Optimization of Joint Strength in Gas Metal Arc Welding by Response Surfaces Methodology

The present study is aimed at investigating the effect of six process parameters on ultimate tensile strength (UTS) of mild steel parts welded by a Gas Metal Arc Welding (GMAW) process. A Box-Behnken design was used to determine the optimum operating conditions for the GMAW process. The six welding parameters are: wire feed rate, welding voltage, welding speed, travel angle, tip-to-work distance and shielded gas flow rate. A WIN welding machine (model: Migweld350SEF) and an electrode ER70S-6 with rod size diameter of 0.8 mm were used in the experimentation. The welding specimens were randomly prepared and tested. The result at the significance level of 0.05 indicated that the optimal conditions for welding were 19 m/min of wire feed rate, 30 volts of welding voltage, 8 in/min of welding speed, 60 degree of welding angle, 7mm of tip-to-work distance, and 10 l/min of shielded gas flow rat

Evaluation of strain and stress states in the single point incremental forming process

Single point incremental forming (SPIF) is a promising manufacturing process suitable for small batch production. Furthermore, the material formability is enhanced in comparison with the conventional sheet metal forming processes, resulting from the small plastic zone and the incremental nature. Nevertheless, the further development of the SPIF process requires the full understanding of the material deformation mechanism, which is of great importance for the effective process optimization. In this study, a comprehensive finite element model has been developed to analyse the state of strain and stress in the vicinity of the contact area, where the plastic deformation increases by means of the forming tool action. The numerical model is firstly validated with experimental results from a simple truncated cone of AA7075-O aluminium alloy, namely, the forming force evolution, the final thickness and the plastic strain distributions. In order to evaluate accurately the through-thickness gradients, the blank is modelled with solid finite elements. The small contact area between the forming tool and the sheet produces a negative mean stress under the tool, postponing the ductile fracture occurrence. On the other hand, the residual stresses in both circumferential and meridional directions are positive in the inner skin of the cone and negative in the outer skin. They arise predominantly along the circumferential direction due to the geometrical restrictions in this direction.The authors would like to gratefully acknowledge the financial support from the Portuguese Foundation for Science and Technology (FCT) under project PTDC/EMS-TEC/1805/2012. The first author is also grateful to the FCT for the postdoctoral grant SFRH/BPD/101334/2014.info:eu-repo/semantics/publishedVersio

Comparative investigation of single-point and double-point incremental sheet metal forming processes

As part of a study of the capabilities of processes suitable for the rapid prototyping of sheet metal parts, two variants of incremental forming have been investigated experimentally and with finite element analysis. By examining the manufacture of similar parts by both processes some important differences between the capabilities of the two methods are highlighted. In particular, significant differences in the patterns of thickness variation and initial fracture sites are observed. © IMechE 2007