Characteristics of Fatigue Cracks Propagating in Different Directions of FSW Joints Made of 5754-H22 and 6082-T6 Alloys

2014 ◽  
Vol 794-796 ◽  
pp. 371-376 ◽  
Author(s):  
Ákos Meilinger ◽  
János Lukács
Keyword(s):  
Fatigue Crack ◽  
Cyclic Loading ◽  
Crack Propagation ◽  
Fatigue Crack Propagation ◽  
Welded Joints ◽  
Fatigue Cracks ◽  
Research Work ◽  
Friction Stir ◽  
Base Materials ◽  
Welding Processes

The Friction Stir Welding (FSW) is a dynamically developing version of the pressure welding processes. High-quality welded joints can be created using this process for different engineering applications (e. g. automotive parts). Nowadays, the knowing of the properties and the behaviour of the welded joints is an important direction of the investigations, especially under cyclic loading. The research work aimed to demonstrate the behaviour of the friction stir welded joints under cyclic loading conditions. Fatigue Crack Propagation (FCG) experiments were performed on 5754-H22 and 6082-T6 aluminium alloys and their friction stir welded joints. The CT type specimens were cut parallel and perpendicular to the characteristic directions of the base materials and the welded joints, and the notch locations in the specimens of welded joints were different, too. Therefore, the propagating cracks represent the possible directions of the fatigue cracks both on the base materials and on the welded joints. The results of the fatigue crack propagation tests on the welded joints clearly demonstrate the different characteristics of the thermo-mechanically affected zone (TMAZ), the heat affected zone (HAZ), and the advancing (AS) and retreating sides (RS) of the weld nugget (WN). The investigations and their results were compared with each other and with the results can be found in the literature.

Behaviour of Friction Stir Welded Joints Made out of Two Aluminium Alloys under Cyclic Loading Conditions

2014 ◽  
Vol 891-892 ◽  
pp. 1463-1468
Author(s):  
János Lukács ◽  
Ákos Meilinger
Keyword(s):  
Cyclic Loading ◽  
Welded Joints ◽  
Aluminium Alloys ◽  
Research Work ◽  
Loading Conditions ◽  
Step Method ◽  
Staircase Method ◽  
Friction Stir ◽  
Base Materials ◽  
Welding Processes

The friction stir welding (FSW) is a dynamically developing version of the pressure welding processes. Nowadays, the knowing of the properties and the behaviour of the welded joints is an important direction of the investigations, especially under cyclic loading. The research work aimed (i) to demonstrate the behaviour of the friction stir welded joints under cyclic loading conditions; (ii) to determine fatigue limit or design curves for aluminium alloys and their welded joints made by FSW process. Experiments were performed on 5754-H22 and 6082-T6 aluminium alloys and their welded joints. Both high cycle fatigue (HCF) and fatigue crack propagation (FCG) tests were executed on both base materials and their welded joints. Statistical behaviour of the base materials and welded joints was represented by the cutting of the specimens and the using of different crack paths. HCF limit curves were determined based on staircase method. FCG limit curves can be determined by own developed six step method. The investigations and their results were compared with each other and with the results can be found in the literature.

Fatigue Crack Propagation Limit Curves for S690QL and S960M High Strength Steels and their Welded Joints

2018 ◽  
Vol 1146 ◽  
pp. 44-56 ◽  
Author(s):  
János Lukács ◽  
Ádám Dobosy ◽  
Marcell Gáspár
Keyword(s):  
Fatigue Crack ◽  
Fatigue Crack Growth ◽  
Crack Propagation ◽  
Crack Growth ◽  
Fatigue Crack Propagation ◽  
Welded Joints ◽  
High Strength Steels ◽  
High Strength ◽  
Base Materials ◽  
Propagation Limit

The objective of the paper is to present the newest results of our complex research work. In order to determination and comparison of the fatigue resistance, fatigue crack growth tests were performed on different grades of S690QL quenched and tempered, and S960TM thermomechanically rolled high strength steels.15 mmand30 mmthick base materials were used for our investigations. Welded joints were made from these base materials, using gas metal arc welding with matching, overmatching, and undermatching filler metals. In the paper, the performance of the welding experiments will be presented, especially with the difficulties of the filler material selection; along with the results of the fatigue crack growth examinations executed on the base materials and its welded joints. Statistical aspects were applied both for the presenting of the possible locations of the cracks in the base materials and the welded joints and for the processing of the measured data. Furthermore, the results will be compared with each other, and the possibility of derivation of fatigue crack propagation limit curves will be referred.

Fatigue Crack Propagation Limit Curves for High Strength Steels and their Application for Engineering Critical Assessment Calculations

2014 ◽  
Vol 891-892 ◽  
pp. 563-568 ◽  
Author(s):  
János Lukács ◽  
Marcell Gaspar
Keyword(s):  
Fatigue Crack ◽  
Crack Propagation ◽  
Crack Growth ◽  
Fatigue Crack Propagation ◽  
Welded Joints ◽  
Research Work ◽  
High Strength Steels ◽  
High Strength ◽  
Critical Assessment ◽  
Propagation Limit

There are different prescriptions containing fatigue crack propagation limit curves and rules for the prediction of the crack growth. The research work aimed (i) to determine fatigue crack propagation limit curves for high strength steels and their welded joints, based on the Paris-Erdogan law; (ii) to use the determined limit curves for engineering critical assessment (ECA) calculations. Experiments were performed on different high strength steels and their 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 byΔK-decreasing and constant 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 limit curves. Engineering critical assessment calculations were performed on a welded structural element having crack like defects.

Behaviour of AlMg3 Base Material and its Friction Stir Welded Joints under Cyclic Loading Conditions

2015 ◽  
Vol 812 ◽  
pp. 155-160
Author(s):  
János Lukács ◽  
Ákos Meilinger
Keyword(s):  
Cyclic Loading ◽  
Welded Joints ◽  
Research Work ◽  
Base Material ◽  
Loading Conditions ◽  
Step Method ◽  
Staircase Method ◽  
Friction Stir ◽  
Important Direction ◽  
Welding Processes

The friction stir welding (FSW) is a dynamically developing version of the pressure welding processes. Nowadays, the knowing of the properties and the behaviour of the welded joints is an important direction of the investigations, especially under cyclic loading. The research work aimed (i) to demonstrate the behaviour of the FSW welded joints under cyclic loading conditions; (ii) to confirm the applicability of the used friction welding technology. Experiments were performed on 5754-H22 aluminium alloy and its welded joints; both high cycle fatigue (HCF) and fatigue crack propagation (FCG) tests were executed. HCF limit curves were determined based on staircase method. Statistical behaviour of the base material and the welded joints under FCG was represented by the cutting of the specimens, in other words by the using of different crack paths. FCG limit curves can be determined by own developed six step method. The investigations and their results were compared with each other and with the results can be found in the literature.

scholarly journals Mismatch effect on fatigue crack propagation limit curves of S690QL, S960QL and S960TM type base materials and their gas metal arc welded joints

2020 ◽  
Vol 65 (2) ◽  
pp. 75-86
Author(s):  
János Lukácsa ◽  
Haidar Mobarkb
Keyword(s):  
Fatigue Crack ◽  
Crack Propagation ◽  
Crack Growth ◽  
Fatigue Crack Propagation ◽  
Welded Joints ◽  
Steel Structures ◽  
High Strength ◽  
Structural Elements ◽  
Base Materials ◽  
Propagation Limit

Nowadays, one of the basic trends in the industry is the environmental impact reduction, in other words the weight decreasing of structural elements and structures, which can be approached by applying different high strength steels. In case of different steel structures, the main manufacturing and joining technology is the welding, the conventional and advanced methods of fusion and pressure welding processes. Beside the weight decreasing, the reliability and safety requirements according to steel structures have significant grown. During the welding process, the welded parts are affected with heat-effect and mechanical loads, which result in inhomogeneous welded joint. The inhomogeneity of the welded joints appears both in microstructural (local) and in geometrical (both local and global) aspects. The changes in microstructure and geometry appear in deflections (basically acceptable), or rather in failures (basically unacceptable); and these influence both the behaviour and the loadability of welded joints. Discontinuities in base materials and their welded joints have especially high danger in case of cyclic loading conditions, which are typical for different structures and structural elements (e.g. bridges, vehicles). There are different standards and prescriptions containing fatigue crack propagation limit curves and rules for the prediction of the crack growth; simple and two-stage crack growth relationships can be found in the literature, most frequently based on the Paris-Erdogan law. The paper summarizes and presents the results according to our fatigue crack growth investigations on Weldox 700E and Weldox 960E quenched and tempered (Q+T) and on Alform 960M thermomechanically treated (TM) high strength steel base materials and their gas metal arc welded joints. The mismatch effect has also been studied; matched, overmatched, undermatched and matched/overmatched (mixed-matched) welded joints were investigated. 15 mm thick plates were used for the investigations, statistical aspects were applied both for presenting the possible crack locations in the real plates, as well as for processing the measured data. Furthermore, the results will be compared with each other, and fatigue crack propagation limit curves will be derived using simple crack growth relationship.

scholarly journals 4005 Property for fatigue crack propagation of friction stir welded 2024-T3 aluminum alloy

2008 ◽  
Vol 2008.5 (0) ◽  
pp. 331-332
Author(s):  
Takao Okada ◽  
Kazuya Kuwayama ◽  
Toshiya Nakamura ◽  
Motoo Asakawa ◽  
Shigeru Machida
Keyword(s):  
Aluminum Alloy ◽  
Fatigue Crack ◽  
Crack Propagation ◽  
Fatigue Crack Propagation ◽  
Friction Stir
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