kaveh abbasi

Fit joints are widely used in industry to connect bush to shaft and its manufacturing process is always associated with geometric deviations similar to other processes. In a cylindrical fit connection, the geometrical deviation of the shaft and the bush is in order of one hundredth of millimeter, which is a common precision in manufacturing. This range of error seems to be significant compared to the required dimensional interference to make the connections and affects the strength of the interference fit joints. Usually, certain geometrical deviations will occur in the production process considering the selected manufacturing method. This research attempted to investigate the effect of common geometric deviations at the surface of interference of cylindrical interference fit on the experimental extraction strength. In this regard, 8 specimens of interference fit with same characteristic of dimensions, surface roughness and interference were produced. Furthermore, shafts with certain geometrical deviation (standard sample, two-lobes, three-lobes and conical) were made and fitted. Then, the extraction force of each part was extracted experimentally. Taking into consideration precise measurements of the parts dimension, the effect of shaft geometrical deviations on the strength of the joint was investigated. The results showed that the geometrical deviation affects the extraction strength. However, in the quality control process of these parts, by measuring the dimensions of the parts, the effects of these usual geometrical deviations on the joint strength could be predicted and the quality control process can be performed more effectively.

Interference fit joints are widely used in the industry to produce tight joints. These type of connections have produced more beautiful and smaller joints by eliminating other joints such as keys which are defected with stress concentration. Interference fit joints could be applied under dynamics and statics design loads, successfully. Interference fit joints are always imperfect, such as other industrial products and also affected by some parameters which directly affect the operation of these joints. For instance, contact surface of every manufactured joint parts are not a perfect cylinder and always there are some form defects. The variation of these parameters could affect the performance and strength of interference joints, so these parameters should be considered. Some effective parameters on the strength of interference fit joints are friction coefficient, roughness, materials properties, dimensions and geometric irregularities of contact surfaces. In this study the effect of diameter of shaft and interference value variation on the friction coefficient in contact surface and strength of joints are investigated. Finite element results are interacted with experimental ones to estimate friction coefficients. Also, factorial method, which is a statistical method for design of experiments, are used to analysis the effects of pressure, which is vary by variation of interference, and radius of contact surface curvature on friction coefficient and strength of joints. Results indicate that the friction coefficient changes with diameter of interference surface, inversely and increase of interference and consequently, pressure leads to growth of friction coefficient.

The precise finite element model is an efficient tool for vibrational analysis. It should be mentioned that, in structural dynamic analysis finite element models of system should be able to accurately predict system characteristics such as natural frequencies. Contrary to static analysis, in structural dynamic analysis, it is not possible to overestimate system characteristics or apply safety factor for predicted characteristics; that means that the exact values of system characteristics such as natural frequencies, should be derived in structural dynamic. According to this, constructing a reliable model in the structure dynamic always has great degree of importance in vibrational analysis. In this study, it has been tried to extract a reliable finite element model for a row of a sample turbine of RollsRoyce brand using empirical results. So, the material properties of the disk and the connection between the disk and the blade are corrected and updated using experimental modal analysis results. Also, it has been tried to propose new method to model and update the disk and blade joint. Finally, reliable finite element model could be used for more analysis such as derivation of Campbell diagrams of system.

Composite nanofibers composed of an organic polymer and inorganic nanomaterials have huge potential to be used in different industrial applications. However, the main concern on the use of composite nanofibers is the distribution properties of nanomaterials in the polymeric matrix. The effect of the capillary tip charge on the additive distribution in the electrospun nanofiber has been previously studied and can be found in the literature. In this study, focus is placed on the investigation of TiO2 nanoparticles (TiO2 NPs) distribution in the polysulfone (PSF) nanofiber. X-ray Photoelectron Spectroscopy (XPS) was conducted to measure the percentage of TiO2 on the surface of the prepared PSF/TiO2 composite nanofiber. The results showed that there was no TiO2 NPs on the surface of the nanofiber for up to 10 nm in depth. TiO2 nanoparticles were mainly found in the center of the nanofiber due to the accumulation of the hydrophobic PSF at the surface of the composite nanofiber. The findings of this work can provide better interpretation of the impact of the interfacial tension on the distribution of the inorganic nanomaterials in the electrospun nanofiber.

There are two major trends in literary criticism, one is formalism (theorized by Viktor Shklovsky in his epistle Resurrection of the Word in Russia) and structuralism (emanating from the Swiss linguist, Ferdinand de Saussure’s theory that differentiated between language and speech). The researcher attempts to review Ivan-e Mada’en, one the most significant odes of Khaqani from the point of view of terms and expressions such as form, text, defamiliarization, and particularly literature debated by formalistic, structural criticism.