Influence of ultrasonic agitation on the abrasive wear characteristics of Al-Cu/ 2 vol.% Grp composite

In the present study, the abrasive wear behavior of Al-4.4 wt.% Cu composite reinforced with 2 vol.% graphite particle (Grp) has been investigated. In the preparation of composite, Ultrasonic Treatment (UT) is provided in the composite melt for the uniform distribution of reinforcement particles. Two bond abrasive wear tests are conducted for composites treated with ultrasound and without UT and base alloy. The results of abrasive wear studies indicate that at 5 and 10 Newton (N) loads, the composite with UT has a higher coefficient of friction (COF) and wear resistance than that of the base alloy (Al-4.4 wt.% Cu). Whereas, at 15 and 20 N load, the value of COF and wear resistance is lower for the composite. Two abrasive wear mechanisms micro-plowing and micro-cutting have been observed during the wear tests of base alloy and composites. The analysis of worn-out sample surfaces at higher load reveals that softened material layer due to localized elevation in temperature between two contact surfaces during wearing acts as a tribolayer in base alloy while in composites both softened material layer and graphite layer have worked together as tribolayer.

Strain Amplitude Dependence of High Damping Grp/Mg97Zn1Y2 Composites Ranging from Anelastic to Microplastic

In this paper, the damping capacities and damping mechanisms of high damping, graphite-reinforced Mg97Zn1Y2 composites were investigated. Composites consisting of different graphite particle sizes (24, 11, and 3 μm) were designed and prepared using the casting method. The microstructure of the composites was examined using optical microscopy (OM) and transmission electron microscopy (TEM), which confirmed that the graphite particles were successfully planted into the Mg97Zn1Y2 matrix. Measurements made with a dynamic mechanical analyzer (DMA) showed that the Grp/Mg97Zn1Y2 composite has a high damping capacity. At the anelastic strain amplitude stage, the damping properties of the Grp/Mg97Zn1Y2 composites were found to be higher than those of the Mg97Zn1Y2 alloy. Furthermore, decreasing the graphite particle size was found to improve the damping properties of the Grp/Mg97Zn1Y2 composites. At the microplastic strain amplitude stage, the damping properties of the Mg97Zn1Y2 alloy were found to be higher than those of the Grp/Mg97Zn1Y2 composites. Moreover, the damping properties of the Grp/Mg97Zn1Y2 composites were found to decrease with increasing graphite particle size. The reason for the increased damping of the Grp/Mg97Zn1Y2 composites during the anelastic strain amplitude stage can be attributed to the increase in the number of damping sources and weak interactions among the dislocation damping mechanisms. At the microplastic strain amplitude stage, the damping properties of the composite are mainly affected by the activation volume of the slipped dislocation.

Manufacturing fine graphite powder with AC electric synthesis

There is presented a technology for manufacturing fine powder of graphite of GE type by means of synthesis. A device with the separation of anode and cathode area by means of Dacron diaphragm use is described. Basic elements of the installation are a stainless steel cathode and a graphite anode submerged into aqueous solution (electrolyte). As a result of the experiment there is obtained fine powder with an average graphite particle size of 4mkm.

Shear actuation-based hybrid damping treatment of sandwich structures using a graphite particle-filled viscoelastic layer

In this work, the effectiveness of a shear actuation-based hybrid active-passive damping treatment is investigated by incorporating the inclusion of graphite particles within the viscoelastic damping layer. The study is performed through the flexural vibration analysis of a sandwich plate-strip where the core is made of a laminate of active layers and graphite particle-filled viscoelastic layers in two different stacking sequences. The active layers are comprised of shear mode piezoelectric actuator patches that are activated according to a shear-based velocity feedback control strategy. The analysis is performed by deriving a closed-loop finite element model of the sandwich plate-strip, and it reveals that the hybrid damping is significantly dependent on the stacking sequence of active and passive damping layers at the core. The inclusion of graphite particles not only provides augmented passive damping but also causes enhanced transfer of shear actuation force from the active layers to other layers. As a result, a significantly improved shear actuation-based hybrid active-passive damping is achieved due to the inclusion. The effectiveness of this hybrid damping in attenuation of resonant displacement-amplitude is also presented by configuring the volume fraction of graphite particles and shear actuator patches in an optimal manner.