Volume 9, Number 6 • November/December 2001 • Moving Forward

Technology Opportunity Showcasehighlights some unique technologies that NASA has developed and which we believe have strong potential for commercial application. While the descriptions provided here are brief, they should provide enough information to communicate the potential applications of the technology.or more detailed information, contact the person listed. Please mention that you read about it in Innovation

CARES/Life Software Tool

To be commercially viable, microelectromechanical (MEMS) devices must be manufactured cost-effectively with high yield rates, and they must survive their intended application environment over the projected service life. It is an essential element in product development that a risk assessment be performed prior to full-scale manufacture. The Life Prediction branch of the NASA Glenn Research Center, a world leader in brittle-material design methodology development, has developed CARES/Life (Ceramics Analysis and Reliability Evaluation of Structures/Life) software that characterizes and predicts the integrity of brittle-material structures.

CARES/Life is already a widely recognized program used by hundreds of organizations worldwide. It has won a NASA Software of the Year Award, an R&D 100 Award and a Federal Laboratory Consortium Award. Several organizations have already requested this program for MEMS-specific applications, including sensor arrays for spacecraft, piezoelectric ceramic sticks for inkjet print heads and micro-turbine development. CARES/Life is suitable for MEMS reliability evaluation of brittle materials and is currently used for polycrystalline (isotropic) materials. It is the most useful for harsh environment applications that challenge the capabilities of existing materials. CARES/Life quantifies the inherent wide dispersions in strengths introduced by etching-induced pits and edge flaws, and it enables part integrity assessment prior to manufacture, reliability to be tracked as a function of the part’s time in service under sustained and repeated loadings, and rapid prototyping of design before the actual hardware is produced. The CARES/Life design methodology combines the statistical nature of strength-controlling flaws with the mechanics of crack growth to predict the probability that a brittle material component will fail as a function of its time in service. This methodology accounts for multi-axial stress states, concurrent flaw populations, slow crack growth, proof testing and component size and scaling effects.

CARES/Life interfaces with commercially available finite element software such as ANSYS or ABAQUS. It can also use test data from specimen rupture tests to obtain the statistical (Weibull) and fatigue parameters required for device life assessment. CARES/Life is currently available as beta-test software to US-based organizations (foreign distribution is considered on a case-by-case basis). Q

For more information, contact Noel N. Nemeth at NASA Glenn Research Center, 216/433-3215, Noel.N.Nemeth@grc.nasa.gov. Please mention you read about it in Innovation.

Remote Pressure Transducer Health Check

Kennedy Space Center is seeking companies to license and commercialize the Remote Pressure Transducer Health Check technology—a process for remotely checking various parameters of a pressure transducer to determine if it requires calibration. In remote locations, wide margins of safety are used to compensate for the degradation of the measurement devices installed over time. This leads to a need for additional resources, increased technical support and the added costs associated with these needs. This technology is designed to accurately determine the health of the measurement device by an in situ check of the sensor’s major operating parameters.

Potential commercial uses of the technology include use in pressure transducer manufacturing; by end-users of pressure transducers; for oil company pipeline maintenance; and for water company pipeline maintenance. This technology permits remote measurements of the sensitivity, linearity, hysteresis, temperature, thermodynamic pressure and repeatability of a pressure transducer; decreases redundant measurements through remote-signal-indicating calibration; decreases the amount of time and possible errors during system failures; and extends the life of devices installed in an operating environment by reducing the number of times a pressure transducer requires removal for laboratory calibration. In the health check procedure, a fixed change, either above or below, in ambient pressure is measured. This is performed by first sealing an enclosed volume around the transducer with a valve. A piston inside the sealed volume is then driven forward, compressing the enclosed gas, thereby increasing the pressure. A fixed pressure below ambient pressure is obtained by opening the valve, driving the piston forward, sealing the valve and then retracting the piston. The output of the pressure transducer is recorded for both the over pressuring and the under pressuring.

By comparing the data with data taken during a preoperative calibration, the health of the transducer is determined from the linearity, hysteresis and the repeatability of its output. The addition of an adiabatic decompression/expansion phase to the health check allows the comparison of the thermometer and the manometer through the thermodynamic equation of state for the gas. This would determine if there exists a constant offset error in the manometer. Q

For more information, contact Lynne Henkiel at NASA Kennedy Space Center, 321/867-8130, Lynne.henkiel-1@ksc.nasa.gov. Please mention you read about it in Innovation.