Laser beam welding is currently used in the welding of steels, aluminium alloys, thin sheets, and dissimilar materials. This high power density welding process has unique advantages of cost effectiveness, deep penetration, narrow bead and heat affected zone (HAZ) widths, and low distortion compared to other conventional welding processes. However, the metallurgical and mechanical properties of laser welds and the response of conventional materials to this new process are not yet fully established. The welding process may lead to drastic changes in the microstructure with accompanying effects on the mechanical properties and, hence, on the performance of the joint. The thermal cycles associated with laser beam welding are generally much faster than those involved in the conventional arc welding processes. This leads to the formation of a rather small weld zone that exhibits locally a high hardness in the case of C–Mn structural steels owing to the formation of martensite. It is currently difficult to determine the tensile properties (full stress–strain curves) of the laser welded joint area owing to the small size(∼V 2·3 mm) of the fusion zone. Complete information on the tensile and fracture toughness properties of the fusion zone is essential for prequalification and complete understanding of the joint performance in service, as well as for conducting a defect assessment procedure on such welded joints. Therefore, an experimental investigation into the mechanical properties of laser welded joints was carried out to establish a testing procedure using fiat micro tensile specimens (0·5 mm in thickness, 2 mm in width) for determination of the tensile properties of the weld metal and H AZ of the laser beam welds. Three similar joints, namely St 37–St 37, St 52–St 52, and austenitic–austenitic, and two dissimilar ferritic–austenitic joints were produced by CO2 laser, using 6 mm thickness plates. The mechanical properties have been examined by microhardness survey and testing of conventional transverse tensile, round tensile, and fiat microtensile specimens. The results for the micro tensile specimens were compared with those for standard round tensile specimens and this clearly showed the suitability of the microtensile specimen technique for such joints.
The effect of pin penetration depth on the mechanical properties of friction stir spot welded (FSSW) aluminum alloy 1050 and pure copper has been investigated. For a certian tool geometry, constant tool rotation speed and penetration time, the materials have been friction stir spot welded in three different penetration depths, namely 2.8 mm, 4 mm and 5 mm. Tensile shear tests, microhardness measurements and micostructural investigation have been carried out on the welded specimens in order to investigate the effect of penetration depth. 2.8 mm plunge depth has resulted in a weak joint, whereas 4 mm and 5 mm plunge depths offer acceptable tensile shear results. Presence of intermetallic phases had an influence on the tensile shear and hardness values.
This study analyzes the influence of different talc ratios on weld strength of polypropylene joined with hot plate welding process. It further determines the optimum welding parameter settings to achieve the optimum weld strength and observes the effect of process parameters, namely plate temperature and heating time on the joint quality. Process parameters were considered as variables and their effect, interactions and relative significance were investigated by utilizing design of experiment. Simultaneously, a mathematical predictive model of the weld strength was developed in terms of welding parameters. The model can predict effectively weld strength with a 95% confidence level.
The purpose of this study is to investigate the influence of the welding parameters in the hot plate welding process of polymer composites, polyamide 6 glass fiber reinforcement 15 wt.-%, by using the Taguchi method. Four welding parameters, namely the plate temperature, heating time, welding displacement and welding time, were optimized under the consideration of the joint strength. The Taguchi approach of the parameter design was used as a statistical procedure to set the optimal welding parameters. For hot plate welding of the specimens, the combination of process parameters based on three levels of the L9 orthogonal array was utilized. The signal to noise and the analysis of variance were employed to find the optimum levels and to indicate the impact of the welding parameters on joint strength by tensile tests of welded joints. It was shown that choosing 270 °C as plate temperature, 1.0 mm of weld displacement and 25 s of heating time, reveals an improved joint strength. For the optimized parameters it was verified that the welding time does not have a significant influence and the most effective factor on joint strength is the plate temperature. The weld displacement and heating time only slightly influenced the joint strength. A confirmation run was also performed to prove the effectiveness of the Taguchi method after determination of the optimum levels of the process parameters. The results showed that the joint strength was improved by about 27 % as compared to the initial welding parameters and the joint efficiency increased from 56 % to 71 %.
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