The tra  ortation industry‌is one of the fundamental industries in human societies that has undergone many changes from the past to the present. This industry is of such great importance that its absence can cause many problems in life. Therefore, with the advancement of science and technology, the structural complexity of this industry has increased day by day.Cars are among the vehicles in this industry that have the most users, so that over time their complexity, diversity, and number have increased. Despite the widespread use of cars, we should not be unaware of their disadvantages and vulnerability. Accidents are one of the most important causes of death in the world, always claiming many victims. In fact, during an accident, a lot of energy is released as a result of the collision of cars with each other, which causes damage and injury to the occupants of the car by transferring this energy to them. If the collision speed is higher, the consequences will be more fatal.Therefore, the importance of vehicle safety in the field of accidents is not hidden from anyone, and for this reason, it is necessary for engineers and researchers in this field to focus their attention on this issue and try to solve this problem. A lot of research and experimental work has been done in this field, which has ultimately led to the introduction of energy-absorbing structures. Energy absorbers are actually structures that are installed in the front of vehicles and absorb the kinetic energy of the collision during an accident by changing their plastic shape and preventing it from being transferred to the passengers. The use of this type of structure is not limited to the field of automobiles, and these structures can be used wherever there is a need to absorb irreversible energy.In this study, the sandwich panel structure was investigated as an energy absorber. In fact, the sandwich panel structure consists of two composite shells with carbon fibers in 7 cylindrical layers and corrugated aluminum cores. In this research, corrugated cores in eight states were used, whose cross-sectional area is a function of a sinusoidal relationship and changes according to the amplitude and number of waves created. The composite shells and corrugated cores were simulated in the Abaqus finite element software and after assembling them together and forming the sandwich panel, they were placed between two rigid plates, one of which is fixed and the other with a mass of 100 kg and a speed of 20 m/s hits the sandwich panel, causing the axial collapse of the sandwich panel. By obtaining the force-displacement diagram resulting from the collapse of the sandwich panel for each of the eight core states mentioned, the amount of energy absorbed and other indicators of the impact resistance of the sandwich panel, including the initial peak crushing force (IPCF), the average force (MCF), crushing force efficiency (CFE), and specific energy absorption (SEA). To validate the materials and simulations performed in this study, existing experimental and numerical research in this field was used. According to the results obtained from the simulation process of low-velocity impact on sandwich panels for different corrugated cores (eight states), it can be concluded that by increasing the number of waves and the amplitude of the cross-sectional area function of corrugated cores, the amount of energy absorbed and the impact capability evaluation indices also increase, so that among the eight states of the aluminum corrugated core, the core with amplitude A = 2.5 mm and wave number N = 10 has the highest energy absorbed and the highest values ??of the impact capability evaluation indices compared to other corrugated cores.

In this thesis, the upsetting process of bimetallic sheets has been analyzed by the force balance method and simulated by the finite element method. The upper and lower dies are cylindrical and have equal radii. The width of the sheets is large compared to their thickness, and therefore it is assumed that the process is carried out in a plane strain state. The bimetallic sheet is composed of a combination of two sheets of different materials, copper and aluminum. Copper due to its high electrical and thermal conductivity and aluminum due to its lightness and corrosion resistance, provide an attractive combination for industrial applications. In this process, as in other metal forming processes, predicting the geometry of the deformation zone and the forming force is important. To analyze the process by the force balance method, a free diagram of a slice of the sheets in the deformation zone is drawn and by writing the equilibrium and yield equations, the forming force in each press stroke is calculated. The analyses performed include examining the deformed dimensions of the sheets as well as the curve of the forming force changes in terms of the press stroke. In the next step, the upsetting process is simulated in the ABAQUS software environment. The material behavior of the two sheets is considered as rigid-plastic in the analysis and simulation. Also, the two sheets are completely bonded together at the beginning and this connection is maintained until the end of the process. The results of the force balance analysis, including the changes in the forming force in terms of the press stroke and the dimensions of the deformation zone, are compared with the simulation results. These comparisons show a good agreement between the results. Considering the unique properties of both metals, the results of this research can have wide applications in various industries such as automotive, aerospace and electronics. For example, in the automotive industry, the use of bimetallic compounds can lead to weight reduction and increased fuel efficiency.   

  Due to the wide application of composite materials and nanocomposites in industry, in this thesis the free vibration of trapezoidal nanocomposite reinforced by Montmorillonite nanoparticles with a fixed support was investigated. The oscillation frequency of the part in the state of free vibration is called the natural frequency, which is without the presence of an external force. Every object or system has its own natural frequency depending on factors such as mass, stiffness and shape. If the frequency of an external vibration applied to the system is equal or close to the natural frequency of the object, the phenomenon of resonance or resonance occurs. The four primary natural frequencies of the trapezoidal plate made of resin with different amounts of montmorillonite nanoparticles were calculated using Abaqus software, a

   Terfenol-D is a magnetostrictive alloy that falls under the category of smart materials, composed of terbium, iron, and dysprosium. This alloy is used in actuators, sensors, and other applications due to its unique properties, such as high saturation strain, high Curie temperature, and significant functional coefficients. Like any other ferromagnetic material, Terfenol-D exhibits magnetic losses, including hysteresis, eddy currents, and excess losses, which need to be accurately calculated under various operating conditions to predict the output of actuators and sensors. When Terfenol-D is subjected to an external magnetic field and undergoes magnetization cycles, hysteresis loss occurs due to the movement and rotation of microscopic magnetic domains, eddy current loss occurs due to the generation of a magnetic field opposing the excitation field, and excess loss occurs due to lattice defects and non-uniform magnetic domains. In this thesis, research was conducted to predict magnetic losses accurately and logically, and due to reasons such as simplifying mathematical calculations and eliminating errors resulting from lengthy and complex methods used in other models, the hyperbolic tangent model was used to calculate the aforementioned losses. To this end, the model's coefficients and parameters were extracted using previous experimental results, and then the model was developed to enable the calculation of various losses. Finally, new relationships were presented to predict the model's coefficients and parameters at new frequencies. The new relationships and model used at new frequencies of 100 Hz and 300 Hz, which had not been used before, were validated, and the results were compared with those obtained from the experimental model.The results obtained in this thesis show that the use of the hyperbolic tangent model and the presented relationships can predict the magnetic power loss in terfenel-D with high accuracy in the frequency range (0 to 300 Hz).

   در اين پايان‌نامه، مدل تحليلي ارائه مي‌گردد كه ضربه سرعت پايين را روي ساندويچ پنل‌هاي كامپوزيتي مدور با رويه‌هاي تقويت شده با نانو لوله‌هاي كربني FG مدلسازي مي‌نمايد. در اين مدل تحليلي با مشخص بودن انرژي جنبشي اوليه ضربه زننده، نيروي تماسي در محل برخورد، ميزان تغيير شكل محل برخورد و برآوردي از ناحيه دچار عيب شده محاسبه مي‌گردد. ساندويچ پنل كامپوزيتي بصورت متقارن و مدور بوده و سطح ورق هاي كامپوزيتي آن از لايه‌هاي متقاطع تشكيل شده است. در اين مدل تحليلي، انرژي كششي غشايي شدن و نيز انرژي كرنش ايجاد خمش در رويه ها تعيين شده و هسته ساندويچ پنل بصورت هاني كمب و كاملاً پلاستيك در نظر گرفته شده است. همچنين، براي تعيين تاريخچه نيروي تماسي و تغيير شكل ساندويچ پنل از مدل جرم-فنر دو درجه آزادي استفاده شده است.معادلات حاكم بر مسئله با محاسبه انرژي پتانسيل، كار نيروي خارجي و انرژي جنبشي سيستم متشكل از ضربه زننده و ساندويچ پنل كامپوزيتي مدور در دستگاه مختصات قطبي استخراج گرديده و با استخراج معادلات حركت سيستم با مينيمم سازي انرژي سيستم معادلات حاكم بر مسئله حل مي‌گردد. براي حل معادلات حاكم بر مسئله از برنامه‌نويسي در نرم‌افزار متلب استفاده مي‌شود. در نهايت مدلسازي المان محدود از فرايند در نرم‌افزار آباكوس (ABAQUS) صورت مي‌گيرد و نتايج مدلسازي تحليلي با نتايج بدست آمده از شبيه سازي عددي با نرم‌افزار تحليلي آباكوس مقايسه مي‌گردد. مدل تحليلي ارائه شده در اين پايان نامه براي تحليل ضربه سرعت پايين بر روي ساندويچ پنل كامپوزيتي مدور با رويه‌هاي تقويت شده با نانو لوله‌هاي كربني FG با هسته هاني كمب از نوآوري‌هاي مطرح در اين پايان نامه است.

Despite the advantages of layered composites, due to low resistance to residual stresses and delamination under pressure High heat, their use is limited. Sandwich structures are suitable candidates for introducing composite materials They are advanced such as purpose graded materials (FGM) and composites reinforced with fibers. Therefore, in this research, Analytical investigation of sandwich beam reinforced by boron nitride nanotubes under thermal load to be For this purpose, in this research, for simulating the beam in MATLAB software, a single-headed Nimushenko beam was used in which the beam core is made of aluminum foam and the layers are made of 1161 aluminum plates with a purity of 99.2% in considered Also, Mori Tanaka's method was used to determine the properties of reinforced layers. and ultimate forces It is presented based on the Montanity model. According to the obtained results, the destruction force increases with the increase of core thickness but its increase rate is different according to the different conditions of the sandwich beam, so that in the thickness equal to the top At ambient temperature, the beam with reinforced top made of boron nitride nanotubes has more resistance. force of destruction It has very little dependence on the thickness of the top. Also, the destruction force increases with the increase in the thickness of the layers, but the rate Its increase is different for different conditions of sandwich beam. In such a way that in the same thickness in the ambient temperature, the beam With a reinforced top made of boron nitride nanotubes, it has less changes. Also with increasing temperature The difference between the forces of destruction should be reduced.

  Among different materials, polymers have found a special place in various engineering applications due to their lightness and other special properties. In order to overcome some of the weaknesses of polymers, they are made and used in the form of composites or nanocomposites. The expansion of polymer composite materials in industries requires the necessity of a detailed investigation of the properties of these materials under different loading conditions, including high speed impact resistance. One of the disadvantages of cured epoxy resin is its brittleness, which reduces its resistance to impact, to solve this problem. The problem is that curing agents are used in the resin. Common methods of curing polymers mainly reduce mechanical properties such as tensile strength. In this thesis, the effect of G-POSS nanostructure as a hardening agent and its effect on the mechanical properties of epoxy resin is investigated. , the effect of adding G-POSS nanoparticles on the mechanical and impact properties of pure epoxy and the combination of epoxy and carbon fibers is investigated experimentally, and the effect of adding different weight percentages of G-POSS nanoparticles on mechanical properties such as Young's modulus, yield stress and Tensile strength and elongation percentage and impact properties such as maximum contact force, contact time and dimensions of the damaged area of the crack in the laminated matrix are checked. Samples of these composite structures with different percentages of G-POSS nanoparticles with uniform distribution are made and tensile and impact tests are performed on the samples. . For this purpose, the mixing process is carried out in two stages, first for 12 hours at a temperature of 70 degrees Celsius using a magnetic stirrer and then for ten minutes the ultrasonic vibration method is used, then the composite samples reinforced with unidirectional carbon fibers are placed in the resin bed. Epoxy is prepared with GPOSS nanostructure added (0.5, 1 and 1.5% by weight of nanostructure was added to the resin). Tensile and low speed impact tests are performed on the samples. The results show that the best results of the impact test are obtained for the sample with 1.5% by weight of GPOSS, which indicates an increase of 26.7% in energy absorption, and the best results of the tensile test are obtained for the sample with 1% by weight of G-POSS, which is the result It is a 28% increase in tensile strength. Based on the results, it can be stated that G-POSS nanostructures are a suitable option for preparing nanocomposites with unique characteristics.

   In this thesis, the effect of adding silica nanoparticles on the mechanical and impact properties in the combination of epoxy and fiberglass with needle-sheet composite fibers of particle fibers has been experimentally investigated and the effect of adding 3% by weight of nanosilica Mechanical properties including Young's modulus, tensile strength and elongation percentage and impact properties including maximum contact force, contact time and dimensions of the damaged area (cracks in the matrix and laminated) have been investigated and analyzed. Glass fibers are combined in sheet and needle form and a new composite sheet is made. The particle fibers are made of Mat material and were determined with the help of tensile tests, tensile strength, Young's modulus, elongation. In fact, the goal has been to see what changes have been made in the Young's modulus and tensile strength as well as the elongation at break by adding a certain weight percentage of nanosilica in the said composite. In addition, based on the technique of artificial intelligence and using the combination of flight search algorithm and teaching-learning based algorithm, it has been used to train the fuzzy-adaptive neural inference network. In fact, the combination of the two mentioned algorithms was done because the flight search algorithm has a negative feature, and that is falling into the trap of local optima, but at the same time, it has a suitable convergence speed to achieve the optimal answer. In order to solve this problem, it was combined with another algorithm whose biggest advantage is its search power and not getting trapped in local optimal points. From the combination of these two algorithms, a hybrid algorithm was created which has two special advantages of proper convergence speed and necessary power to avoid getting trapped in local optimal points. This combined algorithm has been used to train the adaptive neural fuzzy inference network. Finally, the aforementioned combined network has been used to predict the mechanical and impact properties of the composite presented above.

  Metal pipes have been widely used in engineering structures for a long time. For example, pipes are used in the transfer of fluids such as oil and water or in the construction of bridges, masts, car chassis, airplanes, military industries, etc. Pipes are also used for torque transmission in cars, industrial equipment and deep well drilling rigs, etc. Therefore, due to the constant presence of metal pipes in various industries, it is sometimes necessary to change the geometrical dimensions of the cross-section of the pipe to suit the work duty by creating local deformations. In this thesis, the process of local lateral compression of thick-walled pipes has been investigated by two experimental methods and numerical simulation. In this process, the pipe is placed horizontally between the upper and lower molds. The molds are cylindrical and the axes of the molds and the tube are perpendicular to each other. To investigate the behavior of plastic deformation, two types of aluminum tubes with the same outer diameter and different inner diameter were selected and three similar samples were made from each type. The real stress behavior in terms of the real strain of the aluminum material was extracted from the simple tensile test. The tubes are placed horizontally on the lower fixed mold and plastically deformed by the upper mold which is connected to the moving part of the press machine. Then, the geometric dimensions of the deformed area of the tubes have been measured for different press courses. The geometric shape of the deformation zone and the experimental data of the deformation forces have been compared with the process simulation results in Abaqus software. Examining and comparing the results of two experimental and simulation methods revealed that the dimensions of the deformed area in both methods have a good match. The forming forces calculated by Abaqus software show slightly higher values than the experimental values, which can be considered a good validity for the data considering the conditions of the problem.

Implant Insertion is not always successful, Because of inappropriate stability of implant-bone intersection. It seems implant geometrical including length, diameter, Number and depths flutes are affected on stresses and mechanical stability. The purpose of this research is study of implant geometrical variable such as numbers, angle and length of vertical grooves (Flute) on stress distribution and the amount of the implant displacement during static and periodic loads using finite elements Method (FEM) according to ISO 14801 international Standard. founded, that the effect of geometrical variables such as the length of the groove on the implant stem, the angles and Flute’s Number on the overall life of the dental implant and the amount of displacement after implantation has been very effective, so that the diagonalization of the groove has increased the tension better and its length is also more optimal in the original implant. Convergence of geometric variables such as alpha 6 degrees, beta 12 degrees, three grooves, with a fixed groove length will increase the life and stability of the implant by reducing the displacement of the implant in the anchor(bone). Since creating the final torque on the abutment causes the mechanical stability of the dental implant, the torque and loading couple will also stabilize the implant in the bone and increase its lifelog. When the abutment in the implant is tightened with a torque of 35 newton.mm. It causes more stability through more engagement with the surrounding bone.

در اين پايان نامه، ضربه سرعت پايين روي لوله­ فلزي با پوشش كامپوزيتي الياف كربن پيچيده شده با پليمر(CFRP) با روش شبيه ­سازي عددي و با نرم ­افزار آباكوس مدلسازي شده است و مقدار نيروي تماسي، جابه­ جايي در راستاي شعاعي، تغيير شكل محل برخورد، كرنش پلاستيك، ميزان آسيب لوله فلزي و تنش در شرايط بارگذاري ضربه­ اي سرعت پايين محاسبه و مقايسه شده است. در اين پايان ­نامه در ابتدا براي صحه­ سنجي لوله كامپوزيتيCFRP   حاضر تحت ضربه سرعت پايين با نتايج تحليلي و اجزا محدود حاصل از كار هاي پيشين مورد مقايسه قرار گرفته است. سپس با استفاده از نرم ­افزار المان محدود لوله فلزي ساده و لوله فلزي با پوشش الياف كربن پيچيده شده با پليمر مدلسازي مي­گردد و معيار شكست مناسب جهت پيش بيني شكست ناشي از ضربه سرعت پايين بر روي نمونه مورد بحث به كار گرفته مي شود.نتايج به دست آمده نشان مي دهد كه لوله فلزي با پوشش CFRP بنا به جذب انرژي جنبشي ضربه ­زننده توسط لايه كامپوزيتي داراي تغيير شكل ، تنش ،آسيب كمتري نسبت به لوله فلزي ساده مي­باشد و نيز در حالتي كه پوشش كامپوزيتي بر روي لوله قرار مي گيرد به صورت موضعي نيروي تماسي در لايه كامپوزيتي افزايش خواهد يافت و اين مهم باعث مي شود كه مقدار انرژي وارد به لوله فولادي كاهش يابد. نتايج مويد آن است كه در لوله فلزي ساده در اثر ضربه سرعت پايين ناحيه گسترده­ تري دچار تغييرشكل پلاستيك نسبت به لوله فلزي با پوشش كامپوزيتي مي­شود.

  Thin-walled metal tubes filled with metal foam are used as new energy absorbers in low velocity impacts, which bend and crush by absorbing the energy caused by the impact and absorb the impactor's kinetic energy. In this research, the analysis of low speed impact on circular tubes filled with metal foam and determining the amount of energy absorption due to the impact has been done. For this purpose, ABAQUS finite element software has been used and the modeling results have been compared with the results of the reference article in the litereture and the accuracy of the modeling has been ensured. In the following, 10 different models are considered for the impact of the impactor on the pipe. The results of stress, plastic strain, displacement force diagram, dimensionless displacement force diagram and absorbed energy have been extracted and discussed. The parameters investigated in this research are the pipe radius, pipe thickness, pipe length, impact point, foam effect and pipe material. By examining the results, it was found that by increasing the radius and thickness of the pipe and by decreasing the free length of the pipe, the amount of absorbed energy increases and the impact performance of the pipe improves. It was also determined that the amount of energy absorbed due to impact in the tube filled with foam is 5 times the energy absorbed in the tube without foam. In the following, by coding in MATLAB software, the values of local dentingin the first to fifth models were investigated and the results obtained were compared with the results of finite elements. It was found that the average difference of the results obtained for local displacement from finite element modeling and analytical equations is 3.5

در اين پايان نامه به بررسي خواص مكانيكي نانو كامپوزيت تابعي اپوكسي تقويت شده با نانو ذرات سيليس پرداخته شده است. در بسياري از كاربرد هاي مهندسي مواد مركب به دليل مزايايي چون استحكام وسختي به وزن زياد، مقاومت خستگي، مقاومت خوردگي و به ويژه خواص ضربه اي مناسب به طور گسترده مورد استفاده قرار مي گيرند. در سال هاي اخير استفاده از نانو مواد بهمنظور افزايش خواص مكانيكي مورد توجه قرار گرفته است . نانو ذرات سيليس به عنوان پر كننده پوششي براي تهيه تقويت كننده هاي نانو كامپوزيتي پايه اپوكسي استفاده مي شود. جهت بررسي عملكرد تاثير ميزان نانو ذرات سيليس نمونه هايي با درصد هاي وزني مختلف با توزيع يكنواخت و همچنين نمونه با توزيع تابعي ساخته شده است . در ادامه نمونه ها تحت آزمايش تست كشش قرار گرفته و نتايج حاصل از آن جهت بررسي خواص مكانيكي از جمله مدول يانگ ، چقرمگي و... مورد تحليل   قرار گرفته است. همچنين با تهيه عكس هاي SEM كيفت ساخت ونحوه توزيع مناسب نانو ذرات سيليس مورد بررسي قرار گرفته است. با توجه به بررسي عكس ها، آگلومره شدن يا كلوخه شدن ذرات در نمونه هاي با توزيع يكنواخت مشخص شده ودر نمونه تابعي نيز ميزان پيوستگي مرزلايه ها مشخص گرديده است. همچنين در بررسي تحليلي اين تحقيق از نرم افزار آباكوس استفاده شده است . در اين نرم افزار پس ازتعريف خصوصيات نانو كامپوزيت تقويت شده با نانو ذرات سيليس و مش بندي لازم به تجزيه و تحليل نتايج آزمايش تست كشش پرداخته شده است. در پايان، نتايج بدست آمده از مدلسازي با نرم افزار آباكوس با نتايج تجربي مقايسه گرديده و دقت آن مورد بررسي قرار گرفته است. در بررسي نتايج بهبود خواص مكانيكي مشاهده مي شود، با افزايش درصد وزني نانو ذرات سيليس ميزان مدول يانگ افزايش مي يابد.مقدار مدول يانگ نمونه تابعيكه خود تركيبي از نمونه هاي با درصد هاي وزني يكنواخت مي باشد، نسبت به نمونه هاي با توزيع يكنواخت بيشتر است. در بررسي مقدارچقرگي، نمونه تابعي مقداري بيش از هريكاز نمونه هاي با توزيع يكنواخت دارد و نتايج حاصل از چقرمگي در هر دو حالت تجربي ومدلسازي اختلاف جزيي دارند.   

  In this thesis, the dynamic response of sandwich beams with carbon nanotube-reinforced surfaces and foam cores on a viscoelastic foundation under low-velocity vertical impact in the middle of the upper surface is investigated. In this research, an analytical model for nonlinear modeling is presented to calculate the amount of central Deflection and Contact Force. Beam is a sandwich panel with a nanotube composite surface and a foam core. Using the strain-displacement and stress-strain relationships and using the conditions of compatibility in between core and sheets, the displacement field of the core is determined. To model the impact force, the two degree of freedom model is used, and the Hamiltonian principle is used to determine the equations governing the problem. In order to validate the results of the analysis, the results of previous studies and numerical simulation with Abaqus software have been used. For the sandwich beam, the effect of the parameters of velocity and mass of impactor, modulus of elasticity of the core and thickness of the core on the Contact force and Central Deflection has been investigated. For beam sandwiches, increasing the mass and velocity of impactor , modulus of elasticity of the core increases the central Deflection and contact force, and also increasing the thickness of the core decreases the Central Deflection and contact force.

  Forging is one of the volumetric forming processes that has been used in the past centuries as an important process in metal forming. In this process, like other metal forming processes, it is important to calculate the force and pressure required to form the part. This dissertation deals with the experimental and numerical study of the forging process of bimetallic rod open molds with flat top and bottom molds. The bimetallic rod consists of a solid cylinder made of copper and a hollow cylinder made of aluminum. The solid cylinder is driven by a press inside the hollow cylinder. Four bimetallic rods with geometric dimensions and the same materials have been made and tested. The rods are placed horizontally between the steel flat molds and are subjected to various heights with laboratory conditions (electric test temperature 24 ° C, no lubricant used between surfaces and the movement speed of the upper mold 0.5 mm / min) by electric press. And force-displacement diagrams of the samples are recorded. A simple tensile test was used to determine the mechanical properties of copper and aluminum materials. The results of the analysis are compared with the data obtained from the finite element method (Abacus software). The purpose of this dissertation is to study and research on the ratio of the effect of height change on the dimensions of the workpiece and the shaping force. The results showed that there is an acceptable agreement between analytical predictions and simulation results so that in the rate of change of diameters less than 10% of the diameter of the original rod, the forces and cross-sectional dimensions of the deformed rod resulting from the simulation and experimental data are well consistent. And the error rate is less than 1%.

In this thesis, a new analytical model is presented that models low-velocity impact on sandwich beams with glare facesheets and foam core and predicts impact damage. The upper and lower facesheets of the beam under study are composed of several layers of fiber-metal composite of Glare type. The mass and spring model is used to simulate the global deformation of the sheet and the Hertz contact law is used to analyze the crushing of the impact site due to impact. By calculating the elastic energy of the facesheets, the energy expended in the crushing of the core and the work of the external force, the potential energy of the system is calculated and by minimizing it, the contact force is calculated as a function of the crushing of the collision site. The governing equations of the problem are solved numerically-analytically and the contact force, global deformation and crushing of the collision site are calculated as a function of time. Then, to investigate and determine the damage conditions in the composite beam, the threshold forces to create the upper facesheet Delamination (separation of the aluminum layer from the fiber layer) and the threshold force to create debonding (separation of the core from the facesheet) are calculated and the damage conditions been investigated. To validate the analytical model, the results of the analytical model are compared with the results of process simulation with Abaqus software (excluding collision damage). In the next step, the parametric analysis of the analytical model is performed in which the effect of change in mass and impact velocity, the effect of changing the material of facesheets (comparison of composite facesheet with Glare facesheet) and the effect of changing core thickness on contact force and beam displacement are investigated. Finally, the effect of facesheet thickness on the load threshold of laminating and debonding damage has been investigated.   

Forging is one of the bulk metalforming processes that has been used in the past centuries as an importantprocess in metal forming. An important point in forging processes is tocalculate the force and pressure required to form the piece.in this dissertation, the process ofopen die forging of a long billet with a circular cross section is analyzed andsimulated. The analysis has been done in two ways, the slab method and thebased on which the equations governing the slab method can be expressed andupper bound method. In the slab method, first a deformation model is presentedfinally the force required to perform the process is calculated.in order to analyze the process by theupper bound method, the deformed material is divided into three regions. Theseareas are separated by shear boundaries. The deformation model in this methodnot solvable, but in the analysis, this equation is solved by force optimization.is expressed by a two-unknown equation. In normal conditions, this equation isIn the first region, the Cartesian coordinate system is used, and in theof matter in this region. Then an allowable velocity field containinganalysis of the second region, the cylindrical coordinate system is used. Thethird region is modeled as the dead region, meaning that there is no movementmathematical relationships are obtained for the expressions of internal, shearhorizontal and normal components for the first region and an allowable velocityfield containing radial and peripheral components for the first and secondestimated.deformation zones are developed. Strain rate components are calculated andand frictional powers. By calculating the powers and optimizing the force, thegeometric shape as well as the force required to perform the process isThe results of the analysis arecompared with the data obtained from the finite element method (Deformsoftware). The results showed that there is an acceptable correlation betweenanalytical predictions and simulation results. Also, the constant effect ofsolution can be used in industrial applications to evaluate the load requiredfriction on small deformations on the amount of force is negligible. Thisissue to choose a deformation device with sufficient capacity.

Abstract:       Nowadays, the spiralwelded pipes (SWPs) are widely used in oil and gas industry. submerged arc welding (SAW) is the most common method for welding thick pipes, especially spiral pipes.The most important disadvantage of spiral pipes is the presence of high of the pipe and contributes to destructive phenomena in the pipe such as stress corrosion crackingresidual stress that are produced during the manufacturing process. Residual stress reduces the strength (SCC). In the recent years, the trend of using finite due to its good accuracy and low cost.element simulations to investigate residual stress has increased significantly In this study, doublesubmerged arc welding (DSAW) of X70 spiral pipe issimulated using finite element software ABAQUS and the residual stress and distortionare investigated. The heat source is modeled as a moving volumetric heat source using DFLUX subroutine and in FORTRAN language. The thermophysical and mechanical properties of X70using the double elipsoidal Goldak model. The application of heat flux in ABAQUS indirect and thermal and mechanical analyzes are performed separately. The finalsteel are temperature dependent. The finite element solution method is also temperaure of thermal analyzes is used as the initial load in the mechanical prevent damages of pipe, it should be reduced. In the final section of thisanalysis. By reviwing the simulation results, it was found that the tensile residual stress has attained high values around welded areas ??and in order to distortion. By comparing the residual stress of the simulation and the experimentalthesis, the hydrostatic test of pipe was simulated and the results showed that the hydrostatic test significantly reduced the residual stress values ??and results.results, it was found that the simulation is in good agreement with experimental       Keywords: Distortion, Residual stress, SubmergedArc Welding, Spiral Welded Pipes   

Ionic polymer metal composites (IPMCs) are a class of Electroactive Polymers that generate bending motions when they are subjected to an electric field. Very low mass and size, low driving voitage, large strain, flexibility and operation in wet conditions are advantages of an (PMC actuator over traditional actuators. Due to its complexity and its nonlinearity, the IPMC modeling is difficult and its behavior is still not fully agreed upon by researchers. In this thesis, fabrication, dynamic modeling and robust control of a strip type and helical shape IPMC actuator is presented. Dynamic model of a cantilever IPMC actuator based on a distributed RC electrical circuit is developed. The RC transmission lines theory is used to derive the simple analytical impedance and actuation model of an IPMC actuator. Considering the highly nonlinear and uncertain dynamics of the IPMC actuator, a feedback controller based on quantitative feedback theory (QFT) is designed to suppress the arbitrary external disturbances and consistently track desired input.

Abstract During the past recent years, application of composite material has been taken into account considerably in different industries because of their significant properties including high strength over low weight. Hence, composite material reinforcement is necessary due to their low strength in comparison with metals and alloys. In this way, nanostructures have been taken into consideration according to their prominent and exceptional mechanical, thermal, chemical and electrical properties. Graphene platelet is one of the novel nanostructures in which is investigated as a proper reinforcement for composite structures with their unique properties. In the present thesis, analytical modeling of the low velocity impact on graphene platelet-reinforced composite plates are considered. The material properties of nanoplatelet reinforced composites are estimated using micromechanical models. The equations of motion are based on a first- order shear deformation theory via a mass-spring contact model in order to modeling of low velocity impact loading on a rectangular plate. The equations of motion are solved with Fourier series which is an accurate solution method. The effects of material property gradient, initial velocity of the impactor, volume fraction distribution and length to width ratio on impact response of plate structures are presented. For presented analytical modeling, contact force, deflection, and strain and stress fields are considered, and as a validation the results of contact force and deflection are compared with analytical modeling of other researchers. The results exhibited that, volume fraction distribution has a notable effect on the impact response of the plate. Key words: composite plates- graphene platelet- low velocity impact.

  Determination of residual stresses and distortion infriction stir welded 2024 Aluminum alloy by ALEnumerical simulation

هستند.  

  roduction of super hydrophobic nano structure coated on various fabrics for oil-water separation

Analysis of wire drawing process with free deformation zone

  Sandwich structures are now widely used in aircraft, industry, rocket, marine, and medical industries due to its advantages such as high strength, lightness and crack-resistant properties. For this purpose, in this dissertation, analytical modeling and numerical simulation of the low velocity shock load on the sandwich beams with thick core and metallic procedures are carried out. The ultimate goal of this thesis is to obtain the process of high plastic deformation based on the strengths of the sandwich core, as well as the calculation of the transverse displacement of the lower sandwich of the beam under the influence of elastic vibration. In the analytic modeling model, using the Galerkin method, the equations governing the height, velocity and acceleration of the sandwich beam are extracted. Further, for analytical modeling of the low velocity shock load on the beams sandwich, matlab software is used as well as numerical simulation of this process using Abkhus software. In analytical modeling and numerical simulation, three locations are considered for applying sandwich blow times. These three locations are 30 cm from the free end of the beam, in the middle of the beam, and 30 cm from the sandwich support axis, respectively. In the results section, a comparison of the final upper extremity profiles for the three places of impact loading was compared for analytical modeling and numerical simulation. In the next section, the comparison of the high degree of deviation in mass and the various impact velocities for the three locations of impact loads has been compared for analytical modeling and numerical simulation. Finally, the comparison of the effect of the core strength, the effect of the impact mass and the effect of the pickup width on the shape of the final profile on the sandwich of the beam for the three places of impact load was compared.

  AbstractDuring the rolling process, the thickness of the metal sheet decreases through the space between the two rolls. Depending on the geometric and physical conditions, this process is categorized in both symmetric and asymmetric rolling. In the asymmetric rolling process, rolls radiuses, their environmental velocity, or frictional conditions between the upper and lower roll of the metal sheet may not be the same. The most important advantage of this process is that of symmetrical mode, reducing torque and reducing the force between rolls, and the most important adverse effect that may occur in this process is the curvature exiting and bending of the sheet when leaving the deformation region. In this thesis, the process of asymmetric cold rolling metal sheet has been studied analytically and numerically. In the analysis, the upper bound method is used. The rigid plastic material has been assumed and the contact arches of the rolls by a sheet have been replaced with a chord like them. The deformation area is divided into three regions and by providing a velocity field for each region, Shear, friction, internal deformation and total power are calculated. The effect of asymmetric factors such as the   roll radius ratio, the different angular velocities of the rolls, the non-uniformity of the friction conditions of the sheet with the upper and lower rolls on the total power and torque, the rolls separating force, and the radius of curvature of the output sheet have been investigated. Numerical analysis of the asymmetric cold rolling process has been done with the help of Deform software, which is very efficient in the field of forming. In order to optimize the process, in the software environment, a program has been written that minimizing the total power of the process and after implementation of the optimal parameters of the process in this process, which is optimized for these optimal solutions, the amount of rolling power is minimized. In the end, the results of the analysis were compared with the analytical and experimental results of other researchers, and the results of the simulation of finite element as well as experimental results. Comparisons of this analysis with experimental values indicate that the analysis carried out in this thesis, in most cases, predict the problems better than those of other researchers. Finally, with the confidence of the present method, the role of the above mentioned parameters is investigated with the aid of upper bound analysis and the effect of angular velocity, rolls radius, and upper and lower rolls friction factor, the percentage reduction of thickness and initial thickness of the input sheet are investigated.Keywords: Asymmetric rolling, upper bound analysis, plain strain.

  In this study, the catalyst of Mn-Na2WO4/H-ZSM-5 with the percentage of 2% and 5% for Mn and Na2WO4 used as co catalyst in the process of oxidation coupling of methane fabricated. Selectivity, methane conversion and yield process were analyzed in several temperatures. The H_ZSM5 using as support, fabricated using hydrothermal method. The SEM, TGA and EDX were used to analyze catalyst properties. The results of experiments show that the selectivity was improved by 53%, the methane conversion reached 51% and the yield process of C2 reached 27% at 800 C.

شبيه سازي رشد ترك در چدن نشكن آستمپر شده تحت سايش خستگي

تحليل بار ضربه اي روي تيرهاي ضخيم ساخته شده از مواد هدفمند با در نظر گرفتن ميدان دمايي

  هدف از انجام اين پژوهش بررسي رفتار استاتيكي و ديناميكي يك استوانه‏ پيزوالكتريك تحت بارگذاري‏ها و شرايط مرزي متنوع مي‏باشد. كه فرض شده است خواص اين استوانه با استفاده از قانون تواني توزيع مواد به صورت تدريجي و پيوسته هم در راستاي شعاعي و هم در راستاي محوري تغيير مي‏كند. پيزوالكتريك‏هاي PZT-4، PZT-8، PZT-5A و PZT-5H به عنوان پايه‏هاي تشكيل دهنده اين استوانه در نظر گرفته شده‏اند. منظور از تحليل رفتار استاتيكي بررسي كمانش سازه تحت بار حرارتي مي‏باشد و منظور از تحليل رفتار ديناميكي بدست آوردن فركانس‏هاي طبيعي و مود شيپ‏ها تحت ارتعاشات آزاد و بدست آوردن ميدان جابجايي و الكتريكي استوانه تحت ارتعاشات اجباري مي‏باشد. در اين پژوهش براي استخراج معادلات ديناميكي حاكم بر ارتعاشات استوانه از اصل هميلتون و براي حل معادلات و بدست آوردن ميدان جابجايي و پتانسيل الكتريكي از تركيب روش تحليلي و روش المان محدود طيفي استفاده شده است. بدين صورت است كه براي تغييرات در راستاي   از بسط فوريه به عنوان يك روش تحليلي و براي تغييرات در راستاي   و   از روش المان محدود طيفي به عنوان يك روش عددي استفاده شده است. اين روش امكان تحليل سه‏بعدي سازه را فراهم كرده است. علاوه بر اين با وجود بزرگ نبودن تغيير شكل‏ها، براي ديدن اثرات حرارتي در ماتريس سختي از تئوري الاستيسيته سه بعدي غيرخطي براي بيان رابطه بين كرنش و ميدان جابجايي استفاده شده است. و براي حل معادلات ديفرانسيلي مربوط به ارتعاشات اجباري نيز از روش نيومارك استفاده شده است كه در مساله ارتعاشات اجباري، دمپينگ رايلي براي سازه در نظر گرفته شده است. در نهايت نيز در هر مرحله تاثير پارامترهاي مختلفي مانند ضخامت استوانه، شاخص‏هاي قانون تواني مواد، بار حرارتي و انواع مختلف شرايط مرزي بر رفتار ارتعاشاتي سازه بررسي شده است. نتايج بدست آمده نشان مي‏دهند كه با افزايش شاخص‏هاي قانون تواني فركانس‏هاي طبيعي سازه افزايش مي‏يابد و با افزايش ضخامت سازه نيز سختي سازه و فركانس‏هاي طبيعي آن بيشتر مي‏شود. بيشتر شدن سختي سازه موجب افزايش دمپينگ رايلي مي‏گردد و بيشتر شدن دمپينگ رايلي نيز باعث كوچكتر شدن زمان نوسانات مي‏شود. از طرف متغير بودن خواص در طول سازه، موجب مي‏شود كه منحني‏هاي جابجايي و پتانسيل الكتريكي ديگر به شكل متقارن نباشند. علاوه براين نتايج نشان مي‏دهند كه اگر بارگذاري از حالت متقارن خارج شود، مودهاي پادمتقارن نيز در سازه به وجود خواهند آمد و حتي ممكن است كه سازه دچار پيچخوردگي شود و تاب بردارد. نمودارهاي مربوط به اثر بار حرارتي نيز نشان مي‏دهند كه با افزايش دما سازه، فركانس‏هاي طبيعي آن كاهش مي‏يابند.

شبيه سازي فرآيند نورد نامتقارن ورق هاي فلزي به روش اجزائ محدود

مدلسازي تحليلي بار ضربه اي سرعت پايين روي صفحات ساندويچي مدور گلار – فوم

  In this paper, an analytical modeling and numerical simulation of the behavior of composite sandwich panels under the effect of low velocity impact are presented and the method of deformation and development of damage caused by impact under different impact loading conditions is investigated.  Composite sandwich panels are multilayered and include a foam core and composite facesheets, are made of graphite-epoxy. In the first part, analytical modeling of low velocity impact load on composite sandwich panels was used to calculate contact force using two degrees of freedom mass spring model, and the contact force between the plate and the impactor according to the Hertz Contact Law is defined. The spring stiffness of the contact area, and the bending and shear stiffnesses of the sandwich panel are calculated. The stiffness of the spring is evaluated by dividing the laminate into two damaged and undamaged regions, and the amounts of these stiffnesses change over time. For solving the equations of motion, the exact solution method of FSDT has been used and by using energy equations, the damaged region radius is calculated.In the second part, analytical modeling of low velocity impact load on composite sandwich panels, regardless of damage, is investigated and compared with the state in which damage considered.  In the next section, the impact process on the laminate is simulated in Abaqus software for a condition where damage is not considered and In order to validate the modeling, the history of contact force and displacement of the center of the laminate derived from analytical modeling and Abaqus software, have been compared.In the next section, determination of the effects of the mass and velocity of impactor and the thickness of the core on the force and displacemant are discussed. At the end, for the analysis of the damage caused by the impact, the threshold force for matrix cracking, delamination, breaking the fibers, and debonding are calculated from the existing semi-experimental methods And to determine the damage, the contact force is calculated from the mass spring model.KeywordsLow velocity impact, Sandwich panels, Composite, Damage

شبيه سازي لوله هاي مخروطي پر شده از فوم تحت بار ضربه اي محوري در نرم افزار آباكوس

تحليل تاثير نانو ذرات خاك رس بر روي استحكام استاتيكي يك ورق پليمري

رابطه كرنش – تغيير مكان خطي است-2 معادلات ورق بر اسا س تئوري تغير شكل برشي مرتبه اول است.

تحليل ديناميكي تير مدرج هدفمند باخاصيت پيزو‌الكتريكي تحت بار مكانيكي والكتريكي با روش اجزا محدود

Analytical modeling of functionally graded carbon nanotube reinforced composite plates under low velocity impact