Faculty Publications
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Item Effect of High Temperature on the Compressional Wave Velocity of Two Sandstones with Different Grain Sizes(Springer Science and Business Media Deutschland GmbH, 2024) Manikanta, V.; Hasainar, H.; Badiger, N.K.; Kothari, V.; Bhat, A.; Srinivasan, V.Understanding rock behaviour at high temperatures can serve as vital information in restoring fire-damaged monumental structures. This knowledge is essential for engineering and construction purposes, as it allows for assessing rock stability and potential hazards and developing appropriate safety measures in areas with high temperatures. This study investigates the effect of different temperatures on two sandstones with varying grain sizes. The rock was first heated to a range of temperatures such as 35, 250, 500, 750, and 1000 °C. To identify the thermal damage of the rock samples, the Ultrasonic Pulse Velocity measurement instrument is used to identify the inner cracks. This research discusses the application of Ultrasonic Pulse velocity (UPV) to identify thermal damage and analyse related parameters of two different sandstones. The ultrasonic method is one of the simple and reliable techniques to understand the damage conditions of rocks. There were significant variations in the P-wave velocity with thermal treatment, it is observed that a negative trend developed in the primary wave velocity as the temperature increased. They give qualitative and quantitative inferences on the extent of damage caused by various environmental parameters, particularly heating. The data obtained from the present study were compared to check the confidence of regression models. The mean absolute percentage error method, the root mean square error method (RMSE), was carried out on thermal damage of rock samples. Probabilistic analysis was also conducted to estimate the damage on rocks at different confidence levels. © The Author(s), under exclusive license to Springer Nature Singapore Pte Ltd. 2024.Item Experimental investigation and statistical analysis of operational parameters on temperature rise in rock drilling(International Information and Engineering Technology Association info@iieta.org, 2018) Vijay Kumar, V.K.; Kunar, B.M.; Murthy, C.S.Heat generated during rock drilling, due to friction at the bit-rock interface. Due to which temperature increases, which can influence the thermal stress and subsequent rock failure. In this paper, an attempt is made to present results related to the temperature assessment during rotary drilling of rocks on medium-grained sandstone under controlled laboratory conditions. The experiments were conducted by using embedded thermocouple technique, the thermocouple was placed at a distance of 0.5mm (horizontal) from the bit-rock interface. The influence of operational parameters, i.e., the diameter of the drill bit, spindle speed and rate of penetration of rise in temperature was studied using multiple regression and data analysis was carried out using analysis of variance (ANOVA). The temperature was measured by using embedded thermocouple technique at a depth of 6mm, 14mm, 22mm and 30mm respectively. Regression models were developed for the prediction of temperature at the bit-rock interface. It was observed that the increase in temperature for medium-grained sandstone was from 49 0 C to 74 0 C (51.08%) with an increase in the diameter of the drill bit, spindle speed and rate of penetration. © 2018 International Information and Engineering Technology Association.Item Measurement of bit-rock interface temperature and wear rate of the tungsten carbide drill bit during rotary drilling(Tsinghua University Press wyl-dhh@tsinghua.edu.cn, 2020) Vijay Kumar, V.K.; Kunar, B.M.; Murthy, C.S.; Ramesh, M.R.Rock drilling is an essential operation in mining industries. Temperature at the bit-rock interface plays a major role in the wear rate of the drill bit. This paper primarily focuses on the wear rate of tungsten carbide (WC) drill bit and the interrelationship between temperature and wear rate during rotary drilling operations conducted using a computer numerical control (CNC) machine. The interrelationship between the temperature and wear rate was studied with regard to three types of rock samples, i.e., fine-grained sandstone (FG) of uniaxial compressive strength (UCS) that is 17.83 MPa, medium-grained sandstone (MG) of UCS that is 13.70 MPa, and fine-grained sandstone pink (FGP) of UCS that is 51.67 MPa. Wear rate of the drill bit has been measured using controlled parameters, i.e., drill bit diameter (6, 8, 10, 12, and 16 mm), spindle speed (250, 300, 350, 400, and 450 rpm), and penetration rate (2, 4, 6, 8, and 10 mm/min), respectively. Further, a fully instrumented laboratory drilling set-up was utilized. The weight of each bit was measured after the bit reached 30 mm depth in each type of the rock sample. Furthermore, effects of the bit-rock interface temperature and operational parameters on wear rate of the drill bits were examined. The results show that the wear rate of drill bits increased with an increase in temperature for all the bit-rock combinations considered. This is due to the silica content of the rock sample, which leads to an increase in the frictional heat between the bit-rock interfaces. However, in case of medium-grained sandstone, the weight percentage (wt%) of SiO2 is around 7.23 wt%, which presents a very low wear rate coefficient of 6.33×10?2 mg/(N·m). Moreover, the temperature rise during drilling is also minimum, i.e., around 74 °C, in comparison to that of fine-grained sandstone and fine-grained sandstone pink. In addition, this paper develops the relationship between temperature and wear rate characteristics by employing simple linear regression analysis. © 2019, The Author(s).Item Prediction of transient temperature at bit-rock interface using numerical modelling approach and optimization(Springer-Verlag Italia s.r.l., 2024) Vijay Kumar, V.K.; Avinash, A.; Pon Selvan, C.P.; Girish, B.M.; Kunar, B.M.; Flores Cuautle, J.; Ramakrishna, V.K.; Vinayak, V.One of the major factors impacting on drill bit performance during rock drilling is interface temperature. The performance of the drill bit during drilling operations not only depends on operations parameters but also the properties of rock during drilling in laboratory and field investigations. Hence the present study focused on interface of bit-rock, the temperature had been determined by developing a specially grounded thermocouple. Over 500 different test conditions were performed in each rock sample's case during experimental drilling on a cylindrical block of UCS of 17.83 MPa (fine-grained sandstone grey-FG), 13.70 MPa (medium-grained sandstone-MG), and 51.67 MPa (fine-grained sandstone pink-FGP). The results revealed that the average increase in interface temperature for MG is about 53.74%, FG is about 93.26%, and FGP is about 165.22%. The significant parameters such as uniaxial compressive strength (26%), depth (33%), rate of penetration (15.2%), diameter of the bit (5.26%), and thrust (5.04%) are the most influenced parameters on temperature, followed by spindle speed (1.04%), and torque (0.23%) respectively. The proposed regression models successfully predict the temperature with an R2 value of 91.74%, 90.30%, and 90.95% for MG, FG, and FGP, respectively. Finally overall regression model is developed by considered operational parameters with rock properties to predict temperature and R2 value of 80.8% for all three types of rock samples considered. © The Author(s), under exclusive licence to Springer-Verlag France SAS, part of Springer Nature 2023.