Browsing by Author "Raza, Muhammad Farhan"

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Application of friction stir spot welding on additive manufactured carbon fiber composite
(Trans Tech Publications Ltd, 2022) Raza, Muhammad Farhan; Yapıcı, Güney Güven; Mechanical Engineering; YAPICI, Güney Güven; Raza, Muhammad Farhan
Friction stir spot welding as a solid state processing technique is used to join dissimilar and similar metals, composites and polymers. This study illustrates the implementation of friction stir spot welding (FSSW) on additive manufactured nylon-based composites with chopped carbon fibre reinforcements. The purpose of this study is to employ FSSW technique for joining additive manufactured carbon fibre composites. The utilization of pinless tool serves a crucial function in the formation of sound welded joints. The joining process consists of two mechanisms: the piercing and melting of the sheets and the adhesive bonding during the re-solidification. As a result of the FSSW process, the joints indicate a decent mechanical performance with a lap shear failure force (LSFF) of about 250N.
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Application of interlayer friction stir spot welding on 304 stainless steel and aluminum alloy
Raza, Muhammad Farhan; Yapıcı, Güney Güven; Yapıcı, Güney Güven; Başol, Altuğ Melik; İpekoğlu, M.; Department of Mechanical Engineering
The Friction Stir Spot Welding (FSSW) is the modification of solid-state welding known as Friction Stir Welding (FSW). During the recent years, FSSW have become the most commonly used welding technique in the automotive, aerospace, and various manufacturing industries. The FSSW process is most suitable welding technique for joining such metals and alloys which cannot be welded using conventional fusion welding techniques. This welding technique can easily be employed to join dissimilar light weight alloys to reduce the weight of the components to manufacture energy efficient vehicles. Several researchers had applied this technique on various similar and dissimilar metal alloys to elaborate the dominance of this technique over other welding techniques and also to investigate the effects of processing parameters on the joint quality. Despite the superiority of this technique, keyhole that appears on the weld spot as a result of pin of the tool is a serious issue and several researchers focused on resolving this problem which results in the development of a novel technique called Interlayer Friction Stir Spot welding (IL-FSSW) which is developed in the Manufacturing Technologies Laboratory within MEMFIS at Ozyegin University. This study comprises of employment of IL-FSSW process in joining similar and dissimilar stainless steel and aluminium alloys. The weld joint fabricated by utilizing IL-FSSW technique has a magnificent surface appearance without any bulk deformation from the weld spot. The keyhole free weld joint has successfully been fabricated by utilizing this technique and this study elaborates the zero effect of the welding parameters on the surface appearance of the weld spot. The utilization of flat tip tool and intermediate layer helps to fabricate flat weld joint without keyhole in comparison of conventional FSSW techniques. The utilization of intermediate layer (IL) played an important role in improving the lap shear force (LSF) which is 1.5 times greater than the required limit of American Welding Society (AWS) standards and some of the welded samples showed 2 times higher LSF than the minimum required limit. To investigate the effect of operating parameters on the microstructures and mechanical behaviour of the weld joint Design of Experiments (DOE) based on Taguchi model L8 and L9 is developed for AISI304 stainless steel similar joint and Al6061/AISI304 dissimilar joint respectively, by using three parameters as variable by keeping other parameters constant and these three parameters as tool rotation speed, plunge depth and IL diameter. The analysis of variance (ANOVA) statistical model on the basis of lap shear force values elaborated that tool rotation speed has greatest influence on the joint strength. The mechanical behaviour of the weld joint was examined by utilizing tensile testing and Vicker's Hardness tests. Optical Microscopic analysis and micro-hardness tests performed on the nugget zone of AISI304 similar joint and Al6061/AISI304 dissimilar joint helped to discriminate the stir zone (SZ), thermomechanical affected zone (TMAZ), heat affected zone (HAZ) and base metal (BM) as micro-hardness values are different for each zone and OM differentiate these zones on the basis of average grain size (AGS). Scanning electron Microscopy (SEM) of the fracture surface for Al6061/AISI304 weld joint shows intergranular and transgranular fracture behaviour. The lap shear tensile tests showed that tool rotation speed and plunge depth have direct relation with lap shear force as with increasing tool rotation speed and plunge depth LSF is also increasing. The linear relation of plunge depth with LSF is up to certain limit because after that the thickness of spot weld starts to decrease which decrease the LSF as well. The OM analysis indicated the hook formation of intermediate layer with upper sheet and this hook formation plays important role in improving the strength of the weld joint.
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Effects of interlayer on the friction stir spot welding of stainless steel
(Elsevier, 2022-01) Raza, Muhammad Farhan; Yapıcı, Güney Güven; Mechanical Engineering; YAPICI, Güney Güven; Raza, Muhammad Farhan
Comparison of Interlayer Friction Stir Spot Welding (IL-FSSW) and conventional Friction Stir Spot Welding (FSSW) of 304 stainless steel is presented in this study. IL-FSSW is introduced as a novel spot-welding technique to avoid the keyhole formation at the weld spot. This process is employed to fabricate a joint between two stainless steel sheets. The utilization of an interlayer material prevents the occurrence of keyhole without any additional post-process treatment. In addition, the interlayer material also enhances ductility and provides a joint with a maximum lap shear load of 7 kN. The micrographs of the weld zone cross-section were recorded and it was observed that the interlayer material played a significant role in the development of the nugget zone by supporting the formation of a hook structure.