scholarly journals The Size Effect and Microstructure Changes of Granite after Heat Treatment

2021 ◽  
Vol 2021 ◽  
pp. 1-14
Author(s):  
Zhongping Guo ◽  
Jian Li ◽  
Yongqi Song ◽  
Chengqian He ◽  
Fuyu Zhang
Keyword(s):  
Fracture Toughness ◽  
High Temperature ◽  
Fracture Mechanics ◽  
Size Effect ◽  
Mineral Composition ◽  
Fracture Morphology ◽  
Optical Microscope ◽  
High Temperature Treatment ◽  
Nonlinear Characteristics ◽  
Nonlinear Fracture

High temperature can change the mechanical properties of granite, with significant nonlinear characteristics, and at the same time change its microstructure. Therefore, two kinds of granites are used in this paper: one is normal temperature granite and the other is granite treated at 600°C, and a detailed comparative study is made. The fracture toughness of two kinds of rocks was tested by fracture tests, and the results were analyzed by a nonlinear fracture mechanics model (SEL). At the same time, in order to understand the influence of high temperature on the mineral composition and microstructure of granite, XRD, optical microscope, and SEM were used to observe the mineral composition, microcracks, and fracture morphology of granite. The results show the following: (1) high temperature significantly changes the fracture mechanics parameters of granite. The fracture toughness of granite treated at 600°C is significantly lower than that of untreated granite, which is reduced by more than 60%. (2) No obvious size effect was found in the untreated granite, while the size effect of the granite after treatment at 600°C was significant. (3) The granite after high-temperature treatment showed strong nonlinear characteristics, and the SEL can reasonably describe and explain its nonlinear fracture characteristics. (4) The brittleness of the granite treated at 600°C decreased and the ductility increased. The microscopic morphology of the fracture was rough, with obvious steps and rivers. The microcracks and porosity had increased significantly, but the main components did not change significantly.

scholarly journals Effect of High Temperature (600°C) on Mechanical Properties, Mineral Composition, and Microfracture Characteristics of Sandstone

2020 ◽  
Vol 2020 ◽  
pp. 1-19
Author(s):  
Jian Li ◽  
Zhao-Wen Du ◽  
Zhong-Ping Guo
Keyword(s):  
Mechanical Properties ◽  
Fracture Toughness ◽  
Tensile Strength ◽  
High Temperature ◽  
Mineral Composition ◽  
Coal Gasification ◽  
Testing Machine ◽  
High Temperature Treatment ◽  
Unstable Fracture ◽  
Rock Destruction

Rock destruction under high-temperature conditions is a key issue for nuclear waste treatment projects, underground coal gasification, and improvement of the use of geothermal energy for heating. Therefore, in this study, various methods and techniques were integrated to study the changes in mechanical properties, mineral composition, and microscopic fracture characteristics of Sichuan sandstone treated at 600°C. First, the fracture toughness and indirect tensile strength of untreated sandstones and high-temperature treated sandstones were tested by the MTS testing machine, and the double-K model (DKFM) was used to estimate the unstable fracture toughness. Then, the diffraction spectra of sandstone were analyzed with an X-ray diffractometer to determine the mineral composition change after heat treatment. Finally, the microscopic features of sandstone were observed through a scanning electron microscope (SEM) and optical microscope. The results show the following. (1) There is no significant change in the tensile strength and fracture toughness of Sichuan sandstone treated at 600°C. (2) The brittleness of Sichuan sandstone decreases and the ductility increases after high-temperature treatment. (3) The unstable fracture toughness value Kun obtained by the double-K model (DKFM) is significantly larger than the apparent fracture toughness value Kif. (4) After treatment at 600°C, the clay minerals in the sandstone changed significantly. Kaolinite is dehydroxylated to metakaolinite, which may increase the ductility of the rock.

Fracture Mechanics of Y2O3 Ceramics at High Temperatures

2014 ◽  
Vol 89 ◽  
pp. 88-93
Author(s):  
Marek Boniecki ◽  
Zdzislaw Librant ◽  
Władysław Wesołowski ◽  
Magdalena Gizowska ◽  
Marcin Osuchowski ◽  
...  
Keyword(s):  
Fracture Toughness ◽  
Grain Size ◽  
High Temperature ◽  
Fracture Mechanics ◽  
High Purity ◽  
Room Temperature ◽  
Bending Strength ◽  
Hot Isostatic Pressing ◽  
Temperature Changes ◽  
Four Point Bending

Fracture toughness KIc and four-point bending strength σc at high temperature (up to 1500 °C) of Y2O3 ceramics of various grain size were measured. The ceramics were prepared by pressureless air sintering and next hot isostatic pressing of high purity (99.99%) Y2O3 powder. Relative density of about 99 % was achieved. Photos of microstructures revealed small pores distributed mainly inside grains. For smallest grain size (2 - 9 μm) ceramics KIc and σc are almost constant from 20 ° to 1200 °C and next they decrease. For biggest grain size (about 44 μm) they increase up to 800 °C and next they keep constant up to 1200 °C. The micrographs analyses of fracture surfaces indicated that transgranular mode of fracture at room temperature changes to almost intergranular at higher temperatures.

Influence of Nowonty Phase on the Fracture Toughness of SiC/MoSi2 Composites

2007 ◽  
Vol 353-358 ◽  
pp. 1326-1329 ◽  
Author(s):  
Peng Chao Kang ◽  
Gao Hui Wu ◽  
Zhong Da Yin
Keyword(s):  
Fracture Toughness ◽  
High Temperature ◽  
Ternary Phase ◽  
Volume Fraction ◽  
Temperature Treatment ◽  
Precursor Powder ◽  
High Temperature Treatment ◽  
Negative Effect ◽  
Reactive Hot Pressing ◽  
Sic Reinforcement

MoSi2-SiC precursor powder has been synthesized via the mechanical alloy method with the elements Mo, Si and C powder. The SiC/MoSi2 composites with different SiC volume fraction have been prepared by reactive hot-pressing the precursor powder at 1350 °C. There is a significant increase in the fracture toughness due to addition of SiC reinforcement. However, the intermediary ternary phase exists in this system—namely, Mo5Si3C, Nowotny phase, which has negative effect on the fracture toughness, and can be eliminated through high temperature treatment at 1600 °C for 2 hrs.

Effect of Different Tempering Temperatures on Microstructure and Impact Property of 20CrMnTi Steel

2014 ◽  
Vol 900 ◽  
pp. 92-95
Author(s):  
Sheng Xu Liu ◽  
Yi Qiang Xiao ◽  
Ming Long Kang ◽  
Jian Min Zeng ◽  
Guo An Wang ◽  
...  
Keyword(s):  
Electron Microscope ◽  
High Temperature ◽  
Low Temperature ◽  
Fracture Morphology ◽  
Optical Microscope ◽  
Impact Property ◽  
Medium Temperature ◽  
The Impact ◽  
Type Of Fracture ◽  
Scanning Electron

The effect of different tempering temperatures on microstructure and impact property of 20CrMnTi steel has been studied on Zwick/roell Amsler PKP 450 pendulum machine, SU-8020 scanning electron microscope (SEM) and optical microscope. The results shows that the impact property of 20CrMnTi steel is dramatically improved after high-temperature tempering. However, the minimum value occurs when it was tempered at 350°C because of low-temperature tempering brittlement at this degree. The SEM fracture morphology was typical dimples after high temperature tempering, and the type of fracture was ductile fracture; the type of cleavage characteristic and quasi cleavage characteristic were generated on the fracture morphology at low-temperature and medium-temperature tempering respectively, and the type of fracture was brittle.

scholarly journals Aplikasi Size Effect Law Pada Beton Marine dengan Pola Bukaan Tarik

2021 ◽  
Vol 28 (2) ◽  
pp. 143-154
Author(s):  
Fella Supazaein ◽  
Resmi Bestari Muin
Keyword(s):  
Fracture Mechanics ◽  
Size Effect ◽  
Fracture Energy ◽  
High Performance ◽  
High Performance Concrete ◽  
Actual Performance ◽  
Nonlinear Fracture Mechanics ◽  
Nonlinear Fracture ◽  
Sample Height ◽  
Marine Concrete

AbstrakPengembangan infrastruktur di bidang maritim adalah salah satu strategi untuk mengembangkan perekonomian. Beton marine banyak digunakan sebagai material struktur  pada pembangunan infrastruktur di bidang maritim tersebut. Beton marine harus menggunakan beton high performance concrete (HPC). Dengan berkembangnya teknologi beton HPC pengoptimalan efisiensi komponen struktur menjadi lebih signifikan.Pada perencanaan pelaksanaan pembangunan khususnya pada tahap analisa struktur, jarang sekali direncanakan kekuatan terhadap mekanika fraktur yang seharusnya juga didesain agar keruntuhan secara fraktur bisa diatasi. penelitian ini mengkaji aplikasi size effect law pada beton HPC pada balok  dengan berbagai ukuran yang sudah ditentukan (small, medium dan high) untuk memperoleh nilai energy fraktur (Gf). Hasil penelitian ini dapat berkontribusi dalam penerapam metode untuk mendapatkan nilai parameter dari kinerja fraktur. selain itu, data parameter dapat digunakan dalam mengkalibrasi analisa numerik elemen struktur berbasis fraktur energi agar dapat dipastikan kinerja struktur yang sesungguhnya.Hasil pengujian menunjukkan energi fraktur pada benda uji set II (rasio takik terhadap tinggi sample = 1/6) lebih besar 8,4% dari benda uji set I (rasio takik terhadap tinggi sample = 1/3). Factor geometri  dan kemiringan pada garis regresi (A) menurun selaras dengan menurunnya rasio takik. Dari angka keruntuhan nilai  berada pada range 0,1 <  < 10 yang menandakan material didesain harus dengan kriteria nonlinear fracture mechanic.Kata-kata Kunci: Beton marine, mekanika fraktur, size effect law, nonlinear fracture mechanics AbstractInfrastructure development in the maritime sector is one strategy for developing the economy. Marine concrete is widely used as a structural material in infrastructure development in the maritime sector. Marine concrete must use high performance concrete (HPC). With the development of HPC concrete technology, optimization of the efficiency of structural components has become more significant.In the construction implementation planning, especially at the structural analysis stage, it is rare to plan the strength of the fracture mechanics which should also be designed so that fracture collapse can be overcome. This study examines the application of size effect law on HPC concrete on beam of various predetermined sizes (small, medium and high) to obtain the fracture energy value (Gf). The results of this study can contribute to the application of the method to obtain parameter values of fracture performance. In addition, parameter data can be used in calibrating the numerical analysis of energy fracture based structural elements in order to ascertain the actual performance of the structure.The results showed that fracture energy in specimen set II (ratio of notches to depth = 1/6) was 8.4% greater than specimen set I (ratio of notches to sample height = 1/3). The geometric factor  and slope of the regression line (A) decreased in line with the decreasing notch ratio. From the brittleness number, the value of β is in the range 0.1 <β <10 which indicates that the material should  designed with nonlinear fracture mechanic criteria.Key words: marine concrete, fracture mechanics, size effect law, nonlinear fracture mechanics

Experimental Research on Size Effect of Mode II Fracture Toughness of Concrete

2013 ◽  
Vol 438-439 ◽  
pp. 229-234
Author(s):  
Shao Wei Hu ◽  
Liang Hu
Keyword(s):  
Fracture Toughness ◽  
Fracture Mechanics ◽  
Size Effect ◽  
Fracture Energy ◽  
Experimental Research ◽  
Shear Fracture ◽  
Concrete Strength ◽  
Displacement Curve ◽  
Fracture Parameters ◽  
Mode Ii Fracture Toughness

Based on specimen size, which is the main reason of the shear fracture toughness of concrete, experimental research was carried out by 5 groups including 40 symmetrically loading specimens with different length and height. Through load and crack tip sliding displacement curve P-CTSD, load and strain curve P-ε and load and time curve P-t, the effects of length and height of specimens to shear fracture toughness were studied. Specimen stability is strengthened with increasing of length and weakened with increasing of height. Size effect of fracture toughness is weakened with increasing of length, is strengthened with the increasing of height. Fracture toughness increases with the increasing of length, decreases with the increasing of height. Research Background The size effect exists in parameters of concrete, such as concrete strength, modulus of elasticity, fracture toughness, fracture energy and so on [1-. In 1961, the theory of fracture mechanics was applied to concrete structure for the first time by Kaplan [. A vast majority of research work about concrete fracture mechanics was carried out by international scholars [6-. As the development of fracture theory of concrete, the size effect of fracture parameters became the focal point in theory study. Karihaloo [ pointed out that the size effect of concrete strength strengthens with the increasing of components size, however, the size effect weakens when crack length decreased relative to the size of specimens. Hu [3, 10, 11] accounted for the size effect by applying the theory of boundary effect and carried out the concept of local fracture energy which changes with width of fracture process zone. Based on the fictitious crack model, an analytical method [12, 13] for predicting the effective fracture toughness of concrete of three-point bending notched beams is proposed and the effects of initial seam height ratio and height on fracture parameters were carried out by Wu and Xu. At present, research on shear fracture toughness of concrete is immature and there are almost no papers about the size effect of shear fracture toughness of concrete. Aiming at the issue, this paper conducts a study on the size effect of shear fracture toughness of concrete by using symmetrically single-edge notched specimen.

Microstructure, hardness, and fracture toughness evolution of hot-pressed SiC/Si3N4nano/micro composite after high-temperature treatment

2006 ◽  
Vol 97 (6) ◽  
pp. 772-777
Author(s):  
Pavol Šajgalík ◽  
Miroslav Hnatko ◽  
Štefánia Lojanová ◽  
Zoltán Lenčéš ◽  
Helena Pálková ◽  
...  
Keyword(s):  
Fracture Toughness ◽  
High Temperature ◽  
Temperature Treatment ◽  
High Temperature Treatment

Detecting the size effect in concrete beams using nonlinear fracture mechanics

1997 ◽  
Vol 19 (8) ◽  
pp. 605-616 ◽  
Author(s):  
Ahmed S.E. Morgan ◽  
J. Niwa ◽  
T. Tanabe
Keyword(s):  
Fracture Mechanics ◽  
Size Effect ◽  
Concrete Beams ◽  
Nonlinear Fracture Mechanics ◽  
Nonlinear Fracture
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