a b s t r a c tFriction spot welding is a relatively new solid-state joining process able to produce overlap joints between similar and dissimilar materials. In this study, the effect of the process parameters on the lap shear strength of AA6181-T4/Ti6Al4V single joints was investigated using full-factorial design of experiment and analyses of variance. Sound joints with lap shear strength from 4769 N to 6449 N were achieved and the influence of the main process parameters on joint performance was evaluated. Tool rotational speed was the parameter with the largest influence on the joint shear resistance, followed by its interaction with dwell time. Based on the experimental results following response surface methodology, a mathematical model to predict lap shear strength was developed using a second order polynomial function. The initial prediction results indicated that the established model could adequately estimate joint strength within the range of welding parameters being used. The model was then used to optimize welding parameters in order satisfy engineering demands.

Cutting parameters have a significant influence on the surface finish after turning, which can generate unwanted surface roughness. Thus, the parameters optimization could be a favorable strategy to improve the machined part quality. Therefore, the optimization of the cutting speed (v c), feed rate (f) and depth of cut (a p) on finish turning of 6082-T6 aluminum alloy using an uncoated carbide tool (positive rake angles and 0.4 mm tip radius) under dry and reduced quantity lubricant (RQL) conditions was performed. The input variables were combined and randomized via Box-Behnken design of experiments. The surface roughness profiles were recorded, and the roughness parameters R a and R z were measured in each combination of parameters. After optimization, the best results of R a (0.44 μm) and R z (2.73 μm) after dry machining were obtained with v c = 851 m/min, f = 0.07 mm/rev. and a p = 2 mm. Since RQL machining, the correspondent levels (v c = 403 m/min, f = 0.05 mm/rev., a p = 0.5 mm) resulted in the lowest values of R a (0.18 μm) and R z (0.96 μm). The RQL favored the chip formation in turning of AA6082-T6, minimized the occurrence of grooves (scratches), burrs and waviness on the machined surface and generated better surface quality.

This study shows experimental and numerical results of friction spot welding of AA5754 and Ti6Al4V alloys. The determination of proper welding parameters plays an important role for the weld strength. Experimental tests, conducted according to combinations of process parameters such as tool rotational speed (RS) and dwell time (DT), were investigated with response surface methodology using a 3 k factorial design of experiments. Sound joints with elevated shear strength were achieved and the influence of the main process parameters on joint strength evaluated. DT was the parameter with the largest influence on the joint shear resistance (59.9%), followed by its interaction with RS (38.1%). Higher strength was correlated to the thickness and morphology of the joint interface. A numerical model for predicting lap shear strength was successfully developed and used to optimize welding parameters in order to produce high performance joints with less energy consumption and high efficiency.

Este é um artigo publicado em acesso aberto (Open Access) sob a licença Creative Commons Attribution Non-Commercial, que permite uso, distribuição e reprodução em qualquer meio, sem restrições desde que sem fins comerciais e que o trabalho original seja corretamente citado. Effects of Heat Input and Consumable on Simple Bending Strength of Welded Joints in TMCP Steel Tubular ProfilesAbstract: The introduction of steels made by thermomechanical controlled processing (TMCP) demanded higher mechanical and metallurgical properties of the welded joints produced on them. Given these factors, the heat input is strictly limited, and to avoid any reduction in the mechanical strength of the heat affected zone (HAZ), it is required to test welding procedures close to those that will be used in the actual structure. Therefore, the aim of this study is to obtain detailed data on the mechanical efficiency of welded joints by GMAW process and different heat inputs, on square tubular profiles in TMCP steel, disposed as a column/beam weldment. So, six different heat inputs and two filler metals were used (AWS ER80S-G and AWS ER120S-G), with welds located around the profile contour. The twelve welded structures were instrumented and subjected to simple bending. Comparing welded joints produced with same heat input, and despite similar effects on the heat affected zone (HAZ), those made with consumable AWS ER120S-G have shown higher mechanical strength.Key-words: GMAW; TMCP steel; Heat input; Tubular profile; Welded joint Mechanical strength; Simple bending. IntroduçãoO processamento termomecânico controlado (TMCP) envolve o controle rigoroso da austenita durante a laminação a quente, de modo que os seus grãos se transformem em ferrita refinada ao final desta etapa. O conceito básico do TMCP é garantir e melhorar as propriedades mecânicas através do controle das mudanças microestruturais durante o processo de deformação a quente [1]. Para uma dada composição química, as propriedades mecânicas finais dependerão da taxa de resfriamento e da sequência de laminação. Para retardar, ou suprimir a recristalização da austenita deformada, são geralmente utilizados elementos químicos tais como boro, nióbio, titânio ou vanádio, usualmente em proporções variando entre 0,001% e alguns décimos por cento. Deste modo, além das bandas de deformação no seu interior, são produzidos grãos muito alongados de austenita,

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