptop to launch the job and later use his iPad to monitor the progress.

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Figure 1. 12 Million cell model simulated on CoresOnDemand

The CoresOnDemand environment also has the Torque resource manager implemented where customers can submit multiple jobs to a job queue and run them in sequence without any manual intervention.

Customers can use SCP or ship external storage to get data on the cluster. SSH or DCV can be used to access the cluster. Batch, interactive or Torque scheduler can be used to submit and monitor jobs.

All Done?

Once the simulation runs are completed customers usually choose one of two methods to transfer data back. First is to download the results over the internet using SCP (mentioned earlier) or have external media shipped back (External media can be encrypted if needed).

After the customer receives the data and confirms that all useful data was recovered from the cluster, CoresOnDemand engineers re-image the cluster to remove all user data, user accounts and logs. This marks the end of the lease engagement and customers can rest assured that CoresOnDemand is available to help…and it’s pretty fast too.

At the end of the lease customers can download their data or have it shipped on external media. The cluster is later re-imaged and all user data, accounts & logs are also deleted in preparation for the next customer.

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ANSYS Launches Free Student Version

ansys-student-1This week ANSYS, Inc. made a fantastic announcement that has been in the works for a while, and that we think will greatly benefit the simulation community:  A free ANSYS Student product.  This is an introductory product that is focused on students who are learning the fundamentals of simulation who also want to learn the full power and capability of the ANSYS product suite.  It includes ANSYS® Multiphysics™ , ANSYS® CFD™ , ANSYS® Autodyn®, ANSYS® Workbench™, ANSYS® DesignModeler™and ANSYS®DesignXplorer™

Yes you read that right, all of the flagship products for free. No features or capabilities are turned off. It is the exact same software as the commercial product, but the size of problems that you can solve is limited.  It runs on MS Windows. Perfect for students.

PADT is excited about this because it gives students access to the ability to learn FEA and CFD simulation with the world’s most popular and capable simulation tool, without running in to brick walls. Want to do a flat plate with a hole in it? No Problem. Want to model fluid-solid-interaction on a flexible membrane valve? No Problem.  Want to model explosive forming? No Problem.  Want to model combustion with complex turbulence? No problem.

All in the same interface as students will use when they enter the work force or do research at University.

This is great news and we can’t wait to see what schools and students do with this access.

How to Get It – The New Academic Web Pages

The previous Student Portal is being replaced with an Academic Web area on the ansys.com site: ansys.com/academic.

Go to the ANSYS Student site to learn more about ANSYS Student and how to download your copy. These same pages will have resources to help you learn and understand the product.

The “Pictures”

Let me state categorically that PADT was not consulted on the image that ANSYS, Inc. used for the “student” user that was so happy to find out that there is now a free version of the ANSYS software suite.  Here is their picture:

ANSYS-student-version We would have preferred something like this:

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Just kidding. We were happy to see this product come out and thought the picture was hilarious.  In all seriousness, we will also plug the  recent #ilooklikeanengineer twitter hash tag , highlighting the diversity of female engineers. that was awesome and we would love to see more chances for engineers to show their true selves.

 

Major Enhancements in FLOWNEX 2015: Combustors, Importers, and Pipes

FlownexLogo_OfficialSimulation has revolutionized flow and heat transfer dependent systems over the past decades by minimizing costly physical testing and accelerating time to operation around the world. But for many companies, such simulation has largely focused on components and proved to be very time consuming. The technology advancements delivered by Flownex SE now offer a fast, reliable, and accurate total system and subsystem approach to simulation.

FLOWNEX-2015-ICONS

With the release of FLOWNEX 2015, users now have access to advanced combustor system level modeling and they can interact with more system and component simulation tools. This is on top of the already considerable capabilities found in the  tool

Gas Turbine Combustor Heat Transfer Library

During the Preliminary design phase or when considering modifications to existing combustor designs it’s essential to make realistic predictions of  mass flow splits through the  various air admission holes, total pressure losses liner temperatures along the length of the combustor etc.

FLOWNEX-2015-combustor-simulationAlthough very powerful, 3D CFD solutions of combustors are specialized, time consuming processes and therefore are seldom exclusively used during initial sizing of a combustor.

It has been demonstrated that 1D/2D network tools, like Flownex, are capable of predicting with reasonable accuracy the same trends as more detailed numerical models.

The advantage, however, is Flownex’s rapid execution, which allows design modifications and parametric studies to be conducted more simply than ever before. The ease of use and incredible speed of Flownex allows 1000s of preliminary designs to be evaluated under all modes of operation for steady state and dynamic cases. Furthermore, the data obtained from the one-dimensional analysis can be used as boundary conditions for a more detailed three-dimensional model, ultimately supplementing a typical combustor design work flow.

While the simulation of combustor systems was previously possible in the Flownex environment, much of the work of implementing industry standard heat transfer correlations was left to the user through scripting .Now in Flownex SE 2015 it’s all been built in to the tool, while maintaining the flexibility required to model any combustor configuration.

New components include

  • Film convection component
  • Fluid radiation component
  • Jet impingement heat transfer component

To sum up Flownex allows more accurate initial designs, less time is spent on advanced 3D combustor simulations and rig tests, thus reducing development time and cost.

Here is a Video that shows off these features:

Added importers and integration features

AFT Fathom/Impulse/Arrow importer

An importer was added to import the file formats of AFT products. The importer imports all the diameters, loss factors heights, etc. so 90% of the effort is done, and in some cases the networks solve without any modifications.

ROHR2 Integration (pipe stress analysis software)

Flownex has the ability to calculate forces during dynamic simulations. This is very useful in pipe stress analysis for surge or water hammer cases. The ability to import complete geometries from ROHR2 and export results in the format that ROHR2 expects natively has been added. This means a user can perform these combined analysis now with ROHR2 with the minimum of effort.

Fluid Importers

An Importer was added to import liquid and gas properties from CoolProp an open source fluid property library. The existing Aspen/Hysys fluid importer was changed to be a generic Cape-Open compliant importer. This means that fluid properties can now be imported from any Cape-Open compliant server software.

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Tech Tips and Videos for Electromechanical Simulation with ANSYS Products

ansys_free_techtipsWe just recieved a new tech tip bundle from ANSYS, Inc on Electromechanical Simulation.  You may remember when we published the Mechanical and Fluids ANSYS tech tips a few weeks ago.  This latest kit continues with information for people making devices and systems that have mechanical and electrical systems.  The focus of the kit is the application of ANSYS Maxwell and Simplorer – Maxwell to model low frequency electromagnetics and Simplorer to model systems.

Here is a link to “The Electromechanical Simulation Productivity Kit ” here. The kit includes:

  • ANSYS Maxwell Automation and Customization Application Brief
  • ANSYS Maxwell Magnetic Field Formulation Application Brief
  • Electric Machine Design Methodology Whitepaper
  • Electromagnetics And Thermal Multiphysics Analysis Webinar
  • Rechargeable Lithium Ion Battery Whitepaper
  • Robust Electric Machine Design – ANSYS Advantage Article

We also have a collection of videos that are a great introduction to the tool set and how to use it. Check out the overview and the video on the washing machine at a minimum.  Even if you have a simple EMAG or do hand calcs, you need to look at Maxwell and Simplorer.

Vibro-Acoustics Analysis in ANSYS Mechanical as Told by a Structures Guy

Vibro-Acoustics-ANSYS-iconWith the introduction of ACT, the ANSYS Workbench editors have gained capabilities and shortcuts at much faster rate than what can be introduced in a development cycle. One of first and most far-reaching extensions is the acoustics. Inevitably I was called on by one of our customers to show them how to do a vibro-acoustics analysis (harmonic with acoustic excitation), which I did. Since the need for this type of analysis is quite broad, I’ll share it here too.

There was an extra level of excitement with this, in that I’m a structures specialist with no prior acoustics experience. So, I did my own self-training on this topic. I have to give tons of credit to Sheldon Imaoka of ANSYS Inc., who took the time to thoroughly answer the questions I had. That being said, this article will be from the standpoint of a structures engineer who’s just recently learned acoustics.

The first thing you’ll need to do is download the Acoustics extension from the Downloads section at the ANSYS Customer Portal and install it in Workbench.

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It’s at the very top, under ‘A’ for “Acoustics”

One thing you’ll notice when you unzip the Acoustics Extension package is that it contains and entire Acoustics training course. Take advantage of this freebie when learning acoustics analysis. I’ll note that, most of the process outlined in this article comes from the Submarine workshop in the acoustics training course.

Once you’ve installed and turned on the Acoustics extension, insert a Harmonic Analysis system into the project schematic, link to the solid geometry file, and specify the material properties for the solid. You’ll specify the properties for the acoustic region in Mechanical under the appropriate Acoustics extension objects.

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Rename as you see fit

Assuming you just have the geometry for the solid and not the acoustics domain, create two acoustics regions around the solid. The first region, surrounding the solid, will function as the fluid region itself, through which the acoustic waves travel and interact with the structure. The second region, surrounding the first acoustics region, will function as the Perfectly Matched Layer (PML). The PML essentially acts as the infinite boundary of the system. (If you’re an electromagnetics expert, you already know this and I’m boring you.) You can easily create these domains using the enclosure tool in DesignModeler.

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Acoustics Regions

Now we’re ready for the analysis. Open up Mechanical. Look at all those buttons on the Acoustics toolbar! Yikes! Fortunately we just need a few of them.

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Here they are

Insert an Acoustic Body and scope it to the acoustic region surrounding the structural solid. In the Details, enter the density and speed of sound for the fluid. Also set the Acoustic-Structural Coupled Body Options to Coupled With Symmetric Algorithm.

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Pay attention to the menu picks, Details, and geometry scoping here and in the rest of the image captures

“Coupled” refers to coupled-field behavior, i.e. the mutual interaction between the structure and the fluid. You’re probably familiar with this. You need that, otherwise the acoustic waves are just bouncing off the structure and the structure isn’t doing anything. Regarding the Symmetric Algorithm: The degrees of freedom for the acoustic system consists of both structural displacements and fluid pressures, giving you an asymmetric stiffness matrix. However, ANSYS has incorporated a symmetrization algorithm to convert the asymmetric stiffness matrix to a symmetric matrix, resulting in half as many equations that need to be solved and thus a faster solution time yadda yadda yadda, so go with that.

Now insert another Acoustic Body, this time scoped to the outer acoustic region (body). This is your Perfectly Matched Layer. Specify fluid density and speed of sound as before. This time, leave the Coupled Body Option as Uncoupled. But, set Perfectly Matched Layers to On.

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Apply an Acoustic Pressure of zero to the outer faces of the PML body (Boundary Conditions > Acoustic Pressure). As you may have guessed from the menu pick, this is your acoustics boundary condition.

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Now we’ll apply some acoustic wave excitation to this thing. From the Excitation menu, select Wave Sources (Harmonic). In the Details, set the Excitation Type to either Pressure or Velocity, set the Source Location and specify the excitation pressure or velocity value. In this example, I went with Pressure since that’s what MIL-STD-810 specifies, but this option will be based on your customer requirements. I also assumed an external acoustic source (hence, Outside the Model), but again, that will be based on your particular project. You also need to specify the vector of the wave source, via rotations about the Z and Y axes (f and q). In this case I chose 30 and 60 degrees, respectfully, to make it interesting. Once again, enter the density and speed of sound for the fluid.

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Insert Scattering Controls under the Analysis Settings menu and specify whether the Field Output should be Total or Scattered. Total gives you constant pressure waves that interact with the solid but not each other. Scattered gives you wave that interact and interfere with each other as well as the solid.

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Set up the Fluid-Structural Interaction boundary condition where the structural faces are “wetted” by the acoustic domain. The FSI Interface is found under the Boundary Conditions menu.

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Apply structural constraints and specify harmonic analysis settings just like you would with a standard harmonic analysis. Make sure you request Stresses under the Output Controls. Solve the model.

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Plot your structural results as you would for a typical harmonic analysis. Acoustic Pressure wave results may be found under the Results menu in the Acoustics toolbar. If you used Total field output for the scattering option, you can verify your wave source direction by looking at the Acoustic Pressure Contours. Keep in mind that the contours will be orthogonal to the axis of the sine wave; you may need to put some extra spatial thought into it to fully understand what’s going on.

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Acoustic Pressures: Field Output = Total

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Acoustic Pressures: Field Output = Scattered

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Von-Mises Stresses, Max Over Phase: Field Output = Scattered

As you’ll note in the training course, there are a number of design questions that can be answered with acoustics analysis. In this article, I’ve addressed what I thought would be one of the more popular applications of acoustics simulation. If the demand is there, I’ll research and compose more articles on various acoustics applications in the future. For instance, another area I’ve examined is natural frequencies of a structure that’s submerged in a fluid. If there’s another acoustics topic you’d like us to write about, please let us know in the comments.

Seminar Info: Designing and Simulating Products for 3D Printing

Note: We have scheduled an encore Lunch & Learn and companion Webinar for March 23, 2015.  Please register here to attend in person at CEI in Phoenix or here to attend via the web.

ds43dp-1People are interested in how to better do design and simulation for products they manufacture using 3D Printing.  When the AZ Tech council let us know they had a cancelation for their monthly manufacturing Lunch and Learn, we figured why not do something on this topic, a few people might show up. We had over 105 people register, so we had to close registration. In the end around 95 total people made it to the seminar, which is more than expected so we had to add chairs. Who would have thought that many people would come for such a nerdy topic?.

For an hour and fifteen minutes they sat and listned to us talk about the ins and outs of using this growing technology to make end use parts.  Here is a copy of the PowerPoint as a PDF.

We did add one bullet item in the design suggestions area based on a question. Someone pointed out that the machine instructions, what the AM machine uses to make the parts, should be a controlled document. They are exactly right and that is a very important process that needs to be put in place to get traceability and repeatability.  

Here are some useful links:

As always, do not hesitate to contact us for more information or with any questions.

If you missed this presentation, don't worry, we are looking to schedule a live/web version of this talk with some enhancements sometime in March.  Watch the usual channels for time, place, and registration information. We will also be publishing detailed blog posts on many of the topics covered today, diving deeper into areas of interest.

Thank you to the AZ Tech Council, ASU SkySong, and everyone that attended for making this our best attended non-web seminar ever.

Design and Simulation for 3D Printing Full House

Deflategate Update: ANSYS Simulation Shows it Really Does not Make a Difference.

There is still more debate going on about the deflated footballs that the New England Patriots used in their playoff game. "Who Deflated Them? When? Were they acting on orders?"  But no one is asking if it makes a real difference.

Enter ANSYS simulation software. Using the newest ANSYS product, ANSYS AIM, the engineers at ANSYS, Inc. were able to simulate the effect of lower pressure on grip. It turns out that the the difference in pressure only made a 5mm difference in grip. No big deal.  

Being a Multiphysics tool they were able to quickly also run a flow analysis and see what impact drag from "wobble" had on a pass.  A 10% off axis wobble resulted in 20% more drag, that is a few yards on a long pass.  Their conclusion, throwing a tight spiral is more important than the pressure of the ball.

Check out the full article on the ANSYS blog: 

http://www.ansys-blog.com/superbowl-deflategate-scandal-debunked-using-engineering-simulation/#more-11576

Here is the video as well:

FDA Opening to Simulation Supported Verification and Validation for Medical Devices

FDA-CDRH-Medical-Devices-SimulationBringing new medical device products to market requires verification and validation (V&V) of the product’s safety and efficacy. V&V is required by the FDA as part of their submission/approval process. The overall product development process is illustrated in the chart below and phases 4 and 5 show where verification is used to prove the device meets the design inputs (requirements) and where validation is used to prove the device’s efficacy. Historically, the V&V processes have required extensive and expensive testing. However, recently, the FDA’s Center for Devices and Radiological Health (CDRH) has issued a guidance document that helps companies uses computational modeling (e.g FEA and CFD) to support the medical device submission/approval process.

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Phases and Controls of Medical Device Development Process, Including Verification and Validation
 The document called, “Reporting of Computational Modeling Studies in Medical Device Submissions”, is a draft guidance document that was issued on January 17th, 2014. The guidance document specifically addresses the use of computation in the following areas for verification and/or validation:

  1. Computational Fluid Dynamics and Mass Transport
  2. Computation Solid Mechanics
  3. Computational Electromagnetics and Optics
  4. Computational Ultrasound
  5. Computational Heat Transfer

The guidance specifically outlines what form reports need to take if a device developer is going to use simulation for V&V.  By following the guidance, a device sponsor can be assured that all the information required by the FDA is included. The FDA can also work with a consistent set of input from various applicants. 

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CFD Simulation of a Drug Delivery System. Used to Verify Uniform Distribution of Drug

Computational Modeling & Simulation, or what we usually call simulation, has always been an ideal tool for reducing the cost of V&V by allowing virtual testing on the computer before physical testing. This reduces the number of iterations on physical testing and avoids the discovery of design problems during testing, which is usually late in the development process and when making changes is the most expensive. But in the past, you had to still conduct the physical testing. With these new guidelines, you may now be able to submit simulation results to reduce the amount of required testing.
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Simulation to Identify Stresses and Loads on Critical Components While Manipulating a Surgical Device

Validation and verification using simulation has been part of the product development process in the aerospace industry for decades and has been very successful in increasing product performance and safety while reducing development costs.  It has proven to be a very effective tool, when applied properly.  Just as with physical testing, it is important that the virtual test be designed to verify and validate specific items in the design, and that the simulation makes the right assumptions and that the results are meaningful and accurate.

PADT is somewhat unique because we have broad experience with product development, various types of computational modeling and simulation, and the process of submission/approval with the FDA. In addition, we are ISO 13485 certified. We can provide the testing that is needed for the V&V process and employ simulation to accelerate and support that testing to help our medical device customers get their products to market faster and with less testing cost.  We can also work with customers to help them understand the proper application of simulation in their product development process while operating within their quality system.