- 學位論文
金屬正交切削切屑幾何和形成之有限元素模擬
Finite element simulation of chip geometry and formation in orthogonal metal cutting
摘要
本論文係利用有限元素分析軟體ANSYS/LS-DYNA建立一套金屬正交切削過程之模擬分析模型，同時探討切屑形成時的應力、應變等物理量的變化，以助於瞭解金屬正交切削過成切屑的形成機構。分析模型採用Johnson and Cook的材料構成方程式來描述含碳量0.18%低碳鋼材料的行為，並且採用元素破壞產生的切屑剝離準則作為未變形之切屑是否自工件剝離而形成切屑的判斷準則。此模型經分析所得之切削力分佈趨勢與大小和文獻所提供的切削力實驗值相當接近，故可知本研究所建立的模型在定性上是合理的。 研究結果顯示，最大的等效塑性應變值產生在刀具-切屑接觸面，其原因為摩擦所造成；最大的等效應力值發生在主要變形區裡，顯示切削過程的變形產生在主要變形區；切屑剪切平面之剪切角會隨著切削速度的增加而增加，此些結果與切削理論相符。
並列摘要
In this research the finite element analysis software ANSYS/LS-DYNA is used to establish a set of simulation analysis model of a process of a set of metals orthogonal cutting. The physical quantity such as the stresses and the strains can be understood when the chip is formed; this is useful for the enhancing the dimensional accuracy and he improvement of the production. The “Johnson and Cook” formulation used in the analysis model is used to describe the behavior of the 0.18%mild steel material and the chip separate criterion is used to be the criterion of the element fracture if the undeformed chip separate from the workpiece to form the chip. The tendency of distribution of the cutting forces is very close to the experimental value from the reference, so the model established in this research is reasonable qualitatively. The results show that the largest effective plastic strain is caused in the surface of the tool-chip because of the friction. This shows that the caused deformation is in the primary deformation zone and the largest effective stress is caused in the primary deformation zone. The shear angle in the shear plane will crease with the cutting velocity. The results accord with the theory of cutting.