Sneak Previews

Giving robots the gift of touch

"Imagine going through life only seeing things, but never being able to touch them," says Allison Okamura, an assistant professor of mechanical engineering at Johns Hopkins University. She is using specialized tactile sensors, joysticks, styluses, and control methods that enable robots to mimic a sense of touch. "In order to touch something, the robot has to interact with an object and manipulate it," says Okamura. She and other researchers at Johns Hopkins are programming robots to "touch and explore" unknown environments with tactile and force sensing. Her work is important to the development of robots and other machines that can perform tasks that are too dangerous or difficult for humans. The U.S. Navy, for example, wants robots that could feel their way through objects resting on the floor of an ocean. NASA is interested in robotic hands that could transmit information about the structure and strength of rocks on other planets. And back on Earth, doctors are considering the possibility of surgical robots that could differentiate between a blood vessel and a bone. Okamura says the work could also add entertaining dimensions to computer games and educational programs. She admits that some of the applications might not materialize for years, but her plans for now include writing new software for medical applications. For more information, contact Okamura at Johns Hopkins University, 3003 N. Charles St., Baltimore, MD 21218. Telephone: (410) 516-5251. FAX: (410) 516-5251.

Stress reduction in piezoelectric ceramics

Nancy Scottos, a professor of theoretical and applied mechanics at the University of Illinois (Urbana, IL) found a way to improve piezoelectric films. She and her research assistant Lei Lian observed that the thinner ceramic films become, the smaller their piezoelectric responses become. Their conclusion is that stresses within the films were the primary cause. "We can greatly improve their performance as tiny sensors and actuators," she says. How? To understand, consider that stress builds up in piezoelectric thin films during their fabrication. "Shrinkage and densification during the drying and firing processes cause stress," she says. Scottos and Lian confirmed their conclusions about thin films by exposing them to varying amounts of mechanical stress. By applying a small mechanical load in the opposite direction to the tensile strength, they were able to relieve residual stress on the film. Relieving the stress made the film's piezoelectric response 10 to 30% greater. For more information, write to University of Illinois, Talbot Lab, 104 S. Wright St., Urbana, IL 61801.

Tougher, heat-resistant plastics

BF Goodrich is testing a new patented method of mixing plastic with silica to create materials three to four times tougher than plastic alone. "We've primarily focused on the material's toughness, but its wear-resistance and impact strength are also beneficial properties," says John Lannutti, a professor of material science and engineering at The Ohio State University (Columbus, OH). What makes the patented method unique is that he and other researchers have forced melted plastic to fill the tiny holes in silica that are only 50 nm wide. The composite material is tougher than plastic because it divides the force of an impact into many small interactions involving millions of silica particles. "We apply pressure under a vacuum when the materials are hot, during their polymerization phase," says Lannutti. "The plastic penetrates and creates a strong bond between atoms of silica and plastic over a large surface area." Lannutti, working with Robert Seghi, an associate professor of restorative and prosthetic dentistry at Ohio State University, developed this method of producing tougher materials when the two were looking for a way to create plastic dental fillings. BF Goodrich is testing the material in bearings and bearing surfaces that could eventually be included in automotive and aerospace applications. The company supplies a polyamide plastic powder for Lannutti's experiments. "High-temperature plastics are often very brittle," says Lannutti. "Our process addresses this issue." The plastic withstands temperatures up to 800F, making it suitable for parts surrounding hot automotive and jet engines. For more information on the plastic processing method, contact Lannutti at (614) 292-3926 or e-mail lannutti.1@osu.edu .

Diagnosing the health and safety of aging aircraft

"Every airplane that flies has miles and miles of polymer-coated wires," says Tom Mason, a professor of materials science and engineering at Northwestern University (Evanston, IL). "The issue is determining how many aircraft have wiring that is getting brittle and needing repair," he says. Mason is part of a team at Northwestern that will be working on a non-destructive way of diagnosing aircraft wiring. Their work is being funded by a three-year, $450,000 grant from the Federal Aviation Administration for studying commercial aircraft wiring. Wire bundles are typically difficult to inspect because they often run through inaccessible places. Moving or dismantling the bundles can damage the wire, further complicating inspection procedures. The goal of the Northwestern team is development of a technique, called impedance/dielectric spectroscopy, that could be used to detect wiring degradation. "We are trying to use this technique for remote testing to find microscopic pinholes and cracks," says Mason. By reading the dielectric spectra, "we'd like to be able to detect the location of the defect and its nature," he says. Mason and his colleagues will study the properties of new wire, laboratory-aged wire, and naturally aged wire. For more information contact the university's Department of Materials Science and Engineering, 2145 Sheridan Rd., Evanston, IL 60208, call (847) 491-3537, or e-mails
cbrinsom@northwestern.edu or t-mason@northwestern.edu .  For more information on aging aircraft wiring, see the September 4, 2000 issue of Design News , p 76.

NSF establishes material research centers

"The products of modern materials research impact our economy and our everyday lives," says Thomas Weber, director of the Division of Materials Research at the National Science Foundation (NSF). The need for additional research on the science and engineering problems in the creation of new materials prompted the NSF to establish four new centers devoted to the study of polymer, electronic, and superconducting materials. The new centers will be located at the California Institute of Technology, the University of Oklahoma/University of Arkansas, Pennsylvania State University, and the University of Virginia. For more information, contact Ulrich Strom at ustrom@nsf.gov or visit www.nsf.gov/mps/dmr/mrsec.htm

Reducing stress in composites

Like piezoelectric ceramics, fiber-reinforced composites also suffer from hidden stresses that degrade their performance. Unlike piezoelectric ceramics, stress produces warpage arising from thermal expansion, chemical shrinkage, and non-uniform curing. It is possible to modify process variables to compensate for warpage, but it's a time-consuming, trial-and-error procedure. Phillip Geubelle at the University of Illinois (Urbana, IL) developed a modeling software program that helps shorten the time-consuming procedure. The modeling software simulates heat transfer, pressure, curing, and residual stress, and their effects on the manufacture of composite structures. "We need to understand residual stresses in order to predict the actual shape of the finished product," says Geubelle. In circuit board manufacturing, for example, laminates create residual stresses as they cure that change the shape of the circuit board. In automotive manufacturing, the glue that holds stiffeners to engine hoods deforms the shape of the hood. Geubelle and his colleagues Charles Tucker and Scott White believe that making parts from composites is different from making parts from metals. "You can bend, carve, or stamp metal into a desired shape, but with composites, you make the material as you make the part," says Tucker. Their model enables users to explore the phenomena that affect the final forms of composites, and perform the trial-and-error procedure on a computer instead of the factory floor. Simulating mechanical effects allows engineers to accurately predict the final dimensions of composites, including the tendency of parts to change shapes when removed from molds. In addition to automotive and circuit board manufacturing, Geubelle says the software has applications in aerospace industries. For more information on the software, contact Guebelle at geubelle@uiuc.edu .