Using NX allows design and analysis to work together more efficiently and productively

Product: NX CAD, Simcenter 3D
Industry: Aeroespacial y Defensa

For more than 30 years, ENGINEERS at ATA Engineering, Inc., (ATA), have provided analysis and test-driven design solutions for structural, mechanical, electromechanical, and aerospace products. The company has worked on a wide variety of projects, including amusement parks, biomedical devices and electronic components.

Most of ATA Engineering’s work is done in the aerospace industry, for clients such as Orbital Sciences, Lockheed Martin Space Systems, Pratt & Whitney, NASA, Jet Propulsion Laboratory, Air Force Research Laboratory and General Atomics. There is no room for errors in this job: it is critical to meet specifications accurately, while facing strict deadlines. ATA engineers often face short production runs, sometimes even for a single unit, as a satellite component. It’s forced that they do well the first time.

ATA staff have used SOFTWARE NX™ for many years. However, they recently applied the mostrecent version of computer-aided design (CAD) and computer-aided engineering (CAE) NX software to complex real-world structures using three representative cases and found significant improvements in time and effort savings during design, analysis, and upgrade cycles.

ATA engineer Allison Hutchings defines it this way: “Real-world structures have complex design definitions and challenging analysis requirements, and both are constantly changing. NX enables you to cope with changes efficiently and productively.”

Changing model parameters without recreating geometry

The first use case involved meshing an isometric grid reflector model, such as those designed for assembly on a spacecraft. Isometric geometry provides advantages for spatial structures that must be rigid, lightweight, and durable, but the large number of surfaces implies that the definition of the initial geometry of the CAD model and the CAE model can be tedious. When the design needs to be updated, such as altering the diameter, focal length, and measurement of cells in this case, “these changes can cause severe headaches,” Hutchings says. In many cases, you may need to completely recreate the geometry instead of simply updating it to incorporate the new dimensions.

Leveraging Synchronous Technology provided by NX along with an intelligent approach to the original design definition, however, these issues are avoided. Several techniques, such as patterns and expressions, facilitated the direct parameterization of key geometry definitions in NX CAD and this capability was leveraged directly for meshing and analysis. As a result, 100 percent of the geometry was automatically updated and 96 percent of the riveting was performed automatically when the associated finite feature model (FEM) was upgraded to the new geometry. Cleaning the remaining 4 percent was relatively quick and easy, particularly compared to the need to recreate FEM altogether.

The second use case was a lightweight support model. Because weight is a pressing factor in aerospace designs, the engineer must struggle with competitive goals to maintain the lightest possible support while meeting stiffness requirements while maintaining the ability to handle the necessary loads. The process often results in supports with complex geometry.

In Finite Element Analysis (FEA), the standard practice is to “idealize” geometry, eliminating details and features that do not affect analysis. It is done to save calculation time, but it is often necessary to repeat the idealization process each time the part is updated.

With NX, this additional step can be avoided. For this task, after the part dimensions were changed, 93 percent was automatically idealized and updated. Although the changes that were made to the support were relatively simple, the time and effort savings were remarkable: the automated idealization of the upgrade was more than 100 times faster than the manual process and meshing of the updated model was at least 3 times faster.

Updating geometry in minutes

The third use case focused on the model of an existing air brake: a assembly that allows an aircraft to slow down to land by generating a turbulent output flow from a fan bypass nozzle and also makes it easier to landing the aircraft slower, from a steeper angle, reducing overall noise.

The blade angles inside the air brake can have a drastic effect on the performance of the air brake under different conditions. By altering these angles in the model, the analyst can evaluate those effects. In this case, the prismatic blades were rotated to analyze configurations between 0 and 25 degrees. With NX, instead of performing a tedious manual process of reshaping the entire system, Hutchings simply changed the aspa angle parameter and was able to update the geometry in minutes, as the idealized part automatically adjusted to the new angle. Hutchings comments, “Map meshing is preserved, creating an identical mesh on the blade surfaces between all angles, then the CAD model propagates to the FEM and the mesh is updated in minutes.

In all three cases, new NX features made it possible to perform geometry updates quickly, Hutchings says. “We were able to parameterize the design definition, create a structural analysis model by leveraging the design for specific analysis requirements, updating design parameters, and propagating changes to analysis modeling much faster than would have been remodeled.”

More efficient engineering with integrated design and analysis

“These are all problems that we thought were difficult to solve before,” Hutchings says. In the past, updating the finite element model due to geometry changes would involve reshaping changes in CAD, resealing the model, and riveting to create FEM, or some very complex manual changes in meshing. Both options took quite a while. “Recent additions to NX have made these efforts much easier. The degree of connection NX makes possible between design and analysis more efficiently supports engineering compared to the use of non-integrated finite element processes,” he says.

The problems Hutchings examined illustrate the advantages of working with the integrated NX range. This is not only an improvement in the refresh rate, but also the possibility of failure between the CAD model and the finite element model is also less due to the way they are linked. “If you work with constantly changing design specifications, it’s very fast and easy to modify dimensions and change parameters with NX, without having to recreate finite element models,” he says. “This saves a lot of time and effort on tedious tasks, as well as providing confidence that the model will be updated to the correct design definition.”