A mathematical model for assessing the effects of a lot splitting feature on a dynamic cellular manufacturing system

Numerous studies have been carried out in the field of cellular manufacturing systems (CMS) by considering different types of production costs. In all the presented models, it has been assumed that either the production lot of a part type should be processed by only one machine or it can be split among several machines. To the best of our knowledge, there is no research considering the advantages and disadvantages of the lot splitting feature in designing a CMS under a dynamic environment. In this paper, a mixed-integer nonlinear programming model is formulated to design a dynamic CMS by considering the burdened costs of processing part operations, idleness of cells and machines, inter-cell movements, installation/uninstallation of machines, machine overhead, production lost, splitting production lots and dispersing machines among cells. Furthermore, the advantages and disadvantages of the lot splitting feature are investigated by regarding its effect on the burdened costs. After linearization, an illustrative numerical example is solved by GAMS software (CPLEX solver) to illustrate the model performance and analyze the effect of the lot splitting feature. Since the given problem is NP-hard, an efficient simulated annealing algorithm is developed and tested using several test problems.     

接地板级进模设计与制造

介绍了接地板多工位级进模的结构特点和设计要点,分析了模具设计中的技术问题,得出了排样设计和解决内凹弯曲件的卸料问题的方法,对同类零件的模具设计有一定的借鉴作用.     

一种求解矩形件排样问题的启发式算法

研究在一定的矩形板材上排放所需要小矩形的优化排样问题,提出一种基于4块结构排放模式的启发式算法,并且建立了动态规划模型。通过对在计算机上随机产生的试验数据的模拟计算,获得了比遗传算法更好的解,是一种行之有效的方法。     

一种矩形排样问题的优化设计方法

研究了在一定矩形板材上排放所需要小矩形的优化排样问题,提出了一种基于四块结构和一般分块排样模式的新方法,分析了四块结构模式和一般分块模式的特点,并且根据该分块的思想建立了动态规划模型.通过对在计算机上随机产生的试验数据的数值计算,表明该方法获得了比遗传算法更好的解,是一种行之有效的方法.类似文中矩形件排样问题完全可以用该方法来求解,选定合理的参数可以在比较短的时间里得到近似最优解,并且该算法具有一定的鲁棒性.如何把这种分块的启发式思想应用到不规则二维排样和一般的三维排样中去是今后的研究目标.     

压载水舱牺牲阳极优化布置研究

本文介绍了船舶压载水舱的腐蚀与防腐控制的特殊性,探索了一种利用人工神经网络算法和遗传算法进行压载水舱阴极保护设计中的牺牲阳极优化布置的方法。该方法能够使压载水舱的腐蚀得到更为有效的控制,对于船体及其他海洋结构物的阴极保护设计也具有参考价值。     

An investigation into the use of spatial coordinates for the genetic algorithm based solution of the fixture layout optimization problem

The fixture layout optimization problem is highly modal. It has been shown that layout optimization methods that use the genetic algorithm (GA) are effective at finding high quality solutions. To date, such methods have used FEA node numbers to represent the locations of fixture elements. This paper presents a new GA based optimization method that uses spatial coordinates to represent the locations of fixture elements. This method integrates a number of important GA concepts such as real encoding, increased mutation, and sharing. Test results show that the new method provides higher quality solutions with substantially less numbers of generations than the old method. These results also show that the use of increased mutation and sharing significantly improves the performance of the new method.     

多输入／多输出GA-BP网络压铸工艺参数设计系统

遗传算法全局搜索能力强,而BP神经网络擅长局部精确搜索,采用遗传算法优化神经网络初始权值的方法,实现两种算法的结合,达到优势互补,并首次将内浇口类型及其厚度作为设计输出参数引入设计系统,构建更实用的压铸工艺参数优化设计多输入/多输出双隐层GA-BP神经网络。通过实例,验证了本系统所给出的压铸工艺设计结果的合理性。     

基于最优同质块的分段式矩形优化排样

为有效解决企业实际生产中的矩形优化排样问题,对矩形优化算法进行研究,提出基于最优同质块的分段式矩形优化排样算法,有效解决了企业实际生产中的剪切排样问题。该算法首先使用剪床将板材剪成不同长度的子段,然后在子段上基于最优同质块进行优化排样。算法将板材的分段问题以及最优同质块在子段上的最优排样问题均转化为背包问题,并基于动态规划算法求解;使用枚举法求解最优同质块排样。将板材分成若干个子段使算法可以有效解决长板排样问题,使用最优同质块对子段进行优化排样使算法的优化性能得到提高。两组实例应用表明本文算法优于文献中的其他算法。     

基于同质条带的两段式有约束矩形优化排样

为了有效解决企业生产中的有约束矩形优化排样问题，对矩形优化排样算法进行研究，在综合考虑原材料利用率及切割工艺复杂度的情况下，给出基于同质条带的两段式有约束矩形优化排样算法。算法首先通过问题转换，将有约束矩形优化排样问题转化成多重背包问题，然后再基于动态规划算法对其进行求解，最后基于动态规划算法开发了一应用系统，有效地解决了企业实际生产中的有约束矩形优化排样问题。实例应用表明，该算法在求解有约束矩形优化排样问题方面优于其他算法。     

Evaluation of the equivalent time of non-isothermal diffusion processes in the heat-affected zone in fusion welding

A technique for transforming an anisothermic diffusion problem (when the diffusion coefficient is not constant) into an isothermal problem (when the diffusion coefficient is constant) is proposed. It is based on the equivalent time concept. The interrelation between equivalent time and real time is established. The technique enables one to use the known analytical solutions of the linear diffusion problems. It is shown that preheating intensifies carbon diffusion in the heat-affected zone.     

An effective hybrid immune-hill climbing optimization approach for solving design and manufacturing optimization problems in industry

The focus of this research is on a hybrid method combining immune algorithm with a hill climbing local search algorithm for solving complex real-world optimization problems. The objective is to contribute to the development of more efficient optimization approaches with the help of immune algorithm and hill climbing algorithm. The hybrid algorithm combines the exploration speed of immune algorithm with the powerful ability to avoid being trapped in local minimum of hill climbing. This hybridization results in a solution that leads to better parameter values. This research is the first application of immune algorithm to the optimization of machining parameters in turning and also shape design optimization problems in the literature. The results of single-objective benchmark problem, multi-objective disc-brake problem, an automobile shape design optimization problem taken from the literature and case studies for multi-pass turning operation have demonstrated the superiority of the proposed hybrid over the other techniques in terms of solution quality and convergence rates.     

基于智能优化算法的设备布局设计

制造系统的设备布局与生产率和生产成本密切相关,布局设计是制造系统设计者面临的关键问题之一.文章针对布局问题的平方分派模型,构建了一种布局设计的混合智能优化算法--遗传退火算法 ,并分析了算法实现的方法.实例表明遗传退火算法的高效性.     

矩形件优化排样算法与系统的研究

为了有效解决矩形件优化排样问题,通过在已有动态规划算法的基础之上,引入多种启发式策略,提出一种带有启发式策略的动态规划算法,并设计和开发了一个基于该算法的矩形件优化排样系统。介绍了系统的总体设计方案。并通过实例测试,讨论了矩形件优化排样算法的有效性和系统的实用性,证明矩形件优化排样算法具有排样过程耗时少、效果好和适用范围广3大优点,可以有效地提高材料利用率和生产效率。     

变速箱体生产线三维动态模拟图形设计

对虚拟加工环境中变速箱体生产线三维动态模拟图形设计进行了研究,用机械加工的方法制造箱体零件虚拟模型,简化了原型的创作,将CAD/CAM、工工平面布置DSS与三维动态模拟有效结合。三维动态图形设计制造模拟可检查CAD/CAM、工艺布置DSS设计与决策中的一些问题,并找出解决方案,缩短了产品设计制造周期,降低了成本。     

Designing a Turbine Blade Cooling System Using a Generalised Regression Genetic Algorithm

The design of a turbine blade cooling system is a multi-objective optimisation problem involving constraints and complex Interaction among its design variables. The aim of this paper is to develop a methodology to optimise this design using Evolutionary Computing techniques. This paper presents Generalised Regression Genetic Algorithm (GRGA) and the mathematical model of a real-life turbine blade cooling system. Even in the presence of variable interaction, the methodology identifies a number of good feasible designs from which one could be finally chosen based on designer's preferences. The research also demonstrates that GRGA is capable of optimising a real-life design.     

UPVC低发泡挤出制品内空缺陷的产生原因与解决措施

阐述了UPVC低发泡挤出制品内空缺陷的产生原因与解决措施,指出在UPVC低发泡挤出成型中,原料配方的配制及混合工艺、挤出设备及工艺参数设计的合理性,是消除制品内空缺陷的基本条件;而在挤出成型模设计中,发泡倍率的设计、模口缝隙形状与排布、挤出流道内的熔体压力控制等技术参数,是消除制品内空缺陷的关键。     

交互式斜楔在冲模中应用

在汽车冲压模具设计过程中,经常会遇到常规结构实现困难的空间干涉问题,本文介绍一些交互式斜楔结构在设计图纸中的应用,分析采用常规结构存在的问题,探讨如何解决空间干涉造成结构设计的困惑及其解决方法,为设计类似问题提供一种新的思路和方法。     

A method for calculating the extent of galvanic corrosion and cathodic protection in metal tubes assuming unidirectional current flow

A simple procedure for calculating how galvanic corrosion and cathodic protection effects are distributed within metallic tubular systems carrying electrolytes is described. The procedure involves the use of equations which are analytical solutions and, in some instances, equations which require numerical solutions which can easily be effected using microcomputers. The equations arc based on an assumption of unidirectional flow of electric current which is shown to be valid for appreciably conducting electrolytes, such as seawater. Various combinations of linear polarisation kinetics, Tafel law polarisation kinetics and totally diffusion-controlled kinetics can be used. Experimental verification of the procedure has been obtained using synthetic seawater for titanium and Cu-30Ni tubes in galvanic contact and for cathodically protected Cu-30Ni tube. It is proposed that the procedure could find useful application at the design stage of plant involving two or three different metals, or of cathodically protected pipework, when any necessary preventative measures indicated by an analysis could be adopted. Plant containing two or three metals can be, for example, in the form of heat-exchangers, pipe to plate combinations or pipework systems connected by plastic sections. Useful design data relating to cathodically-protected pipework can be obtained for systems based on either sacrificial protection or impressed current.     

基于萤火虫算法的螺栓连接结构布局优化

螺栓连接是工程结构的重要连接方式。优化螺栓连接结构的布局可以提高结构的力学性能。建立螺栓连接结构的有限元参数化模型,对连接板和螺栓进行有限元力学分析。运用萤火虫算法对螺栓布局进行优化设计,得到合理的螺栓排布尺寸,减小了孔周应力。当螺栓数量为4个时,与初始设计方案相比,优化后螺栓的分布更加合理,最大孔周应力明显下降。当螺栓数量为6个时,对三排和双排的初始设计方案进行优化,得到相同的双排最优螺栓布局。数值算例表明了萤火虫算法在螺栓连接结构布局优化中的有效性,研究结果可供机械设计参考。     

注射模3D总装配设计

叙述了应用Pro／E进行模具3D总装配设计的基本思路,并结合具体实例说明了应用EMX设计模具总装配的基本流程和具体步骤,该设计思路和方法也适合应用其它软件进行模具的3D总装配设计。