Analysis of the FSW Force Footprint and its Relationship with Process Parameters to Optimise Weld Performance and Tool Design

Hattingh, D.G.; Niekerk, T.I. van; Blignault, C.; Kruger, Grant H.; James, M.N.

doi:10.1007/bf03266414

Cited by 26 publications

(18 citation statements)

References 2 publications

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“…The incorporation of the effects of weld stress concentrations and residual stresses into a fracture mechanics life integration to predict the observed S-N curves for as-welded fatigue specimens. Secondly, a novel technique has been developed by the authors that allows on-line monitoring of a polar plot of tool forces during FS welding [11]. This gives a twin-lobed 'force footprint' that is related to the energy input into a friction stir weld and potentially provides fundamental information about the mechanisms underlying weld nugget formation.…”

Section: Welded Joints In Aluminium Alloysmentioning

confidence: 99%

Residual stresses and fatigue performance

James

Hughes²,

Chen³

et al. 2007

Engineering Failure Analysis

175

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Residual stresses are an inescapable consequence of manufacturing and fabrication processes, with magnitudes that are often a high proportion of the yield or proof strength. Despite this, their incorporation into life prediction is primarily handled through sweeping assumptions or conservative application of statistics. This can lead to highly conservative fatigue design methodologies or unforeseen failures under dynamic loading. The push from the desire for higher levels of materials performance, coupled with the pull of more sophisticated techniques for residual stress measurement, favours a reassessment of the accuracy of assumptions made about residual stresses and the modification during fatigue cycling. A viewpoint is also emerging that the fatigue performance of welded joints might be optimised through careful process control, coupled with understanding of the relative positions of, and interaction between, residual stress peaks, weld defects, hardness and microstructure. This paper will present information regarding the residual stress profiles in aluminium and steel welds obtained via synchrotron and neutron diffraction at the ESRF/ILL in Grenoble. Specimens were then subjected to specific cases of fatigue loading and the residual stress field was again measured. Difficulties associated with determining the strain-free lattice spacing will be mentioned, and the import of these data for life prediction modelling will be considered.

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Section: Welded Joints In Aluminium Alloysmentioning

confidence: 99%

Residual stresses and fatigue performance

James

Hughes²,

Chen³

et al. 2007

Engineering Failure Analysis

175

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show abstract

“…Hattingh 17 , et al analysed the force footprints to systematically study the influence of tool geometry on FSW process parameters and on weld tensile strength, in an effort to optimize the tool design thereby producing welds with 97 per cent of the parent metal strength in Al 5083-H321 alloy. Studies on the relationship between tool profiles, rotational speeds, traverse speed and the microstructure using force footprint plots were reported by Hattingh 18 , et al Arbegast…”

Section: Introductionmentioning

confidence: 99%

Role of Threaded Tool Pin Profile and Rotational Speed on Generation of Defect Free Friction Stir AA 2014 Aluminium Alloy Welds

Reddy¹,

Rao²

2016

DSJ

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Influence of threads on tool pin and rotational speeds on defect occurrence in friction stir welding (FSW) of aluminum alloy AA 2014 T6 plates has been studied. The effect of FSW forces on the evolution of mechanistic defects, caused in turn through a variation in heat generation during the process has also been examined. In case of conical tool pin, relatively lower rotational speeds resulted in unbounded zones and micro defects while high speeds caused excessive flash, thereby resulting in surface defects and voids inside the weld. The FSW joints were defect-free at moderate speeds, hinting an optimum heat generation and flow. Reaction forces on the tool pin, in the welding direction, were correlated with the defect formation. Tools equipped with a threaded conical pin profile resulted in sound welds, irrespective of the tool rotational speeds in the entire range of 400 rpm -2400 rpm. The threaded conical pin, with a relatively larger frictional area, may be contributing to higher levels of heat generation compared to a plain conical pin. Further, positive displacement of the hot plasticised material by the threads will carry away excess heat from the advancing-to-the-retracting side and simultaneously downwards, thus confining all heat within the weld zone.

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“…Further information is contained in Hattingh et al (2004), Blignault (2003Blignault ( , 2006, Lombard (2007) and Blignault et al (2008). The bending forces exerted on the tool during welding can be plotted against the angular position of the tool to provide a polar FF diagram (see Fig.…”

Section: Overview Of the Multi-axial Transducer And The Force Footprimentioning

confidence: 99%

“…The authors have termed this diagram the force footprint (FF) (Hattingh et al, 2004). This force footprint can provide information on two orthogonal forces on the tool during rotation, on their angles relative to the weld line, and on the resultant bending force.…”

Section: Introductionmentioning

confidence: 99%