Application of a portable indentation rig with Rockwell indenter to determine mechanical properties and residual stresses on an aluminum plate

Measuring residual stresses is still a dilemma in many engineering applications. It is even more crucial when the industrial requirements demand for a non-destructive technique in order to avoid compromising the structural integrity of the engineering components. Furthermore, estimating the mechanical properties of the materials, especially when the components are aged, is of importance. Instrumented indentation has gained much interest in recent years. There are many studies in the literature which are focused on measuring residual stresses or mechanical properties using instrumented indentation. Since in many cases there is no possibility of transferring large samples or those under service, for possible measurements, having a portable rig can be very useful. Furthermore, indentation procedure is a low-cost non-destructive method with high accuracy which is able to measure the plastic properties of material as well as its residual stresses on which the designing and construction of the portable apparatus were based. The instrumented indentation testing details were followed according to the ASTM E2546-15 standard practice. In this research, a wide range of simulations were performed on a group of aluminum alloys in order to estimate the equi-biaxial residual stresses by analyzing the indentation load–displacement curves which were obtained from the experimental outcomes. Then neural networks were employed to estimate the unknown parameters. The performance accuracy of the designed portable apparatus and the acceptable precision of the introduced method were then verified with experimental tests performed on Al 2024-T351.

Speed control of universal motor

Universal Motors (UM) are normally used for driving portable apparatus such as hand tool machines, vacuum cleaners and most domestic apparatus. The importance of UM is due to its own advantages such as high starting torque, very powerful in relation to its small size, having a variable speed; and lower cost. So, this paper focus on UM speed control under variable loading conditions. A mathematical model for UM is designed. Two controllers are proposed for controlling the motor speed, output rate controller and output reset controller. Ant Colony Optimization (ACO) is proposed for tuning the controller’s parameters due to its impact on solving different optimization problems. It possesses fast convergence, minimum algorithm parameters required, lower consecution time and give optimal results without needing large number of iterations. The results are compared and discussed accurately, which show the proposed tuning technique work well and give optimal results for both controllers.

NITRATE CONCENTRATION IN PLANT PRODUCTS OF ALBANIAN MARKET

This study presents a research done for nitrate concentration in fruits and vegetables purchased in Albanian markets and department stores.Recently media and television, investigative programs, newspapers, social networks and Association for the Albanian consumer have denounced the problem of the high nitrate content found in plant products.In this study, nitrate concentration available in vegetables and fruits, was determined and compared with standard limits.Thirty-seven fruits and vegetables were purchased in summer and autumn and tested with Green Test Eco 5 supply, a simple and portable apparatus that performs quick measurements with margin error about 10%. Photos of the checked products were made and each value was registered and calculated referring the margin error of the supply. Excel was used to draw diagrams and make statistical analysis.From the results obtained it was noticed a very high concentration of nitrate in vegetables and fruits like watermelon, melon, beetroot, marrow, cherry radish, red potato. These products tested accounted around 40% of the total quantity and were dangerous to eat.For other products it was noticed a lower nitrate content comparing with the dangerous one but again above allowed standard limit like white potatoes, eggplants, cherry radish. These products tested accounted around 20% of the total quantity and were still ok to eat.Of course, the products with nitrate levels below the permitted standard such as bananas, carrots, broccoli, apple, orange, green lettuce, cucumber, kiwi, pineapple, persimmon, onion, cauliflower were also found in the analyzed products. So about 40% of total quantity were safe to eat.The conclusions extracted from this study are such as to highlight the risk to the Albanian consumers and the lack of control of the responsible institutions.