Regularities of main crack formation in heterogeneous materials

2020 ◽  
Author(s):  
Ekaterina Damaskinskaya ◽  
Vladimir Hilarov ◽  
Ivan Panteleev ◽  
Dmitry Korost
2016 ◽  
Vol 722 ◽  
pp. 247-253 ◽  
Author(s):  
Alexander N. Kravcov ◽  
Pavel Svoboda ◽  
Adam Konvalinka ◽  
Elena B. Cherepetskaya ◽  
Ivan E. Sas ◽  
...  

The paper discusses the use of acoustic emission, stress-memory effect, and X-ray computed microtomography (μST) to detect the onset of destruction of specimens of concrete and basalt which are widely used in construction. It is shown that the most informative parameter is acoustic emission activity based on which the onset of the formation of a main crack can be identified. The geometry of the crack is determined using computed X-ray tomography.


2012 ◽  
Vol 166-169 ◽  
pp. 1121-1126
Author(s):  
Worapong Srisoros ◽  
K Kaewpetch ◽  
P Ariyasuk ◽  
A Chokcharoenmahasarn

The Rigid-Body-Spring-Model was applied for analyzing fire-damaged concrete beam with voronoi random mesh. Material models of fire-damaged concrete was defined by the experiment. To evaluate the performance and effectiveness of the RBSM with voronoi random mesh, four models of fire damaged concrete beam at various temperatures covered 20°C and 100 to 800°C were analyzed. According to the results, heated specimen 800°C has the lowest strength capacity and internal stress comparing to the other specimens. Main crack of 800°C specimen appears earlier than other specimens. Strength capacity of heated specimen 400°C was higher than the results of unheated specimen because of hydration reaction of large cement clinker was accelerate during heating.


2021 ◽  
Vol 2021 ◽  
pp. 1-10
Author(s):  
Bo Wu ◽  
Shixiang Xu ◽  
Guowang Meng ◽  
Junhua Cai ◽  
Han Wei ◽  
...  

Based on LS-DYNA numerical simulation analysis and comparison with laboratory tests, the blasting crack development dynamic evolution mechanism of elliptical bipolar linear shaped charge is analyzed. The development law of rock crack and optimal radial decoupling coefficient under different blast hole diameters were studied. The results revealed that the blasting with elliptical bipolar linear shaped charge had a remarkable effect on the directional crack formation, and the maximum effective stress of rock close to the position of shaped charge in the direction of concentrating energy is about 2.3 times of that in the direction of nonconcentrated energy. Moreover, the directional crack could be formed by blasting with elliptical bipolar linear shaped charge with different hole diameters, whilst the length of the main crack was related to the radial decoupling coefficient. Particularly, the main crack reached the longest when the radial decoupling coefficient was 3.36.


2018 ◽  
Vol 84 (12) ◽  
pp. 68-72
Author(s):  
A. B. Maksimov ◽  
I. P. Shevchenko ◽  
I. S. Erokhina

A method for separating the work of impact into two parts - the work of the crack nucleation and that of crack growth - which consists in testing two samples with the same stress concentrators and different cross-sectional dimensions at the notch site is developed. It is assumed that the work of crack nucleation is proportional to the width of the sample face on which the crack originates and the specific energy of crack formation, whereas the work of the crack growth is proportional to the length of crack development and the specific crack growth energy. In case of the sample fracture upon testing, the crack growth length is assumed equal to the sample width. Data on the work of fracture of two samples and their geometrical dimensions at the site of the notch are used to form a system of two linear equations in two unknowns, i.e., the specific energy of crack formation and specific energy of crack growth. The determined specific energy values are then used to calculate the work of crack nucleation and work of crack growth. The use of the analytical method improves the accuracy compared to graphical - extrapolative procedures. The novelty of the method consists in using one and the same form of the notch in test samples, thus providing the same conditions of the stress-strain state for crack nucleation and growth. Moreover, specimens with different cross-section dimensions are used to eliminate the scale effects. Since the specific energy of the crack nu-cleation and specific energy of the crack growth are independent of the scale factor, they are determined only by the properties of the metal. Introduction the specific energy of crack formation and growth makes possible to assign a specific physical meaning to the fracture energy.


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