동적초미소경도법을 이용한 화강암의 경도 산정법

Abstract

This study is to estimate the dynamic hardness of Deajeon granite by the dynamic ultra-micro hardness method. For this purpose, samples are obtained from cores of the Daejeon granite with the depth of 41 m and 223 m. In addition, the dynamic hardness was measured by the dynamic ultra-micro hardness tester with the method of indentation, load-unload, and cycle tests. then elastic modulus and plastic modulus were also calculated from their results. The results are following as: From the observation of microphotographs, minerals in the Daejeon granite are mainly consisted of feldspar, quartz, and mica. Along with the minerals boundary arbitrarily was divided the samples from the first to the fortieth sections in the depth of 41 m and 223 m. Measurements were done 5 times for each test method, 15 times in each section, and 600 times in each spot. Therefore, measurements are totally performed 1200 times. The size and Martens hardness were 8∼10 m, more than 4000 N/mm2, in quartz, 10∼13 m and, 2000∼4000 N/mm2, in feldspar, 24∼30 m and less than 2000 N/mm2. By the indentation test, average of Martens hardness values were 4534.7 N/mm² in quartz, 3639.8 N/mm² in feldspar, 990.5 N/mm², in mica at the depth of 41 m, and 4622.4 N/mm² in quartz, 3759.9 N/mm² in feldspar, 1121.4 N/mm² in mica at the depth of 223 m, respectively. By the load-unload test, average of Martens hardness values were 4524.4 N/mm² in quartz, 3726.1 N/mm² in feldspar, 836.3 N/mm² in mica at the depth of 41 m and 4604.3 N/mm² in quartz, 3715.1 N/mm² in feldspar, 939.8 N/mm² in mica at depth of 223 m respectively. By the cycle test, average of Martens hardness values were 4300.4 N/mm² in quartz, 3454.6 N/mm² in feldspar, 836.3 N/mm² in mica at the depth of 41 m and 4366.3 N/mm² in quartz, 3478.3 N/mm² in feldspar, 806.3 N/mm² in mica at the depth of 223 m respectively. There was only a few difference in the results of indentation and load-unload tests, however cycle test showed lower 200 N/mm² values than the other two tests. Martens hardness values can be divided by three groups, that is, Group-1 of less than 2000 N/mm², Group-2 of 2000∼4000 N/mm² and Group-3 of more than 4000 N/mm². When Martens hardness values were compared and analyzed with Mohs scale the ranges of Group-1 might be matched with mica, Group-2 with feldspar, and Group-3 with quartz. By the load-unload test, average Eit represented Young's modulus 88.2 GPa in quartz, 71.9 GPa in feldspar, and 51.2 GPa in mica at the depth with 41 m and 89.4 GPa in quartz, 71.6 GPa in feldspar, 57.1 GPa in mica at the depth with 223 m respectively. By the cycle test, average it represented elastic and plastic 79.1 % in quartz, 76.9 % in feldspar, 46.5 % in mica at the depth with 41 m and 79.1 % in quartz, 75.2 % in feldspar, 41.2 % in mica at the depth with 223 m respectively. In conclusion, it means that hardness test of each mineral is possible to be measured by dynamic ultra-micro hardness method. In addition, this method might be measured elastic modulus and plastic modulus, Poisson’s ratio as well as dynamic hardness in various materials.