Numerical and experimental investigations of mechanical properties of AW 6005-T6 Aluminium alloy butt weld joint using GMAW process

This study aimed to investigate the effect of the welding heat input on the heat affected zone (HAZ) of AW 6005-T6 aluminium alloy for a butt-welded joint using gas metal arc welding. The determination of the thermal cycles, metallography, and the resulting mechanical properties in the zone makes its possible. The study involved using a welding experiment, numerical simulation, physical simulation, and mechanical tests. The welding was carried out using the pulsed gas metal arc welding (GMAW) transfer and type J thermocouples were used to develop the thermal cycles in the HAZ. Simufact® Welding was utilized for the numerical simulation. Optical microscope was used to evaluate the microstructures and Vickers microhardness test was done along the weld cross-section. The HAZ was located on the weld cross-section with a mean hardness of 63.7 HV0.1, which is considerably lower when compared with the base metal (BM) which has a hardness of 100 HV0.1. This indicates thermal softening occurred due to the heat input to the material. There is a match in the hardness values of the Gleeble samples and the locations on the weld cross section suggested by the model showing validity of the simulation. It is important to note the fact that there is an influence of heat input into aluminum AW 6005-T6 weld joints and its mechanical properties in the design of welding process parameters for automotive parts. The welding parameters can be optimized to decrease the heat input into the weld, as this can directly affects the mechanical properties in the HAZ

Submerged arc welding process peculiarities in application for Arctic structures

The paper focuses on the submerged arc welding (SAW) process in application to structures for Arctic conditions. One of the technical challenges for modern Arctic structures is to produce high-quality welds since a weld is usually the weakest part of any structure. Welding is especially difficult for the high strength steels (HSS), which are used in structures for weight-reduction purposes. The objective of the study is to explore the usability, development possibilities and parameters of SAW process for welding of thick cold-resistant HSS plates. Meeting this objective required in-depth understanding of the welding and material science background, which includes the quality requirements of weld joints intended for Arctic service as described in various standards, properties of cold-resistant HSS and description of testing methods used to validate welding joints for low temperature conditions. The study describes experimental findings that improve understanding of SAW process of thick quenched and tempered (QT) and thermo-mechanically processed (TMCP) HSS plates. Experiments were conducted to develop SAW procedures to weld several thick (exceeding 25 mm) high strengths (580–650 MPa tensile strength) cold-resistant (intended operational temperature at least −40 ℃) steel grades. The welds were evaluated by a wide range of industrial tests: analyses of chemical, microstructural and mechanical properties; hardness tests; and cold resistance evaluation tests: the Charpy V-notch impact test and the Crack tip opening displacement (CTOD) test. Acceptable welding parameters and recommendations were developed, and the results of the experiments show that high quality welds can be obtained using heat input up to 3.5 kJ/mm. © 2022. the Author(s), licensee AIMS Press. This is an open access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0)</p

Desorption Behavior and Thermogravimetric Analysis of Bio-Hardeners

In this work, the thermal degradation and drying of bio-hardeners are investigated. Four bio-hardeners based on exudates of Senegalia senegal, Vachellia nilotica, Vachellia seyal, and Acacia Siebteriana were analyzed by FTIR and thermogravimetric analysis, and a desorption study was also conducted. The analysis by infrared spectroscopy indicates the existence of oligomers of different types all giving 5-hydroxy-2-hydroxymethylfuran and 2, 5-dihydroxymethylfuran which are then the real hardening molecules. The pyrolysis of these extracts reveals three main regions of mass loss, a first region is located between 25 degrees C and 110 degrees C reflecting the loss of water from the adhesive and the formation of some traces of volatile organic compounds such as CO2 and CO, a second zone characterized by the release of CO, CO2 and CH4 gases with peaks between 110 degrees and 798.8 degrees C. At the end of the analysis, about 22% of the initial mass remains undecomposed, this mass corresponds to the rigid segments of the bio-hardener which are not completely decomposed

Characterisation of a composite material with polyester matrix reinforced with particles from doum palm (hyphaene thebaica) fruit

The objective of this paper is to extract the hulls of Hyphaene thebaica fruit to elaborate a composite material with polyester matrix and to characterize it physically and mechanically. The first step of the process consisted of crushing, drying and then physically characterizing the hulls. The obtained results show that the average density is 766 kg/m3, the kinetic of water absorption is 40.39% and the average kinetic of humidity is 9.23%. The second step of the process consisted of crushing and sieving the hulls in order to classify them in four different sizes, and then proceeding to the manufacture of panels according to the different sizes of particles and different dosages. Another phase of characterisation has thus been achieved and the following results have been obtained: general theoretical density is 1275.86 kg/m3; average apparent density is 0.892 g/cm3, and the average density of the shells is 0.766 g/cm3. The average porosity rate obtained is 0.3%. As for the mechanical characteristics obtained by the three-point bending, the results on the average flexural modulus of elasticity (MOE) are presented as follows: 3400 ± 511 MPa for 10%–90% and size 0.5–2.5 mm, 4100± 320 MPa for 15%–85% size less than 0.5 mm; 5730± 212 MPa for 30%–70% size 0.5–2.5 mm; 6510± 211 MPa for 15%–85% size 0.5–2.5 mm; 5880± 110 MPa for 30%–70% size less than 0.5 mm. The corresponding flexural breaking strength (MOR) are respectively: 12.8± 0.2 MPa; 13.5± 0.2 MPa; 12.0± 0.5 MPa; 10.8± 0.2 MPa and 13.8± 0.3 MPa. The methods used in this work are experimental. These results allowed to deduce that the composites elaborated are particleboard type P2 and have the advantage to be used as panels useable in furniture, thermal and acoustic insulation and as structural materials. Thus, it is also possible to use it as an abrasive aggregate for sanding. All prepared particleboards had exterior and interior quality capabilities, for both working and non-working environments. It is also possible to use it as an abrasive aggregate for sanding

Influence of the Extraction Location on the Physical and Mechanical Properties of the Pseudo-Trunk Banana Fibers

The specific properties and availability of banana pseudo-trunk fibers make them a promising alternative for the development of green composites. However, the wide dispersion of their properties can hinder their use. In this study, the influence of the sampling area of the banana pseudo-trunk on the physical and mechanical properties of the fibers was evaluated. Prior to retting, the trunk was sampled longitudinally (bottom, middle and top) and transversely (periphery, intermediate and heart). Gravimetric tests were carried out and revealed variations in water absorption (347.1–517.4%), density (0.92–1.45 g.cm−3) and linear mass (25 -34tex). Tensile tests were also performed and showed a significant effect of fiber location on Young’s modulus (6.60–34.6GPa), tensile strength (91-350MPa) and elongation at the break (0.9–2.6%). Due to diameter scatter, variations of 42% were found for fibers in the same area. In a region, the physical properties increase from the periphery to the core, and the mechanical properties decrease in the same direction, except for elongation. The results of this study showed good agreement with those of other natural fiber types. However, we recommend the peripheral areas of the pseudo-trunk to extract reinforcing fibers from composites because of their low density (0.9 g.cm−3) and their high stiffness (34GPa)