scholarly journals An advanced assessment of mechanical fracture parameters of sandstones depending on the internal rock texture features

2019 ◽  
pp. 157-168 ◽  
Author(s):  
Leona Vavro
Keyword(s):  
Texture Features ◽  
Mechanical Fracture ◽  
Fracture Parameters ◽  
Rock Texture

Fracture Resistance of AAAS Composites with Ceramic Precursor

2021 ◽  
Vol 322 ◽  
pp. 54-59
Author(s):  
Iva Rozsypalová ◽  
Petr Daněk ◽  
Pavla Rovnaníková ◽  
Zbyněk Keršner
Keyword(s):  
Mouth Opening ◽  
Crack Model ◽  
Arithmetic Means ◽  
Mechanical Fracture ◽  
Three Point Bending ◽  
Static Modulus ◽  
Fracture Parameters ◽  
Ceramic Precursors ◽  
Static Modulus Of Elasticity

The paper deals with selected alkali-activated aluminosilicate (AAAS) composites based on ceramic precursors in terms of their characterization by mechanical fracture parameters. Composites made of brick dust as a precursor and an alkaline activator with a silicate modulus of Ms = 0.8, 1.0, 1.2, 1.4 and 1.6 were investigated. The filler employed with one set of composites was quartz sand, while for the other set it was crushed brick. The test specimens had nominal dimensions of 40 × 40 × 160 mm and were provided with notches at midspan of up to 1/3 of the height of the specimens after 28 days. 6 samples from each composite were tested. The specimens were subjected to three-point bending tests in which force vs. displacement (deflection at midspan) diagrams (F–d diagrams) and force vs. crack mouth opening (F–CMOD) diagrams were recorded. After the correction of these diagrams, static modulus of elasticity, effective fracture toughness, effective toughness and specific fracture energy values were determined using the Effective Crack Model and the Work-of-Fracture method. After the fracture experiments, informative compressive strength values were determined from one of the parts. All of the evaluations included the determination of arithmetic means and standard deviations. The silicate modulus values and type of filler of the AAAS composites significantly influenced their mechanical fracture parameters.

Fracture Response of Fine-Grained Cement-Based Composite Specimens with Special Inclusions

2019 ◽  
Vol 292 ◽  
pp. 63-68 ◽  
Author(s):  
Michal Vyhlídal ◽  
Iva Rozsypalová ◽  
Tomáš Majda ◽  
Petr Daněk ◽  
Hana Šimonová ◽  
...  
Keyword(s):  
Transition Zone ◽  
Interfacial Transition Zone ◽  
Mechanical Fracture ◽  
Three Point Bending ◽  
Fine Grained ◽  
Fracture Parameters ◽  
Edge Notch ◽  
Fracture Tests ◽  
Materials Used ◽  
Bending Fracture

This paper concerns research into the importance of the interfacial transition zone around inclusions of selected materials in fine-grained cement-based composite. Tests were performed on eight sets of prismatic test specimens. The sets differed in the inclusion materials used, which were placed at midspan above the initial central edge notch. The first was a reference set without any inclusion, the second contained a steel inclusion, four more contained different types of rock inclusion, the seventh contained an inclusion of extruded polystyrene, and the last contained a space of the same dimensions as that occupied by the inclusions in sets 2 to 7. The test specimens were subjected to three-point bending fracture tests at the age of (usually) 28 days. The fracture response was analysed by means of fracture mechanics theory, and apparent mechanical fracture parameters (modulus of elasticity, fracture toughness and fracture energy) were evaluated. The conclusion shows that a possible relationship exists between the differences in the mechanical fracture parameters of specimens with/without an inclusion and the existence of the interfacial transition zone.

Effect of Cement Dosage on Selected Mechanical Fracture Parameters of Concretes

2014 ◽  
Vol 617 ◽  
pp. 239-242 ◽  
Author(s):  
Hana Šimonová ◽  
Ivana Havlíková ◽  
Petr Daněk ◽  
David Lehký ◽  
Barbara Kucharczyková ◽  
...  
Keyword(s):  
Fresh Concrete ◽  
Mechanical Fracture ◽  
Bending Tests ◽  
Fracture Properties ◽  
Three Point Bending ◽  
Fracture Parameters ◽  
Edge Notch

Mechanical fracture parameters obtained from three-point bending tests on concrete specimens with a central edge notch are introduced in this paper. A total of four sets of specimens were tested. The concrete used in each set differed in cement dosage, which ranged from 250 to 455 kg per m3of fresh concrete. Three specimens in each set were tested at the age of 28 days. Increasing the dosage of cement influences the mechanical fracture properties of concretes in both positive and negative ways.

Fracture Parameters of Alkali-Activated Aluminosilicate Composites with Ceramic Precursor

2020 ◽  
Vol 309 ◽  
pp. 73-79
Author(s):  
Hana Šimonová ◽  
Ivana Kumpová ◽  
Iva Rozsypalová ◽  
Patrik Bayer ◽  
Petr Frantik ◽  
...  
Keyword(s):  
Fracture Process ◽  
Fracture Process Zone ◽  
Process Zone ◽  
Mouth Opening ◽  
Crack Mouth Opening Displacement ◽  
Crack Model ◽  
Mechanical Fracture ◽  
Ceramic Precursor ◽  
Fracture Parameters ◽  
Alkali Activated

This paper deals with selected alkali-activated aluminosilicate composites with a ceramic precursor in terms of their characterization using mechanical fracture parameters. Three composites were studied. They were manufactured using brick powder as a precursor and an alkaline activator with a dimensionless silicate modulus of Ms = 1.0, 1.2 and 1.4. The test specimens were nominally 40 × 40 × 160 mm in size and had a central edge notch with a depth of 1/3 of the specimen’s height. At least 6 specimens made of each composite were tested at the age of 28 days. The specimens were subjected to three-point bending tests, during which diagrams showing force vs. deflection at midspan (F–d diagrams) and force vs. crack mouth opening displacement (F–CMOD diagrams) were recorded. After the processing of these diagrams, values were determined for the static modulus of elasticity, effective fracture toughness (including its initiation component from the analysis of the first part of the F–CMOD diagrams), effective toughness and specific fracture energy using the effective crack model, Work-of-Fracture method, and Double-K fracture model. After the fracture experiments had been performed, compressive strength values were determined for informational purposes from one part of each specimen that remained after testing. In order to obtain visual information about the internal structure of the composites before and after the mechanical testing, the selected specimen was examined via X-ray microtomography. Tomographic measurements and image processing were performed for the qualitative and quantitative evaluation of internal structural changes with an emphasis on the calculation of porosimetry parameters as well as the visualization of the fracture process zone. The fractal dimension of the fracture surface and fracture process zone was determined. The porosity and microstructure images of selected samples taken from specimens were assessed.

scholarly journals Mechanical Fracture Parameters of Cement Based Mortars with Waste Glass Powder

2017 ◽  
Vol 190 ◽  
pp. 86-91 ◽  
Author(s):  
Hana Šimonová ◽  
Jana Zahálková ◽  
Pavla Rovnaníková ◽  
Patrik Bayer ◽  
Zbyněk Keršner ◽  
...  
Keyword(s):  
Glass Powder ◽  
Waste Glass ◽  
Mechanical Fracture ◽  
Fracture Parameters ◽  
Waste Glass Powder

Identification of AAAS Composites Mechanical Fracture Parameters

2021 ◽  
Vol 322 ◽  
pp. 66-71
Author(s):  
Martin Lipowczan ◽  
David Lehký ◽  
Iva Rozsypalová ◽  
Petr Daněk ◽  
Pavla Rovnaníková ◽  
...  
Keyword(s):  
Fracture Energy ◽  
Modulus Of Elasticity ◽  
Crack Mouth Opening Displacement ◽  
Crack Model ◽  
Mechanical Fracture ◽  
Specific Fracture Energy ◽  
Static Modulus ◽  
Fracture Parameters ◽  
Static Modulus Of Elasticity ◽  
Specific Fracture

The paper deals with selected alkali-activated aluminosilicate (AAAS) composites based on ceramic precursors in terms of characterization by mechanical fracture parameters. Two composites made of brick dust as a precursor and an alkaline activator with a silicate modulus Ms = 1.0 were investigated. The composites differed in the fineness of grinding of the precursor – in the first set it was 0 to 1 mm, in the second set 0 to 0.3 mm. The filler was crushed brick. The test specimens had nominal dimensions of 40 × 40 × 160 mm and were provided with notches in the middle of the span up to 1/3 of the depth of the specimens after 28 days of hardening. Five to six specimens from each composite set were tested. The specimens were subjected to three-point bending tests, in which force vs. displacement (deflection in the middle of the span) diagrams (F–d diagrams) and force vs. crack mouth opening displacement (F–CMOD) diagrams were recorded. After correction of these diagrams, the values of static modulus of elasticity, effective fracture toughness, effective toughness and specific fracture energy were determined using the Effective Crack Model and the Work-of-Fracture method. After the fracture experiments, the values of informative compressive strength were determined on one of the fractured parts. At the same time, the values of static modulus of elasticity, tensile strength and specific fracture energy were identified using artificial neural networks and F–d diagrams measured and simulated in the ATENA FEM software. All evaluations included the determination of basic statistics of parameters.

scholarly journals Tentative Characterization of Old Structural Concrete through Mechanical Fracture Parameters

2017 ◽  
Vol 190 ◽  
pp. 414-418 ◽  
Author(s):  
Hana Šimonová ◽  
Petr Daněk ◽  
Petr Frantík ◽  
Zbyněk Keršner ◽  
Václav Veselý
Keyword(s):  
Structural Concrete ◽  
Mechanical Fracture ◽  
Fracture Parameters

scholarly journals Components of the Fracture Response of Alkali-Activated Slag Composites with Steel Microfibers

2019 ◽  
Vol 9 (9) ◽  
pp. 1754 ◽  
Author(s):  
Hana Šimonová ◽  
Petr Frantík ◽  
Zbyněk Keršner ◽  
Pavel Schmid ◽  
Pavel Rovnaník
Keyword(s):  
Mouth Opening ◽  
Crack Mouth Opening Displacement ◽  
Model Parameters ◽  
Crack Model ◽  
Mechanical Fracture ◽  
Alkali Activated Slag ◽  
Fracture Parameters ◽  
Fracture Tests ◽  
Activated Slag ◽  
Alkali Activated

Knowledge of the mechanical and primarily fracture parameters of composites with a brittle matrix is essential for the quantification of their resistance to crack initiation and growth, and also for the specification of material model parameters employed for the simulation of the quasi-brittle behavior of structures made from this type of composite. Therefore, the main target of this paper is to quantify the mechanical fracture parameters of alkali-activated slag composites with steel microfibers and the contribution of the matrix to their fracture response. The first alkali-activated slag composite was a reference version without fibers; the others incorporated steel microfibers amounting to 5, 10, 15 and 20% by weight of the slag. Prism specimens with an initial central edge notch were used to perform the three-point bending fracture tests. Load vs. displacement (deflection at midspan) and load vs. crack mouth opening displacement diagrams were recorded during the fracture tests. The obtained diagrams were employed as inputs for parameter identification, the aim of which was to transfer the fracture test response data to the desired material parameters. Values were also determined for fracture parameters using the effective crack model, work-of-fracture method and double-K fracture model. All investigated mechanical fracture parameters were improved by the addition of steel microfibers to the alkali-activated matrix. Based on the obtained results, the addition of 10 to 15% of microfibers by weight is optimal from the point of view of the enhancement of the fracture parameters of alkali-activated slag composite.

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