No abstract

The thermal expansion and the extraction characteristics of a rock are observed in a common phenomenon caused by the rock’s exposure to significant temperature differences. A thermally induced rock damage is a complex process full of uncertain physical and mechanical processes. Hence, investigating the mechanism of brittle materials is significant for both scientific and engineering applications. This study proposes a thermo-mechanical coupling model based on a continuous–discontinuous element method to simulate the thermal cracking processes in brittle rocks. In this micro-mechanical model, the rock matrix is simulated as an assembly of blocks bonded to each other. A spring model is employed to model the contacts in the blocks to simulate the mechanical deformation properties, while a thermal model is applied between their bonds to simulate heat conduction. The model validity is verified herein. Furthermore, the cracking process of brittle materials under the thermal stresses caused by the temperature gradient is studied using a thick-wall cylinder model. Consequently, the simulation results show that the microscopic crack initiation and propagation processes can be reasonably simulated at the cooling stage using the thermo-mechanical coupling model. Different geological and operation conditions are also further studied to reveal their effects on the patterns of induced fractures. This study provides a possible method for analyzing the thermal damage process and mechanism of brittle materials.

Aim of the present work focuses with influence of processing parameters on fabricated composites of LM25 alloy with SiC particles reinforcement through the squeeze casting technique. The following process parameters like stirring speed from 550 to 750 rpm, SiC weight proportions from 4 to 8% and melting temperature from 600 to 700oC were employed. Then processed composites were subjected to microstructural analysis and mechanical tests to ascertain metallurgical and mechanical properties. SEM and EDS results confirmed that the better bonding of SiC particles with matrix is achieved in the LM 25 composites and it is due to homogeneous dispersion of SiC particles in the stir casting process. The maximum tensile strength (211 MPa) and hardness (91 Hv) is achieved on the composite samples with processing parameters of 750 rpm stirring speed, 8% of SiC proportions and 650 0C of melting temperature, respectively. From the design of experiment by Taguchi method, it is found that the stirring speed plays an important role in achieving better distribution of SiC particles in the composite samples than that of other parameters like SiC weight ratios and melting temperature of the alloy.