Embedded Resistance Wire Technique for Epoxy Curing and Self-Healing of PET Thermoplastics

The aim of the present study is to apply an embedded resistance wire technique for curing of thermosetting resins as well as for the self-healing of thermoplastic polymers. The work consists of two parts. In the first part, Kanthal resistance wires embedded in a resin plate acted as heating elements when direct electrical current was flowing through them (Joule heating). During heating, the temperature was continuously monitored using a thermal camera, and accurate temperature times for fixed position diagrams as well as temperature positions for fixed time diagrams were calculated. The effects of curing with this method were evaluated by studying the three-point bending mechanical behavior of the cured resin, comparing it with the corresponding behavior of the same resin when cured using a conventional oven curing method at the same temperature. In the second part of the present work, the possibility of using the same technique for healing existing notches and flaws in a PET thermoplastic is explored. We examined whether providing energy through the resistance wires created the right amount of heat to heal the thermoplastic, or, more specifically, whether it closed the notches and eliminated the abrasions that were artificially created on the specimens. The technique using embedded resistance wires worked equally well, with interesting and promising preliminary results regarding the curing of thermoset resins and the healing of thermoplastics.

Evolution of the Microstructure of a CuCr1Zr Alloy during Direct Heating by Electric Current

Round tensile test specimens of an age-hardened CuCr1Zr alloy were subjected to direct electrical current heating in a Gleeble thermal–mechanical simulator at 800 °C. The mechanical properties were monitored by the Vickers hardness test, and the changes in the grain structure were examined by light metallography. A quantitative analysis of the size and distribution of fine precipitates during annealing was carried out using transmission electron microscopy (TEM). The grain structure showed a gradient corresponding to the gradient of the temperature on the test piece. Annealing for 60 s at 800 °C resulted in a partially (~50%) recrystallized structure with new grains about 45 μm in diameter. In the as-delivered condition, TEM documented tiny (1 to 4 nm) coherent chromium precipitates inducing strain fields in the matrix. During overaging, the particles lost their coherence and gradually coarsened up to a mean diameter of 40 nm after 300 s at 800 °C. The coarsening kinetics obeys Lifshitz, Sloyzov, and Wagner’s theory.

Influence of plastic deformation on electrochemical properties of X5CrNi18-10 steel

The purpose of the work was to determine the effect of plastic deformation on the electrochemical properties of X5CrNi18-10 steel. The tested material belongs to the group of stainless steels with low carbon content and is used in many industries due to high corrosion resistance. In most applications of the tested material, it is formed into complicated shapes and exposed to aggressive environments. An example can be applications in medicine (implants) as well as in civil engineering and nuclear energy The literature on the subject shows a different impact of deformation on anti-corrosion properties. Samples with 5 different deformations were obtained. Electrochemical direct electrical current and alternating electrical current tests were performed for the obtained materials. The tests were carried out in a 1 molar sodium chloride solution. Studies have shown an increase in corrosion resistance of samples with increasing strain in the tested strain ranges.

An Extensive Review of Multilevel Inverters Based on Their Multifaceted Structural Configuration, Triggering Methods and Applications

Power electronic converters are used to transform one form of energy to another. They are classified into four types depending upon the nature of the input and output voltages. The inverter is one among those types; it converts direct electrical current into alternating electrical current at desired frequency. Conventional types of inverters are capable of producing voltage at the output terminal that can only switch between two levels. The range of output voltage generated at the output is low when they are used for high power applications. To improve the voltage profile and efficiency of the overall system, multilevel inverters (MLIs) are introduced. In multilevel inverters the voltage at the output terminal is generated from several DC voltage levels fed at its input. The generated output is more appropriate to a sine wave and the dv/dt rating is also less leading to the reduction in EMI. Though they possess many advantages compared to the conventional inverters, the structural complexity and triggering techniques involved in designing multilevel inverters are high. Many studies are being carried out in defining new topologies of MLI with reduced switch as well as with the implementation of different PWM techniques. This paper will provide an extensive review on variety of MLI configurations based on the parameters such as the number of switches, switching techniques, symmetric, asymmetric, hybrid topologies, configurations based on applications, THD and power quality.

ZAP! Nikola Tesla Takes Charge by M. Kulling

Kulling, Monica. ZAP! Nikola Tesla Takes Charge. Illustrated by Bill Slavin. Tundra Books, 2016.In this, her ninth contribution to Tundra Books’ Great Ideas Series, prolific children’s author Monica Kulling distills and simplifies the life and inventions of immigrant engineer and scientist Nikola Tesla (1856–1943) for primary school readers. Confining her story to the first half of Tesla’s long life, from his humble origins in Slovenia (then a part of the Austro-Hungarian Empire), to his achievements as nineteenth-century America’s foremost electrical engineering genius, Kulling has maintained a manageable length compatible with the attention span of her audience.The rivalry between Tesla and his one-time patron and employer, Thomas Edison, over the suitability of alternating versus direct electrical current (AC vs. DC) is described without exposing all the sordid details of their rivalry. The story then quickly moves on to Tesla’s partnership with George Westinghouse to illuminate the 1892-93 Chicago world’s fair site, and to build the first hydroelectric power plant at Niagara Falls, employing alternating current, a system that allowed electricity to be transmitting over greater distances more cheaply and efficiently than Edison’s rival system. Kulling ends her story in 1898, when Tesla demonstrated a model boat controlled by radio waves, an invisible force that he suggested might also be used for wireless communication, a concept soon made real by radio pioneer Guglielmo Marconi.Apart from an anachronistic use of the word “robot,” Kulling’s text is historically and scientifically accurate, clearly written, and age-appropriate, without being condescending. Bill Slavin’s illustrations are nicely evocative of the late nineteenth-century buildings and workshops, and are scaled large enough for story-hour readings to groups of children.Reviewer: Merrill DistadHighly recommended: 4 out of 4 starsMerrill Distad is Associate University Librarian (Research and Special Collections Services) and University Archivist, University of Alberta, and is the co-editor of Peel’s Bibliography of the Canadian Prairies to 1953 (Toronto, 2003). He is the author, most recently, of The University of Alberta Library: The First Hundred Years, 1908–2008 (Edmonton, 2009).