Evaluation of the mechanical properties of friction stir lap welded joints for dissimilar aluminum alloys(AA1100 To AA6061)
In this study friction stir lap welding (FSLW) joints are made for similar and dissimilar aluminum alloys (AA1100 to AA6061-T6) sheets of 3mm thickness by varying the welding parameters, such as tool rotation speeds (1000, 1250 & 1600 rpm) and welding speeds (35, 75 & 100 mm/min) and pin length of (2.8, 5.4 & 5.7mm) with using cylindrical threaded tool pin profile. Many tests and inspections were performed such as X-Ray radiographic and tensile shear test to evaluate the weld quality and joint efficiency under different welding parameters. Microhardness and microstructure observations were carried out at the best welding parameters. The maximum tensile shear force (4.93 KN) and joint efficiency (93%) were obtained when welding process was conducted by a new technique with using friction stir diffusion welding process at the welding speed of 75 mm/min, tool rotation speed of 1250 rpm and using pin length of 2.8 mm. It was found that the Vickers hardness of the similar and dissimilar joints reached to the maximum value at stir zone and drop toward the base metals.
THE TENSILE BEHAVIOUR OF FRICTION-STIR-WELDED DISSIMILAR ALUMINIUM ALLOYS
Aluminium alloys generally have a low weldability with the traditional fusion-welding process. However, the development of Friction Stir Welding (FSW) has provided an alternative, improved way of producing aluminium joints, in a faster and more reliable manner. The FSW process has several advantages, in particular the possibility to weld dissimilar aluminium alloys. This study focuses on the tensile behaviour of dissimilar joints of AA6351-T6 alloy to AA5083-H111 alloy produced by friction stir welding. Five different tool pin profiles, such as Straight Square (SS), Tapered Square (TS), Straight Hexagon (SH), Straight Octagon (SO) and Tapered Octagon (TO), with three different welding speeds (50 mm/min, 63 mm/min, 75 mm/min) have been used to weld the joints. The effect of the pin profiles and the welding speed on the tensile properties was analyzed and it was found that the straight square pin profile with 63 mm/min produced a better tensile strength then the other tool pin profiles and welding speeds.
Experimental study on bond behavior between high-strength grout and deformed steel bars
Abstract Engineers use high-strength grout to connect precast concrete members for its low shrinkage and good fluidity. This paper designed 87 central pull-out specimens using the control variable method to investigate the influence of factors on the rebar-grout bond property such as compressive strength, steel grade, bar diameter, transverse stirrups, and bond length. The test result showed that improving grout compressive strength (85.8 MPa–122.7 MPa) cannot improve the bond strength, which was different from the previous conclusions of concrete pull-out tests. Simplified formulas were presented for calculating the characteristic values of bond strength, residual strength, peak slip, and relative slip of load-holding platform based on parameter analysis. Then, a constitutive model was proposed to predict the full-range bond stress-slip curve of high-strength grout and steel bar specimens from bearing to failure. Finally, FEA models were established to evaluate the applicability and accuracy of the constitutive model.