نشریه مهندسی مکانیک و ارتعاشات
سال هشتم شماره 2 (پیاپی 27، تابستان 1396)

Due to the favorable properties of wide regions of the world and has developed a shortage of fresh water in dry areas that already face large-scale development has occurred Such as parts of North Africa and the Middle East, to produce fresh water by desalination to need a lot of energy and a lot of research studies for the development of solar desalination is being done by solar energy With the aim of identifying key technical challenges and potential opportunities for solar energy, A variety of technologies for the optimum amount of solar energy as well as various technologies for solar desalination system includes advanced technique for restoring energy is studied we conclude that the development of solar desalination system for cost-effective and energy-efficient in the near future may be grounds for water supply desert regions of the world. The effects of water cooling with two modes: simple desalination (passive) by installing cooling and desalination of water (active) examined and compared in terms of daily production has been tested. Tests in August (August) in geographical coordinates (N:35°34′,E:53°22′) carried on the basis of the results observed maximum production rate freshwater disabled 0.26 (kg / m2) per hour. Moreover, the daily output disable mode of 1.035 (kg / m2.day) daily 1.530 (kg / m2) reached in active mode.

This paper presents a mathematical model for geometry optimization of a rectangular cross-section flat plate fin with application in calculating optimized width of a heat sink for different Nano fluids (Aluminum oxide, Silicon dioxide, Titanium dioxide, Copper oxide, Gold, Copper, Diamond and Ferros oxide) with water as based fluid. Flow impinging on the fin is considered laminar. The effects of Reynolds number, volume fraction of nanoparticles, particle size, inlet velocity and different average temperature on the geometry optimization of the fin are investigated. A rectangular flat plate fin made from copper with higher thermal conductivity is used as the test case. Various Nano fluids with different volume fractions (0.005% to 0.1%) and different nanoparticle sizes (3×10-8 to 1×10-7 nanometer) are analyzed. In this analysis, as a basic assumption, the length of the fin is taken larger than the width and the fin volume is considered constant. Then, width of the fin will be optimized. The results indicated that the highest and the lowest optimized width is related to Gold and silicon dioxide nano fluids respectively. Increase in volume fraction, inlet velocity and temperature and decrease in nano particle size leads to optimized width enhancement.

Welding plays an important role in manufacturing and it is a reliable and efficient joining process in which the coalescence of metals is achieved by fusion. Nowdays welding is as the main and most common process for joint of metals. Among the welding methods, Laser Beam Welding) has the potential of welding very small and precise components. Localized heating with solidification of the melt, makes the connection between parts. In this thesis, laser spot welding process, which is one of the varieties of LBW process, is studied. In fact the laser spot welding is a simple type of laser welding that is widely used in various industries. The low strength of joints can damage structures. Therefore it is important that the strength of the joint be estimated and optimized. In this research, investigation and optimization of the laser spot welding process using design of experiments and response surface method is considered. Three parameters (peak power, pulse duration and thickness) of the process at three levels were the input factors. Material of sheets that was used in this research is AISI 304 stainless steel. The response or output factor was tensile - shear strength. Minitab16 software was used for design of experiments and analysis of the results. Finally, results showed that increase the peak power until 4250 watt and pulse duration until 3/5 millisecond provide the most tensile - shear strength (2200 Kg), and Square of thickness has the most negative effect on tensile shear strength of the joint.

During machining a portion of the heat generated by operation activities edges of cutting tool relative to the workpiece is transferred to machine tool, and in addition, the friction generated in continuous motion of Ball Screw and the Nut that Due to shift of axis machine is created, causing the expansion of the Ball Screw size will be. Because of the length of the high ratio of length to diameter, expansion of the length of Ball Screw to be important. Because after every movement applied to in the NC, according to the size difference between the previous program and the current line, in addition to the original displacement, had done an additional displacement due to the expansion of the Ball Screw. Machines CNC five-axis, in addition to the direct impact of linear expansion length of Ball Screw linear axes for the accuracy of the workpiece geometry, the indirect effect are also considering option RTCP (Rotation Tool Center Point), to move the axis rotary is shown. The RTCP active, the center of cutting tool is fixed in space instead of, the center of the rotary axes are moving. In this case, to compensate for displacement of cutting tool, In effect movement the rotary axes, linear axes will be moved. In this paper, directly or indirectly effect of Ball Screw linear expansion on the workpiece geometric accuracy studied using analytical-mathematical And the results can be compared with the adaptive control as five-axis CNC machines used in the paper.

The subject of this study was vibration damping of Timoshenko beam based on finding optimal place and number of piezoelectric sensor and actuator using LQR controller and MOPSO algorithm. Today, researchers make a lot of effort to make a structure have optimized reliable life, manufacturing cost, and power consumption. One of the researches on optimized and controlled smart structure is through using piezoelectric sensor and actuator so that the sensor and actuator can adopt the best controlling interest based on the type of approach to design the controller upon receipt of a vibration by sensor and with the transfer of vibration signals to the controller. Then, it can transfer a proper signal to the actuator. In fact, it is the actuator that tries to neutralize the vibrations of the structure in order to have a structure with longer life and lower failure and can meet the designer's objective in the best way. In this study, using MOPSO algorithm and defining the design variables, the best number and location to place the piezoelectric sensor and actuator at the bottom and top the bottom and top cantilever beam in in a specified range can be searched and then an optimal model of smart structure was suggested.

This paper studies the effects of soluble cutting fluid-based sio2 Nano-fluid on machining force in turning of hardened AISI 4340 tool steel. These influences, Moreover, are compared with the outputs of similar tests through dry. The obtained results showed 1% volume fraction of sio2 Nanoparticles added to soluble water as cutting fluid was considerably reduced machining force in comparison dry. The investigations indicated that sio2 Nano-fluid reduced machining force by 24% compared to the dry state Moreover, the results illustrated that the lowest machining force obtained in cutting speed 400 m/min, feed rate 0.1 mm/rev and cutting nanofluid.

During movement in different flying levels, ballistic objects can endure various forces, which depend on the strength of different parts of the intended body at the time of their design and manufacturing. Among the forces resulting from aerodynamic equations, lift and drag forces could be noted. These two forces depend on characteristics such as the angle of attack. In the present paper, a Shahab-3 ballistic missile (manufactured in Iran) has been evaluated by simulating in the software Najm. This software can be used to analyze the ballistic objects. This work were analyzed in two stages, once with the attack angle of 2 degree and once again with the angle equal to 8 degree. After performing the investigations, it was determined that in the attack angle of 2 degree the forces created in the body of ballistic object do not develop any critical pressure or tension. However, in the attack angle of 8 degree, the lateral pressure starts from the length of 8 m from the object’s tip and it reaches the critical point in the end area, which complies with reality. Moreover, the lift-to-drag coefficient ratio that is considered as a characteristic of aerodynamic analysis is much more suitable for angle of 2 degree.

A study on fracture toughness (KIC), fracture energy (GIC) and Young's modulus of styrene acrylonitrile composites by two volume content of 24% and 34% acrylonitrile has been conducted. ZnO nanoparticles were added to composites up to 1 vt%. Volume percent parameter has been described as a sensational parameter. The experimental results indicate that adding ZnO nanoparticles increase the mechanical properties and in some cases, it decreases them. Also the experimental results and the results of modeling show that the second order response surface method makes the best prediction. Additionally, the best value for Fracture toughness is 2.283 MPa.m1/2 when the volume percent of styrene acrylonitrile is 34% and volume percent of ZnO is 0.1%. Also, the best value for fracture energy is equal to 1101 J/m2, when the volume percent of styrene acrylonitrile is 34% and the volume percent of ZnO is 0.33%. And finally, this method shows that the best value for Young's modulus is 4.281 GPa when the volume percent of styrene acrylonitrile is 31% And volume percent of the particle is 0.5%.