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Reduce weight and manufacturing costs through simulations

Optimization of a battery pack holder

In just four months, masters student Laura Hinsching immersed herself in FEM simulation during the Corona Online semester. So, with a lot of self-motivation, and in a short time, she was able to show a very impressive result in the further development of a mounting device for battery packs.​

Material and geometry variants

Together with mechanical engineering professor Dr.-Ing. Folker Flüggen and seminar leader Dipl.-Ing. (FH) Frank Einicke, Laura Hinsching, at Nordhausen University of Applied Sciences, developed an ambitious concept study. The aim of the study was a weight and cost-optimized further development of a mounting device for a battery pack. For this purpose, Laura Hinsching used the Ansys Workbench simulation software to achieve the desired optimization by calculating material and geometry variants.

The concept study was initiated by a medium-sized Thuringian company active in the development of lithium-ion batteries for the marine sector.

Propagation test for type approval

As a reference scenario, the desired operating condition was first evaluated. The so-called propagation test and the interaction of the lithium-ion cells with the cell holder were mapped as a thermal worst-case scenario with Ansys Workbench. For this purpose, a coupling of transient thermal and structural mechanical simulation was carried out. As a third calculation, a prestressed modal analysis and a dynamic structural-mechanical analysis were selected for the dynamic load case due to vibrations of the battery packs during operation on the high seas. The results were validated by measurements or, specifically, by comparison with already existing measurements on the real assembly.

The calculation was first carried out with the actual state of the cell holder and then with various alternative materials. After a suitable material could be selected according to the simulation results, the geometry was examined and optimized by varying the geometry parameters on the basis of the prescribed test scenarios.

Thermal runaway as a worst-case scenario

A critical requirement for marine battery systems is the thermal load capacity of the components. In the so-called propagation test, the worst case of an overcharge with subsequent thermal runaway of a cell in the system is tested. Normally, the probability of such an event is very low due to the built-in energy management software and the high level of security of the cells. Nevertheless, this scenario must be safeguarded as part of the approval procedure. "In this case, thermal load peaks of over 200°C can occur locally at the cell holders under consideration," reports Laura Hinsching. "Consequently, the choice of materials is limited. At the same time, it had to be ensured that the cell holder guarantees the radial and axial fixation of the cells during the entire overcharging process. This is the only way to prevent propagation and thus the spread of thermal runaway among the cells."

Based on the simulation results, a concept for the production of the components was worked out, which ensures realizable significant weight reductions with an optimal material utilization rate. A large part of the reduction in weight and costs can be attributed to the polymer material selected. This material was convincing due to its low material price as well as low production costs in component manufacture (injection moulding) and post-processing. At the same time, it was possible to ensure sufficient mechanical strength and thermal resistance for the application at hand.

> 40%
Cost reduction
by polymer material
> 60%
Weight reduction
with high strength

Finalize the product for series production

The medium-sized Thuringian company is extremely positive about the result of the concept study. "With the results of the studies, we were able to take a good and important step forward in the further development of our product," explained the head of battery development.

"The project was completed in less than four months thanks to the simulation and the dedicated efforts of those involved in the project. As a result, we can now commission the manufacture of a prototype in order to finalize the product for series production."

Training problem solvers for tomorrow is the goal of Nordhausen University of Applied Sciences. Even the Greek scholar Aristophanes said in 400 B.C. "To educate people is not to fill a vessel, but to kindle a fire". The fact that online teaching and application-oriented knowledge transfer can also succeed in releasing such driving forces makes those responsible at Nordhausen University of Applied Sciences very proud. They are also optimistic about the future of engineering education, because Laura Hinsching is now working successfully as a design engineer for her "client".

FEM simulation in teaching - successful even in the Corona age

For many years, the Ansys Workbench simulation platform has had a firm place in the training of future engineers at Nordhausen University of Applied Sciences. Within just four weeks, in April 2020, it became the first university in Thuringia to completely convert its curriculum to online teaching, including the FEM laboratory.

Since then, the students in FEM seminars have been using the possibilities of Ansys Student for working on seminar assignments. The online platform makes it possible to exchange ideas with lecturers and fellow students and to discuss and work on projects together. Starting with the basics of statics, the content of the training includes nonlinear structural mechanics, temperature fields, topology optimization, design exploration and fluid-structure interaction. Thanks to the possibilities of materials testing in the university's laboratory, material models for simulation can be derived and validated directly from real measured values. A university of short distances makes this possible. In addition, the integration of the new software generation Ansys Discovery is being planned in order to further expand the approach of simulation-driven product development (Simulation Driven Design) based on physical behavior. 

A large part of the students had never had any contact with the simulation tool until the time of the first "Corona Semester" in April 2020. And then learning FEM "from 0 to 100" in the home office makes the result of Laura Hinsching's final thesis, after just four months, all the more impressive. "What was able to be implemented here, also with a huge amount of self-motivation by masters student Laura Hinsching, is very impressive," emphasizes seminar leader Dipl.-Ing. (FH) Frank Einicke proudly.

Hochschule Nordhausen
Dipl.-Ing. (FH) Frank Einicke

Author: Gerhard Friederici (CADFEM GmbH)
Images: Hochschule Nordhausen

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