Fourth International Conference on Material and Component Performance under Variable Amplitude Loading
To search for a specific ID please enter the hash sign followed by the ID number (e.g. #123).

Special Loading Conditions

Session chair: Chmelko, Vladimir, Professor (Slovak University of Technology, Institute of Applied Mechanics and Mechatronics, Bratislava, Slovakia)
 
Shortcut: R
Date: Wednesday, 1. April 2020, 14:00
Room: Hall B
Session type: Oral

Contents

14:00 R-01

Comprehensive description and evaluation of a multi-physical testing process to simulate real conditions that affect the reliability and aging of high energy traction batteries for electric vehicles (#79)

A. Karthikeyan1, R. Zinke1, A. Schönemann1, R. Heim1

1 Fraunhofer-Institut für Betriebsfestigkeit und Systemzuverlässigkeit LBF, Systemzuverlässigkeit Future Mobility, Darmstadt, Hesse, Germany

The early evaluation of sources that affect the reliability and aging of high energy Li-Ion-battery-packs becomes more important with increasing demand for electric vehicles and with the increasing competition between the designers and operators of such battery systems. The main criteria to evaluate especially the battery pack’s electrical reliability and aging characteristics are capacity and power fade due to residual capacity loss and internal resistance increase. The reasons are multifold. On battery cell level, e. g. mechanical stress and strain during Li-Ion intercalation may lead to deformation, dilatation and cracks in the active materials, high current during charging and discharging may lead to critical heat production, thermal conditions outside ideal temperature ranges may lead to melting separators and short circuits. On battery system level, loose electrode connections, cracks and deformations in housings etc. from mechanical, electrical and thermal load sources contribute to performance loss, reliability decrease and aging. In order to experimentally simulate the real mechanical, electrical and thermal loading of battery systems that eventually lead to aging affects in real applications, multi-physical test facilities are needed that allow vibrational loading via adequate shaker systems, electrical charging and discharging via vehicle energy systems as well as temperature and humidity control via a climate testing environment. For example, vibrations of 200 Hz at 1.000 kg payload, electrical power of 250 kVA for charging and de-charging, temperatures from -40 °C to 80 °C, and humidity up 95 % need to be realized simultaneously for adequate testing.

The aim of this contribution is to show, discuss and evaluate the relevant specifications and processes needed for a multi-physical test procedure to simulate real conditions that have an effect on the reliability and aging of high energy Li-Ion-battery-packs. This includes, on the one hand, the handling during shipment of hazardous goods by meeting international standards, installation of the battery pack on a shaker table, transferring the real multi-dimensional variable amplitude loading via mechanical load spectra into the test control units, reduction of test time, residual bus simulation, pre-processing, test sequence control and others. On the other hand, safety measures to minimize thermal runaway, fire or explosions are important. The comprehensive description and evaluation of the multi-physical testing process helps to efficiently simulate real conditions that affect the reliability and aging of high energy Li-Ion-battery-packs.

References

Debes, Christian (2016): KOSTEN SPAREN MIT MULTIPHYSIKALISCHEN PRÜFVERFAHREN. In: emobilitytec 5. Jahrgang, S. 36–39.

Heim, Rüdiger; Dautfest, Alexander; Flaschenträger, David; El Dsoki, Chalid (2015): Systemzuverlässigkeit von Hochvolt-Batterien für Elektrostraßenfahrzeuge. In: ATZ Elektron 10 (5), S. 40–45. DOI: 10.1007/s35658-015-0594-x.

Keywords: reliability, variable amplitude loading, multi-physical test, experimental simulation, high-energy traction battery
14:01 R-02

Relevance of strong motion portion of a synthesized time-history for strength and functional validation in earthquake simulation (#103)

F. Bösl1

1 IABG mbH, Ottobrunn, Germany

Seismic qualification is necessary, especially for equipment being installed in earthquake prone regions. There are various methods to qualify components, starting from experienced based data evaluation up to a physical shake-table test. For shake-table testing, again various methods exist, whereas the most common method, considering the relevance of strong motion portion, will be presented in the following.
In shake table testing regarding earthquake simulation of i.e. non-structural components, the most common way to describe the input motion of the shake table is by comparing the Test Response Spectrum (TRS) with the Required Response Spectrum (RRS). The Response Spectrum (RS) is a plot of the maximum response, as a function of oscillator frequency, of an array of single-degree-of-freedom (SDOF) damped oscillators subjected to the same base excitation. The RS provides the information, if each required frequency content is excited sufficiently. However, it supplies neither the waveform of excitation that produced it, nor the duration of motion and especially the strong motion portion of the signal. A common way for i.e. test laboratories is to develop the input motion out of a given RRS, which has to be enveloped by the calculated TRS from the actual time history of the motion of the shake table. Many standards require an input motion of 30 s with a strong part motion of around 15 s to 20 s. The definition of strong part motion in several standards varies, or is even not defined at all. The following example shows two test scenarios, in which the requirement of fulfilling the enveloping of the RRS by the TRS is given in a comparable manner for each load cases, whereas the applied input motions are different regarding the strong part motion. Though those two test scenarios having an equal TRS, the equipment under test (EuT) show different test results regarding material fatigue. This example shows the importance of the development of a synthesized time-history, considering the strong part ratio of the signal.

Keywords: earthquake, simulation, time-history
14:02 R-03

Ringing conditions, durability life and sound quality of church bells (#139)

A. Rupp1, M. Plitzner1

1 University of Applied Sciences Kempten, Kempten, Germany

For centuries bells have been a vital expression of our culture and history. The importance for European history shows up in very different and diverse uses over the centuries for religious and secular occasions. Each time bells were silent, life, liberty and humanity were directly threatened. Thus bells are valuable cultural assets that should be preserved for future generations.

Bells are musical instruments operated like machines with necessary technical equipment engine, drive and control and exposed to severe loading conditions by the clapper. Many especially large and famous bells were damaged by ringing over decades and centuries. Often fatigue cracks have been observed due to high stress conditions under the vibrations of ringing. The repair or restoration is very expensive or even not possible and thus often valuable cultural heritage is irrecoverable destroyed.

The European competence center for bells ECC-ProBell at the University of Applied Sciences of Kempten has performed extensive investigations on the parameters determining the life of bells and on methods to evaluate the risk for damages on bells in service. The most important operating parameter is the intensity of the clapper-impact, which is determined by the mass, the weight distribution, the material and the contact conditions as well as the approaching speed and direction of the clapper to the swinging bell. The impact results in the stress conditions and the emitted sound. Each bell system is unique and thus needs to be optimized for its very specific set of parameters. Computer models and respective data were developed, to allow for an optimization of the parameters and ringing conditions of such bell systems, to minimize the risk for damages and at the same time to guarantee for a high musical quality.

In this presentation, the correlation of the dynamic stress conditions with the quality of sound is reported. The sound of a bell consists of many tones which are achieved by the unique shape of the bell body. However, the quality of the sound of the bell can be described not only by the actual tones and their intervals but more by the mixture, how such tones are excited by the clapper impact. The clapper impact lasts not longer than about half a millisecond – thus to design the sound of a bell in view of tone excitation requires to design the conditions of such short contact. As a consequence the set up of bell systems especially in view of a long life under ringing conditions with a high musical quality are discussed. A new monitoring system including a public science community is finally presented based on the elaborated methods and data.

Figure 1
Keywords: Ringing conditions, sound quality, church bells