Epoxy underfills can be implemented in electronic packaging to enhance solder joint reliability of surface mounted components. However, it is important for an engineer to have a failure criterion that can be used for failure predictions and redesign of electronic assemblies. Data from epoxy bond failure in mock electronic part assemblies were correlated to finite element analyses to predict adhesive failure initiation. Experiments were performed to determine failure loads for various loading locations and nonlinear viscoelastic analyses were performed for the same loading locations to determine a maximum principal strain failure parameter. Predictions showed that a maximum principal strain failure parameter defined from one test could be used as an indicator of adhesive failure of an epoxy bond undergoing other modes of loading. Failure initiation predictions matched experimental data using a maximum principal strain failure parameter for an epoxy bond undergoing mixed modes of loading for both unfilled and alumina oxide filled 828DEA epoxy. vi Table of
This paper aims to provide performance optimisation of a multirotor drone that is designed for underground spaces. Currently, drones are being used efficiently for various applications in surface fieldwork projects. But using drones for underground spaces is challenging because of confined space, GPS-denied environment and various air properties in underground spaces. In this paper, first, the designed and manufactured drone is discussed. Then, to improve the drone performance for defined missions, a sensitivity analysis is done over the effective design parameters of the drone components and air density as an environmentally effective parameter. The sensitivity analysis over the flight simulations shows that drone performance increases by increasing air density, while the optimised number of propellers blades is presented. The results show that by increasing the battery capacity, the flight time increases but the overall performance of the drone decrease. Also, the drone would be able to carry about 450 grams payload and payloads more than 450 grams can significantly decrease flight time. Finally, the results of sensitivity analysis lead to optimise the drone performance efficiently for the designed mission in underground mines.
This study focuses on a novel steering method for supersonic fin-stabilised projectiles using pin-based mechanical micro-actuators implanted at the rear of the ammunition. When supersonic cross-flows and aerodynamic structures generated by the neighbouring tail fins are acting on the projectile, complex interactions between the boundary layer and the pin-induced shockwaves will occur around the actuator. To understand the underlying physical phenomena and to determine how these flow structures could be simulated with steady-state CFD simulations, fundamental wind tunnel investigations have first been performed on a flat plate by means of pressure sensitive paints (PSPs) and particle image velocimetry (PIV) measurements. The resulting conclusions have then been applied to the controlled ammunition. Parametric CFD calculations determined the optimal area where the actuator should be implanted. Six degrees of freedom (6DoF) simulations provided the resulting trajectory. These predictions have finally been compared to free-flight deviation measurements to validate the steering methodology and to quantify the prediction error resulting from successive aerodynamics and flight mechanics simulations.
