Strength in Rotary Friction Welding of Five Dissimilar Nickel-Based Superalloys

Advanced manufacturing processes improve the cost and quality of goods. Rotary friction welding is a fast, energy-efficient, and reliable joining process for metals, but new applications are hindered by large development costs for each new alloy. Each alloy set has different welding characteristics; therefore, lessons learned from a single alloy are not always broadly applicable. To establish knowledge that is applicable across multiple alloys, a family of different superalloys were welded to discover process trends that were applicable beyond a single alloy set. In this study, weld symmetry did not correlate to weld strength across alloy systems. Some alloys’ strongest welds occurred at maximum symmetry, whereas high asymmetry was associated with different alloys’ maximum strength. High feed rates, high welding forces, low energy, and low temperatures all resulted in high-strength welds across all alloy and geometry combinations. Tensile strengths greater than 95% of base-metal strength were recorded for most alloy systems.

Validation of the load-bearing capacity of the frame assembly of metal structures on the standard 2.440 series using IDEA StatiCa

The paper aims to study the actual operation of a rigid frame unit for coupling a crossbar with a column on high-strength bolts according to the standard 2.440-2 series using modern software systems of the component finite element method. Special attention was paid to the operation of nodal elements, as well as their stress-strain state. Based on the results of static calculations, the cross-sections of the elements under consideration, as well as the components of the node (plates, bolts, seams, etc.) were selected from the tables of the standard series. Subsequently, using the component finite element method serving as the basis of the IDEA StatiСa software, all the components of the node were mod-elled with respect to acting forces. The conducted calculations confirmed the suitability of the obtained node model for identifying inconsistencies in the series and modern standards. Using stresses on plates, bolt and welding forces, as well as several forms of vibration to assess the stability of compo-nents, the applicability of the node in question in the proposed configuration was evaluated. It turned out that the node failed to meet modern standards in terms of design conditions. Moreover, the serial bolts were overloaded by almost 38%, and some welds approached the limit state. When used in real conditions, this can lead to serious losses, including human lives. Recommendations are given for changing the specific configuration of the node in order to protect it from the destruction of any nature, including local buckling failure.

Intermeshing: A New Concept For Rapid Steel Erection

<p>Three-dimensional intermeshing of steel enabled by advanced digital manufacturing holds the potential to radically change how steel bridges and buildings are connected. This paper presents the concept of the first universal structural steel connection in over 100 years. The proposed Intermeshed Steel Connection (ISC) exploits recent advances in steel cutting technologies and robotics to shape member ends precisely. This vastly reduces on-site bolting and welding. Forces are transferred through common bearing surfaces at multiple contact points. The new connection is designed to accelerate structural steel deployment and offer better disassembly options. This paper introduces the geometry, manufacturing, and initial analysis of the connection approach, which holds the potential to be robust, secure, scalable, and faster to erect.</p>

In Sight of a Fillet Joint Based on Welding Force Method

Analysis of fillet-welded T-sections was carried out using the commercial finite element software ANSYS® for SM400A shipbuilding steel. To avoid the time consuming experimental technique, this model was validated with the existing experimental and numerical results. The vertical deflection, transverse shrinkage, and longitudinal residual stress were considered to validate the present model. After validating the model, the longitudinal, transverse, and normal plastic strains were collected from flange, web, and weld bead portions throughout the thickness and were averaged. These plastic strains were converted into corresponding longitudinal, transverse, and normal welding forces and were applied in an elastic model to obtain the distortions. The average welding force method was found to be very efficient in determining the distortions of welded structures. It was found that the proper distortion pattern for single-sided fillet welding can be obtained by incorporating the additional shrinkage forces from the weld bead.

Thermo-Mechanical Characterization of Friction Stir Spot Welded Sheets: Experimental and FEM Comparison between AA6060 and AA7050 Alloys

A study was carried out to evaluate how the Friction Stir Spot Welding (FSSW) process parameters affect the temperature distribution in the welding region, the welding forces and the mechanical properties of the joints. An experimental campaign was performed by means of a CNC machine tool and FSSW lap joints on both AA6060 and AA7050 aluminum alloy plates were obtained. Some thermocouples were inserted into the samples to measure the temperatures during FSSW. A set of tests was carried out by varying the process parameters, namely rotational speed, axial feed rate and plunging depth. Axial welding forces were measured during the execution of the experiments by means of a piezoelectric load cell. The mechanical properties of the joints were assessed by executing shear tests on the specimens. A comparison between the quality of the joints obtained on the two materials and a correlation between process parameters and joints properties was found. A FEM model for the simulation of the process was set up using the commercial code Deform 2D. The peculiarity of this model is a 2D approach used for the simulation of a 3D problem, in order to guarantee a very simple and practical model able to achieve results in a very short time. This solution was achieved, based on a specific external routine for the calculation of the developed thermal energy due to the friction between tool and workpiece. The collected experimental data were finally used to validate the model.

Simulative Model for the Evaluation of Thermo-Mechanical Effects in Friction Stir Spot Welding (FSSW) of Aluminum Sheets

A study was performed to evaluate how the Friction Stir Spot Welding process parameters affect both the thermal distribution in the welding region and the welding forces. An experimental campaign was performed by means of a CNC machine tool and FSSW lap joints on AA6060-T6 aluminum alloy plates having a thickness of 2+2 mm were executed. Five thermocouples were inserted into the samples at a specific distance from the specimen center. A set of tests was carried out by varying the process parameters, namely rotational speed, axial feed rate, plunging depth and dwell time. Axial welding forces were also measured during the execution of the experiments by means of a piezoelectric load cell. The experimental data collected were used to set up and to validate a simulative model of the process. In particular, a 2D FEM model was set up using the commercial code Deform 2D. A 2-dimensional FEM code was preferred in order to guarantee a very simple and practical model able to achieve results in a very short time. Since it is not possible to simulate the rotation of the tool in a 2D configuration, a specific external routine for the calculation of the developed thermal energy due to the friction between tool and workpiece was set up and implemented into the code starting from the local pressure distribution along the contact area.

The Influence of the Microstructure on the Switching Properties of Ag C, Ag-WC-C and Ag-W-C Contact Materials

The correlation between the microstructure of Ag-C, Ag-WC-C and AgWC composites and their switching properties was investigated. Two methods were used to manufacture the starting powder mixtures, namely classical milling and mechanical alloying . The arc erosion, contact resistance and welding forces of the contact materials obtained by different methods were measured using model devices. This paper presents the results achieved for the tested materials. It was found that weight loss was lower for the contacts produced by high energy milling

Friction Stir Spot Welding (FSSW) of Aluminum Sheets: Experimental and Simulative Analysis

Friction Stir welding (FSW) is a solid state joining process developed by TWI (The Welding Institute) in 1991. This technology is suitable for joining different materials even considered difficult to be welded using more traditional techniques and it is appropriate to weld materials in different configurations (such as butt, lap, circumferential, T-joint etc). Recently, starting from the FSW approach, a new technology called Friction Stir Spot Welding (FSSW) was developed. In this case, instead of moving along the weld seam, the tool only indents two overlapped parts. In some applications, this technology can be considered as a valid alternative for single point joining processes like resistance spot welding (RSW) and riveting processes. This work deals with an experimental study of the FSSW process for the lap-joining of thin aluminum sheets. In particular, an experimental campaign was performed on AA6060 T6 aluminum sheets having a thickness equal to 2 mm. The FSSW process was applied on couples of overlapped sheets by varying the tool rotational speed, and by keeping fixed the other process parameters, such as axial feed rate, indentation depth, and dwell time. Welding forces distributions were recorded during the process. Preliminary tensile tests and metallurgical analyses were also performed to evaluate the quality of the joints as function of the chosen process parameters. A numerical model of the FSSW process was developed and implemented using the commercial FEM code Deform 3D. The model parameters were set according to the experimental evidence.