Deriving inspiration from the propulsion methods of squids, a pulsatile jet propulsion system is adopted in a robotic model. A squid-like direction control mechanism, which can direct the jet along any direction on a hemispherical work volume, is also implemented. To obtain a suitable robot velocity (v)and a propulsive efficiency (ηp) for testing this mechanism, the stroke ratio (L/D) and outlet diameter are varied and thevand the ηpof various alternatives are estimated experimentally using vision analysis. A Stroke ratio of 3.78 and an outlet diameter of 25.4 mm were found suitable and employed for testing the mechanism. When the jet is deflected by 60° in the horizontal plane, the robot rotates about its centroid, signifying excellent maneuverability. Reverse motion was also demonstrated by removing inlet valves and blocking the outlet through the direction control mechanism. The performance of the direction control mechanism indicates that the robotic model was a feasible alternative to conventional screw-propelled aquatic robots.

Purpose Stainless steel is one of the most important elements in structural design and application, and due to its excellent properties, it is widely used in industries for conventional structural engineering applications, such as thermal power plants, nuclear power plants, civil constructions, etc. (Mishra et al., 2014). A traditional tensile testing machine cannot determine the transversal stress–strain curves (Olden, 2002, 2013). Design/methodology/approach In the present study, identical mild steel specimen parts are welded at different intervals and then subjected to tensile loading. Welding is carried along the length of the specimen. Induced stresses are determined at the welded intervals and the stress–strain curve is obtained. Findings By considering the temperature of the weld at the interface, thermal stresses are determined. Brinell hardness number is determined at the interface and the base metal. Also, the change in the hardness at the heat-affected zone (HAZ) is found. Validation is carried out by comparing the results with the original stress–strain curve. Originality/value In the HAZ, there is a drop in the hardness number, which means that there is a change in the material property due to welding. The thermal stresses which develop at the interface can also play a very important role for property change. Results show that the stress developed due to the rise in temperature is lesser than that of normal stresses.