مجله مهندسی ساخت و تولید ایران
سال نهم شماره 10 (دی 1401)

Fault diagnosis of rotary machines plays an essential role in reliability and safety of new industrial systems. Gears are considered as a vital part of the components of industrial machines, so that the defects of these components cause irreparable damages in industrial processes. Nowadays, many research workers conduct studies on the diagnosis of gear faults using data analysis. In this research, to acquire acoustic data from a sample gearbox, a system was fabricated and developed. Then, some common faults in the gearbox teeth were created artificially. In this research, cepstrum analysis method was used in order to detect the harmonics of gear mesh frequency and the family of sidebands created. In the primary investigation, the harmonics related to the gearbox shaft were identified with the cepstrum analysis method in the interval of 0 to 0.25 seconds. Then, in order to detect the faults of the gear, by analyzing in the interval of 0 to 0.0002 seconds, the faults related to the tooth were clearly visible and tracked. According to this research results by observing increase in amplitude of the first and fifth rahmonics, it is possible to detect faults such as broken and worn teeth of gears. The obtained results show the effectiveness of the presented method to diagnose the fault in the gearbox and prevent unexpected costs.

Achieving the minimum thinning and required forming force is one of the main purposes in the manufacturing of sheet products using the hydroforming process. This paper investigates forming of the copper sheet using the hydrodynamic deep drawing assisted by radial pressure via the design of experiment method and finite element (FE) analysis. Firstly, the necessary experiments have been designed using the Taguchi design of experiment method. In this design, maximum fluid pressure, punch velocity, the friction coefficient between punch and sheet, the friction coefficient between die and sheet, the gap between blankholder and die, punch nose radius, die entrance radius, and prebulge pressure were considered as input variables and thinning ratio and punch force considered as response functions. Then, designed experiments were performed using an experimental verified FE model and the desired results were obtained. Finally, the optimum levels of input variables were obtained using the Taguchi optimization method and the confirmation experiments were performed using the FE simulation. Results show that the punch nose radius and die entrance radius are the essential parameters on the thinning ratio. Also, the maximum fluid pressure is the most effective parameter on the punch force.

Nowadays, the use of new technologies in the cleaning of parts has attracted the attention of various industries due to the problems of traditional cleaning methods such as low cleaning quality, lack of repeatability, low safety, equipment corrosion, low speed and environmental problems. Using the process of cleaning with ultrasonic waves is one of the new methods of cleaning parts in a safe, fast, high-quality and environmentally friendly way. Therefore, it is necessary to optimize and develop this cleaning process by researchers. The purpose of this research is to design, model and introduce a new optimal and continuous ultrasonic cleaning tank to improve the quality of cleaning using ultrasonic waves. In this research, the simulation has been done using finite element method (FEM) and by performing static, modal, harmonic analysis and computational fluid dynamic transient analysis in ANSYS 15 software. In this article, after obtaining the natural frequencies and the shape of the vibration modes, the amount of displacement of different points is determined by applying harmonic stimulation. Then, by applying this displacement to the fluid, the pressure field created in the fluid inside the simulation tank and the effective range of cleaning have been determined by comparing the created acoustic pressure. The modeled ultrasonic cleaning tank with 9 ultrasonic transducers with a resonant frequency of 26.5 kHz and a power of 100 watts with a spiral arrangement was manufactured and tested. The obtained results show the proper performance of the designed and manufactured ultrasonic cleaning tank. Also, the obtained results show that the simulation with the finite element method is reliable and a suitable method for designing and optimizing ultrasonic cleaning tanks.

In recent years, the hydroforming process for manufacturing complex parts such as combustion chamber and gas turbine nozzle baffle, in which the forming process of materials, especially super alloy sheets, has a key role, has attracted the attention of power plant industries. Also, this process is used as a supplementary and sizing process at the end of the manufacturing process to increase the dimensional accuracy of the assembled component. In this research, the hydroforming process of AISI304 stainless steel tube for manufacturing of gas turbine nozzle baffle has been investigated. Before conducting the experimental tests and for a more accurate evaluation, the hydroforming process of the pipe was simulated in three stages: pre-forming the pipe, heat treatment of the pre-formed pipe and finally performing the hydroforming process in the final form, and in this regard, a numerical model was created. Finite element simulation was developed in Abaqus commercial code environment. In the following, the simulation results were compared with the laboratory results and a good agreement was observed between them. Also, the best form change mode to achieve the final form of the baffle is hydroforming the annealed preform tube at 100 bar oil pressure.

In this article, the friction stir process (FSP) was used to add various weight percentages of silicon carbide (SiC) nanoparticles to the base phase of PA6/NBR. Also, the effect of three variables of the rotation speed tool (ω), traverse speed (V) and the weight percentage of silicon carbide nanoparticle (S) on the mechanical properties (young’s modulus and impact strength) were investigated by response surface methodology (RSM) based on the Box-Behnken design. Scanning electron microscope (SEM) was used to determine the dispersion of nanoparticles in the base phase and the effect of their addition on the microstructure of PA6/NBR thermoplastic elastomer. Moreover, the thermal properties of PA6/NBR/SiC samples with different weight percentages of silicon carbide nanoparticles were investigated by differential scanning calorimetry (DSC) and thermo gravimetric analysis (TGA). The values obtained from the regression equations showed that, under optimal conditions of the rotational speed of 1200 rpm, traverse speed of 20 mm/min and the weight percentage of nanoparticles of 3.8 wt. %, the maximum young's modulus and impact strength 665.18 MPa and 62.26 J/m, respectively could be obtained. Also the crystallization and melting temperature increased to 198 and 222.8 °C, respectively.

Covalent organic frameworks (COFs) are a category of organic polymers with crystalline structure having vast potential for electrochemical energy storage due to great porosity and specific area, as well as strong resonance. The simultaneous polymerization and crystallization of two reactive monomers featuring directional bonding designs provides COFs. The purpose of the current research was to produce high-performance COFs based on condensation reaction between diamine and trialdehyde monomers in liquid state. The synthesized COFs were characterized in terms of structure and properties through Fourier Transform Infrared (FTIR) spectroscopy, BET analysis, X-ray diffraction (XRD), Thermogravimetric analysis (TGA), and electrochemical performance. FTIR confirmed the successful chemical reaction between precursor monomers leading to covalent bond formation. XRD confirmed the formation of crystalline structure having typical lattice of a COF. BET analysis showed that the synthesized COF is porous, whose average pore diameter is around 28 nm, pore volume per gram is 0.19 cm3, and specific area is 465 m2/g. Thermal stability of the synthesized COF was found through TGA to be 316 °C. cyclic voltammetry, galvanostatic charge/discharge, and electrochemical impedance spectroscopy tests revealed that the electrodes made from the synthesized COFs possess satisfactory cycle performance and high-level specific capacitance (302 F/g) at current density of 1 A/g.