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Metal Casting Technologies : September 2007
73 WHO'S WHO OF METALS -- ANNUAL 2007/8 3. DESIGN AND DEVELOPMENT OF EXPERT SYSTEM In conventional human approach of phase diagrams, lot of assumptions are involved and this provides a way for minor errors regarding the structure, since even small variation in the calculation would cause change in structure and composition at certain points. These kinds of minor errors can be eliminated using mathematical logical approach in C. The logic behind this can be illustrated by considering a part of iron carbon phase diagram as example. Take the austenite and liquid region and analyze how far this system implements the lever rule here by taking the carbon and temperature as input from the user. In Fig.1, X1 and X2 represents the carbon content variation at different temperatures, where X1 is the variation in the left curve and X2 is the variation in the right curve. This value varies for different temperatures but for a given temperature, X1 and X2 values are fixed. These X1 and X2 values are not entirely fed as data to the system, but their variations according to the temperature has been analyzed and a mathematical equation has been developed. Using mathematical equation, X1 and X2 values are calculated for the given temperature. This process is done under looping structures. This carbon content (X1 and X2) variation for the austenite liquid region has been analyzed and the rate of variations has been observed for different temperatures. The system takes the X1 and X2 values by making use of the equation developed. X1=0.17+ (a1*((1490-T)/10)); [Eq.1] X2=0.53+ (a2*((1490-T)/10)); [Eq.2] From the equations 1 and 2, a1 and a2 represents the range of carbon content variation of X1 and X2 respectively Figure 1. Iron carbon phase diagram - austenite liquid region