A. V. Filippov

Structure and tensile fracture of 1570C aluminum alloy

Both deformation and fracture tensile studies on orientation dependence of 1570C aluminum alloys samples with respect to rolling direction have been carried out. As revealed, the viscous fracture mechanism is more inherent to the samples with orientation transversal to the rolling direction while samples oriented along the rolling direction revealed quasi-brittle areas on the fracture surfaces. Despite practically the same level of the yield stress there is 10% difference I the ultimate stress.

Effect of friction stir welding parameters on defect formation

Friction stir welding is a perspective method for manufacturing automotive parts, aviation and space technology. One of the major problems is the formation of welding defects and weld around the welding zone. The formation of defect is the main reason failure of the joint. A possible way to obtain defect-free welded joints is the selection of the correct welding parameters. Experimental results describing the effect of friction stir welding process parameters on the defects of welded joints on aluminum alloy AMg5M have been shown. The weld joint defects have been characterized using the non-destructive radioscopic and ultrasound phase array methods. It was shown how the type and size of defects determine the welded joint strength.

Experimental Research Into Generation of Acoustic Emission Signals in the Process of Friction of Hadfield Steel Single Crystals

The results of experimental research into dry sliding friction of Hadfield steel single crystals involving registration of acoustic emission are presented in the paper. The images of friction surfaces of Hadfield steel single crystals and wear grooves of the counterbody surface made after completion of three serial experiments conducted under similar conditions and friction regimes are given. The relation of the acoustic emission waveform envelope to the changing friction factor is revealed. Amplitude-frequency characteristics of acoustic emission signal frames are determined on the base of Fast Fourier Transform and Short Time Fourier Transform during the run-in stage of tribounits and in the process of stable friction.

Mathematical support for automated geometry analysis of lathe machining of oblique peakless round–nose tools

Automatization of engineering processes requires developing relevant mathematical support and a computer software. Analysis of metal cutting kinematics and tool geometry is a necessary key task at the preproduction stage. This paper is focused on developing a procedure for determining the geometry of oblique peakless round-nose tool lathe machining with the use of vector/matrix transformations. Such an approach allows integration into modern mathematical software packages in distinction to the traditional analytic description. Such an advantage is very promising for developing automated control of the preproduction process. A kinematic criterion for the applicable tool geometry has been developed from the results of this study. The effect of tool blade inclination and curvature on the geometry-dependent process parameters was evaluated.

Effect of adhesion transfer on the surface pattern regularity in nanostructuring burnishing

In the paper the influence of friction-induced adhesion of metal to the tool on the formation of surface topography under nanostructuring burnishing was studied. A comprehensive approach, including both experimental (optical microscopy and profilometry) and theoretical (computer-aided simulation) methods was used. The results showed a direct connection between values of adhesion strength of materials in contact with the workpiece surface pattern quality caused by the tool movement. Results of the experimental and theoretical study are in good agreement and allow us to identify the reason of regular profile forming during surface burnishing.

Adhesion transfer layer formation in sliding on equal-channel angle pressed ultrafine grained AA6063

The effect of equal-channel angle pressing (ECAP) conditions on wear resistance and adhesion of the resulted ultrafine grained AA6063 in sliding against a steel ball has been investigated. Using the 3D laser confocal microscopy the parameters of wear and adhesion transfer layer thickness on ultrafine grained AA6063 has been measured. As it was established, the ECAP at room temperature allowed forming AA6063 microstructure in sliding, which is more wear resistant and less prone to adhesion as compared to the previous one at higher temperatures. The effect of ECAP pass number n on the above parameters becomes negligible for n > 8. The wear resistance of AA6063 processed by ECAP at 200°C is improved only for n = 4 whereas n > 4 has only a negative effect.

Sliding dynamics on ultrafine grained Al–6 wt % Mg made by equal channel single pressing

The effect of ECAP pass number on wear, microhardness and tribological dynamic behavior of UFG Al– 6 wt % Mg alloy has been studied. The UFG Al–6 wt % Mg samples demonstrated higher wear resistance after 4 and 8 ECAP passes as compared to as-received alloys state. The dynamics of sliding and loudness level generated in sliding showed moderate increase of vibrations and noise on ECAP UFG samples.

Towards the effect of acoustic emission (AE) sensor positioning within AE signal parameters in sliding on bulk ultrafine-grained materials

The effect of AE sensor positioning on the bulk ultrafine-grained materials used for sliding against steel ball has been investigated. Two versions of AE sensor positioning have been tested and showed the different attenuation levels. The experimentally obtained AE signal waveforms have been analyzed under the AE signal parameters such as a median frequency and AE energy. It was established that the AE sensor positioned on the sample supporting plate in the vicinity of the sample tested allowed redistribution of the signal energy from a low-frequency to high-frequency range as well as extending the median frequency range as compared to those obtained by mounting the sensor on the immobile sample holder.

Application of 3D Сomputed Microtomography for Investigating the Microstructural Defects of Carbon Fiber Reinforced Composite Made by 3D-Printing

The microstructural defect of additive manufactured 3-component carbon fiber reinforced polymer (CFRP) composites has been studied using computed microtomography. The samples have been prepared using a 3D-printing process developed at Skolkovo Institute of Science and Technology, Russia. The research procedure has been described and internal defects of the fiber composite material have been detected and analyzed using a 3D image reconstructed from a number of cross section views. The defects larger 50 μm have been detected using the computed microtomography test. Defect-free images and defects typical for this type of composites such as delamination in polymer matrix and between fibers in a bundle, fiber breakage have been obtained.

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

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.