Mohammad Hossein Yas

   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.

  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

   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.

   In this study, a combination method with fillers was used to prepare anti-fouling polyethersulfone nanofiltration membranes for the removal of pharmaceutical pollutants from aquatic environments. Therefore, graphene oxide nanoparticles functionalized with polyaniline were used to prepare mixed matrix membranes. The effect of the modification method used on the separation performance and morphology of the newly prepared membranes was investigated. To identify the prepared membranes, Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), X-ray diffraction spectroscopy (EDX), contact angle measurement, and pore size and porosity calculation were used. FTIR spectroscopy indicated the formation of functional groups on the surface of the filler. In fact, this analysis emphasized the successfulness of the modification method used in the desired membrane. The results showed that the permeate flux of the modified membrane was about 3.5 times higher than that of the unmodified polyethersulfone membrane. Additionally, the surface-modified membrane had a lower contact angle and superior anti-fouling properties compared to the unmodified membrane. To identify membranes prepared through Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), X-ray diffraction spectroscopy (EDX), contact angle measurement, and pore size and porosity calculation were used. FTIR spectroscopy showed that functional groups were formed on the surface of the filler. In fact, this successful analysis emphasized the effectiveness of the modification method used in the membrane under study. The results showed that the permeation flux of the modified membrane was about 3.5 times that of the unmodified polysulfone membrane. Additionally, the surface-modified membrane had a lower contact angle and better anti-fouling properties than the unmodified membrane. Comparing the performance of membranes prepared for removing pharmaceutical compounds from aqueous environments indicates that the results are almost similar. However, the removal efficiency of drugs by a mixed matrix membrane containing graphene oxide nanoparticles functionalized with polyaniline at a weight percentage of 0.25 (PES/G-Pu 0.25 membrane) is slightly higher than other membranes due to the greater influence of the filler on the adsorption and surface charge properties of the membrane.   

  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.

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.

   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.

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%.

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 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.  

Thermal   vibrations of composite beams reinforced by Boron Nitride nonotubes

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.

طراحي و ساخت ماشين نورد نامتقارن ورق هاي فلزي

  this present literature investigates the thermal buckling and vibration of functionally graded porous nanocomposite beam reinforced by graphene platelets based on Timoshenko beam theory . This study focuses on the effect of the porosity distribution , porosity   coefficient and the effect of the variou   GPLs dispersion pattern , size and geometry of GPLs ,as well as the influence of   eam boundary conditions ,slenderness ratio and the thermal gradient   . Because of the negative thermal expansion coefficent of graphene , the critical thermal buckling gradient is in a high range. the numerical results suggest that introducing the little amount of GPLs enhances remarkably the stiffness of the present structure ,on the   other hand ,due to negative thermal expansion coefficient of nano fillers ,the studied beam acceptably behaves in high thermal gradient .Both porosity distribution and GPLs pattern obviously affect on frequency increment   although the effect of GPLs pattern is more .In a certain ,when the porosity coefficient increases ,the frequency increment decreases , though this decrease is much less . the effect of   oundary conditions on frequency increment is not so much. According to the results ,the relation between slenderness ratio and frequency is inverse.  Analyzing the effect of   increase on beam frequency suggests that increasing thermal gradient , the beam frequency lessens. Meantime The effect of   increase on frequency increment is different in beams with various porosity distributions and GPLs pattern.

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

  Smart materials are a new term for materials with ability of understanding and processing environmental events and show an appropriate response to them. These materials are able to change in their dimensions, colors and energy in a reversible manner in response to the physical or chemical effects of the environment. In recent years, using intelligent materials has been expanded in a wide range of new technologies. Magnetolectroelastic materials are the most important types of these materials, which provide the ability to interact between magnetic, electrical and elastic properties in a single compound form. In this present research free vibration, static and dynamic response of functionally graded Magnetolectroelastic beam have been investigated for these materials. The studied beam has different support conditions and relations are based on two-dimensional elasticity theory. The equations of motion are extracted using the Hamilton principle and solved by finite element method. The mechanical, electrical, and magnetic properties of this beam vary in thickness according to the power low distribution. Finally, the accuracy of the responses was compared with the results of previous studies including the static and dynamic response of the system, the effect of various geometric parameters, auxiliary and volume fraction indices on natural frequencies were investigated. According to the results, it is observed that with increasing the volume fraction of functionally graded material, the natural frequency increases. In the static response study, with the increase of the volume fraction indices in different supporting conditions, the deviation of the middle of the beam decreases. The greatest divergence of the middle in the beam is with clamped-free boundary condition and the middle cavity deviation is reduced in beams with simply supported, clamped-simply and clamped-clamped boundary conditions, respectively. The solutions obtained from finite element solvers based on the two-dimensional elasticity theory are in good agreements with theory of beams.

  Today, nanotechnology research is underway at a fast pace, and day by day various applications of this technology in various areas of life are made clear to humans. In the case of nanofibres, this is the case, and is used as one of the most important nanotechnology products in many areas. Nano fibers have attracted particular attention in recent decades due to their mechanical, physical and chemical properties, such as the high surface area, the bond between the fibers, the microfacial space between the fibers, and high porosity. Among the many available techniques for the preparation of nanofibres, the electrospinning method is a simple and efficient method that, with precise control of the operating conditions and the characteristics of the polymer solution, results in the production of more uniform nanostructures. In this study, the application of polyacrylonitrile / Schiff base alumoxane nanofibers was tested by electrospining and applied to experimental studies of the effects of conductivity properties and the removal of heavy metals from aqueous solutions using polyacrylonitrile / Schiff base alumoxane nanofibers. First, the Schiff base alumoxane and 2-mercaptoacetic acid alumoxane were synthesized first, and Schiff base alumoxane nanoparticles were investigated in a nanofibre structure to remove heavy metals from aqueous solutions using Design expert7 software. The polyacrylonitrile/Schiff base alumoxane nanocomposites were highly efficient in removing 97% of lead and 94% cadmium ions from aqueous solutions. To test the conductivity of nanofibres, 2-mercaptoacetic acid alumoxane nanoparticles have also been used with palladium nanoparticles in nanofibers with copper electrolytes and silver electroplating. Based on the results, the highest conductivity of 316.45(s/m) is about 2.5% of the 2-mercapto-acetic acid alumoxane nanoparticle and 0.03% of palladium.  

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

    تحليل رفتار مكانيكي ميكرو- سازه‌ها به‌‌عنوان يكي از اجزاي اساسي سيستم‌هاي نانو-ميكرو الكترومكانيك از اهميت خاصي در بين محققين رشته مهندسي مكانيك برخوردار مي‌باشد. در اين راستا، ميكرو‌-تيرها در سيستم‌هاي ميكرو-نانو مانند: ميكرو‌پمپ‌ها، ميكرو‌آينه‌ها و ميكرو‌سنسور‌ها نقش مهمي را ايفا مي‌نمايند. با توجه به مطالب ذكر شده تحليل رفتار ميكرو سازه‌هاي ساخته شده از مواد تابعي براي طراحي دقيق و مناسب از اهميت فوق العاده‌اي برخوردار مي‌باشد. از مهمترين پارامترهاي طراحي داده‌هاي مربوط به آناليز ارتعاشات آزاد و اجباري سازه هاي مي‌باشد. همچنين براي انجام تحليل مناسب و حاصل شدن نتايج دقيق‌تر بايد همزمان از يكي از   تئوري‌هاي محيط پيوسته غيركلاسيك و مدل تغيير شكل برشي استفاده نمود. هدف اصلي پايان نامه تحليل و بررسي تاثير گراديان حرارت بر روي تير كامپوزيتي تقويت شده با نانو لوله هاي نيتريد بور مي­باشد.كه تير موردنظر بر اساس تير تيمو شنكو مدل سازي شده وقوانين حاكم بر اين تير براي حل اين مساله كمك گرفته شده است.در اين پايان نامه مقدار خيز وتنش و كرنش   محوري و برشي بررسي شده است وبا افزيش درصدجرمي نانولوله هاي نيتريد بور مقدار خيز تير كاهش يافت همچنين تاثير پارامترهاي همچون، نحوه‌ي توزيع نانولوله در راستاي ضخامت تير، شرايط مرزي مختلف ونسبت لاغري تير بر روي جابه‌جايي و تنش بررسي شده است و نتايج بدست آمده نشان مي‌دهد كه تغيير هر كدام از اين پارامترها تاثير بسزايي بر روي جابه‌جايي و تنش دارد.                 واژگان كليدي: مكانيك محيط پيوسته غير‌كلاسيك، تير، تئوري تنش برشي ،گراديان حرارتي.

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

  textile colors are among the most advanced compounds that are believed to be in industrial wastewater and will cause many environmental problems. so removing these pollutants from these wastewater is important The purpose of this study was to remove the methylene blue color using a packed bed reactor of the immobilized cells of the ralstonia-eutropha on the basis of kissiris To investigate the cometabolism kinetics of this color, we proposed a model to predict the dynamic trend of the removal of this material. To do this, initially, the immobilization   of the ralstonia eutropha cell in a bioreactor was performed using a culture medium containing glucose as a carbon source. Then, by using spectrophotometric method, the amount of cell growth in each stage of the sampling, the amount of glucose remaining, and also the methylene blue removal efficiency obtained. The results showed that the porosity and the high specific surface of kissiris produced the possibility of effective binding of Ralstonia iotropha bacteria in a packed bed reactor, and immobilized cells had high levels of high removal of methylene blue in a high concentration, in a concentration of 200 mg / L of methylene blue on the basis of mass transfer limitations As a result of reducing inhibition, Decolorization was observed at 65% interval. The Hendell model was used to determine the traditional color removal due to the decomposition rate at high concentrations, which indicated the role of methylene blue inhibition of cell degradation enzymes. The kinetics parameters were qmax = 1.250 mg / gh and K / m = 139.0 mg L-1 and K / I = 190.1 mg L-1, respectively. Then, using the kinetic parameters, dynamic color modeling was performed. The results indicated that the low concentration of the immobilized system to remove the color from the free cellular system was not justified, but with the increasing methylene blue concentration and the inhibitory effect, the use of immobilized system resulted in an effective reduction of the concentration On the surface and inside the biocatalyst and the resulting reduction of concentration to Due to the limits of external and internal mass transfer, the reduced methylene blue inhibition has a better performance than the free cellular system....

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.