PSI - Issue 42

Iulian-Ionut AILINEI et al. / Procedia Structural Integrity 42 (2022) 1422–1427 Author name / Structural Integrity Procedia 00 (2019) 000 – 000

1423

2

1. Introduction In the last three decades, much research has been focused on vibration-based fatigue failure of structures by monitoring their modal parameters, Mazurek and DeWolf (1990); Salawu (1997), Yan et al. (2007) and Moisa (2021). Any shift in natural frequency, damping loss factor or change of modal shape indicates that the internal microstructure of th e part’s material is starting to decay. The experiments presented in the current paper demonstrate that even anisotropy of sheet metals has a significant influence on the vibration response of the structures and should be considered when designing parts subjected to high cycle fatigue, like the ones used in the automotive industry. Vanlanduit et al. (2009) performed a fatigue test on an electro-dynamical shaker with simultaneous natural-frequency tracking. Their research showed the benefits of using the multi-sine signal for excitation: a low-frequency fatigue load and a high-frequency dynamic load. George et al. (2004) improved the method after noticing the change in the specimen’s natural frequency during the fatigue testing . Therefore, manually adjusted the excitation frequency to keep the deviation of the actual load stress from the desired load stress within 5 per cent. Cesnik et al. (2012) added a real time control software automatisation of the near resonance harmonic excitation based on monitoring the phase angle and the principal stress in a predefined fatigue notch zone. Real-time control allowed the excitation signal adjustment to maintain the stress load's desired constant value during the accelerated fatigue test. This paper aims to characterise the anisotropy of the S600MC steel sheet subjected to vibration. The report is divided into four sections. The first section presents the experimental investigation, followed by the numerical analysis. The main results and discussion are shown in the next section, while the main conclusions are summarised in the last quarter. 2. Experimental investigations The influence of anisotropy on vibration behaviour was analysed considering the directional dependencies of the properties of the plastic material for 3.0mm thick S600MC sheet metal. The test specimens were laser cut at orientations θ=0°, 45°, and 90° with respect to the rolling direction as depicted in Fig. 1.

Fig. 1. Test specimen orientation on sheet metal

Three specimens were tested for each orientation. The geometry of models with a 12.5mm wide and 75mm long gauge section follows ISO 10113:2006 standard. The specimen geometry specifications are depicted in Fig. 2.a.

Fig. 2. a) Specimen dimensions according to the ISO 10113:2006 standard, and b) Vibration test setup.