Bu-Ali Sina University

About: Bu-Ali Sina University is a education organization based out in Hamadan, Hamadān, Iran. It is known for research contribution in the topics: Catalysis & Adsorption. The organization has 4078 authors who have published 7969 publications receiving 122828 citations.

Sequencing the mixed-model assembly line to minimize the total utility and idle costs with variable launching interval

Abstract: A mixed-model assembly line (MMAL) is a type of a production line where a variety of products is assembled on it. A mixed-model assembly line problem involves not only solving the traditional problems of the assembly line design (i.e., determining the cycle time, the number and sequence of stations, and the balancing problem) but also determining the sequence of products in assembly line. The product sequencing has a high effect on the mixed-model assembly line efficiency. In this paper, we consider sequencing problem with a variable launching interval between products on the assembly line. A mathematical model is presented, which is capable to solve the small-sized ones of these problems. The considered problem involves two optimization problems (the sequencing problem and launching interval problem). Since this problem is strongly NP-hard, a hybrid metaheuristic algorithm based on the simulated annealing approach and a heuristic approach is developed. The heuristic approach (launching interval between products algorithm) is presented to solve the launching interval problem for each sequence. Numerical experiments are used to evaluate the performance and effectiveness of the proposed algorithm. Variable launching interval consideration in MMAL problem causes the higher complexity of this problem. However, this assumption improves the considered goals for this problem. Not only a power algorithm for MMAL is presented in this paper but also the effect of this assumption is discussed. Numerical experiments are used to evaluate the performance and effectiveness of the proposed algorithm.

Strengthening mechanisms of nano-grained commercial pure titanium processed by accumulative roll bonding

Abstract: Grain-refining process in commercial pure titanium was performed by room-temperature accumulative roll bonding. The study on the microstructural evaluations showed a reduction in grain size from about 45 µm in the untreated (annealed) sample to about 90 nm after six cycles of accumulative roll bonding, a reduction factor of about 500 times. The yield strength of the nano-grained commercially pure titanium after the sixth cycle, 799 MPa, was about three times higher than that of the as-received sample, 284 MPa. Different strengthening mechanisms during the accumulative roll bonding processing of the commercially pure Ti were assessed, and the contribution of each mechanism to the yield strength improvement was quantitatively calculated. The results showed that the calculated yield strength (834 MPa) for a six-cycle processed sample is close to the measured value (799 MPa).