مجله مهندسی مکانیک
سال پنجاه و یکم شماره 1 (پیاپی 94، بهار 1400)

Vibrations due to backlash and other nonlinear effects is a common problem in industries with power transmission systems with gear. Various dynamic models show chaotic behavior in power transmission systems that use spur gears. The aim of this study is to control the chaotic behavior in spur gear transmission system by transferring the system onto an existing unstable periodic orbit and tracking the trajectory using sliding mode control. The proposed model in this study considers a pair of spur gears with time dependent stiffness, backlash and static translation error. Firstly, the dynamic equations are extracted and the effect of model parameters on system response are indicated by simulation results. Then using Poincare’ map and an efficient algorithm, the unstable periodic orbit is detected. Finally, the sliding mode controller is designed to track the desired trajectory obtained from the unstable periodic orbit. The simulation results show the performance of the proposed controller.

In the present article, the impact of the loading rate on tensile features of the piston aluminum-silicon alloy, with and without silica nano-particles has been studied. Tensile tests were performed on casted specimens at different loading rates. Then, obtained experimental data were analyzed by the Minitab software, for the sensitivity analysis to find the effect of the loading rate on tensile properties. Results showed that in samples without silica nano-particles, the yield stress and the elongation of the material increased and decreased, respectively; when the loading rate increased. Microstructure images indicated that silica nano-particles were embedded to the silicon element. As a result, higher values of the silicon element were found in the aluminum matrix. However, the size of silicon particles was smaller in the nano-composite. The fracture surface illustrated that by increasing the loading rate in tensile testing and by the addition of silica nano-particles, the brittleness of the material increased.

In this paper, the adaptive robust tracking problem is solved for the sandwich systems with non-smooth nonlinear saturation function in the presence of uncertainties and external disturbances. Sandwich systems are a class of nonlinear systems, such that the non-smooth nonlinear functions are sandwiched between their distinct subsystems. This article studies on sandwich systems include two nonlinear subsystems with the nonlinear saturation function located between the subsystems. Due to features like the lack of invertibility and non-smoothness of the saturation function, as well as the existence of unknown gains and external disturbances, analysis and design process for the mentioned systems face with complexities. In this paper, an adaptive robust controller is proposed by using the backstepping control approach and its combination with the Nussbaum function, based on the Lyapunov theory to achieve the control objectives. In order to verify the theoretical achievements as well as, the efficiency of the proposed method, it’s applied to a mechanical system consists of a one-link manipulator that is handled with a DC motor. Simulation results show the effective performance of the proposed approach in the tracking of the time-varying reference signal in the presence of unknown terms, external disturbances and sandwiched saturation function between subsystems.

Solar collectors are among the most widely used equipment for solar energy storage, in which solar radiation energy is transferred to the internal energy of a transferring material, but this equipment can rarely fulfill thermal needs due to the solar time and energy requirement. Therefore, this paper proposes the use of phase change materials (PCM) in the collector to improve thermal storage and prevent energy loss. The main objective of this study is to investigate phase change materials (PCM) slurry fluid flow inside a solar plate and to evaluate its performance. In order to evaluate the performance of the solar collector with this fluid, a solar sheet containing phase change material is simulated in Comcast software. A numerical analysis conducted with Comsol Multiphysics Software is presented to obtain a preliminary evaluation of the performance of the proposed concept. The numerical results show that these materials can effectively improve solar collector performance.

Employment of optimized fuel injected motorcycle rather than carbureted ones is a key to reduce pollution. This article studies a 150-cc fuel injected motorcycle, where its engine management unit (ECU) data are optimized, using genetic algorithm and the least squares method, in order to operate at the optimal engine operating points. The ECE40 driving cycle is employed, and the output torque and CO emissions are studied as the objective functions during the optimization procedure. The motorcycle model and the controller models are presented. Simulation results as well as the experimental ones show a reduction of CO by about 20%, CO2 by 5%, HC by 19%, and NOx by about 1%. Moreover, the output torque is increased by about 12%. According to the emission test results, the motorcycle is able to pass the Euro-3 standard. The proposed optimization technique provides a solution to have an optimal ECU for a specific application.

The design and construction of aircraft wings with optimal geometry and physical properties that are highly stable is of high importance to engineers. In this study, with the assumption of uncertainty in system design variables, a robust optimization of the Flutter velocity aeroelastic wing with high-aspect-ratio under the bending-torsion effect is examined with the standard deviation minimization. Therefore, the aeroelastic wing are firstly modeled based on the Euler-Bernoulli cantilever beam model in quasi-steady aerodynamic conditions. After validating the results, in the simulation section, by using the 4th Runge-Kutta numerical solution and the theory of Eigenvalues, the system response time and Flutter velocity are obtained. In the high-aspect-ratio wings, increase the Flutter velocity in the presence of uncertainty in the parameters is important. Therefore, by choosing parameters such as bending and torsional rigidity and mass per unit wing as optimization variables the effect of uncertainty on the design variables and optimized by genetic algorithm. In addition, the values of variables before and after optimization, as well as the rate of improvement of the Flutter velocity are presented in a robust and deterministic optimization. Finally, based on the optimization results, design variables for achieving an appropriate stability structure in terms of the phenomenon Flutter is confirmed.

This paper is carried out the free vibrational behavior of functionally graded polymer composite annular and circular plates reinforced with graphene nanoplatelets (GPLs) using three-dimensional elasticity theory. The weight fraction differs gradually across the thickness direction. Effective elasticity modulus of the nanocomposite has been estimated by the modified Halpin-Tsai model. Five different GPLs distribution patterns within the polymer matrix are considered.  State space first order differential equation by employing the equation of motion and constitutive relation within the framework of three-dimensional elasticity theory across the thickness direction is derived. Present approach is validated by comparing the numerical results with those reported in the literature. Influence of outer radius to thickness ratio, different GPL distribution patterns, GPLs loading and edge boundary conditions on the vibrational behavior of GPLs reinforced composite (GPLRC) circular/annular plates are studied. The results implied that GPLs with a low content can have an excellent influence on the natural frequencies of the circular and annular plate.

In this paper, dynamic model of r cooperative manipulators with n_m links derived by using recursive Gibbs-Appell formulation. Object grasped fully constrained by the manipulator’s end effector and manipulators transport the object simultaneously. For computing the system equations, first the object and manipulators dynamic equations developed independently. Therefore, by preparing the constraint equations, the end effectors and object inter connection forces and torques omitted for the constrained equations. By arranging these equations, the final form of motion equations in joint space evaluated. Next, the forward dynamic equations simulated by MATLAB software and compared with ADAMS software. For inverse dynamic solution, with considering the joints redundancy, two proper solution selected among appropriated one. In the first case, the solution chosen by considering the force extracted on the object by the manipulators. While, the force only cause the object manipulation and omitted the object internal force and stress. For the second one, optimum torques computed using Lagrange multiplier method and defining a cost function with assuming the arbitrary energy distribution between manipulator’s joints. At the end, the dynamic load carrying capacity calculated in all methods.

Nowadays, CCHP cycles receive more attention due to high efficiency and low pollution. In this regard, a novel CCHP cycle has been proposed. This cycle combines gas turbine, ORC, HRSG, single effect, and double effect absorption refrigeration cycles. The prime mover of the ORC is the geothermal energy and the waste energy of this is used to run the single effect absorption cycle. The gas turbine cycle is fueled by natural gas and the exhaust gases of this provide energy to operate HRSG and the double effect absorption cycle. The purpose of this CCHP is to reduce dependence on natural gas while increasing (or constant) power production. For thermodynamic modeling and validation, a code has been developed in the EES software. This cycle has 32.8 MW power production, 37.1MW heat generation, and 4.6 MW cooling capacity and the EUF of the cycle is 60.5%. In addition, the fuel consumed by the gas turbine cycle is reduced by 1.20% while keeping constant power production. Also, parametric studies show that the inlet temperature of the gas turbine has the most influence on the EUF.

The purpose of present paper is numerical study of the effect of pure fluid (water, air and ethilen glicon) on flow field and heat transfer rate of a cavity contatining nano fluid and pure fluid which separated with an obstacle. we used water-copper oxide as nano fluid. governing equations are derived based on volume controll method and solved base on SIMPLE method together. results show that, increasing Grashof number will cause rise of flow speed and heat transfer rate in cavity. in ( , ) Grashof numbers, conduction is the dominated heat transfer and with increasement of Grashof number ( , ), mechanism changes from conduction to convection. in cavity containing air-nano fluid, the strength of vorticities in cavity containg air () is greater than the nano fluid one (). while in the cavity containing nano fluid-ethilen glicon (), vorticity strength is greater in cavity containing nano fluid (). in low Grashof numbers, heat transfer rate on hot wall, while the pure fluid is air (95.77%), is greater than ethilen glicon (70.34%) and ethilen glicon is greater than water (50.14%). in high Grashof numbers heat trasnfer rate on hot wall, while the pure fluid is ethilen glicon (67.33%), is greater than air (56.41%) and air is greater than water (50.93%). while in all Grashof numbers heat transfer rate on cold wall,

In this study, by using signal processing methods, the propagation behavior of the waves in a GF/EP composite plate is practically investigated, and the propagated wave signals variations is analyzed as well. First, multiple paths of signal propagation was designed, based on a network of piezoelectric transducers, which have a dual role of excitor and sensor, which demarcates the plate into four areas, comprsing healthy, with delamination, hole and notch areas. Then by defining two types of damage indexes, under the concept of wavelet transform, the extraction features of the signals associated with each of the four areas in 40 directions and 9 conditions are compared. In the final step, the effect of each damage on the signal waves, by applying the numerical values of the damage indexes, at the joint time and frequency domain, was studied. The results show that by the proposed method, it is possible to detect and distinguish the wave behavior analysis affected by different damages in the structure; furthermore, it is a reasonable and convenient alternative technique for the conventional nondestructive testing.

In this research, convective heat transfer in a flow over rotating elliptic cylinders with various axis ratios and rotation rates is investigated numerically. The governing equations including continuity, momentum and energy equations are solved by numerical finite element method. The rotating cylinder was assumed at a constant temperature and heat dissipation to the flow was defined. Numerical analysis was performed by means of COMSOL Multiphysics software. Two domains were defined in the geometry, the rotating one with constant velocity and the second one was assumed to be stationary and the domains are paired to each other. The heat transfer rate and streamlines are obtained for all cases. The unsteady flow is studied when the cylinder starts to rotate suddenly. The results indicate an increase in heat transfer by increasing the rotational ratio. In the higher rotational ratios, the vortices in rotational path of the solid wall are removed and immediately transferred to the edge of the cylinder. In terms of the ratio of heat transfer to drag force, rotating cylinder with axis ratio of unity is the best one.

In the present work, the effects of the blade installation angle of a two-stage axial turbine on its performance are investigated  numerically. The geometrical specifications of the General Electric MS5001 gas turbine are selected for the study. First, the turbine geometry is created and gridded, and the final model is generated by the combination of the gridded blades. In order to calculate the effect of the wall on the turbulent flow, the Shear Stress Transport (SST) turbulence model is used. First, the acquired results from the studied turbine are compared with the available data from the power plant which showed a good agreement. Then, to investigate the effects of the blade angle on the performance of the turbine, the angle of each row from the four rows of turbine blades is changed in each step, and the obtained results are compared with the results of the turbine original model. Increasing the installation angle of stator blades in the second row and decreasing the installation angle of rotor blades in the second row lead to increasing the produces power and efficiency of the turbine. The acquired results show that the produced power is increased by 4% and the turbine efficiency is increased by 0.87% in the best-optimized arrangement of blades.

In this study, the behaviour of biosensors is investigated by using the modified coupled stress theory. The biosensor is electrostatically stimulated and also immersed in the fluid. Unlike previous studies, in the present study, the size effect parameters, surface layer, and intermolecular Casimir force are considered simultaneously. In order to solve the nonlinear static equation, the Modified Adomian Decomposition (MAD) method and the numerical method are used. Finally, the effect of the length of the material and also the effect of stress on the pull-in voltage is studied as well. Comparing the results of the Adomian analytical solution with numerical methods and reported results in the literature, show that the method has high accuracy and can be used as an effective and efficient method for analyzing the stability of Nano-bio sensors. The results indicate that by considering the surface effect and also increasing the size effect parameter, the pull-in voltage in both numerical and analytical modes is more than the situation which surface effect is neglected. In addition, with the presence of the surface layer and the increase of the Casimir force, the pull-in voltage is reduced.

In the present study, a particular model of parabolic solar collectors, SEGS LS2, has been numerically studied. Generally, solar thermal collectors are divided into two general concentrators and none concentrators, the SEGS LS2 model being concentrated so that it reflects sunlight on its focal point and Together parabolas and moving a fluid from the focal point absorbs the radiant heat of the sun. The heat absorbed into the operating fluid (Syltherm oil 800) is transferred to the thermal system. The study compares the input speed of the heat transfer pipe, which is composed of Syltherm 800 oil. So that the average speed of the pipe inlet constant, but with the secondary slopes enter the particle collector. To create these intermittent bursts, a step-sine input is used such that, by applying this boundary condition, the velocity changes instantaneously (non-stable) and causes more turbulence of the carrier of the heat. The results of the study indicate an increase in the Thermal efficiency under the stepwise-sinus input boundary conditions. Thus, this variable has a 22% increase compared to the constant speed input.

A novel type of actuator based on the magnetostriction phenomena is proposed. This model consists of a cantilever beam made of steel which is laminated with Metglas 2605sc as the magnetostrictive material. The beam deflects while it is located in a magnetic field, because of the shape changes in the magnetostrictive layer. This beneficial deformation can be used to design an actuator. The nonlinear Euler-Bernoulli beam theory is implemented by means of newton’s second law. The dynamic response of the proposed model of the actuator beam and specially the relation between the position of the beam tip under the influence of magnetic field and also the effect of the damping coefficient on the transient response and stabilization of the tip of the beam, which is assumed to be end effector, are obtained. The proposed model in this paper needs no connections and driving instruments and can be used remotely, moreover achieved nonlinear dynamical equations in this study can be used as a design tool for these kinds of actuators.

The heat exchanger is one of the most important parts of the Altitude Engine Test Facility. In this regard, it is necessary to identify the Air-Cooled heat exchanger to optimally use the ambient temperature conditions. In this study, after designing, thermal heat exchanger simulation was performed. The ultimate goal is to identify the performance of this heat exchanger for the specific conditions of high temperature and low pressure of this system based on the sizes provided by the design software Aspen and HTRI and simulation results of ANSYS CFX. The design accuracy of this study was carried out in two ways. At first, the validity of the computational model was confirmed by reference to experimental results from a similar geometry. Then, the results of two designing software were compared with the computational fluid dynamics method which validated in the previous step. The results showed that the design was suitable and can provide the required heat transfer for the most critical current flow of high temperature gases in 650 °C and 50 mbar pressure which was based on actual conditions. The results of the study confirmed the temperature of 50 °C at the output of the designed heat exchanger. In addition, the pressure drop for hot gases on the pipe side after passing through 3 passes in critical operating condition was found to be close to 5% of inlet pressure.

In this article, the failure of gearbox transfer of steel mill ingot in the company of Iran National Steel Group is studied. This shaft receives power from the electromotor and it’s inside another hollow axis. The shaft, power to rotate the ingot transfer roller by a spiral gear transmits to another axis. The roller make this system an important part of the ingot production line. This shaft many times will failure and replace it is a huge loss to the factory. Due to lack of the fundamental information about the map and kind of shafts after failure, measurement quantum were performed to determine the type of alloy-axis and to make the piece which these pieces have a short working life span and after undergoing loading, they were fractured. To find the causes of failure, the shaft was modeled in the Solid works software and it was inserted into the Ansys Workbench software for stress analysis. After using boundary conditions and loading, the Points that were susceptible to failure were identified. Also the conditions and defects that could lead to failure were analyzed. Finally to estimate shaft fatigue life, fatigue models were used and to improve the life of the piece suggestions and solutionswere presented.

In this study, in order to waste heat recovery from a marine diesel engine, a humidification – dehumidification desalination unit type of open – water and closed – air cycles with water heated is proposed for producing the consumed fresh water the crew of the ships. The energy required to produce freshwater is provided by recovered heat from exhaust gases from marine diesel engine. For this proposed system, first simulated thermodynamically and detailed energy and exergy analysis, in order to determine the main sources of irreversibility and performance characteristics of the system is conducted. Moreover, a comprehensive parametric study to find key parameters trend with system performance parameters is carried out. The study found that the system has the ability to produce 0.2746 kg.s-1 fresh water, using 432 kW of primary energy. As well as desalination efficiency and exergy efficiency were calculated to be 1.516 and 23.9%, respectively. And from an exergy analysis it can be seen that among all the components of the system, the heater has the highest exergy destruction rate, which accounts for about 73.2% of the total exergy destruction rate.

In this study, the kinematics and dynamics of a plane direct-guided cable robot with three degree-of-freedom and the control of its direction have been studied and investigated. First, the tensile of the cables has been investigated regarding that the robot is a closed kinematic chain mechanism and the end-effector is adjoined to the base through several actuating cables. Afterwards, the Proportional-Integral-Derivative (PID) controller and the fuzzy PID controller have been applied on the cable robot for different and various final desired conditions. It is noticeable that a proper control rule for the cable robot not only causes the tracking of the desired trajectory, but also guarantees the positivity of the cable tension forces for all states. In order to determine the parameters of the controllers, the krill herd algorithm as a population-based optimization procedure is implemented. The obtained results indicate the successfulness of the proposed strategy to guide the cable robot to the desired objectives.

In this paper, the thermal effects because of temperature gradient and the stress distribution on a Yb:YAG thin disk under the three-side pumping with different powers are investigated. The side surface of the disk is being pumped by three continuous working diode lasers and its underside plane is being cooled by water. The amount of distribution of temperature and stress in the disk is studied by the Finite Element Method (FEM) with the help of ANSYS software. The largest power absorbed by Yb:YAG crystal is 240 W which in this power, the temperature of active material reaches 408 K and its stress is 132 MPa. The variations of refractive index and focal length created in the thin disk are calculated by obtained data from ANSYS software and indicates that Yb:YAG disk remained isotropic and it is a suitable laser active substance.

In this paper, the experimental results from the study of the effect of the angle of the slope of glass cover on the performance of the two geometry of solar desalination with flat and convex plates under different amounts of distilled water are presented. The slope of the studied angles is selected to be 25°, 27.5°, 30°, 32.5° and 35° while the other design parameters remain constant. The results showed that a solar collector with a convex absorber plate has a higher average daily water production compared to the solar collector with a flat absorber plate. Experiments also showed that the angle of the slope has a significant effect on the performance of the solar desalination system. The best slope is 32.5° and the larger angles cause to decrease in the heat transfer coefficient. These results can be used for design purposes and eliminate the common assumption of using lower angles to optimize productivity. Finally, from the obtained information, new experimental relations are obtained for the Nusselt number for the flat and convex surfaces with different slope angles of the glass cover.

In this paper, design and numerical simulation of an energy harvester piezoelectric cantilever beam has been investigated using Comsol multiphysics finite element software. Modelling the piezoelectric cantilever beam and applying end support boundary condition, material property, meshing the beam and harmonic excitation of the clamped support, deflection of the beam yeilds to the electrical current and voltage, respectively. In the modelling and simulations for the beam and piezoelectric blocks, the aluminum and EAPap materials have been considered, respectively. The mode shapes and natural frequencies of vibration for the piezoelectric beam have been extracted and the effect of different type of piezoelectric block arrangement to obtain electrical energy harvesting has been investigated. Also, the outcome FE results have been validated and compared with experimental data reported in the literature. It is shown that in excitation frequency condition equals to the natural frequency of the beam when the beam width divided in either two or three strips with serie/parallel type of arrangement in an equivalent electrical circuit, the energy harvesting capacity of the beam increases in comparison to the beam with the one strip.

Industrial arms must be able to perform their tasks in environments with serious unplanned conditions and perturbations. In this paper, the aim is to control a robotic manipulator which is under parametric uncertainty and significant external perturbations. Fuzzy type 2 logic is considered as an appropriate choice in the face of uncertain conditions due to various reasons such as the use of fuzzy membership functions and footprint of uncertainty existence in the algorithm. The use of neural network can increase the robustness of controller in the face of uncertainties. Although the neural network does not necessarily need to build its fuzzy type 2 rules, the initial rules based on sliding surface of sliding mode scheme can improve system’s performance. More robustness of the novel algorithm in comparison with classic sliding mode controller is the main feature made in the presence of parametric uncertainty and external perturbations. In addition, the controller self-regulation feature, based on the existence of neural network in the central block of fuzzy type 2 controller, helps to increase the robustness of the method. Positive performance of novel scheme has been shown in simulation of two-link robotic arm with different significant perturbations.

The creation process of biological tissues needs an artificial substrate in order to control cellular responses to mechanical and chemical signals. This artificial support is named a scaffold. Investigating the effects of scaffold geometry on fluid flow regime as well as influence of different locations of the cells on the scaffold on effective mechanical stimulations of the stem cells are the main goals of this study. So, scaffolds were utilized which include architecture of the pores achieved from implicit surfaces. Using finite elements and fluid-structure interaction methods and solving the problem through two way coupling of the equations, the results show that microstructure of the scaffolds and architecture of their pores have major effects on improvement of fluid flow reaching various locations of the scaffold. This issue besides of optimization conditions of shear stress and hydrodynamic pressure in different surfaces of the scaffold leads to increase of oxygen delivery and perfusion to the cells. Moreover, preference of using HP scaffolds and as a next priority utilizing of Gyroid scaffols is reported.

Using renewable energies instead of fossil fuels can reduce environmental problems. In this way, batteries can play an important role as energy storage. Lithium-ion batteries have been very much considered in recent years due to their high energy density and long life time. The use of electric vehicles is increasing to prevent air pollution in various countries. In these cars, electric motors that work with batteries are used instead of internal combustion engines. In this paper, a lithium-ion battery was modeled electrically and thermally. It was indicated the temperature increase and the battery voltage decrease in discharging process. The numerical solution of the energy and electrical equation was made using a finite volume method in computational fluid dynamics. The results showed that when the battery is discharged at a discharge rate of 1c, the battery temperature reaches 54°C and at a discharge rate of 2c, the battery temperature reaches 83°C, which can damage the battery. To avoid this problem, a cooling system was designed which, with a flow rate of 0.2 m / s and 25°C at a discharge rate of 1c cooled battery to 31°C and at a discharge rate of 2c to 40°C. To increase cooling, with a flow rate of 0.2 m / s used a temperature of 15, in this condition the temperature of the battery at discharge rate of 2c reached a discharge temperature of 37°C, which falls within the permissible range.

In Nano-scales, the application of nanobeams as sensors of infinitesimal masses is widespread and they been studied by many researchers in nanotechnology. This paper analyzes dynamics and vibration of mass sensing nanobeams in various vibrational modes, taking into account the size effects in nano-scales. To do this, the governing equations for the transverse vibration of a nanotube are derived by considering size effects and an added mass at the arbitrary distance from the beam using the nonlocal elasticity theory. Employing the Hamilton principle, final equations and boundary conditions of the mass sensing nanobeam are obtained. Using the exact method, the frequency characteristics of the mass sensing nanobeam are obtained. Then, The size effects and mass sensing on the frequency behavior of the nonlocal nanobeam are simulated especially at higher modes of vibration. The obtained results show that the mass sensor feature of the nanobeam has increased at higher modes and therefore higher vibrational modes should be carefully studied. It is also observed that size effects at the higher vibrational modes are inventible, and these effects on the frequency are greater than the mode shapes of the nanobeam.

In this paper a two dimensional numerical study of solidification of phase change material (PCM) in a triplex tube heat exchanger is studied. Water is used as heat transfer fluid (HTF) which flows through the inner and outer tubes while the shell side is filled with RT82 as the PCM. The purpose of this numerical study is to increase the internal tube size vertically and horizontally with the constant volume of phase change material as a geometric parameter and also the effect of temperature as a flow parameter. Also, in this study, the effect of nanoparticles on the solidification process of phase change material has been investigated. The results show that the solidification time has decreased with the addition of nanoparticles. Also, the results indicate that with an increase in the internal tube, a significant decrease in solidification time is observed. Vertical geometric arrangement with two and three internal tubes compared to the flow arrangement with an internal tube of solidification time has decreased by 15% and 30%, respectively.

To achieve a high-performance additive to improve lubricant quality, increasing its lifespan and efficiency, as well as environmental compatibility, recycling capability and reducing production costs and processing are among the key challenges facing the lubrication industry in the country. In this study, the effect of titanium dioxide nanoparticles as an additive with concentrations of 0.1, 0.2 and 0.5 wt% were investigated on tribological properties of lubricants using pin-disk test method. According to importance of condition monitoring on oil analysis and analysis element of erosion, after the wear tests, coefficient of friction and  thermal conductivity coefficient,the best sample was chosen and used in the single-cylinder Honda CDI-125 motorcycle. According to the results of the tests, it was found that the nano-lubricant with a concentration of 0.5% by weight has the best performance. In other words, increasing the weight concentration of nanoparticles as an additive in epoxy biofuel has a positive effect on improving anti-wear properties and friction. Also the elemental analysis results showed that the application of a nano-lubricant did not have a positive effect on reducing the erosion elements of iron, chromium, aluminum, tin and nickel, but the erosion elements of   copper, lead and molybdenum decreased.

In this research, for the first time, the free vibration of the functionally graded beam containing transverse crack under clamped-clamped boundary condition studied based on Reddy high order theory. It was assumed that mechanical properties of beam vary exponentially in the thickness direction. To drive the closed form solution for natural frequencies of functionally graded beams containing a transverse crack, Ritz method was used. The effects of slender ratio, the location of crack, depth of crack and material gradients on natural frequency were also examined. Finally, the results of the analytical method were analyzed and compared with results of modeling by ABAQUS software and other studies. This research shows that due to more complex equations of Reddy beam theory, using Reddy beam theory for a thick beam and Timoshenko beam theory for a thin beam are more suitable. In addition, a relation between the depth of crack and the necessity of using functionally graded beam is confirmed.

A numerical model of the new passive solar collector is performed, then the thermodynamic analysis of the thermal cooling systems is applied to the model in three systems: absorption, ejector, and Rankin for different climate condition of Iran, in this work. The results show that a large percentage of the energy required of the systems is available by the solar, even at some hours of the day; the total energy can be supplied by the solar. In all systems, the highest percentage of energy supplied by the solar and the highest solar coefficient of performance is related to Abadan and the lowest amount of it is related to Ramsar. In the absorption system, with the increase of generator temperature, the solar fraction decreases, and the solar coefficient of performance increases, but in the ejector and Rankin systems, the solar fraction and the solar coefficient of performance increases with the increase of generator temperature. In all systems, with the increase of evaporator temperature, the solar fraction and the solar coefficient of performance increase.