基于CFD的高速切削层流模拟

 高速切削塑性变形的本质是位错的不可逆运动与增殖,切削时固体的黏滞力与位错速度成正比,材料的黏性效应在材料的动态力学行为中起到越来越重要的作用,因此从流体的角度去理解比从固体的方面去认识更符合其特点。本文描述了高速切削的位错阻尼机理,建立了基于流体力学的高速切削理论模型,利用计算机模拟技术得到了高速切削时的速度场、压力场和应变率场,为高速切削研究提供了新的思路。通过分析计算结果得出如下结论:在刀尖上方存在速度滞止点,此处速度为零,压力最大,其位置变化影响着刀具寿命和工件已加工表面的质量;从压力最大点开始,压力值沿前刀面逐渐减小直到某处为零,此点即切屑与前刀面分离点;剪切面(刀尖与自由表面拐角处连线)上应变率最大,然后由此向外依次减小。

Laminar Flow Analog for High Speed Machining Based on CFD

In high speed metal cutting, the irreversible dislocation motion and multiplication result in the plastic deformation of the metal, and its velocity are proportional to the drag force of the solid. Therefore, the effect of viscosity becomes more and more important in describing the material dynamic behavior. The damping mechanism of dislocation in high speed metal cutting is described from the fluid aspect; a model for high speed machining is established based on fluid mechanics. The velocity distribution, the pressure distribution and the strain rate distribution are calculated by solving the Navier-Stokes equation and energy equation, which provides a new method to study high speed machining. Analytical results show that approximating the behavior of metal cutting by a fluid model during high speed machining is not irrelevant. A speed stagnation point is located at some distance from the tool tip on the tool rake face on which the maximum value of the pressure occurs, with zero speed. Its location influences the life of the tool and the quality of the finished surface. The pressure decreases along the rake face and reaches zero at some point away from the tool tip, which is the point of separation of the chip from the tool. The value of the strain rate exhibits a rapid increase from the tool tip to the free surface corner, and then decreases outwards.