Papers by Keyword: Stability

Abstract: Recently, a new meta-heuristic optimization algorithm–harmony search (HS) was developed,which imitates the behaviors of music improvisation. Although several variants and an increasing number of applications have appeared, one of its main difficulties is how to enhance diversity and prevent it trapped into local optimal. This paper develops an opposition-based learning harmony search algorithm (OLHS) for solving unconstrained optimization problems. The proposed method uses the best harmony to play pitch adjustment, and bring the concept of opposition-base learning into improvisation, which enlarged the algorithm search space. Besides, we design a new parameter setting strategy to directly tune the parameters in the search process, and balance the process of exploitation and exploration. Numerical results demonstrate that the proposed algorithm performs much better than the existing HS variants in terms of the solution quality and the stability.

Abstract: Retained austenite has an important effect on strength and toughness of 20Mn2SiCrMo bainitic rail steel. In this work, the stability of retained austenite and mechanical properties have been studied. The results show that impact toughness of experimental steel has close relationship with the stability of retained austenite. When tempered at lower than 350°C, retained austenite owns good thermal stability, corresponding to relatively high impact toughness.

Abstract: The problem of stability of the polymer rod in creeping was solved by energy method in the form of Timoshenko and Ritz. Possible displacements of the points were given in the form of a trigonometric series with undetermined coefficients. Results obtained numerically using complex Matlab under different constraint equations between creep deformations and stresses. There are shown the necessity of taking into account the "junior" component of high-elastic deformation by using the Maxwell-Gurevich equation.

Abstract: In this paper, xingshan iron mine as an engineering example. Based on slip field theory, numerical simulation method and limit equilibrium method for the mine slope stability research and evaluation. Meanwhile, a variety of load shedding scheme was designed and optimized design. The results showed that the final dump slope angle is 19.2, considering the most unfavorable conditions in saturated with earthquake. And ultimate load shedding scheme can guarantee the slope stability, and saves the load shedding costs is about 20 million yuan. The economic effect is remarkable.

Abstract: In this paper, the influences of different conditions on heat-transfer stability of porous fibrous composition were analyzed by the one-dimensional unsteady heat transfer model. It was resulted that the surface condition of composition was key parameter for heat performance during different thermal process. Great humidity and thermal difference caused the heat transfer fluctuating of material covering, and then changed the thermal conductivity. For the insulation materials under low temperature, the heat performance was sharply fluctuated nearby 0°C.

Abstract: Dynamic behaviour of spindle system influences chatter stability of machine tool considerably. Self-excited vibrations of the tool results in unstable cutting process which leads to the chatter on the work surface and it reduces the productivity. In this paper, a system of coupled spindle bearing system is employed by considering the angular contact ball bearing forces on stability of machining. Using Timoshenko beam element formulation, the spindle unit is analyzed by including the gyroscopic and centrifugal terms. Frequency response functions at the tool-tip are obtained from the dynamic spindle model. In the second phase, solid model of the system is developed and its dynamic response is obtained from three dimensional finite element analysis. The works on analysis of the stability of milling processes focus on calculating the stability boundary of the machining parameters based on the dynamic models characterizing the milling processes. The stability lobe diagrams are generated from frequency response functions (FRF’s) lead to an stability limit prediction for the system at high speed ranges.

Abstract: When the pod works in the air, pod can produce the overshoot and stability. To solve this problem, the study demonstrates that the fuzzy-PID was used to control the pod. Simulink simulation module of Matlab was using to establish a control system model pod exterior orientation framework to verify the simulation, anti-jamming performance and tracking performance of the system. The results show that fuzzy PID control method can make the system have good stability, noise immunity and tracking capability.

Abstract: In the first part of my paper, a vibration model has been put forward for studying the self-synchronization of a vibrating system by two-motor driven with isolation frame. The self-synchronization motion implementation and the stability condition of self-synchronization motion is obtained by the Routh-Hurwitz criterion. Zhao C Y ^{[ 1 ,2 ]} developed self-synchronization of the duel-motor and four-motor driven vibrating system by modified average method. S everal methods were used to analyze the self-synchronous motion verifying the self-synchronization of two motors. Wang D G used the computer to simulate the process of self-synchronization, and the results showed that the synchronization of vibrating system came true in either speed or phase to enable the system to be in a good self-synchronization state ^{[ 3 ]} . Balthazar ^{[ 4 ,5 ]} studied the self-synchronization of four motors having limited power supply and mounted on a flexible structural frame support.

Abstract: The idea of self-synchronization vibrating system comes from the phenomenon of synchronization. In the 1960s, Blekhman^[1,2] proposed the self-synchronization theory of vibrating system driven by two induction motors. When the structure parameters of the two motors met the requirements, the system could operate synchronously. Blekhman^[3] also found that even if the rotating speed and the angular phase difference of the two eccentric rotors were being disturbed or one of the motors was powered off, the system could still operate synchronously. The small parameter methods were applied to a number of problems by R.F. Nagaev^[4]. It can lead to better understanding of the self-synchronization theory. Wen Bang-chun^[5] applied self-synchronization theory to engineering and established a branch of the vibration utilization engineering, and numerous self-synchronous vibrating machines were invented.

Abstract: For the problems about design and manufacture of the variable pitch tapered end mills, this study proposes a three-dimensional parametric design method of variable pitch mill. Firstly the equation of calculating the optimal angle between the pitch was presented .Considering existing different patches between two cutting edges, helix edge curve and cross-section groove model of tapered end mill were established .Secondly, mathematical expression of ball end teeth for tapered mill was derived, and all points data of tapered mill surface can be determined by established model. Through the graphical representation, the points set are translated into a solid model.