Mechanic of Advanced and Smart Materials

Abstract Phononic crystals are a kind of advanced materials that are created by alternating arrangement of one or more inclusion materials in a different host material. In this research, the effect of the dimensional parameters of inclusions on the band gap of tungsten-rubber phononic crystal plate has been investigated. The shape of the inclusion under investigation is a hollow cylinder and the lattice type is square. The analysis of the above structure was done based on the finite element method and with aid of Comsol software. The band structures of the phononic crystals have been obtained for 10 different dimensions of the inclusion (inner and outer diameter of the hollow cylinder). The results showed that to achieve the widest band gap, the outer and inner diameters of the cylinder should be 4.5 and 3.77 mm, respectively. In this case, the band gap can be obtained from the frequency of 281.5 to 1076.5 Hz, and the total width of the band gap is 795 Hz.

Abstract This experimental study investigated the effect of machining parameters on the surface roughness of bone during the grinding process. Bone grinding is commonly used in neurosurgery, spinal operations, and heel spur removal. Despite using CNC machines and robotic systems in this field, selecting optimal process parameters to achieve desirable surface quality remains a significant challenge. In this research, bovine femur bone samples were subjected to experimental trials. Four parameters were examined, including spindle speed, feed rate, depth of cut, and tool diameter. The Sobol sensitivity analysis method was implemented using Python programming to assess surface roughness's sensitivity to these parameters. Subsequently, response surface methodology (RSM) in Minitab software was employed for results analysis and process optimization. The findings revealed that tool diameter, depth of cut, and osteon orientation had the most substantial influence on surface roughness. The optimum roughness value of 1.47 µm was obtained under specific conditions: spindle speed of 3000 rpm, feed rate of 60 mm/min, depth of cut of 0.1 mm, tool diameter of 8 mm, and across osteon orientation. The sensitivity analysis confirmed the dominant role of tool diameter in both longitudinal and across osteon orientations.

Abstract In the present study, the vibrational analysis of a three-layer sandwich plate with an auxetic core under aerodynamic forces with simply supported boundary conditions has been investigated. In this sandwich plate, the middle layer, or the so-called core, is made of auxetic material. The plate is subjected to aerodynamic forces on one side. To reduce the intensity of vibrations in the structure, the plate has been reinforced with carbon nanotubes. For the analysis and modeling of the plate’s vibrations, the modified shear deformation plate theories were employed, and the aerodynamic force exerted by the airflow on the plate was assumed based on first-order piston theory. Using Hamilton's principle, the governing equations for the vibrational behavior of the sandwich plate were derived, and the Galerkin weighted residual method was utilized to solve these equations. To demonstrate the validity of the obtained relationships and the proposed solution method, the results of this study were compared with results published in reputable journals and numerical solutions obtained using the finite element method through commercial software. Finally, the effects of various parameters such as the geometric dimensions of the sandwich plate, the dimensions of the auxetic core, aerodynamic pressure, and the volume fraction of carbon nanotubes on the vibrations of the structure were examined and analyzed.

Abstract In this article, research on the process of induction hardening on the Saina vehicle’s Tulip part, which is made of 1055 steel, was investigated. The input parameters discussed in this article include induction power, hardening time and cooling fluid pressure, and in the output parameter, surface hardness and effective case depth were investigated. Using the test design table extracted from the Minitab software and the analyzes performed with the response surface method, the mathematical and statistical equations governing the process were extracted, and using the analysis of variance table, the ineffective parameters of the process were removed and the final regression equation and other required information was extracted. Then the optimization of the process according to the desired values to achieve the desired surface hardness and effective case depth were done by providing a suitable range of induction power settings, induction time and cooling fluid pressure, which helped to reduce destructive tests and increase the quality assurance of parts.

Abstract The entry of air into hydraulic power systems presents a key challenge for both stationary and mobile machinery. Given the performance limitations of conventional online deaeration methods, this research was conducted to design, fabricate, and optimize an air-oil separator unit. To simulate the turbulent flow and the physical separation mechanism, a three-dimensional, two-phase numerical model was developed, integrating the Volume of Fluid (VOF) and Discrete Phase Model (DPM) approaches. A laboratory-scale hydro-pneumatic test rig was designed and fabricated to validate the numerical model. A comparison between experimental and numerical results revealed a discrepancy of approximately 2.5% for separation efficiency and 5.6% for pressure drop, thereby confirming the model's validity for analyzing the variables affecting the separator's performance. The results indicated that separation efficiency exhibits a non-linear behavior, with an optimal inlet velocity range of 3.5 to 5.5 m/s establishing a balance between high efficiency (87.5–90%) and an acceptable pressure drop (735–1150 Pa). Furthermore, the geometric analysis identified optimal ranges for key parameters. Accordingly, optimal values for the conical section angle (5–6°), cylindrical diameter (36–40 mm), and air outlet diameter (18 mm) yielded separation efficiencies of 89%, 90%, and 90%, respectively. These findings provide a quantitative and reliable framework for the optimal design of air-oil separators, demonstrating that an effective balance between efficiency and energy consumption can be achieved by selecting appropriate geometric parameters. The implementation of this approach is expected to enhance the reliability and service life of hydraulic systems significantly.

Abstract This paper investigates the effect of aerodynamic damping on the flutter threshold of a rectangular aluminum sheet in supersonic flow. Using matrix form of DQM and the first-order piston theory, this paper increses the accuracy and speed of the solution. Using the difference of squares method (DQM), two different scenarios of the first-order piston theory are analyzed: a simplified case without damping and a full case with damping. The results show that the flutter threshold occurs at Mach 3.395 in both cases, indicating that aerodynamic damping has no effect on the flutter velocity. This finding is confirmed by parametric sensitivity analysis. Accordingly, the simplified formulation of the piston theory is proposed as a computational basis for future studies. This method has computational advantages such as reduced computational time and is suitable for practical applications in the design of aerospace panels. this method can be a benchmark for future flutter researches.

Abstract In this paper, shape memory polymers (SMPs) are reviewed, as they have demonstrated exceptional properties that make them suitable as advanced materials for current and potential applications, particularly in robotics. However, the thermomechanical properties and traditional shape memory features are somewhat limited due to their ability to recover their original shape solely through the use of a heating source. SMPs not only possess remarkable mechanical and shape memory properties but also their ease of fabrication makes them suitable candidates for numerous applications. In this research, an artificial muscle equipped with a shape memory polymer is introduced, and its mechanical properties are measured and tested in a simple gripping and releasing mechanism. The results showed that the device is capable of performing cyclic loading and provides a force-to-energy ratio of 0.25. In future, the possibility of using this apparatus in robotic application such as surgical operation and crop harvester will be studied and evaluated.

Abstract In this study, the time-dependent behavior and stress relaxation of API-X42 seamless steel pipes reinforced with glass fiber composites were investigated to assess the effects of time on system stability and load-bearing capacity. A composite layer of E-glass fibers embedded in epoxy resin was applied to the pipe joint regions. Tensile tests were conducted in single-step and multi-step modes, with a 10minute hold at each stage, and the stress–time data were recorded in normalized form. The results indicated that lower loading rates promoted gradual stress relaxation and extended system stability, whereas higher rates led to faster stress release and attainment of a stable state in the early stages. Moreover, increasing the number of loading steps resulted in cumulative stress reduction and brought the system behavior closer to a quasi-stable state. At loading rates of 50, 100, and 200 mm/min, the final stress relaxation values were recorded as 8.9%, 7.7%, and 9.4%, respectively. These findings highlight the key role of resin viscoelasticity and stress distribution between fibers and steel in the mechanical stability of the system and underscore the importance of evaluating time-dependent behavior in the design and long-term performance prediction of reinforced steel pipes. The results of this study provide clear guidance for future research aimed at comprehensively investigating the effects of multi-step loading and ultimate failure mechanisms in steel–composite hybrid systems.