Mechanic of Advanced and Smart Materials

Abstract In this research, an attempt is made to repair copper parts that are widely used in industry, electrical appliances and etc. using melting method. This is very challenging and it causes defects such as in hot cracks, thermal stresses and residual stresses and in order to prevent these defects the friction method is used.in this research, in order to repair copper parts using friction process have been used in 3 different ways and after welding, welding has been investigated in term of hardness and stresses, metallographic properties and crystal structure. in order to examine the weld in terms of mechanical and metallurgical properties, the following test were performd:1-hardness test 2-tensile test 3-metallography 4-prepration of SEM images and elemental analyze of EDAX. 5-inspection of welding and check the lacks 6-surface quality after welding and repairing 7-performed the XRD test to check the crystal structure and check phase changes in welding were investigated and results were presented. The result of this research shows these parameters have straight effects on the quality and properties of welding, including, changing in distance between crystal plates and changing in crystal structure and increasing in hardness of welding surface because of friction of tool with the work piece and temperature increase at this position.

Abstract In this study, the effect of texture and morphology on the mechanical behavior of 316L stainless steel samples fabricated by selective laser melting was investigated using the crystal plasticity finite element method. To this end, four representative volume elements with varying grain aspect ratios were reconstructed based on the EBSD data obtained from the samples. The crystal plasticity constitutive relations were implemented into the ABAQUS software through a UMAT subroutine, and the representative volume elements were simulated under tensile loading. The results show that isotropic morphology leads to higher tensile strength on a macroscopic scale. Moreover, as the grain aspect ratio increases and the grains become more elongated, the tensile strength of the samples gradually decreases. Additionally, the stress distribution becomes more non-uniform with increasing grain elongation, and regions with stress concentration along the loading direction and at the boundaries of elongated grains increase. This study highlights the critical role of grain morphology in determining the mechanical behavior of polycrystalline materials. Furthermore, the proposed crystal plasticity finite element modeling approach provides an effective tool for accurately predicting the performance of materials manufactured through additive manufacturing methods, facilitating the exploration and development of new alloys and advanced materials.

Abstract In recent years, research on sandwich plates has increased due to capabilities such as energy absorption, strength to weight ratio, thermal insulation, and so on in major industries such as aerospace and marine industries. In this study, by using low-density aluminum foams and making sandwich planels by FML layers (including aluminum and composite sheets) and aluminum foam core, an experiment was carried out with the help of a high speed impact with gas gun, and the effect of density of foam, number of FML layers, velocity and mass of the projectile were investigated in terms of energy absorption of sandwich structures and ballistic limit of the projectile. Also, the results of empirical experiments on foam and composite layers, collision simulation and bullet penetration in a sandwich structure were performed using LS-DYNA software, and the results were compared and verified with experimental results. Experimental experiments and parametric studies show that aluminum foam (33%) and aluminum sheet (25%) have the highest energy absorption against the Bullet. Also, with the addition of a FML layer, the energy absorption of the sandwich plate increased by 40%.

Abstract This research aims to conceptually and optimally design a hybrid-electric octocopter to carry cargo or passengers. The drone uses a Wankel engine connected to an electricity generator to drive the brushless motors or charge the batteries. A genetic algorithm is employed to optimize the total weight and thrust force. The design variables include the engine power, fuel tank capacity, capacity and number of battery cells, brushless motor speed constant, speed controllers’ amperage, arm length, arms cross-section diameter, propeller radius, and propeller angular velocity. The engine’s mass-to-weight ratio is considered a key input parameter of the algorithm used to study the effect of technology on the final design. Two optimization objective functions are used: 1. maximizing the fuel-to-gross weight ratio and, 2. maximizing the thrust-to-weight ratio. Numerical results show that long flight ranges of order 1000 km are achievable with the designs presented by the first objective function, thanks to their large fuel capacity. According to our calculations, the overall performance of the octocopter configurations obtained by the second objective function with engine mass-to-power ratios of a=0.3 and a=0.6 (kg/kW) is very close. In other words, further advancement in Wankel engines’ mass-to-weight ratio does not result in considerable improvements in short-range VTOL vehicles.

Abstract One way to improve the mechanical properties of nickel-based superalloys is by controlling the grain boundary structure, particularly the twin boundary. Understanding the role of twin boundaries in deformation can help improve the mechanical properties of nickel-based superalloys. When the twin boundary in the nickel-based superalloy increases toughness, it is used in materials such as airplane wings, and landing gear, but when it increases the yield stress, it is used in turbine blades and discs. In this study, a molecular dynamics model simulates the tensile loading process of a nickel-based superalloy containing a twin boundary under three different loading orientations.The twin boundary is oriented parallel, inclined, and perpendicular to the loading direction. The results indicate that the yield strain values are 0.0479, 0.0478, 0.0453, and 0.0501 for samples without twin boundaries, with twin boundaries parallel, inclined, and perpendicular to the loading direction, respectively. The perpendicular twin boundary has resulted in an increase in the yield strain, while the inclined twin boundary has led to a decrease in the yield strain compared to the sample without the twin boundary. Also, the ultimate strains for samples without twin boundaries, parallel, inclined, and perpendicular are 0.08061, 0.10704, 0.095, and 0.06536, respectively. The ultimate strains are in the following order: parallel, inclined, no twin boundary, and perpendicular, respectively. Crack formation and growth at the highest strain occurred at points along the twin boundary and phase interface.

Abstract Metal matrix nanocomposites are materials with various and diverse properties that are somewhat controllable, and for this reason, there is today a growing effort to apply them in different industries. In this regard, significant research has been conducted to manufacture, develop, and improve their properties, leading to the creation of new methods for fabricating these materials. One such method is the modified stir casting process. In this study, based on the modified stir casting method, aluminum matrix nanocomposites of “A357” reinforced with alumina nanoparticles at weight percentages of 0.5%, 1%, and 1.5% were fabricated under different conditions such as cooling rate of the melt and alloy state. Properties such as hardness, tensile strength, yield strength, elongation at yield, elongation at fracture, Young’s modulus, fracture toughness, and work hardening were investigated. Based on the results obtained, it was found that adding alumina nanoparticles to A357 aluminum results in a nanocomposite with mechanical properties significantly superior to the base alloy. Among the nanocomposites fabricated under various conditions, the highest yield strength was observed in the nanocomposite reinforced with alumina nanoparticles at a weight percentage of 1%, and the best tensile strength was found in the nanocomposite reinforced with alumina nanoparticles at a weight percentage of 0.5% under conditions where the alloy was modified with an admixture in a semi-solid state and cast with a low cooling rate.

Abstract Considering the importance and high application of CK45 steel in today's industries and the increasing use of modern machining methods such as wire cut EDM, it is necessary to examine the effects of these methods' variables on the properties of metals. In this study, to enhance surface properties during the manufacturing process, cubic samples made of CK45 steel were fabricated using the wire cut method, and the effects of speed and current intensity variables on changes in surface properties including hardness, roughness, wear, and corrosion were discussed. The hardness and weight loss due to wear in the base sample were 218 HV and 18.51 mg, respectively, while in a sample with a manufacturing speed of 80 and a current intensity of 3 amps, these values reached 247.7 HV and 5.62 mg. The highest roughness was recorded in a sample with a manufacturing speed of 50 and a current intensity of 4 amps, and the best and worst corrosion results were observed at a speed of 50 and a current intensity of 3 amps and a speed of 50 and a current intensity of 4 amps, respectively

Abstract In the present investigation, the mechanical properties of mesenchymal stem cells (MSC) and carcinomatous cells of bone tissue (MG-63 and SAOS-2) has been studied applying AFM. Based on the sufficient similarity of mechanical characterizations of normal human osteoblast cells (NHOst) with mesenchymal stem cells (MSC), MSC have been applied instead to NHOst. Due to the outcomes, the elastic modules of MG-63 and SAOS-2 are lower than MSC. The elastic modulus of MG-63 and SOAS-2 cells were estimated before and after chemo and plasma treatment. MTT appraisal has been applied to define the convenient dosages for 24- and 48-h incubations due to the IC50 cell viability concentration. The elastic modules of MG-63 (917 Pa) and SAOS-2 (697 Pa) cell increase to 1.72 (1579 Pa) and 5.44 (4985 Pa) (after 24, 48 h) times compared to untreated MG-63 cell and 1.15 (802 Pa) and 7.49 (5225 Pa) (24, 48 h) times compared to untreated SAOS-2 cell. The plasma treatment increased the elastic modules of MG-63 and SAOS-2 cells. In the second section, the resonant frequencies and enlargement of the frequency response function of the AFM beam’s motions have been analyzed using FEM and experimental procedures by AFM. The outcomes displayed that raising the specimens’ hardness raises the resonant frequency. Lastly, the FEM and experimental outcomes have been evaluated and displayed the good agreement.