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This study was conducted to determine the indentation behavior of thin AlSi10Mg specimens manufactured using Selective Laser Melting (SLM) in the as-built condition along with two post-treatments, namely solution heat treatment and artificial aging. Four different thicknesses of 1.0 mm, 1.5 mm, 2 mm, and 2.5 mm of SLM specimens, with the different post-treatments, underwent standardized Rockwell hardness tests using a spherical indenter to determine their hardness values and assess the impression using a stereo microscope and scanning electron microscope (SEM). The as-built specimens showed a trend of smaller indentation depths with increasing specimen thickness, and finally creased with 0.1547 mm depth at 2.5 mm. However, the post-treatments altered the behavior of the specimens to a certain degree, giving larger experimental indentation depths of 0.2204 mm, 0.1962 mm, and 0.1798 mm at 1.0 mm, 1.5 mm, and 2.5 mm thickness, respectively, after solution heat treatment. Artificial aging showed a general decrease in indentation depth with increasing specimen thickness in contrast to solution treatment, and resulted in depths of 0.1888 mm and 0.1596 mm at 1.0 mm and 2.5 mm thickness. Furthermore, a material numerical model was made using stress–strain data on ANSYS Workbench to develop a predictive model for the indentation behavior of the specimens in contrast to experimentation. Under multi-linear isotropic hardening, the Finite Element Analysis (FEA) simulation produced indentation geometry with an average accuracy of 95.4% for the artificial aging series. [ABSTRACT FROM AUTHOR]

A promising method for additive manufacturing that makes it possible to produce intricate and personalized parts is selective laser melting (SLM). However, the mechanical properties of as-corroded SLM parts are still areas of concern. This research investigates the mechanical behavior of SLM parts that are exposed to a saline environment containing a 3.5% NaCl solution for varying lengths of time. The exposure times chosen for this study were 10 days, 20 days, and 30 days. The results reveal that the tensile strength of the parts is significantly affected by the duration of exposure. Additionally, the study also examined the influence of porosity on the corrosion behavior of the parts. The analysis included studying the mass loss of the parts over time, and a regression analysis was conducted to analyze the relationship between exposure time and mass loss. In addition, the utilization of scanning electron microscopy (SEM) and X-ray photo spectroscopy (XPS) techniques yielded valuable insights into the fundamental mechanisms accountable for the observed corrosion and mechanical behavior. It was found that the presence of corrosion products (i.e., oxide layer) and pitting contributed to the degradation of the SLM parts in the saline environment. This research emphasizes the importance of considering part thickness in the design of SLM components for corrosive environments and provides insights for enhancing their performance and durability. [ABSTRACT FROM AUTHOR]

In the context of global climate change, there is a projected increase in land surface temperature (LST) worldwide, amplifying its impacts. This poses a particular concern for countries with hot climates, including the Kingdom of Bahrain as an example for the Gulf Cooperation Council countries (GCC), which are countries with a hot climate. With a surge in population growth, there is a heightened demand for land to accommodate additional residential developments, creating an opportunity to investigate the influence of land use changes on LST variations. To achieve this goal, a residential development project spanning from 2013 to 2023 was undertaken. Landsat 8 OLI/TIRS remote sensing datasets were selected for four climate seasons, each set comprising images before and after development. The analysis involved extracting the LST, Normalized Difference Vegetation Index (NDVI), and Normalized Difference Built-Up Index (NDBI) on various dates, followed by correlation and regression analyses to explore their interrelationships. The results revealed a significant increase in the mean LST during spring and autumn post-development. A consistent positive association between the LST and NDBI was observed across all seasons, strengthening after development completion. Conversely, there was a pre-development negative correlation between the LST and NDVI, shifting to a positive relationship post-development. These findings empirically support the idea that small-scale residential developments contribute to notable LST increases, primarily due to expanded impervious surfaces. These insights have the potential to inform localized adaptation strategies for small-scale residential development projects, crucial for managing the impacts of rising land surface temperatures. [ABSTRACT FROM AUTHOR]

Recent progress in additive manufacturing, also known as 3D printing, has offered several benefits, including high geometrical freedom and the ability to create bioinspired structures with intricate details. Mantis shrimp can scrape the shells of prey molluscs with its hammer-shaped stick, while beetles have highly adapted forewings that are lightweight, tough, and strong. This paper introduces a design approach for bioinspired lattice structures by mimicking the internal microstructures of a beetle's forewing, a mantis shrimp's shell, and a mantis shrimp's dactyl club, with improved mechanical properties. Finite element analysis (FEA) and experimental characterisation of 3D printed polylactic acid (PLA) samples with bioinspired structures were performed to determine their compression and impact properties. The results showed that designing a bioinspired lattice with unit cells parallel to the load direction improved quasi-static compressive performance, among other lattice structures. The gyroid honeycomb lattice design of the insect forewings and mantis shrimp dactyl clubs outperformed the gyroid honeycomb design of the mantis shrimp shell, with improvements in ultimate mechanical strength, Young's modulus, and drop weight impact. On the other hand, hybrid designs created by merging two different designs reduced bending deformation to control collapse during drop weight impact. This work holds promise for the development of bioinspired lattices employing designs with improved properties, which can have potential implications for lightweight high-performance applications. [ABSTRACT FROM AUTHOR]

This study evaluates two multiscale models to determine their ability to describe the effect of grain size (GS) on the plastic behavior of ultrafine-grained (UFG) and nanocrystalline (NC) materials. One model follows the Hall–Petch type (Model-1), while the other adopts dislocation kinematics to illustrate the grain boundary effect (Model-2). The stress–strain relation was utilized to present predictions about how various copper and nickel grain sizes affect the evolution of their plastic behavior. These predictions were compared to each other and their respective experimental databases. The copper databases stem from a well-known published paper, while the nickel databases were sourced from a research project. An analysis was conducted to evaluate each model's ability to replicate the critical value (dcrit) for the UFG to NC transition. In the case of copper, both models produce a comparable dcrit of 16 nm. Model-1 has a lower sensitivity to yield stress below this value compared to Model-2. Both models accurately describe the weakening phase of metals below dcrit, particularly Model-2. The maximum error of 11% for copper was observed in Model-1, whereas Model-2 predicted a minimum error of 0.6%. [ABSTRACT FROM AUTHOR]

An upper bound analysis of free-chip machining has been carried out, where the tool cutting and friction forces were determined from the deformation energy dissipated during the chip separation process. The method employed was based on the classical upper bound theorem, as formulated by Prager and Hodge, and Drucker, Prager, and Greenberg, and its modification by Collins, to deal with the metal forming processes involving coulomb friction. A straight shear plane and coulomb friction at the chip/tool interface were assumed and the energy required for cutting was calculated from a strain rate/velocity field that was constructed using the method proposed by Collins. Cutting forces, thrust forces, tool/chip contact lengths, and chip thickness ratios were determined for different tool rake angles and friction conditions. The theoretical results were also compared with some experimental results that are available in the published literature. The comparison between the two was not found to be satisfactory. This may be due to the non-unique nature of the machining process, as stated by Hill and demonstrated by other authors. The results calculated from the present method of "energy balance" were also found to be in agreement with those obtained by Merchant using the principle of "force balance". [ABSTRACT FROM AUTHOR]

The current work investigates the possibility of fabricating additive manufacturing products in solid-state form, from AA2011-T6 of 40 mm diameter rods as a feedstock, using an additive friction stir deposition (A-FSD) technique. The use of large diameter feedstocks, especially high-strength aluminum alloys (2XXX series), is a challenge, as it necessitates high power and the critical selection of the optimal A-FSD parameters, such as feed rate and spindle rotation speed. The study included applying a wide range of spindle rotation speeds, ranging from 400 to 1200 rpm, at three levels of feeding rates of 1, 3, and 5 mm/min. The AA2011-T6 friction stir deposited parts (FSDPs) were visually evaluated. This was followed by an examination of macrostructures through the thickness of the fabricated specimens. The characterization of microstructures was also carried out using optical microscopy and a scanning electron microscope equipped with advanced EDS analysis. Furthermore, the mechanical properties in terms of hardness and compressive strength of the AA2011-T6 base material (BM) and deposited materials were evaluated. Sound, additively manufactured products were successfully fabricated from 40 mm diameter AA2011-T6 feedstocks using the suggested deposition variables of 600 and 800 rpm spindle speeds and feeding rates of 1, 3, and 5 mm/min. The results indicated that the spindle speed and feeding rate govern the quality of the FSDPs. Furthermore, the axial load during the A-FSD process increased with increasing these parameters. In comparison to the AA2011-T6 BM, the additively deposited materials showed a refined grain structure and uniform dispersion of the fragment precipitates in their continuous multi-layers. The reduction ratio in grain size attains 71.56%, 76%, and 81.31% for the FSDPs processed at 800 rpm spindle speed and feeding rates of 1, 3 and 5 mm/min, respectively, compared to the grain size of BM. The Al2Cu and Al7Cu2Fe intermetallics are detected in the AA2011-T6 BM, and their deposited parts are in different shapes of spherical, almost spherical, irregular, and rod-like shapes. The compressive strength and hardness of the deposited parts increased with increasing spindle speed and feeding speeds. At a spindle speed of 800 rpm and a 5 mm/min feeding rate, the higher hardness and compressive strength gained were 85% and 93%, respectively, from that of the AA2011-T6 feedstock. [ABSTRACT FROM AUTHOR]

Metal-based ceramic composite laser cladding offers substantial compensations in enhancing brake disc surface characteristics. Laser cladding was utilized to combine B4C powder (10–40%) with Ni 63 powder to make Boron Carbide (B4C)/Nickel 63 composite coatings. For the subsequent experiments, the specimens were ground and polished. Bonding strength, fracture toughness, and residual stress were examined with the B4C content. The fracture morphologies were checked using a scanning electron microscope (SEM). It was observed that the bonding strength of various coatings might approach 175 MPa. Best bonding was observed when the B4C level was between 15% and 30%. The porousness of the coating continuously raised as B4C content increased. The coating's maximum permeability was 5.6% after the B4C level reached 30%. As the B4C level in the coating grew, the coating's compression resistance decreased. The bonding strength was within desirable limits, and compression resistance was consistently strong. The material bending strength increased when the B4C materials were reduced below 35%; at this level, the bending strength was highest. The bending strength was covered by the optimal range of bonding strength. Good bonding strength and mechanical characteristics were achieved when B4C content was 20% to 30%. The 20% B4C coating had the smoothest fracture morphologies and the strongest bonding strength, making it the most stable. For the estimation of total matrix deformation and corresponding coating stress on coated brake discs, Ansys software was utilized to create a static structural model. [ABSTRACT FROM AUTHOR]