Effect of long-term thermomechanical treatment on the crack resistance of 12Kh1MF steel

1989 ◽  
Vol 25 (2) ◽  
pp. 202-208 ◽  
Author(s):  
O. N. Romaniv ◽  
A. N. Tkach ◽  
I. R. Dzioba ◽  
V. N. Simin'kovich ◽  
A. A. Islamov
Keyword(s):  
Crack Resistance ◽  
Thermomechanical Treatment ◽  
12Kh1mf Steel

Complex study of the fracture processes in materials and structures

2018 ◽  
Vol 84 (11) ◽  
pp. 46-51 ◽  
Author(s):  
N. A. Makhutov
Keyword(s):  
Fracture Mechanics ◽  
Crack Resistance ◽  
Scientific Basis ◽  
Intensity Factors ◽  
Nonlinear Fracture Mechanics ◽  
Nonlinear Fracture ◽  
Linear Fracture ◽  
Science Technology ◽  
Fracture Processes

The results of comprehensive studies of multifactor processes, mechanisms and criteria for fracture at a variation of the crack-like defect state, loading conditions and mechanical properties of structural materials carried out in the 20th - 21st centuries are presented on the basis of monographic publications and articles published in the journal “Zavodskaya Laboratoriya. Diagnostika Materialov.” Crack resistance of materials and structures has become a key problem of the material science, technology, design, manufacture and service of structures. Fracture mechanics including estimation of the stress-strain and limiting states in a cracks tip formed a scientific basis of the crack resistance analysis Stress intensity factors (linear fracture mechanics) and strain intensity factors (nonlinear fracture mechanics) are accepted as the basic criteria of those states. The basic computational relations for construction of the fracture diagrammes which link the cracks growth with conditions of a static, cyclic, long-term, dynamic loading are presented. Parameters of computational relations are put into correspondence with the features of fracture processes on nano-, micro-, meso- and macrolevels. Prospects of the research and guidelines of further studing crack resistance are discussed.

scholarly journals EVALUATION OF CHARACTERISTICS OF RESISTANCE OF PROPAGATION OF CORROSION- FATIGUE CRACKS OF LONG-TERM OPERATED DRILL PIPES

2021 ◽  
pp. 111-122
Author(s):  
О. Yu. Vytyaz ◽  
R. S. Hrabovskyi
Keyword(s):  
Fatigue Crack ◽  
Crack Resistance ◽  
Corrosion Fatigue ◽  
Fatigue Cracks ◽  
Drill String ◽  
Drilling Mud ◽  
Corrosion Fatigue Crack ◽  
Corrosion Crack Resistance ◽  
Fatigue Crack Development

The aim of the proposed article is to determine the patterns of the corrosion-fatigue cracks in long-term operational metal elements of drill strings (steel 45, 36G2S, 40HN) when drilling wells in corrosive environments (drilling fluid "Biocar", potassium polymer mud and on the air). Based on the obtained results of experimental studies, diagrams of cyclic corrosion crack resistance for the studied systems "metal - medium" were drawn. The cyclic crack resistance characteristics of long-used metals of drill string elements are determined - the values of constants (C and n) in power dependence of Paris, as well as the values of threshold and critical stress intensity factory. The influence of drilling mud of the corrosion crack resistance of the investigated metals of drill string elements was estimated quantitatively. In particular, in the environment of drilling mud "Biocar" the process of corrosion-fatigue crack development in the studied metals of the elements of drill strings is not significantly, in the range of 1-5%, differs from the development of fatigue crack on the air. Whereas in the potassium polymer drilling mud media, the rate of corrosion-fatigue cracks development in the investigated metals of the drill strings elements significantly, in the range of 15-35%, differs from the development of fatigue cracks on the air. It is established that under the influence of working loads the process of the corrosion-fatigue crack development in long-operated elements of drilling string is accelerated by more than 10% in the media of the potassium polymeric drilling mud than in the environment of drilling mud "Biocar".

scholarly journals Investigation of the relationship between the strength limit and the long time fatigue of steel reinforcements of reinforced concrete structures

2021 ◽  
pp. 28-40
Author(s):  
Denys Chernyshev ◽  
Yulia Makarenko ◽  
Tetiana Khomutetska ◽  
Valeriy Makarenko
Keyword(s):  
Reinforced Concrete ◽  
Crack Resistance ◽  
Hydrogen Content ◽  
Experimental Studies ◽  
Concrete Structures ◽  
Reinforced Concrete Structures ◽  
Reinforcing Steel ◽  
Term Operation ◽  
Strength Limit

The results of experimental studies have shown a strong effect of diffusion hydrogen on the static and cyclic parameters of crack resistance of reinforcing steel. It was found that with increasing flooding, especially when the hydrogen content exceeds 5 cm3/100g, both static strength and long-term strength (fatigue) decrease sharply. Moreover, these areas of hydrogen solution in reinforcing steel are characterized by a viscous nature of fracture, while for heavily flooded reinforcement (from 5 to 12 cm3/100g) is characterized by brittle fracture by the mechanism of microcracking in the hardened (martensite or troostite structure). The analysis of the obtained experimental results allowed to determine the optimal hydrogen content in the reinforcing steel (3…5 cm3/100g), the excess of which can cause a decrease in the crack resistance of the reinforcement during long-term operation, especially in corrosive environments. The mechanism of hydrogen influence on crack resistance of metal at static and alternating loading which consists in diffusion and dislocation movement of hydrogen in structure of a reinforcing core that as a result that causes strong flooding of steel and its embrittlement is offered. It is established that carbon and low-alloy sieves, which are characterized by ferritic-pearlitic and sorbitol structure provide high resistance, especially to long-term fatigue, and the transition to steels with a structure of martensite or tempered (transient structure of bainite) structure of bainite sharply reduces reinforcing steel, which makes it impossible to use in the manufacture of reinforcement involved in reinforced concrete structures designed for long-term operation (more than 50…60 years). Thus, the obtained diagram can be recommended to designers of reinforced concrete structures for hydraulic purposes, as it greatly facilitates the reasonable choice of reinforcement in the development of reinforced concrete structures for responsible and long-term use.

scholarly journals Assessment of the Current State of Internal Force and the Optimization of Cable Force for an Existing Long-span Pre-Stressed Concrete (PC) Cable-stayed Bridge

2017 ◽  
Vol 11 (1) ◽  
pp. 572-585 ◽  
Author(s):  
Xijun Ye ◽  
Zhuo Sun ◽  
Guoqing Huang
Keyword(s):  
Crack Resistance ◽  
Internal Force ◽  
The State ◽  
Geometric Shape ◽  
Natural Material ◽  
Cable Stayed Bridge ◽  
Cable Force ◽  
Resistance Value

Introduction: Due to the influence of load, fatigue, corrosion, natural material aging and other long-term adverse factors, the state of the internal force of a cable-stayed bridge will be changed. These long-term effects can result in the bridge not meeting specified functional requirements, and potentially resulting in structural failure. This investigation focuses on the parameter identification of a girder for a pre-stressed concrete (PC) cable-stayed bridge. Without considering the influence of cable relaxation and temperature on the girder’s geometric shape, an improved method based on the “cable force-girder’s displacement” relationship is proposed. Method: In this method, measurement variations of displacement and cable force are simultaneously obtained, enabling the use of an optimization method to identify parameters which need to be resolved. To verify the proposed method, a single pylon PC cable stayed bridge (2×160m) is selected as a case study. For the state of internal force, results from the case study bridge indicate that the crack resistance value of the girder no longer satisfies the demand of Generalized codes for design of highway bridges and culverts(JTG D60-2004,in Chinese). In order to adjust the internal force, cable force optimization was undertaken, whereby bending energy was taken as the objective function. Result: Using these results the geometric shape of the girder was restored to its initial state. The results also show that neither the crack resistance value nor the compression resistance value of the girder exceeded specified limits, and that the stress of the girder was effectively controlled.

Anisotropy of the Cyclic Crack Resistance of Aluminum Alloys After Long-Term Operation

2016 ◽  
Vol 52 (1) ◽  
pp. 83-88
Author(s):  
I. M. Andreiko ◽  
Yu. V. Holovatyuk ◽  
O. P. Ostash ◽  
O. I. Semenets’ ◽  
L. B. Koval’chuk
Keyword(s):  
Aluminum Alloys ◽  
Crack Resistance ◽  
Cyclic Crack Resistance ◽  
Term Operation

Estimation of the strength and crack resistance of the metal of railway wheels after long-term operation

2012 ◽  
Vol 47 (6) ◽  
pp. 799-806 ◽  
Author(s):  
L. I. Markashova ◽  
V. D. Poznyakov ◽  
A. A. Gaivoronskii ◽  
E. N. Berdnikova ◽  
T. A. Alekseenko
Keyword(s):  
Crack Resistance ◽  
Term Operation ◽  
Railway Wheels
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