有固相析出的多效两段蒸发 系统模型与过程模拟

建立了带有冷凝水闪蒸的有固相析出的多效两段蒸发系统的常规设计数学模型,模型将系统的相平衡关系用回归式表达,使模型可以用计算机编程求解,避免了手工计算结合查相图的烦琐的计算过程;利用矩阵方程具有结构清晰和高度模块化的特点,将系统的物料衡算和热量衡算方程组写成矩阵方程的形式,只要保留或舍弃矩阵方程中的相关块矩阵,模型就能代表没有冷凝水闪蒸或没有固相析出的多效两段蒸发系统常规设计模型;采用迭代法结合矩阵法来求解模型,算例表明,冷凝水闪蒸对多效两段蒸发系统是有效的节能措施,算法收敛速度快、收敛稳定性好。     

Automatic process plan generation in an operative process planning system

The architecture and design of process planning systems should follow the architecture and design of the manufacturing systems they are intended to serve. This article describes a process planning system specifically intended for a workshop orientated factory, a factory which is specialized for the production of a limited number of group technological product lines. The goal of the system is to generate automatically and rapidly reliable part programs from order information. With the system, a process plan can be generated by workshop personnel on the basis of process plan specifications stored in part family models. A part program generation algorithm can then create a part program automatically by pasting together segments of program code stored in the process models of the system. The part program generator can be tailored by new parametric part program definitions related to features. The tool paths of the generated code can be visualised. The system described forms the operative process planner part of the MCOES (BE-3528) process planning system.     

A green productivity based process planning system for a machining process

In the metal cutting industry, manufacturers have strived to increase energy efficiency and to reduce environmental burdens through the use of dust collectors and waste disposers. It is more beneficial and efficient to apply the front-of-pipe technology that prevents the sources of pollutants and minimises energy use through the redesign of products and the change of process planning and machining operations. In particular, process planning for the environment, called eco-process planning, is central to increasing energy efficiency and reducing environmental burdens because process planning decisions greatly influence machining performance. At present, greenability, a term used to indicate environmental friendliness, has been little considered as a major concern in the process planning stage because process planning decisions have focused on improving productivity aspects that include speed, cost and quality. Thus, it is essential to develop an eco-process planning approach that enables the harmonisation and enhancement of greenability performance while improving productivity performance, termed green productivity (GP). This paper presents the development of a GP-based process planning algorithm that enables the derivation of process parameters for improving GP in machining operations. The core mechanism of the algorithm is the realisation of the process improvement cycle that measures GP performance by the collection of machining data, quantifies this performance by categorical representation and predicts the performance through prediction models. To show the feasibility and applicability of the proposed algorithm, we have conducted an experiment and implemented a prototype system for a turning machining process.     

An intelligent process planning system for micro turn-mill parts

An attempt has been made to develop a generalised system for the generation of process plan for the manufacture of micro parts in this work. It has two components; first one deals with automatic part feature extraction from feature-based model and second one performs the execution of process planning activities in accordance with feature using knowledge-based system approach. The proposed system maps extensible markup language (XML) data for the feature based-model and produces the corresponding manufacturing activities needed for the manufacture of micro parts. The process plan modules considered in this work includes process sequence, tools and fixtures, process parameters selection and set-up plan generation. An attempt has been made to develop process parameters selection module based on experimental investigation and optimisation apart from manufacturing catalogues and user manuals. Feature extraction through XML files avoids complex feature extraction process. The application of the developed system has been verified with a case study. The present system is limited to micro turn-mill features. Incorporation of more micro features and consideration of other activities of process plan ensures a complete process planning system for micro-machining processes.     

An intelligent feature-based process planning system for prismatic parts

Today, feature-based design has become a core technology for solid product modelling primarily because it can capture the designer's intent and provide the capability to satisfy the informational needs of the down-line application tasks for CAD/CAM integration. This paper reports the development of an intelligent environment, IFPP (Intelligent Feature-based Process Planning), for the feature-based design synthesis and process planning of prismatic parts to be produced on CNC machining centres. IFPP consists of two functional modules, namely Feature Based Modeller (FBM) and Automatic process Planner (AutoPlan). The FBM provides a graphical environment for the feature-based synthesis, validation and representation of the solid model of the part to be produced. AutoPlan maps this feature information to the corresponding machining processes to generate the operation plan and corresponding CNC code. This CNC code is unique in that it is functionally encapsulated with the feature data to provide a 'Variant' strategy utilizing the special parametric programming facilities provided on the controller. IFPP thus demonstrates an integrated part-process environment that enables quick turnaround from design to manufacture.     

Development of a geometry-based process planning system for surface micromachining

There are many CAD systems developed for the design and fabrication of MEMS (Micro-Electro Mechanical Systems). However, most of them simulate the construction process given the two-dimensional mask data, and few systems generate the fabrication process plan from a designed model. Furthermore, the current systems simulate the construction process based on the two-dimensional geometry data. In this paper, a new process planning technique that uses a three-dimensional surface micromachined structure as input is proposed. The system decomposes an imported surface micromachined model into a set of three-dimensional models, each of which has the geometry compatible with the fabrication process, and then groups them for efficient layer generation. Finally, it generates the fabrication order and the masks for all the layers of the structure.     

Phase-field simulation for the evolution of solid/liquid interface front in directional solidification process

In this study, the phase field method was used to study the multi-controlling factors of dendrite growth in directional solidification. The effects of temperature gradient, propelling velocity, thermal disturbance and growth orientation angle on the growth morphology of the dendritic growth in the solid/liquid interface were discussed. It is found that the redistribution of solute leads to multilevel cavity and multilevel fusion to form multistage solute segregation, and the increase of temperature gradient and propelling velocity can accelerate the dendrite growth of directional solidification, and also make the second dendrites more developed, which reduces the primary distance and the solute segregation. When the temperature gradient is large, the solid-liquid interface will move forward in a flat interface mode, and the thermal disturbance does not affect the steady state behavior of the directionally solidified dendrite tip. It only promotes the generation and growth of the second dendrites and forms the asymmetric dendrite. Meanwhile, it is found that the inclined dendrite is at a disadvantage in the competitive growth compared to the normal dendrite, and generally it will disappear. When the inclination angle is large, the initial primary dendrite may be eliminated by its secondary or third dendrite.     

Integrative process plan model and representation for intelligent distributed manufacturing planning

Process planning is one of the key functions for product design and manufacturing. Process plans have very great impact on all phases of product design and manufacture. Therefore, it is necessary to establish a high level of interaction between different product design activities and their tight integration into a coherent system. In this paper we describe a process plan model that allows for such integration. The framework for integration is briefly described and the process plan model that considers three dimensions of planning is explained. The manufacturing process plan model is defined as a three-dimensional model with the following dimensions: time/order, variability/alternatives, and aggregation. All three dimensions are defined and explained as they relate to overall manufacturing planning. The nature of these dimensions is illustrated with several examples. The implementation of the framework and the model within the distributed system IMPlanner is presented. The prototype has been implemented in the Java language and the model for data storage has been implemented in XML. The benefits of integrated consideration are described for several currently implemented applications such as feature modelling, process visualization, process network generation, cell formation, and scheduling.     

Power system transmission network expansion planning using AC model

An optimisation technique to solve transmission network expansion planning problem, using the AC model, is presented. This is a very complex mixed integer nonlinear programming problem. A constructive heuristic algorithm aimed at obtaining an excellent quality solution for this problem is presented. An interior point method is employed to solve nonlinear programming problems during the solution steps of the algorithm. Results of the tests, carried out with three electrical energy systems, show the capabilities of the method and also the viability of using the AC model to solve the problem.     

Instabilities of the liquid solid interface

Bodensohn et al.¹ observed that a sudden temperature change of the liquid above 1.1 K caused the interface between solid and liquid⁴He to become corrugated; they proposed that the instability of the interface was caused by the introduction of a heat current induced by the temperature gradient. Subsequently Grinfeld² showed that a non hydrostatic stress of the crystal could cause an instability; this idea was put forward by Balibar, Edwards and Saam³ to explain the observation of Bodensohn et al. A more detailed analysis has been given recently by Bowley and Nozières⁴. The two causes of instability are analyzed in the present paper for both normal³He and superfluid⁴He. The phase diagram and critical heat current for normal³He are presented. The corrugations will appear most rapidly near the minimum of the melting curve at 0.32 K and need a temperature gradient of order a few µK/cm. For superfluid⁴He the inability of the liquid to support thermal conduction (heat is transported by second sound) changes the nature of the instability, with the result that dissipation at the interface becomes important. As a consequence only the Grinfeld instability is observable in practice so that corrugations appear with wavelength between 6 and 8 mm.     

A generative process planning system for parts produced by rapid prototyping

This paper presents a generative process planning system for parts produced by the rapid prototyping process (i.e. fused deposition modelling–FDM). The proposed process planning involves optimal selection of orientating the model with a proper support structure and then provides an intelligent slicing methodology, such as direct or adaptive, to minimise the built up time, keeping the geometry and cusp height errors in control. Pre- and post-slicing processes have been used to minimise the sliced data error. The Computer Aided Process Planning (CAPP) model has been arranged into five modules: orientation, support structure generation, slicing, path planning and Numerical Control (NC) program generation, and model build up. The CAPP model has been implemented in C language having a unique methodology consisting of 42 simplified steps. The CAPP model has been tested for several examples and shows satisfactory results.     

A piezoelectric-inhomogeneity system with imperfect interface

This paper examines the electro-mechanical fields for a circular anisotropic piezoelectric fiber sensor inside an anisotropic piezoelectric or non-piezoelectric elastic matrix with imperfect interface under remote in-plane uniform tension. The interface imperfection is posed on the mechanical fields only. The present formulation admits different boundary value problems in a unified manner, so various fiber–matrix interface conditions are considered: (1) perfect bonding; (2) pure debonding; (3) in-plane pure sliding; (4) out-of-plane pure sliding; (5) full debonding; and (6) partial debonding. An interface condition is modeled by a specific layer of mechanical springs with vanishing thickness, namely k_sd for normal debonding, k_st for in-plane sliding, and k_sv for out-of-plane sliding. Partial debonding is the one that allows to represent intermediate states between cases (1)–(5) above, for which the spring constants can take on any arbitrary values. An accurate three-dimensional approach in conjunction with an energy formulation based on linear theory of piezoelectricity is presented. The generalized displacement field is expressed in terms of series involving some appropriate amending functions. In the context of the present study the nature of the solution satisfies the necessary continuity in the electric potential across the fiber–matrix interface, while accounting for possible discontinuity in its derivative at the interface. This consideration accelerates the convergence rate significantly.     

舰船装备保障系统规划模型研究

针对舰船装备保障系统规划的系统性与复杂性,基于装备保障工程实践,研究提出了舰船装备保障系统规划模型,将规划要素分解为保障需求、能力建设和组织实施三个方面,并建立了核心问题的分层结构与映射关系。构建了舰船装备技术保障任务框架体系,设计了舰船寿命期修理结构论证模型,探索了舰船装备维修设计方法,突破了舰船装备保障系统规划的关键技术。该规划模型能够为研制阶段同步开展舰船装备保障系统配套建设,有序推进技术保障工作,加快形成保障能力提供理论支撑。     

The planning of a manufacturing system: a dynamic model

The paper studies a dynamical model of a manufacturing process taking into account:

the purchase of raw materials;

the scheduling of production;

the planning of sales.

We particularly deal with the planning of the production rate and of sales.

The basic hypotheses are:

the orders of each finished product are known over a given period of time

T;

the inventory levels are the state variables of the process;

the control variables are the purchase, productiqn and sale rates.

The goal of the ‘controller’ is to determine a policy which allows him to minimize at the time T the ‘capital’. As ‘capital’ we consider both the financial means and the technological resources employed in the process. Bilateral constraints in state and control variables have been introduced in our model.

The Maximum Principle has been used to formulate the problem and to obtain a solution.     

Integration of process planning and scheduling by exploring the flexibility of process planning

A unique method for the integration of process planning and scheduling in a batch-manufacturing environment is reported. This integration is essential for the optimum use of production resources and for the generation of realistic process plans that can be readily executed with little modification. The integration problem is modelled at two levels: process planning and scheduling, which are linked by an intelligent facilitator. The process-planning module employs an optimization approach in which the whole plan solution space in terms of available machines, tools, tool accessibility and precedence constraints is first generated and a search algorithm is then used to find the optimal plan. For a given set of jobs, the scheduling module takes the optimal plans for each job and generates a schedule based on a given criterion, as well as the performance parameters (machine utilization and number of tardy jobs). An unsatisfied performance parameter is fed back to the facilitator, which then identifies a particular job and issues a change to its process plan solution space. The iteration of process Planning -scheduling-solution space modification continues until a schedule is satisfactory or until no further improvement can be made. The uniqueness of this approach is characterized by the flexibility of the process-planning strategy and the intelligent facilitator, which makes full use of the plan solution space intuitively to reach a satisfactory schedule. (It may not be the optimal, though.) The integrated system was implemented in the manufacturing of prismatic parts. The testing results show that the developed integration method can achieve satisfactory process plans and a schedule in an effective and efficient manner.