Criterion of Core Fracture by Deviation-Velocity for Composite Clad Rod in Extrusion

• Main Authors: Yu-Kai Lin, 林裕凱
• Other Authors: 徐瑞坤
• Format: Others
• Language: zh-TW
• Published: 2001
• Online Access: http://ndltd.ncl.edu.tw/handle/99886267284818540944

碩士 === 國立交通大學 === 機械工程系 === 89 === The composite clad rod is a rod composed of two or more materials. It is applied extensively in industry because of its outstanding mechanical characteristics. However, when subject to extrusion the composite clad rod tend to develop non-uniform deformation because of these differences in materials’ mechanical properties. In certain cases, core fracture appears. The main object of this thesis is to investigate the criterion of core fracture for composite clad rod in extrusion. Upper-bound method was adopted for the analysis with a kinematically admissible velocity field to simulate the core and the sleeve’s uniform deformation under sound process parameter combinations, while a deviation-velocity field simulates the radial flow of core material. These two velocity fields are combined together with a designed variable applied to the deviation velocity component. When the total minimized power of extrusion indicates an existence of deviation velocity component, the initiation of the core fracture is deemed positive to occur. With this criterion for core fracture established, the extrusion work designed variable combinations is systematically investigated, and the work limit diagram for the composite clad rod in extrusion can be constructed.