Abstract

One of the many critical analysis tasks in aircraft design is the evaluation of structural stability, and since the invention of finite element analysis (FEA), engineers around the world have been attempting to perform analysis with as few elements (and thus the lowest amount of computational cost) as possible. One of those “sweet spots” between mathematically accurate results and lowest number of elements is the 20-node Hexahedral element (also known as Hex mesh). Unfortunately, from a historical perspective, the process required to develop geometry suitable for a hexahedral mesh has been complicated and time-intensive – almost to the point of negating the time saved by faster solutions due to the hexahedral mesh. With the availability of MSC Apex’s hex meshing toolsets, engineers now have a quick and innovative solution to the creation of high-quality mesh for structural analysis. Ever since hex meshing was invented, comparisons have been made in many industries as to the accuracy of results between hexahedral elements and tetrahedral elements [1][2][3]. Most analysts prefer hex elements because the results are generally more accurate, but sometimes avoid using them because of the extra cost (measured in hours of engineering work) needed to create them. Therefore, engineers would like to use tetrahedral mesh for analysis due to project schedule. In certain circumstances, though, a high-quality hexahedral mesh is necessary and extra time must be taken to develop this type of mesh in favor of result accuracy. Users from Northrop Grumman Mission Systems evaluated MSC Apex’s hex meshing functionality by conducting a benchmark workflow to compare time spent in using Patran and MSC Apex, finding approximate 9 hours productivity gains with the new workflow. In this white paper, the details of the benchmark workflow, MSC Apex’s hex mesh toolset, and time saving of each step are introduced. Prior to MSC Apex’s advancements in the hex meshing workflow, users used Patran as a pre-processor and MSC Nastran as a finite element solver in order to create the hexahedral mesh for a variety of its electronics products. This legacy workflow, measured on an evaluation-worthy geometry part, previously took 16 hours to complete the pre-processing in Patran and solve using MSC Nastran. Using MSC Apex on this same geometry file, this workflow was reduced to 7 hours (55% time saved), yielded more uniform results, and allowed the engineer additional time spent on inspecting and refining the mesh quality, which was not a luxury allowed using the traditional workflow with Patran. Additionally, the Nastran BDF file size was smaller f om MSC Apex, due to the advancements in hex meshing, allowing for fewer elements to achieve the desired results. MSC Apex’s advancements in hexahedral mesh creation & validation were applied during this workflow evaluation, including Geometry Cleanup, Solid Split, Hex Mesh Creation, Generative Meshing Updates, and Hex Mesh Diagnostics Tool. Included below is a detailed description of this geometry file and workflow evaluation, including a description of how these time savings were achieved.