# Thin Walled Cross Section Analysis for Crash Using the Macro Element Method

Why is cross sectional analysis useful?

Constantly growing safety requirements, search for improved material use, re-design of a structure to fulfill the needs of electromobility, creation of an innovative new vehicle design. All of those crash design challenges can be addressed through the usage of simplified cross sectional analysis performed in accordance with the Macro Element Method (MEM).

In the process of creating an optimal crashworthy structure, the mechanical response of thin walled beams plays a crucial role. The sooner the engineer gains the knowledge about required basic geometrical parameters of specific beams, their thicknesses and performance related to material properties, the better.

MEM provides the possibility to test various materials and geometrical concepts of your design. It’s a fast and effortless way to receive a variety of results and data on a beam’s mechanical properties which will substantially speed up the overall design process.

What are the benefits of simplification?

Simplified cross sectional models are perfect for early stages of the design process.

On this phase of conceptual work, only basic dimensions of a section need to be taken under consideration. The Macro Element Method enables engineers to work on a cross sectional model neglecting all minor dents and details. Thanks to the concept of a Super Folding Element, each corner of a column can be modeled by two connected plates, without needing to determine the radius.

Figure 2- example of a thin walled cross section created in accordance to the MEM (in CCC software)

In software based on such methodology, model creation is simple and quick.

Moreover, any modification of the original design in search for the optimal solution is as easy as possible. This simplified modeling approach is perfect for semi- and fully automatic optimization purposes.

Which cross-sectional parameters can be analyzed; what results are received?

A simplified model of a cross section is created from plates based on points located in a 2-dimensional space. Each plate represents one side-face of a beam. A collection of connected plates builds a segment. In consequence, analysis of numerous geometrical variants is not a challenge – thanks to the simplified model, coordinates of points can be changed manually or automatically in the optimization process. Additionally, each cross sectional plate is defined by several parameters, such as thickness or assigned material, which can also be easily toggled. From the calculation process, the engineer receives seven blocks of detailed results accurately characterizing the beam’s mechanical response.

Figure 3 – cross section calculations – available results

The engineer is granted a comprehensive package of data considering the beam’s crash performance on a very early stage of structure creation. Selection of an optimal design variant is possible within the pre-design stage.

How much time it takes to analyze a cross section?

One of the greatest advantages of working with a simplified cross sectional model is that the calculation time does not exceed several seconds! The engineer has the possibility to test hundreds of design concepts in minutes!

Figure 4- calculation time – single cross section

What makes the method even more attractive are the minimal hardware requirements. MEM software can be used on a standard PC machine or laptop.

Are the analysis results reliable?

Yes, calculations of a simplified cross sectional MEM model are not only fast but also accurate. The very methodology itself is routed in experiment and has been developed based on numerous lab data. Thirty years of close cooperation with automotive industry and various R&D offices grants the confidence of results accuracy.

Figure 5- CCC- Experimental Verification

S frames – Quasi Static Response (JSAE Experiments)

In summary: What are the benefits of simplified cross sectional modeling?

• Perfect for early stages of design process
• Easy and fast modeling
• Easy and fast design modifications
• Perfect for optimization purposes
• Short calculation time (up to few seconds)!!!
• Detailed results for various design concepts available in minutes
• Tested in practice by demanding customers

This guest post on Innovation Intelligence is written by Agata Abramowicz Sokoll, CEO of Impact Design Europe, developer of Crash Cad Calculate and Cross Section Creator. CCC and CSC are available through the Altair Partner Alliance.

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