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Aerodynamic and optimal design of a blade of a horizontal axis wind turbine (HAWT) has been performed in order to extract maximum power output with considering the strength of the blade structure resulted from different loads and moments. A design procedure is developed based on the Blade Element Momentum (BEM) theory and suitable correction factors are implemented to include three-dimensionality effects on the turbine performance. The design process has been modified to achieve the maximum power by searching an optimal chord distribution along the blade. Based on the aerodynamic design, the blade loads have been extracted and the blade mechanical strength has been investigated by analyzing the thickness of the blade surface and the blade material. The developed numerical model can be considered as a suitable tool for aerodynamically and mechanically design of a turbine blade. The results for a 500 W turbine show that the turbine performance improves by 5% approximately, by modifying chord radial distribution. Yield stress analysis shows the effect of introduced chord distribution on the blade strength, in different blade thicknesses and different blade materials. In addition, optimum tip speed ratio for having favorable mechanical safety factor is derived. Three different airfoil are examined for this investigation and comparing their mechanical safety factor.

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Concrete is one of the most widely used building materials for fragile behavior. The addition of fiber to concrete affects the behavior of tensile strength, tensile strength, flexural strength, modulus of elasticity, impact resistance and some other mechanical properties of concrete. For this purpose, an experimental research was carried out to provide an experimental model of the flexural fatigue life of reinforced concrete with macrosynthetic fibers by constructing concrete joists with three different thicknesses of 80, 100 and 150 mm. SN models (stress-loading) and HN (thickness-loading) was presented. The results showed that increasing the thickness of concrete samples and adding fibers to concrete mixture increases the fatigue life. Also, the addition of fibers to concrete samples measured the thickness of the sample for the stress level of 0.7 final stresses at 12.45-8.24%, for the stress level of 0.8, the final stress was 22.15-5.45%, and for the stress level of 0.9, the final stress decreased to 22.15% -10.18% Finds. Fiber-reinforced concrete is a type of concrete that is mixed with fiber. Various types of fibers are used to produce fiber-reinforced concrete, which include glass, polymer, carbon and steel. In the present research, macro-synthetic polymer fibers were used. Some of the consequences of applying macro-synthetic fibers in concrete include reduced shrinkage of fresh and hardened concrete, increased ductility, increased strength against fatigue stresses, increased durability and lifetime of concrete, improved concrete mechanical properties (tensile strength, flexural strength, etc.), control of secondary/thermal cracks of concrete, preventing the in-depth propagation of cracks, post-cracking chargeability and reduced permeability against chloride and sulfate ions .In most of the studies, the concrete sample's thickness is increased along with the increase in the beam's length; however, in the present work, only thickness of the beam samples with and without fibers was changed and other dimensions of the samples were kept constant in order to investigate merely the effect of increased thickness. Accordingly, effect of the size of macro-synthetic fiber-reinforced concrete sample at different thicknesses was assessed via fatigue life variations. The intertwisted fibers were added to the concrete mixture by 0.4 vol.%. Then, from each sample, three specimens were made. The obtained results were averaged and, then, recorded in the relevant tables. The following cases were considered as the research objectives: - Effect of sample size on fatigue life of concrete samples - Effect of adding macro-synthetic fibers on fatigue life In order to determine flexural fatigue of the concrete samples with the above-mentioned geometric properties, UTM device was used. The test was performed with constant sinusoidal loading at the frequency of 10 Hz. The input information for the test included loading curve shape, minimum and maximum loading values, loading frequency, and maximum number of loadings, all of which were defined as the input. To measure the values of stress levels in order for measuring the loading values, first, the average of the samples' flexural strength had to be determined; then, the stress levels could be calculated from the obtained results. also A cross sectional analysis of the broken sample showed that most of the sample failure was from aggregate and the mixture design was suitable.

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To determination of equal-channel angular pressing(ECAP) process on the stress-strain behavior of  steel core of steel/copper bimetal and also effect of Cu-shell thickness on the created surface stretch during ECAP, the bimetallic samples composed of steel rods with 8 mm diameter and copper shells with 0.75 mm thickness are prepared. The both bimetallic samples and steel rods with 9.5 mm are subjected to consecutive ECAP process using die with inner angle 90^o and an outer curvature corner angle of 30^o. The applied load and punch displacement are recorded during samples passing through an ECAP die. The tensile testing is carried out on both the initial and ECAPed series. Moreover, dependence of surface stretch to diameters, shell thickness and strength properties of constituents of core/shell bimetallic rods is analytically modeled. Then, the finite element method(FEM) is used to investigate the effect of Cu-shell thickness. The obtained results revealed that the ultimate tensile strength of bimetallic core and steel rods are improved approximately 60% and 108% by ECAP deformation, respectively. The applied punch load for passing of bimetallic sample through an ECAP die is 54% less than the ones for steel rod. According to the FEM results, the maximum value of surface stretch is linearly decreased with increasing the thickness of copper shell. The obtained results show a good agreement between the analytical model and FEM approach.

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The flow forming process is widely used in the production of axisymmetric industrial parts. The advantage of the flow forming process over other manufacturing methods is the use of simple tooling, reduced forming loads due to localized deformation, and enhanced mechanical properties and surface quality of finished parts. In this research, the warm flow forming process of AA6061-O aluminum alloy has been investigated for the first time. For this purpose, laboratory equipment and samples were designed and fabricated. In this study, the effect of temperature, thickness reduction, and number of passes (number of forming steps) on dimensional accuracy (thickness variation) and mechanical properties of warm flow formed AA6061-O alloys pipes have been experimentally investigated. The experimental results show that flow forming increases the strength and decreases the ductility of the formed pipe at all process levels compared to the initial non-flow forming pipe. However, the ductility of the pipe increases and its strength and microhardness decrease by increasing the forming temperature from 20 to 300 ° C. While with increasing the percentage of thickness reduction from 20% to 60% at a constant forming temperature, the strength and micro-hardness of the warm flow-formed pipe increases and its ductility decreases.

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The grinding process is one of the most important and widely used machining processes to achieve the desired surface quality and dimensional accuracy. Since the undeformed chip thickness is not a constant value in the grinding process and is changing independently and momentarily for each abrasive, the determination of the undeformed chip thickness accurately is essential to determine the grinding forces and surface topography of the grinding wheel. Previous studies on grinding forces were mainly regardless of the micro-mechanisms between the abrasive and the workpiece. On the other hand, only the average values ​​of forces could be calculated by determining the average value for undeformed chip thickness. In this study, a new analytical model with the approach of kinematic-geometric analysis of abrasive grain trajectory is presented to determine the undeformed chip thickness and subsequent grinding forces. This model predicts the components of normal and tangential grinding forces (including sliding, plowing, and cutting forces) accurately and in detail based on the instantaneous undeformed chip thickness obtained from the kinematic analysis of abrasive movement and micro-mechanisms between abrasive and the workpiece. In the end, experimental tests were performed to validate the theoretical model.

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One of the forming pipes methods is the rotary draw bending process. Today, bending of thin-walled pipes with low radius of curvature is widely used in the automotive, military and aerospace industries, which is used to bend high-strength pipes. In this paper, at first the necessary models were created to simulate the bending process of the rotary pipe, and then the necessary mechanical and physical properties for stainless steel 304 and elastomers were determined. Then, experimental and numerical study of the forming force and changes in pipe wall thickness were performed. The process simulation was analytically performed using polyurethane elastomeric mandrels and nitrile rubber based on ABAQUS finite element software on 304 steel. The results show a good agreement between simulation and experimental results. Finally, the effects of process parameters including mandrel type, pipe diameter and bending radius were analyzed on the maximum forming force by factorial analysis. The results showed that the maximum forming force for both types of mandrel materials is obtained for pipes with small diameter and high curvature radius. Also, the bending forces increase 5 times by 30%increasing the bending radius, for pipes with smaller diameters. In addition, in equal diameter and radius of bending, the bending forces in the case of using polyurethane mandrel are 25% more than nitrile mandrel.

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In this study, bending of titanium tubes using steel balls in 0.5 and 0.85 mm sizes and resistance heating with experimental and simulation methods have been investigated. In order to apply temperature in rotatory draw bending of tubes, electric current cables were connected to both sides of the tube, and experiments were performed at room temperatures, 100℃, 200℃, 300℃ and 400 ℃ with a bending ratio of 1.8 and a bending angle of 90 ° was done. After the experiments, cross-sectional distortion, wrinkles, cracking and thickness distribution of bent tubes were investigated. The results of this study showed that in the case of bending at room temperature with and without metal balls, the tubes could not be bent. In the bending process with a constant speed of 0.8 Rad/s, by placing metal balls inside the tube and increasing the temperature 100℃, 200℃ and 300℃, the thickening in the intrados of ​​the bent tube decreased by 9.8% and the thinning at the extrados of the bent tube increased by 8.4%. Also, by changing the bending speed from 0.8 to 0.4 Rad/s the cracking defect was eliminated at 400℃. Due to increased pressure due to steel balls in bending area, cross section distortion in tubes decreased by 10.4%. The best bending conditions and the least amount of defects were obtained at 300℃ with steel balls.

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electrical discharge coating (EDC) is the simplest way to deposit a thin or thick coating on the surface of a substrate to change the properties of this undesirable layer. In the EDC process, the molten pool produced due to sparking in electrical discharge is combined with material particles from the loosely bonded compacted electrode (green compacted) and then rapidly cooled to form a coated layer. Extensive methods for coating the surface of the substrate exist such as electroplating, electroless plating, vapor deposition methods, thermal spraying and many others. These processes have disadvantages such as high capital costs, complexity, higher setup complexity and space requirements that limit their implementation to some extent. Among all coating methods, EDC has advantages over other coating methods. For EDC, there is no need to set up any equipment to create a vacuum or isolation environment around the bed. Also, only by changing the different variables of the machine, the thickness can be changed and the characteristics of the coating layer can be controlled. This study focuses on chrome ceramic coatings formed in the EDC process on stainless steel substrates (ST37) with process parameters with 8 amp current and 100 µs on time. The results showed that the hardness of stainless steel coated with chromium and copper increased to 1284 (HV) in electrical discharge.
 

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Flow forming is one of the advanced methods for producing low thickness cylindrical parts. The dimensional accuracy of pipes produced by the flow forming method is much higher than other methods and this method is widely used in the aerospace industry. In this research, the effect of number flow forming passes has been investigated on the mechanical properties and microstructure of AISI4130 steel. Three stages of thickness reduction have been successfully completed and in the fourth stage, the tube was fractured. In the first stage of this pass, the desired steel thickness has changed from 14.2 mm to 9.3 mm. In the second stage, the thickness reached 2.6 mm, in the third stage to a thickness of 2.3 mm and in the fourth stage by reaching 1.8 mm thick, there has been a tear in the pipe. During the flow forming process, the maximum amount of 84.5% thickness reduction can be achieved. To achieve a higher percentage of thickness reduction, it is necessary to re-anneal the flow formed sample. To investigate the tensile properties, tensile tests have been done through both longitudinal and circumferential directions. According to the results, it was found that the flow forming operation on this steel has increased the hardness and yield, and ultimate strength of the material at every stage. Also, the hard work done at every stage on this steel by maintaining the ferritic pearlite-ferritic structure has caused finer grain structure and elongation of the grains.
 

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At the end of the forming process, when the part is removed from the mandrel and the matrix and the part is loaded, a deformation occurs in the part, and this deformation after forming is called spring back. This research was carried out in order to experimentally determine the spring return of stainless steel 316 and carbon steel ST37 with different thicknesses in C-die forming and compare it with finite element simulation. The parts with three thicknesses of 1, 1.5, and 2 mm, forming and the geometrical dimensions of the spring back of the sheets have been verified. The results showed that the experimental spring back in the finite element simulation is consistent with the test, and also by reducing the thickness, spring back increases, which is affected by perfect elastic zone and surface plastic strain and membrane and bending stress.

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   This paper investigates the effects of various parameters, including support conditions, the Demand to Capacity Ratio (DCR) of the member under gravitational loads, the section factor (the ratio of perimeter to area), and the fire insulation coating thickness on the fire resistance duration of steel columns under fire effects. To this end, four steel H-shaped columns and four steel tube columns with the height of 4 meters, are subjected to the standard fire curve (ASTM E119) from four sides, and the effects of different parameters are studied. Initially, a heat transfer analysis is carried out on the 2D cross-section of columns with its fire insulation coating in Abaqus software. Then, a nonlinear general static analysis is performed on a 3D steel column model subjected to gravity (concentrated axial) and thermal loading simultaneously.
Results of this study indicate that the columns only expand but do not deform significantly until approximately 250^oC. After that, a decrease in the steel strength and stiffness and as a result, a decrease in fire resistance and bearing capacity of the steel column occurs. This is accompanied by an increase in the mid-span horizontal displacement of the column and an increase in the effect of the P-δ bending moment, which results in the column failure at about 500^oC to 650^oC. The results also show that the fixed or pin support condition on the bottom end of the column does not significantly affect the column failure time under fire effects. In square box columns, the increase in the section thickness increases the fire resistance duration of the steel column. However, increasing the section width does not significantly affect the column failure time. In H-shaped columns, the increase in the flange thickness and the decrease in the column web height increases the column fire resistance duration. On the other hand, the results indicate that the section factor, the initial load level of the member due to gravitational loads, and the fire insulation coating thickness have a significant effect on column failure time to the extent that with the increase in DCR of the member from 0.3 to 0.7, the failure time of the column decreases by about 25 to 35 minutes.
Based on the results of this study, two formulae have been presented to calculate the failure time of protected columns by CAFCO300. The results of these formulae have also been compared to a relationship proposed in Chapter 10 of the Iranian National Building Regulations. It is found that the results of these formulae are fairly similar, when the initial DCR equals 0.7. Therefore, the relationships of the present study provide a more optimal and accurate design of the fire insulation coating thickness, because this load level can only occur in structures that are not designed for lateral loads and are designed only under gravitational loads.