Yazar "Sarici, Didem Eren" seçeneğine göre listele

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    Determining point load strength loss from porosity, Schmidt hardness, and weight of some sedimentary rocks under freeze-thaw conditions
    (Springer, 2018) Sarici, Didem Eren; Ozdemir, Engin
    Rocks are subjected to various atmospheric, climatic, and seasonal effects, and those effects can cause partial or complete deterioration. To understand the degree of deterioration of rocks, especially in cold regions, the influences of freeze-thaw cycles on physico-mechanical properties need to be investigated. This study assesses the influence of freeze-thaw cycles on some physical and mechanical properties of some rocks of sedimentary origin in Turkey. For this purpose, samples were subjected to 30 freeze-thaw cycles, and porosity, point load strength, Schmidt hardness, and weight loss were determined after every five cycles. The freeze-thaw cycle progression led to decreases in point load strength, Schmidt hardness, and weight and an increase in porosity of the specimens. The increase and decrease ratios were calculated at the end of every five freeze-thaw cycles, and the relationships were determined for estimated point load decrease ratios. At the end of 20 cycles, there was a strong relationship between point load strength loss and Schmidt hardness loss (R-2 = 0.903), which can be very useful for predetermination of point load strength decrease after freeze-thaw cycles without testing.
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    The effects of some environmental conditions on the mode I fracture toughness of rocks
    (Springer, 2024) Ozdemir, Engin; Sarici, Didem Eren
    Fracture toughness is an important parameter in determining the fracture mechanism of rocks, concretes and other composites, and it is used in performing design and stability analyses. In this study, the aim was to determine the effects of different environmental conditions (dry, saturated, freezing, thermal shock and thermal aging) on fracture toughness and fracture energy values of rocks from three different origins: gabbro, recrystallized limestone and limestone. In the first stage, the physical, chemical, mechanical, mineralogical and petrographic properties of rocks were determined. The material properties of rocks were revealed by physico-mechanical tests, XRD, XRF and petrographic analysis. In the second stage, the rocks were aged by exposing them to pre-determined environmental conditions for a certain period of time and then, semi-circular bending strength tests were applied to the aged rocks. SEM images were taken to determine the effects of different environmental conditions on surface cracks. According to the experimental results, thermal shock, thermal ageing and water saturation conditions led to decreasing fracture toughness, while freezing conditions led to increasing fracture toughness. It was determined that thermal shock was the environmental condition that caused the most weakening. In freezing conditions, it was observed that physico-mechanical properties and fracture toughness values of rocks increased. It was seen that the fracture toughness values of the monomineralic structured samples were more affected by the environmental conditions than the multimineralic rocks.
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    Effects of thermal shock and aging on natural stones: an experimental and statistical study
    (Springer, 2023) Ozdemir, Engin; Sarici, Didem Eren
    Natural stones are exposed to sudden and slow-developing thermal cycles, affecting their physico-mechanical and surface properties. In this study, changes in the physico-mechanical properties of natural stones in response to sudden (thermal shock) and slow-developing (thermal aging) thermal cycles were investigated on natural stone samples with various compositions (magmatic, sedimentary, metamorphic). Both the thermal shock and thermal aging cycles were simulated by first heating the specimens to 105 degrees C for 18 h. In case of the thermal shock cycles, the heating phase was followed by placing the samples in purred water for 6 h. To simulate the thermal aging cycles, specimens were allowed to cool at room temperature (23 degrees C) for 6 h. At the end of the cycles, a selection of physico-mechanical properties was evaluated and compared with the initial values. Results indicate that thermal treatments have a significant negative effect on the strength of the natural stone samples. Regression models were developed to estimate uniaxial compressive strength, point load strength, Brazilian tensile strength from non-destructive test parameters (Schmidt hardness, P wave velocity, porosity) of natural and treated samples. Results show that there are strong correlations between mechanical properties and non-destructive test parameters (R-2 > 0.96, MAPE values between 2 and 5%).
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    Modeling uniaxial compressive strength of some rocks from turkey using soft computing techniques
    (Elsevier Sci Ltd, 2021) Gul, Enes; Ozdemir, Engin; Sarici, Didem Eren
    Uniaxial compressive strength (UCS) is substantially used mechanical parameters to observe and classification of rocks, but this test is subsersive, taking a long time and required well equipped laboratory conditions and properly prepared samples. Therefore it is important to estimate this parameter from other physico-mechanical rock parameters that are nondestructive, easy to prepare samples and required less time. Machine learning methods which are among these methods and increase their importance and validty are Multilayer Perceptron Neural Network (MLPNN), M5 Model Tree (M5MT), Extreme Learning Machine (ELM) methods. In this study, Brazilian tensile strength, ultrasonic P-wave velocity, shore hardness tests of different rock types (Basalt, limestone, dolostone) were performed. The results were used for estimating UCS using MLPNN, M5MT, ELM methods. The validation of models were checked root mean squared error (RMSE), mean absolute error (MAE), variance account for (VAF) and coefficient of determination (R-2) and a10-index. Weights and bias values for MLPNN and ELM approaches and the tree structure for the M5MT method are presented. The result indicated MLPNN model outperforms the other models. Based on the result of predictive models with RMSE, MAE, VAF and R-2 equal to RMSE: 1.3421, MAE: 0.7985, VAF: 99.7409, R-2: 0.9982%.
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    Thermal deterioration of marbles: Gloss, color changes
    (Elsevier Sci Ltd, 2016) Sarici, Didem Eren
    Marbles are widely used as construction materials because of their high resistivity to common conditions, and to their aesthetic appeal. Aesthetic qualities such as color, gloss and polishability are important for rock used as constructions materials. But marbles as building stones show complex weathering phenomena. Thermal effects are important weathering factors affecting the aesthetical and physico-mechanical properties of marbles. This study assesses changes to surface aesthetic properties of some marble samples due to heat. For this purpose thermal ageing and thermal shock cycles were inflicted on six types of marble samples of differing colors. Marble samples of shiny surfaces were prepared. In thermal shock cycles, samples were heated up to 105 degrees C for 18 h then placed for 6 h in distilled water. In thermal ageing cycles, the samples were placed in an oven for 18 h then allowed to cool for 6 h at room temperature. At the end of cycles 4, 8, 12, 16 and 20, gloss measurements were recorded; at the end of the last cycles color changes were evaluated. The relationships between gloss and color parameters were also investigated. Thermal shock has more important effects on marble surface properties than the thermal ageing cycle. L* and b* parameters constituted an important effect on glossiness and these parameters were strong indicators for predicting gloss loss. (C) 2015 Elsevier Ltd. All rights reserved.
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    Use of uncertain numbers for appraising tensile strength of concrete
    (Techno-Press, 2013) Tutmez, Bulent; Cengiz, A. Kemal; Sarici, Didem Eren
    Splitting tensile strength (STS) is a respectable mechanical property reflecting ability of the concrete. The STS of concrete is mainly related to compressive strength (CS), water/binder (W/B) ratio and concrete age. In this study, the assessment of STS is made by a novel uncertainty-oriented method which uses least square optimization and then predicts STS of concrete by uncertain (fuzzy) numbers. The approximation method addresses a novel integration of fuzzy set theory and multivariate statistics. The numerical examples showed that the method is applicable with relatively limited data. In addition, the prediction of uncertainty at various levels of possibility can be described. In conclusion, the uncertainty-oriented interval analysis can be suggested an effective tool for appraising the uncertainties in concrete technology.
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    Utilization of granite waste as alternative abrasive material in marble grinding processes
    (Elsevier Sci Ltd, 2018) Sarici, Didem Eren; Ozdemir, Engin
    Wastes formed during the production and processing of marble and granite cause problems for the leading countries in natural stone production because they result in environmental pollution, negative conditions for health and cause economic losses. Decreasing the formation of waste materials and studies on their reusability are important to provide environmental and economic benefits. The main purpose of this study is to determine the reusability of the waste material formed during granite production as conventional artificial abrasive in the marble abrasion process. Accordingly, three different marble samples commercially available in different areas of Turkey were studied. Bohme abrasion test was carried out with Al2O3 and granite waste, which are used as common abrasives in marble abrasion operations. The waste of granite was classified in three different grain sizes after processing it with solid-cutting, crushing-grinding and screening operations and then used in Bohme abrasion test run. The performance of abrasion process was evaluated as the decrease in the surface roughness of marble samples and the increase in the surface gloss. As a result of tests, the performance of granite wastes and Al2O3 abrasives were compared. Test results showed that granite wastes caused a relative decrease in marble surface roughness and an increase in gloss especially in high CaCO3 and low MgCO3 containing soft rocks such as travertine. (C) 2018 Elsevier Ltd. All rights reserved.