PSI - Issue 57

Marco Bonato et al. / Procedia Structural Integrity 57 (2024) 799–809 / Structural Integrity Procedia 00 (2019) 000 – 000

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Methods and Tools

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2.1. Simplification of Validation signal The vibration loading can affect both the mechanic and the electronic parts. The cumulative approach for the simplification of vibration signals needs to consider what is the expected failure mode, so that the criteria of equivalent fatigue damage content is satisfied. In both cases the criteria content based on equivalent damage is based on the Fatigue Damage Spectrum approach. In principle, the generic parameters considered were as follows (Bonato and Delaux (2015) and Bonato and Goge (2017)): - mechanical failure affecting the aluminum casing or brackets: Basquin’s b = 8 and damping ratio Q = 10 (5% damping) - electronic failure affecting the soldered joints on the PCB: Basquin's = 4 and damping ratio Q = 25 (2% damping) Next to these generic parameters, two more realistic combinations of the b and Q values were considered for the simplification of the signals. These values were tailored to the components underinvestigation, and were defined by data obtained from bench measurements, the material cards and a posteriori knowledge of the zone of failure. The additional settings are: - HVCH: failure affecting the brackets Basquin’s b= 8 and damping ratio Q = 25 (2% damping) - Alternator: failure affecting the aluminum casing - Basquin’s b = 10 and damping ratio Q = 17 (3% damping) The following sections will illustrate how two complex OEMS vibration specifications (a shock plus random, and a sine on random)were simplified into a purely random (PSD) or harmonic (Sine sweep) accelerated vibration tests, and the application of FEA simulation to validate the product design facing vibration damage. Overall, six signals were considered for the FEA fatigue calculations: three PSDs for the HVCH, and 3 sine sweeps for the alternator. The cumulated signals were generated by using software HBK nCode Glyphworks version 2022. 2.2. Shock-plus-Random for HVCH The Shock-plus-Random (SpR) validation signal is illustrated in Figure 3. The 21 hours duration PSD comes from the ISO 17500 standard, commonly applied for the components mounted on the body of the car. The series of shock pulses has a half sine shape with a period of 6 milliseconds and an amplitude of 30 g. A total of 1000 shocks were requested.

Fig. 3. (a) Half sine shock signal in time domain (b) Random vibration in frequency domain