Effect of tool tilt angle on strength and microstructural characteristics of friction stir welded lap joints of AA2014-T6 aluminum alloy

Friction stir welding(FSW)has been extensively adopted to fabricate aluminium alloy joints by incorporating various welding parameters that include welding speed,rotational speed,diameters of shoulder and pin and tool tilt angle.FSW parameters significantly affect the weld strength.Tool tilt angle is one of the significant process parameters among the weld parameters.The present study focused on the effect of tool tilt angle on strength of friction stir lap welding of AA2014-T6 aluminium alloy.The tool tilt angle was varied between 0°and 4°with an equal increment of 1°.Other process parameters were kept constant.Macrostructure and microstructure analysis,microhardness measurement,scanning electron micrograph,transmission electron micrograph and energy dispersive spectroscopy analysis were performed to evaluate the lap shear strength of friction stir lap welded joint.Results proved that,defect-free weld joint was obtained while using a tool tilt angle of 1°to 3°.However,sound joints were welded using a tool tilt angle of 2°,which had the maximum lap shear strength of 14.42 kN and microhardness of HV 132.The joints welded using tool tilt angles of 1°and 3°yielded inferior lap shear strength due to unbalanced material flow in the weld region during FSW.

Carbon Emission Modeling and Analysis in Manufacturing Process for Numerical Control Machine Tools

Reducing carbon emissions( CEs) is the urgent demand all over the world. In order to realize the low-carbon numerical control( NC) machining, the evaluation model of a part's manufacturing carbon emission with NC machine tools was built by considering the influences of the cutting tool geometrical parameters.The manufacturing CEs were produced by electric power,cutting tools,and cutting fluid consumed in manufacturing process. The parameters of cutting tools affected not only the CEs,but also the machining quality. Then the actual constraint models of the machine performance,machining quality were given in order to optimize the cutting parameters and achieve the low-CEs. Finally,a case was given to analyze the influences of the cutting tool angles on the manufacturing CEs. The results show that the CEs decrease as the rake angle and edge angle increase under the constraints of the machine specifications and machining quality.

3D Identification of Face and Flank in Micro-mills for Automatic Measurement of Rake Angle

In an Industry 4.0 context,to each object a"digital twin"is associated,which is a virtual counterpart of the object itself.In the case of a tool,this includes,together with its material and manufacturing information,its solid geometry.Tool geometry knowledge is fundamental to enable effective tool management,manufacturing verification,and tooling simulation.If for tool management the conventional 2D presetting is sufficient,tooling simulation and tool manufacturing verification require a complete 3D characterization.This is particularly true in the case of the microtools:the process of micro-chip formation is still a research subject.Although the 3D geometry of a tool is well established in the ISO 3002 series of standard,only recently 3D measurement of tools has been made possible by new measuring systems.Still,tool geometry verification requires a lot of human intervention.This paper aims at setting the base for the automatic analysis of point meshes scanned on the whole surface of tools,and in particular microtools.The first step for doing this is the identification of the active surfaces of the tool,that is the face and the flank plus the cutting edge.The identification of these geometric features is in general possible thanks to their specific characteristics:in particular,the cutting edge is characterized by a high curvature,and it separates the face from the flank.This paper considers cylindrical micro end-mills as a first example of an approach that can be extended to in principle any kind of tool.The cylindrical helix characterizing the cutting edge is the key geometry to be considered in the development of the specific method.Once the tool features(face,flank,and cutting edge)have been separated,of the tool angles,for instance,can be estimated.As first angle to study,the rake angle has been selected.The approach will be validated on simulated data and on real scans of micro-tools.

Ironing effect on surface integrity and fatigue behavior during ultrasonic peening drilling of Ti-6Al-4V

Imposing compressive residual stress field around a fastening hole serves as a universal method to enhance the hole fatigue strength in the aircraft assembly filed.Ultrasonic Peening Drilling(UPD)is a recently proposed hybrid hole making process,which can achieve an integration of strengthening and precision-machining with a one-shot-drilling operation.Due to the ironing effect of tool flank surface,UPD introduces large compressive residual stress filed in hole subsurface.In order to reveal the strengthening mechanism of UPD,the influence of ultrasonic vibration and tool dynamic relief angle on ironing coverage rate and its corresponding effect on surface integrity in UPD were analyzed.The experiments were conducted to verify the influence of ironing effect on surface integrity and fatigue behavior of Ti-6Al-4V hole in UPD.The results indicate that the specimen features smaller surface roughness,higher micro-hardness,plastic deformation degree and circumferential compress residual stress under higher ironing coverage rate.The fatigue life increases with the raise of ironing coverage rate,and the fatigue source site in UPD shifts from surface to subsurface comparing with that without vibration assistance.The results demonstrates that a better strengthening effect can be obtained by reasonably controlling the ironing coverage rate in UPD.