Browsing by Author "Darnis, Philippe"
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Item Experimental characterization of the AA7075 aluminum alloy using hot shear compression test(2021-05) Bhujangrao, Trunal; Veiga, Fernando; Froustey, Catherine; Guérard, Sandra; Iriondo, Edurne; Darnis, Philippe; Mata, Franck Girot; Tecnalia Research & InnovationThe experimental characterization of the material under shear loading is essential for researchers to study the plastic behavior of materials during manufacturing processes. Indeed, regardless of the loading mode, ductile materials mainly deform plastically under shear loading. Thus, for such material behavior analysis, shear tests are very useful. In this paper, a test procedure is defined to characterize the shear deformation of AA7075 aluminum alloy at high strain under compression loading. The Finite Element (FE) simulation is used to select the suitable specimen geometry for the testing. Finally, the experimental tests are carried out using a conventional compression device at a constant strain rate of 0.1 s−1 and at an elevated temperature of 20–500 °C. The results show that the drop in the flow stress curved relative to the increase in temperature exhibits the softening mechanism. The homogeneous behavior of the shear strain along the shear region was also observed and shown by the macro and micro images. The effect of temperature and equivalent strain on the evolution of the microstructure is discussed in detail. It is discovered that, various dynamic recrystallization mechanisms were recorded for aluminum alloy AA7075 depending on the imposed strain conditions.Item Review of intermediate strain rate testing devices(2020-07) Bhujangrao, Trunal; Froustey, Catherine; Iriondo, Edurne; Veiga, Fernando; Darnis, Philippe; Mata, Franck Girot; Tecnalia Research & InnovationMaterials undergo various loading conditions during different manufacturing processes, including varying strain rates and temperatures. Research has shown that the deformation of metals and alloys during manufacturing processes such as metal forming, machining, and friction stir welding (FSW), can reach a strain rate ranging from 10−1 to 106 s−1 . Hence, studying the flow behavior of materials at different strain rates is important to understanding the material response during manufacturing processes. Experimental data for a low strain rate of <101 s−1 and a high strain rate of >103 s−1 are readily available by using traditional testing devices such as a servo-hydraulic testing machine and the split Hopkinson pressure bar method, respectively. However, for the intermediate strain rate (101 to 103 s−1 ), very few testing devices are available. Testing the intermediate strain rate requires a demanding test regime, in which researchers have expanded the use of special instruments. This review paper describes the development and evolution of the existing intermediate strain rate testing devices. They are divided based on the loading mechanism; it includes the high-speed servo-hydraulic testing machines, hybrid testing apparatus, the drop tower, and the flywheel machine. A general description of the testing device is systematically reviewed; which includes the working principles, some critical theories, technological innovation in load measurement techniques, components of the device, basic technical assumption, and measuring techniques. In addition, some research direction on future implementation and development of an intermediate strain rate apparatus is also discussed in detail.