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 | N O V E M B E R / D E C E M B E R 2 0 2 2 1 2 UNDERSTANDING MATERIAL FATIGUE University of Tokyo researchers used computer simulations to gain a better understanding of the physical mechanisms of low-cycle fatigue fracture in amorphous solids like glass and plastics. Understanding material fatigue in this class could help improve the reliability of materials used for industrial applications, such as machine or airplane parts, that experience many cycles of stress. What the scientists discovered challenges the widely held belief that the stress required for a fracture to occur is much smaller for cyclic stresses compared with constant stress. Instead, simulations showed that both fatigue and monotonic fractures share the same critical strain in disorder materials that corresponds with the onset of irreversible deformation. “Dynamic and elastic asymmetries with respect to density changes can lead to a link between shear deformation and density fluctuations,” explains researcher Hajime Tanaka. The next step is to confirm the team’s results through further experiments, which could help materials scientists better understand the initiation of fractures. www. u-tokyo.ac.jp/en. ROBOT DRAWS WITH CONDUCTIVE INK A collaborative research team fromWorcester Polytechnic Institute, Mass., Imperial College London, and University of Illinois Urbana-Champaign created a robotic system that literally draws its own energy to survive. To receive the maximum amount of energy from a given power source, the robot visually rearranges its surroundings by using conductive ink to draw electrical circuits. The team combined their circuit printing system with a robotic gripper, creating a robot that can perform a repertoire of actions aimed at attaining greater power— like higher voltages—from its environment and thus surviving in unfavorable conditions. The researchers tested their robot in simulations of different real-world scenarios. To prevent the robot from solely moving in a straight line, the team added obstacles to its surroundings, both in simulated and real-world trials. Some of these obstacles, such as foam cubes, could easily be removed by the robots, while others were connected to EMERGING TECHNOLOGY Scientists from the Russian Academy of Sciences and St. Petersburg University discovered a new mineral in Russia, which could become the basis for developing supercapacitor batteries. Sergeysmirnovite belongs to the hopeite group and is composed of magnesium, zinc, and phosphorus. The mineral is named in honor of Sergey Smirnov (1895-1947), a renowned specialist in mineralogy of ore deposits. www.rfbr.ru. BRIEF a grounding plate that drew the electrical power away when a circuit touched it. The team found that their robot rapidly and effectively learned to overcome these obstacles to survive and maximize the received energy. This meant rearranging obstacles or bridging areas in its surroundings that prevented it from completing the action of drawing. “I think we are taking steps toward adaptive behaviors for robots,” lead re- searcher Andre Rosendo says. www.wpi. edu, www.imperial.ac.uk, illinois.edu. Researchers simulated fractures in amorphous materials due to both cyclic fatigue and constant stress using course-grained dynamics. Courtesy of Institute of Industrial Science, The University of Tokyo. Experimental setup of the circuit drawing robot. The Jaco arm performs pick-and-place actions suggested by the network. An Arduino then receives signals noting the state of the arm and sets the on/off of the peristaltic pump to control the ink flow. The connection starts to show conductivity after the ink dries. Courtesy of Xianglong Tan, Zhikang Liu, Chen Yu, and Andre Rosendo.
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