Purpose The paper aims to investigate the problem of heat distribution in FDM 3D printing. The temperature distribution of the material is important because of the occurrence of shrinkage and crystallization phenomena that affect the dimensional accuracy and strength of the material. Design/methodology/approach The study uses a thermoplastic material (polylactide) and a test stand equipped with a 3D printer adapted to perform thermographic observations. The main source of heat in the study was a molten laminate material and a hot-end head. Findings When the material is molten at the temperature of 190°C, the temperature of a previous layer increases above the glass transition point (Tg = 64.8°C) and reaches to about 80°C. In addition, at the boundary of the layers, there occurs a permanent bonding of the consecutive layers because of their partial melting. The paper also reports the results of porosity of PLA samples printed at the temperature ranging between 205 and 255°C. The degree of porosity depends on the temperature of the extruded material. Practical implications The results may be helpful for designers of various printed parts and construction engineers of printing heads and 3D printer chambers. Originality/value Thermograms of material layers with a height of 0.3 mm are obtained using a thermal imaging camera with a lens for macro magnification (43 pixels/mm).
Helicopters play an important role in air-to-ground fire covering and the short-distance air-to-air fights, as well as the anti-tank missions and battlefield force transferring. The detection and survivability of helicopters on a battlefield significantly depends on their infrared emissions level, as well as the methods, equipment and systems used by potential enemy. The automatic detection systems, recognition and identification of flying objects use among other the thermo-detection methods, which rely on detecting the infrared radiation emitted by the tracked object. Furthermore, due to low-altitude and relatively low flight speed, today’s combat assets like missile weapons equipped with infrared guidance systems are one of the most important threats to the helicopters performing combat missions. Especially meaningful in a helicopter aviation is infrared emission by exhaust gases, egressed to the surroundings. Due to high temperature, exhaust gases are a major factor in detectability of a helicopter performing air combat operations. In order to increase the combat effectiveness and survivability of military helicopters, several different types of the infrared suppressor (IRS) have been developed. This paper reviews contemporary developments in this discipline, with particular examples of the infrared signature suppression systems.
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