- 學位論文
基於ANSYS/LS-DYNA的正交金屬切削切屑-刀具接觸摩擦之研究
Study of Friction at The Chip-Tool Contact for Orthogonal Metal Cutting with ANSYS/LS-DYNA
摘要
本研究應用商用有限元素分析軟體ANSYS/LS-DYNA，建立一套以Lagrange運算法為基礎，具有熱固耦合的金屬正交切削有限元素分析模型。模型中刀具材料為碳化鎢，工件材料為AISI4340鋼，且兩者材料模型均採用Johnson和Cook的動態構成方程式。建模時，刀具視為可變形體而不是剛體，此有助於了解刀具在切削過程的行為。切削剝離準則採用以材料的破壞應變值作為判斷依據的元素破壞法。 提供正確的摩擦模型是利用有限元素分析軟體模擬切削過程所必須的。本文提出一個方法決定在切屑-刀具接觸面上的摩擦。利用在切屑-刀具接觸面上的切屑應力模擬結果建立摩擦模型。將透過摩擦模型所獲得的新摩擦係數作為FEM分析模型的輸入，再利用迭代法求得正確的摩擦係數。最後論文也探討切削速度和斜角對摩擦與接觸長度，以及應力與溫度分佈的影響。
並列摘要
In this research, a commercial finite element software ANSYS/LS-DYNA is used to develop a coupled thermo-mechanical model based upon Lagrange formulation to simulate the orthogonal metal cutting processes. The materials used for cutting tool and workpiece in the model are tungsten carbide and AISI 4340 steel, respectively. Both of them are modeled by the Johnson and Cook dynamic constitutive material equation. Cutting tool is modeled as a deformable body, but not a rigid body. This will facilitate to understanding the behavior of the cutting tool while machining. The element failure law based upon a failure strain for a material is used for the chip separation criterion. It needs to provide an accurate friction model for cutting simulation using FEM based software. This paper presents a methodology to determine the friction at the chip-tool interface. Simulated results of stresses on the chip at the chip-tool interface are utilized in developing the friction model. The new friction coefficient obtained from the friction model is used as an input of the analysis model. Repeat the procedures until the correct coefficient is found. Lastly, effects of cutting velocity and rake angle on friction and contact length, as well as on the stress and temperature distributions are investigated.