JOURNAL OF MECHANICAL RESEARCH AND APPLICATION (JMRA)
Year:2012 | Volume:4 | Issue:1|Papers Count:7

The spot welding is widely used for joining thin sheets in different industries; such as automotive industry. This method of welding is very easy to automate and maintain. In this study, the effect of nugget diameter on the tensile-shear strength of the spot welding joints was investigated. The specimens were manufactured from AISI 1008 HR sheets with 1.0 mm thickness. The eight different electrodes with different active face diameters (3–10 mm) were employed. Tensile tests of the prepared specimens indicated that both ultimate tensile strength (UTS) and yield strength increased to a certain level and then remained constant. The comparison between specimen failure modes showed that in specimens with lower nugget diameter, tearing occurred in nugget. However with increasing the diameter, failure location moved to nugget edge with tearing in base sheet. Interestingly, the specimens with change in failure location were those that UTS and yield strength were remained almost constant. This was also the case where the elongations of these specimens were studied.

In this research, the incremental slitting method was employed to determine through thickness residual stress profile of a carbon/epoxy laminate. The method involves measuring strains at the back surface of the stressed specimen, while a narrow slit is cut by a CNC milling machine progressively from the top surface of the specimen. "Pulse Method" was selected as the computational approach for the determination of residual stresses from measured strains.Results show that thermal residual stresses resulting from curing process of laminated composites have high values and may play a significant role in the failure of these components.

This paper aims at studying a trigeneration system, based on an internal combustion engine and a steam ejector refrigeration system. The designed cycle is to generate cooling and heating energies, and supply power simultaneously. The cycle is studied from thermodynamics point of view and for this purpose, the first law of thermodynamics is applied to all the components of the cycle. The efficiency of the cycle is studied by changing a number of parameters such as the pinch point temperature, evaporator temperature, heat generator temperature, and condenser temperature to simulate summer and winter seasons. The results show an increase in the fuel efficiency up to 88% for the winter and 71% for the summer, and also a 28% fuel savings for the winter and 18% for the summer seasons.

Residual Stress Measurement has gained interests among researchers for many years due to its great influence on the structural integrity. Slitting Method is one of the destructive techniques that relies on the introduction of an increasing cut to a part containing residual stresses. Similar to all other mechanical strain relief techniques, slitting also suffers from its shortcomings during the measurement procedure. In the present research, slitting method was simulated using finite element analysis. Furthermore, the experimental procedure of the slitting method was carried out. The quenching was employed to induce residual stresses within a sample made of 316L steel. A strain gauge was attached in the correct location and the residual stresses were measured using the compliance coefficients. The experimentally measured stresses were then compared with those predicted using finite element analysis. A very good correlation was observed.

The main objective in this paper is to create a method for one-dimensional modeling of multi-stage axial flow turbine. The calculation used in this technique is based on common thermodynamics and aerodynamics principles in a main stream line analysis. In this approach, loss models have to be used to determine the entropy increase across each section in the turbine stage. Finally, the analysis and comparisons between the calculated results and experimental data are performed.

The effect of a distributed patch mass on the natural frequency of vibration of a laminated rectangular plate with simply supported boundaries is investigated. The third order displacement field of a composite laminated rectangular plate is defined using the two- variable refined plate theory. Equations of motion of the plate are obtained with the help of the calculus of variation. Parametric study of non-dimensional natural frequencies of vibration is carried out and the effects of geometrical parameters such as the aspect ratio of the plate, size and location of the patch mass on these frequencies are studied. The results are then compared with those reported using the third order shear deformation theory. The findings are found to be in a very good agreement.

In this study, the vibration of cracked plates is investigated using differential quadrature method and experimental modal analysis. The crack, which is assumed to be open, is modeled by the extended rotational spring. With its finite length, the crack divides the plate into six segments.Then, the differential quadrature is applied to the governing differential equations of motion and the corresponding boundary and continuity conditions. An eigenvalue analysis is performed on the resulting system of algebraic equations to obtain the natural frequencies of the cracked plate. To ensure the integrity and robustness of the presented method, experimental modal analysis is carried out on cantilever plates having open cracks with finite length and the results are compared with the proposed method. A numerical study is performed to show the effect of length, depth and location of the crack on natural frequencies of the plates. The results verify the accuracy and efficiency of differential quadrature method.