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The present work discusses the fabrication of low-cost, reliable and durable flexible electronic circuits from conductive carbon paste on flexible polyethylene terephthalate (PET) substrate using microdispensing direct ink write technique. Printing parameters such as pressure, substrate speed and gap size are optimized through Box-Behnken experimental design technique to achieve the desired quality of prints (patterns). For the nozzle with an inner diameter of 200 µm, the system is able to produce pattern line width ranging from 198 µm to 295 µm, respectively. Based on optimized parameters, circuits such as foil grid and rectangular spiral are printed on a flexible PET substrate. The deposited patterns of circuits are morphologically characterized by optical microscopy and scanning electronic microscopy. Current-Voltage (I-V) characteristic is performed to evaluate the conductive performance of circuits. The sensitivity of circuits to bending is assessed by studying resistance response under fully bend and unbend angle of 90° and 0°. Durability and reliability of circuits are analyzed by subjecting circuits to continuous 500 bend cycles and study its resistance response. The analysis revealed that these direct ink write circuits are reliable, durable and stable in performance and are applicable to the flexible electronic application.

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Welding distortion is a critical issue as it leads to severe deterioration of structural integrity of welded work piece and dimensional precision. This study aims at studying the effects of shielded metal arc welding (SMAW) parameters on the evolution of mechanical properties, including tensile strength, impact toughness, and hardness, along with angular distortion on a welded joint from SA 516 grade 70. Such parameters are analyzed and optimized by employing the Taguchi method and Grey relational analysis. SA 516 grade 70 is commercially used for fabrication of storage tanks, boilers and pressure vessels. SMAW is investigated with three levels of root gap, groove angle, electrode diameter, and pre-heat temperature, which were varied on a butt joint in flat (1 G) position to determine their effects on response variables at room temperature. Nine experiments were designed using a Taguchi L9 orthogonal array, welded according to American Society of Mechanical Engineers (ASME) section IX, and samples were prepared and tested as per ASTM A 370. The Taguchi method and Grey relational analysis were employed to observe the most significant parameters and optimal levels that synergically yield improved responses. Results are validated by conducting confirmatory experiments that show good agreement with optimum results.

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