Fabrication of Tailor-Made Metallic Structures for Lightweight Applications and Mechanical Behaviour

Tailor-made metallic structures are fabricated by welding, adhesive bonding, and mechanical joining methods. Here the aim is not only to fabricate lightweight structures, but also to develop novel methods of joining. Lightweight structures are advantageous in several ways including reduction of fuel consumption and vehicle emissions. Developing novel methods of joining is advantageous due to the possibility of joining of dissimilar materials, improved mechanical performance, and microstructures. In the chapter, initially, tailor-welded blanks (TWB) are introduced, and after that, fabrication of TWBs by laser welding, friction stir welding, and friction stir additive manufacturing are elaborately discussed. Some critical issues in modeling the deformation during fabrication of TWBs is also discussed. A brief account of mechanical behavior of adhesive bonded sheets and mechanical joining are presented in the later part.

A Systematic Study on the Effects of Process Parameters on Spinning of Thin-Walled Curved Surface Parts With 2195 Al-Li Alloy Tailor Welded Blanks Produced by FSW

The manufacturing process is inevitably accompanied with the production of scraps, which leads to resource waste and environmental pollution. Recycling and remanufacturing are the most commonly used approaches for metal scraps due to their well-established advantages from economic and environmental perspectives. In this study, spinning experiments with 2195 Al-Li alloy tailor welded blanks produced by friction stir welding from metal scraps were conducted under different process parameter designs. And then the effects of various process parameters on spinning of thin-walled curved surface parts were systematically studied. The results of the corresponding experimental groups show that the roller attack angle, the spinning clearance, and the installation method of tailor welded blanks have the most significant effect on the weld torsion angle. In addition, it was found that along the longitude direction of spun parts, the surface roughnesses of the weld of spun parts were greatly improved under the roller nose radius of 10 mm, the spinning clearance of 1.0 mm, the constant linear velocity, and the installation method of tailor welded blanks (the lower surface of tailor welded blanks is spun by rollers), while the process parameters have little significant effect on the surface roughness along the latitude direction of spun parts. Furthermore, it can be concluded that the forming profiles of spun parts fitted the mandrel well under the roller nose radius of 6 mm, double rollers, the roller attack angle of 30° and 45°, spinning clearance of 1.5 mm, and the installation method of tailor welded blanks (the upper surface of tailor welded blanks is spun by rollers). The research results will provide guidance for the precise spinning of thin-walled curved surface parts with tailor welded blanks. Thereby, it is also beneficial for green manufacturing involving recycling and remanufacturing of metal scraps.

Al Alloy Tailor welded Blanks Fabrication via Friction Stir Welding: Effect of Shoulder Size

Material flow and heat generation by tool shoulder during Friction Stir Welding (FSW) significantly alters the microstructural and thermomechanical behaviour of joints. The effect of shoulder size on mechanical properties of joints has not yet been reported in the FSW of Tailor Welded Blanks (TWBs). This article reports the effect of shoulder size on joint quality in FSW of TWBs between 6.35 mm thick plates of AA2024-T3 and 2.5 mm thick plates of AA7475-T7 alloys in butt joint configuration fabricated under shoulder sizes: 18 mm, 20 mm, and 22 mm. Microstructural evaluation of FSWed joints reveals a significant increase in grain size with shoulder diameter sizes. The X-ray EDS elemental maps reveal the presence of fine second phase particles stir zone. The progressive elimination of void defect with the increase in shoulder size was observed. The tensile testing reveals the highest strength of joints fabricated under shoulder size of 18 mm. Fractographic analyses of broken tensile specimens showed the mixed mode of failure in all the weld specimens.

Improvement on Mechanical Properties of Submerged Friction Stir Joining of Dissimilar Tailor Welded Aluminum Blanks

Friction stir welding is a solid-state welding method that produces joints with superior mechanical and metallurgical properties. However, the negative effects of the thermal cycle during welding dent the mechanical performance of the weld joint. Hence, in this research study, the joining of aluminum tailor welded blanks by friction stir welding is carried out in underwater conditions by varying the welding parameters. The tensile tests revealed that the underwater welded samples showed better results when compared to the air welded samples. Maximum tensile strength of 229.83 MPa was obtained at 1000 rpm, 36 mm/min. The improved tensile strength of the underwater welded samples was credited to the suppression of the precipitation of the secondary precipitates due to the cooling action provided by the water. The lowest hardness of 72 HV was obtained at the edge of the stir zone which indicated the weakest region in the weld zone.

Thermal Finite Element Modelling of the Laser Beam Welding of Tailor Welded Blanks through an Equivalent Volumetric Heat Source

In last decades, several numerical models of the keyhole laser welding process were developed in order to simulate the joining process. Most of them are sophisticated multiphase numerical models tempting to include all the several different physical phenomena involved. However, less computationally expensive thermo-mechanical models that are capable of satisfactorily simulating the process were developed as well. Among them, a moving volumetric equivalent heat source, whose dimensions are calibrated on experimental melt pool geometries, can estimate some aspects of the process using a Finite Element Method (FEM) modelling with no need to consider fluid flows. In this work, a double-conical volumetric heat source is used to arrange a combination of two half hourglass-like shapes with different dimensions each other. This particular arrangement aims to properly assess the laser joining of a Tailor Welded Blank (TWB) even in case of butt joint between sheets of different thicknesses. Experiments of TWBs made of 22MnB5 steel sheets were conducted in both equal and different thicknesses configurations in order to validate the proposed model. The results show that the model can estimate in a satisfactory way the shape and dimensions of the fused zone in case of TWB made of sheets with different thickness.