September_AMP_Digital

A D V A N C E D M A T E R I A L S & P R O C E S S E S | S E P T E M B E R 2 0 1 9 1 3 reveal subtle structural changes indi- cating catastrophic damage in bridges. In August 2018, the Morandi Bridge near Genoa, Italy, collapsed and killed dozens of people. Scientists fromNASA, the University of Bath, U.K., and the Italian Space Agency used synthetic aperture radar (SAR) measurements from several different satellites and reference points to map relative dis- placement from 2003 to the time of its collapse. Using a new process, they were able to detect millimeter-size changes to the bridge over time that would not have been detected by the standard processing approaches applied to spaceborne synthetic aper- ture radar observations. “We can’t solve the entire problem of structural safety, but we can add a new tool to the standard procedures to better support maintenance consider- ations,” says Pietro Milillo, lead scien- tist. nasa.gov. HIGH-SPEED X-RAYS CAPTURE MICROSCOPIC FLAWS Scientists have recently achieved a new understanding of laser spattering, leading to new insights about micro- scopic defects that occur in laser-based production of metal parts. A research team from Argonne National Labora- tory, Lemont, Ill., created high-speed x-ray “movies” to analyze the phenom- enon, and the work could lead to rem- edies for this serious manufacturing challenge. Laser spattering refers to the ejection of molten metal from a pool heated by a high-power laser dur- ing laser-based manufacturing pro- cesses, such as laser welding and laser- additive manufacturing. These laser manufacturing technologies are used to fabricate parts for use in a variety of industries, including aerospace, the automotive industry, healthcare, and construction. “The newly discovered mecha- nism will guide the development of approaches to mitigate defect forma- tion in welds and additively manufac- tured parts,” says researcher Lianyi Chen. The research group created the images through the use of a high- energy synchrotron x-ray at Argonne National Lab along with image analysis and numerical simulations. “The high penetration power of hard x-rays and high resolutions of the imaging technique enable us, for the first time ever, to connect the spatter- ing behavior above the surface with dynamics below the surface and inside the titanium sample,” the researchers say . anl.gov. This collection of MHz x-ray images of metal spattering of Ti-6Al-4V reveals various events that occurred during laser process- ing. Courtesy of Argonne National Lab.