The overall acoustic echo of a submarine is greatly dependent on the conning tower. For enhancing the acoustic stealth performance of a submarine, it is necessary to research an innovative design scheme of the conning tower to reduce its target strength (TS). The aim of this work is to reduce the TS of a conning tower by varying its geometry and streamlining. The accuracy in modelling the acoustic scattering of a conning tower using the Kirchhoff approximation (KA) was validated, compared with finite element analysis (FEA). Several angular conning tower geometries were designed to analyze the effect of streamlining and the number of lateral facets on TS using the KA method. In consideration of the actual situation, the acoustic effect of backing medium was analyzed by compared water-filled elastic hulls with rigid hulls. From the observed TS calculation results, it is shown that the non-streamlined four lateral-facet conning tower geometries are optimal for acoustic stealth performance during the range of incidence angles from −10X to 10X, whereas the streamlined versions have better performance at incidence angles beyond this range. Furthermore, elastic hulls and rigid hulls provide similar spatial distribution regularities in monostatic configuration with the rigidity affecting the magnitude of the TS.

The study aims to investigate the effect of semisolid structure and strontium (Sr) addition on the wear behavior of hypoeutectic Al-Si alloy. Semisolid hypoeutectic Al-Si alloy was prepared using cooling slope casting with addition of 0 to 0.93 wt.% Sr. Microstructural study was done using an optical microscope. Vicker microhardness and pin on disc tribometer were used for microhardness and wear testing. When compared to conventional casting, the microhardness of the semisolid hypoeutectic Al-Si alloy improved by 9.8%. Sr addition at 0.43 wt.% resulted in a refined eutectic structure with a 17% increase in hardness over conventional casting. The globular structure α-Al formed during semisolid casting reduced porosity, and the addition of Sr refined the eutectic silicon into a fine fibrous structure that is tightly bound with the Al matrix. These are the primary factors that contribute to the high wear resistance in modified-Sr semisolid alloys.