مجله مهندسی ساخت و تولید ایران
سال دهم شماره 3 (خرداد 1402)

Carbon fiber reinforced composites have many industrial applications due to their suitable mechanical and physical properties. Drilling is one of the common methods for creating connections between fiber-reinforced structures. Rotary ultrasonic drilling process is one of the new methods in machining fiber-reinforced composites, which has been highly regarded in recent years. Exact dimensional tolerance is one of the important issues in machining of carbon fiber reinforced composites. Therefore, in recent years, new tools such as cored diamond tools are used in drilling fiber-reinforced composites, considering force reduction and simultaneous drilling and grinding inside the hole. In this research, the dimensional accuracy in the drilling process using ultrasonic waves in carbon fibers reinforced composites has been investigated. The results indicate the effective axial force reduction in vibration drilling compared to traditional drilling. Besides, the results show that the cylindrical and roundness tolerance have been improved significantly while using ultrasonic vibrations. According to the examinations, it was observed that the tool rotational speed increasing and feed rate decreasing improve quality of the hole.

The aim of carrying out this research was to fabricate and characterize a nano–SiC scaffold with PEG in order to utilize in bone tissue engineering. For this purpose, nano–SiC powder was synthesized via ball milling method. Fabrication of scaffolds and their coating were carried out using polymeric sponge replication and dip – coating methods. Nano–SiC and scaffolds were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), energy dispersive spectroscopy (EDS), particle size distribution test (DLS), transmission electron microscopy (TEM), and Brunauer Emmet Teller (BET). In order to examine the physical and mechanical properties of the scaffolds, porosity percentage and compressive strength values were measured. Results showsd that nano–SiC powder were synthesized and characterized via ball milling method with success. Fabrication and characterization of nano–SiC–PEG scaffolds was conducted via polymeric sponge replication and dip coating methods with success. The porosity of the scaffolds was found to be around 65-80%. The compressive strength of the scaffolds was found to be around 0.72-2.32 MPa. Finally, the 30% by weight silicon carbide scaffold with polyethylene glycol coating and 30 seconds coating time was introduced as the optimal scaffold that can be used for bone tissue engineering applications (spongy bone).

Tube hydroforming is a forming process in which the hydraulic pressure is used to change the shape of material. In this research, the formability of copper-aluminum double-layered tube in the hydroforming process has been investigated by experimental and simulation methods. First, the double-layered tube with the outer layer of aluminum has been examined, which was burst due to the low plasticity of the aluminum tube. Then, a two-layered tube with the outer layer of copper has been examined, and the inner aluminum tube was wrinkled. To prevent the inner aluminum layer from wrinkling, an internal mechanical restraint made of copper has been used, and the experiment in this case has led to the formation of the double-layered tube without bursting and wrinkling. Response surface method has been used to study the effect of parameters. These parameters included axial punch displacement, first pressure, final pressure, aluminum tube thickness and the counterpunch. The objective functions were the thinning of copper layer, the thinning of aluminum layer and the height of the protrusion. The results showed that the axial displacement has the greatest effect on the height of the protrusion and the thickness of the inner aluminum layer has the greatest effect on the thinning of the layers. In order to achieve the maximum height of the protrusion and the minimum thinning for both layers, the optimal parameters have been extracted in the two cases of the presence and absence of the counterpunch, and the results were compared with the finite element simulation.

The presence of cracks in fuel vessels and pipelines against intermittent loads will cause them to grow in the damaged area and cause problems in the fuel transfer process. Using composite fibers to repair the damaged area can increase the life of the structure and part and prevent further damage during unloading and refueling. In this research, a steel tank is subjected to monotonic loading with an increase rate of 1 MPa per minute. The main material of these types of structures is API 5L X65 steel, and the repair conditions are made according to ISO24817 and ASME PCC-2 standards. Numerical analysis of these structures according to the type of defect in it and comparing it with the repaired tank can predict the optimal working conditions. Also, the presence of cracks in this type of tank due to the type of corrosion will cause a lot of stress concentration and change their shape. Using composite fibers and spacers will reduce the stress level and prevent the growth of cracks caused by corrosion. Among the advantages of repairing with the help of composite fibers are the non-interruption of fluid flow inside the pipe during the repair, easy installation, reduced costs, and improved safety. Therefore, this method reduces the stress concentration in the corrosion area.

The process of major repairs and manufacturing in diesel engine repairing and remanufacturing factories is very important. Reducing the cost of repairing and the time of the processes is depended on the amount of capacity and work speed. One of the equipment that increases the capacity and speed of work is a device called a heavy equipment rotary table. In this article, research and investigation for the construction of a heavy equipment rotary table is targeted. The importance and application of items that should be considered for the design of this product have been collected. The designing of this device has been done in CATIA and Abaqus software. The loading capacity of the device was 15 tons and the torque capacity was 15000 N.m. The influential and critical components of the device were simulated using Abacus finite element software, and the geometric dimensions of each component were precisely determined. St37 carbon steel sheets were used to make the body of the machine. The standard components and parts of the device were also selected according to the mechanical and functional characteristics of the device. Finally, the rotary table device was built according to the extracted functional models and its function was evaluated successfully.

The brittleness behavior of thermosetting composites has resulted in limitations in their wider applications.  The said composites brittleness even becomes more critical upon the addition of reinforcing materials. Moreover, the use of materials recyclable to the environment in the use of composites has been considered to address challenges regarding bio-aspects, nevertheless die to the incompatibility of natural reinforcements with the polymer phase, the addition of natural fibers leads to the decrease in absorption energy and impact resistance of composites. The present study aims at the materials and the fabrication technique of polyester micro-composites reinforced with natural kenaf fiber up to 20 wt% laminated aligned or crossed perpendicularly, which has resulted in the increase in the impact resistance of the base polymer by 2400% and the energy absorption capability by 40% improvement.  The observed enhancement is correlated to the increase in contribution of the natural fiber phase in load transfer and energy absorption aligned the fiber direction during the fabrication process and the improvement in the resin penetration within the kenaf fibers which also leads to the penetration ability of resin within the layers of high fiber ratio in this classification of composites.