Waste Heat Recovery from Metal Casting and Scrap Preheating Using Recovered Heat

AbstractIn metal casting, after solidification of the molten metal in the mold cavity, the knocked out casting has heat energy stored it and is wasted into atmosphere as the casting cools down in the shop floor. If this heat energy can be absorbed by the raw materials by a suitable arrangement, it will reduce energy consumption during melting, resulting in savings in economy and environment. This paper discusses an innovative approach to implement such a methodology. In a basic set up, when this preheating was achieved, the scrap was found to take 2.83% less energy than it would take to melt without this preheating set up. This technique has been improvised by keeping aluminum powder in between the scrap and the hot casting to have better heat recovery, resulting in an increase of heat recovery to the tune of 5.7%. When this savings are applied to global castings produced, which run into millions, the total energy and emissions saved amounts to a substantial figure. The calculations indicate energy savings as high as 419 GWh, which translates roughly to Rs 377 crores a year for Indian foundries in one year

Influence of microstructure on the failure of ultra-high molecular weight polyethylene composite beams impacted by blunt projectiles

Increasing the fibre tensile strength is well-known to improve the ballistic performance of ultra-high molecular weight polyethylene (UHMWPE) fibre composite beams. Here we investigate modifying ply microstructure as an alternate way to enhance ballistic performance. Specifically, we numerically investigate the mechanisms via which failure is initiated in [0o/90o]nlaminates comprising UHMWPE tape plies and compare with the commonly used UHMWPE fibre composites. Each ply of the beam is discretely modelled using a pressure-dependent crystal plasticity framework with the deformation mechanisms of the tape and fibre-based microstructures modelled by recognising differences in the available slip system in these two material systems. The numerical calculations are used to construct failure mechanism maps for a range of impact velocities, ply shear strengths and ply tensile strengths. Three dominant failure mechanisms emerged from the study: (i) failure of plies immediately under the projectile via an indirect tension mechanism in which compressive stress imposed normal to the plies by the projectile induces tensile in-plane ply stress due to the anisotropic expansion of the alternating 0o/90o plies; (ii) failure due to tensile straining at the rear of the impacted beam resulting from a combination of beam bending and stretching and (iii) a shear plugging like failure mode due to tensile straining at the edge of the impact site. Tensile stress generation by indirect tension is significantly reduced in the tape-based microstructures due to the unavailability of the slip systems that result in lateral plastic expansion. In fact, our calculations suggest that over the entire range of parameters modelled here the tape-based microstructures outperform the fibre-based microstructures. This suggests an alternate route to enhancing the ballistic performance compared to the traditional methods that rely mainly on increasing fibre strength