Filtreler
Comparison of drilling performance of chisel and button bits on the electro hydraulic driller

Su O. | Yarali O. | Akcin N.A.

Article | 2013 | Rock Mechanics and Rock Engineering46 ( 6 ) , pp.1577 - 1587

Electro hydraulic drillers have been widely used in mining for drilling and roof-bolting. In the drilling process, the performance of the machine is predicted by selecting an appropriate bit type prior to drilling operations. In this paper, a series of field drilling studies were conducted in order to examine and compare the performance of chisel and button bits including wear on the bits. The effects of taper angle on chisel bits, which are at angles of 105, 110 and 120, were investigated in terms of rate of penetration, instantaneous drilling rate and specific energy. The results of drilling and abrasivity tests performed in the l . . .aboratory supported the outcome of the field studies. Based on laboratory studies and field observations, it was proven that the conglomerate encountered, though it is very abrasive, is easy to drill. The cutter life in the encountered series is also longer in sandstone formation compared to the conglomerate. Additionally, button bits resulted in lower specific energy and higher penetration rates relative to chisel bits, regardless of their taper angles. The results were also supported with statistical analyses. © 2012 Springer-Verlag Wien Daha fazlası Daha az

Prediction of specific energy of rock cutting with conical bits by discrete element method [Kalem uçlu keski·lerle kayaç kesmede ayrik elemanlar yöntemi·yle spesi·fi·k enerji·ni·n kesti·ri· mi·]

Su K.

Article | 2011 | Madencilik50 ( 2 ) , pp.19 - 28

Prediction of performance and consumed energy of excavation machines has an important role on excavation processes. For this purpose, the specific energy values, which are determined by laboratory cutting tests, are utilized. Accordingly, specific energy prediction models have been being developed in computer environment by discrete elements method which is one of the numerical analysis methods. One of the most common programs used in this field is PFC 3D (Particle Flow Code in 3 Dimensions) which is able to model in three dimensions. In the scope of this study, laboratory rock cutting tests performed in the laboratories of Istanbul . . . Technical University was modeled in PFC 3D. Depending on the cutting forces acting on the pick and excavated volume of the rock, the specific energy values were calculated and compared with laboratory results. It was observed that specific energy values calculated, particularly for higher cutting depth (9mm) is close to practical values. At the end of the study, linear relationships having high correlation coefficients were determined between laboratory and modeling studies and the entire results were statistically supported with regression analysis Daha fazlası Daha az

Tool forces and specific energy prediction models in the process of sandstones cutting by using conical picks

Wang X. | Wang Q.-F. | Su O.

Article | 2018 | Scientific Mining Journal57 ( 1 ) , pp.5 - 14

In this study, unrelieved rock cutting experiments were conducted at the linear rock cutting machine and the characteristics of tool forces were discussed. The correlations among tool forces, specific energy, cutting depth, and rock strength were analyzed using single factor regression analysis method. Based on multiple non-linear regression method, the models of tool forces and specific energy were developed considering the rock strength and cutting depth. The results indicate that models of tool forces have the superior performance. When the model of specific energy is analyzed using the compressive strength of the rock, it was se . . .en that the correlations are weak compared to the model related to tensile strength of rock. In conclusion, it is emphasized that the proposed models presented in this study are particularly recommended for performance prediction of soft and medium-hard strength sandstones in case conical picks are employed. © 2018 Union of Chambers of Engineers and Architects of Turkey. All Rights Reserved Daha fazlası Daha az

Dominant Cutting Parameters Affecting the Specific Energy of Selected Sandstones when Using Conical Picks and the Development of Empirical Prediction Models

Wang X. | Wang Q.-F. | Liang Y.-P. | Su O. | Yang L.

Article | 2018 | Rock Mechanics and Rock Engineering51 ( 10 ) , pp.3111 - 3128

Specific energy is one of the most significant parameters in the process of rock cutting and it has been widely used for evaluating the performance of excavation machines. In this paper, based on rock cutting tests that were conducted on a linear cutting machine (LCM), the effects of relevant cutting parameters and characteristics, including the clearance angle, the cone (tip) angle of conical picks, the rake angle and the cutting depth on specific energy were investigated. Five different conical picks with the cone angles between 60° and 100° were used in the experiments. In addition, five different sandstones with uniaxial compres . . .sive strength varying from 17.91 to 85.98 MPa were subjected to cutting tests under different levels of cutting parameters. As a result of the tests, it was found that the clearance angle has a considerable effect on cutting force and specific energy. When it was greater than 10°, mean cutting force increased with the increasing cone angle, yet linearly decreased with the increasing rake angle and attack angle. However, specific energy has no statistical relationship with the attack angle, the rake angle, and the cone angle. It does not vary effectively with the relevant angles. Statistical analyses also indicate that strong relationships exist between the specific energy and the cutting depth in a power function. In this context, a general model of specific energy was proposed, and based on the test data and previous studies, empirical models of specific energy were developed using multiple non-linear regression and principal component regression methods. Besides, the statistical analyses showed a good agreement between the measured and predicted specific energy in unrelieved and relieved cutting modes. In conclusion, some prediction models of roadheader production rates were developed that were based on the models of specific energy. By comparing the results with the literature, it was found that the proposed models are valid in predicting the instantaneous cutting rate of roadheader especially at the cutting depth of 7–9 mm. They can be used for preliminary estimation of the production rate of roadheaders. Thus, it can be claimed that the models can offer effective solutions for the prediction of production rate of roadheaders equipped with conical picks. © 2018, Springer-Verlag GmbH Austria, part of Springer Nature Daha fazlası Daha az

Specific energy analysis of rock cutting based on fracture mechanics: A case study using a conical pick on sandstone

Wang X. | Su O.

Article | 2019 | Engineering Fracture Mechanics213 , pp.197 - 205

In order to further study rock fracture mechanism cutting by conical picks, a number of indentation experiments were undertaken. In these experiments, the chips formation and their shapes were initially observed. Then, a model of specific energy was developed and the effects of relevant cutting parameters on the specific energy were investigated based on Evans’ rock cutting mode and indentation experiments. The results showed that fracture toughness, elasticity modulus of the rock, and depth of cut have significant influence on specific energy. Applications of fracture mechanics to cutting indicated that the maximum indentation dept . . .h linearly increases with the increasing of depth of cut. There is positive power correlation between maximum cutting force and depth of cut. The total work done by the pick is approximately proportional to the square of cutting depth. The dataset of specific energy yields on a power fitting curve with the depth of cut. Theoretical analysis and experimental results revealed that there is only approximately 3% of the external work of the pick contributes to the generation of new chipping surfaces while most the external energy is dissipated in producing the crushing zone. © 2019 Elsevier Lt Daha fazlası Daha az

Effect of cutting depth and line spacing on the cuttability behavior of sandstones by conical picks

Wang X. | Su O. | Wang Q.-F. | Liang Y.-P.

Article | 2017 | Arabian Journal of Geosciences10 ( 23 ) , pp.197 - 205

Various types of conical picks in different shapes are produced and widely employed on mechanical excavators. Depending on the mechanical and abrasivity properties of rocks, appropriate shape of pick is selected. In order to obtain maximum efficiency from the pick during excavation, the interaction between the pick and rock and the cutting mechanism play very important role. In this context, linear cutting tests were conducted by using a conical pick at the cutting depths between 3 and 18 mm and also at the various line spacings on sandstones exhibiting different mechanical properties. The results indicated that cutting depth and li . . .ne spacing have significant influences on the tool forces acting on the pick, the ratio of normal to cutting force, and the specific energy. Accordingly, strong correlations and empirical models were developed. In conclusion, the empirical models proposed for estimating the forces and specific energy would be used for producing the conical bits and also designing the cutter heads of mechanical excavators on soft and medium-hard strength sandstones. © 2017, Saudi Society for Geosciences Daha fazlası Daha az

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