TÜBİTAK Marmara Research Center, Gebze, Turkey.

Átírás

1 Vildan ÖZKAN 1,*,Đsmail H. SARPÜN 2, Sabri TUNCEL 3 1,* Muş Alparslan University, Science Faculty Physics Dept., Muş, Turkey, v.ozkan@alparslan.edu.tr 2 Afyon Kocatepe University, PhysicsDept., Afyonkarahisar, Turkey. 3 TÜBİTAK Marmara Research Center, Gebze, Turkey.

2 Introduction Marbles Materials and Methods Experiments and Results Conclusions

3 TÜBİTAK MRC The Scientific and Technological Research Council of Turkey (TÜBİTAK) TÜBİTAK has been founded in Ankara in 1963 with the aim of developing, promoting, planning, coordinating and funding the R&D activities, in respect of the priorities for Turkey s development. Scientific research and technological development activities of TÜBİTAK are conducted through its research institutes. Marmara Research Centre (MRC) in Gebze is the oldest and largest research organization under TÜBİTAK. Materials Institute (MI) of the Marmara Research Center, the largest Industrial R&D complex in Turkey, aims to increase the global competitiveness of the Turkish Materials industry by delivering contract research projects, industrial testing and characterization services and technical training.

4 The Non-Destructive Testing Laboratory which is part of the NDT& Acoustical Technologies Group at MI was established in The first industrial project of the laboratory, and also of MRC, was the radiographic and ultrasonic testing of the weld seams during the construction of Istanbul Bosphorus Bridge the same year. Then the laboratory extended its facilities into the application of different NDT techniques and research activities, particularly in ultrasonics to meet the demands of the Turkish Industry. Starting from 2000, training and certification of NDT personnel program has also been carried out according to EN 473 under the supervision of Level-3 certified researchers. We can apply in our laboratory six main NDT methods. These are, radiography (RT), ultrasonic (UT), magnetic particle (MT), penetrant (PT), eddy current (ET) and acoustic emission (AE). All of our equipment is mobile and used for both research and industrial service purposes. Our 19 NDT test methods are accredited by DAP/Germany.

5 Introduction The marbles having small grain size, dominant grain size distribution in a narrow range, and irregular grain boundary are more resistant against the ageing teststhan theoneswithlargegrain size, grain sizedistribution in awide range, and straight grain boundary. Marble is no less complex; it is a product of metamorphism of limestone beds subjected to heat and/or pressure. It appears to be only anisotropic. The very good physical and mechanical properties of marble, such as its high resistance to abrasion, translucence and capability to be polished, as well as its high strength and hardness render it one of the most widely used structural materials even today for the construction of both buildings and sculptures.

6 Ultrasonic testing of marbles has been examined by several researchers and all of them observed that the ultrasonic technique is suitable and accurate enough to detect chemical and structural anomalies and discontinuities in marble material. In this work, we have studied the mean grain size determination of some marbles using ultrasonic velocity measurements, ultrasonic attenuation and the ultrasonic relative attenuation (URA) method. In addition this work shows that there is a linear relation between experimental and evaluated mean grain size in all marble groups. Thesevalues have been compared with results obtained by polarize microscope images.

7 Marbles Marble samples have been collected from different regions of Turkey. Marble samples classified into three groups according to formations; Marble Samples Sedimentary marble Metamorphic marble Travertine marble

8 Materials and Methods Thicknesses of the samples varied from 9 mm to 12 mm with a front surface dimension of 5 5 cm 2. Front surface of all samples has been manufacturely polished and therefore roughness has been eliminated. Sedimentary Marble Samples; Sedimentary marbles are composed largely of quartz with other common minerals including feldspars, amphiboles, clay minerals, sandstone with quartz, limestone and sometimes more exotic igneous and metamorphic minerals. Sedimentary rocks are economically important since they can be used as construction material. Metamorphic Marble Samples; Marble is generally a metamorphic rock resulting from regional or contact metamorphism of sedimentary carbonate rocks, either limestone or dolostone. This metamorphic process causes a complete recrystallization of the original rock into an interlocking mosaic of calcite and/or dolomite crystals. Travertine Marble Samples; Travertine is a terrestrial sedimentary rock, formed by the precipitation of carbonate minerals from geo-thermally heated hot-springs. Travertine is often used as a building material.

9 Experiments and Results Ultrasonic Measurements The determination of transmission velocity of ultrasonic waves through the marbles were performed by a Sonatest Sitescan 150 pulser/receiver instrument with Sonatest SLH2-10 and Sonatest SLH4-10 transducer operated at the frequency of 2 MHz-4 MHz at the room temperature. The velocity values were obtained directly from knowledge of the properties of the flaw detector. According to the ultrasonic attenuation method, the amplitudes of successive backwall echoes are used to determine the attenuation coefficient of marbles. A modified URA (Ultrasonic Relative Attenuation) method was also applied to samples. According to this method the rate of peak heights was used to determine mean grain size of samples. Mean grain size was calculated by using software with polarized microscopy.

10 The mean values of the velocity, attenuation coefficient and rate of peak heightsin thethreetypesof marblesweregiven in Table 1 withmean grain size of samples.

11 ReferenceGraphs In ultrasonic methods reference graphs have to be plotted to determine the mean grain size of samples. The reference graph for the ultrasonic velocity method was plotted using the valuesfromtable 1 asshownin Fig. 1. Figure 1. Reference graph of marble samples according to ultrasonic velocity method.

12 One can see from the Fig. 1., Sedimentary marble samples correlation coefficient is higher than the other samples in ultrasonic velocity method. The reference graph for the ultrasonic attenuation method was plotted using thevaluesfromtable 1 asshowninfig. 2. Figure 2. Reference graph of marble samples according to ultrasonic attenuation method.

13 TheURA values of marble samples are shown in Fig. 3.which was plotted using the values from Table 1. Figure 3. Reference graph of marble samples according to modified URA method. The URA and ultrasonic attenuation methods depend on the rate of screen height of peaks.

14 Evaluation of Mean Grain Size In all methods fitting equations were used to evaluate the mean grain size of samples. The ultrasonic methods have been compared in the separate graphs for each marble group. The evaluated mean grain size of samples were given in Table 2 for sedimentary marble samples. The comparison of the experimental and the evaluatedmeangrainsizeresultshavebeenshowninfig. 4. Table 2. Evaluated mean grain size of sedimentary marble samples by using 4 MHz probe.

15 Figure 4. Comparison of experimental and evaluated mean grain size of sedimentary marbles. The evaluated values obtained using 4 MHz probe are given in Table 3 and the comparison of the mean grain sizes are shown in Fig. 5., for metamorphic marble samples.

16 Table 3. Evaluated mean grain size of metamorphic marble samples by using 4 MHz probe.

17 Figure 5. Comparison of mean grain sizes of metamorphic marble samples. The evaluated values measured by 4 MHz probe are given in Table 4 and the comparison of experimental and evaluated mean grain sizes of samples are given in Fig. 6., for travertine marble samples.

18 Table 4. Evaluated mean grain size of travertine marble samples by using 4 MHz probe.

19 Figure 6. Comparison of experimental and evaluated mean grain sizes of travertine marble samples.

20 Conclusions Ultrasonic velocity and attenuation values have been measured by using probes of 2 MHz and 4 MHz and their relationship with the grain sizes have been examined. It has been found that there is a linear relation between experimental and evaluated mean grain size in all marble groups. One can compare three marble groups by their ultrasonic properties. The correlation coefficients of metamorphic marble samples are higher than the others and also travertine marble samples are not suitable because of their porosity structure. Besides, as the mean grain size decrease, the ultrasonic velocity and the rateof heights of successive peaks increase whereas the ultrasonic attenuation coefficient decreases.

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