Thermal analysis and experimental testing of clamping jaws for thermomechanical simulator

This paper presents a thermal analysis of clamping jaws for a thermomechanical simulator, which is compared with the results from a thermal camera and thermocouples placed directly on the specimens during experimental testing. The clamping jaws have several cooling circuits inside of them and are actively cooled throughout the process. The test specimens are in turn heated by high-frequency electrical resistance heating. During the testing, it was observed whether the cooling system is sufficient, partly because polymeric materials are also used on the jaws to electrically insulate the system. Based on the measurements, it was found that even though the test specimen is heated almost to 1000 °C for a long time, the temperature of the jaws does not exceed 40 °C. The suitability of the proposed cooling system was proved and also the satisfactory agreement of experimental measurements with numerical simulations was achieved.

XRD Peak Profile Analysis of SiC Reinforced Al2O3 Ceramic Composite Synthesized by Electrical Resistance Heating and Microwave Sintering: A Comparison

Al2O3 with 10 wt.% of SiC ceramic composite is synthesized at 1500°C by electrical resistance heating sintering with a holding time of 5 hours and microwave sintering methods with a holding time of 15 minutes. The samples generated by the two methods are characterized using powder X-ray diffraction and field emission scanning electron microscopy (FESEM). Experiments with both samples showed that the existence of the α-Al2O3 and β-SiC phases in both samples was verified by the findings of XRD pattern on both samples. Microstructure study illustrates that the Al2O3 matrix particles have spherical-like shape and their average matrix particle size is 67 ± 5 nm for electrical resistance heating sintered sample and 38 ± 5 nm for microwave sintered sample. The lattice strain and crystallite size of Al2O3 matrix were measured using Williamson–Hall (W-H) methods, which were achieved via the use of XRD peak broadening, based on a diffraction pattern. Three modified W-H models were used to compute other parameters, including strain (ε) and stress (σ), as well as energy density (u). These models were the uniform deformation model (UDM), the uniform deformation energy density model (UDEDM), and the uniform deformation stress model (UDSM). The average crystallite sizes of α-Al2O3 attained from these three models of Williamson–Hall (W–H) methods and FESEM analysis are correlated and found very close to each other. In all three models of the W-H technique, X-ray diffraction peak profile examination of electrical resistance heating-sintered and microwave-sintered Al2O3/10 wt. % SiC ceramic composite reveals that the microwave-sintered sample has finer crystallite size with less strain.

Highlighting Specific Features to Reduce Chemical and Thermal Risks of Electronic Cigarette Use through a Technical Classification of Devices

Currently, the emission generation protocol of electronic cigarettes has only one standardized vaping regimen that is consistent with mouth-to-lungs inhalation. Recent works show the significant increase in performance of the device with the use of a direct lung vaping regimen (167 mL s−1, consistent with direct lung inhalation). However, requirements are needed for its use in a laboratory. This work aims at identifying mechanical characteristics of a device and providing a classification based on recommended power range, electrical resistance, heating surface, and air resistance of twenty-six tested devices. The electrical resistivity relation allows the estimation of the wire surface using its diameter and its length. The air resistance is obtained by measuring the pressure drop of the tested device with airflow rates ranging from 1–10 L min−1. Through the wide panel of tested devices, results allow separating them in two categories: classical and sub-ohm electronic cigarettes consistent with the two inhalation behaviours. Differences up to 71 mm2 for the wire surface and up to 4.8 Pa 0.5 min L−1 for the air resistance are observed between them. This limit seems to correspond to a required power of 25 W and an electrical resistance of 1.1 Ω.

A novel approach to hot die-less clinching process for high strength AA7075-T6 sheets

High strength AA7075-T6 aluminum sheets were joined by hot die-less clinching by locally heating the clinching region with an electrical resistance heating method. This method applied a large amount of current in the range 7.5–15 kA over a time period of 2–3 s to enhance the local ductility of AA7075-T6 sheets. A modified die-less clinching tool was developed to carry current from the blank holder to the anvil through a pair of AA7075-T6 sheets to be clinched. The above range of applied current and time duration led to an increase in sheet metal temperature in the range 175–260 ℃ leading to material softening and a consequent reduction in the clinch forming force as well as improved material flow. The clinched joints produced with constant forming force of 60 kN resulted in an increase in lap shear joint strength up to 41% with an applied current of 15 kA. Microstructure examination of the clinched region for a range of electrical resistance heating conditions revealed sound joints with previously reported forming and force locking mechanisms as well as recently identified elevated temperature material locking mechanism in the literature. The geometric interlock resulted in nonlinear increase in force with displacement in the lap shear test as well as instantaneous drop in the force due to failure of material locking.