Finite Element Modeling and CAD/CAM of Nett-Forming by Injection Forging - Manufacturing Systems Processes - page 100

FIGURE 4.4 Examples of component-forms produced by injection forging.

difficult or impossible to produce by conventional cold forging were summarized in the classification
[31]. Some of these have been formed by injection forging or by combination of processes, such as,
spiders for universal joints [28, 29], the bodies for diesel injectors [32], pipe flanges [19], solid flanges
with square cross-sections [33], alternator pole parts with claws [16], and staggered branches [34]. Some
of the components formed in Manufacturing Engineering Research Center (MERC) of the University of
Strathclyde are shown in Fig. 4.4 .
Injection forging may be used to form components with radial variations in geometry. Generally, it
is possible to produce components with flanges, stepped shafts, and secondary (local) shape elements;
the shape elements can be solid or tubular, cylindrical or square cross-section, and can be incorporated
throughout the component [2]. In addition, components which may be formed by injection forging can
also contain axial variations. The combination of radial extrusion with forward and backward extrusion
has enabled the forming of such components in single stage [14-16, 19]. Some component-forms, which
had been classified with reference to axial variations of component-geometry for forming by conventional
cold forgings [30], can be formed more effectively by injection forging; nevertheless, complex tooling is
required to effect such forming. With reference to all possible variations in component-forms, compo-
nents which may be formed by injection forging may be classified by the approach depicted in Fig. 4.5 .

4.2 FEM and Applications in Metal-Forming

Design, with a view to forming flawless components which satisfy the specified performance and quality
requirements, is a universal aim. To achieve this quality of design, the design practitioner has to have a
clear appreciation of material deformation and tool behavior during forming. The analysis and design
of metal forming has been affected by the use of several process-modeling methods—analytical, numer-
ical, and experimental methods. Commonly used analytical methods are Slab, the Slip-line field, and
Upper-bound methods; numerical approaches include finite element and boundary element techniques.
Experimental methods include Physical Modeling and visioplasticity; the latter may be classified as a
“half-analytical” approach since it combines experimental and analytical techniques.
Finite-element method (FEM) was originally developed as a technique for the analysis of structures;
a number of structural elements may be analyzed as an assembly. The feasibility of applying this technique
to analyze complex structures was enhanced by the development of digital computers. The method was
subsequently extended to solve problems relating to the deformation of continua which may be subjected