## 3 Mechanical Vibration Tests
### Comparision of Bolt, Vacuum, and Electromagnetic Fastening Methods  
To evaluate the potential of different mounting methods, it is necessary to compare their basic characteristics in terms of holding (clamping) force, speed of removal, weight, and cost. The result of comparing the holding forces is presented in Figure 13.  
Electric car batteries are typically installed in the floors of cars, with low heights ranging from 110 to 180 mm. Given their average density of 2.2 kg per liter, this results in a mass per 1 cm\({}^{2}\) of battery ranging from 0.024 to 0.039 kg. This information is crucial when considering the ability of different clamping systems, such as vacuum clamps and electromagnetic chucks, to transfer accelerations to the battery installation. For a vacuum clamp with a holding force of 7 N/cm\({}^{2}\), it can transfer accelerations ranging from 20 to 33 g per 1 cm\({}^{2}\) of holding area. In contrast, an electromagnetic chuck (for the catalogue value of holding force) can theoretically transfer accelerations in the range of 315 to 516 g (from 84 to 137 g for a thinner steel plate and 33N/cm\({}^{2}\) of holding force) per 1 cm\({}^{2}\) of holding area. The comparison of the weight of different fastening systems was realized by comparing the weight of 1 cm\({}^{2}\) of fastening surface because it is the main factor affecting the weight of a given holder and its fastening system. The average material density of an electromagnetic holder is about 3 times greater than that of a vacuum holder, and similarly the height is 3 to 3.5 times greater, resulting in  
Figure 13: Comparison of holding forces of vacuum, electromagnetic clamps, and bolts. about 10 more mass per 1 cm\({}^{2}\). That is why an average electromagnetic chuck mass per 1 cm\({}^{2}\) of holding area is equal to 0.055 kg/cm\({}^{2}\) and the mass of a vacuum clamp per 1 cm\({}^{2}\) of its surface area ranges from 0.005 to 0.008 kg for clamp heights of 20 to 30 mm. For the holding area of 60 \(\times\) 60 cm this results in a difference of between about 18 to 28 and almost 200 kg. A large mass of electromagnetic clamps requires very powerful electromagnetic vibration exciters or substantially limits the obtainable vibration accelerations or masses of the DUT. The comparison of the weight of different fastening systems is presented in Figure 14.  
Looking at the cost of different fastening techniques, it can be said that the cheapest solution are bolts. The price of one hundred of them is about EUR 20. The cost of a 60 \(\times\) 60 vacuum plate is about EUR 1100, and the cost of three electromagnetic chucks with dimension 20 \(\times\) 60 cm is about EUR 8500 with additional costs for control units for the electromagnets of around EUR 1000. A comparison of the disassembly (release) time makes the screws, unrivaled in other parameters, useless for the purpose of creating a system for rapid evacuation of the battery pack under test from the test stand. Pneumatic and electromagnetic mounts allow the DUT to be released from the head expander or the slide table in a matter of seconds, compared to over a dozen minutes for almost 70 bolts. The performances of the electromagnetic chucks and the vacuum clamping systems in the presence of vibrations can vary, and their suitability depends on the specific requirements of a given application. Due to their strong magnetic holding force, electromagnetic can better transfer vibrations from the base to the workpiece (in this case, the device under test). Vacuum clamping systems can introduce vibration absorption, as the vacuum seal between the workpiece and the table surface can act as a cushion, reducing the transmission of vibrations. In the case of electromagnetic clamps, vibrations can potentially cause wear and tear on electromagnetic chuck components, leading to increased maintenance requirements and a reduced lifespan.