This paper reports a self-aligned three-dimensional process (3D-SOULE) that incorporates batch-mode micro ultrasonic machining (μUSM), lapping and micro electro-discharge machining (μEDM) for fabrication of concave and mushroom-shaped spherical structures from hard and brittle materials. To demonstrate the process, 1 mm structures are fabricated from glass and ruby spheres. The μEDM technique is used to create the tool for μUSM from stainless steel spheres. Stainless steel 440, which provides a tool wear ratio <5%, is chosen as the tool material. A 2 × 2 array is used for batch processing. For an ultrasound generator frequency of 20 kHz and a vibration amplitude of 15 μm, machining rates of 24 and 12 μm min −1 are obtained for glass and ruby spheres, respectively. An approximate linear relationship is observed between the measured roughness (R a) of the machined surface and the product of the fracture toughness (K IC) and the hardness (H) of the workpiece material (K IC 3/2 H 1/2).
Measuring the extent of flow of viscous fluids inside opaque molds has been a very important parameter in determining the quality of products in the manufacturing process such as injection molding and resin transfer molding. Hence, in this article, an ultrasonic torsional guided wave sensor has been discussed for monitoring the movement of flow front during filling of resins in opaque molds. A pair of piezoelectric normal shear transducers were used for generating and receiving the fundamental ultrasonic torsional guided wave mode in thin copper wires. The torsional mode was excited at one end of the wire, while the flowing viscous fluid progressively wet the other free end of the wire. The time of flight of the transient reflections of this fundamental mode from the air-fluid interface, where the wire enters the resin, was used to measure the position of the fluid flow front. Experiments were conducted on four fluids with different viscosity values. Two postprocessing algorithms were developed for enhancing the transient reflected signal and for suppressing the unwanted stationary signals. The algorithms were tested for cases where the reflected signals showed a poor signal to noise ratio.
This paper presents the efforts at micro thermal stimulation to initiate the flight and control the direction of beetles. Experiments were carried out by mounting micro thermal stimulators at the base of the antenna of the Green June beetle (Cotinis nitida). Preliminary in vivo experiments with resistive micro-heaters demonstrate that the beetle generates a torque of 18mN-mm at an estimated temperature of 43°C at the beetle-heater interface. These experiments utilized a micromachined resistive heater fabricated from bulk Ni foil. Additional experiments with a beetle carcass indicate that ultrasonic heating could be more effective, providing an estimated interface temperature of 43°C with 160 mW power. A circular PZT-5H disk of 3.2 mm diameter was used in the experiments.
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