Key Engineering Materials Vol. 1042

Abstract: The sugar palm flour industry generates substantial solid waste, contributing to environmental pollution. The utilization of waste pellets as raw material for pyrolysis for bio-oil production has not been widely studied. Pelletization aids handling and improves pyrolysis efficiency through uniform size and density. This study investigated the effect of pyrolysis temperatures of the pellets on the yield and quality of the produced bio-oils. Pyrolysis was carried out non-isothermally with a heating rate of 40°C/min, starting at room temperature and continuing until the final temperature was reached, which was varied at 300°C, 400°C, and 500°C in an N₂ atmosphere. The condensed vapor was then collected in a closed container and subjected to several analyses, including yield, viscosity, density, pH, calorific value, and chemical composition. Results show that the optimal temperature was 400°C, at which the bio-oil exhibited the highest yield (43.8% wt), the lowest viscosity (2.05 cSt), the highest density (1.138 g/mL), and a sufficient calorific value (1.0 kcal/g on a wet basis). Gas Chromatography-Mass Spectrometry analysis revealed that the acidic compounds (phenolics and carboxylic acids) in bio-oil increased with increasing pyrolysis temperature. Higher temperatures increase bio-oil yield by breaking down biomass components, such as lignin. However, excessive heat causes the thermal cracking of the produced organic vapors, thereby reducing yield and increasing acidic compounds. Our novel study presents new opportunities for utilizing pelletized biomass waste-derived bio-oil as a biofuel. However, improving bio-oil quality—particularly by reducing acidity and increasing calorific value—may require upgrading techniques such as catalytic pyrolysis, which should be explored in future research.

Abstract: Avocado seeds can be used as raw materials for making biodiesel because of their abundance and their underutilized potential. A catalyst is needed to accelerate the reaction, such as CaO, which can be made through the calcination process of green mussel shells that contain 97.2% CaCO₃. This study aims to obtain CaO catalysts to be used in the synthesis of biodiesel made from avocado seeds using the reactive extraction method. The parameters measured were the density and viscosity values of the biodiesel produced. The CaO catalyst concentration was determined to be 5% (w/w). The operation time was 8 hours, and the ratio of methanol to avocado seeds was 9:1 (v/w), with an operating temperature of 65°C. This study obtained a CaO catalyst from green mussel shells with a CaO content of 78.5%, which is composed of Ca and O elements and exhibits large porosity, as determined by SEM-EDS testing. The free fatty acid (FFA) content in avocado seeds was 2.38%, biodiesel yield was 80.19% with density and viscosity values of 1,021.48 kg/m³ and 14.98 cSt, respectively. The density and viscosity values did not meet the requirements of SNI No. 7182:2015 because the products produced may still contain impurities.

Abstract: Livestock manure is one of the sources of biomass whose usage has yet to be improved. Cow manure can be utilized as a raw material for producing briquettes, serving as an alternative energy source. This alternative fuel has advantages in terms of the production process and the simplicity of raw material usage. The goal of this study was to examine the influence of temperature variations on the features of briquettes made from cow dung. Briquettes are made in three steps: raw material preparation, molding, and carbonization via pyrolysis. For one hour, pyrolysis was carried out at temperatures ranging from 350°C to 500°C. Briquettes’ quality is decided once they have been tested. The yield value of the briquette produced ranges between 31.70% and 40.08%, with an average of 38.91%. The results indicate that the density ranges from 0.851 to 0.903 g/cm³, the moisture content ranges from 0.58% to 1.29%, and the heating value ranges from 4546.9 to 5108.5 kcal/kg. According to the findings of the drop test, none of the samples broke. The best pyrolysis briquette from cow manure is at a temperature of 500°C with a yield of 31.71%, a moisture content of 0.58%, a density of 0.903 grams/cm³, and a heating value of 5108.5 kcal/kg.

Abstract: Regulations governing welding in the oil and gas industry mandate post-weld heat treatment (PWHT) for all welded joints, regardless of pipe wall thickness. The maximum permissible hardness is limited to 248 HV to prevent cracking. However, PWHT is time-consuming, energy-intensive, and costly. This study investigates the use of interpass temperature control and the temper bead welding technique as alternative methods for reducing weld hardness without PWHT. SA-335 Grade P11 low alloy steel pipes were welded using the GTAW process with ER80S-B2 filler metal and 99.99% argon gas. A preheat temperature of 250 °C was applied in all conditions. Four experimental groups were investigated: (1) PWHT at 650 °C for 1 hour, (2) low interpass temperature at 250 °C, (3) high interpass temperature at 600 °C, and (4) temper bead welding with 17 overlapping beads. The first three groups used 7 beads for comparison. Weld quality was assessed using VT, PT, and RT. Hardness testing served as the primary evaluation method, followed by tensile, bend, macrostructural, and microstructural analysis. Hardness results showed that the PWHT and high interpass groups remained below 248 HV, with the temper bead group achieving the lowest weld metal hardness (215.5 HV). The low interpass group exceeded the limit (up to 256.3 HV). All specimens failed in the base metal during tensile testing, with average strengths ranging from 498.3 MPa (PWHT) to 526.3 MPa (temper bead). No critical defects were found in bend tests. Microstructural comparison revealed that temper bead welding produced finer and more uniform grains, contributing to lower hardness and improved thermal softening in the HAZ.

Abstract: Welding process is widely used as a metal assembly technique in various industries, including construction, automotive manufacturing, pressurization, and shipbuilding. In ship repair and fabrication, dissimilar welding between carbon steel and cast iron is often required, for example, in assembling appendages such as propeller shafts, yokes, and other equipment. Although cast iron offers high strength about 700 MPa and weight reduction benefits, its poor weldability due to high carbon content often leads to cracking when joined to carbon steel. Previous studies have found that preheating before welding mitigates rapid cooling and martensite formation, while buttering with Ni-based filler reduces carbon diffusion and carbide precipitation at the fusion boundary. This research has been carried out to investigate various procedures for dissimilar welding ductile cast iron A536 and carbon steel A36, as follows: (1) no preheat or buttering (Control), (2) preheating only (PH), (3) buttering only (BT), and (4) combined preheat and buttering (PHBT) to evaluate their effects on tensile strength, hardness, and microstructural evolution. Successful study of dissimilar welding between carbon steel and cast iron will reduce the cost of ship maintenance, increase its service life, and provide a path for more sustainable development.

Abstract: This paper presents an analytical model for analyzing two bonded dissimilar piezoelectric materials weakened by multiple embedded cracks. The medium is subjected to anti-plane mechanical and in-plane electrical loading. We consider the interface imperfect to address potential electro-mechanical damage at the interface, with the electro-mechanical imperfection represented by a linear spring model. First, the solution for a dynamic electro-elastic dislocation in the piezoelectric layer is obtained using the integral transforms technique. Subsequently, the dislocation solutions are utilized to transform the problems into a set of singular integral equations featuring Cauchy kernels, which are then solved numerically in the Laplace transform domain. The numerical Laplace inversion technique calculates the dynamic stress intensity factors (DSIFs). Several examples are analyzed to derive DSIFs for varying crack lengths and the spring constants reflecting imperfect electro-mechanical bonding and the material properties of the piezoelectric layers.

Abstract: Masjid Al-Haram experiences some of the densest pedestrian flows globally, with foot traffic exceeding 278,000 individuals per hour during peak rituals. This presents a unique opportunity to convert human kinetic energy into usable electricity via piezoelectric floor systems. This paper investigates whether low-cost, fused-deposition-based (FDB) 3D printing methods can fabricate PZT/polymer smart mats that are both mechanically robust and electrically responsive. Two strategies are compared: (i) a modular approach, where discrete PZT tiles are embedded in a compliant TPU lattice, and (ii) a mixed-blend approach, where PZT-filled and insulating filaments are co-extruded into a monolithic structure. Simulations are used to assess each design’s print fidelity, interfacial adhesion, electrical output under 750 N footstep loading, fatigue life across 10⁶ cycles, and foldability for roll-out deployment. Results indicate that while the mixed-blend design offers superior fabrication speed, the modular structure yields more stable electrical performance. This study provides a simulation-backed design framework for scalable, energy-harvesting mats tailored for high-traffic religious spaces, setting the stage for future prototyping and deployment.

Abstract: Reinforced concrete dapped end beams (RC-DEBs) in service suffer damage near the reentrant section under unknown loading conditions, reducing service life, particularly when recurrent loading is considered. In this investigation, a Finite Element Model (FEM) of a standard RC-DEB was used, together with a 3-dimensional concrete model and a fixed constitutive model. The girder reinforcement was designed in compliance with Eurocode 2 (EN-2) criteria for shear and deflection analysis. The level of deterioration under fatigue difficulties was determined by doing a fatigue analysis of moving and fixed pulsing loads at the midpoint and offset loading. A scaled-down experimental validation of the FEM for fixed pulsing loading was considered to better understand fatigue deterioration for practical applications. The major mode of damage observed is shear brittle failure at the beam's reentrant region. Although the moving load proved to be more damaging than the fixed pulsing load, loading at an offset of a/d of unity had an effect on the reentrant portion. The EN-2 code is nonconservative when it comes to describing the reinforcement at the reentrant section; for optimal performance, the hanger reinforcement must be properly anchored to the shear.

Abstract: The increasing environmental impact of natural aggregate extraction and the growingaccumulation of ceramic waste have prompted the search for sustainable construction materials.This study investigates the feasibility of using ceramic waste from waste electric insulators aspartial replacement for natural coarse aggregates in concrete production. The ceramic waste fromwaste electric insulators termed here as porcelain insulator ceramic waste (PICW) sourced fromlocal dumpsites was processed and incorporated into concrete mixes at replacement levels of 0%,15%, 30%, 50% and 75%. Coarse aggregates of maximum size 20 mm were used in this study.The ceramic waste from waste electricity insulators was crushed using a hammer up to size 20 mm as indicated in the particle size distribution. Grade 25 of concrete was designed for in the mixdesign. Laboratory tests, including sieve analysis, moisture content, specific gravity, waterabsorption, workability (via slump testing), and compressive strength were conducted to assess themechanical and physical properties of both fresh and hardened concrete at curing intervals of 7,14, and 28 days. The findings indicate that concrete containing up to 30% ceramic waste exhibitshighest cempressive strength and workability comparable to conventional concrete withoutcompromising its durability and workability, demonstrating its potential as a viable and ecofriendlyalternative. The highest compressive strengths were recorded with 15% and 30% at 25.7and 25.5 MPa respectively. Conversely, tensile strength declines with increasing PICWreplacement at 28 days thus 3.32, 3.16, 2.99, 2.31 MPa. The study underscores the dual benefitsof reducing construction costs and promoting sustainable waste management, making ceramicwaste a promising material in the pursuit of green construction practices i.e., sustainableconstruction by mitigating environmental degradation and promoting circular waste utilization.The study offers valuable insights for future standards development and large-scale industrialapplications.