Amirkabir University of TechnologyAmirkabir Journal of Mechanical Engineering2008-603257420250622Detection and Evaluation of Core and Face De-bonding in Sandwich Composite Reinforced with Carbon Fibers Using Pulsed Heating Infrared Thermography MethodDetection and Evaluation of Core and Face De-bonding in Sandwich Composite Reinforced with Carbon Fibers Using Pulsed Heating Infrared Thermography Method401416581610.22060/mej.2025.24030.7833FAHamidPourbafraniComposite and Nanocomposite Research Laboratory, Faculty of Mechanical Engineering, University of Kashan, Kashan, IranAbolfazlAzimiComposite and Nanocomposite Research Laboratory, Faculty of Mechanical Engineering, University of Kashan, Kashan, IranAhmad RezaGhasemiComposite and Nanocomposite Research Laboratory, Faculty of Mechanical Engineering, University of Kashan, Kashan, Iran0000-0002-9326-4990BehzadMoslemi-AbyanehComposite and Nanocomposite Research Laboratory, Faculty of Mechanical Engineering, University of Kashan, Kashan, IranJournal Article20250405<span style="letter-spacing: .05pt;">The de-bonding of core and face is one of the most important defects created in sandwich composite materials during their manufacture and operation. In this study, the pulsed step heating thermography method was used to identify and evaluate core and face de-bonding in carbon fiber reinforced sandwich composites with foam core. For this purpose, the de-bonding defects between the core and the face were implemented in the samples during the manufacturing process. Then, using the pulsed step heating infrared thermography method, the location and number of these defects in the samples were identified. The desired parameters of this method, such as time step and heating rate, were obtained from the finite element modeling. By comparing numerical and experimental thermographic imaging results, the best time to record infrared images is predicted to be one second after the end of heating. Numerical results showed that with increasing thermal power and heating time, the temperature difference between the damaged area and its surroundings increased. Also, the numerical results were in good agreement with the experimental results, which can demonstrate the ability to detect the core and the face de-bonding defect in sandwich composite materials reinforced with carbon fibers and foam core using the pulsed heating thermography method</span>.<span style="letter-spacing: .05pt;">The de-bonding of core and face is one of the most important defects created in sandwich composite materials during their manufacture and operation. In this study, the pulsed step heating thermography method was used to identify and evaluate core and face de-bonding in carbon fiber reinforced sandwich composites with foam core. For this purpose, the de-bonding defects between the core and the face were implemented in the samples during the manufacturing process. Then, using the pulsed step heating infrared thermography method, the location and number of these defects in the samples were identified. The desired parameters of this method, such as time step and heating rate, were obtained from the finite element modeling. By comparing numerical and experimental thermographic imaging results, the best time to record infrared images is predicted to be one second after the end of heating. Numerical results showed that with increasing thermal power and heating time, the temperature difference between the damaged area and its surroundings increased. Also, the numerical results were in good agreement with the experimental results, which can demonstrate the ability to detect the core and the face de-bonding defect in sandwich composite materials reinforced with carbon fibers and foam core using the pulsed heating thermography method</span>.https://mej.aut.ac.ir/article_5816_ff1ced3097ccf17c1e67506cdad9ac95.pdfAmirkabir University of TechnologyAmirkabir Journal of Mechanical Engineering2008-603257420250622Optimum Walking Design for Biped Robots Based on the Improved Inverted Pendulum ModelOptimum Walking Design for Biped Robots Based on the Improved Inverted Pendulum Model417452582110.22060/mej.2025.23962.7829FAAbbasAzimiDepartment of Mechanical Engineering, Shahrood University of Technology, Shahrood, Iran.MostafaNazariDepartment of Mechanical Engineering, Shahrood University of Technology, Shahrood, Iran.S. MojtabaVaredi KoulaeiDepartment of Mechanical Engineering, Shahrood University of Technology, Shahrood, Iran.0000-0002-7427-2127Journal Article20250301The Spring-Loaded Inverted Pendulum (SLIP) model limits the controllability and mobility of biped robots in walking due to its omission of the ankle joint. This paper proposes a new walking pattern, titled "Optimized Step Design for Biped Robots Based on an Improved Inverted Pendulum Model," known as the Variable Spring-Loaded Inverted Pendulum with Finite-sized Foot (VSLIP-FF) model. Inspired by human walking characteristics, an adaptive strategy for leg extension and contraction is proposed for step planning, effectively emulating the role of the ankle joint. Finally, we examine the position and velocity of the robot’s center of mass with the VSLIP-FF model during walking on surfaces with varying friction. This stability and adaptability are crucial for the practical use of biped robots on diverse terrains. Simulation results for the model in the stated conditions show that it maintained stability on both flat and inclined surfaces with an 8% slope, exhibiting human-like behavior and achieving longer strides in a shorter time compared to the SLIP model. Friction conditions for the model on flat surfaces were also evaluated; based on this model’s parameters, if the friction coefficient is greater than or equal to 0.047, the friction between the robot's foot contact surface and the ground is static. Otherwise, it is classified as kinetic (sliding) friction.The Spring-Loaded Inverted Pendulum (SLIP) model limits the controllability and mobility of biped robots in walking due to its omission of the ankle joint. This paper proposes a new walking pattern, titled "Optimized Step Design for Biped Robots Based on an Improved Inverted Pendulum Model," known as the Variable Spring-Loaded Inverted Pendulum with Finite-sized Foot (VSLIP-FF) model. Inspired by human walking characteristics, an adaptive strategy for leg extension and contraction is proposed for step planning, effectively emulating the role of the ankle joint. Finally, we examine the position and velocity of the robot’s center of mass with the VSLIP-FF model during walking on surfaces with varying friction. This stability and adaptability are crucial for the practical use of biped robots on diverse terrains. Simulation results for the model in the stated conditions show that it maintained stability on both flat and inclined surfaces with an 8% slope, exhibiting human-like behavior and achieving longer strides in a shorter time compared to the SLIP model. Friction conditions for the model on flat surfaces were also evaluated; based on this model’s parameters, if the friction coefficient is greater than or equal to 0.047, the friction between the robot's foot contact surface and the ground is static. Otherwise, it is classified as kinetic (sliding) friction.https://mej.aut.ac.ir/article_5821_926c11cc055de9b8d697b6a587d40c4d.pdfAmirkabir University of TechnologyAmirkabir Journal of Mechanical Engineering2008-603257420250622Synergistic Effect of Rotating Magnetic Field and Ultrasonic Vibrations in Magnetorheological Abrasive Flow FinishingSynergistic Effect of Rotating Magnetic Field and Ultrasonic Vibrations in Magnetorheological Abrasive Flow Finishing453472582210.22060/mej.2025.24373.7862FAYahyaChoopaniDepartment of Mechanical Engineering, Meybod University, Meybod, IranMohsenKhajehzadehMechanical Engineering Department, Amirkabir University of Technology, Tehran, IranMohammad RezaRazfarMechanical Engineering Department, Amirkabir University of Technology, Tehran, IranJournal Article20250709This study employed rotating magnetic fields and ultrasonic vibrations as an effective solution to overcome the limitations associated with the magnetorheological abrasive flow finishing (MRAFF) process. To this end, first, an industrial prototype of the MRAFF setup was designed and fabricated. After preparing the magnetorheological polishing (MRP) fluid, a rotating magnetic field was applied, and subsequently, ultrasonic vibrations were applied to the workpiece in a direction perpendicular to the fluid flow. In order to evaluate the efficiency of the proposed technique, the effect of processing time on three indices, i.e., surface roughness rate, finishing rate, and material removal rate, in aluminum alloy 2024 tubes was investigated. The results indicated that during the first 10 minutes of processing, besides a decrease observed in the surface roughness ratio, the finishing rate and material removal rate also increased; however, due to the destructive effects of abrasive particles, the continuation of the process caused a re-increase in the surface roughness. Microscopic images not only confirmed these findings but also indicated that under optimal conditions, in addition to creating a uniform surface, the proposed technique reduced the roughness of the inner surface of the tubes by 98%. As a result, this method offers a promising prospect as an efficient solution for finishing and deburring inner surfaces, especially in longer tubes.This study employed rotating magnetic fields and ultrasonic vibrations as an effective solution to overcome the limitations associated with the magnetorheological abrasive flow finishing (MRAFF) process. To this end, first, an industrial prototype of the MRAFF setup was designed and fabricated. After preparing the magnetorheological polishing (MRP) fluid, a rotating magnetic field was applied, and subsequently, ultrasonic vibrations were applied to the workpiece in a direction perpendicular to the fluid flow. In order to evaluate the efficiency of the proposed technique, the effect of processing time on three indices, i.e., surface roughness rate, finishing rate, and material removal rate, in aluminum alloy 2024 tubes was investigated. The results indicated that during the first 10 minutes of processing, besides a decrease observed in the surface roughness ratio, the finishing rate and material removal rate also increased; however, due to the destructive effects of abrasive particles, the continuation of the process caused a re-increase in the surface roughness. Microscopic images not only confirmed these findings but also indicated that under optimal conditions, in addition to creating a uniform surface, the proposed technique reduced the roughness of the inner surface of the tubes by 98%. As a result, this method offers a promising prospect as an efficient solution for finishing and deburring inner surfaces, especially in longer tubes.https://mej.aut.ac.ir/article_5822_fd2ae8ec902471d8956fca3486031013.pdfAmirkabir University of TechnologyAmirkabir Journal of Mechanical Engineering2008-603257420250622A Numerical Study on the Influence of Geometric Parameters on Tesla Valve Performance within an Automatic Recirculation Control Valve SystemA Numerical Study on the Influence of Geometric Parameters on Tesla Valve Performance within an Automatic Recirculation Control Valve System473496582410.22060/mej.2025.24217.7851FARafatMohammadiDepartment of Mechanical Engineering, Arak University, Arak, IranArsalanRajaeiDepartment of Mechanical Engineering, Arak University, Arak, IranNaserMeyghaniDepartment of Mechanical Engineering, Arak University of Technology, Arak, IranJournal Article20250603In this study, the performance of a Tesla valve, integrated into Automatic Recirculation Control valves used in industrial applications, is investigated through numerical simulation. The primary objective was to analyze the influence of key geometric parameters of the valve on flow characteristics, including flow rate, pressure drop, and cavitation phenomena. The governing equations were solved using the finite volume method in ANSYS CFX, and the numerical results were validated through comparison with experimental data. The parametric study was conducted in two phases. In the first phase, under a constant pressure drop, the effects of body diameter, stage diameter, stage angle, and the number of stages on flow rate were examined. The results indicated that increasing the diameter and reducing the stage angle can enhance the flow rate by up to 45%, whereas variations in the number of stages had minimal impact on flow rate. In the second phase, the effects of the aforementioned parameters were assessed under varying pressure drops. These results also revealed a direct correlation between pressure drop and flow rate, with trends consistent with the first stage. The findings of this study provide valuable insights for the optimal and customized design of Tesla valves in Automatic Recirculation Control systems, contributing to enhanced efficiency and reduced energy losses in industrial pumping applications. In this study, the performance of a Tesla valve, integrated into Automatic Recirculation Control valves used in industrial applications, is investigated through numerical simulation. The primary objective was to analyze the influence of key geometric parameters of the valve on flow characteristics, including flow rate, pressure drop, and cavitation phenomena. The governing equations were solved using the finite volume method in ANSYS CFX, and the numerical results were validated through comparison with experimental data. The parametric study was conducted in two phases. In the first phase, under a constant pressure drop, the effects of body diameter, stage diameter, stage angle, and the number of stages on flow rate were examined. The results indicated that increasing the diameter and reducing the stage angle can enhance the flow rate by up to 45%, whereas variations in the number of stages had minimal impact on flow rate. In the second phase, the effects of the aforementioned parameters were assessed under varying pressure drops. These results also revealed a direct correlation between pressure drop and flow rate, with trends consistent with the first stage. The findings of this study provide valuable insights for the optimal and customized design of Tesla valves in Automatic Recirculation Control systems, contributing to enhanced efficiency and reduced energy losses in industrial pumping applications. https://mej.aut.ac.ir/article_5824_b7f520a55897b35e6eb462bbf80915c6.pdfAmirkabir University of TechnologyAmirkabir Journal of Mechanical Engineering2008-603257420250622Dynamic Progressive Buckling of Thin Wall Foam-Filled Conical Tubes Under Impact LoadingDynamic Progressive Buckling of Thin Wall Foam-Filled Conical Tubes Under Impact Loading497520582610.22060/mej.2025.24158.7845FASaeedFeliDepartment of Mechanical Engineering, Razi University, Kermanshah, Iran0000-0003-0638-2380ErfanMakhsoosDepartment of Mechanical Engineering, Razi University, Kermanshah, Iran.Seyed SajadJfariDepartment of Mechanical Engineering, Hamedan University of Technology, Hamedan, Iran0000-0002-9155-592XJournal Article20250515Energy absorbers are of particular importance today due to their extensive application in industry, and they are recognized as key elements in enhancing safety and reducing damage resulting from impact. These absorbers dissipate the impact caused by axial loads through plastic deformation and buckling. In this paper, the impact loading on foam-filled grooved conical absorbers has been investigated using analytical and numerical simulation methods. Initially, a novel analytical model for calculating the mean crushing force and the amount of energy absorption in absorbers is presented. This model is based on elastic and plastic energy absorption, which includes hinge bending and deformation between hinges. Numerical simulation of progressive dynamic crushing in these absorbers has been performed using Abaqus, and the results have been compared with the analytical model and experimental results. The aim of this comparison was to evaluate the accuracy of the analytical model in predicting the actual behavior of the absorbers. Finally, the effect of various parameters such as cone angle, number of grooves, and foam density of the absorber on the amount of energy absorption has been investigated. The results of this investigation can be a useful guide in the optimal design of this type of energy absorbers.Energy absorbers are of particular importance today due to their extensive application in industry, and they are recognized as key elements in enhancing safety and reducing damage resulting from impact. These absorbers dissipate the impact caused by axial loads through plastic deformation and buckling. In this paper, the impact loading on foam-filled grooved conical absorbers has been investigated using analytical and numerical simulation methods. Initially, a novel analytical model for calculating the mean crushing force and the amount of energy absorption in absorbers is presented. This model is based on elastic and plastic energy absorption, which includes hinge bending and deformation between hinges. Numerical simulation of progressive dynamic crushing in these absorbers has been performed using Abaqus, and the results have been compared with the analytical model and experimental results. The aim of this comparison was to evaluate the accuracy of the analytical model in predicting the actual behavior of the absorbers. Finally, the effect of various parameters such as cone angle, number of grooves, and foam density of the absorber on the amount of energy absorption has been investigated. The results of this investigation can be a useful guide in the optimal design of this type of energy absorbers.https://mej.aut.ac.ir/article_5826_99f42c473afe0eb4bd047ae133b851fc.pdfAmirkabir University of TechnologyAmirkabir Journal of Mechanical Engineering2008-603257420250622Experimental and Numerical Investigation of the Effects of Metal Fibers on Heat Conduction in Phase Change MaterialsExperimental and Numerical Investigation of the Effects of Metal Fibers on Heat Conduction in Phase Change Materials521542583010.22060/mej.2025.24293.7855FAMohamadJowziDepartment of Mechanical Engineering, Faculty of Engineering, Razi University, IranJafarJamaatiDepartment of Mechanical Engineering, Faculty of Engineering, Razi University, Iran0000-0002-1949-6240Journal Article20250702Several methods have been proposed to enhance the thermal conductivity coefficient of phase change materials. In this study, the effect of incorporating metallic fibers on the enhancement of thermal conductivity in PCMs is investigated through both experimental and numerical approaches. The impact of fiber material, diameter, length, and volume fraction on the conductive heat transfer performance of PCMs has been investigated. Experimental results demonstrate that the addition of a small volume fraction of metallic fibers (approximately 2%) can improve the thermal conductivity of PCMs by up to four times. In two identical experimental setups, replacing steel fibers with copper fibers resulted in a 55% increase in thermal conductivity. The numerical results indicate that increasing the volume fraction of fibers from 2.35% to 3.9% leads to an improvement of more than 50% in the effective thermal conductivity. On the other hand, increasing the orientation angle of the fibers by 15 degrees relative to the direction of heat flow results in a 31% decrease in thermal conductivity. This study also presents a novel approach for evaluating the microstructure of fibrous composites and determining their effective thermal conductivity.Several methods have been proposed to enhance the thermal conductivity coefficient of phase change materials. In this study, the effect of incorporating metallic fibers on the enhancement of thermal conductivity in PCMs is investigated through both experimental and numerical approaches. The impact of fiber material, diameter, length, and volume fraction on the conductive heat transfer performance of PCMs has been investigated. Experimental results demonstrate that the addition of a small volume fraction of metallic fibers (approximately 2%) can improve the thermal conductivity of PCMs by up to four times. In two identical experimental setups, replacing steel fibers with copper fibers resulted in a 55% increase in thermal conductivity. The numerical results indicate that increasing the volume fraction of fibers from 2.35% to 3.9% leads to an improvement of more than 50% in the effective thermal conductivity. On the other hand, increasing the orientation angle of the fibers by 15 degrees relative to the direction of heat flow results in a 31% decrease in thermal conductivity. This study also presents a novel approach for evaluating the microstructure of fibrous composites and determining their effective thermal conductivity.https://mej.aut.ac.ir/article_5830_e520f70ac3930490458892665cda6620.pdf