Advanced Materials Research Vols. 118-120

Abstract: Flexible job shop scheduling problem (FJSP) is an important extension of the classical job shop scheduling problem, where the same operation could be processed on more than one machine. It is quite difficult to achieve optimal or near-optimal solutions with single traditional optimization approach because the multi objective FJSP has the high computational complexity. An novel hybrid algorithm combined variable neighborhood search algorithm with genetic algorithm is proposed to solve the multi objective FJSP in this paper. An external memory is adopted to save and update the non-dominated solutions during the optimization process. To evaluate the performance of the proposed hybrid algorithm, benchmark problems are solved. Computational results show that the proposed algorithm is efficient and effective approach for the multi objective FJSP.

Abstract: Factors affecting the shape of failure rate curve are analyzed, and four elements including load, strength, degradation and lifetime index (namely, the number of load application and time) are proposed for calculating the failure rate of components. Taking the number of load application and time as the life index, respectively, the failure rate models of components consisting of four elements is developed, which can embody the effect of parameters of load, strength, degradation and life. Then, the rules that the reliability and failure rate changes as life index are studied. The result shows that the failure rate curves are partially or whole bathtub-shaped. For different parameters of load, strength and strength degradation, the curves of reliability and failure rate of components changing with time present different shapes. The models derived in this paper can calculate the failure rate of components as long as the parameters of load, strength and degradation and life index are known.

Abstract: In this paper we address a rectangular packing problem (RPP), which is one of the most difficult NP-complete problems. Borrowing from the respective advantages of the two algorithms, a hybrid of genetic algorithm (GA) and simulated annealing (SA) is developed to solve the RPP. Firstly, we adopt and improve Burke’s best-fit (BF) placement strategy, which is not restricted to the first shape but may search the list for better candidate shapes for placement. Secondly, we propose a new crossover operator, named Improved Precedence Operation Crossover (IPOX), which can preserve the valuable characteristics of the previous generation. At last, using a new temperature and iterations strategy and Boltzmann-type operator, we propose SA to re-intensify search from the promising solutions. The computational results validate the quality and the effectiveness of hybrid algorithm.

Abstract: Surrogate model produced by using multivariate adaptive regression spline (MARS) approach takes the form of an expansion in a set of basis functions which are selected from data. This approach is especially useful in the case of having no advance understanding of the parametric model. As for MARS procedure, the adaptive adjustment is used frequently to best fit the data optimally. In this paper, the adaptive adjustment is realized by using Matlab programming language and provides support for MARS procedure. Taking crashworthiness improvement for example, the program is applied to produce surrogate model for peak acceleration, and then the optimization is carried out based on this model. The results indicate that the surrogate model constructed by MARS approach can predict peak acceleration precisely and therefore can provide instruct for crashworthiness improvement.

Abstract: On the basis of the powerflow theory and four-end parameter analysis method, the responses and the powerflow characteristics of the vibration transfer path system are examined. The sensitivity of non-linear damping is employed as measurement criterion. The powerflow and powerflow sensitivity are obtained and the effect on powerflow and powerflow sensitivity of dry friction damping, fluid damping and structural damping is studied. Numerical results are also presented and discussed. It is supposed to study the sensitivity of these parameters, to estimate the effect of the change of parameters, to improve the design performance.

Abstract: A Low-pressure cylinder rotor of certain large centrifugal compressor units was studied by combing orthogonal experiments and finite element method. The effect of bearing parameters (length-diameter ratio, clearance ratio, dynamic viscosity of lubricating oil and preload) to bearing-rotor system stability and journal vibration was evaluated and optimum bearing parameters were determined. The significant and non-significant factors influencing on system stability and journal vibration were determined by variance analysis and F test. These conclusions will provide guidance to compressor rotor system design.

Abstract: This paper concentrates on the computational challenge in multidisciplinary design optimization (MDO) and a comprehensive strategy combining enhanced collaborative optimization (ECO) and kriging approximation models is introduced. In this strategy, the computational and organizational advantages of original collaborative optimization (CO) are inherited by ECO, which can satisfy the strengthened consistency requirements. Kriging approximation models are constructed to replace high-fidelity simulation models in individual disciplines and reduce the expensive computational cost in practical MDO problems. The proposed methodology is demonstrated by solving the classical speed reducer design problem. The better results indicate that ECO using kriging approximation models can achieve a considerable reduction of computational expense while guaranteeing the accuracy of optimal solutions with efficient convergence.

Abstract: For highly-reliable products, Accelerated Degradation Testing (ADT) data can provide useful reliability information. Moreover, Step-Stress Accelerated Degradation Testing (SSADT) usually requires a less sample size, shorter time and less cost than Constant-Stress Accelerated Degradation Testing (CSADT). However, in designing an efficient SSADT, the issue about how to choose accelerated stress level was seldom discussed. In this study, first we use drift Brownian motion to model a typical SSADT performance degradation process. Then, under the situation that total experiment cost is not given while the sample size, total test time and the interval of performance inspection are specified, our objective is to minimize the asymptotic variance of the estimation of the reliability of the pth quantile of product’s lifetime under use condition. Form the derivation of our objective, we find a way to improve the speed of optimal algorithm for SSADT. The optimal plan can give the stress levels and test time at each stress level. Finally a simulation example is used to illustrate the proposed method.

Abstract: To realize the integration of process planning and scheduling (IPPS) in the manufacturing system, a particle swarm optimization (PSO) algorithm is utilized. Based on the general PSO (GPSO) model, one GPSO algorithm is projected to solve IPPS. In GPSO, crossover and mutation operations of genetic algorithm are respectively used for particles to exchange information and search randomly, and tabu search (TS) is used for particles’ local search. And time varying crossover probability and time varying maximum step size of tabu search are introduced. Experimental results show that IPPS can be solved by GPSO effectively. The feasibility of the proposed GPSO model and the significance of the research on IPPS are also demonstrated.

Abstract: Friction under vibration condition presents extremely different complex characteristics from that of the conventional state. Practice shows that machine power rises obviously with the significant decrease of the fiction. However, occurrence mechanism of the vibration is not fully studied or revealed; therefore, how to further develop the benefits of vibration, there is no concrete and clear measures yet. From this actual situation, this work want to reveal the characters of nonlinear dynamic of the vibration friction, analyze the relationship between vibration and friction, discuss the impact of vibration’s parameters on the friction mechanism, Theoretical study and experimental verification were conducted to improve the work efficiency of the related equipments with the benefits of the vibration friction.