Fatigue crack growth resistance of S960QL high strength steel (original) (raw)
Related papers
2013
There are different documents and standards containing fatigue crack propagation limit or design curves and rules for the prediction of crack growth. The research work aimed to characterise the fatigue crack propagation resistance of different steels using limit curves, based on statistical analysis of test results and fatigue crack propagation law, and to determine fatigue crack propagation limit curves for different structural steels and wide-spreading high strength steels, and their welded joints, under mode I and mixed mode I + II loading conditions. Experiments were performed on different (high strength) steels and partially their welded joints. The specimens were cut parallel and perpendicular to the characteristic directions of the materials; therefore the specimens represent the different possible locations of cracks in the base materials and welded joints. Fatigue crack growth experiments were performed by ΔK-decreasing and constant load amplitude methods. The evaluation pr...
2013
There are different documents containing fatigue crack propagation limit or design curves and rules for the prediction of crack growth. The research work aimed to characterise the fatigue crack propagation resistance of different steels using limit curves and determination of limit curves for different structural steels and high strength steels, and their welded joints, under different loading conditions, based on statistical analysis of test results and the Paris-Erdogan law. With the help of the characteristic values of threshold stress intensity factor range ( Kth), two constants of Paris-Erdogan law (C and n), and fatigue fracture toughness ( Kfc) two reliable methods – a simplified method and a two stages method – can be proposed. Our testing results were compared with the testing results can be found in the literature. The limit curves calculated by the new method represent a compromise of rational risk (not the most disadvantageous case is considered) and striving for safety ...
Lecture Notes in Mechanical Engineering, 2018
Nowadays, the environmental impact reduction and the reliability enhancement of operating structures are basic trends in the heavy industry, which can be achieved using advanced materials and technologies. Metal structures are often operated with microstructural failures (e.g. cracks), and under cyclic loading conditions. The research work has focused on the high strength steels from the world of materials, on the welding technologies from the manufacturing processes, and on the fatigue cracks from the material failures. In order to determine and compare the fatigue resistance of different high strength steels grades and their gas metal arc welded joints, fatigue crack growth tests were performed on S690QL, S960QL and S960M steel grades. Statistical aspects were applied both for the presenting of the possible locations of cracks in base materials and welded joints and for the processing of the measured data. Fatigue crack propagation limit curves were derived based on two-stage crack growth relationship, using probability methods. The determined limit curves can be applied for engineering critical assessment and structural integrity calculations.
Determining of the Fatigue Crack Growth Rate of HSLA Steel at Room Temperature
Advanced technologies and materials, 2022
Welded joint is a critical region of a welded structure and fracture mechanics analysis is inevitable in the structural integrity assessment of all welded structures. This paper shows the determining of parameters of the fatigue crack for constituents of welded joints produced of high strength low alloyed steel. The applied methodology refers to the Paris relation where the link was established between the variable load quantity or the corresponding stress intensity factor range and crack growth per cycle. Results have shown that the position of the notch and crack initiation affect the values of the stress intensity range of fatigue threshold ΔKth and parameters in the Paris' equation. This is mostly expressed when determining growth parameters of the fatigue crack in heat affected zone of HSLA steel, where different changes of growth speed of the fatigue crack clearly express differences in structure of the crack pass.
A comparison of the fatigue behavior between S355 and S690 steel grades
Journal of Constructional Steel Research, 2012
The use of higher strength steels allows the design of lighter, slenderer and simpler structures. Nevertheless, the increase of the yield strength of the steels does not correspond to a proportional increase of fatigue resistance, which makes the application of high strength steels on structures prone to fatigue, a major concern of the design. This paper presents a comparison of the fatigue behavior between the S355 mild steel and the S690 high strength steel grades, supported by an experimental program of fatigue tests of smooth specimens, performed under strain control, and fatigue crack propagation tests. Besides the cyclic elastoplastic characterization, the fatigue tests of smooth small size specimens allow the assessment of the fatigue crack initiation behavior of the materials. Results show that the S690 steel grade presents a higher resistance to fatigue crack initiation than the S355 steel. However, the resistance to fatigue crack propagation is lower for the S690 steel grade, which justifies an inverse dependence between static strength and fatigue life, for applications where fatigue crack propagation is the governing phenomenon. Consequently, the design of structural details with the S690 steel should avoid sharp notches that significantly reduce the fatigue crack initiation process.
Influence of Fatigue Crack Formation and Propagation on Reliability of Steel Members
Applied Sciences
During the years of bridge exploitation, many degradation processes and external influences attack its structure. Therefore, bridge reliability and durability is decreasing in time. On the other hand, the traffic load remains almost the same or even higher than in the past. However, bridges should not to become the limiting component of communication capacity and traffic reliability. Regarding to reliability, bridges should be assessed from the viewpoint of the Ultimate Limit States (ULS) and Serviceability Limit States (SLS). Within the ULS, cross-sections and members are verified for various types of stressing and their combinations, and also for fatigue at the same time. The cross-sectional verification, e.g., for bending stresses and fatigue, is done independently according to corresponding criteria of the ULS determined for strength verification a fatigue assessment separately. The presented article deals with the steel railway plate girder bridge with bottom member deck, in wh...
Development of a Correlation to Estimate the Fatigue Strength for Steels Based on Low-Cost Test
CT y F - Ciencia, Tecnologia y Futuro
Fatigue cracking in metallic materials occurs mainly due to the effect of cyclic stresses and their variation of magnitude over time. To evaluate the fatigue strength based on S-N curves, many tests are needed, which require a lot of time and incur high costs. For this research, several tests were conducted on samples of high-strength steels to determine their mechanical properties, chemical composition and fatigue. It was found that impact toughness Charpy V Notch , the percentage of alloying elements and the mechanical properties show a positive lineal effect in relation to the fatigue strength of the materials evaluated. Considering this behavior, a correlation to predict the fatigue strength of the steel was developed based on the Charpy impact energy, the yield strength, the ultimate strength, and the hardness of the material; thisa correlation shows a very good fit with the experimental fatigue data The main advantage of this correlation is that the estimation of fatigue stren...
Fatigue resistance of welded joints of S 690 QL high strength steels
2014
In our days the high strength steels are used increasingly greater fields, especially in welded structures. Because of this, it is important to deal with the features of the welded joints. The design of a structure is frequently done on static loading, but the welded structures often exposed with cyclic loading. From that viewpoint the welded joints has significance. In this study the low cycle and high cycle fatigue features of the welded joints of S690QL high strength steels are presented.
Development of a correlation to estimate the fatigue strength for steels based on low-cost tests
Ciencia Tecnologia y Futuro, 2010
F atigue cracking in metallic materials occurs mainly due to the effect of cyclic stresses and their variation of magnitude over time. To evaluate the fatigue strength based on S-N curves, many tests are needed, which require a lot of time and incur high costs. For this research, several tests were conducted on samples of high-strength steels to determine their mechanical properties, chemical composition and fatigue. It was found that impact toughness Charpy V Notch , the percentage of alloying elements and the mechanical properties show a positive lineal effect in relation to the fatigue strength of the materials evaluated. Considering this behavior, a correlation to predict the fatigue strength of the steel was developed based on the Charpy impact energy, the yield strength, the ultimate strength, and the hardness of the material; thisa correlation shows a very good fit with the experimental fatigue data The main advantage of this correlation is that the estimation of fatigue strength is based on very low cost tests.