Destruction Patterns of X70 Steel Sample, Possessing Cracks of Corrosion-Mechanical Origin, under Cyclic Loading

2019 ◽  
Vol 946 ◽  
pp. 20-24 ◽  
Author(s):  
O.A. Nasibullina ◽  
A.G. Gareev
Keyword(s):  
Steel Sample ◽  
Fatigue Tests ◽  
Relaxation Processes ◽  
Corrosive Media ◽  
Mechanical Destruction ◽  
Metal Structures ◽  
Gradual Accumulation ◽  
Accumulation Of Damage ◽  
Machine Parts ◽  
Focal Zone

Most of the structures, parts of machines in the process of operation are subjected to the action of cyclically changing loads, such changes can be judged by the fatigue of the metal. In addition to the influence of mechanical stresses during the service, corrosive environment affects metal structures, machine parts, which leads to the process of gradual accumulation of damage. Corrosive media leads to a decrease in durability. The paper presents results of fatigue tests on a sample of steel X70, selected from the focal zone of destruction of the main gas pipeline. The sample under investigation had numerous cracks typical for corrosion-mechanical destruction. It is shown that with an increase in the number of loading cycles, the electrode potential of the metal decreases, which leads to a decrease in its thermodynamic stability. With the growth of the crack, there is a decrease in the potential, which is not compensated by the relaxation processes. Results of the regression analysis showed that the correlation coefficient is r = 0.99, using the three-parameter logarithmic function.

scholarly journals Experimental study on fatigue performance of Q420qD high-performance steel cross joint in complex environment

2021 ◽  
Author(s):  
Haigen Cheng ◽  
Cong Hu ◽  
Yong Jiang
Keyword(s):  
Fatigue Life ◽  
High Performance ◽  
Steel Structure ◽  
Steel Structures ◽  
Fatigue Tests ◽  
Fatigue Performance ◽  
Corrosive Media ◽  
Joint Connection ◽  
High Performance Steel ◽  
The Cross

AbstractThe steel structure under the action of alternating load for a long time is prone to fatigue failure and affects the safety of the engineering structure. For steel structures in complex environments such as corrosive media and fires, the remaining fatigue life is more difficult to predict theoretically. To this end, the article carried out fatigue tests on Q420qD high-performance steel cross joints under three different working conditions, established a 95% survival rate $$S{ - }N$$ S - N curves, and analyzed the effects of corrosive media and high fire temperatures on its fatigue performance. And refer to the current specifications to evaluate its fatigue performance. The results show that the fatigue performance of the cross joint connection is reduced under the influence of corrosive medium, and the fatigue performance of the cross joint connection is improved under the high temperature of fire. When the number of cycles is more than 200,000 times, the design curves of EN code, GBJ code, and GB code can better predict the fatigue life of cross joints without treatment, only corrosion treatment, and corrosion and fire treatment, and all have sufficient safety reserve.

scholarly journals Changing in Fatigue Life of 300 M Bainitic Steel After Laser Carburizing and Plasma Nitriding

2018 ◽  
Vol 165 ◽  
pp. 21002 ◽  
Author(s):  
Antonio J. Abdalla ◽  
Douglas Santos ◽  
Getúlio Vasconcelos ◽  
Vladimir H. Baggio-Scheid ◽  
Deivid F. Silva
Keyword(s):  
Mechanical Properties ◽  
Fatigue Life ◽  
Plasma Nitriding ◽  
Fatigue Behavior ◽  
High Strength ◽  
Tensile Tests ◽  
Steel Sample ◽  
Fatigue Tests ◽  
300M Steel ◽  
Structural Applications

In this work 300M steel samples is used. This high-strength steel is used in aeronautic and aerospace industry and other structural applications. Initially the 300 M steel sample was submitted to a heat treatment to obtain a bainític structure. It was heated at 850 °C for 30 minutes and after that, cooled at 300 °C for 60 minutes. Afterwards two types of surface treatments have been employed: (a) using low-power laser CO2 (125 W) for introducing carbon into the surface and (b) plasma nitriding at a temperature of 500° C for 3 hours. After surface treatment, the metallographic preparation was carried out and the observations with optical and electronic microscopy have been made. The analysis of the coating showed an increase in the hardness of layer formed on the surface, mainly, among the nitriding layers. The mechanical properties were analyzed using tensile and fatigue tests. The results showed that the mechanical properties in tensile tests were strongly affected by the bainitic microstructure. The steel that received the nitriding surface by plasma treatment showed better fatigue behavior. The results are very promising because the layer formed on steel surface, in addition to improving the fatigue life, still improves protection against corrosion and wear.

Cross Property Correlations for Metals Subjected to Fatigue Damage Accumulation

2002 ◽  
Author(s):  
Mahesh C. Bogarapu ◽  
Igor Sevostianov
Keyword(s):  
Electrical Resistance ◽  
Damage Accumulation ◽  
Fatigue Tests ◽  
Electric Resistance ◽  
Metal Structures ◽  
Accumulated Damage ◽  
Fatigue Damage Accumulation ◽  
Theoretical Predictions ◽  
Method Of Evaluation ◽  
Better Than

A new method of evaluation of elastic property deterioration due to accumulated damage is suggested and experimentally verified. It is based on the explicit correlations between two groups of anisotropic properties – conductivity and elasticity, recently established for porous/microcracked materials with anisotropic microstructures. An experimental study of fatigue has been done to verify the theoretical predictions. The electrical resistance and Young’s modulus are measured as functions of the number of loading cycles in the standard fatigue tests. The agreement between the theoretical predictions and the direct experimental data is better than 10% in all cases. The results allow one to use the measurement of electric resistance to estimate the damage accumulated in metal structures and decrease in the elastic modulus.

Modeling of Crack Growth in Steels

2012 ◽  
Vol 726 ◽  
pp. 233-240
Author(s):  
Jacek Jackiewicz
Keyword(s):  
Crack Propagation ◽  
Crack Growth ◽  
Damage Accumulation ◽  
Progressive Damage ◽  
Damage Development ◽  
Special Cases ◽  
Accumulation Of Damage ◽  
Machine Parts ◽  
Selection Of

The paper discusses issues related to the damage accumulation and cracking in steels. Special attention is paid to the selection of appropriate methods in the modeling of progressive damage development. In special cases, the accumulation of damage and crack propagation may lead to the brutal destruction of machine parts. In addition, some attention was drawn to the conditions that can lead to this brutal destruction.

scholarly journals Modeling of corrosion-mechanical behavior of multi-element metal structures of transport works in real-world conditions

2019 ◽  
Vol 6 (3) ◽  
Author(s):  
Valentin Chernykh
Keyword(s):  
Corrosion Damage ◽  
Corrosive Wear ◽  
Joint Effect ◽  
Euler Method ◽  
Arbitrary Cross Section ◽  
Corrosion Wear ◽  
Corrosive Media ◽  
Intermediate Point ◽  
Railway Bridges ◽  
Metal Structures

The article is part of the author’s dissertation research. Multi-element metal structures are widely used in the construction of transport structures (metal spans, trusses of railway bridges, overpasses, etc.). During operation, such structures are subjected to the joint effect of loads, temperatures, and corrosive media. In accordance with this, the task of predicting the behavior of such structures seems to be relevant. It consists in the development of effective models oriented to the calculation of the bearing capacity of structural elements subjected to corrosive wear. The article discusses the most common corrosion damage to metal multi-element structures of transport facilities, the classification of corrosion processes according to the nature of the surface destruction, the main types of metal elements and bridge structures. The main parameters characterizing the corrosive wear of metal structures were determined. Ways to account for the effect of aggressive environment on metal structures, i.e. well-known mathematical models and work, in which attention is paid to the problem of corrosion, wear modeling. The process of identifying corrosion wear models (determining unknown model coefficients) is described. The system of equations for determining the coefficients of a mathematical model of corrosive wear is given. The values of the coefficients of the models used to predict the behavior of structures, with a different choice of an intermediate point are given. A statically indefinable flat five-element truss of arbitrary cross section, part of the rods of which works in tension and part in compression is considered. For this design solves the problem of assessing durability. To solve this problem, use the corrected Euler method. The obtained numerical values of the durability of trusses of five rods, depending on the lengths of the rods.

scholarly journals Изгиб и растяжение судовых композитных элементов

2020 ◽  
Author(s):  
S.I. Koryagin ◽  
O.V. Sharkov ◽  
N.L. Velikanov
Keyword(s):  
Polymer Coating ◽  
Experimental Studies ◽  
Adhesive Layer ◽  
Polymer Coatings ◽  
Breaking Load ◽  
Strength Properties ◽  
Concentrated Force ◽  
Mechanical Destruction ◽  
Metal Structures ◽  
Reinforced Polymer

Полимерные покрытия давно и прочно завоевали свое место при изготовлении и ремонте судовых конструкций. Одной из причин, сдерживающих их более широкое применение, является отсутствие расчетных зависимостей, позволяющих рассчитать прочностные свойства композитных элементов. Для построения этих зависимостей необходимы дальнейшие экспериментальные исследования, их анализ и обобщение. В работе представлены результаты исследований прочностных свойств металлических конструкций судов с армированным полимерным покрытием при растяжении и изгибе. Экспериментально было установлено, что разрушение покрытия происходило при линейных деформациях основы на границе адгезионного слоя. При загрузке образца сосредоточенной силой определены усилия, при которых произойдет механическое разрушение композиционного образца по адгезионному слою. Построены зависимости разрушающей нагрузки от соотношения толщин основы и покрытия при растяжении и изгибе, проведено сравнение с экспериментальными результатами.Polymer coatings have long and firmly won their place in the manufacture and repair of ship structures. One of the reasons restraining their wider application is the lack of computational dependencies that allow to calculate the strength properties of composite elements. Further experimental studies, analysis and generalization are needed to construct these dependencies. The paper presents the results of studies of strength properties of metal structures of ships with reinforced polymer coating under tension and bending. It was found experimentally that the destruction of the coating occurred during linear deformations of the substrate at the boundary of the adhesive layer. When loading a sample with a concentrated force, the forces at which the mechanical destruction of the composite sample along the adhesive layer will occur are determined. The dependences of the breaking load on the ratio of the thickness of the substrate and the coating under tension and bending are constructed, a comparison with the experimental results is carried out.

scholarly journals VI. The phenomena of rupture and flow in solids

1921 ◽  
Vol 221 (582-593) ◽  
pp. 163-198 ◽  
Keyword(s):  
Mathematical Theory ◽  
Maximum Tensile Stress ◽  
Critical Value ◽  
Theory Of Elasticity ◽  
Fatigue Tests ◽  
Stress And Strain ◽  
Maximum Extension ◽  
Grooved Surface ◽  
Machine Parts ◽  
Effect Of Surface

In the course of an investigation of the effect of surface scratches on the mechanical strength of solids, some general conclusions were reached which appear to have a direct bearing on the problem of rupture, from an engineering standpoint, and also on the larger question of the nature of intermolecular cohesion. The original object of the work, which was carried out at the Royal Aircraft Estab­lishment, was the discovery of the effect of surface treatment—such as, for instance, filing, grinding or polishing—on the strength of metallic machine parts subjected to alternating or repeated loads. In the case of steel, and some other metals in common use, the results of fatigue tests indicated that the range of alternating stress which could be permanently sustained by the material was smaller than the range within which it was sensibly elastic, after being subjected to a great number of reversals. Hence it was inferred that the safe range of loading of a part, having a scratched or grooved surface of a given type, should be capable of estimation with the help of one of the two hypotheses of rupture commonly used for solids which are elastic to fracture. According to these hypotheses rupture may be expected if (a) the maximum tensile stress, ( b ) the maximum extension, exceeds a certain critical value. Moreover, as the behaviour of the materials under consideration, within the safe range of alternating stress, shows very little departure from Hooke’s law, it was thought that the necessary stress and strain calculations could be performed by means of the mathematical theory of elasticity.

Apparatus for programmed feeding of corrosive media in fatigue tests

1967 ◽  
Vol 2 (2) ◽  
pp. 120-121 ◽  
Author(s):  
A. V. Karlashov ◽  
A. D. Gnatyuk
Keyword(s):  
Fatigue Tests ◽  
Corrosive Media

Corrosive media of Orenburg gas condensate field on the condition of metal structures

1996 ◽  
Vol 32 (6) ◽  
pp. 610-614 ◽  
Author(s):  
N. A. Gafarov ◽  
A. A. Gocharov ◽  
A. S. Grintsov ◽  
V. M. Kushnarenko
Keyword(s):  
Gas Condensate ◽  
Corrosive Media ◽  
Metal Structures
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