International Journal of Advanced Design and Manufacturing Technology
Volume:11 Issue: 2, Jun 2018

Given the application of gears in various industries including steel industries, studying the reasons for facture in gears before reaching the end of their lifetime is of great importance. In this study, a gearbox was investigated which included a gear and a pinion. After four years of use, the teeth of gear and pinion along with the shaft attached to the gear were fractured. The fracture had occurred suddenly and with a lot of noise. The fracture in gear and pinion were in the teeth while the fracture in shaft occurred in the keyway. At the beginning of the study, shaft and gear design equations were used to evaluate the suitability of each of the parts in the system using theoretical equations and then fracture type was determined using fracture studies and the accuracy of analytical results were determined. In the analytical study, the results showed that the fracture is due to improper design for the gear shaft leading to more than one million unites of load on the shaft leading to cracks in the keyway and misalignment between gears causing fracture. In the fracture studies, the fracture type (ductile and brittle) was determined and the accuracy of analytical results was confirmed. In the numerical results, the distribution of static strain in the fractured shaft and a redesigned shaft are investigated.

Among assembling methods, welding is most widely used in various industries. During the welding operation, material is heated to a temperature above the melting point and melted material forms a weld pool. This leads to the formation of tensile residual stresses in the weld toe. In this paper, effect of burr grinding technique on fatigue strength of butt-welded joint has been evaluated. Burr grinding is one of the weld geometry modification methods that with removing small crack-like defects at the weld toe and increasing weld toe radius leads to reduction of stress concentration factor (SCF) and improvement of fatigue strength of weld. Also, the finite element simulation was performed by using ABAQUS software and stress concentration factor was chosen as a criterion. This factor was calculated using analytical and numerical methods for samples before and after grinding. Burr grinding procedure on welded samples was done using an electric grinder and different conical burrs. Burrs with different radii have been selected in order to provide a better comparison. Fatigue life of samples before and after grinding was determined by fatigue tests under constant amplitude loading. The results show 43.72 percent improvement in stress concentration factor and 50.61 percent improvement in fatigue life of samples. In experimental study, the best result belongs to grinding with a 3 mm tapered burr leading to an improvement of 50.61% in fatigue life while grinding with 1 mm tapered gives the worst result of 8.88% improvement in fatigue life

The most common extrusion based technology in rapid prototyping is Fused Deposition Modeling (FDM). In FDM process, widely used materials are Acrylonitrile Butadiene Styrene (ABS) and Polycarbonate. In this study ABS-P430 material is considered. During the part build process, the rapid heating and cooling is happening on the build part which leads to high thermal gradient. This thermal gradient causes thermal stress; it will lead to deformation of build parts. In this paper a three dimensional transient thermo-mechanical Finite Element Analysis (FEA) had been used to find out the maximum principal stress and deformation of the build part. This FEA analysis is called as thermal and structural deformation model or 3D FEA model. In this model, the novel technique called Element birth/death is used in ANSYS11 to mimic the FDM process. The most influencing parameters of FDM process called orientation and layer thickness have been considered in a 3D FEA model to calculate the deformation of a part. To validate the work, a standard design which is considered in 3D FEA model is fabricated using dimension 1200es FDM machine using same orientation and layer thickness and deformation is measured. From the results it was observed that the relative error between 3D FEA model and actual fabricated model is found to be 3-6%. This 3D FEA model would be helpful for RP machine users to find the deformation of the build part before making the products.

In the present study, investigation of mechanical behaviour of the fuel cladding material for a nuclear superheat Boiling Water Reactor with annular fuel rods, is carried out. In this design, each annular fuel element is cooled internally by steam and externally by water. For the fuel cladding material, radiation embitterment and irradiation-assisted stress corrosion cracking (IASCC) are the most important issues that have to be taken into account. Hence, for cladding, two materials are considered. Preliminary thermal expansion and stress analysis have been done for a fresh (begin of cycle) ASBWR (Annular-fuelled Superheat Boiling Water Reactor) fuel element. The purpose of these analysis is to investigate the stress distribution and thermal expansion of the cladding in the initial phase of operation. The results show that there is a noticeable difference in the axial expansion between the inner and outer claddings. For T91 (modified 9Cr-1Mo steel) cladding, the maximum axial thermal growth of the inner cladding is 22.12 mm, which is about 9.7 mm more than the outer cladding. For Inconel 718 cladding, the results are 27.8 mm and 13.4 mm, respectively.

Parallel kinematic machines, are closed loop structures which have more accuracy, stiffness and ability to withstand high loads. In this paper the vibration equations of the new parallel mechanism, that has higher stiffness because of parallelogram system and fixed length pods, have been derived by analytical approach. Whereas the proposed mechanism is applied as a machine tools, its vibrational behavior investigation has key impact factor. All the kinematic chains of the mechanism have been taken into consideration to achieve the coupled system of equations. To extract mechanism natural frequencies, modal analysis is carried out using three methods including analytical, finite element (FEM) and experimental method on parallel mechanism which has four degrees of freedom including three linear motion along the x, y and z axes and a rotary motion about x axis. Finally the natural frequencies and mode shapes obtained from analytical, experimental and FEM were compared. It is worth noting that all the frequencies obtained from three methods had little differences.

In the present research, similar and dissimilar resistance spot welding (RSW) process of St12 and galvanized steel sheets with thickness of 0.9 mm was investigated. The experiments were carried out based on the statistical design of experiments (DOE) approach to investigate the effect of RSW parameters on the welding quality, achieving the mathematical regression equations and predicting the new results. Welding time and electrode force were considered as the input process variables while the tensile-shear strength of the joints was considered as the process response. By comparing three RSW types, galvanized steel has the highest tensile-shear strength. Statistical analysis shows that tensile-shear strength is increased with increasing electrode force and welding time. Good agreement between the verification tests and the optimization results revealed that the statistical modelling would be appropriate for RSW process. Welding time (T) = 5 s and electrode force (P) = 925 N, welding time (T) = 5 s and electrode force (P) = 1100 N and welding time (T) = 3 s and electrode force (P) = 925 N were obtained as the optimum settings for similar RSW of St12, dissimilar RSW of St12 to galvanized steel and similar RSW of galvanized steel, respectively

The manufacturing of metal bellows with high ratios of crown-to-root diameters is very sensitive to design parameters such as internal pressure inside the tube, axial force and movement, die-stroke length (distance of the dies) as well as the initial tube length. In this paper, hydroforming process of a metallic bellows is investigated experimentally. For this purpose, the effects of internal pressure and die stroke on the maximum achievable convolution height and thickness distribution of hydroformed bellows is studied. The experiments are performed with different internal pressures such as 90, 110 and 130 bars and also in different die strokes such as 10, 12 and 14 mm. The results show that by increasing the die stroke, the range of allowable internal pressure to produce a metallic bellows without wrinkling or bursting decreases and manufacturing of the bellows becomes more difficult. It is extracted from results that with holding the die stroke value, very low internal pressures lead to wrinkling in the hydroformed bellows while very high internal pressures cause the excessive thinning. Also, it is concluded that by increasing both internal pressure and die stroke, the convolution height of manufactured bellows is increased. It is proved that the maximum thickness reduction is occurred at the crown point of hydroformed bellows