钛铝合金低温切削加工温度的实验和仿真研究

Simulation and Experimental Study on Temperature in Cryogenic Cutting of Titanium Aluminum Alloy

钛铝合金具有低密度、高强度、抗氧化与抗高温蠕变等特点,在航空航天工业的应用潜力巨大,但该材料强度高,导热性能差,在切削加工中过高的切削温度导致加工效率低和表面完整性差。对材料进行了静态压缩试验和动态压缩试验,拟合了材料在-196~600℃下的本构方程;根据实际冷却条件,定义切削冷却边界,设置对流换热系数,建立了二维直角切削模型,并设计了测温刀片进行了试验验证,液氮低温冷却下的切屑形态与仿真切屑形态具有良好的一致性,试验与仿真得到的切削力和切削温度结果误差较小,说明了构建的钛铝合金低温本构方程和有限元模型具有较高的准确性,仿真得到的切削温度场也具有较高的可信性。结合仿真得到的等效塑性变形、应力场与切削温度场,进一步分析了液氮冷却切削钛铝合金的材料去除机理,发现其由周期性断裂去除向周期性断裂和绝热剪切断裂复合去除转变。

Titanium aluminum alloy has the characteristics of low density,high strength,oxidation resistance and high temperature creep resistance,and has great application potential in the aerospace industry.However,the material has high strength and poor thermal conductivity,and the high cutting temperature leads to low processing efficiency and poor surface integrity.The static compression test and dynamic compression test are conducted,and the constitutive equation of the material at−196~600°C was fitted.According to the actual cooling conditions,the cutting cooling boundary is defined,the convective heat transfer coefficient is set,and the two-dimensional right-angle cutting model is established.The cutting insert for temperature measuring is designed for experimental verification.The chip morphology under liquid nitrogen low temperature cooling is in good agreement with the simulated chip morphology.The error of cutting force and cutting temperature obtained between experiment and simulation is small,which indicates that the constructed constitutive equation and finite element model have high accuracy,and the simulated cutting temperature field also has high credibility.Combined with the equivalent plastic deformation,stress field and cutting temperature field obtained by simulation,the material removal mechanism of liquid nitrogen cooling cutting of titanium aluminum alloy is further analyzed,and it is found that it changes from periodic fracture removal to periodic fracture and adiabatic shear fracture composite removal.