Microstructural Characterization and Mechanical Properties of Laser Beam-Welded Dissimilar Joints between A6000 Aluminum Alloy and Galvanized Steel

This paper presents the laser beam welding process of a lap joint between galvanized steel (Z225) and an aluminum alloy (A6000) from an IPG fiber laser. Welding of steel to aluminum has become popular in the automotive industry as a means of reducing the total vehicle body mass. This approach reduces fuel consumption and, ultimately, carbon emissions. Laser welding parameters used to control heat input for the study were laser power ranging between 800 and 1200 W, as well as laser welding speeds between 2 and 4 m/min. Distinct features of the dissimilar joints were microscopically examined. The SEM-EDS technique was employed to study the intermetallic phases along the Fe-Al interface. The outcome revealed the presence of “needle-like phases” and “island-shaped phases” at high heat inputs. Traces of both Fe2Al5 and FeAl3 phases were detected. For low heat input, there was evidence of insufficient fusion. Weld width was influenced by welding parameters and increased with an increase in heat input. Mechanical properties of the joints indicated that the microhardness values of the weld joints were higher than those of both base metals. The maximum tensile shear strength obtained was 1.79 kN for a sample produced at 1200 W and 3 m/min.

Roof-mounted photovoltaic generator temperatue modeling based on common brazil roofing materials

This paper examines the performance of solar photovoltaic generators on roofs of residential buildings. The primary focus is the loss of performance due to temperature increase as function of roof material and the distance from the photovoltaic (PV) generator to the roof. A heat transfer model has been developed to predict PV module temperature, and the equations of the model were solved using the Engineering Equation Solver (EES) software. The research modeling correlates the distance of the solar generator to the roof and the roofing material with the temperature variations in the PV generator. There are many models to predict PV module temperature, but this study refines the prediction by the distance from PV module to roof and the roofing material as variables. Optimal combinations of distance and materials that minimize the heating loss in the solar generator leading to increased electrical power generation. Results show an average error of 3%–4% from the temperature predicted by the model to the temperature measured under experimental conditions in Belo Horizonte, Brazil. The minimum roof-module separation required to ensure minimal PV performance loss from heating from the roof is ∼10 cm for red ceramic and cement fiber roofs. For galvanized steel, the optimal distance is between 20 cm and 30 cm. Cement fiber shows the best predicted and measured characteristics for PV-panel roof mounting among the 3-common commercial roofs evaluated in these studies. These investigations were based on roof installations and local materials in Belo Horizonte, Brazil.

Investigation Techniques of Arson Fire in Low-Temperature Warehouses Using ED-XRF

Investigation techniques for fire prevention in low-temperature warehouses were studied using energy dispersive X-ray fluorescence (ED-XRF). In the first experiment, a sample (galvanized steel sheet plus urethane foam plus sandwich panel) was burned with 500 mL of a flammable liquid (gasoline, thinner, kerosene, and light oil)/ Then, the component change of the sample was measured. In the combustion experiment, there was a difference in the heat of combustion depending on the type of flammable liquid; however, as a result of measuring the component change of the sample with ED-XRF after combustion, the largest component change was measured in the combustion experiment with gasoline. The change was in the order of thinner, kerosene, and diesel. Using ED-XRF, it was possible to distinguish the flammable liquid used in the experiment by measuring the component change of the sample resulting from the difference in the combustion heat of the flammable liquid. A second experiment was conducted under the same conditions as the first experiment, assuming a fire brigade fire suppression condition, and the combustion time of the flammable liquid was limited to 600 s. A combustion characteristic of flammable liquids is that the temperature and heat flux reach the maximum value within 300 s after the start of combustion regardless of the type of liquid. Because the change of composition was confirmed in the order of light oil, it was possible to distinguish the flammable liquid used at the fire site using the ED-XRF measurement result.

Seismic resistance of frame-cladding buildings with a cold-formed galvanized steel profile framing

Building structural systems with light gauge steel framing technology are steadily gaining popularity due to their huge advantages over traditional technical solutions. As a result of the competitiveness inherent in LGSF technology, its application is gradually increasing in the manufacture of both bearing and nonbearing structures. At the same time, the actual absence of national standards for seismic design requires the development of programs and the implementation of research and development work to study the behavior of LGSF buildings in the conditions of seismic impact. The article touches upon the main problems of antiseismic construction of LGSF buildings and presents the results of domestic and foreign research.

Corrosion Behavior in Volcanic Soils: In Search of Candidate Materials for Thermoelectric Devices

Thermoelectric generators have emerged as an excellent solution for the energy supply of volcanic monitoring stations due to their compactness and continuous power generation. Nevertheless, in order to become a completely viable solution, it is necessary to ensure that their materials are able to resist in the acidic environment characteristic of volcanoes. Hence, the main objective of this work is to study the resistance to corrosion of six different metallic materials that are candidates for use in the heat exchangers. For this purpose, the metal probes have been buried for one year in the soil of the Teide volcano (Spain) and their corrosion behavior has been evaluated by using different techniques (OM, SEM, and XRD). The results have shown excessive corrosion damage to the copper, brass, and galvanized steel tubes. After evaluating the corrosion behavior and thermoelectric performance, AISI 304 and AISI 316 stainless steels are proposed for use as heat exchangers in thermoelectric devices in volcanic environments.

Magnetic Pulse Hybrid Joining of Polymer Composites to Metals

To lighten their vehicles, car manufacturers are inclined to substitute steel structures with aluminum alloys or composites parts. They are then faced with the constraints inherent to dissimilar (galvanized steel/aluminum) or hybrid (metal/composite) assemblies. Recent developments in magnetic pulse welding seems to offer a viable route. Very fast, this process can be robotized and generates a very localized heating system which limits the formation of intermetallic and damage the composite. Low energy consumption, without filler metal or smoke it is recognized as an environmentally friendly process. In this paper, electromagnetic pulse welding is exploited to assemble polymer composite to metals. Two techniques, a metallic insert in polymer composite or an external patch, have been tested with possible design considerations.

Gas brazing of thin-sheet galvanized steel with aluminum solders

. In this work, the first stage of experimental research was carried out to estimate the main physicochemical processes that determine the qualitative characteristics of a brazed joint made of thin sheet galvanized steel during gas brazing with aluminum solder systems. In particular, an estimation was made of the ability of spreading and wetting of aluminum solders (AlSi5, AlSi12) on the surface of thin sheet galvanized steel ( DX56D + Z of 0.4 mm thick and zinc-coated layer of 45–65 microns) at a step-by-step increase in the heating area of the base metal in the presence and absence of flux (Al-Flux 726). The aluminum alloys was heated “not directly,” but through the base metal to maximize the preservation of the anticorrosive zinc coating at the interface between the liquid solder and the base material.