OS1507 The study on the fatigue crack propagation behavior of the structures with fillet weld for load transmission type.(Second report)
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Hydraulic excavators have a lot of welded joints. Performing fillet weld is easy and economical. However fillet welded structures have unwelded area which is to be origin of fatigue crack initiation. Although the groove and fillet weld is performed to decrease unwelded area, it is difficult to perform fillet weld on both side for attachment with box structure. And also the structure with groove does not match machine costs. Because of that, high accurate evaluation method is needed. Up to date, evaluation for unwelded area has been studied in many papers and there are many standard evaluations method for crack propagation of unwelded area. However almost the all papers investigated cross fillet weld, and there is few fillet welded investigation. Moreover it is uncertain that crack propagation evaluation for actual machine condition is match or not, because many actual machines have unwelded fillet weld, and influence of weld defect for crack propagation behavior is not clear. In this study, fatigue crack growth tests were carried out on fillet welded test pieces. A test piece is modeled as to the actual machine. As the results, there was little crack initiation life. Almost the all lifetime is crack propagation. And weld defect have an effect on the direction of crack propagation.Keywords:
Fillet (mechanics)
Fillet weld
This paper discusses contemporary design procedures for fillet welds to hollow structural sections (HSS) in several prominent design codes. The structural reliability associated with the directional strength-enhancement factor contained in North American Specifications is examined, based on a set of laboratory tests on fillet-welded connections between HSS and rigid end-plates. A total of 33 connections, in which the welds had been designed to be the critical elements, were tested to failure by axial tension loading applied to the HSS members. The experimentally obtained weld strengths were compared to the predicted nominal strengths. The directional strength-enhancement factor was found to lead to unsafe strength predictions, particularly for large weld sizes. Hence, a restriction on the use of this factor for fillet welds to HSS members, in North American steel design specifications, needs to be considered. The analysis also shows that Eurocode 3 fillet weld design provisions give conservative strength predictions.
Fillet (mechanics)
Fillet weld
Eurocode
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According to the specification for Highway Bridges, the preheat temperature is determined by thickness of plate, PCM and diffusible hydrogen. The standard of the minimum preheat temperature has been determined based on the results of y-groove weld cracking test. Therefore, it is considered to require the superfluous preheat temperature, when this standard is applied to the fillet welding. However, the discussion of preheat temperature with the results of fillet weld cracking test has been still insufficient. In this paper, to discuss the standard for fillet welding, we examine the cold cracking susceptibility and the HAZ hardness distributions of the fillet welds using 50mm thick plates whose PCM ranges from 0.24% to 0.27% with various preheat temperatures. Using the present results, we propose a modified standard of the minimum preheat temperature for fillet welding.
Fillet (mechanics)
Fillet weld
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Welding sequence is one important factor which affects the residual stresses and distortions produced during welding, thus determines the welding quality and performance. In this paper, 3D numerical simulation of temperature distribution, residual stresses and distortions of the T-joint fillet weld with respect to the variation of welding sequence is presented. The finite element simulation involved thermo-mechanical analyses. Four welding sequences (WS) considered are one direction welding (WS-1), contrary direction welding (WS-2), welding from centre of one side (WS-3) and welding from centres of two sides (WS-4). The simulation results revealed that peak temperature achieved in the welding was greatly affected by the welding sequence and residual stress and angular distortion produced cannot both hold in minimum for a WS. The smallest residual stresses and the smallest angular distortions are related respectively to WS-2 and WS-4. The distributions of temperature, longitudinal and transverse residual stresses as well as angular distortions were also presented.
Fillet (mechanics)
Fillet weld
Welding joint
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In this study, in order to estimate the residual distortions of the fillet welded plates, three-dimensional finite element simulation was employed. The simulation included the uncoupled thermal and structural analyses which used the element birth and death technique to simulate the addition of weld metal to the workpiece. The accuracy of the finite element model was assessed by comparing the distortion results with experimental measurements. The effects of five different welding sequences on the residual distortion in fillet welded plates were investigated. The residual welding distortion in different positions for fillet welded plates was studied. It is obtained that by choosing the appropriate welding sequence, the maximum vertical residual distortion could be decreased significantly.
Fillet (mechanics)
Fillet weld
Distortion (music)
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Fillet (mechanics)
Fillet weld
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In the load-carrying fillet weldments, which are common in ship structures, fatigue cracks can occur at the weld root, in addition to the weld toe. In particular, fatigue cracks originating from the weld root are difficult to detect and cause a significant reduction in the fatigue strength of a weldment. Therefore, it is important to note the fatigue failure mode of load-carrying fillet weldment. In this study, a series of fatigue test was carried out for the fatigue strength evaluation of longi-web connections that are typical kinds of the load-carrying fillet weldment.
Fillet weld
Fillet (mechanics)
Fatigue limit
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The static characteristics of the combined joints using fillet weldings and high strength bolts are experimentally investigated in order to check the possibility of accumulation of the strength of each connecting element. In this study 50mm long fillet welding with 5mm size is decided as an unit of welding and M16 or M20 (S10T) high strength bolt is unit of bolt. Combinations of 0-3 units of each connecting element are selected as test specimen. Tottally 76 specimens were tested. It becomes clear that the maximum strength of the combined joints using fillet weldings and high strength bolts is 5-15% smaller than the accumulated value of the slip strength of high strength bolts and the maximum strength of fillet weldings. And the maximum design strength, of combined joints using fillet weldings and high strength bolts, which is calculated by nominal strength has enough safety.
Fillet (mechanics)
Fillet weld
Fatigue limit
High strength steel
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Hydraulic excavators have a lot of welded joints. Performing fillet weld is easy and economical. However fillet welded structures have unwelded area which is to be origin of fatigue crack initiation. Although the groove and fillet weld is performed to decrease unwelded area, it is difficult to perform fillet weld on both side for attachment with box structure. And also the structure with groove does not match machine costs. Because of that, high accurate evaluation method is needed. Up to date, evaluation for unwelded area has been studied in many papers and there are many standard evaluations method for crack propagation of unwelded area. However almost the all papers investigated cross fillet weld, and there is few fillet welded investigation. Moreover it is uncertain that crack propagation evaluation for actual machine condition is match or not, because many actual machines have unwelded fillet weld, and influence of weld defect for crack propagation behavior is not clear. In this study, fatigue crack growth tests were carried out on fillet welded test pieces. A test piece is modeled as to the actual machine. As the results, there was little crack initiation life. Almost the all lifetime is crack propagation. And weld defect have an effect on the direction of crack propagation.
Fillet (mechanics)
Fillet weld
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In this paper, tensile tests were carried out to investigate elastic-plastic behavior of fillet weld. When the fillet weld size is enough (more than 0.7 times plate thickness), specimens with base metal thickness 12mm failed in base metal. Finite element analyses assuming plane strain state are carried out. Test results can be simulated by the analyses. In the limit analysis based on the slip line fields theory, mechanism of fillet weld assumed as the shear line connecting a root to a toe of fillet weld was derived. Analytical results agree with the test results.
Fillet weld
Fillet (mechanics)
Base metal
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In the load-carrying fillet weldments, which are common in ship structures, fatigue cracks can occur at the weld root, in addition to the weld toe. In particular, fatigue cracks originating from the weld root are difficult to detect and cause a significant reduction in the fatigue strength of a weldment. Therefore, it is important to note the fatigue failure mode of load-carrying fillet weldment. In this study, a series of fatigue test was carried out for the fatigue strength evaluation of longi-web connections that are typical kinds of the load-carrying fillet weldment.
Fillet weld
Fillet (mechanics)
Fatigue limit
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