Houdini Puts Navistar International on the Road with Eight-Node "Brick" Finite Element Model Generation

Engineers at Navistar, a leading manufacturer of medium and heavy trucks, school bus chassis and diesel engines in North America and abroad, use Houdini for CAD to "brick" finite element generation.

Superior engineering has made Navistar International a trusted name in the trucking industry. With Algor's Houdini, Navistar engineers are taking advantage of the best that engineering software has to offer.

Navistar engineers recently spoke with us about designing a part for the crankshaft of an engine. The crankshaft is the heart of the engine and its structural soundness is vital.

While working on this crankshaft design, Houdini enabled Navistar engineers to use the CAD and analysis software packages of their choice while taking advantage of Algor's unique mesh generation and enhancement capabilities.

What Houdini Does

Houdini takes a CAD solid model from virtually any source, automatically optimizes the surface mesh, then fills the volume with eight-node "brick" finite elements. The resulting high-accuracy eight-node "brick" solid model is ready for analysis by Algor or any other popular FEA program, including Ansys, Abaqus, Cosmos, SDRC, Nastran, Patran, NISA and Procast.

The engineers we interviewed at Navistar design their models in Master Series 2.1, and conduct their analyses with a popular FEA package. Houdini bridges these two software packages with unique mesh generation and enhancement capabilities.

At the Heart of the Engine

The crankshaft is the heart of an engine. Its structural soundness is critical because it is subjected to intense forces including firing pressure and torsional loading.

Navistar engineers use finite element analysis in conjunction with prototype testing to establish a factor of safety for all parts. The crankshaft in this example was subjected to those tests.

From CAD Solid Model to eight-node "Brick" Model

The component of the crankshaft shown below was designed in Master Series by Dr. Xinmin Xu, a Development Engineer at Navistar. Dr. Xu exported the model as an IGES trimmed surface file into Houdini. After using Houdini's mesh generation and enhancement capabilities, the resulting eight-node, "brick" finite element model was ready for analysis.

Dr. Xu at Navistar used Houdini to mesh a Master Series CAD solid model. The actual part can be seen to the left of the computer.

Refining the Surface Mesh

Dr. Xu wanted a very refined, high-accuracy mesh around the key features of the crankshaft component. However, if the mesh was very fine throughout the model, the analysis would take a large amount of time and computing resources.

Dr. Xu used a two-step technique in Houdini which allowed him to keep the fine mesh around key features and create a coarser mesh elsewhere. The result was a high accuracy mesh in the critical areas of the part while keeping the model to a manageable size.

With Houdini's unique surface mesh generation capability, Dr. Xu first created a very fine, global mesh. After checking the mesh and making adjustments by hand, he selected all the mesh in the most critical areas of the crankshaft component.

The selected mesh was specified in a different color. The model was then reprocessed with Merlin mesh enhancement technology, an important Houdini tool. Merlin created a coarser mesh throughout the rest of the model.

Dr. Xu used Houdini to create this eight-node "brick" finite element model of a crankshaft.

Creating the Solid Mesh

After a quick check of the surface mesh, Dr. Xu used Houdini's Hexagen solid mesh generator to create the 3-D "brick" mesh from the surface mesh.

"Houdini's eight-node 'brick' generation capabilities gave me an opportunity to create a crankshaft model with a high degree of accuracy not possible before," said Dr. Xu.

"For example," Dr. Xu continued, "oil drillings inside the crankshaft were modeled with a high mesh density, yet the size of the model was still within the running capacity of our HP735 workstation."

The Analysis

Static, linear stress analysis was performed on the crankshaft to test the effect of firing pressure and torque. Finite element analysis results and prototype testing results correlated closely thanks to Houdini's meshing capabilities.

About Algor

"The capability of Algor to interact with a variety of packages gives me the flexibility to choose software based on my preferences," said Dr. Xu. "For this example, I used Master Series for building solid models and Algor for meshing.

"The automatic mesh generator (Hexagen) is superior. It gives me quick surface meshing, the ability to modify surface mesh density, easy element adjustment, and a check to assure that the model is watertight.

"The ability to control the mesh density only in the areas of interest is essential," said Dr. Xu. "It means that I can have the accuracy of fine mesh around key features while keeping the model to a reasonable size."

Navistar plans to use Houdini as an important part of their design and analysis process for all cast and forged engine components.

Keep On Trucking

The crankshaft is just one example of the work that Navistar engineers are doing with Houdini. The front cover, cylinder head, exhaust manifold, oil cooler header, alternator bracket, cylinder block and fuel injector were also meshed using Houdini. Dr. Xu plans to use Houdini on all forged and cast engine components he designs in the future.

Houdini offers superior meshing capabilities and the option of taking advantage of a wide range of engineering software. These engineering advantages will help keep Navistar the world-wide leader in diesel technology.