When you talk about additive manufacturing in the aerospace industry, it is impossible not to discuss design. Design is one of – if not  – the most important driving factors behind AM’s benefits in the development of aerospace parts. Design is what enables innovation in lightweighting and gains in performance efficiency. In a word, design is critical.

Considering this, we felt it important to not only consider AM in aerospace from the hardware and aerospace sides, but also from the perspective of engineering design software – we should note here that here our definition of design also encompasses simulation and manufacturing analysis. To shed some light onto the power of engineering design for aerospace applications, we spoke to Ryan O’Hara, the Technical Director of Aerospace and Defense at nTopology Inc.

A bit of background

nTopology will be a familiar name to many in the industry, as it is one of the leading engineering software companies specializing in design for additive manufacturing (DfAM). In 2019, the New York-based company launched nTop Platform, a complete engineering workflow that is offered through an annual subscription mode.

“Modern design engineering ecosystems are continually trying to pull more information forward in the process in an effort to enable engineers to make use of downstream knowledge early in the design process,” O’Hara explained. “This is especially important in advanced manufacturing applications, where the downstream manufacturing process can have a significant impact on design decisions from the onset of the design process.

“nTop Platform provides a common foundation so that engineers across a number of disciplines including design, simulation and manufacturing can capture their own piece of the process, send it upstream (or downstream) and leverage that of others at any point. Additionally, various pieces of workflow knowledge can be configured into a larger process or application on top of the platform, providing a top-level design engineering environment that captures the work, skill and engineering know-how of each design team member.”

Close-up of the fuel-cooled oil cooler design

From a design perspective, nTop Platform enables users to generate AM-optimized geometries through its AM Toolkit, which combines topology optimization algorithms and field-driven design technology. In practice, this means that parts can be designed to only have material where it is needed, while still meeting performance specifications and manufacturing limitations (i.e. overhang angles, wall thicknesses, etc).

O’Hara states: “The three key drivers that set nTopology apart from other software vendors are: unbreakable modeling technology that allows for lightning-fast iterations and unlimited geometric complexity; field driven design that uses geometry, simulation and manufacturing fields to drive geometric design to optimize the part; and the ability to create workflows that can be reused, shared, remixed and automated.

“nTop Platform has provided a combination of workflows that directly facilitate DfAM process steps. These include workflows for lightweighting, architected materials and direct export of slice data to certain build processes. nTop Platform also allows users to deploy their own workflows within a company. In one instance, an experienced AM manufacturing engineer was able to leverage nTop Platform to configure a workflow that could be used as a time and cost estimator and shared with a team of design engineers. As such, the design engineers could see in near real-time the effects of their design decisions on the downstream AM processes.”

nTop Platform is easily integrated with existing CAD, CAE and CAM platforms, to facilitate seamless workflows for its clients. “nTop Platform embraces the most useful aspects of CAD, CAE, CAM and topology optimization, and it integrates with all modern engineering systems,” O’Hara says. “It also adds a new layer of control and governance for reliable, consistent and validated results without the need for human involvement at every step.”

Rising to the nTop of aerospace

Today, more than 30% of nTopology’s clients are from the aerospace industry, and the company’s nTop Platform is in use at some of the world’s largest aerospace firms to assist in the development of new and innovative parts. The platform’s appeal comes in large part from its design capabilities, as well as its efficient workflow.

Close-up of the fuel-cooled oil cooler design

“In today’s design environment, engineers are tasked with having to produce higher performing parts with a given design volume,” O’Hara explains. “They are asked to do this on shorter and shorter design cycles, all while making their components lighter.”

Looking specifically at the benefits of nTop Platform and additive manufacturing in aerospace, O’Hara identifies three key areas: the maximization of part performance, the consolidation of design and the production of lighter parts.

“nTop Platform and AM fundamentally enable three specific areas for the aerospace industry,” he elaborates. “First, the ability to maximize part performance in a way that was not previously possible with traditional design and manufacturing methods by allowing for the generation and fabrication of complex shapes that have direct effects on the fundamental function of the component. Second, consolidation of design: by decreasing the number of sub-components and making the parts multi-functional it allows for fewer components, reduced assembly time and more reliable systems. Third, aerospace components can be improved by using geometry that uses material more efficiently through optimization algorithms, periodic structures and field-driven design methods to produce lighter parts.”

Compared to other engineering software solutions, nTop Platform stands out in a critical way. That is, while most modeling environments are built to document an engineering solution, nTop Platform actually creates one. “nTopology integrates mathematics and simulation to create a single environment without geometry bottlenecks,” O’Hara says. “nTop Platform allows engineers to fully utilize their computers to understand and solve hard problems.

“Anytime the barriers to design and subsequent manufacturing can be removed, there will always be a benefit to the designer, manufacturer and, ultimately, the end-user. nTopology’s fundamental goal is to allow engineers to be able to generate geometry without limitations. When these parts can be quickly and easily realized in the physical space, huge opportunities become available for all those individuals involved in the design process.”

Where additive and DfAM make the biggest impact

In the aerospace sector, there are a vast number of parts that can be designed, redesigned and optimized using AM, from engine components to interior cabin structures. According to O’Hara, however, one of the part groups that will benefit the most from additive manufacturing is heat exchangers.

“Far and away the biggest limitation to air and space components is the mitigation and handling of heat,” he explains. “Heat from a turbine engine, electronic device or working fluid often needs to be transported in a way that ensures the critical engineering process that the heat comes from can be maintained. Heat exchangers are fundamental to these processes and require complex internal geometries to be effective. nTopology and AM are able to deliver huge gains in performance by increasing surface and decreasing wall thickness to enable the exchange of heat in ways that are simply not possible with traditional design and manufacturing processes.”

In one example, nTopology’s software was used in combination with ANSYS CFX to redesign a Fuel Cooled Oil Cooler (FCOC). The report, which can be read in full here, details the process from initial redesign in CAD, to process steps in nTop Platform and to final Computational Fluid Dynamics (CFD) and analysis steps in ANSYS CFX.

300% increase in heat transfer

The part in question is a high-performance heat exchanger (HEX) used in the aerospace industry, which exchanges heat between the engine oil and the fuel of an aircraft. The design was inspired by a project led by America Makes aimed at leveraging AM to redesign a legacy shell and tube HEX to determine whether advanced design and manufacturing could increase performance.

In this case, nTop Platform enabled engineers to define a volume for the part which could act as a basis for the modified FCOC design, maximizing surface area while minimizing mass in its interior walls. The surface area of the part was maximized using a Triply Periodic Minimal Surface (TPMS), also known as gyroid structure. By implementing this structure in the heat exchanger design, the team achieved a 146% increase in surface area compared to traditional tube and shell HEX of the same size. 

The fuel-cooled oil cooler design

“When coupled with advanced manufacturing methods, these TPMS structures enable parts with both high strength and heat dissipative requirements to be designed in a manner that was previously impossible to achieve,” says O’Hara.

The wall thickness of the component was minimized thanks in large part to the use of a nano-functionalized high-strength 7000 series aluminum alloy (7A77), which was developed specifically for AM. The superior strength of the metal enabled thinner interior walls in the part without sacrificing strength or performance. In fact, the gyroid structure has walls about half the thickness of those made from traditional casting-grade aluminum alloys for AM. Overall, the increased surface area and minimized wall thickness of the FCOC resulted in a 300% increase in heat transfer compared to the legacy component. 

All this was achieved using nTop Platform with the support of ANSYS CFX capabilities, which provided computational fluid dynamics simulation to evaluate the performance of the redesigned FCOC. The software company concludes: “nTop Platform allows the user to create complex geometries (TPMS structures, fluid volumes, smooth lattice-solid transitions), while maintaining complex control over the geometric model, and then easily allows the user to export the geometry outside of nTop Platform for validation and verification.”

The key is design

It is becoming increasingly apparent that additive manufacturing is unlocking new application opportunities in the aerospace industry, through the production of more efficient and often higher performing parts. As we’ve seen, additive manufacturing systems are not unlocking these capabilities on their own: sophisticated software programs such as nTop Platform are really at the core of these benefits and allow AM’s potential to be fully exploited.

nTopology is one of the companies pushing AM technologies and applications ahead from the software side, with an integrated platform that removes geometric barriers to advanced design and enables the maximization of part performance, the consolidation of design and the production of lighter parts.

For more insights into the intersecting Aerospace and AM industries, read our full Aerospace AM Focus 2020 eBook.

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