This work presents an ultrafast laser (pulse duration<1 ps) direct-write technique for rapid prot... more This work presents an ultrafast laser (pulse duration<1 ps) direct-write technique for rapid prototyping and manufacturing of embedded microheater structures on thermal sprayed NiCr (80 wt.%/20 wt.%) alloy coatings. By combining thermal spray, an additive material process, and ultrafast laser micromachining, a subtractive material process, this technique shows considerable potential in fabricating small scale embedded functional parts within thermal spray coatings. Heater patterns designed to produce a uniform heat flux, a linear distributed heat flux, and a non-uniform heat flux that compensates for edge losses to produce a uniform temperature distribution have been fabricated and characterized. A stable working temperature of up to 500 °C measured in still air is observed, with fracture in the samples observed at higher operating temperatures. A mechanical analysis based on bimorph beam bending is presented to account for the failure mechanism of the laser-machined thermal spray microheaters at high temperatures, and recommendations are made for improved materials and fabrication parameters for high-temperature operation.
There is a growing demand for in situ monitoring of strain in high-temperature, harsh environment... more There is a growing demand for in situ monitoring of strain in high-temperature, harsh environment systems. Resistive strain gauges, while popular and easy to implement, have several disadvantages when used at high-temperatures. This work presents the design, fabrication, and initial testing of capacitive strain gauges for use in high-temperature, harsh environments. The gauges are fabricated using a direct-write thermal spray technology in which a computer-controlled deposition system is used to fabricate silver gauge patterns onto polymer, composite, and alumina substrates to form the strain gauges. Gauges were also fabricated using ultrafast laser micromachining of blanket NiCr coatings thermal sprayed onto an alumina substrate. The typical gauge capacitance was 4–25 pF. Mechanical measurements performed included gauge factor, linearity, and zero shift. Temperature-based measurements include the temperature coefficient of capacitance (TCC) and thermal cycling tests. The devices show promise for use in harsh environments and in wireless strain monitoring applications.
This work presents an ultrafast laser (pulse duration<1 ps) direct-write technique for rapid prot... more This work presents an ultrafast laser (pulse duration<1 ps) direct-write technique for rapid prototyping and manufacturing of embedded microheater structures on thermal sprayed NiCr (80 wt.%/20 wt.%) alloy coatings. By combining thermal spray, an additive material process, and ultrafast laser micromachining, a subtractive material process, this technique shows considerable potential in fabricating small scale embedded functional parts within thermal spray coatings. Heater patterns designed to produce a uniform heat flux, a linear distributed heat flux, and a non-uniform heat flux that compensates for edge losses to produce a uniform temperature distribution have been fabricated and characterized. A stable working temperature of up to 500 °C measured in still air is observed, with fracture in the samples observed at higher operating temperatures. A mechanical analysis based on bimorph beam bending is presented to account for the failure mechanism of the laser-machined thermal spray microheaters at high temperatures, and recommendations are made for improved materials and fabrication parameters for high-temperature operation.
There is a growing demand for in situ monitoring of strain in high-temperature, harsh environment... more There is a growing demand for in situ monitoring of strain in high-temperature, harsh environment systems. Resistive strain gauges, while popular and easy to implement, have several disadvantages when used at high-temperatures. This work presents the design, fabrication, and initial testing of capacitive strain gauges for use in high-temperature, harsh environments. The gauges are fabricated using a direct-write thermal spray technology in which a computer-controlled deposition system is used to fabricate silver gauge patterns onto polymer, composite, and alumina substrates to form the strain gauges. Gauges were also fabricated using ultrafast laser micromachining of blanket NiCr coatings thermal sprayed onto an alumina substrate. The typical gauge capacitance was 4–25 pF. Mechanical measurements performed included gauge factor, linearity, and zero shift. Temperature-based measurements include the temperature coefficient of capacitance (TCC) and thermal cycling tests. The devices show promise for use in harsh environments and in wireless strain monitoring applications.
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