| Summary: | 碩士 === 國立交通大學 === 機械工程系 === 88 === Composite clad rods that are composed of two or more different materials being used extensive in the industry because of their excellent mechanical characteristics. However, owing to the different properties of the constituent materials, it is very often encountered various defects during extrusion process.
In this study, the fracture of the core of the composite clad rods is our major object. We present a numerical simulation model based on the upper-bound theorem to analyze the core of composite clad rods in extrusion. Beside a normal three-dimensional admissible velocity fields that dictates the normal deformation of core and sleeve, an extra velocity fields depicts the necking of core is superimposed on this normal velocity fields. Both of the normal and the extra velocity fields are derived under the condition of incompressibility of materials or the constant volume flow. One pseudo-parameter was added on the extra velocity fields, while the total energy consumptions are subjected to minimization. If the result shows that a non-extra velocity fields exist, then we concluded core fracture would happen. Use the proposed criterion, combination of working parameters sound extrusion are established.
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