A hybrid genetic algorithm for solving a layout problem in the fashion industry.

As of this writing, many success stories exist yet of powerful genetic algorithms (GAs) in the field of constraint optimisation. In this paper, a hybrid, intelligent genetic algorithm will be developed for solving a cutting layout problem in the Belgian fashion industry. In an initial section, an existing LP formulation of the cutting problem is briefly summarised and is used in further paragraphs as the core design of our GA. Through an initial attempt of rendering the algorithm as universal as possible, it was conceived a threefold genetic enhancement had to be carried out that reduces the size of the active solution space. The GA is therefore rebuilt using intelligent genetic operators, carrying out a local optimisation and applying a heuristic feasibility operator. Powerful computational results are achieved for a variety of problem cases that outperform any existing LP model yet developed.Fashion; Industry;

Microstructural engineering of functionally graded materials by electrophoretic deposition

An important challenge in the design and processing of engineering materials is to combine irreconcilable properties of materials, such as hardness and toughness, in the same component. A possible concept to meet this demand is that of functionally graded materials (FGMs). The main feature of a graded material is the position-dependant composition and related mechanical properties. Electrophoretic deposition (EPD) is a fairly rapid low cost process, capable of producing such FGMs with complex geometry. This paper reports on processing of homogeneous as well as continuously graded ceramic-ceramic (ZrO2-Al2O3) and ceramic-metal composites (WC-Co) by means of EPD. The EPD characteristics of the constituent powders, such as the point of zero charge (pzc), the natural pH, the electrophoretic mobility, the effective particle charge and the resistance of the suspension are experimentally determined. The EPD processing parameters are described and the mechanical properties of the densified FGM composites are reported and evaluated. A model for the EPD process has been developed which enables to calculate the composition gradient in the FGM material from the starting composition of the suspensions, the EPD operating parameters and the powder-specific EPD characteristics. (C) 2003 Elsevier Science B.V. All rights reserved.status: publishe

Electrophoretic shaping of functionally graded hardmetals

status: publishe

Functionally graded WC-Co materials produced by electrophoretic deposition

Functionally graded WC-Co materials can be fabricated using electrophoretic deposition from a suspension of hard metal powder in acetone, with variable cobalt content. The deposits can be sintered to closed porosity at 1290 and 1340 degreesC. The cobalt gradient disappears if sintering is carried out at 1400 degreesC. (C) 2001 Published by Elsevier Science Ltd. on behalf of Acta Materialia Inc.status: publishe

Gradient profile prediction in functionally graded materials processed by electrophoretic deposition

Electrophoretic deposition (EPD) allows the formation of plate-shaped binary functionally graded materials (FGM) by depositing from a powder suspension to which a second suspension is continuously added during the process. The deposition yield is described as a function of time and starting composition of both suspensions, resulting in a model of the EPD process that allows predicting the composition gradient in the green deposit as well as in the sintered material. The model presented enables calculation of the composition gradient in the FGM material from the starting composition of the suspensions, the EPD operating parameters and the powder-specific EPD characteristics. The powder-specific parameters, i.e. the effective charge, the electrophoretic mobility, the specific conductivity of the intermicellar liquid and the specific resistance of the deposit, incorporated in the model were experimentally determined from EPD of the individual homogeneous powder suspensions. The model was verified for the ZrO2-Al2O3 system by the actual preparation and analysis of two different FGM materials. Because of the excellent correlation between the predicted and the measured concentration profiles, the described model allows to precisely engineer and design the composition profile in FGM materials produced by EPD. (C) 2003 Acta Materialia Ltd Published by Elsevier Ltd. All rights reserved.status: publishe

A hybrid genetic algorithm for solving a layout problem in the fashion industry

As of this writing, many success stories exist yet of powerful genetic algorithms (GAs) in the field of constraint optimisation. In this paper, a hybrid, intelligent genetic algorithm will be developed for solving a cutting layout problem in the Belgian fashion industry. In an initial section, an existing LP formulation of the cutting problem is briefly summarised and is used in further paragraphs as the core design of our GA. Through an initial attempt of rendering the algorithm as universal as possible, it was conceived a threefold genetic enhancement had to be carried out that reduces the size of the active solution space. The GA is therefore rebuilt using intelligent genetic operators, carrying out a local optimisation and applying a heuristic feasibility operator. Powerful computational results are achieved for a variety of problem cases that outperform any existing LP model yet developed.status: publishe

Functionally graded ZrO2-WC composites processed by electrophoretic deposition

This paper reports on the processing of homogeneous as well as graded ZrO2-WC composites by means of electrophoretic deposition. The EPD characteristics of the constituent powders, such as the point of zero charge, the natural pH and the electrophoretic mobility are experimentally determined and reported. The EPD processing parameters are described and the mechanical properties of the densified homogeneous and FGM composites are reported and evaluated. Moreover, the deposition yield in the FGM material is described as a function of time and starting composition of the suspensions, resulting in a model of the EPD process that allows to predict the composition gradient in the sintered material. The presented model enables to calculate the composition gradient in the ZrO2-WC FGM material from the starting composition of the suspensions, the EPD operating parameters and the powder-specific EPD characteristics.status: publishe

Functionally graded ceramic and ceramic-metal composites shaped by electrophoretic deposition

Because of the increasing interest in colloidal processing methods for shaping advanced technical ceramics and hardmetals, the potential of electrophoretic deposition as a shaping process is investigated. The mechanisms of deposition, which have been proposed in literature, and the relation between the evolution of the current, yield and the electric field strength are evaluated. Special attention is given to the electrophoretic characteristics of the constituent powders, such as the point of zero charge, the natural pH, the electrophoretic mobility; the effective particle charge and the resistance of the suspension.. The investigated materials comprise alumina, zirconia and their composites as well as various formulations of hardmetals. The fabrication of homogeneous as well as continuously graded plate-shaped components is highlighted. The main feature of a functionally graded material (FGM) is the position-dependant composition and related mechanical properties. Moreover, a mathematical model of the EPD process for FGMs is presented that allows to predict the composition and slope of the gradient in the sintered material from the starting composition of the suspensions, the EPD process parameters and the powder specific EPD characteristics. The correlation between the experimental results and the predicted gradient profile is excellent. (C) 2003 Elsevier Science B.V. All rights reserved.status: publishe

Processing of hardmetal coatings on steel substrates

The possibility to coat steel substrates with a WC-Co hardmetal coating by means of electrophoretic deposition and subsequent microwave heating is reported. A fully densified coating with a final thickness up to 200 pm was achieved. Vickers hardness measurements revealed a difference of 600 Hv between the bulk material and the coating. (C) 2003 Acta Materialia Inc. Published by Elsevier Science Ltd. All rights reserved.status: publishe

Thick plate-shaped Al2O3/ZrO2 composites with continuous gradient processed by electrophoretic deposition

This paper concerns the processing of free standing objects with a gradient composition. The possibility to shape 5 mm thick ZrO2-Al2O3 FGM discs by means of electrophoretic deposition (EPD) from suitable stable suspensions was explored. The EPD processing parameters and sintering schedules are described, and the densified FGM composites are evaluated. A mathematical model was established for the EPD process, allowing to calculate the composition gradient in plate-shaped FGM materials from the starting composition of the suspensions, the EPD operating parameters and the powder specific EPD characteristics. The model was essential to engineer the gradient profiles in the green deposits. Defect free Al2O3/ZrO2 FGM discs with a diameter of 55 mm, and a thickness of 5 mm could be successfully processed.status: publishe