Physical modeling of extrusion process

Many metal forming processes can be simulated by using the Physical Modeling Technique which requires an inexpensive and small amount of apparatus. The underlying principle behind the Physical Modeling Technique is to simulate the actual metal forming process by selecting a model material and die geometry that closely resemble the actual metal forming process. Typical modeling materials are PLASTICINE, wax and lead while the typical die models are usually made of aluminum, wood or plexiglass.

In two-dimensional analyses, a square or circular grid pattern is printed on the surface of the specimen using ink and a grid stencil. The common method of generating the grid pattern is to use different types of PLASTICINE instead of using ink. Therefore, alternating slabs of PLASTICINE of different colors automatically form the grid patterns.

In the first phase of this study, 16 types of PLASTICINE were tested, via standard compression tests, in order to determine their flow behavior and to identify a pair with similar behavior.

In the second phase of this study, three-dimensional extrusion process was studied by using two types of PLASTICINE as a modeling material while using plexiglass as chamber and die material. The friction coefficient of PLASTICINE was obtained by utilizing the ring compression test. Analysis of deformation patterns, using the well established Physical Modeling Technique, is normally carried out by prescribing a grid pattern on the surface of modeling material.

The extrusion experiments were conducted at the three different area reductions for three different semi-cone die angles. In each case, the plastic strain distributions were determined analyzing the deformed and undeformed grids.

The main objective of this study was to simulate the three-dimensional extrusion process by using PLASTICINE as a modeling medium. Since PLASTICINE is available in 16 different colors, it became necessary to characterize the mechanical behavior of 16 different types of PLASTICINE. The objective was also to identify color pairs of PLASTICINE with similar mechanical behavior and to use these color pairs for the three-dimensional extrusion process. Furthermore, the objectives were to determine the strain distributions of plastic strain components along the diameter of an extruded product and to determine the effects of the process variables, such as area reduction and semi-cone die angle, on the required forming load.