Nikolay V. Druzhinin

Bio: Nikolay V. Druzhinin is an academic researcher from Russian Academy of Sciences. The author has contributed to research in topics: Modal analysis & Vibration. The author has an hindex of 1, co-authored 1 publications receiving 2 citations.

The Use of Laser-Doppler Vibrometry for Modal Analysis of Carbon-Fiber Reinforced Composite

Abstract: Both modal analysis procedure and the results obtained on a three-component 3D-printed carbon-fiber reinforced composite (CFRC) are presented. Experimental modal analysis of on the composite has been carried out to obtain the dynamic behavior characteristics. As revealed, the different eigen-oscillations waveforms possess different sensitivity of its amplitude frequency response to structural defects of the composite. For the similar waveforms we observed the differences in eigen-oscuillation frequencies, vibration velocities and damping factors which can be caused by the presence of numerous defects homogeneously distributed in one of the samples.

Studying Stability of CFRP Composites to Low-Energy Impact Damage by Laser Vibrometry

Abstract: Nondestructive quality control of small-thickness composites is an important scientific and technical problem due to significant damage inflicted on materials even with minor impact loads. The stability of a 1-mm–thick CFRP composite to impact damage with an energy of up to 10 J has been investigated. Special attention has been paid to the analysis of the “visible” area of defects formed as a result of successive striking with increasing and decreasing energy in the range from 1 to 5 J. The area of defect indications was estimated by analyzing the images of vibrations at the surface of the composite produced by its acoustic stimulation and laser vibroscanning.

Experimental and finite element analyses on the vibration behavior of 3D-printed PET-G tapered beams with fused filament fabrication

Abstract: PurposeThis study aims to reveal the influences of three-dimensional (3D) printing parameters such as layer heights (0.1 mm, 0.2 mm and 0.4 mm), infill rates (40, 70 and 100%) and geometrical property as tapered angle (0, 0.25 and 0.50) on vibrational behavior of 3D-printed polyethylene terephthalate glycol (PET-G) tapered beams with fused filament fabrication (FFF) method.Design/methodology/approachIn this performance, all test specimens were modeled in AutoCAD 2020 software and then 3D-printed by FFF. The effects of printing parameters on the natural frequencies of 3D-printed PET-G beams with different tapered angles were also analyzed experimentally, and numerically (finite element analysis) via Ansys APDL 16 program. In addition to vibrational properties, tensile strength, elasticity modulus, hardness, and surface roughness of the 3D-printed PET-G parts were examined.FindingsIt can be stated that average surface roughness values ranged between 1.63 and 6.91 µm. In addition, the highest and lowest hardness values were found as 68.6 and 58.4 Shore D. Tensile strength and elasticity modulus increased with the increase of infill rate and decrease of the layer height. In conclusion, natural frequency of the 3D-printed PET-G beams went up with higher infill rate values though no critical change was observed for layer height and a change in tapered angle fluctuated the natural frequency values significantly.Research limitations/implicationsThe influence of printing parameters on the vibrational properties of 3D-printed PET-G beams with different tapered angles was carried out and the determination of these effects is quite important. On the other hand, with the addition of glass or carbon fiber reinforcements to the PET-G filaments, the material and vibrational properties of the parts can be examined in future works.Practical implicationsAs a result of this study, it was shown that natural frequencies of the 3D-printed tapered beams from PET-G material can be predicted via finite element analysis after obtaining material data with the help of mechanical/physical tests. In addition, the outcome of this study can be used as a reference during the design of parts that are subjected to vibration such as turbine blades, drone arms, propellers, orthopedic implants, scaffolds and gears.Social implicationsIt is believed that determination of the effect of the most used 3D printing parameters (layer height and infill rate) and geometrical property of tapered angle on natural frequencies of the 3D-printed parts will be very useful for researchers and engineers; especially when the importance of resonance is known well.Originality/valueWhen the literature efforts are scanned in depth, it can be seen that there are many studies about mechanical or wear properties of the 3D-printed parts. However, this is the first study which focuses on the influences of the both 3D printing parameters and tapered angles on the vibrational behaviors of the tapered PET-G beams produced with material extrusion based FFF method. In addition, obtained experimental results were also supported with the performed finite element analysis.