The application of computer-aided engineering (CAE), computer-aided design (CAD), and computer-aided manufacturing (CAM), is essential in modern metal forming technology. Thus, the process of modelling for the investigation and understanding of deformation mechanics has become a major concern in recent and advanced research, and the finite element method (FEM) has assumed increased importance, particularly in the modelling of deformation processes. This work is devoted to the development of a CAD/CAM system for the closed-die forging process. The system development consists of three stages: namely, metal flow simulation, die failure analysis and design optimisation, and the development and implementation of a machining code. In the first stage, the FEM was used to simulate the axisymmetric closed-die forging process of copper material. The method is used to study the metal flow; die filling, retaining the non-linearity involved in the large change in the geometry; the continuous change in the contact surface condition; and the isotropic material work-hardening characteristics. In the second stage, a finite element analysis and optimisation algorithm is developed to examine the die fatigue life and to optimise the die design. The finite element analysis in the first and second stage was carried out using commercially available finite element software called LUSAS. In the third stage, a machining code for the optimised die is developed and implemented using CAD/CAM software called UniGraphics and CNC machine. #

The ®nite element method (FEM) is employed to investigate the residual stress state and the variation of internal stresses in ST50 steel quenched from 600 to 08C. Three different geometrical shapes of model were used, namely cylinder, cone and pyramid-shaped cone. Thermal analysis is ®rst performed to obtain the cooling curves for the core and surface of the models, and this is followed by a full structural analysis. The results of the cylinder bar obtained from the computer simulation are compared with those experimentally determined values that are available in the literature and there appears to be a good measure of agreement. The study found that at the initial stages of the quenching process, the residual stresses were tensile at the surface and compressive in the core, however, towards the end of the quenching process, the tensile residual stresses switched to the core and compressive residual stresses at the surface. Under the same quenching conditions, if the models with different geometrical shape were tested, it has been found that the geometry has signi®cant effect on the distribution and the magnitudes of the residual stress. Although the cylinder and the cone were different in shapes, but the residual stress state were not much in difference. Only when the cone turn into pyramid-shaped cone, the results were different and higher values of internal residual stress. # .my (A.M.S. Hamouda).

Fuzzy rules optimization is always a problem for a complex fuzzy model. For a simple 2-inputs-1-output fuzzy model, the designer has to select the most optimum set of fuzzy rules from more than 10 000 combinations. The authors have developed fuzzy models for machinability data selection (Int. J. Flexible Autom. Integrated Manuf. 5 (1 and 2) (1997) 79). There are more than 2 Â 10 29 possible sets of rules for each model. The situation would be more complicated if there were a further increase in the number of inputs and/or outputs. The fuzzy rules (Turning Handbook of High-Efficiency Metal Cutting, General Electric Co., Detroit) were selected based on trial and error and/or intuition. Genetic optimization has been suggested in this paper to further optimize the fuzzy rules. The development of a Fuzzy Genetic Optimization algorithm is presented and discussed. An object-oriented library to handle fuzzy rules optimization with genetic optimization has been developed. The effect of constraint rules is also presented and discussed. Comparisons between the results from the optimized models and literature are made. r .my (A.M.S. Hamouda).

Optimized machinability data is obtained from a skilled machine tool operator's experience and intuition. Thus, fuzzy logic is a good approach to describe the strategy and action of the skilled operator when selecting the machinability data. In this paper, the development stages of an online fuzzy expert system (FES) are presented, possible methodologies are illustrated and their pros and cons are discussed in this paper. The FES has been developed using object oriented programing, dynamic link library (DLL) and ActiveX Control. It can be easily incorporated into the Internet and Intranet environment and can be accessed virtually at any place. A simplified fuzzy set-handling object has been developed in order to save resources. Weighted-centroid rather than union centroid is recommended in output defuzzification. Comparison between these two methods is made and discussed. # .my (A.M.S. Hamouda).

. The revolute-joint is an important component of a mechanical system. Thus, the motion simulation of multibodies connected with revolute-joints is of common interest. A simple revolute-joint can be easily represented in a numerical way, whereby the bending moment at the particular joint equals zero. Formulation becomes complicated when involving bending limits, the resistive moment and the damping effect. Furthermore, several bodies connected with revolute-joints form a complex system. This has been particularly useful for simulating a multibody system. A novel revolute-joint model is proposed in this paper. Several possible methods are suggested to handle bending limits. The incor-poration of the resistive moment and damping effects are also presented. The numerical stability of the revolute element is discussed, and a stability criterion suggested. The revolute-joint element is incorporated into an explicit finite difference code developed by the authors. Numerical examples are shown for different methods and conditions.

This review paper is devoted to discussing the development and the present state of some key aspects of the mechanical behaviour of composite materials under impact loading. The experimental techniques employed for determining the behaviour of composite materials at high strain rate in tensile, compressive and shear loading are presented and discussed. The discussion includes their fundamental advantages and limitations. Directions for future research are also indicated.

W-Beam guardrail system has been in use as a standard for roadside safety barrier since 1950s. Recently, its safety performance standard has been upgraded to absorb impact from large vehicles. This performance standard requires guardrail system to be capable of capturing and redirecting a large range of vehicle types and sizes but its effects on safety of motorcyclists are not yet understood.

Metal cutting data selection is complex and cannot be easily formulated to meet design specification by any mathematical model. Optimized Machinability data is obtained from a skilled machine tool operator's experience and intuition. A rule-based expert system and materials database have been incorporated into many CAD/CAM systems in order to obtain optimal machining parameters. Fuzzy logic is a better tool to describe the strategy and action of the skilled operator when selecting the metal cutting data. A first prototype of such a system was developed by the present authors. This paper further describes development of fuzzy models and their feasibility. Development of several models for different cutting tools is presented and discussed. The models are validated with the Machining Data Handbook. The feasibility of a generalized fuzzy model for all the cutting tools is also presented. (M.A. El Baradie) 0924-0136/99/$ -see front matter © 1999 Elsevier Science S.A. All rights reserved. PII: S 0 9 2 4 -0 1 3 6 ( 9 9 ) 0 0 1 2 7 -2

The development and implementation of an online knowledge-based system for machinability data selection is presented. Fuzzy logic has been incorporated as the reasoning mechanism behind the system. The system has been developed using object oriented programming, dynamic link library and Active-X control. It has been incorporated and tested into Internet and Intranet environment. Possible implementations of the system are suggested to work on real-world environment. A simplified fuzzy set-handling object has been developed in order to save resources. Weighted-centroid rather than union centroid has been used in output defuzzification. Comparison between these two methods is made and discussed. q

Singularities and uncertainties in arm configurations are the main problems in kinematics robot control resulting from applying robot model, a solution based on using Artificial Neural Network (ANN) is proposed here. The main idea of this approach is the use of an ANN to learn the robot system characteristics rather than having to specify an explicit robot system model.

In the present study, 1 and 2 wt.% of aluminum were successfully incorporated into magnesium based AZ31 alloy to develop new AZ41 and AZ51 alloys using the technique of disintegrated melt deposition. AZ41-Al 2 O 3 and AZ51-Al 2 O 3 nanocomposites were also successfully synthesized through the simultaneous addition of aluminum (1 and 2 wt.%, respectively) and 1.5 vol.% nano-sized alumina into AZ31 magnesium following same route. Alloy and composite samples were then subsequently hot extruded at 400 • C and characterized. Microstructural characterization studies revealed equiaxed grain structure, reasonably uniform distribution of particulate and intermetallics in the matrix and minimal porosity. Physical properties characterization revealed that addition of both aluminum and nano-sized alumina reduced the coefficient of thermal expansion of monolithic AZ31. The presence of both Al and nano-sized Al 2 O 3 particles also assisted in improving overall mechanical properties including microhardness, engineering and specific tensile strengths, ductility and work of fracture. The results suggest that these alloys and nanocomposites have significant potential in diverse engineering applications when compared to magnesium AZ31 alloy.

Libya is a rich developing country which suffers the consequences of explosions in both human and vehicle population. This has been accompanied by a heavy toll of deaths. In 1977, road accidents were the cause of IO% of all deaths and 62% of male deaths in the age group IS-25 The rates-per hundred million veh km-of fatalities, injuries and accidents (1980) were 35,202 and 416 respectively.

In the present study, new magnesium based AZ41/Al 2 O 3 -Ca and AZ51/Al 2 O 3 -Ca nanocomposites were successfully synthesized incorporating varying amount of elemental Al (1 and 2% by wt.), Ca (1 and 2% by wt.) and 1.5 vol.% nano-sized (50 nm) Al 2 O 3 particulates into AZ31 alloy using disintegrated melt deposition technique. AZ41 and AZ51 alloys were also developed following the same processing route by adding 1 and 2 wt.% Al, respectively. All alloy and composite samples were then subsequently hot extruded at 400 C and characterized. Microstructural characterization studies revealed equiaxed grain morphology, reasonably uniform distribution of nanoparticulate and intermetallics in the matrix, good interfacial integrity and minimal porosity. Addition of nano-sized Al 2 O 3 particulates and Ca into AZ41 and AZ51 samples helped to reduce the average grain size and diameter of Mg 17 Al 12 second phase and introduced (Mg, Al) 2 Ca phase in the matrix. Microhardness test results revealed that AZ51/Al 2 O 3 -2Ca samples exhibited around 47% and 90% higher microhardness value when compared to monolithic AZ51 and AZ31 samples, respectively. Room temperature tensile test results also revealed that newly developed nanocomposites exhibited superior combination of tensile properties in terms of 0.2% yield strength, ultimate tensile strength and ductility when compared to their respective alloys and some commercially available Mg alloys.