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A prototype software system that automatically designs the gating and runner systems, which comprise the feed system, of injection molds is described. The system, called AMDS (Automated Mold Design System), integrates CAE, with iterative redesign and knowledge stored in a features representation of the part. Gating design involves the generation of the best gating configuration represented by number, location, and type of gates, and the determination of the best conditions under which plastic should enter through the gates. Runner design also involves the generation of a runner layout followed by the sizing of the runner segments. The design of both systems is iterative, whereby the design variables are changed, the new design analyzed, evaluated, and redesigned if necessary, until an acceptable design is obtained. The evaluation of the gating design is based on eighteen performance parameters, while the evaluation of the runner system is based on four performance parameters. The system has been tested on three-dimensional parts made up of planar rectangular wall features with holes as add-on features.

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Cotterell and Mai and their co-workers [1][2][3][4] have determined the specific essential work of fracture (We) in ductile materials by utilizing geometrically confined specimens in which the size of the outer plastic zone is proportional to the square of the initial ligament length z. They distinguished the inner fracture process zone and outer plastic deformation region and interpreted the inner fracture process zone as the necked region [4] in the path of the crack comprising essential work of fracture. By extrapolating the straight line relationship between the total specific work of fracture Wf(=Wf/t ~ where Wf is the total work of fracture; t is the thickness; ~is. the initial ligament length) and the initial ligament length z down to zero ligament, they obtained the specific essential work of fracture We from the intercept.Recently, we have reported [5][6][7][8] that the resistance to crack initiation and growth can be determined utilizing the locus line of a set of characteristic points on load-displacement curves of specimens which differ only in initial crack size fromwhere R is the resistance to crack growth; B is the specimen thickness; a is the initial crack length; Ur is the area enclosed by a loading curve, the locus line along the characteristic points, and the displacement axis as shown in Fig. 1. The characteristic points can be any points of interest such as the crack initiation points, the points at which the sane amount of crack growth c occurs, the maximum load points, or the fast rupture points. We also reported [8] that the crack-resistance Rm at the maximum load point of load-displacement curve can have similar values for different initial crack sizes when the R-curve of the specimen has a transition in the slope as shown schematically in Fig. 2. Since the maximum load point on a displacement-controlled load-displacement curve occurs at the tengential point between the corresponding constant-load crack-driving force line and theR-curve, Rm for different initial crack sizes can have similar values if the tangential points for different initial crack sizes occur nearby each other on the R-curve.When the inner processing zone and the outer plastic region can be distinguished as in the case considered by Cotterell et al., the R-curve may reflect Int Journ of Fracture 42 (1990)