Effects of Test Temperature and Low Temperature Thermal Cycling on the Dynamic Tensile Strength of Granitic Rocks
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ORIGINAL PAPER
Effects of Test Temperature and Low Temperature Thermal Cycling on the Dynamic Tensile Strength of Granitic Rocks Ahmad Mardoukhi1 · Yousof Mardoukhi2 · Mikko Hokka1 · Veli‑Tapani Kuokkala1 Received: 5 December 2019 / Accepted: 14 September 2020 © Springer-Verlag GmbH Austria, part of Springer Nature 2020
Abstract This paper presents an experimental procedure for the characterization of the granitic rocks on a Mars-like environment. To gain a better understanding of the drilling conditions on Mars, the dynamic tensile behavior of the two granitic rocks was studied using the Brazilian disc test and a Split Hopkinson Pressure Bar. The room temperature tests were performed on the specimens, which had gone through thermal cycling between room temperature and − 70 °C for 0, 10, 15, and 20 cycles. In addition, the high strain rate Brazilian disc tests were carried out on the samples without the thermal cyclic loading at test temperatures of − 30 °C, − 50 °C, and − 70 °C. Microscopy results show that the rocks with different microstructures respond differently to cyclic thermal loading. However, decreasing the test temperature leads to an increasing in the tensile strength of both studied rocks, and the softening of the rocks is observed for both rocks as the temperature reaches − 70 °C. This paper presents a quantitative assessment of the effects of the thermal cyclic loading and temperature on the mechanical behavior of studied rocks in the Mars-like environment. The results of this work will bring new insight into the mechanical response of rock material in extreme environments. Keywords Granite · Dynamic loading · High strain rate · Fractal dimension · Low temperature · Split Hopkinson pressure bar
1 Introduction In recent years, the exploration of Mars and Moon as alternative habitats for the humankind has attracted a great deal of attention. For instance, NASA has been rapidly increasing the number of missions for exploring Mars. During the twentieth century, the number of missions was limited to four proposals and some limited mission designs. However, since the beginning of the twenty-first century, 29 missions have been completed (including unsuccessful missions) and there are currently 12 active missions (NASA 2019). This highlights the importance of increasing our knowledge and understanding of the environmental conditions on Mars to fulfill the final goal of sending humans to this planet. The environmental conditions on Mars are considerably harsher * Ahmad Mardoukhi [email protected] 1
Engineering Materials Science, Tampere University, POB 589, 33101 Tampere, Finland
Institute of Physics and Astronomy, University of Potsdam, 14476 Golm, Germany
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compared to Earth. For example, the minimum temperature recorded on Mars − 143 °C, while the maximum temperature reaches + 35 °C with the mean temperature of about − 63 °C (Jet Propulsion Laboratory 2007). Additionally, the atmosphere of Mars is mostly composed of carbon dioxide, argon, and nitrogen, and the surface pressure is only
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