IRANIAN JOURNAL OF MANUFACTURING ENGINEERING
Year:2018 | Volume:5 | Issue:2 |Papers Count:6

In this study, high-temperature tensile behavior of Al-3 vol% SiC nanocomposite is investigated. To fabricate the samples, SiC nano reinforcements and Al matrix were mixed using an attrition milling. The mixed powders were then subjected to cold pressing and hot extrusion at temperature of 500° C. Tensile behavior at different temperatures along with density measurement and microstructural examinations were studied. The results represent a 40% improvement in ultimate tensile strength of Al-3vol% SiC nanocomposite in comparison with non-reinforced sample at ambient temperature. Also, a rise in temperature up to 270 ° C during the tensile test led to an increase of the maximum elongation. Moreover, this temperature rise caused to 50% and 44% reduction of ultimate tensile strength of non-reinforced and nanocomposites samples, respectively. Fractured surfaces also showed that the in non-reinforced sample with increasing the temperature, brittle fracture changes to ductile fracture however, for nanocomposite sample the fracture remains brittle.

The use of composites in the aerospace industries is widespread due to their unique properties, as in some planes, more than half the weight of the aircraft is composed of composite materials. Drilling is one of the most widely used machining operations to assemble composite parts and connect them to each other. Delamination and hole diameter errors are the most important defects that occur during drilling of fiber-reinforced composites which reduce the efficiency of composite structures. The purpose of this research is to investigate the effect of twist drill point angle and size of chisel edge on delamination and diameter error of the hole in drilling of a thin sheet of Kevlar/epoxy composite with a supporter plate. The experiments were designed and implemented with full factorial design and in 3 levels for feed rate and 3 levels for cutting speed. The obtained results showed that the lowest mean diameter error of the hole is obtained in drilling with a 135-degree point angle drill with chisel edge and the lowest mean delamination factor in drilling is obtained with a 135-degree point angle drill without the chisel edge.

Engineers inspired of self-healing operation in biological system and take advantage of this innovation for repairing different materials such as composites. In the present study, reparation of micro-cracks and damages in a epoxy-glass fibers composite using self-healing methods in investigated. So one series of hollow glass micro-tubes were used to fabricate a self-healing mechanism. These micro-tubes were filled by one self-healing agent which is one two-part resin. The purpose of the present study is to investigate the effect of heating cycles over the time is restored in this composites. So consecutive temperature cycles (1, 3 and 5 cycles) were implemented in the temperature range of 25-70 ° C after the damage made in the sample. The results of tension tests showed that a 86% healing efficiency which gained after 7 days can be gained only in 1 day with almost 5 cycles of heat in the mentioned temperature range.

Ultrasonic welding is an economic and advanced method for connecting such parts like plastic, fabrics, metals and dissimilar materials, especially for mass and high quality production assembly parts. The most important and distinguished property of this method to other fabrics and plastic sewing methods is the minimum destruction of materials and fibers because the maximum produced heat occurs in the contact interface. Horn is one of the basic parts of the ultrasonic welding which in addition on the transmitting waves and appropriate energy concentration, provides the necessary pressure to keep the melted joint interfaces together in order to form a weld. That’ s why horn characteristics in terms of geometry and dimensions have a significant impact on the quality of welding. The purpose of this paper is to study the design of a roller type tool by numerical method using finite element method. In this research, the design and modeling of continuous welding roller tools was performed using numerical finite element method by ABAQUS 6. 12 software. By simulating and analyzing include natural frequency and harmonic analysis, the frequency, mode shape and other design parameters and behavior of the collection during applying oscillations for 4 types of horns include conical integrated, stepped with grooves integrated, stepped without grooves integrated and bell-like horn were derived. The result of the different horns shows that the stepped without groove horn has the highest gain, but the radial displacement distribution in the conical integrated and stepped with groove horns is more non-uniform than other horns. Also, in the stepped without groove and bell-like horn, the efficiency of the conversion of longitudinal to radial displacement and the uniform distribution of radial displacement is more uniform, which results in better optimal design conditions.

In this research, the microstructure, phase-analysis, hardness and wear behavior of cladded carbon steel of St-52 by a high chromium-carbon electrode with or without using 309-stainless steel as a middle layer are investigated. Cladding process is performed by shield-metal arc welding (SMAW) and gastungsten arc welding (GTAW) methods. In order to evaluate of microstructure, the optical and scanning electron microscopies along with EDS analyses are used. In addition, hardness measurement and wear behavior are conducted by micro-Vickers hardness and dry-sliding wear test, respectively. The research findings show that the microstructure of cladded samples are consisted of M7C3 carbides into the eutectoid matrix of Ɣ + M7C3. Additionally, the volume fraction of carbides are increased at the cladded sample with middle layer of 309-stainless steel as opposed to other samples. Increasing of carbides percentage at the cladded samples with middle layer are caused to enhanced of hardness and wear resistance with comparing to other samples. In this case, the surface hardness and weight loss of wear test are achieved from 780HV and 3. 7mg to 945HV and 2mg at the cladded sample without and with middle layer of 309-stainless steel, respectively. Moreover, examining the wear surfaces indicated the occurrence of an adhesive wear mechanism in the specimens. Also, by increasing the hardness in middle layer sample the amount of adhesive wear decreased.

The magnetic flux leakage technique (MFL) is a widely used method for corrosion detection in the gas pipelines. The inspection of pipelines is typically performed using intelligent PIGs. The MFL intelligent PIG is equipped with an array of magnetizers responsible for inducing a magnetic field in the pipeline wall. The magnetic field leaks out of the pipeline wall at the locations where defects are present. The magnitude of the leakage magnetic field is measured by Hall-effect sensors and used for analysis of defects. In recent studies, the design of the appropriate magnetizer, as a technique to improve the probability of detection of the MFL, has been of great interest to the researchers. In this study, the simulation of the MFL technique was carried out based on Maxwell equations and in 3D using COMSOL software. The specimen under test was a carbon steel plate with a thickness of 10mm, which contained two pitting defects with various depths of 4mm and 6mm. Then, the MFL signals obtained from the defects were analyzed. Following the finite element modeling and obtaining the magnetizer dimensions, MFL system was designed and manufactured. First, the FEM results were experimentally validated. The results of the comparison indicated that there was a good agreement between experiments and FEM. The mean error was below 9%. Finally, MFL experiments were carried out and C-scans from the defects of different depths were obtained. The C-scans can be used for characterization of the defects.