CASE-BASED PRODUCT CONFIGURATION AND REUSE IN MASS CUSTOMIZATION

The increasing complexity and size of configuration knowledge bases requres the provisionof advanced methods supporting the development of the actual configuration process and design reuse.A new framework to find a feasible and practical product configuration method is presented in masscustomization. The basic idea of the appoach is to integrate case-based reasoning (CBR) with a con-straint satisfaction problem(CSP). The similarity measure between a crisp and range is also given,which is common in case retrieves. Based on the configuration model, a product platform and customerneeds, case adaptation is carried out with the repair-based algorithm. Lastly, the methodology in theelevator configuration design domain is tested.     

DISTRIBUTED MONITORING SYSTEM RELIABILITY ESTIMATION WITH CONSIDERATION OF STATISTICAL UNCERTAINTY

Taking into account the whole system structure and the component reliability estimation uncertainty, a system reliability estimation method based on probability and statistical theory for distributed monitoring systems is presented. The variance and confidence intervals of the system reliability estimation are obtained by expressing system reliability as a linear sum of products of higher order moments of component reliability estimates when the number of component or system survivals obeys binomial distribution. The eigenfunction of binomial distribution is used to determine the moments of component reliability estimates, and a symbolic matrix which can facilitate the search of explicit system reliability estimates is proposed. Furthermore, a case of application is used to illustrate the procedure, and with the help of this example, various issues such as the applicability of this estimation model, and measures to improve system reliability of monitoring systems are discussed.     

RELIABILITY-BASED DESIGN AND ANALYSIS ON HYDRAULIC SYSTEM FOR SYNTHETIC RUBBER PRESS

To overcome the design limitations of traditional hydraulic control system for synthetic rubber press and such faults as high fault rate, low reliability, high energy-consuming and which always led to shutting down of post-treatment product line for synthetic rubber, brand-new hydraulic system combining with PC control and two-way cartridge valves for the press is developed, whose reliability is analyzed, reliability model of the hydraulic system for the press is established by analyzing processing steps, and reliability simulation of each step and the whole system is carried out by software MATLAB, which is verified through reliability test. The fixed time test has proved not that theory analysis is sound, but the system has characteristics of reasonable design and high reliability, and can lower the required power supply and operational energy cost.     

Modeling,Simulation and Control of Pulsed DE-GMA Welding Process for Joining of Aluminum to Steel

Joining of aluminum to steel has attracted significant attention from the welding research community,automotive and rail transportation industries.Many current welding methods have been developed and applied,however,they can not precisely control the heat input to work-piece,they are high costs,low efficiency and consist lots of complex welding devices,and the generated intermetallic compound layer in weld bead interface is thicker.A novel pulsed double electrode gas metal arc welding（Pulsed DE-GMAW）method is developed.To achieve a stable welding process for joining of aluminum to steel,a mathematical model of coupled arc is established,and a new control scheme that uses the average feedback arc voltage of main loop to adjust the wire feed speed to control coupled arc length is proposed and developed.Then,the impulse control simulation of coupled arc length,wire feed speed and wire extension is conducted to demonstrate the mathematical model and predict the stability of welding process by changing the distance of contact tip to work-piece（CTWD）.To prove the proposed PSO based PID control scheme’s feasibility,the rapid prototyping experimental system is setup and the bead-on-plate control experiments are conducted to join aluminum to steel.The impulse control simulation shows that the established model can accurately represent the variation of coupled arc length,wire feed speed and the average main arc voltage when the welding process is disturbed,and the developed controller has a faster response and adjustment,only runs about 0.1 s.The captured electric signals show the main arc voltage gradually closes to the supposed arc voltage by adjusting the wire feed speed in 0.8 s.The obtained typical current waveform demonstrates that the main current can be reduced by controlling the bypass current under maintaining a relative large total current.The control experiment proves the accuracy of proposed model and feasibility of new control scheme further.The beautiful and smooth weld beads are also obtained by t     

Reliability sensitivity-based correlation coefficient calculation in structural reliability analysis

The correlation coefficients of random variables of mechanical structures are generally chosen with experience or even ignored,which cannot actually reflect the effects of parameter uncertainties on reliability.To discuss the selection problem of the correlation coefficients from the reliability-based sensitivity point of view,the theory principle of the problem is established based on the results of the reliability sensitivity,and the criterion of correlation among random variables is shown.The values of the correlation coefficients are obtained according to the proposed principle and the reliability sensitivity problem is discussed.Numerical studies have shown the following results:(1) If the sensitivity value of correlation coefficient ρ is less than(at what magnitude 0.000 01),then the correlation could be ignored,which could simplify the procedure without introducing additional error.(2) However,as the difference between ρs,that is the most sensitive to the reliability,and ρR,that is with the smallest reliability,is less than 0.001,ρs is suggested to model the dependency of random variables.This could ensure the robust quality of system without the loss of safety requirement.(3) In the case of |Eabs|ρ0.001 and also |Erel|ρ0.001,ρR should be employed to quantify the correlation among random variables in order to ensure the accuracy of reliability analysis.Application of the proposed approach could provide a practical routine for mechanical design and manufactory to study the reliability and reliability-based sensitivity of basic design variables in mechanical reliability analysis and design.     

Annotation and Retrieval System of CAD Models Based on Functional Semantics

CAD model retrieval based on functional semantics is more significant than content-based 3D model retrieval during the mechanical conceptual design phase. However, relevant research is still not fully discussed. Therefore, a functional semantic-based CAD model annotation and retrieval method is proposed to support mechanical conceptual design and design reuse, inspire designer creativity through existing CAD models, shorten design cycle, and reduce costs. Firstly, the CAD model functional semantic ontology is constructed to formally represent the functional semantics of CAD models and describe the mechanical conceptual design space comprehensively and consistently. Secondly, an approach to represent CAD models as attributed adjacency graphs（AAG） is proposed. In this method, the geometry and topology data are extracted from STEP models. On the basis of AAG, the functional semantics of CAD models are annotated semi-automatically by matching CAD models that contain the partial features of which functional semantics have been annotated manually, thereby constructing CAD Model Repository that supports model retrieval based on functional semantics. Thirdly, a CAD model retrieval algorithm that supports multi-function extended retrieval is proposed to explore more potential creative design knowledge in the semantic level. Finally, a prototype system, called Functional Semantic-based CAD Model Annotation and Retrieval System（FSMARS）, is implemented. A case demonstrates that FSMARS can successfully botain multiple potential CAD models that conform to the desired function. The proposed research addresses actual needs and presents a new way to acquire CAD models in the mechanical conceptual design phase.     

CONSTRUCTION METHOD OF KNOWLEDGE MAP BASED ON DESIGN PROCESS

Due to the increasing amount and complexity of knowledge in product design, the know-ledge map based on design process is presented as a tool to reuse product design process, promote the product design knowledge sharing. The relationship between design task flow and knowledge flow is discussed; A knowledge organizing method based on design task decomposition and a visualization method to support the knowledge retrieving and sharing in product design are proposed. And a knowledge map system to manage the knowledge in product design process is built with Visual C++ and SVG. Finally, a brief case study is provided to illustrate the construction and application of knowledge map in fuel pump design.     

Characteristic verification and parameter optimization of airbags cushion system for airborne vehicle

Abstract： The major methods to investigate the airbags cushion system are experimental method, thermodynamic method and finite element method （FEM）. Airbags cushion systems are very complicated and very difficult to be investigated thoroughly by such methods For experimental method, it is nearly impossible to completely analyze and optimize the cushion characteristics of airbags of airborne vehicle because of charge issue, safety concern and time constraint. Thermodynamic method fails to take the non-linear effects of large airbag deformation and varied contact conditions into consideration. For finite element method, the FE model is usually complicated and the calculation takes tens of hours of CPU time. As a result, the optimization of the design based on a nonlinear model is very difficult by traditional iterative approach method. In this paper, a model based on FEM and control volume method is proposed to simulate landing cushion process of airborne vehicle with airbags cushion system in order to analyze and optimize the parameters in airbags cushion system. At first, the performance of airbags cushion system model is verified experimentally. In airdrop test, accelerometers are fixed in 4 test points distributed over engine mount, top, bottom and side armor plate of hull to obtain acceleration curves with time. The simulation results are obtained under the same conditions of the airdrop test and the simulation results agree very well with the experimental results, which indicate the established model is valid for further optimization. To optimize the parameters of airbags, equivalent response model based on Latin Hypercube DOE and radial basis function is employed instead of the complex finite element model. Then the optimal results based on equivalent response model are obtained using simulated annealing algorithm. After optimization, the maximal acceleration of airborne vehicle landing reduces 19.83%, while the energy absorption by airbags increases 7.85%. The performance of the airbags cushion system thus is largely improved through optimization, which indicates the proposed method has the capability of solving the parameter optimization problem of airbags cushion system for airborne vehicle.     

Analysis of collapse in flattening a micro-grooved heat pipe by lateral compression

The collapse of thin-walled micro-grooved heat pipes is a common phenomenon in the tube flattening process, which seriously influences the heat transfer performance and appearance of heat pipe. At present, there is no other better method to solve this problem. A new method by heating the heat pipe is proposed to eliminate the collapse during the flattening process. The effectiveness of the proposed method is investigated through a theoretical model, a finite element(FE) analysis, and experimental method. Firstly, A theoretical model based on a deformation model of six plastic hinges and the Antoine equation of the working fluid is established to analyze the collapse of thin walls at different temperatures. Then, the FE simulation and experiments of flattening process at different temperatures are carried out and compared with theoretical model. Finally, the FE model is followed to study the loads of the plates at different temperatures and heights of flattened heat pipes. The results of the theoretical model conform to those of the FE simulation and experiments in the flattened zone. The collapse occurs at room temperature. As the temperature increases, the collapse decreases and finally disappears at approximately 130 ℃ for various heights of flattened heat pipes. The loads of the moving plate increase as the temperature increases. Thus, the reasonable temperature for eliminating the collapse and reducing the load is approximately 130 ℃. The advantage of the proposed method is that the collapse is reduced or eliminated by means of the thermal deformation characteristic of heat pipe itself instead of by external support. As a result, the heat transfer efficiency of heat pipe is raised.     

基于事例的供应商选择模型与方法研究

供应商选择是供应链管理的重要内容。本文根据供应商选择的特点,采用基于事例推理的技术研究供应商选择的决策方法,建立了基于事例推理的供应商选择过程模型。进一步,应用模糊集理论,研究了供应商选择事例的表示与检索,提出了一种考虑模糊特征隶属度函数值的相似度检索方法。最后,给出了基于事例的供应商选择系统的应用实例。     

A Case-Based Computer-Aided Process-Planning System for Machining Prismatic Components

This article deals with a process-planning system that uses case-based reasoning methodology. Briefly, case-based reasoning is an intelligent problem-solving technique which works by searching through a database for previously solved problems for one or more cases whose identifying features closely resemble the current problem. The case-based reasoning system used in this article to develop a process plan, typically consists of three modules, i.e. the part input and representation module, the case retrieval, and case adoption module. In this paper, new approaches have been proposed in all three modules. By incorporating a multiparametric and absolute-matching technique, the case retrieval module especially has become more powerful. A practical approach has been suggested in this research to compute the similarity between part input and case. An illustrative example is included to demonstrate the proposed system.     

CBR诊断系统实例获取的合成相似性度量方法

考虑到车辆故障产生的复杂性及系统诊断的特点,采用实例推理诊断方法,而实例推理的关键在于相似实例的获取。针对实例属性存在模糊性的特点,把模糊集概念用于实例的获取中,提出一种实例获取算法——分级合成相似性度量算法,该算法充分考虑到模糊集中心距对实例相似度的影响。最后给出轮胎异常磨损的算法示例,验证了该算法的简洁、合理和有效性。     

基于实例的装配顺序规划技术研究

研究装配实例表示与重用技术，提出一种基于实例的装配顺序规划方法。通过对装配知识的组织来构造装配实例模型，采用基于相似度的实例检索算法，通过实例的检索获得符合设计要求的最佳匹配实例。以某机型机翼为例进行验证。     

基于粒子群优化案例推理的RH终点温度预测

针对RH流程终点钢温预报问题,提出了一种基于多元线性回归和粒子群优化算法改良的案例推理方法。首先,对待一般案例推理方法中缺乏影响因素的问题,利用多元线性回归的方法进行属性约简;其次,面对案例检索中相似度计算缺乏权重计算方法的问题,采用粒子群优化算法对权值进行优化;最后,基于简化的影响因素和优化权重,采用改进的灰色关联相似性的案例检索来预测RH终点的钢水温度。利用某钢铁厂RH工艺的实际生产数据,分别对多元线性回归、BP神经网络、一般案例推理方法和粒子群优化案例推理方法进行测试,从结果可以看出,文中所使用的基于粒子群优化过的案例推理方法的预报精度,相较于多元线性回归,BP神经网络以及一般案例推理更加准确。     

FSM-Monitoring of Fatigue Crack in Lattice-Stiffened Steel Plate Deck for Bridge Structures

For elucidating applicability of FSM （field signature method） on detection of fatigue crack initiation and monitoring of its propagation, a series of fatigue tests on steel plate decks （4,625 × 2,250 mm^2） stiffened in lattice-shape by longitudinal and lateral ribs was carried out by using a wheel load traveling test machine. The fatigue crack was observed by visual inspection at the weld toe between the deck plate and the longitudinal rib when the number of wheel load traveling repetition was around 210 thousands. The response of FSM-monitoring, which was the potential difference change between the sensing pins （pair）, became clear when the number of the repetition was around 190 thousands. The fatigue crack initiation could be detected by FSM considerably earlier than visual inspection. The fatigue crack propagation such as the direction could also be monitored even though the distance of the sensing pins was extended to 230 mm. On the other hand, the electric field analysis for the virgin situation without any cracks was carried out. The results of analysis indicated that 60 mm length of crack which could not be confirmed by visual inspection could be detected by FSM.     

实例检索策略及其在减速器零件CAPP中的应用

针对ＣＡＰＰ中实例零件的相似性检索，从加工工艺的角度出发，提出了基于加工特征和进刀方向的相似性判定准则以及三级搜索策略，提高了实例匹配的准确性，使实例工艺的重要性增强。该方法已应用到所开发的减速器主要零件通用型ＣＡＰＰ系统，该系统将派生式和基于实例方法集成一体，既具有派生式适应性强的优点，又充分利用了以往成熟的工艺实例。     

实例检索在工程机械测试性设计实例库中的应用

将实例检索运用到工程机械的测试性设计中可以很好地解决重复性建模、建模过程复杂等问题.首先介绍了实例推理技术（CBR）的原理,然后着重介绍了属性相似度和权重的计算方法,并参照工程机械的测试性需求影响因素,建立了工程机械测试性设计的实例库,最后,结合实例对设计效果进行了检验.     

Indexing and retrieval in case-based process planning for multi-stage non-axisymmetric deep drawing

This paper presents a case-based reasoning (CBR) methodology for computer-aided process planning (CAPP) for multi-stage, non-axisymmetric sheet metal deep drawing. The methodology addresses the indexing and retrieval of process planning cases. Planning cases are indexed via a feature-based representation of deep drawn parts. Efficient case retrieval is achieved by a feature-based similarity analysis between a new deep drawn part and existing parts in the case library. An illustrative example is included to demonstrate the operation of the proposed approach and show its effectiveness in speeding up CAPP for multi-stage non-axisymmetric deep drawing. This revised version was published online in April 2005 with a correction to the corresponding author’s address.     

Acoustic Resonance in Exhaust Gas Economizer Tube Bundles Prediction and Suppression of Resonance

The tendency for air column resonance generation in structures with a constant volume behind a tube array like that of an exhaust gas economizer has been reported, but many points remain unclear with respect to the mechanism and conditions that generate acoustical resonance. When acoustical resonance is generated, in reality, prevention and suppression measures are implemented by inserting a baffle plate into the ducts through a process of trial and error. The purpose of this study is to clarify the mechanism of generation of acoustical resonance, and to establish an appropriate measure to prevent such resonance. Noise generated in an exhaust gas economizer was correlated with the flow inside the tube array and experimentally analyzed, and the mechanism for resonance generation was considered. In addition, the effectiveness of a baffle plate positioned in order to prevent resonance was investigated. We have successfully employed a single baffle plate to suppress resonance.