Key Engineering Materials Vol. 955

Abstract: Handheld laser welding with filler material is an interesting alternative for TIG and MIG/MAG welding in aesthetic parts of small thicknesses, due to its high versatility, speed of application, low deformability and aesthetic finish. The novelty of this study lies in the analysis of the feasibility of this process for welding aluminium alloys of low thickness (2mm), commonly welded by GTAW or GMAW processes. Due to its high sensitivity to heat, laser welding of aluminium alloys is always accompanied by defects such as porosity and cracks. In this work aluminium-magnesium alloy sheets (5754 H111) were joined using fillet weld, butt weld and cornice weld configurations. The appearance, microstructure, porosity and mechanical properties were analyzed through non-destructive and destructive tests. The results of the external aspect of the samples showed a very low distortion and deformation of the material; however, the macrographic analysis showed abundant internal porosity. In the case of the fillet and cornice welding this porosity was within the applicable standard, and in the case of the butt-welded samples, tensile tests results proved the validity of the process.

Abstract: Today environmental aspects are of great importance in the sustainability of the planet, in this aspect anti-corrosive treatments facilitate the durability of metal structures. Among the most widely used anticorrosive metals is Zinc and its alloys. In the deep galvanizing process of large steel structures, tanks containing Zinc in a molten state at a temperature of 460 °C are necessary. Then, to protect elements that are too large or that need to be treated "in situ", metallization is used, which consists of projecting molten zinc wire on the metal surface that has previously been subjected to a process sandblasting (mechanical abrasion). The two main methods of metalizing are electric arc and flame. In the present work an industrial wiredrawing draft has been studied, determining the drawing force and the power required in each stage. For this purpose, linear strain hardening model vs non-linear strain hardening model that takes strain rate hardening into account has been proposed for its implementation in the analytical model of the process and finite element model (FEM) has been developed too. The use of Hall Petch equation has been allowed to get a prediction of the evolution of the grain size during the wiredrawing sequence.

Abstract: Flanges are commonly used in aircrafts to provide stiffness and support for the assembly Incremental Sheet Forming (ISF) processes have been approached to produce both stretch and shrink flanges as a low-cost alternative in the fabrication of a small number of parts and prototypes. This work analyzes stretch and shrink flanges of AA2024-T3 sheet with different geometries manufactured by Single Point Incremental Forming (SPIF). The numerical simulation using Finite Elements of the flanges allows evaluating the stress in successful and failed flanges. On the one hand, the formability of stretch flanges is usually evaluated in terms of principal strains within the Forming Limit Diagram (FLD). However, this approach does not seem to capture all the physics to explain the enhancement in formability observed in SPIF over the conventional forming. A formability analysis is performed in the field of stress triaxiality versus equivalent plastic strain, discussing the differences between successful and fractured specimens. On the other hand, for shrink flanging, the appearance of wrinkles is analyzed in terms of the compressive stresses along the flange during the incremental forming. This allows to determine a critical limit stress of winkling to predict the failure in practice for a given geometry and forming condition.

Abstract: Drilling of metal alloys is an operation that is still performed today in many industrial sectors such as aeronautics, automotive or civil engineering. This is mainly due to the high number of mechanical joints that must be made in structural elements. However, it is known that conventional drilling operations can generate defects on the machined surface mainly due to the effect of temperature on the tool and the material. For this reason, a non conventional process such as abrasive water jet machining (AWJM) is ideal for this type of operation. The decrease in temperature along the process minimizes the defects generated while keeping a high surface finish on the machined part. Therefore, this research has been carried out, where a 2 mm thick S275JR steel has been drilled by abrasive water jet. An experimental methodology has been developed to carry out the drilling. The input parameters include hydraulic pressure (P), stand of distance (SOD), abrasive flow rate (AMF) and traverse speed of the tool head (TS). In order to carry out the experiment satisfactorily, micro-drilling trials have been carried out leaving the TS parameter fixed in order to know the behavior of the material against the kinetic energy presented by the water jet equipment. These holes have been analyzed by means of the geometrical defects obtained in the form of diameter and kerf taper angle. Finally, the most relevant conclusions of the research have been developed, where it is emphasized that kerf taper (KT) angle increases drastically with the increase in SOD, giving greater results in area and with a greater amount of deformations and projections.

Abstract: Better use of material and energy resources is fundamental in any human activity. Finding better and more sustainable solutions might be inspired by nature herself. The natural evolution of life has shown a successful testing path of sustainable solutions that can be the inspiring starting point for engineering and manufacturing new directions of continuous improvement. This is the role that biomimicry can play. Evolution has been continuously testing this end, thriving strategies with better optimization in its yield. Keeping nature at the center of every design process will lead in the right direction. This is the role that biomimicry can play. Biomimicry or bioinspiration makes the most of the following methodologies: observing how evolution has achieved efficient strategies in any field of interest and realizing how to implement them or having a problem to solve and searching in Nature to find guidance or inspiration to succeed. Through a systematic review of some of the latest developments in manufacturing, focused on their capability to approach (mimic) natural textures; some applications are characterized and tested successfully to reduce energy consumption, improve efficiency, or reduce friction, among other potential improvements. In nature, actual surfaces present a functional texture. Natural evolution has developed textures showing real advantages for different functional purposes. Analyzing those natural surfaces can improve engineering surfaces’ qualitative and quantitative design. A correlation between scales, manufacturing processes, and natural strategies (surface features) will help map new product and engineering design areas of interest. This paper explores these correlations of natural surfaces with functional characteristics that make them sustainable and appropriate for inspiring research directions in manufacturing engineering surfaces. It mainly looks for contributions to efficient energy use in engineered solutions.

Abstract: DP600 steels are high strength steels used in structural elements of vehicles. However, they can be used in other sectors, but this requires a study in different working conditions, with the help of tools that facilitate the realization of predictions about the mechanical properties of these materials.The "Design Expert" software was used during this research. In it, the combinable input variables are introduced, which in this case are only the size of the pin and the folding angle of the sheet, so that employing simple combinatorial operations tells us how many and which experiments we will have to perform to cover the different possibilities.Simulations have been carried out with the Deform-2D software, applying the finite element method, to know in advance what is going to be the behavior of the metal sheets interacting with the rotating pin, in processes like drawing.

Abstract: The increased use of plastics has become a major environmental problem, especially during this pandemic. Plastics have generated many problems, particularly waste disposal, which made the researchers aimed to develop biodegradable plastic through fruit waste material, avocado seeds. From a total of 3 kilograms of the avocado seed, starch was extracted through the traditional starch extraction method. There were three groups with the same ingredients but differing in their concentration; the relationship between the proportion of the ingredients and their respective differences was seen by using ANOVA and Post hoc tests. The samples have undergone a tensile strength test following ASTM D882. From the results, the best experimental group was the group with 40 grams of starch, 20 grams of polyvinyl alcohol, and 10 grams of used cooking oil; however, it is different from the biodegradable plastic bags used as the control group. It could be deduced that it is possible to make biodegradable plastic out of Avocado seed starch that is biodegradable, water-soluble, and non-toxic. However, further analysis may be conducted to provide physical features as commercial plastics.

Abstract: In this work, cellulose hemp fibers were extracted from agricultural waste via a pretreatment process using an alkaline solution followed by a bleaching process. The high-pressure homogenization by microfluidizer was conducted to defibrillate hemp fibers into cellulose nanofibers (CNFs). The obtained products in each step of the process, including hemp raw fibers, alkaline-treated fibers, bleached fibers, and CNFs, were analyzed in terms of morphology, chemical composition, chemical structure, crystallinity, and thermal stability. SEM images revealed the successful extraction and decreased diameter with the uniform nanofiber shape. The disappearance of lignin and hemicellulose-related peaks in FTIR analysis, a decrease in their content in the chemical composition results, and an increase in the thermal stability of purified fibers indicated the success of the chemical treatment in removing noncellulosic components.

Abstract: This paper studies the effect of both perlite and pozzolan powders as cement substituents. First, it addresses the mechanical properties of pozzolanic mortar in the short term, i.e., with a schedule of 7, 14 and 28 days. Next, in order to extend the analysis related to the porosity of the designed mortars, the water absorption is studied. The provided results indicated that the compressive strengths of the pozzolanic mortars were lower than those of the reference mortar. However, among the tested pozzolanic mortars, those containing 10% of perlite displayed superior strengths. Additionally, while the water absorption values for pozzolanic mortars were higher than those of the reference mortar, the inclusion of 10% of perlite in the mortar resulted in lower water absorption compared to the other pozzolanic mortars.

Abstract: Cellulosic fibers are one of the trend studies being conducted from the recent research due to their cost-effectiveness and abundance as biomass waste products from different plantations. The study aims to fabricate a dew extractor machine and analyze and characterize fibers based on their physical, mechanical, and chemical properties. The machine achieved the required torque, which is 370.645 N.m, and a speed of 28.82 rpm for the initial process for the sources of fiber by using a chain drive. Among the three fibers, the banana shows greater tensile strength with 221.225 MPa - 418.59 7MPa for untreated and 191.376 MPa – 715.428 MPa for treated. Napier has the smallest value of tensile strength with 77.944 MPa – 146.731 MPa for untreated and 76.048 MPa – 287.689 MPa for treated. The chemical properties of the fibers were analyzed using Fourier Transform Infrared Spectroscopy shows all three fibers have a similar single-, triple- and double-bond, namely a secondary aliphatic alcohol, alkene, and a non-conjugated alkene functional group. It can be concluded that treated fibers can withstand more stress, stretch even more, and therefore are more elastic than untreated fibers.