TY  - JOUR
A1  - Mardoukhi, Ahmad
A1  - Mardoukhi, Yousof
A1  - Hokka, Mikko
A1  - Kuokkala, Veli-Tapani
T1  - Effects of test temperature and low temperature thermal cycling on the dynamic tensile strength of granitic rocks
JF  - Rock mechanics and rock engineering
N2  - 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 degrees 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 degrees C, - 50 degrees C, and - 70 degrees 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 degrees 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.
KW  - granite
KW  - dynamic loading
KW  - high strain rate
KW  - fractal dimension
KW  - low
KW  - temperature
KW  - split Hopkinson pressure bar
Y1  - 2020
U6  - https://doi.org/10.1007/s00603-020-02253-6
SN  - 0723-2632
SN  - 1434-453X
VL  - 54
IS  - 1
SP  - 443
EP  - 454
PB  - Springer
CY  - Wien
ER  - 
TY  - JOUR
A1  - Mardoukhi, Ahmad
A1  - Mardoukhi, Yousof
A1  - Hokka, Mikko
A1  - Kuokkala, Veli-Tapani
T1  - Effects of strain rate and surface cracks on the mechanical behaviour of Balmoral Red granite
JF  - Philosophical Transactions of the Royal Society of London, Series A : Mathematical, Physical and Engineering Sciences
N2  - This work presents a systematic study on the effects of strain rate and surface cracks on the mechanical properties and behaviour of Balmoral Red granite. The tensile behaviour of the rock was studied at low and high strain rates using Brazilian disc samples. Heat shocks were used to produce samples with different amounts of surface cracks. The surface crack patterns were analysed using optical microscopy, and the complexity of the patterns was quantified by calculating the fractal dimensions of the patterns. The strength of the rock clearly drops as a function of increasing fractal dimensions in the studied strain rate range. However, the dynamic strength of the rock drops significantly faster than the quasi-static strength, and, because of this, also the strain rate sensitivity of the rock decreases with increasing fractal dimensions. This can be explained by the fracture behaviour and fragmentation during the dynamic loading, which is more strongly affected by the heat shock than the fragmentation at low strain rates.
KW  - split Hopkinson pressure bar
KW  - rock
KW  - granite
KW  - dynamic loading
KW  - fractal dimension
KW  - surface cracks
Y1  - 2017
U6  - https://doi.org/10.1098/rsta.2016.0179
SN  - 1364-503X
SN  - 1471-2962
VL  - 375
IS  - 2085
PB  - Royal Society
CY  - London
ER  -