Papers by Keyword: Sustainability

Abstract: The condition of a dynamic machine (equipment) can be estimated at the current level, by measuring the vibration levels. Each component of a machine produces a vibration with one or more specific frequencies. Knowing the components of the spectrum of frequencies of the global vibration, it is possible to determine which of the components of the moving assembly the problem occurred. Thus, by measuring the vibration, a multitude of defects can be detected, for a wide variety of dynamic machines. Unlike other diagnostic devices, spectrum analyzers have the widest use in the evaluation of vibrations and specific stresses on fixed structures or on rotor blades. Other experiments evaluate the natural frequencies of the rotors, the influence of the cavity of the rotor-stator interaction. Model or prototype studies establish the influence of pressure pulsations at partial load for radial axial turbines [5]. In the work, the vibrational behavior of a Kaplan hydraulic turbine with 6 rotor blades of high power (P=200MW, Dn=9.5m), was analyzed when mechanical failures (wear) appeared after several years of operation, the graphs being taken from the diagnostic system of the studied hydrogen generator.

Abstract: Plastic pollution remains a critical environmental and public health challenge. Bioplastics have emerged as a promising alternative to reduce the adverse impacts of petroleum-based plastics. Among renewable biomass sources, macroalgae, particularly seaweeds, stand out due to their high biomass yields, cost-effectiveness, and ease of cultivation. For an island nation like Sri Lanka, seaweed-based bioplastics present a unique opportunity to advance sustainability while strengthening the economy. Sri Lanka already has an established seaweed farming industry, primarily exporting dried seaweeds, which could be expanded into value-added bioplastic production. Several studies project a significant global increase in bioplastic demand by 2028, underscoring the potential market. With its year-round cultivation potential, rich marine biodiversity, and proximity to major Asian markets, Sri Lanka is well-positioned to become a competitive player in the regional bioplastics industry. This review examines bioplastic production from seaweeds, with a focus on its applicability, benefits, and strategic relevance for Sri Lanka as a developing country.

Abstract: The disposal of waste marble is a severe concern worldwide, as it is non-biodegradable, leading to dumping issues and environmental pollution. An economically feasible solution to this problem is utilizing it in concrete production that will make the environment green, make the construction industry sustainable, fulfil the high demand for concrete, and convert waste into valuable materials. This study investigates experimentally the feasibility of using waste marble as a partial replacement for coarse aggregate in concrete production. The research focused on preparing M30-grade concrete mixes with varying percentages of waste marble aggregate to replace normal coarse aggregate, ranging from 20% to 100%. The study evaluated the fresh properties, compressive strength, and durability of concrete made with waste marble aggregate. The research findings indicate that the optimal outcome was achieved with a 60% replacement of natural coarse aggregate with waste marble coarse aggregate in concrete production. The workability increases as the percentage replacement of coarse aggregate by waste marble aggregate increases, as found by the slump value test. The compressive strength of the mix having 60% replacement of natural aggregate by waste marble aggregate concrete (WMAC-60) is 10.0%, 11.8% and 12.14, higher than conventional concrete tested at 7, 28, and 56 days, respectively. The durability of WMAC-60 is also improved, with 7.14% and 13% lower chloride ion pass than conventional concrete at 28 and 180 days of a rapid chloride penetration test, respectively. A 6.1% and 6.67% higher resistivity was found in WMAC-60 compared to the conventional concrete at 28 and 180 days of electrical resistivity test, respectively. In brief, waste marble aggregate is an eco-friendly and sustainable method that reduces concrete costs without compromising concrete performance.

Abstract: This study evaluates the effect of temperature variations on the corrosion rates of A106 Grade B steel using dynamic polarization and weight-loss methods. Carbon steel samples were immersed in a 1-molecular-concentration hydrochloric acid electrolyte solution at different temperatures ranging from 25 to 55°C, with or without inhibitors at different concentrations, for a specified period. In this study, nano silica was synthesized in the laboratory using a Sol-gel process to serve as an environmentally friendly corrosion inhibitor derived from natural sand (Najaf, Iraq). The results demonstrate the effectiveness of the inhibitor, producing favorable corrosion rates even at high temperatures in its presence, while corrosion rates decreased in the absence of added inhibitor concentrations (400–1000 ppm). The results and statistical data were analyzed using Tafel and CR plots, Arrhenius analysis (ln (CR) vs. 1/T), and percentage inhibition ratios. Corrosion rates, current densities, and Tafel constants (CR, icorr., βc, βa) were determined during polarization, while the weights of the inhibitor-treated and non-inhibited samples were evaluated during weight loss studies. Tests (XRD, FTIR, AFM, TGA/TDS, and SEM) demonstrated the achievement of the work goal of developing a protective silicate layer of silica (SiO₂) nanoparticles, which provided effective and durable protection of the target metal surface samples from corrosion, especially under temperature fluctuations.

Abstract: Cleaner melt transfer is critical to the broader use of recycled aluminium alloys in high-end structural casting applications, where oxide bifilms and intermetallic inclusions, such as Fe-containing intermetallics, can significantly affect the casting's mechanical properties. In counter-gravity low- and high-pressure casting, the launder system must not only promote the sedimentation of inclusions but also deliver a stable, cleaner melt to the crucible. Prior research showed that 15° double baffles in the mid-section of the sedimentation launder at a flow rate of 100 kg·h^-1 provide high efficiency. The present work investigates the influence of baffle design at the launder-crucible interface, where the melt enters the crucible before casting. Fluid dynamic simulations were carried out at a 100 kg·h^-1 flow rate for three inlet configurations: (i) full baffle; (ii) lifted baffle; and (iii) split baffle. Inclusions of various densities and diameters were tracked. Results indicate that the full baffle, while beneficial as a benchmark and efficient, is impractical because it generates fresh oxide surfaces. The lifted baffle provided the most effective reduction in inclusions, like the full baffle setup, enhancing sedimentation and suppressing entrainment, while the split baffle showed intermediate behaviour. Moreover, the lifted configuration promoted centrifugal flow (at lower velocities, it still made a partial contribution) within the crucible, directing inclusions towards the crucible wall and the stagnation-velocity zone, and enabling the crucible itself to act as a final sedimentation stage before the counter-gravity pump extracts the melt. These results demonstrate that combining mid-launder optimisation with crucible inlet baffle design enables cleaner, more automated melt delivery, thereby strengthening the use of recycled aluminium alloys in structural casting applications.

Abstract: The decarbonization of the aluminium industry requires a transition from fossil fuels to sustainable energy carriers. This study investigates the substitution of natural gas (NG) with hydrogen (H₂) in reverberatory furnaces, analyzing the impact on melt quality, furnace integrity and exhaust emissions. Experimental investigations were conducted in a specifically designed furnace setup combining electrical heating with a burner system capable of operating with variable fuel blends ranging from pure natural gas to 100 vol.-% hydrogen. The results demonstrate that the hydrogen content in the aluminium melt depends on the atmospheric conditions — water vapour content in the atmosphere — during the melting and heating phases. In contrast, the holding phase exhibited a quasi-static behavior with negligible further hydrogen uptake, due to the isothermal process control. Numerical simulations (CFD) revealed that admixture rate exceeding 80 vol.-% H₂ leads to significantly higher adiabatic flame temperatures. This results in the formation of local hotspots on the furnace walls and requiring the use of high-performance refractory linings. Furthermore, these thermal conditions correlated with a major increase in NO_x emissions, despite a successful reduction in CO₂ output. Considering the material quality, X-ray computed tomography (XCT) analysis indicated a marginal increase in volume porosity with higher hydrogen fractions. However, tensile testing confirmed that this porosity did not compromise the mechanical performance, as yield strength and ultimate tensile strength remained unaffected across all fuel mixtures. The study concludes that standard degassing procedures are sufficient to reduce the increased initial hydrogen load, showing that hydrogen combustion for secondary aluminium production is feasible.

Abstract: The increasing use of fibre-reinforced composites raises critical issues related to sustainability and end-of-life management, particularly for thermoset-based systems. In this work, a non-conventional thermo-mechanical recycling strategy is proposed for hemp/carbon hybrid laminates, aiming at the recovery and reuse of intact reinforcement plies without destructive fibre-matrix separation. Full carbon, full hemp, and two hybrid laminate configurations with different stacking sequences were manufactured, recycled through controlled thermo-mechanical disassembly, and reprocessed into new laminates. The flexural and interlaminar shear behaviour of virgin and recycled materials was investigated to assess the influence of the recycling process on mechanical performance.

Abstract: Climate change is progressing rapidly, posing severe risks to the environment and making sustainability and circularity key challenges for future industrial development. Greenhouse gas emissions are largely driven by human activities within industrialized societies, requiring adaptation at individual, societal, and industrial levels. Metal forming technologies can contribute significantly to this transformation by improving material efficiency, process efficiency, product efficiency, and circularity. Material efficiency is particularly important, as material production accounts for the largest share of industrial emissions. Process efficiency offers a high leverage effect, due to the large production volumes in forming process chains, while product efficiency reduces energy consumption during usage and enhances the performance of energy generation systems. Circularity supports sustainability by extending material lifecycles through reuse and recycling, thereby avoiding energy-intensive primary production. This paper presents an overview of exemplary sustainability contributions in metal forming process chains. For open-die forging, it can, for example, be shown, that digital twins, virtual reality–based operator training and real-time assistance systems are measures to improve material and process efficiency. A circularity approach for open-die forging is presented, with a remanufacturing concept for large shafts based on re-forging end-of-life components, in order to heal fatigue-related damage by forming. Increased material, process and product efficiency is demonstrated by a use case study of forging hollow rotor shafts for wind turbines. Whereas, the hollow-forging allows for weight reduction in the rotor component and thus enables higher power density of the generator, thinner tower designs and reduced logistic costs. Additionally, the use of an innovative air-hardening ductile (AHD) steel can eliminate the energy-intensive heat treatment in the process chain.

Abstract: The reshaping approach is widely considered a virtuous strategy in line with the pillars of the Circular Economy. According to this approach, End-of-Life (EoL) components are subjected to a second forming process to achieve a new functional geometry. However, EoL parts often exhibit a non-uniform thickness distribution and work-hardened zones resulting from the primary manufacturing step, which makes the design of the reshaping step not trivial. Beyond the standard objectives like avoiding fracture and minimizing springback during the reshaping operations, one of the most concerning aspects is the complete removal of the geometrical features coming from the initial forming process. Flexibility and versatility of the forming process are unavoidable requirements to make the reshaping successful. Therefore, three different reshaping routes are numerically investigated in the present work: (i) reshaping by hydroforming (RH) at room temperature; (ii) reshaping by gas forming (RGF) at hot temperature; (iii) a hybrid approach, based on the combination of an intermediate deformation step via Single Point Incremental Forming followed by sheet hydroforming (RHA). The three routes share the same EoL, characterized by the presence of a deep-drawn square feature. Comparing the three routes, in terms of final shape and thinning distribution, with a reference case study (represented by the sole hydroforming process carried out on an undeformed flat blank) allowed to conclude that the feature removal and a non-severe thinning could not be achieved simultaneously: in fact, while RGF and RHA ensure a more evident suppression of the pre-existing feature, they simultaneously induce a more pronounced and localized thinning compared to the RH route.

Abstract: Electroplasticity in sheet metal forming is a relatively recent method that involves applying an electric current to metal sheets during or before the forming process. Existing research on Electro-Assisted (EA) forming primarily focused on material characterization; few studies have investigated the effect of electropulsing on loads, power, and energy consumption during sheet metal forming, and no studies have explored the reshaping of previously formed titanium sheets after the Electro-pulsed treatment (EPT). This research aims to bridge some of these gaps of knowledge by applying two different electropulsing treatments, varying in current density, to square Ti6Al4V specimens prior to shaping and reshaping. performed using dies and counter dies having different geometries. Load, power, and energy consumption data were measured to assess the benefits of EPT compared to an untreated specimen serving as a reference. The findings suggest that EPT can significantly reduce the energy consumption and forces required for both shaping and reshaping of titanium components, extending their useful life and reducing the need for remelting. The study highlights the potential of EPT as a sustainable solution for reducing the environmental impact of titanium sheet disposal and recycling, improving material efficiency, and optimizing industrial forming processes.