جستجوی مقالات مرتبط با کلیدواژه "آلومینیوم 7075" در نشریات گروه "مکانیک"

Machining with rotary tools using all insert circumstances instead of a specific cutting edge reduces tool wear and thus increases its life. This method, in addition to the simplicity of the mechanism, is considered one of the cheapest environmentally friendly processes. The important role of the inclination angle on the outputs has been pointed out. For this purpose, according to the forces and geometrical conditions, a suitable tool holder is designed and built in which it is possible to change the inclination angle. Aluminum 7075 has been selected as the workpiece, and the turning operation has been done using appropriate tools. The surface roughness of the workpiece is measured based on input parameters such as feed and inclination angle. The design of the experiment is based on full factorial design, and surface roughness has been measured based on the angle of inclination in three modes and three different feeds. Reducing the inclination angle and the feed has improved the quality of the surface. The best surface roughness has been at an inclination angle of 5 degrees and an advance of 0.12 mm/round. The shape of the chips has also been investigated. Ribbon-type chips were formed at higher inclination angles, but conical helical chips were formed as the inclination angle decreased.

In this paper, the effect of including SiC nanoparticles in the weld zone on the maximum shear strength of friction stir lap welded 7075 aluminum alloy is investigated, both experimentally and numerically. This objective is carried out by studying the effects of rotational and transverse speeds, tilt angle, the shape of the tool and the penetration depth. The numerical investigation is based on developing an FE model by means of Deform and ABAQUS to simulate the welding procedure, which results are verified by the experimental findings. Experimental procedure is designed based on Taguchi method. The verification of the developed FE model shows that the simulation results are in proper agreement with the experimental findings. In general, including SiC nanoparticles in the weld zone can increase the maximum shear strength up to 24%, compared to the case of where the specimens are welded without SiC. Furthermore, applying the threaded tapered tool leads to higher shear strength in comparison with the squared shape tool, i.e., the strength of the specimens welded by threaded tapered tool are 4 to 5% higher without SiC inclusion and 4 to 7.5% higher with SiC, compared to the same case welded by squared tool. In addition, while the rotational speed has the highest influence on the findings, the tilt angle does not affect the results that much.

7075 aluminum alloy, with a high strength-to-weight ratio and good impact strength, is one of the useful materials in the aerospace and automotive industries. However, this alloy has limitations such as poor formability, high spring back at low temperatures, and thermal distortion during hot forming. To overcome these limitations, a thermomechanical process including solution heat treatment, forming, and quenching in the die can be used. In this research, for producing a U-shape part with a depth of 30 mm, a 7075 sheet with a thickness of 2 mm was first subjected to solution heat treatment at a temperature of 480 ℃, and then was immediately transferred to a cooling die to be formed at a temperature of 4 ℃ under a hold time of 20 seconds. Finally, the part was artificially aged to improve its mechanical properties. A finite element simulation of the process using the ABAQUS software was also performed. Good dimensional accuracy and absence of rupture in the final U part, close agreement between the experimental and simulation results, an acceptable 25% reduction in elongation, very close tensile strength to the base material, and microhardness equal to 95% of the base material are the results of this research.

abrasive water jet is one of the most popular cutting methods today due to its ability and unique features such as the ability to cut complex shapes as well as the wide range of materials and non - creation of thermal distortion at the cutting site. The accuracy of the process is mainly due to selecting the cutting parameters. The sheet used in this study is aluminum 7075 with a thickness of 25 mm. In this research, for water jet pressure, forward speed and nozzle distance to the surface of the workpiece, three surfaces and for the impingement angle of two surfaces were considered. In order to investigate the quality of the cut - off area, the effect of process parameters on the high and low width of the cut section and also the cut - surface slope is investigated. Finally, the cut gap created by this process has special geometrical features that in some cases is the limitation of the process. The results showed that the change in the direction of the water jet from the perpendicular to the surface of the work piece, although the width of the cutting crack cannot be changed, the surface quality decreases and the cutting surface slope increases.

While bare Aluminum does not have the desired properties for aerospace and naval industries, when converted to composite by reinforcing materials, the desired mechanical and other properties are achieved. In this study, Aluminum 7075-T6 was selected as the base phase and Silicon Carbide (SiC) particles were used as the reinforcing phase for the composite for the experiments on the yield strength, ultimate tensile strength, and fatigue life. According to the experiment design, the SiC was prepared with three different particle sizes, in nanometer, submicron and micron scales. SiC powder with different mass fractions with Aluminum was cast by vortex casting by a resistive furnace equipped with an electromagnetic coil and a vacuum pump, and the composite samples were cast according to the experimental design. The samples were then subjected to dissolution. Afterward, T6 heat treatment was performed on the samples. Ultimately, the prepared experimental samples were subjected to tensile and fatigue tests, followed by the relevant standards. According to the results, reinforcement of aluminum 7075-T6 with SiC particles improved properties such as yield strength, ultimate tensile strength, and fatigue life, but reduced the elongation and ductility of the samples. The results indicate that 1% sample with nanoparticle size has improved the final tensile strength by 21.33% and has the highest fatigue strength.

To predict static aeroelastic behavior accurately, two-way fluid and structure interaction (FSI) coupling methods are used to calculate the static deformations and aerodynamic characteristics of the deformed rocket. According to the studies, little research has been done on the weight reduction of space structures. Therefore, due to the stratigicness of the Fin of space structures, the mechanical behavior of the sheets for the construction of the Fin has been experimentally studied using a constrained groove pressing (CGP) method and a comparison has been done between the amounts of deviation caused for a rocket flying in different Mach numbers and different angles of attack, by simulating a two-way FSI Method for WAF and Flat Fins models with two types of material, the CGP 7075-T6 aluminum, and the 4130 steel. Results of constrained groove pressing show that with the increase in the steps of this process, 7075-T6 aluminum with 38% increase of yield strength in fourth transit, 34% increase in tensile strength, 40 percent decrease in elongation, and 62% increase in toughness relative to the prototype, will be produced. The total deviation in WAF Fin is much less than the flat Fin. Also, deviations of Fin made of CGP 7075-T6 aluminum is less than the Fin made of 4130 steel.

The ECAP-Conform is one of the newest and less known processes that improve mechanical properties. In the present study, the effective parameters of the ECAP-Conform process for AA7075 have been investigated. Influence of parameters such as roller radius, bending angle, die channel angles, rod/roll friction coefficient, rod/die friction coefficient, and the aspect ratio of the die groove on the torque, the applied force on the die, the stress, and the effective plastic strain, the output rod curvature, and the strain distribution uniformity have been investigated. The design of experiments was carried out based on the response surface method by the Minitab software, and simulations were performed using the ABAQUS software. To validate the FEM, the ECAP-Conform process of AA7075 rod was performed and the comparison of experimental and numerical results have acceptable compliance (7.5% error). It was found that the die channel angles and the rod/die friction coefficient have a more significant effect on all responses. Moreover, to maximize the imposed strain and strength, and to minimize the process torque and curvature, as well as achieving a uniform distribution of strain, the optimal output parameters have been obtained.

In this research, the surface of aluminum 7075-T6 was reinforced by pumice micro and nanoparticles using the friction stir process (FSP). First, optimum parameters of pass number (1 & 4 pass), travel speed (40 & 80 mm/min) and tool rotation rate (800 & 1200 rpm) considering the microstructure, hardness and resistance to wear were selected. Results showed that with increasing the pass number, decreasing the travel speed and increasing the tool rotation rate, the grain size in stirred zone (according to the microscopy images) decreased, while the hardness (according to the Vickers micro-hardness test results) and resistance to wear (according to the pin on disk test results) increased. Under conditions of single pass, travel speed of 80 mm/min and tool rotation rate of 800 rpm, average grain size in stirred zone was 10 micron; while under conditions of four passes, travel speed of 40 mm/min and tool rotation rate of 1200 rpm it was reduced to 5 micron that led to an increase in average micro-hardness from 80.2 to 94.6 Vickers and a decrease in wear amount from 33 to 27 mg after a sliding distance of 1000 m. By addition of pumice micro and nanoparticles, average micro-hardness was increased to 99.6 and 107.8 Vickers and wear amount was decreased to 24 and 20 mg, respectively.

Severe Plastic Deformation (SPD) processes are widely used in order to decrease the grain size and improve mechanical properties of engineering alloys. Equal- Channel Angular Pressing (ECAP) is one of such processes that can be performed on bulk materials. In this paper effect of ECAP and heattreatment coupling on 7075 Aluminum alloy was investigated. ECAP was performed on samples after solution treatment. Considerable grain size decrease was observed. Sample’s hardness was increased after ECAP. In order to investigate the effect of solution treatment time on hardness, samples were solution treated at 500° degrees for 5, 10 and 15 hours. It was shown that increasing the solution treatment time from 5 to 15 hours decreases the hardness in solid solution state from 45 to 39 HRB due to increase in the solution of the initial precipitates. Aging treatment at 80 and 120 degrees was performed to further harden the alloy. It was observed that aging treatment after ECAP increases the hardness of all samples. Increasing the solution treatment time from 5 to 15 hours increases the maximum hardness in aging state at 120 degrees from 92 to 98 HRB.

Development of research on aluminum light joints is one of the most effective ways to reduce fuel consumption¡ increase strength and development of aerial structures. In this study¡ the feasibility of Tjoint AA7075 aluminum alloy with using friction stir welding process was studied. For this purpose the AA7075 aluminum joint with different tool offset¡ plunge depth¡ linear and rotational speeds were studied. In order to better understanding the production and distribution of heat¡ welding process was simulated using commercial fluent package software. Depending on the selected parameters in the process¡ the strongest connection was produced in the 1.5mm tool offset on advancing side¡ the 0.4 mm plunge depth¡ 2o tool tilt angle¡ and 1325 rpm rotational speed and 69 mm/min linear velocity¡ respectively. The failure position of all tensile samples was located on the T appendage. Tunnel void was the major defect in the joints which disappeared with increased heat input and cooling rate. The strongest connection which produced in these experiments had 181 MPa strength that nearly 80% of the aluminum base metal. The connection elongation after the tensile test was close to 11 mm.