高强度钢45CrNiMoVA流变本构方程研究

本文以45CrNiMoVA材料为研究对象,通过准静态扭转实验和正交切削实验相结合的方法建立了反映切削加工过程中应变硬化效应、应变率硬化效应和热软化效应的Johnson-Cook材料本构模型,在低应变率范围内采用扭转试验的方法来获得材料本构模型的系数,使用正交切削实验来获得高应变率条件下的材料模型系数。

陶瓷生坯边位压裂纹的产生与扩展规律

为揭示陶瓷生坯切削加工过程中的材料去除机理及其裂纹扩展特性,利用冷等静压成型技术制备出氧化铝陶瓷生坯,通过边缘位压试验研究切屑成型、裂纹产生和扩展规律。结果表明:在较小位压宽度时,切屑形成主要为压碎方式,载荷波动相对较小;在较大位压宽度时,主要是由裂纹扩展而形成的大块切屑为主,载荷存在规律性波动。裂纹扩展路径受刀具楔角和印压厚度的影响,在较小刀具楔角时(≤35°),裂纹主要沿着圆弧扩展,当刀具楔角增大时(≥45°),裂纹扩展路径先沿直线扩展后沿圆弧扩展到表面;切屑长度随着印压宽度的增大逐渐增大,但印压宽度≥1.5mm时,切屑长度与印压宽度的比例关系基本维持在1.6左右。

Chip Formation in Micro-cutting

The miniaturisation context leads to the rise of micro-machining processes. Micro-milling is one of the most flexible and fast of them. Although it is based on the same principles as macro-cutting, it is not a simple scaling-down of it. This down-sizing involves new phenomena in the chip formation, such as the minimum chip thickness below which no chip is formed. This paper presents a review of the current state of the art in this field from an experimental and a numerical point of view. A 2D finite element model is then developed to study the influence of the depth of cut on the chip formation. After the model validation in macro-cutting, it highlights the phenomena reported in literature and allows to perform a minimum chip thickness estimation.