The present work deals with temperature effects and parametric optimization in the drilling of continuous glass fiber reinforced epoxy composite. Drilling ability was examined operating a drilling system with different drill bits, feed rate, and spindle speed parameters. The investigation was performed by changing the tool and composite interface. Drilling experiments were carried out under the dry condition. Thrust force and drilling temperatures were measured using dynamometer and thermal camera. Peel-up and push-out delamination were evaluated using an image analyzing tool. Results show that the tribo-mechanical behavior of the drilling operation is affected at different levels by tool coating. This behavior is related to the intrinsic friction properties of coating nature. Response surface methodology was used in the evaluation of experiment results. The feed rate of 0.13 mm/rev, spindle speed of 2425 rpm and HSS-TiN drill bit are found as an optimum drilling parameters and drill type.

No abstract

No abstract

The potential of forming EN AW-2014 alloy in semisolid state was investigated. The EN AW-2014 slugs were partially melted at 610°C, to a liquid fraction of ∼15, before they were extruded into a solid bar with a diameter of 16 mm. The ram speed used in this process was much lower than that employed in thixoforging of the same alloy to maximise heat removal from the slug and to fully solidify the liquid fraction by the time the extruded bar exits the die. The high solid fraction employed was also of help in this regard. Forming during extrusion under these conditions took place largely via rotation of the α-Al globules over one another, producing a remarkable microstructure of predominantly uniform globular α-Al grains. The forming load was at least an order of magnitude smaller with respect to that measured during hot extrusion of the same alloy, underlining the benefits of extruding the hard to form 2XXX alloys in semisolid state. Having been largely drained of its liquid, the final part of the preheated slug, however, failed to enjoy extrusion under such favourable conditions. The large extrusion deformation and temperatures well above the liquidus point have led to dynamic recrystallisation, which is responsible for the equiaxed, instead of fibrous, grain structure in this region.

With copper as the main alloying addition, alloy from the 2XXX family offers high strength at low specific weight and are widely employed for aircraft, wheels and major structural components. However, they suffer from low forming speeds and require high forming pressures. Hence, it is very attractive to form these alloys in semisolid state for technical and economical reasons. In this study, one of the most important wrought alloys for aerospace applications, AA2014 was used. In order to form the best semi-solid forming products, thixotropic character must be known. For this purpose, AA2014 alloy ascast and warm extruded samples were heated to 600, 610 and 620°C in semi-solid region and held for 0, 5 and 10 min in the induction coil. All samples were cooled with water at room temperature. Microstructure analysis was conducted with metallographic methods and shape factor values were calculated. With increasing predeformation rate and heating temperature, the shape factor increases. Experimental results show that spherical shaped thixotropic microstructures which is required for semi-solid forming can be created in AA2014 alloy.