Novel space-based design methodology for preliminary engineering designNahm, Y.-E.; Ishikawa, H.
doi: 10.1007/s00170-004-2463-2pmid: N/A
This work is motivated from set-based concurrent engineering (SBCE) paradigm. In contrast to the traditional design practice, SBCE considers a broader range of design possibilities (i.e., design space) from the outset, explicitly communicates and reasons about sets of design alternatives, and gradually narrows the sets to eliminate inferior alternatives until a final solution remains. Thus, the key to success of SBCE is the proper implementation of the space representation method to define the possible design region, the space mapping method to obtain the performance space achievable by the initial design space, and the space narrowing method to eliminate infeasible subspaces from the initial design space. This paper proposes a novel space-based design methodology for preliminary engineering design. The main characteristic features of our approach are to incorporate the designer’s preference structure with degrees of desirability in specifying both design space and performance space, and to find a ranged set of design solutions that satisfy changing sets of performance requirements through set-to-set space mapping from design space to performance space and space narrowing to eliminate infeasible design subspaces. Central to the proposed design methodology is the integration of meta-modeling techniques, modified fuzzy arithmetic, design of experiment (DoE), robust design techniques, and uncertainty analysis. A preliminary parametric design example of a vehicle side impact beam is demonstrated to show the effectiveness of the proposed methodology and its availability in the large-scale multi-objective design synthesis problem.
Application of fuzzy and rough sets theory in the optimization of machining parameters for mold milling operationsYajun, Jiang; Zhenliang, Lou; Minghui, Li
doi: 10.1007/s00170-004-2472-1pmid: N/A
NC milling operation has become one of the main means of mold manufacturing in recent years, and the determination of milling conditions is important to assure the quality and minimize the costs of molds. This paper first constructs an optimization model of machining parameters for mold milling operations, focusing on minimizing the production costs. Then, based on the properties of the machining parameters database, it also proposes an extended model of fuzzy and rough sets theory for incomplete information systems, including incomplete continuous attribute values, and applies the model to rules learning from the machining database. Thus, by rule reasoning, the feasible solution space of optimization model can be easily established. At last, an example is presented to detail the optimization of machining parameters in the case of the cavity milling of an injection plastic mold.
Application of particle swarm optimisation in artificial neural network for the prediction of tool lifeNatarajan, U.; Periasamy, V.M.; Saravanan, R.
doi: 10.1007/s00170-004-2460-5pmid: N/A
In an advanced manufacturing system, accurate assessment of tool life estimation is very essential for optimising the cutting performance in turning operations. Estimation of tool life generally requires considerable time and material and hence it is a relatively expensive procedure. In this present work, back-propagation feed forward artificial neural network (ANN) has been used for tool life prediction. Speed, feed, depth of cut and flank wear were taken as input parameters and tool life as an output parameter. Twenty-five patterns were used for training the network. Recently there have been significant research efforts to apply evolutionary computational techniques for determining the network weights. Hence an evolutionary technique named particle swarm optimisation has been used instead of a back-propagation algorithm and it is proven that the experimental results matched well with the values predicted by both artificial neural network with back-propagation and the proposed method. It is found that the computational time is greatly reduced by this method .
Digitized die forming system for sheet metal and springback minimizing techniqueCai, Zhong-Yi; Li, Ming-Zhe; Chen, Xi-Di
doi: 10.1007/s00170-004-2459-ypmid: N/A
A flexible production system for sheet metal parts was developed based on the “digitized die” concept. The system can produce a variety of three-dimensional parts without the need for conventional dies, and given only the geometry and the material information of the desired part. The digitized die forming (DDF) system includes the forming press, the shape control system, and software modules with the functions of forming process planning, digitized die shape design, forming process numerical simulation, and springback correction. The digitized die installed in the forming press is the kernel component of the system, it is composed of a pair of matrices of punches, and sheet metal is formed by the enveloping surface of the punches. The working surface of the digitized die are modeled by Non-Uniform Rational B-Spline (NURBS) and constructed by adjusting the height of each punch. Forming process simulation software was developed based on updated Lagrangian formulation and elastic-plastic material model of the finite element, it conducts the numerical simulation to predict the springback and forming defect that may occur in the forming process. A simulation-based approach to compensate for material springback was developed, by correcting the forming surface numerically, an accurate digitized die surface for desired part is obtained. In this paper, the overall structure of the DDF system and the methods of design and control of digitized die shape are described, the detailed steps of the die shape correction for springback and forming process simulation are explained. Applications of the system for the forming of typical sheet metal parts are described .
Injection molding of polymer micro- and sub-micron structures with high-aspect ratiosLiou, A.-C.; Chen, R.-H.
doi: 10.1007/s00170-004-2455-2pmid: N/A
This work studies the injection molding characteristics of polymer micro- and sub-micron structures using demonstration mold inserts with micro- and sub-micron channels with high-aspect ratios. The effects of the injection molding parameters on the achievable aspect ratio of the micro- and sub-micron walls were investigated. Additionally, distinctive mold-filling behaviors and resulting defects were observed for various polymers, such as polymethyl methacrylate (PMMA), polypropylene (PP) and high-density polyethylene (HDPE). Experimental results reveal that the mold temperature determines the success of the injection molding of micro- and sub-micron walls. The satisfactory mold temperature for micro-injection molding significantly exceeds that for traditional injection molding. Moreover, the main injection pressure and the main injection time substantially affect the achievable aspect ratio of the micro- and sub-micron walls. Furthermore, unusual flow behaviors occur and poor molding results are obtained when PP and HDPE are used for micro-injection molding.
Modeling study of the surface tension and gravitational effects on flow injection in center-gated disksLi, C.T.; Wu, B.Y.; Chen, T.S.
doi: 10.1007/s00170-004-2479-7pmid: N/A
Flow injection in center-gated disks was experimentally studied in this paper for possible applications in the manufacturing of composite materials in space. The experimental set-up used in this study was designed to provide flow visualization of the mold filling process. To record the progression of the fluid flow front in the mold, the experiment was filmed using a CCD. The effects of gravitation and surface tension on the development of flow front progression and front shape were examined for a wide range of the governing parameters (namely, the capillary and Stokes numbers). It has been found that surface tension tends to hold the flow front in symmetric shape while gravitation tends to distort it. The balance of these two forces has significant effects on the progression of the flow and the front shape. Results obtained from this experimental model not only validate the finite element method (FEM) model thus developed but also provide useful information in the design of the resin transfer molding process in space.
Using a Nd:YAG laser and six axes robot to cut zinc-coated steelGhany, K. Abdel; Rafea, H. Abdel; Newishy, M.
doi: 10.1007/s00170-004-2468-xpmid: N/A
Zinc-coated steel sheets are important materials in the automobile and home appliance industries. Currently, lasers are the preferred tools for metal cutting because of their good cutting quality, flexibility and excellent features and results, as compared to traditional tools. The solid-state Nd:YAG laser has successfully replaced the gaseous CO2 laser for metal cutting; its small size and short wavelength makes it suitable for cutting bright and metal-coated materials, as well as being able to be transmitted via optical fibers and robots to cut complicated three dimensional and curved shapes. In this work, the Nd:YAG laser is used to cut 1 mm zinc coated steel sheets. We demonstrate the effects of different cutting parameters such as laser power, cutting speed, different gas types and pressures, and focus position on the cutting quality characteristics of attached dross, kerf width and cut surface roughness. Using a six axes robot, cutting speed was limited to 6 m/min because of the noticeable vibration at higher speeds. Results showed that the cutting surfaces achieved were very sharp and smooth. In cutting, Nd:YAG required less power and attained higher speeds than the published results of a CO2 laser, which makes Nd:YAG an economical alternative to cut zinc and metal-coated materials. In addition, laser cutting using robots provided efficient and consistent cutting quality, especially in the case of 3D and countered cutting. Apart from using low speed, robots proved to be more economical than costly, specially designed CNC tables.
A novel approach to manufacturing and experimental investigation of closed-cell Al foamsTzeng, Sheng-Chung; Ma, Wei-Ping
doi: 10.1007/s00170-004-2440-9pmid: N/A
This investigation proposes a modified technique for manufacturing closed-cell aluminum foams to reduce the cost of production of foaming agents during the casting and foaming process. The addition of foaming agents promotes the uniformity of cell sizes and controls the viscosity of the melting aluminum alloy. Moreover, this work elucidates the mechanical characteristics of closed-cell aluminum foams under compressive loading. Discussions cover the compressive stress-strain curve, densification strain and energy absorption effects of various specimens with various porosities. Furthermore, the thermal conductivity of the aluminum foams is determined, and the results compared with some theoretical predictions. The optimum parameters for meeting some tendentious and practical design requirements, such as those of impact absorption and thermal insulation design applications, are discussed. Finally, an empirical correlation between normalized yield strength and relative densities is obtained .