IRANIAN JOURNAL OF MANUFACTURING ENGINEERING
Year:2017 | Volume:4 | Issue:1 |Papers Count:6

Today, in many industrial processes, the use of hydraulic systems for power transmission is growing. The need of improving more accurate and faster dynamic performance of hydraulic systems has increased. Hydraulic valves are key components in hydraulic systems that improving their performance causes increasing in hydraulic systems efficiency and accuracy. In this paper, a voice coil motor is designed for a hydraulic servo valve and optimized using genetic algorithm. Firstly, a preliminary design according to the size limit has been investigated using a combination of magnet Halbach. Then optimum design is provided based on genetic algorithms to optimize the size and lack of saturation magnetic flux to achieve power needed. Finally, the achieving results of the optimization design utilizing a Halbach magnet array, is evaluated using finite element analysis. The results show the improvement in time of performance about %3/41 new actuator compared to hydraulic valve's solenoid.

This article studies the impact force during the sub resonant vibrations on mechanical properties and microstructure of carbon steel welded by GMAW process. For testing, sheets of carbon steel welded together in accordance with welding procedure Specification. 3 samples under various forces and vibration functions as a control sample (no vibration) is considered. Tests for hardness, tensile, impact and the microstructure of all samples is conducted in accordance with current standards. The results, increasing the yield strength of the samples has shown resonant. The yield strength of 319 MPa and the samples in the sample without a resonant vibration, 381, 363, 421 MPa. Impact resistance test results of the samples showed increased impact resistance is resonant examples. Impact strength of 5. 5 joules without vibration and resonant samples 16. 5, 18, 10 is Jules. Vickers hardness test results obtained from the samples, reducing the hardness of the resonant shows. Sample without vibration in the heat effected zone 189 Vickers and examples of resonant 141, 152, 120 Vickers is also hardness values in the weld samples without vibration of 244 Vickers and examples of resonant 178, 193, 103 Vickers is. The results of microstructural investigations, did not show significant changes.

In this article, the effect of cryogenic cycling on flexural properties of fiber metal laminate (FML) has been investigated. This laminates were composed by two aluminum 2024-T3 plates and an epoxy matrix composite ply formed by four layers of basalt fibers by hand lay-up technique. Various surface treatments include mechanical (grinding), chemical (etching) and electrochemical (anodizing) were used for improving the adhesion between polymer composite layer and aluminum sheet. Each cryogenic cycle was carried out in 4 min and temperature range was between-40 ° C and 25 ° C. Flexural properties were evaluated on samples after 15 and 30 cycles and compared to non-exposed samples. While the cryogenic cycling decreased the flexural strength of the FML with etched aluminum, increasing at first, and then decreasing after a while was observed in the FML with anodized aluminum. About samples that the FML with grinded aluminum, both of flexural modulus and fracture energy increased at first and then decreased; while the flexural strength decreased continuously. Evaluation of optical microscope showed that the reason of decreasing in flexural properties about samples with etched aluminum and also decreasing in flexural strength for samples with grinded aluminum after cycles is changing in mechanism of failure from failure of composite to separation between layers of FML; while about FMLs with anodized aluminum, the only observed mechanism was failure of composite and it has not changed.

In this study, three series of electrical discharge machining experiments were carried out on γ-TiAl intermetallic. In the first series, by changing pulse current and pulse on time in EDM process and in the second series by changing the size and concentration of aluminum powder particles mixed in dielectric fluid, output characteristics including material removal rate (MRR), tool wear rate (TWR) and surface roughness (SR) are evaluated. In the third series of machining experiments, after determination of the optimum size and concentration of aluminum particles, current and pulse on time, are changed at levels as exactly the same levels in powder-free tests and MRR is evaluated. Finally, MRR of the EDM and optimum PMEDM processes, are compared. By increasing the aluminum particles concentration, TWR and SR will be decreased to an optimal level and then will be increased. For particle size of 2 μ m and 20 μ m, by increasing the aluminum powder concentration, MRR increases at first and then decreases, while for particle size of 63μ m, by increasing powder concentration, MRR decreases. The minimum and maximum increment of MRR in optimum PMEDM condition compared with EDM mode was 32% and 88%, respectively. With increase of electrical discharge energy, the addition of aluminum powder has less effect on increase of sparking frequency and consequently the MRR.

Spring back is the geometric change made to a part at the end of the forming process when the part has been released from the forces of the forming tool. Upon completion of sheet metal forming, deepdrawn, twisting and stretch-drawn parts spring back and thereby affect the dimensional accuracy of a finished part. In wave guides bending and twisting elements are used to transmit waves. In the present work, the spring back of rectangular section thin wall hollows is investigated. In order to study the torsional behavior of the specimens, a finite element model is constructed by considering a material model with strain hardening behavior. After validating numerical simulation by experiment, twisted angle versus applied torque is presented according to FE model. In conclusion, a relation based on numerical and empirical results is proposed to estimate twisted angle before and after loading and unloading. In the other words, by using the present model, applied twisted angle to achieve the desired value could be obtainable.

In the present study, Al/TiC surface composites were prepared by SMAW process using FeTi and graphite powders as reactants. Electrical arc was used in order to start the formation of TiC particles into steel melt. The reactants ratio effect on microstructure, hardness and wear behavior was examined. Dry sand/rubber wheel abrasion test machine according to ASTM G65 was used to wear tests. Results showed that maximum size and volume fraction of TiC particles was obtained by 18/82 graphite/FeTi ratio. This specimens showed maximum hardness equal to 481 BHN. Also, results showed that wear behavior dependent on size and volume fraction of the reinforcement particles. Measurements showed that, the waste volume in the coated and noncoated specimens were 25 mm3 and 289mm3, respectively. In all samples, micro-cutting of the composite matrix were seen. It was revealed that surface composites obtained with 18/82 graphite/FeTi ratio had lower wear rates and bigger wear resistant.