MSC Software "Model of the Month" Part 1: HyperSonic X-43 Type Vehicle

This article was featured by MSC/NASTRAN on their home page as "Model of the Month" from August 1998 to January 1999

HyperSizer® - Designs on the Fly!

What is HyperSizer?

HyperSizer is software that performs automated structural analysis and sizing optimization based on aerospace methods for strength, stability, and stiffness.

Analysis methods range from closed form, traditional hand calculations repeated every day in industry to more advanced panel buckling algorithms. Margin-of-safety reporting for every potential failure provides the engineer with a powerful insight into the structural problem.

Optimization capabilities include finding minimum weight panel or beam concepts, material selections, cross sectional dimensions, thicknesses, and layups from a library of 40 different stiffened and sandwich designs and a database of composite, metallic, honeycomb, and foam materials. The engineer is able to provide 'real-world' expertise in the optimization process by interacting with the software.

Modern and innovative physics based solutions, coupled with MSC/NASTRAN finite element analysis, are provided for today's composite designs such as the Joint Strike Fighter and the Reusable Launch Vehicle. HyperSizer's unique methods are quick, accurate, and will analyze and optimize an entire aircraft.

About the Model

The model represents a NASA designed two-stage-to-orbit aerospace plane requiring accurate analysis capabilities to account for a complex thermo-mechanical environment. The integrated airframe/engine design contains a large volume of pressurized cryogenic fuel. Internal bulkheads serve as shape control members to maintain the vehicle's shape. The aeroshell is designed to be graphite/epoxy, hat-shaped stiffened panels.

Though HyperSizer can analyze and optimize FEMs as large as one million DOFs, the choice was made to build a relatively small model of approximately 30,000 degree of freedoms (DOF) for the aerospace vehicle. This allows us to take advantage of HyperSizer's unique panel and beam stiffness formulations that achieve accuracy with coarsely meshed MSC/NASTRAN FEMs. More about this later.

 How does HyperSizer Benefit the Aerospace Plane Design?

First, HyperSizer provides a complete and detailed analysis of the entire aircraft including concise margin-of-safety (MoS) summaries of all potential structural failure modes for all areas of the vehicle. This color contour plot shows critical MoS of the aero-shell panels for all analyses performed. For instance, if local buckling of the facesheet has a lower MoS than panel buckling, then for that surface area, the MoS for local buckling is shown. This plot quickly indicates areas which do not meet structural integrity requirements, or over-designed areas which can be made lighter.

This entire vehicle, containing 7 assemblies, 21 optimization groups, and 203 structural components, is analyzed on a Pentium Workstation in two minutes.

Second, HyperSizer optimizes all aspects of the aerospace plane structural design including: material selection (Gr/Ep vs. Al); panel and beam concepts (hat stiffened panel vs. honeycomb sandwich panel); and exact cross sectional dimensions (beam flange width of 1.24 vs. 1.39).

Third, HyperSizer produces accurate structural dry weight predictions as shown in the unit weight contour plot here. It is very important to quantify dry weight of competing concepts accurately early in the design process. Revolutionary designs such as the Joint Strike Fighter and Reusable Launch Vehicle typically do not have historical weights available.

Interaction between the engineer and the software is key to HyperSizer's design

process

Engineers learn within seconds the strengths and weaknesses of their structural designs from the software's interactive reporting of margins-of-safety. Interactive 3-D graphics provide visual inspection of the structural component layout, assemblies, and drawn to scale optimum panel and beam cross sections. These features are used on the aerospace plane to quickly interpret and understand design flaws. Critical design issues were identified and resolved early in the design process, allowing ample time to perform many design trade studies. This quick and highly interactive process makes the task of saving weight easy and fun.

To learn more about the benefits of HyperSizer for the aerospace plane, ccontinue reading at
MSC Model of the Month Part 2»