Critical Stress Intensity Coefficient at Transverse Shear for Nanofibrobeton

2021 ◽  
pp. 41-47
Author(s):  
E.A. SADOVSKAYA ◽  
E.N. POLONINA ◽  
S.N. LEONOVICH ◽  
S.A. ZHDANOK ◽  
V.V. POTAPOV
Keyword(s):  
Stress Intensity ◽  
Transverse Shear ◽  
Critical Stress ◽  
Intensity Coefficient ◽  
Stress Intensity Coefficient

scholarly journals A PROBABLISTIC APPROACH TO EVALUATION OF THE ULTIMATE LOAD ON FLEXURAL RC ELEMENT ON CRACK LENGTH

2020 ◽  
Vol 16 (1) ◽  
pp. 98-105
Author(s):  
Sergey Solovyev
Keyword(s):  
Reinforced Concrete ◽  
Stress Intensity ◽  
Crack Length ◽  
Reliability Analysis ◽  
Critical Stress ◽  
Probabilistic Approach ◽  
Structural Elements ◽  
Intensity Coefficient ◽  
Stress Intensity Coefficient ◽  
Concrete Elements

The fracture mechanics of concrete and reinforced concrete is a promising direction in the development of methods for reinforced concrete structural elements design and inspection. At the same time, probabilistic methods of design and behavior analysis of structural elements are of particular interest. The article describes a probabilistic approach to load-bearing capacity and reliability analysis of flexural reinforced concrete elements based on the crack length criterion. The functional relationship between the critical stress intensity coefficient of concrete and the design compressive strength of concrete is given. The article presents a method for the reliability analysis of flexural reinforced concrete elements at the operational stage with limited statistical data about the critical stress intensity coefficient of concrete. The ultimate value of the failure probability (or reliability index) should be set for each object individually based on the value of the acceptable risk.

RELIABILITY ANALYSIS OF REINFORCED CONCRETE FLEXURAL ELEMENT ON CRACKING BASED ON FRACTURE MECHANICS

2020 ◽  
pp. 40-44
Author(s):  
S. A. Solov’ev ◽  
O. V. Yarygina
Keyword(s):  
Compressive Strength ◽  
Reinforced Concrete ◽  
Stress Intensity ◽  
Fracture Mechanics ◽  
Reliability Analysis ◽  
Critical Stress ◽  
Intensity Coefficient ◽  
Concrete Compressive Strength ◽  
Concrete Element ◽  
Stress Intensity Coefficient

The article describes a probabilistic approach to the reliability analysis of a flexural reinforced concrete element by the cracking criterion using the provisions of fracture mechanics. Two mathematical models of limit state are proposed for reliability analysis: with the evaluation of the critical stress intensity coefficient directly and through the design concrete compressive strength. On the basis of regression analysis, the relationship between the critical stress intensity coefficient and the design concrete compressive strength is established which can be used in the inspection of reinforced concrete structural elements. The influence of the design concrete compressive strength on the failure (cracking) probability of the flexural reinforced concrete element is analyzed. The numerical example of reliability analysis is given for the reinforced concrete beam by the criterion of cracking. It is noted that the required level of reliability should be set for each structural object individually based on the acceptable risk value using economic and non-economic losses.

Application of the ultrasound control to evaluation of the crack-resistance of low-carbon martensite steel 07Kh3GNMYuA

2021 ◽  
Vol 87 (1) ◽  
pp. 45-51
Author(s):  
R. A. Vorob’ev ◽  
V. N. Litovchenko
Keyword(s):  
Heat Treatment ◽  
Stress Intensity ◽  
Crack Resistance ◽  
Critical Stress ◽  
Mechanical Characteristics ◽  
Intensity Coefficient ◽  
Acoustic Characteristics ◽  
Stress Intensity Coefficient ◽  
The Impact

The goal of the study is to reveal the impact of change in the structural state of steel 07Kh3GNMYuA after heat treatment on the values of the critical stress intensity coefficient (K1c) obtained at a temperature of 50°C and on the velocity of ultrasound wave propagation, as well as to determine a correlation between them for rapid assessment of the crack resistance using acoustic characteristics. The mechanical characteristics of the material and the critical stress intensity coefficient K1c were obtained on the test machine «Inspekt 100 Table». The tangent method is used for determination of K1c. Three samples per K1c value were used in the experiment for a three-point bending scheme at the operating temperature T = –50°C. Acoustic parameters were measured using the echo-pulse method. The results of ultrasonic scanning of heat-strengthened samples made of steel 07Kh3GNMYuA demonstrated the possibility of non-destructive quantitative evaluation of the critical stress intensity coefficient. New data on the mechanical properties of steel 07Kh3GNMYuA and on the correlation between the velocity of longitudinal elastic waves and the values of the critical stress intensity coefficient of structures were obtained. Deviation of the calculated values of K1c obtained using acoustic measurements from the experimental values does not exceed 10%. The proposed model, which explains change in the acoustic characteristics of steel 07Kh3GNMYuA on the basis of phase changes occurring in the steel structure upon tempering, provides conducting of similar studies for other modes of heat treatment and other steel grades. The method is a low labor- and time-consuming procedure for determination of the mechanical characteristics of the products made of steel 07Kh3GNMYuA, since it does not require the manufacturing of samples and their testing. The developed procedure can be proposed for manufacturing application, as the main or additional method for evaluation of the mechanical parameters of materials after various modes of heat treatment.

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