Determination of fatigue crack growth parameters in welded joint of HSLA steel (original) (raw)
Related papers
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.
Fatigue Crack Growth Rate Behaviour of HSLA Steel at Varying Load Amplitudes
Procedia Structural Integrity, 2019
During their operation, modern aircraft engine components are subjected to increasingly demanding operating conditions, especially the high pressure turbine (HPT) blades. Such conditions cause these parts to undergo different types of time-dependent degradation, one of which is creep. A model using the finite element method (FEM) was developed, in order to be able to predict the creep behaviour of HPT blades. Flight data records (FDR) for a specific aircraft, provided by a commercial aviation company, were used to obtain thermal and mechanical data for three different flight cycles. In order to create the 3D model needed for the FEM analysis, a HPT blade scrap was scanned, and its chemical composition and material properties were obtained. The data that was gathered was fed into the FEM model and different simulations were run, first with a simplified 3D rectangular block shape, in order to better establish the model, and then with the real 3D mesh obtained from the blade scrap. The overall expected behaviour in terms of displacement was observed, in particular at the trailing edge of the blade. Therefore such a model can be useful in the goal of predicting turbine blade life, given a set of FDR data.
Procedia Structural Integrity, 2017
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Fatigue crack growth retardation in an HSLA steel in benign environments
The crack growth and closure were examined for fatigue loading of an HSLA steel in non-corroding media. R and DK dependent significant crack growth retardation was observed in NaOH. Presence of a passive film at high R and self repair of the film and formation of an additional oxide layer at low R could explain the retardation.
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.
Fatigue and fatigue crack growth behavior of tool steel
2008
Fatigue and fatigue crack growth (FCG) behaviors of tool steel were investigated at room temperature. Fatigue tests were performed under a load control with sinusoidal waveform of stress ratio R=0.1 at a frequency of 10Hz. The fatigue crack was identified nucleated from inclusion presents at specimen surface. The inclusion became the stress raiser and acts as the fatigue fracture origin. The fatigue limit value was observed at 396Mpa. The threshold stress intensity factor range obtained from the fatigue crack growth test was 8.06MPam 1/2 . The fatigue crack growth curve was then used to predict the fatigue life based on modified Paris equation. The predicted lives were in good agreement with the experimental results.
A fracture mechanics approach for the crack growth in welded joints with reference to bs 7910
2013
The fatigue process in welded joints is discussed and modeled. A fracture mechanics model has been proposed to describe the entire fatigue process. The model is calibrated to fit the crack growth measurements carried out on fillet welded joints. The objective is to establish a unified approach which is consistent with rules and regulation both based on the S-N approach (Eurocode 3) and applied fracture mechanics (BS 7910). Emphasis is put on how to choose growth parameters in conjunction with a fictitious initial crack size to obtain both reliable crack growth paths and predictions of the entire fatigue life. If the growth rate parameters given in BS 7910 for a single linear relationship between log da/dN and log ∆K are used in conjunction with initial crack depths near 0.015 mm the model fits both measured crack histories and S-N fatigue life estimates at various stress levels. Introduction and objectifs In the present paper the fatigue process in fillet-welded joints where cracks ...
Fatigue crack growth resistance of S960QL high strength steel
Quenched and tempered steels belong to the highest strength categories of structural steels. Their weldability is more complicated than mild steels due to the risk of cold cracking and the decrease of toughness and strength properties in heat affected zones. Since the out-standing strength properties can be primarily exploited in mobile structures where signifi-cant energy saving can be achieved with their application, cyclic loading can often occur among the various loading conditions. Due to the above mentioned reasons the analysis of fatigue crack growth is relevant in terms of this steel group. There are different prescrip-tions containing fatigue crack propagation limit curves and rules for the prediction of the crack growth. The research work aimed to determine fatigue crack propagation limit curves for S960QL and its welded joint, based on the Paris-Erdogan law. Experiments were performed on specimens cut from gas metal arc welded joints and the propagating cracks in the specimens represent the different possible locations of the real cracks in the structural elements. Fatigue crack growth tests were executed by ΔK-decreasing and con-stant load amplitude methods. The evaluation process consists of six steps, and by means of the selected values a statistical method can be proposed for determination of the fatigue crack propagation limit curves.