tip sheet

For assistance call (505) 667-7000

GUMMY BEAR STRAIN

Researchers at Los Alamos National Laboratory have developed a specially designed type of Split-Hopkinson pressure bar tailored to evaluate the influence of high strain rates - the rate at which materials deform under stress - and temperature on the mechanical behavior of elastic compounds, such as plastic or rubber. For scientists who usually test metals, such materials are as rubbery as gummy bear candies. Traditional Hopkinson bars and their data-acquisition techniques work best for materials with higher strengths. The new bar developed at Los Alamos is being used to evaluate the influence of strain rate and temperature on polymers, rubbers, plastics, binders used in explosives, polymer-bonded explosives and other extremely malleable materials. Moreover, strain rates for these materials can be tested at high and low temperatures: ranging from minus 55 degrees Celsius to plus 75 degrees Celsius. Strain data obtained from the bar tests are incorporated into material models for use in structural computer codes to describe the mechanical properties of materials. In addition to military and nuclear weapons stockpile stewardship applications, the researchers are using the high-rate testing for automobile and aircraft components to give manufacturers a clearer idea of how materials will hold up without having to perform numerous, expensive crash tests during component development. James E. Rickman, (505) 665-9203, elvis@lanl.gov

LOUDER PLEASE, I CAN'T SEE YOU

Los Alamos space scientists have patented a low-noise, high-speed output amplifier for charge-coupled devices, the components that convert light into electronic signals in video camcorders, the Hubble Space Telescope and hundreds of other high-performance scientific instruments. CCD devices, if run at very slow frame rates, are sensitive to individual photon events in starlight and other very dim conditions. The new amplifier permits the same ultra-sensitive image recording at 10 frames a second -- roughly 10 times faster than previous amplifiers and suitable for a wide range of new applications in engineering and process control. Jim Danneskiold, (505) 667-1640, slinger@lanl.gov

SLAP ME AND I'LL EXPLODE

Laser slappers, now under development at Los Alamos, represent the next generation of explosives detonators and are similar to electrical slapper detonators. In the laser slapper, a fiber optic transmits a laser pulse to vaporize a thin metal film. This film, or flyer as it is commonly called, is launched through a short barrel. The flyer shock loads, or slaps, high-density, pressed explosives, setting off a detonation. Laser slapper detonators offer a number of safety advantages over conventional detonators. Most importantly, they require very high peak laser powers to operate, making natural or accidental human-caused detonation very unlikely. Because light is transported over fiber optics, laser slappers avoid many of the electrical hazards associated with existing detonators. Finally, use of insensitive, secondary explosives makes these detonators safer to handle, manufacture, transport and deploy. Kathy DeLucas, (505) 665-9201, duke@lanl.gov

MICROWAVES IN FOR A TUNE UP

Most high-performance passive microwave and radio frequency devices need tuning after they are assembled and may require continual fine-tuning during their use, currently achieved with crude mechanical means like tuning screws. Using materials called nonlinear dielectrics, Los Alamos researchers have developed an electrical tuning method that offers great precision and continual broadband and fine tuning. An electric field induces changes in certain dielectric thin films that can be used to control electrical tuning. Easily adjusted for changes in requirements or equipment, dielectric tuners can be miniaturized and integrated into conventional circuitry. Better than semiconductors for some applications, they are well-suited for high-performance microwave equipment used in the wireless communications industry, that require high peak-power capacities or high switching speeds. Gary Kliewer, (505) 665-2085, garyk@lanl.gov

Los Alamos National Laboratory is operated by the University of California for the U.S. Department of Energy.

press releases