https://stmechanics.bmtc.ac.ir/ Science and Technology in Mechanical Engineering en daily 1 Wed, 21 Jan 2026 00:00:00 +0330 Wed, 21 Jan 2026 00:00:00 +0330 https://stmechanics.bmtc.ac.ir/article_222110.html Particle-reinforced metal matrix composites are among the latest engineering materials, and their rapid development in recent years can be attributed to their exceptional properties, including high specific strength, wear resistance, corrosion resistance, high elastic modulus, and wide-ranging applications. These materials are used in various industries such as aerospace, telecommunications, electronics, automotive, defense, and many other commercial and consumer products. In this study, the effect of the percentage of diamond particles with a size of 100 micrometers on the mechanical and wear properties of bronze-diamond composites is investigated. Composite powders with varying diamond percentages in a bronze matrix are prepared using a ball mill to mix the bronze and diamond powders, and the resulting composite powders are consolidated through hot pressing. Using scanning electron microscopy, the effect of diamond content on their uniform distribution, the microstructure of the bronze matrix, and the mechanical and wear properties are examined. This study investigates the effect of different weight percentages of diamond particles (8%, 10%, 12%) on the properties of bronze-diamond composites. The results indicate that adding diamond to the metal matrix reduces flexural strength. Furthermore, as the weight percentage of diamond increases, flexural strength decreases, while wear resistance improves with higher diamond content. https://stmechanics.bmtc.ac.ir/article_227244.html Tillage operations are very important in various aspects, including improving the physical quality of the soil, maintaining moisture, increasing organic matter, and reducing erosion, and play a fundamental role in providing a suitable substrate for optimal plant growth... In this regard, the design and construction of a multi-purpose rotivator with the aim of simultaneously performing tillage and planting operations creates a revolution in increasing productivity, reducing fuel consumption, time, and total cost of production. This device, with its combined mechanisms, is capable of performing operations such as breaking up clods, aerating the soil, preparing the seedbed, and digging adjustable furrows simultaneously. The double-sided folding structure and design compatible with road transport conditions are other important features of this advanced tiller. In addition to the technical advantages, using this device with modern technologies will help automate agricultural operations, reduce resource losses (such as water, energy, and fertilizer), and adapt to the principles of sustainable agriculture. Due to the lack of a similar domestic model and its affordable price compared to foreign models, this device can play an effective role in the development of agricultural mechanization in the country. Thus, the multipurpose tiller, as an efficient, smart, and economical tool, will pave the way for increasing productivity, conserving resources, and achieving sustainable development goals in modern agriculture. https://stmechanics.bmtc.ac.ir/article_227802.html The application of the Equal Channel Angular Pressing (ECAP) process imposes severe plastic strains on the metallic billet. As a result of these imposed strains, the initially coarse grains are transformed into ultra-fined or nanostructured grains, and beneficial microstructural evolutions occur in the texture of the material, which lead to improvements in mechanical properties. In this study, commercially pure titanium (CP-Ti) BT1-0, as a hard-to-deform material, was placed inside a casing made of pure copper and subjected to four passes of warm ECAP at a temperature of 250°C in a 135° channel using route Bc, accompanied by the application of back pressure through extrusion in the end of die. The simultaneous effect of back pressure and the casing on the grain structure and mechanical properties of the target material, i.e., CP-Ti, was evaluated. Experimental results showed that the grain size was refined from 49 µm in the initial annealed state to 710 nm after four ECAP passes. The compressive yield and ultimate strength, and also compressive elongation changed from 267 MPa, 899 MPa, and 51.8 mm/mm in the non-ECAPed condition to 958 MPa, 1375 MPa, and 30.7 mm/mm after ECAP processes, corresponding to increases of 359% and 153%, and a decrease of 59%, respectively. The average Vickers hardness also increased from 163 Hv in the initial annealed state to 289 Hv after four ECAP passes, representing a 77% enhancement. https://stmechanics.bmtc.ac.ir/article_228147.html Damage detection, aimed at preventing overall structural failure and enabling planned repair and rehabilitation, has been a significant research focus in recent years. Data-driven structural health monitoring through structural response analysis constitutes the core of contemporary studies. This approach utilises artificial intelligence tools, particularly artificial neural networks, to eliminate the need for complex preprocessing of time-series data and achieve more accurate results compared to traditional structural health monitoring and damage detection methods. In this study, an unsupervised deep neural network (convolutional autoencoder) is proposed to reconstruct input data and employ the reconstruction error as a damage-sensitive feature. The findings demonstrate that the proposed model achieves highly accurate damage detection across various structural conditions, despite being trained solely on healthy structural data. Moreover, the model exhibits favourable performance in terms of the number of training parameters and computational effort. Finally, to validate the effectiveness of the model, the results are compared with those of similar studies, demonstrating superior accuracy. https://stmechanics.bmtc.ac.ir/article_228618.html Multi-Effect Distillation (MED) systems are advanced technologies for seawater desalination, valued for their high energy efficiency and heat recovery capabilities in industrial and potable water applications. This study developed a mathematical model based on mass, energy, and thermodynamic balances to analyze system performance. By solving the governing equations, the impact of key parameters—number of distillation stages, inlet steam temperature, and brine concentration—on the Gain Output Ratio (GOR) was quantitatively evaluated. Results show a linear positive correlation between the number of stages and GOR improvement, with a maximum GOR of 12.049 achieved in a 12-stage configuration at an 80°C feed temperature. Each additional stage increases GOR by approximately 15%. However, the motive-to-sucked steam ratio grows exponentially with more stages, significantly increasing motive steam consumption. These findings provide an analytical framework for optimizing industrial MED systems, enhancing energy efficiency and economic savings. https://stmechanics.bmtc.ac.ir/article_228621.html The passage of trains over railway rails induces significant vibrations in the rail structure—a phenomenon that has gained increasing importance with the development of high-speed rail systems. Severe vibrations can lead to increased fatigue stresses, reduced rail lifespan, and potential structural instability. One effective approach to mitigating these issues is to increase the gap between the natural frequency of the rail and the excitation frequency, thereby preventing resonance. In this study, the geometric dimensions of the railway rail are optimized with the aim of enhancing vibrational performance and reducing fatigue-induced stresses. To achieve this, a combined methodology involving Response Surface Methodology (RSM) and Genetic Algorithm (GA) is employed. A numerical model of the rail is developed and simulated using ANSYS software. The analyses focus on extracting natural frequencies and evaluating stress responses under torsional, bending, and combined vibration modes. The results indicate that increasing the excitation speed leads to a reduction in the optimal width of the rail’s bottom flange for similar vibration modes. Additionally, increasing the width of the rail head from 40 to 80mm significantly reduces local stresses. These findings provide a practical basis for intelligent and resilient design of railway rails under dynamic loading conditions https://stmechanics.bmtc.ac.ir/article_230149.html Predictive maintenance and speed control of rotating machines are crucial in modern industries due to the reduction of maintenance costs and the improvement of efficiency and reliability. This paper presents a method for fault diagnosis and speed control of induction motors. The proposed method employs two algorithms for fault diagnosis. In the first algorithm, a novel method for extracting statistical, frequency, and energy features is utilized, along with machine learning algorithms for fault classification. If the fault detection accuracy of the first algorithm is not suitable, the second algorithm is used. This algorithm utilizes a convolutional neural network (CNN) and an optimized long short-term memory (LSTM) model. In this network, feature extraction and selection are performed automatically. We present a new algorithm for optimizing layers and parameters through an adaptive ant colony algorithm and likelihood functions. The proposed methods are tested on three datasets. In the first dataset collected for this research, the focus is on the healthy state, bearing fault, and uncoupled condition. In the second dataset, we focus on the defects of the inner and outer rings of the bearing. In the third dataset, eight cases are considered, including seven cases with defects in the stator and rotor, and one healthy case. Vibration and acoustic data are used for fault diagnosis. Then, a control algorithm, including a fractional-order optimal control controller, is presented to control the motor speed, especially when it is under fault conditions. The results indicate that the first algorithm is suitable for the first and second datasets, while the second algorithm is more suitable for the third dataset. https://stmechanics.bmtc.ac.ir/article_230150.html This study presents a comprehensive, APA-style summary of an experimental investigation into modified Arcan U-shaped CFRP joints bonded with epoxy and polyurethane adhesives. The objective is to evaluate how loading angle and mode influence joint strength, failure mechanisms, and ultimate performance, with the goal of informing design practices for adhesive-bonded CFRP joints. The methodology entails preparing CFRP specimens with modified Arcan fixtures, subjecting them to loading angles of 0°, 45°, 60°, and 90°, and imposing mode-specific loading conditions (shear, mixed shear–tension, and tension). Key findings indicate systematic variation of strength and failure modes with loading angle, with distinct trends for adhesive/cohesive failures versus fiber-related failures. The results underscore the critical role of loading geometry in governing interfacial behavior, highlight the relevance of Arcan-based testing for evaluating bonded joints, and discuss implications for structural design, safety margins, and future research directions. Limitations include the controlled laboratory setting and specimen-scale constraints, suggesting caution when extrapolating to full-scale structures. The study advances understanding of CFRP joint performance under varied loading and offers practical guidance for engineers designing adhesive-bonded CFRP assemblies https://stmechanics.bmtc.ac.ir/article_232636.html The Mindlin plate theory, which accounts for shear deformation effects, is employed to ensure accurate modeling of moderately thick plates. This paper investigates the efficiency of various dynamic relaxation methods for the elastic analysis of Mindlin plates. The main objective is to evaluate the advantages of twelve different relaxation schemes. The distinctions among these approaches lie in the determination of artificial parameters such as damping and mass, which are essential for the convergence of dynamic relaxation. The study focuses on assessing these methods based on numerical stability, convergence rate, and computational efficiency. Several Mindlin plate examples with diverse geometries and boundary conditions are solved to compare the performance of different dynamic relaxation techniques. Given the variety of the analyzed cases, the obtained results can serve as benchmark problems for Mindlin plate analysis. Key criteria, including the number of iterations required for convergence and the total computational time, are recorded for each method. The results reveal significant variations in efficiency among the twelve algorithms, with some exhibiting rapid convergence while others require considerably more iterations. A comprehensive ranking based on these computational metrics is established to identify the most efficient and robust techniques for practical applications. Furthermore, the study demonstrates the sensitivity of dynamic relaxation convergence to the selection of artificial parameters. Numerical results indicate that the Underwood method is efficient in terms of analysis time, while the minimum residual energy scheme achieves the fewest iterations for Mindlin plate analysis.Several benchmark cases of Mindlin plates with diverse geometries and boundary conditions are solved to compare the performance of the proposed DR schemes. Given the variety of solved examples, the results can serve as benchmark problems for Mindlin plate analyses. Key metrics, including the number of iterations required for convergence and total computational time, are recorded for each method. The results reveal significant variations in efficiency among the twelve algorithms: some exhibit rapid convergence, while others demand substantially more iterations. A comprehensive ranking system is established based on these computational criteria, identifying the most efficient and robust techniques for practical applications.Furthermore, this study highlights the sensitivity of dynamic relaxation convergence to the selection of fictitious parameters. Numerical results demonstrate the effectiveness of the Underwood method in computational time and the minimum residual energy technique in iteration count for analyzing Mindlin plates. https://stmechanics.bmtc.ac.ir/article_232639.html Base fluids generally have low thermal conductivity, but adding solid nanoparticles improves this property. In this research, spherical zinc oxide (ZnO) nanoparticles with diameters of 10-30, 35-45 and 80-100 nm were stabilized in ethylene glycol using a two-step method. CTAB surfactant and ultrasonic agitation were used to prevent particle aggregation. Nanofluids were prepared with volume fractions of 0.2 to 1% at temperatures of 20 to 60°C. Thermal conductivity was measured using the transient hot-wire method with a KD2-Pro device. Results showed that decreasing nanoparticle size, increasing temperature and increasing volume fraction significantly improved thermal conductivity, with the maximum increase (about 18%) observed at the highest temperature, smallest particle size and highest volume fraction. The effect of volume fraction was more remarkable at lower concentrations. Temperature increases facilitated heat transfer by weakening molecular bonds. Comparison of experimental data with analytical models showed that the difference between results increases with higher temperatures and volume fractions. Finally, a multivariate empirical model was developed and validated to predict the thermal conductivity of ZnO/EG nanofluid, which effectively describes the dependence of thermal conductivity on temperature, particle size and concentration. https://stmechanics.bmtc.ac.ir/article_233429.html Baseball is one of the most popular sports in the United States, and numerous studies have examined various aspects of its throwing mechanics, including ball release characteristics, upper-limb biomechanics, common shoulder and elbow injuries, and performance differences between left- and right-handed players. Given the high incidence of overuse injuries—particularly among pitchers—there is a growing need for advanced control strategies to optimize joint and muscle coordination during throwing. This study aims to develop an optimal control framework based on Sliding Mode Control (SMC) integrated with a detailed dynamic model of the upper limb during the baseball pitching motion. The proposed model enables precise regulation of joint angles and torques, helping maintain athletic performance while reducing musculoskeletal injury risk. The outcomes of this research have potential applications in rehabilitation systems, pitching skill training, and the development of assistive robotic technologiesGiven the high rate of repetitive motion injuries in this sport, particularly among pitchers, there is a need to develop control strategies to optimize muscle and joint movements. The goal of this research is to design an optimal controller based on the sliding mode control (SMC) method, along with precise dynamic modeling of the upper limb movement during baseball pitching. This model enables accurate control of joint angles and applied torques, allowing for both athletic performance preservation and reduction of musculoskeletal injury risks.The results of this study can be applied to the design of rehabilitation systems, training of throwing skills, and development of sports-assistive robots. https://stmechanics.bmtc.ac.ir/article_233433.html This study investigates the buckling and post-buckling behavior of composite pipes under internal pressure, with a focus on the effect of embedding NiTi wires with shape memory alloy (SMA) effect on improving mechanical capacity and controlling post-buckling. The pipes were made of carbon/epoxy composite (T300/5208) and fabricated using a filament winding process with a [−55/55] layup. Shape memory wires under 5% prestrain were embedded in multiple layers to provide compressive force against residual tensile stresses caused by curing and to enhance the mechanical performance of the tubes. Three models were analyzed using Abaqus software: a pipe without SMA and internal pressure, a pressurized pipe without SMA, and a pressurized SMA-reinforced pipe. Buckling analysis using a linear perturbation solver and examining the first five buckling modes was performed; then, post-buckling analysis using a general nonlinear static solver and applying initial deflection according to mode I was performed. The results showed that the presence of the memory wire increased the critical buckling force by less than 1% and increased the internal pressure capacity of the pipes by 20%, without negatively changing the post-buckling behavior under internal pressure. These findings indicate that the use of shape memory alloys can be an effective and practical solution for improving the mechanical performance and increasing the pressure capacity of composite pipes, especially in industrial applications and advanced structures. https://stmechanics.bmtc.ac.ir/article_234236.html The high sensitivity of spectral strain estimation has made it a powerful tool for early detection of failures and dynamic nonlinear instabilities. In this study, first, the modal analysis of a free-free aluminum beam was addressed in the form of three experimental, analytical, and numerical approaches. In the modal section, the dynamic responses of the beam were recorded at six points with a calibrated hammer impact test. The experimental results were combined with signal analysis and advanced algorithms to obtain modal parameters, including natural frequencies, modal vectors, and frequency responses, with an accuracy of more than 90% compared to the analytical and numerical results. Numerical modeling in Abaqus showed that the results at frequencies of 80 to 1800 Hz corresponded with acceptable accuracy and were able to simulate the vibration behavior of the system with low error. In the second section, the analysis of dynamic signs and spectral strain of the frequency response function signal was performed using wavelet transform and short-time Fourier transform methods. The results of this analysis showed that at a frequency of 255 Hz, there is a significant dynamic anomaly in mode 2 with a high quality factor (more than 25) and a strain in the range of 4.5 to 6.5, indicating the possibility of cracks, loosening, or stiffness changes in the structure. This anomaly is stable over time and is associated with mode interaction and nonlinear phenomena. https://stmechanics.bmtc.ac.ir/article_234707.html This study examines the influence of nanosilica incorporation on the mechanical and thermal performance of hybrid biocomposites composed of pine wood flour and recycled polypropylene. Composite formulations containing 50 wt% polypropylene, 50 wt% pine wood flour, nanosilica at four loadings (0, 3, 6, and 9 wt%), and 3 wt% maleic anhydride grafted polypropylene were compounded using a twin-screw extruder. Standardized test specimens were subsequently manufactured by injection molding. Mechanical properties—tensile and flexural strength and modulus, as well as notched Izod impact strength —alongside thermal behavior and flammability characteristics were evaluated. Increasing nanosilica content to 9 wt% resulted in reductions of 12.98% and 5.16% in tensile strength and tensile modulus, respectively. Flexural strength, flexural modulus, and notched impact strength also declined by 6.1%, 5.02%, and 10.92%, respectively. Conversely, the limiting oxygen index exhibited a 12.4% increase at the highest nanosilica loading, accompanied by higher residual char and improved thermal stability. Morphological analyses further showed fewer interfacial voids in specimens containing 3 wt% nanosilica, indicating superior fiber–matrix adhesion and reduced fiber pullout. Overall, nanosilica demonstrated a favorable contribution to the thermal performance of the composites, though excessive loading adversely affected mechanical properties due to nanoparticle agglomeration. The findings highlight the importance of optimizing nanosilica content to achieve a balanced enhancement of mechanical and thermal functionalities in bio-based polymer composites. https://stmechanics.bmtc.ac.ir/article_234712.html Gears are components that transmit rotational motion by engaging the gear teeth. Since gears are used in the power transmission system, their failure will lead to the mechanism failure. So, predicting failure factors is important to ensure a proper design. Tooth surface failure includes cases such as wear, pitting and spalling. Considering that experimental studies of fatigue phenomena are time-consuming and expensive, it is necessary to improve numerical models and bring them as close as possible to real conditions. The aim of this research is to present a numerical model to predict the subsurface fatigue crack initiation and growth under cyclic contact loading. In this study, Abaqus software was used for 2D modeling of a pair of teeth in contact. The analysis was performed using standard finite element method with progressive crack growth. The crack growth angle was determined according to the improved Richard criterion. The results showed that the maximum ΔKII position, with about 9% error, has the best agreement with the experimental spalling. So, the maximum ΔKII position was proposed as a criterion for determining the subsurface crack initiation position. The stress intensity factor of initial subsurface crack left and right tips is the same, and so, both tips start to grow simultaneously. In this model, the improved Richard criterion was used to determine the crack growth angle, which leads to the prediction of a spalling with dimensions close to the experimental spalling. The predicted spalling length showed a difference of about 6% compared to the experimental spalling. https://stmechanics.bmtc.ac.ir/article_229232.html This study investigated the improvement of mechanical and thermal properties in polypropylene matrix composites by adding glass fiber reinforcement. The results showed significant outputs in several tests. The addition of reinforcing particles resulted in a decrease in yield strain, while causing significant changes in yield strength. Charpy impact tests showed different energy absorption. This study investigated the effect of adding glass fibers with different L/D ratios (250, 300, 350) on the mechanical and thermal properties of injection molded polypropylene composites. The samples were produced by twin-screw extrusion and injection molding and tested according to ISO and ASTM standards. The results showed that the sample with 30% glass fibers (L/D=350) had the highest yield strength (98.6 MPa), impact energy absorption (14.1 kJ/m²), and thermal deflection temperature (151.7°C), and the shrinkage was reduced to 0.26%. These results indicate the potential of these composites for engineering applications with high dimensional accuracy. In addition, the addition of glass fibers resulted in a decrease in the melt flow index, while other particles showed the least effect. https://stmechanics.bmtc.ac.ir/article_234469.html Experimental investigation of workability of age-hardened Aluminum 7075 in ECAP process. Experimental investigation of workability of age-hardened Aluminum 7075 in ECAP process. Experimental investigation of workability of age-hardened Aluminum 7075 in ECAP process. Experimental investigation of workability of age-hardened Aluminum 7075 in ECAP process. Experimental investigation of workability of age-hardened Aluminum 7075 in ECAP process. Experimental investigation of workability of age-hardened Aluminum 7075 in ECAP process. Experimental investigation of workability of age-hardened Aluminum 7075 in ECAP process. Experimental investigation of workability of age-hardened Aluminum 7075 in ECAP process. Experimental investigation of workability of age-hardened Aluminum 7075 in ECAP process. Experimental investigation of workability of age-hardened Aluminum 7075 in ECAP process. Experimental investigation of workability of age-hardened Aluminum 7075 in ECAP process. Experimental investigation of workability of age-hardened Aluminum 7075 in ECAP process. Experimental investigation of workability of age-hardened Aluminum 7075 in ECAP process. Experimental investigation of workability of age-hardened Aluminum 7075 in ECAP process. https://stmechanics.bmtc.ac.ir/article_234713.html The scarcity of traditional fuel sources and its consequences have constrained global economic growth and social advancements, worsened environmental impacts, and hindered human empowerment. Therefore, the use of renewable energies is imperative to mitigate CO2 emissions and prevent global temperature rise and climate change. This article presents the latest technologies and advancements in renewable hydro, wind, solar, bio, geothermal, and marine energy applications. The deployment of renewable energies typically necessitates higher initial investment costs compared to non-renewable counterparts; however, with increased research and scientific development, these costs are diminishing. As renewable energy is integrated into the power grid expands, electricity prices decrease significantly throughout the day, sometimes reaching negative values. Subsequently, the percentage of electricity generated and the capacity factor (CAP) for electricity production using each renewable energy source are compared against total electricity generation and total CAP (renewable and non-renewable energies) in Iran, Asia, and globally during the 2015-2024 period. The results indicate that Iran possesses a high potential in renewable energy resources; however, their contribution to electricity generation is remarkably low compared with other Asian and Middle Eastern countries. Iran ranks fourth in the Middle East in terms of solar and wind energy use. Finally, the factors influencing the increased exploitation of renewable energies in Iran are discussed, and corresponding solutions are proposed. https://stmechanics.bmtc.ac.ir/article_235005.html The integration of solar energy into gas turbine cycles represents a promising approach to enhance system efficiency and reduce fossil fuel consumption. In this study, a single-shaft gas turbine–solar hybrid power plant is simulated under both design-point and off-design conditions and analyzed from energy and exergy perspectives. The model incorporates a compressor, turbine, combustion chamber, heat exchanger, and solar receiver, while the influence of key parameters such as compressor pressure ratio, turbine inlet temperature, and solar irradiation is investigated. The results reveal that solar energy utilization reduces fuel consumption and lowers exergy destruction within the combustion chamber. Off-design simulations further demonstrate that variations in rotational speed and solar irradiation significantly affect power output, fuel consumption, and overall efficiency. Increasing the compressor speed enhances the mass flow rate of air and requires additional fuel to maintain the air–fuel ratio, thereby increasing the output power but simultaneously raising fuel consumption and reducing thermal efficiency. https://stmechanics.bmtc.ac.ir/article_235415.html Flame flashback is a significant challenge in the design and operation of premixed burners, which can lead to serious damage to equipment. This phenomenon occurs when the flame speed exceeds the flow velocity of the gas, causing the flame to propagate back toward the burner nozzle. In this study, an innovative hybrid model based on physical criteria is presented for accurate prediction of flame flashback in methane-air mixtures. By combining the wall number criterion (W = 1.15 ± 0.08) and the Richardson number (Ri = 0.25 ± 0.03) along with an automatic calibration algorithm, the proposed model significantly improves prediction accuracy. The results demonstrate that the model can predict the probability of flame flashback with 92.3% accuracy across a wide range of operating conditions. The RMSE for flame speed prediction was measured at 0.23 m/s, and for flashback probability prediction, it was 7.2%. With a 45% reduction in prediction error compared to conventional models, this model offers an effective solution to address the challenge of flame flashback in combustion industries https://stmechanics.bmtc.ac.ir/article_235416.html استفاده از انرژی باد به‌عنوان منبعی پاک و تجدیدپذیر در دهه‌های اخیر توجه بسیاری از محققان را به خود جلب کرده است. در میان انواع توربین‌های بادی، توربین بادی ساونیوس به دلیل سادگی ساخت و توانایی عملکرد در سرعت‌های پایین باد، گزینه‌ای مناسب برای استفاده در مقیاس کوچک محسوب می‌شود. یکی از مسائل مهم در طراحی این توربین‌ها، اثر میله‌های هدایت‌کننده بر میدان جریان و عملکرد آیرودینامیکی روتور است. در این پژوهش، اثر میله‌ با مقطع بیضی و ضرایب منظر مختلف بر عملکرد توربین ساونیوس به‌صورت عددی و دوبعدی در نرم‌افزار انسیس فلوئنت بررسی شده است. شبیه‌سازی‌ها در حالت گذرا و با استفاده از مدل آشفتگی SSST K-ω انجام گرفت و اعتبارسنجی مدل از طریق مقایسه با داده‌های تجربی موجود صورت پذیرفت. نتایج نشان داد بیضی‌های با نسبت منظر بیشتر از 1 بهبود ضریب گشتاور و ضریب توان را سبب می‌شوند، به‌گونه‌ای که در نسبت منظر ۱.2 بیشترین بهبود توان به‌اندازه 23 درصد مشاهده شد. https://stmechanics.bmtc.ac.ir/article_236578.html In this study, the numerical study of the effect of wall temperature change on the suction of gas-fired boiler chimneys in residential buildings was investigated using two-phase flow in ANSYS Fluent software. The finite volume method was used to numerically solve the continuity, momentum, and energy equations, and the analysis was verified with previous works. Considering the high use of chimneys in residential buildings and the importance of proper chimney suction in the optimal use of gas-fired appliances and the exit of combustion products, the temperature of the wall and chimney insulation are of special interest. After ensuring the independence of the solution from the network, the results indicate that the speed of the combustion products exiting the chimney increases with increasing wall temperature. With a decrease in wall temperature, the buoyancy force due to the difference in density caused by the temperature difference decreases, and at the same time, the phase change from gas to liquid increases, which causes a decrease in the flow speed in the chimney, and as a result, the chimney suction decreases. Also, by reducing the wall temperature from 360 to 330 Kelvin, the difference in inlet pressure compared to outlet decreases by 23 percent, which indicates a decrease in chimney power. https://stmechanics.bmtc.ac.ir/article_236579.html In this study, using titanium (Ti), boron carbide (B4C) and reduced graphene oxide (RGO) powder precursors, a corrosion and wear resistant coating was created on 316L stainless steel alloy by laser method and its surface interaction properties were investigated. In this regard, initial tablets were made using reduced graphene oxide with percentages of 0.5, 1 and 3. The results showed that coating the surface of 316L steel alloy with Ti+B4C+1%RGO powder mixture can increase the corrosion resistance value up to 21 times compared to the 316L steel substrate and the surface hardness up to 2 times. Field emission scanning electron microscopy (FE-SEM) images showed that reduced graphene oxide nanosheets were effectively dispersed on the surface and titanium carbide TiC phase was formed on the surface after laser process. The deposition of a coating containing reduced graphene oxide nanosheets in a titanium matrix with a thickness between 2.545 - 2.37 μm on the surface of 316L steel has been identified as one of the most important reasons for increasing the surface properties of this alloy. The results of this research can enhance the scope of use of 316L steel in corrosion resistance and hardness applications. https://stmechanics.bmtc.ac.ir/article_236580.html the multi-stage edge combustion of super particles has been modeled, and the effect of changing the fuel type on the change in the triple flame propagation velocity has been considered; by introducing the effects of particle disintegration in the preheating zone for two states of uniform and random particle distribution, the temperature change profile of the particles has been obtained. the effects of heat dissipation in four states have been investigated, assuming the pyrolysis in a limit zone. The mass fraction conservation equations of gaseous fuel, solid fuel, oxidant and energy conservation were solved for the above four states. A suitable theory for triple flames in the limit of large activation energy (large β) and definite but small heat release (small α but non-zero) was presented using the parabolic flame path approximation for multi-stage edge combustion of super nanoparticles. analytical formulas were presented to determine the flame propagation velocity and triple flame curvature. The temperature, rate and reaction rates were expressed analytically. the effect of fuel changes from methane gas fuel to solid iron nanoparticle fuel was introduced. This fuel change shows that in an equal mixture fraction gradient; the triple flame propagation velocity is higher for methane gas fuel than iron nanoparticle fuel. with increasing fuel Lewis number from 0.4 to 2.5, the flame formation location gradually increases from 0.5003 at Lewis number 0.4 to -0.1233 at Lewis number 2.5. increasing oxidant Lewis number from 0.4 to 2.5, the flame formation location gradually increases from -0.0916 to 0.1985. https://stmechanics.bmtc.ac.ir/article_237107.html In this study, the influence of the swirl-collector diameter ratio on the cyclone particle separation efficiency and its pressure drop is examined numerically. The simulations were performed using ANSYS Fluent 2021. The diameter ratios investigated for the swirl collector are 0.25, 0.50, 1, 2, and 4. The fluid considered is air, with an inlet velocity of 1 m/s and a particle diameter of 10 μm. The results indicate that increasing the swirl-collector diameter ratio from 0.25 to 0.50 leads to a substantial reduction in pressure drop, while further increases in the diameter ratio cause the pressure drop within the cyclone to remain nearly constant. Additionally, the results show that the cyclone with a diameter ratio of 0.50 achieves 100% collection efficiency, whereas the cyclone with a diameter ratio of 4 is unable to separate the particles. Moreover, it was concluded that cyclones with equal swirl-collector diameters exhibit better performance than cyclones with other swirl-collector diameter ratios. https://stmechanics.bmtc.ac.ir/article_238259.html Shell-and-tube heat exchangers are widely used in energy, chemical, and HVAC industries due to their mechanical robustness, high thermal efficiency, and ability to withstand elevated pressures and temperatures. This study aims to enhance heat transfer performance while minimizing pressure drop by numerically modeling and optimizing the geometry of helical grooves inside the tubes of such heat exchangers. Thermo-hydraulic analysis was carried out using CFD simulations in COMSOL Multiphysics. Model validation against well-established empirical correlations confirmed the accuracy of the baseline model, with a deviation of less than 6%. The results show that increasing the depth and width of the helical grooves can enhance the heat transfer coefficient by up to 23%, although at the expense of a 20% rise in pressure drop. Finally, the developed model was optimized using a genetic algorithm. The optimization results indicate that the optimal geometry—groove depth of 2 mm, width of 1.5 mm, helix angle of 40°, and 20 grooves—improves the overall thermal performance by 25% compared to smooth tubes. https://stmechanics.bmtc.ac.ir/article_238616.html This study presents a comprehensive numerical analysis to investigate the impact of the air cavity depth in a Double-Skin Façade (DSF) integrated with Hybrid Photovoltaic/Thermal (PV/T) panels on the seasonal energy optimization of office buildings in Tehran's climate. The primary objective was to determine the optimal cavity depth to achieve minimal energy consumption and maximal utilization of solar energy throughout the year. For this purpose, a dynamic model of the system was developed using TRNSYS and MATLAB software, with real-world climatic data from Tehran employed as input boundary conditions. Within a parametric analysis framework, 22 different configurations with cavity depths ranging from 5 to 100 cm were evaluated. Key performance indicators, including heating and cooling loads, electrical energy balance (net production and consumption), and the reduction rate of carbon dioxide emissions, were calculated for each configuration. The simulation results demonstrated that varying the cavity depth has a significant impact on the system's thermodynamic behavior, including airflow patterns, heat transfer rates, and the overall efficiency of the solar system. Based on the results, the optimal cavity depth for Tehran's climatic conditions was determined to be 20 cm for warm seasons and 30 cm for cold seasons. Furthermore, increasing the depth to approximately 80 cm maximized electricity generation and reduced primary energy consumption by about 95% compared to the base case. https://stmechanics.bmtc.ac.ir/article_240032.html Overhead cranes are widely used in industrial applications, and among their various components, the wheels are critically important, as they account for the highest rate of failures. Given that these wheels are subjected to dynamic loading conditions, fatigue is the principal mechanism governing their failure and wear. This study investigated the effect of adding cylindrical slotted holes to the wheel wall on the distribution of static stress and the wheel's fatigue life. The objective was to maximize the hole diameter to minimize material usage and manufacturing costs, while maintaining acceptable performance and fatigue life within acceptable parameters. A 60-ton nominal capacity overhead crane wheel was selected for this investigation. Static loading on the wheel was simulated using the finite element method (FEM) to determine the effective stress and static safety factors in the regions where holes were added. To validate the numerical results, experimental load tests were also conducted on the crane wheel. Subsequently, utilizing the outputs from the loading simulation, a fatigue analysis was performed numerically using the Dang Van criterion to determine the wheel's fatigue safety factor. This process was iterated for cylindrical, slotted holes with diameters ranging from 10 to 70 mm. Furthermore, the requirements of international standards for overhead crane design were incorporated. The results indicate that, for an AISI 1045 steel wheel under the specified loading conditions, an optimal maximum hole diameter of 33 mm is achievable. This geometry yields a 9.8% reduction in material consumption while preserving operational safety and performance. https://stmechanics.bmtc.ac.ir/article_241177.html Development of high energy efficiency dryers is of great importance for the future of the drying industry. So in the present research, after applying an analytical two-dimensional solution on temperature and moisture content of the moist object, entropy production in the process of convective drying of an apple slice is studied with the second law of thermodynamics. The entropy production in fluid flow and moist object is computed and influences of aspect ratio of moist object and inlet temperature and velocity of fluid flow on the entropy production are analyzed. The result show that smaller aspect ratio produces less entropy; also by decreasing inlet temperature and velocity of fluid flow, the entropy production decreases too and by increasing inlet temperature and velocity of fluid flow, moist object will be dried sooner. So, respect to the amount of entropy production and final moisture content of the moist object, an optimized value for inlet temperature and velocity of fluid flow will be obtained. The effect of inlet temperature increase on the entropy production is more than inlet velocity increase. The study shows that the second law of thermodynamics is a potential tool for optimizing the drying process and dryers designing. https://stmechanics.bmtc.ac.ir/article_241181.html Gas turbines are widely used today as the most widely used type of turbomachinery in various industries including power generation, oil and gas, process power plants, aerospace, marine industries and even some domestic and small-scale applications. These cycles, which are considered the core of power generation and propulsion systems, have always been of interest to researchers because their optimization directly leads to reduced operating costs, increased energy sustainability and reduced environmental impacts. Key parameters in improving the performance of these cycles include increased thermal efficiency, exergy efficiency, reduced specific fuel consumption and reduced carbon dioxide emissions. In this study, advanced thermodynamic analysis and performance comparison of four distinct gas turbine cycle configurations including the basic Brayton cycle, the cycle equipped with heat recovery (recuperator), the cycle equipped with intercooler and the combined cycle of intercooler and recovery have been carried out using coding in the MATLAB environment. In this analysis, pressure losses in various components, changes in working fluid properties from air to combustion products, and the effect of increasing fuel mass on the outlet flow have been investigated. The results include accurate calculations of thermal efficiency, exergy efficiency, specific fuel consumption, output power, and carbon dioxide emission for each cycle and have been analyzed quantitatively and qualitatively using T-s and P-v diagrams. The findings show that the simultaneous use of recuperator and intercooler can increase thermal efficiency by more than 45% and exergy efficiency by about 39%, and significantly reduce fuel consumption and carbon emissions. https://stmechanics.bmtc.ac.ir/article_241185.html In this study, the water jet incremental sheet forming (WJISF) process of AISI 304 stainless steel sheets was experimentally investigated. The primary objective was to study the effects of key process parameters, including pump pressure, nozzle feed rate, sheet thickness, and the type of backing/support material, on the final characteristics of the formed part. A full factorial design of experiments (DOE) was employed to ensure accurate experimental planning, and the results were evaluated using analysis of variance (ANOVA). Experiments were conducted on sheets with thicknesses of 1 and 1.5 mm, using two different auxiliary materials to enhance the energy transfer of the forming jet. The experimental results showed that pump pressure and nozzle feed rate are the most influential parameters on forming depth. Specifically, increasing the pressure from 70 to 80 bar resulted in a 37% increase in forming depth, whereas increasing the feed rate led to a reduction in the final forming depth. Furthermore, it was found that the nozzle diameter and the type of backing material have a direct influence on surface roughness and wall flatness. The application of molten copper slag as a backing material reduced bottom thinning, while the use of sand resulted in a decrease in deformation depth. Overall, the results indicate that water jet incremental sheet forming is an effective, flexible, and non-contact sheet metal forming technique, which can be considered a suitable alternative to conventional mechanical incremental forming processes such as single-point incremental forming (SPIF) and multi-point incremental forming (MPIF). https://stmechanics.bmtc.ac.ir/article_242572.html The main source of energy consumption in evaporative coolers is the forced passage of air through wetted materials, which causes a significant pressure drop. In this study, to address this challenge and reduce the energy consumption of evaporative coolers, an innovative design with wetted surfaces was proposed, in which air flows parallel to the wetted surface instead of passing through it. To evaluate the proposed method, a laboratory prototype was constructed. Mathematical models predicting the effects of ambient temperature and airflow velocity on the performance indices of the cooler were developed using nonlinear multiple regression, based on experimental data obtained from field tests. Field experiments were conducted within an ambient temperature range of 15–32 °C and airflow velocities between 1–3 m/s. For validation of the obtained models, additional experiments under different conditions were performed, and the experimental results were compared with model predictions using statistical indices of coefficient of determination (R²) and root mean square error (RMSE). The results showed that both ambient temperature and airflow velocity affect performance indices through quadratic relationships. Cooling capacity improved with increasing ambient temperature up to about 25 °C, after which it declined. the highest cooling load within the experiments was around 1.7kW observed at the temperature of 23.5 °C with a velocity more than 3m/s. at such condition an effectiveness of 3.4 was achieved. Evaluation of the developed mathematical equations (R² > 0.98 and RMSE < 0.00532) revealed that the models accurately predicted the measured data. https://stmechanics.bmtc.ac.ir/article_242944.html Accurate solar energy generation forecasting is one of the main challenges in managing renewable energy systems due to the variable nature of solar radiation, dynamic weather conditions, and climate uncertainties. In this study, a comprehensive systematic review of 33 selected studies published between 2019 and 2025 was conducted to investigate the effectiveness of deep learning models in predicting solar energy generation. The main focus was on long-short-term memory (LSTM) networks and hybrid models, which have been widely used in recent years. The models were compared based on error evaluation indices including root mean square error (RMSE), mean absolute error (MAE), and mean absolute percentage error (MAPE). The results showed that hybrid models performed better in short-term forecasts, reducing the error by about 2.9%, while models equipped with attention mechanisms provided greater accuracy in medium- and long-term horizons. In addition, the use of multi-source data including local information, satellite imagery, and meteorological data improved the forecast accuracy by about 30%. Finally, the findings indicate a growing trend of using multi-level approaches, integrating diverse data, and making models smarter to improve reliability and sustainability in solar energy resource management. https://stmechanics.bmtc.ac.ir/article_244135.html The off-design performance of gas turbine–fuel cell hybrid systems, resulting from variations in operational conditions, remains a major challenge for their stable and optimal operation. This study aims to identify the optimal design point of a gas turbine–fuel cell combined cycle and to evaluate its behavior under off-design conditions, thereby quantifying performance degradation and system stability at varying loads. To this end, a multi-objective optimization was conducted, focusing on maximizing thermal efficiency, exergetic efficiency, and net power output, and the optimal point was selected as the design reference. Results indicated that at the optimal point, the thermal efficiency reaches approximately 65%, the exergetic efficiency about 57%, and the net power output around 33.4 MW. Subsequently, the system's off-design performance was analyzed using the gas turbine performance map while maintaining the fuel cell parameters at their optimal values. Findings reveal that reducing the rotational speed to 50% of its nominal value decreases the exergetic efficiency to approximately 50% and the net power to about 62.2 MW, whereas the highest efficiency occurs near the nominal speed. Moreover, the variations in power and efficiency remain consistent and free of unrealistic fluctuations. https://stmechanics.bmtc.ac.ir/article_244150.html Nanomaterials have gained a special place in materials science and advanced industrial applications due to their unique mechanical, electrical and thermal properties. In this review article, nanomaterials are classified into four categories based on structural dimensions: zero, one, two and three dimensions, and their mechanical behavior in the form of nanocomposites is investigated. The main focus is on carbon nanomaterials, including graphene and single-walled and multi-walled carbon nanotubes, as well as ceramic and magnetic nanomaterials such as TiO₂, Al₂O₃, SiO₂, Fe₃O₄ and Fe₂O₃. The mechanical properties, including Young's modulus, shear modulus and Poisson's ratio, along with the components of the elastic stiffness matrix, are analyzed within the framework of analytical and micromechanical models. In particular, the mixing law and the Halpin-Say model are used to predict the elastic behavior of nanocomposites, and the effects of parameters such as volume fraction, orientation, aspect ratio, and dispersion quality of nanoparticles are evaluated. Also, synthesis methods including sol-gel, co-precipitation, and chemical vapor deposition (CVD) are investigated for their effects on particle size, morphology, and uniformity. The results of the studies show that optimizing the interfacial structure and uniform distribution of nanophases increases the Young's modulus, tensile strength, and stiffness of the composite. In addition, considering nanoscale effects and modifying classical models with multiscale approaches significantly increases the accuracy of predicting elastic behavior. Finally, industrial applications in wear-resistant coatings, magnetic sensors, electromechanical systems, and aerospace industries are reviewed, and the challenges in dispersion and multiscale modeling are analyzed. https://stmechanics.bmtc.ac.ir/article_244153.html This study numerically evaluates, in three dimensions, the thermo-hydraulic performance of a fin-and-tube heat exchanger equipped with longitudinal vortex generators (LVGs). The objective is to quantify how vane shape enhances heat transfer while balancing the accompanying pressure drop, with emphasis on biomedical uses such as blood warmers and heat exchangers in life-support systems. Two LVG shapes—triangular and semi-cylindrical—were modeled and simulated under conditions spanning near-wall laminar up to transitional flow. The results show that the semi-cylindrical vane generates more persistent longitudinal vortices, promotes stronger near-wall mixing, thins the thermal boundary layer, and increases the average convective heat transfer relative to the triangular vane, albeit with a higher pressure drop. As the Reynolds number rises, heat transfer is strengthened and pressure loss increases; conversely, raising the inlet temperature of the cold stream reduces the wall heat-transfer coefficient. Within the operating range examined, the semi-cylindrical vane offers a more favorable heat-transfer/ pumping-power trade-off for compact biomedical heat exchangers. https://stmechanics.bmtc.ac.ir/article_244155.html In an era marked by increasing space object congestion and the challenge of tracking uncooperative or passive satellites, the development of independent and cost-effective orbit determination methods is essential. This paper presents a novel and operational methodology that integrates classical orbital dynamics with a genetic optimization algorithm to extract the six classical orbital parameters of a satellite using only the geographical coordinates of a limited number of its ground track points. The proposed method is entirely passive, eliminating reliance on active navigation systems like GPS or external databases such as TLE (Two-Line Element) sets. Implementation in MATLAB and evaluation on two simulated scenarios (a standard orbit and a polar orbit) demonstrated that with only ten observational points, the average relative error of the orbital parameters was reduced to less than 0.7% for the standard orbit and approximately 1% for the polar orbit. The results indicate the high capability of the genetic algorithm in converging to the optimal solution and its robustness against outlier data. This method serves as an efficient complementary solution for space situational awareness, identification of unknown satellites, and tracking of large space debris. https://stmechanics.bmtc.ac.ir/article_244466.html Inertial loads play an important role in structural design of Multirotors in vertical take-off of Recreational Manned-multirotor. In this paper a star layout for the support structure of motors and cabin of a manned recreational multirotor has been introduced. First the stress levels has been evaluated due to the maximum trust of motors using static finite element modeling. Afterward, time-dependent dynamic effects of applied motor loads have been investigated in take-off and Pull-up maneuvers on internal stresses using nonlinear dynamic finite element analysis. The effects of the pull-up maneuver as the most severe maneuver for this recreational multirotor have been studied within symmetric and unsymmetric conditions. The finite element results show that proper restrain of motors and inertial loads by the star layout leads to reduction of stress in unsymmetrical rather than symmetric pull-up maneuver. Moreover, performed frequency analysis in flight boundary conditions shows adequacy of the proposed star layout structure in the manner of natural frequency and motor working frequency (6.23 to 21.6 Hz). https://stmechanics.bmtc.ac.ir/article_244630.html Electrical Discharge Machining (EDM) is a vital manufacturing process for hard materials, particularly alloy steels, extensively utilized in mold making, aerospace, and automotive industries. In this study, the effects of discharge voltage, peak current, pulse-on time, and electrode material (copper vs. graphite) on the Material Removal Rate (MRR), Tool Wear Rate (TWR), and Surface Roughness of MO40 alloy steel were experimentally investigated. The experiments were designed using the Response Surface Methodology (RSM) with the Box-Behnken design, and regression models and Analysis of Variance (ANOVA) were employed to evaluate the main effects and interactions of the parameters. The results indicate that peak current has the most significant impact on the MRR, while discharge voltage and pulse-on time have the greatest influence on surface roughness. Furthermore, the TWR is primarily governed by the physical properties of the electrode; copper electrodes exhibit higher wear due to their high thermal conductivity. The optimization results revealed that the maximum MRR achieved was 0.010362 g/min (graphite electrode), the minimum TWR was 0.00000167 g/min (copper electrode), and the minimum surface roughness was 0.7695 μm (graphite electrode). Additionally, a thermal model for local heat flux, based on the radial distance from the spark center, was developed, yielding a maximum value of 6.688 MW/m² under conditions of 120 V, 8 A, and 100 μs.