Izzet Karakurt

An Experimental Study on the Depth of Cut of Granite in Abrasive Waterjet Cutting

Many studies investigating the cutting performances of waterjets for several kinds of materials such as steel, brass, glass, or aluminium are available. However, there are few studies focused on the rock cutting in the literature. In the present study, therefore, it is aimed at investigating the cuttability of granite by abrasive waterjet. The effect of process parameters and the textural properties of granites on the cut depth and surface quality were investigated. The design philosophy of Taguchi was followed to conduct the experiments. Analysis of variance (ANOVA) was used to evaluate the data obtained statistically. Major significant process factors affecting the cut depth of granite were determined. It was disclosed that the traverse speed was the most significant process parameters affecting the cut depth of granite. Additionally, it was found that the depth of cut and surface quality were strongly affected by the grain size and its boundaries with the grains surrounding. Furthermore, consistent relations between some physical and mechanical properties of the granite (e.g., the water absorption, microhardness, the specific bulk density, and the uniaxial compressive strength) and the depth of cut were observed.

Prediction of the Cut Depth of Granitic Rocks Machined by Abrasive Waterjet (AWJ)

In this paper, an experimental study on the cut depth, which is an important cutting performance indicator in the abrasive waterjet (AWJ) cutting of rock, was presented. Taguchi experimental design of an orthogonal array was employed to conduct the experiments. A variety of nine types of granitic rocks were used in the cutting experiments. The experimental data were used to assess the influence of AWJ operating variables on the cut depth. Using regression analysis, models for prediction of the cut depth from the operating variables and rock properties in AWJ machining of granitic rocks were then developed and verified. The results indicated that the cut depths decreased with increasing traverse speed and decreasing abrasive size. On the other hand, increase of the abrasive mass flow rate and water pressure led to increases in the cut depths. Additionally, it was observed that the standoff distance had no discernible effects on the cut depths. Furthermore, from the statistical analysis, it was found that the predictive models developed for the rock types had potential for practical applications. Verification of the models for using them as a practical guideline revealed a high applicability of the models within the experimental range used.

Forecasting the Energy-related CO2 Emissions of Turkey Using a Grey Prediction Model

As one of the most important anthropogenic greenhouse gases, carbon dioxide (CO2) emissions have drawn great academic and scientific attention over the last decades. With the economic development and fossil energy consumption growth in especially developing countries, such as Turkey, efforts controlling the CO2 emissions are required for both planning the countries’ energy policy and maintaining the international agreement on climate change mitigation. Therefore, forecasting the CO2 emissions is a key factor in adjusting related policies. This article aims at presenting a grey prediction model to forecast the energy-related CO2 emissions in Turkey. Energy-related CO2 emissions for the period of 1965–2012 were considered as the case of this study. Then, emissions in Turkey were forecasted in the upcoming years, up to year 2025. Additionally, the forecasting accuracy was examined by calculating three different evaluation statistics. The results indicated that future energy-related CO2 emissions of Turkey can be successfully forecasted by application of the grey prediction model, and this technique can be used as a potential forecasting tool for CO2 emission.

An investigation on the kerf width in abrasive waterjet cutting of granitic rocks

This paper presents an experimental and statistical study on the kerf width, used instead of the width of the cut in abrasive waterjet (AWJ) cutting. Pre-dimensioned granitic rocks were sampled for the experimentations designed by using Taguchi orthogonal arrays. The effects of the AWJ operating variables on the kerf width were studied and the rock properties were correlated with the kerf widths. Additionally, predictive models for the kerf widths were developed using multi-variable regression analysis and the developed models were verified through some statistical tests. The results demonstrated that the standoff distance and the traverse speed have significant effects on the kerf widths. The results also showed that water absorption, unit weight, microhardness, the maximum grain size of rock-forming minerals, and mean grain size of the rock have significant correlations with the kerf widths of the tested rocks. Furthermore, the modeling results revealed that the predictive models derived from rock properties, can be successfully used as a practical guideline.

Wear Performance of Saw Blades in Processing of Granitic Rocks and Development of Models for Wear Estimation

This study investigates the wear performance of diamond circular saw blades in cutting of granitic rocks. An alternative wear measuring method is developed to measure the reduced blade radius without taking the blade off the machine. The effect on and contribution to the specific wear rate (SWR) of each operating variable are determined, and the SWR is correlated with rock properties. Morphologies of wearing surfaces of segments and rocks are also evaluated using scanning electron microscopy (SEM). Depending on both operating variables and rock properties, prediction models are developed for estimation of the SWR. Results show that the SWR increases with an increase in the peripheral speed and the traverse speed, while it decreases with an increase in the cutting depth and the flow rate of the cooling fluid. The peripheral speed, and the microhardness and proportions of minerals such as quartz, plagioclase, and feldspar are statistically determined as the significant variables affecting the SWR. Finally, it is disclosed that models developed for estimation of SWR have great potential for practical applications.

Experimental and statistical analysis of cutting force acting on diamond sawblade in sawing of granitic rocks

In this study, sawability analyses of granitic rocks were carried out using segmented circular diamond sawblades. In the experimentations, a computer controlled cutting machine was used and the experiments were performed with the same-direction cutting mode. Effects and contribution of each operating variable (the peripheral speed, workpiece traverse speed, cutting depth and flowrate of cooling fluid) on the cutting force were determined and cutting forces were correlated with rock properties. Moreover, models were built depending on the operating variables and the rock properties (physico-mechanical and mineralogical properties) for the estimation of cutting force. The results indicated that the higher cutting forces were obtained for higher cutting depth and traverse speed and for lower peripheral speed and flowrate of cooling fluid. The most significant operating variable affecting the cutting force was determined as cutting depth. It was concluded that rather than the physico-mechanical properties, mineralogical properties (such as quarts, plagioclase and feldspar content) is the dominant rock properties affecting the cutting force. Results also revealed that the predictive models derived from operating variables and materials properties have high potentials for practical applications.

Development of Predictive Models for the Specific Energy of Circular Diamond Sawblades in the Sawing of Granitic Rocks

This paper presents an experimental study on the sawing of granitic rocks by circular diamond sawblades. The influence of the operating variables and rock properties on the specific energy were initially investigated and analyzed. To determine the most significant operating variables and rock properties influencing the specific energy, statistical analyses were then employed and the models were built for the estimation of specific energy depending on the operating variables and the rock properties. Moreover, the derived models were validated through statistical tests such as the determination coefficient, t-test, F-test, and residuals. The results indicated that the specific energy decreased with the decreasing of peripheral speed and the increasing of traverse speed, cutting depth, and flow rate of cooling fluid, respectively. It was concluded that, rather than the physico-mechanical properties, the mineralogical properties were the dominant rock properties affecting the specific energy. Additionally, the peripheral speed was statistically determined as the most significant operating variable affecting the specific energy. The peripheral speed was followed by the cutting depth, traverse speed, and flow rate of cooling fluid with respect to their level of significance on the specific energy. Furthermore, the model results revealed that the developed models have high potentials as a guidance for practical applications.

A study on the prediction of kerf angle in abrasive waterjet machining of rocks

In this study, the effects of the abrasive waterjet operating variables on the kerf angle were studied and the material properties were correlated with the kerf angle. The Taguchi method was followed to conduct the experimentation and the regression modeling was used in order to build models for prediction of dependent (kerf angle) from independent (operating and material properties) variables. Additionally, the adequacy of the model was tested using several statistical tests. The results indicated that not only operating variables themselves, but also the textural and mineralogical properties had discernible effects on the kerf angles. It was found from the correlation analysis that the water absorption, max grain size of rock-forming minerals and mean grain size of the rock had significant influences on the kerf angles of the rocks tested. Furthermore, it was determined that the kerf angles can be predicted by the developed models related to the rock types.

Analysis and Mitigation Opportunities of Methane Emissions from the Energy Sector

Abstract Methane concentration in the atmosphere has critically increased recently. Increasing environmental concern and global warming have made it become an imminent consideration. The energy sector is the second largest contributor to methane emissions. In this study, major sources of methane emissions in energy production processes are determined. The countries that are responsible for the majority of emissions in every source are defined and the methane release performances of these countries are evaluated. Finally, methane mitigation options from natural gas and oil systems and coal mining, accounting for the majority of emissions from the energy sector, are presented.

Diamond recovery from waste sawblades: A preliminary investigation

Due to their excellent hardness and toughness, diamond tools have been widely used as cutting tools for mining applications such as machining and/or processing of natural stones. A considerable amount of used sawblades with diamond grits are damaged, scrapped and wasted in the regions where machining and/or processing of ornamental stones are heavily conducted. Since a damaged and/or scrapped sawblade could still have diamonds grits, the recovery of diamond grits from sawblades has recently gained attention. The aim of this study was to investigate the recoverability of diamonds from damaged sawblades using hydrometallurgical processes, including aqua regia. Using scanning electron microscopy micrographs, the worn surfaces of diamonds were also examined before and after leaching. The results of the study represented that the diamonds from damaged sawblades can be successfully recovered by hydrometallurgical processes, including aqua regia, and the recovered diamonds could be reused in cutting tools after size classification. The results also revealed that among the damage types of diamond, the fractured and polished crystals resulted in diamond crystals with lower grain size.