靜水壓擠製為一不同於傳統擠製的金屬成形方法，其主要特徵在於利用液體將壓力均勻的施加於擠製錠上，而非直接利用擠桿施加壓力。擠製錠周邊的壓力於模具出口處較入口處低，利用此壓力差使得金屬流動。
複合包芯材是指由兩種或兩種以上不同機械性質的材料所組成的複合材。在製造複合包芯材方面，由於靜水壓擠製比傳統擠製更能使得製品變形均勻，因此為製造複合包芯材之最有效方法之一。
本論文擬利用液動潤滑理論，配合極限解析中的上界法，建立一靜水壓擠製之數學模式，並用來分析複合包芯材在靜水壓擠製過程中的種種變形情形。本研究首先利用建立出的數學模式分析複合包芯材流經圓錐狀模所需之負荷，並且考慮非線性應變硬化對加工荷重能量造成的影響。再透過解析檢討在不同的加工條件下，複合包芯材的變形行為，最後以實驗來印證本研究所提之解析模式的可靠度。
Hydrostatic extrusion is an extrusion process where the billet is completely immersed in pressurized liquid. Pressure at the die orifice is lower than that at the die entrance, and the resulting pressure differentialcauses metal flow, the force required to push the billet through the die thus is provided by the hydrostatic pressure instead of direct ram force.
Composite rods or wire can be composed of two or more different materials, and each material has its own distinctive mechanical characteristics. Because a composite rod billet is deformed more uniformly in the hydrostatic extrusion process than in the conventional extrusion, it is considered hydrostatic extrusion is one of the most effective processes for manufacturing of composite rods and wires.
The aim of this thesis is to propose an analytic model for hydrostatic extrusion process. In this model the liquid surround the billet will be considered to be one kind of hydrodynamic lubrication and upper-bound theorem will be adopted for the analysis of the deformation of composite rods or wire. Model describing the plastic flow of the above mentioned clad rods was established. Work-hardening effects of the materials are taken into account.The results show the deformation behaviors of billets under hydrostatic extrusion with different processing parameters. Finally an experiment of the hydrostatic extrusion of round rod was conduced, and its results were found very close with the analysis.