To improve the machining efficiency and reduce the overall manufacturing cost, a new model of machining hypoid gears by tilt cutting method is setup. Unlike the traditional cradle-style mechanical machines, the new model has no cradle and eccentric drum, the tool swivel drum is controlled by NC system. Firstly, according to its special structure, the mathematical model of the machine tool is built, an algorithm is developed to calculate the motional parameters. After building the machine tool model by the software Vericut, cutting simulation is performed. Based on the comparison of gouge and excess amount between simulated model and theoretical model, the tooth cutting experiment is conducted. Then, measurement and rolling detection for the hypoid gears is performed. The results indicate the rationality, reliability and accuracy of newly designed model of the milling machine. Moreover, the proposed method of calculating the motional parameters is feasible, which would be meaningful for future industrial application.
The mechanism of failure of heat exchanger and steam generator tube-to-tubesheet joints is related to the level of residual stresses produced in the tube expansion and transition zones during the expansion process and their variation during operation. The accurate prediction of these stresses based on the plastic and creep properties of the joint materials involved can help to design for better leak tightness and strength. Existing design calculations are based on an elastic perfectly plastic behavior of the expansion joint materials and do not account for creep. The proposed model is based on a linear strain hardening material behavior and considers the joint contact pressure relaxation with time. The interaction of the tube and the tubesheet is simulated during the process of the application of the expansion pressure and operation. The effects of the gap, material strain hardening and creep properties are to be emphasized. The developed model results are validated and confronted against the more accurate numerical FEA models.
In this paper, a delivery workload balancing problem in an assembly plant is considered. The problem is first described as a special case of the unrelated parallel machine scheduling problem of minimizing the makespan. Then, a polynomial time heuristic algorithm is proposed, which is regarded as a dynamic programming procedure to compute a linear partition of a specified list of given jobs. In addition, a simple improvement procedure based on local search technique is discussed. Numerical results indicate that from the viewpoints of solution quality and execution time both, the proposed heuristic is applicable in the practical situation.
This study investigates the robust topology optimization of a thin plate structure under a concentrated load with load position uncertainty. The effect of uncertain load direction, load magnitude, and load distribution in topology optimization problems has been investigated in previous research, but few studies have dealt with robust topology optimization considering load position uncertainty. In this study, load position uncertainty is modeled using the convex hull model, in which the load position uncertainty is confined within a circular area whose center is at the nominal load position. The worst load condition is defined as that when the applied load is at a position in the convex hull that gives the worst value of the mean compliance. Here, the robust objective function is formulated as a weighted sum of the mean compliance obtained from the mean load condition and the worst compliance obtained from the worst load condition, with a plate model based on Reissner-Mindlin plate theory. The robust topology optimization problem is formulated using a level set-based topology optimization method. Through numerical examples, robust optimum configurations are compared with deterministic optimum configurations and the validity of the proposed robust design method is then discussed.