https://ajme.aut.ac.ir/ AUT Journal of Mechanical Engineering en daily 1 Wed, 01 Jul 2026 00:00:00 +0330 Wed, 01 Jul 2026 00:00:00 +0330 https://ajme.aut.ac.ir/article_5971.html This review presents a comprehensive and critical evaluation of carbon-based and graphene-based thermal interface materials (TIMs) for advanced thermal management in electronic systems. Conventional TIMs typically exhibit thermal conductivities in the range of 0.1–10 W/m·K, limiting their effectiveness in high-power and miniaturized devices. In contrast, carbon-based TIMs demonstrate significantly enhanced performance, with carbon nanotube (CNT) composites achieving 8–12 W/m·K and graphene-based composites reaching up to 23.2 W/m·K at 60 wt% loading. We provide a detailed comparative analysis of CNT and graphene architectures, emphasizing their exceptional intrinsic thermal conductivities (~3000 W/m·K for CNTs and ~5000 W/m·K for graphene) and addressing practical challenges such as interfacial resistance, dispersion uniformity, and large-scale integration. The review synthesizes fabrication strategies, performance trends, and application-specific considerations, while outlining future directions including hybrid architectures, eco-friendly formulations, and cost-effective, scalable manufacturing techniques. By integrating quantitative comparisons and identifying critical research gaps, this work offers a roadmap for next-generation TIM development aimed at a high-power electronics, telecommunications, and computing systems, where efficient thermal management is essential for reliability, energy efficiency, and long-term operational performance. https://ajme.aut.ac.ir/article_5898.html This paper presents a comprehensive parametric analysis concentrated to the design of a novel low temperature hydrogen porous micro-reactor. The main important of this work is optimizing the water production process by a complete parametric description. In the analytical solution of this problem, the velocity profile is first determined by solving the momentum equation, and this result is then used in the energy and mass concentration equations to obtain thermal and mass parameters. The solution is achieved through a non-asymptotic solution that concurrently incorporates both mathematical and physical aspects, taking into account the matching conditions . Maximum variation of Nusselt number in the width of microchannel is observed for the alumina porous medium, with values of 58.70% and 67.69% respectively with 95% and 90% porosities. The rate of hydrogen to water conversion in alumina media is approximately 41% faster than titanium oxide and 67% faster than silicon carbide. The maximum variation of Sherwood number in the width of microchannel is observed for the silicon carbide porous medium, with values of 58.33% and 50.13% respectively with 95% and 90% porosities. As the porosity coefficients increase from 85% to 95% the variation rates of fluid and solid phase temperature is decreased from 78.01% to 45.09% and 65.92% to 35.09%. the porosity coefficient, the rate of hydrogen to water conversion is increased from 43.01 to 75.05%. https://ajme.aut.ac.ir/article_5939.html The growing demand for sustainable energy highlights the need for efficient small-scale wind turbines, especially in urban areas with low wind speeds and limited space. This study experimentally examines aerodynamic augmentation effects on turbine performance using shrouds and tailored flanges. Four turbine configurations—a bare turbine, a turbine with a simple shroud, a shroud with a vertical flange, and a shroud with an improved curved flange—were 3D printed and tested in a controlled wind tunnel under realistic low- to moderate-speed urban wind conditions. Airflow velocity at the shroud throat and corresponding power output were measured across various wind speeds. Results show that both flange curvature and height significantly affect aerodynamic performance. The curved-flange design consistently increased throat velocity and turbine output, achieving up to a 32.3-fold power gain over the bare turbine at 5 m/s. At higher wind speeds, differences among augmented configurations decreased, yet the improved curved flange still delivered approximately 4.3 times the output of the bare turbine at 16.35 m/s. These findings emphasize the importance of outlet geometry in lowering startup thresholds, sustaining airflow acceleration, and maximizing energy capture. Overall, this study provides robust experimental evidence that shrouds with improved curved flanges significantly enhance small-scale urban wind turbine efficiency, offering a practical solution for low-wind energy harvesting and guiding future designs for improved performance across diverse wind regimes. https://ajme.aut.ac.ir/article_5940.html Polylactic acid (PLA), a biodegradable thermoplastic derived from renewable resources, has emerged as one of the most widely utilized materials in fused deposition modeling (FDM) due to its printability, cost-effectiveness, and environmental sustainability. Despite its popularity, PLA parts fabricated by FDM often suffer from reduced mechanical reliability as a result of anisotropy and processing variability. This study presents a comprehensive experimental and numerical investigation into the strain-rate-dependent mechanical behavior of FDM-printed PLA components, with particular emphasis on the influence of build orientation, raster angle, and infill pattern on tensile performance. ASTM D638 Type-V dog-bone specimens were fabricated using Ender 3 Pro and Xplorer 3D printers and tested at strain rates of 2 mm/s, 5 mm/s, and 10 mm/s on a Universal Testing Machine. Results revealed that tensile strength increases significantly with higher strain rates, showing improvements of up to 115%, though at the expense of ductility. Among orientations, on-edge samples exhibited the highest strength of 32.3 MPa, while raster angles aligned with the loading axis enhanced stress transfer and stiffness. Infill geometry further influenced energy absorption, with concentric patterns outperforming hexagonal arrangements. Numerical simulations conducted in Ansys and Abaqus correlated well with experimental findings, validating stress–strain responses and failure trends. The combined insights demonstrate the critical role of process parameters in tailoring the mechanical properties of FDM-printed PLA parts. https://ajme.aut.ac.ir/article_5941.html This research investigates the effective input parameters of the Elliptical Cross-Section Spiral Equal-Channel Angular Extrusion (ECSEE) method and selects the optimal performance. The influential parameters in the ECSEE method are considered as input factors in the experimental design, which are expressed in three parameters: punch speed, sample annealing, and the number of extrusion passes. Subsequently, a Taguchi design of experiments (DOE) table was created for each input parameter according to its variation range. After designing the experiments, the output results of forming force and plastic strain for each level were obtained using experimental tests. The optimization of the input values was investigated based on the S/N ratio criterion ("the smaller the better" for forming force and "the larger the better" for plastic strain). The obtained results indicated that the optimal test level in the ECSEE method for achieving the minimum forming force is using a punch speed of 6 or 9 mm/min, sample annealing at 300°C for 120 minutes, and 2 extrusion passes. Furthermore, to achieve the maximum plastic strain, the optimal parameters are a punch speed of 9 mm/min, sample annealing at 200°C for 120 minutes, and 6 extrusion passes. https://ajme.aut.ac.ir/article_5974.html This research aims to enhance the hardening behavior of a non-rotating 2D tri-axial braided composite (2DTBC) fan blade, through investigating the backbone curve characteristics. This enhancement raises the blade’s natural frequencies at large oscillation amplitudes, thereby delaying the onset of resonance. A combination of different methods has been employed, including an Artificial Neural Network (ANN), an analytical method, the finite element method (FEM), and a single-objective genetic algorithm (GA). The ANN was used to establish the relationship between the braiding machine parameters and the structural characteristics of the braided fabric. Micromechanical modeling was utilized to determine the mechanical properties of the braided composite. Based on the first-order shear deformation theory (FSDT), the nonlinear free vibration partial differential equations of the composite blade shell were derived using Hamilton's principle. The FEM was employed to solve the differential equations and obtain the corresponding backbone curves. Finally, a single-objective genetic algorithm was deployed to optimize the braided composite structure in order to increase the hardening behavior of the blade. The obtained results demonstrate the viability of the proposed approach. The results indicate that the hardening behavior has increased by a factor of 6.8 compared to the non-optimized case. https://ajme.aut.ac.ir/article_5979.html Conformal cooling channels have been proposed as a promising alternative to traditional cooling channels. The objective of this paper is to introduce a novel method of producing milled groove conformal cooling channels (MGCCC) for injection molding using hard tooling. An experimental investigation was carried out by comparing the conventional cooling channel approach with CCC to optimize the cooling time. The study focuses on a specific case study of an "enclosure part" from a medium-scale industry(Mold Craft Engineers Pvt. Ltd. in Pune). The injection mold tools for this part used straight drilled cooling channels, which resulted in uneven cooling and longer cooling times. The milled groove CCC was designed to improve the cooling time and reduce cycle time, to conform to the shape of the cavity. The fabrication of the mold with CCC was performed using CNC machining. Milled grooves were sealed with a fitted plate and O-rings to prevent leakage. Temperature measurements were recorded using RTDs embedded near the cavity surface under controlled molding conditions. The experimental analysis, which involved temperature measurement of the molded part during the injection molding process, revealed that the mold with milled groove CCC exhibited shorter cooling times than the mold with straight cooling channels. Cooling time was reduced by 73.33% compared to the conventional cooling system. https://ajme.aut.ac.ir/article_5993.html This research investigates the nonlinear free oscillation analysis of imperfect, functionally graded, porous, stiffened, open conical panels resting on an elastic foundation under thermal conditions. To establish the governing nonlinear dynamic equations, the classical shell theory, the nonlinear von Kármán assumptions, and Hamilton’s principle are employed. Due to the use of the multiple scales method (MSM), the equations of motion must be rewritten in dimensionless form; therefore, the dimensionless parameters are introduced. The Galerkin approach is utilized to discretize the dimensionless partial differential equations (PDEs). By neglecting in-plane inertias and solving the resulting algebraic relations, the discretized system reduces to a nonlinear ordinary differential equation. Based on this final nonlinear ODE, the linear frequencies are extracted, and the numerical results are validated with previous studies for different geometries. Furthermore, the MSM is employed to determine the nonlinear frequency relationship. Finally, the effects of geometrical variations, material properties, imperfections, and foundation effects are investigated. The reported outcomes highlight the importance of imperfect FG-porous stiffened conical panels to multiple parameters, providing valuable insights into their vibration behavior under simply supported conditions. https://ajme.aut.ac.ir/article_6032.html The study explores the behaviour of systems under both free and forced vibrations of spherical sandwich panels supported by an elastic foundation exposed to various impact load profiles. The panels consist of multilayer composite face sheets formulated based on the first-order shear deformation theory, and a soft core characterized by a higher-order theory employing third-order in-plane and second-order transverse displacement fields. By calculating the mechanical energy components, and introducing a higher-order element with nine nodes and 15 degrees of freedom for each node, the element stiffness and mass matrices were determined. Boundary conditions are simulated through distributed virtual springs. A free vibration problem is evaluated to extract the structure’s natural frequencies and mode shapes. Using the Newmark method, time response of displacement, velocity, acceleration, and phase planes are calculated for various impact profiles, specifically for half-sine pulses. This comprehensive analysis of sandwich panels' dynamic response under various impact loads reveals that the load profile critically determines structural behavior, essentially governing the boundary between safe operation and potential failure. For example, sudden loads like rectangular pulse emerged as the most critical case, causing extreme discontinuous responses across all dynamic parameters, and gradual loads (Gaussian/exponential) proved optimal for sensitive applications by generating smooth, controlled structural responses and providing ideal performance for stability-critical systems. https://ajme.aut.ac.ir/article_6036.html This article proposes architectural strategies and comfort conditions for designing nearly zero-energy buildings (NZEBs) across different climatic regions of Iran, based on the Köppen-Geiger classification method and passive design techniques. According to the Köppen-Geiger climate classification, Iran's climate is divided into nine zones. The primary climatic zones considered in this study include Bwh, Bwk, Bsk, Bsh, Csa, Cfa, Csb, Dsa, and Dsb. The impact of climatic conditions on the design of nearly zero-energy buildings was analyzed using the Köppen-Geiger method. the selected cities within the mentioned climate zones were analyzed by the Climate Consultant software (CCS) in EPW format, utilizing the ASHRAE Standard 55 and also PMV (Predicted Mean Vote) comfort model. By inputting weather data from selected cities into CCS, output results including comfort conditions, natural ventilation, cooling, heating, and other parameters across the nine climatic zones were obtained. Additionally, during designing NZEBs, passive architectural parameters such as window shading, passive solar radiation, and internal heat generation in these nine climate zones were examined. The results showed that the BWh climate (Yazd) provides the highest thermal comfort at 19.7%, while the CFa climate (Anzali) provides the lowest thermal comfort at 3.6%. In the BWh climate, window shading, evaporative cooling, and internal heat gain have better conditions for comfort compared to other climates, with percentages of 16.8%, 25.8%, and 22.5%, respectively. https://ajme.aut.ac.ir/article_6045.html Additive manufacturing of biopolymer composites is rapidly advancing biomedical engineering. By combining synthetic polymers with natural biopolymers, inorganic ceramics, nanomaterials, and bioactive molecules, AM enables patient-specific constructs with high geometric precision and tunable biological performance. These materials support applications across hard and soft tissues, including bone regeneration, cartilage repair, wound healing, vascular grafts, and cancer modeling. Despite this progress, major barriers remain: mechanical-degradation mismatches, limited vascularization in thick constructs, photoinitiator-related cytotoxicity, and inter-laboratory variability that reduces reproducibility and slows clinical translation in real-world settings. Broader adoption is further constrained by the lack of standardized protocols and clear regulatory pathways. We compare AM modalities (extrusion, vat photopolymerization, and powder-bed processes) through a cost-benefit lens, outlining when each optimally balances resolution, throughput, sterility, and cell compatibility. To address these gaps, recent work (2020–2025) is shifting the field from static scaffolds toward adaptive, intelligent, and sustainable platforms, leveraging 4D printing, nanotechnology-enabled reinforcement and bioactivity, AI-driven design optimization, and greener feedstocks such as sustainable biopolymers. Notably, 2025 reports on multi-material bioprinting for neural tissues show improved print fidelity and bioactivity, enabling more realistic microvascular networks and neural interfaces. By synthesizing these advances and critically evaluating current limitations, this review proposes strategic directions for AM to mature into a clinically relevant, globally sustainable manufacturing approach. Biopolymer composites are not incremental upgrades; they are pivotal enablers of next-generation regenerative medicine. https://ajme.aut.ac.ir/article_6046.html This research aims to investigate the external aerodynamics of the IKCO-DENA+ car, which leads to the annoying sound inside the cabin. In this research, the sources of aerodynamic noises were identified using wind tunnel tests on a 2/5 scaled model. Smoke flow visualization of the flow around the car for finding out aerodynamic characteristics and noise sources has been conducted. The results obtained from visualization showed that six different factors can be considered as a source of noises, including 1.the distance between the side mirror and the body, 2. the aerodynamic form of the side mirror, 3. the rear passenger quarter window, 4. the shark antenna, 5. car handles, and 6. indentation design feature on the rear door of the car. Then, within the next steps, the surface modification solutions regarding the identified noise sources were tested. In addition, Measurements using hot wire anemometry and pressure sensors were performed at different velocities of 18, 36, 54, 72, 90, 108 and 118.8 km/h. The results showed that surface modification related to quarter window led to a reduction of the flow disturbances and the aeronoise level on the car’s rear door glass significantly. Furthermore, modifying the side mirror of the car has considerably improved the aerodynamic behavior within the area of the front door glass. Consequently, these two modifications reduced pressure disturbances by 9% and 5%, respectively. https://ajme.aut.ac.ir/article_6048.html For many years, biodiesel has been seen as an alternative fuel with the ability to eventually replace diesel. Products that are emitted when engines undergo a complete combustion reaction provide no direct health risks to humans. Due to certain fuel characteristics, biodiesel performs poorer during combustion process than diesel fuel. As a result, smoke emissions, complete combustion products like CO2, and incomplete combustion products including HCs, CO, and NOX are released into surrounding. An attempt has been made to enhance combustion and emission performance of CRDi-VCR type diesel engine using B20 neem biodiesel with a novel nanoparticle mixture of Al2O3 and ZnO as nano fuel additives for various dosing levels. B20 Neem biodiesel with nano additives was tested on a CRDi-VCR type diesel engine at a constant speed of 1500 rpm at various loads. Due to higher oxidation rate of hydrocarbon molecules, the nano additive reduced CO emissions in studies while improving the thermal conductivity, mass dissipation, and heat transfer of the tested nano fuels. Due to the improvement in the combustion reaction, CO2 emission increased with product of complete combustion. Brake specific fuel consumption was reduced at full load condition with the addition of 25 ppm NPs. Also, neem biodiesel fuel results in appreciably improved brake thermal efficiency, lower values of smoke opacity, and lower CO, NOX and HC emissions. https://ajme.aut.ac.ir/article_6055.html In this study, the convective transport of a temperature-dependent magneto-micropolar fluid over a stretching surface embedded in a porous medium is examined. The formulation accounts for viscous dissipation, internal heat generation or absorption, and radiative heat transfer modeled through the Rosseland diffusion approximation, which is appropriate for optically thick media. The governing equations, developed without the use of similarity transformations, are solved using the Optimal Homotopy Analysis Method (OHAM). The resulting velocity, microrotation, and temperature fields are illustrated through graphical and tabulated data across a broad range of physical parameters. Validation against existing literature demonstrates the reliability of the present approach. Quantitative analysis shows that the microrotation boundary layer decreases by approximately 18–25% with increasing micropolar parameter, while thermal boundary layer thickness increases by about 10–14% under stronger radiative effects. Moreover, micropolar fluids exhibit a thinner momentum boundary layer compared to Newtonian fluids under identical conditions. Specifically, the Newtonian case yields a thinner layer relative to the micropolar case . Overall, the results provide valuable insights into micropolar fluid behavior with practical implications in porous and radiative flow systems. https://ajme.aut.ac.ir/article_6066.html This study evaluates the sensitivity of modal parameters to incomplete adhesion in single-lap adhesive joints by comparing the vibrational behavior of fully bonded joints and joints with a macroscopic partial bond (≈50% loss of bonded area in the overlap). Beyond prior studies on crack-like or delamination-type defects, often using intrusive or destructive inspections, the present work targets a practically relevant macroscopic manufacturing flaw within a fully non-destructive modal testing framework. An integrated experimental–numerical approach is employed: aluminum 7075-T6 beams bonded with epoxy 828 are tested using impact-hammer excitation and laser Doppler vibrometer, and responses are processed in MATLAB and MEscope to extract natural frequencies and damping ratios. A three-dimensional finite element model in Abaqus/CAE is refined via limited experimental calibration. Results show 3–15% reductions in the first eight bending natural frequencies of defective joints relative to intact ones, with stronger effects in higher modes due to dominant stiffness loss over minor mass reduction. The damping ratio increases about sevenfold (0.0032 to 0.0236) in the defective specimen, attributed to frictional dissipation at the unbonded interface and contact nonlinearities supported by mode-shape analysis. These quantified shifts in frequency and damping establish modal parameters as reliable, non-destructive indicators of incomplete adhesion in single-lap joints and provide a basis for vibration-based structural health monitoring and defect detection in adhesively bonded components in aerospace, automotive, and multi-material structures.