Volume 10, Number 4 • July/August 2002 • Moving Forward

Technology Opportunity Showcase highlights 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.

Langley Scanning Thermography

NASA Langley is seeking licensing partners for their Scanning Thermography technology. The subject technology is a transportable scanning thermographic system for nondestructive evaluation or testing (NDE/NDT) of materials for cracks, flaws, disbonds, corrosion and wear.

A carriage conveys a heat source and a thermal imager at a constant speed over a test surface structure. The imager follows the heat source and produces a video image of the thermal characteristics of the test surface as the induced heat is diffused. Temperature differences indicate regions of differing heat diffusivity. Because damaged, corroded or disbonded areas are thinner, and dissipate heat differently from unaffected sections, they show a corresponding difference in temperature. The

system’s infrared imager converts this thermal response into a video signal, which is analyzed by an attached microcomputer and image processor.

Material defects produce deviations from the induced surface temperature that move at a speed proportional to the constant speed. Thermal noise produces deviations that move at random speeds. Computer averaging of the digitized thermal data with respect to the constant speed minimizes noise and improves the signal of valid defects. The motility and high scan rates of the thermographic equipment coupled with the high signal-to-noise ratio render the system suitable for portable, on-site analysis. Technicians can then examine the system’s digital output in real time for a precise diagnosis of structural degradation.

The advantages of NASA’s thermographic imaging method include noninvasive and noncontacting; suitability to a wide range of materials including composites and metals employing aluminum, plastic and resin matrices; real-time imaging; transportable/in-service use; rapid coverage of large areas of varying shapes (six times that of point-and-shoot methods); good defect resolution (dependent on depth of material), especially for disbonds, delaminations and corroded areas; scanning speed of over six feet per second; and relatively inexpensive equipment. Q

For more information, contact the Robert C. Byrd National Technology Transfer Center, phone: 800/678-6882, hottechnologies@nttc.edu. Please mention you read about it in Innovation.

3-D Roller Locking Sprags

NASA invites commercial companies to license the 3-D roller locking sprag technology for use in commercial applications.

Originally developed at NASA Goddard Space Flight Center, this technology provides a solution to torque-coupling locking brake and clutch applications that are too demanding for conventional sprag brakes/clutches. NASA’s 3-D roller locking sprag brake/clutch provides superior holding torque at a reduced size and weight.

Many machines with rotating parts use brakes and clutches to stop or control the degree and direction of motion of the driven parts. Brakes and clutches often are incorporated between concentric races (i.e., rotating shafts). One class of locking brake/clutch uses spherical balls or cylindrical rollers located between an inner and outer race. At least one of the races contains cam surfaces against which the balls or rollers wedge and lock to produce instantaneous torque coupling. A variation on this approach incorporates the cam shape into the roller (i.e., sprag), which rotates through a small angle to engage the sprag’s cam surfaces against the concentric cylindrical surfaces of the inner and outer races. Springs often are used to preload the sprags against the race surfaces so that the sprags engage and disengage instantly with no backlash.

NASA’s innovative 3-D roller locking sprag has a tapered periphery and replaces the concentric, cylindrical surfaces of the inner and outer races of the brake/clutch with grooves into which the 3-D sprag fits. This geometry creates four points of locking contact–two between the outer taper of the 3-D sprag and the outer grooved race, and two between the inner taper of the 3-D sprag and the inner grooved race–twice as many as with conventional, simple ball-based roller locking brakes/clutches. The two additional contact points increase the locking efficiency of the device while reducing the level of sprag-to-race contact stresses. In conventional cylindrical roller sprags, the roller contacts the races along the full length of the roller sprags. However, NASA’s 3-D roller locking sprag contacts only the diametrically opposing sides of the grooved races at the four points noted above, reducing contact stress and increasing holding power. Q

For more information, contact Darryl Mitchell at Goddard Space Flight Center, phone: 301/286-5169, Darryl.R.Mitchell.1@gsfc.nasa.gov. Please mention you read about it in Innovation.