Engineering topics
Blecke, Jill
Publications and source records attributed to Blecke, Jill.
Off-Axis Input Characterization of Random Vibration Laboratory Data for Model Credibility.
Abstract not provided.
Carbon Composite Microelectromechanical Systems (CMEMS)
Pyrolyzed carbon as a mechanical material is promising for applications in harsh environments. In this work, we characterized the material and developed novel processes for fabricating carbon composite micro-electromechanical systems (CMEMS) structures. A novel method of increasing Young's modulus and the conductivity of pyrolyzed AZ 4330 was demonstrated by loading the films with graphene oxide prior to pyrolysis. By incorporating 2 wt.% graphene stiffeners into the film, a 65% increase in Young's modulus and 11% increase in conductivity were achieved. By reactive ion etching pyrolyzed blanket AZ 50XT thick film photoresist, a high aspect ratio process was demonstrated with films >7.5um thick. Two novel multi-level, volume-scalable CMEMS processes were developed on 6" diameter wafers. Young's modulus of 23 GPa was extracted from nanoindentation measurements of pyrolyzed AZ 50XT films. The temperature-dependent resistance was characterized from room temperature to 500C and found to be nearly linear over this range. By fitting the results of self-heated bridges in an inert ambient, we calculated that the bridges survived to 1000C without failure. Transmission electron microscopy (TEM) results showed the film to be largely amorphous, containing some sub-micrometer sized graphite crystallites. This was consistent with our Raman analysis, which also showed the film to be largely sp 2 bonded. The calculated average density of pyrolyzed AZ 4330 films was 1.32 g/cm 2 . Thin level of disorder and the conductivity of thin film resistors were found to unchanged by 2Mrad gamma irradiation from a Co 60 source. Thin film pyrolyzed carbon resistors were hermetically sealed in a nitrogen ambient in 24-pin dual in-line packages (DIP's). The resistance was measured periodically and remained constant over 6 months' time.
Highly stretchable miniature strain sensor for large dynamic strain measurement
In this paper, a new type of highly stretchable strain sensor was developed to measure large strains. The sensor was based on the piezo-resistive response of carbon nanotube (CNT)/polydimethylsiloxane (PDMS) composite thin films. The piezo-resistive response of CNT composite gives accurate strain measurement with high frequency response, while the ultra-soft PDMS matrix provides high flexibility and ductility for large strain measurement. Experimental results show that the CNT/PDMS sensor measures large strains (up to 8 %) with an excellent linearity and a fast frequency response. The new miniature strain sensor also exhibits much higher sensitivities than the conventional foil strain gages, as its gauge factor is 500 times of that of the conventional foil strain gages.
NMSBA High Frequency Modal Analysis of a Solid Metal Cylinder using a Polytec 3D Scanning Laser Vibrometer
Abstract not provided.
Highly Stretchable Miniature Strain Sensor for Large Strain Measurement.
Abstract not provided.
NMSBA High Frequency Modal Analysis of a Solid Metal Cylinder
This memo documents the results and methodology of the high-frequency modal test performed on a solid metal cylinder, provided by Vibrant Corporation, in September 2014 at Sandia National Laboratories. The purpose of this test was to measure mode shapes of the unit (torsion, axial, and bending) as high in frequency as achievable with a Polytec PSV-400 scanning laser Doppler vibrometer.
A Wiki for Sharing Substructuring Methods Measurements and Information.
Abstract not provided.