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Moisture content and chloride ion effect on the corrosion behavior of fitting brass (gate valves) used as a connection of PVC's conduits in aggressive sandy soil,

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Fretting fatigue is the main phenomenon inducing reduction of fatigue strength in overhead transmission conductor lines which are subjected to aeolian vibrations. Using the Bersfort ACSR 48/7 conductor, fatigue tests were conducted under several traction forces and relative vibration amplitudes. By metallographic examinations it has been observed that fretting induces microcracks which are mainly located between the keeper edge (KE) and the last point of the contact (LPC) of the conductor at the mouth of the suspension clamp. Under the fatigue tests conditions, several cross-sections of wires in the external layer of the conductor were instrumented using strain gauges. Wire strains recorded near to the suspension clamp show that the alternating strains were predominantly traction strains near the KE and that bending alternating strains become significant near the LPC. On the basis of fatigue tests results and assuming some simplified hypothesis, stress intensity factors were computed at the tip of cracks. The computed stress intensity factors take into account the combined effect of fretting behaviour at the contact points and both traction and bending stresses. The computed stress intensity factor ranges for low fatigue bending vibration amplitudes show good agreement with the endurance limit of the conductor.

Herein, we present a simple procedure for fabricating epoxy/graphite composites using a simple solution blending method. The addition of graphite filler in the epoxy matrix showed a beneficial effect on mechanical properties by enhancing Young's modulus up to 55.25% of its value. The highest thermal conductivity was obtained to be 1.53 ± 0.07 W· m−1· K−1, which depicts a fourfold increment as compared to the neat matrix. The effective thermal conductivity has been predicted using Nan model, which shows a satisfactory agreement with the experimental data. Besides, the investigated composites display enhanced electrical conductivity; this evolution of electrical conductivity as a function of filler volume fraction is well described using percolation theory. Thermogravimetry and differential scanning calorimetry have been used to determine the thermal properties of the composites as a function of filler volume fraction. These findings indicate that the thermal, electrical, and mechanical properties of epoxy/graphite composites could be ideal for thermal management and control of heat transfer devices.