面向钛合金切削的加工界面热场测量物理重构模型及实验研究

Titanium alloy is a commonly used material for aircraft engine compressor disk because of its excellent mechanical properties and corrosion resistance. However, its low heat conductivity often results in a steep temperature gradient at the tool-chip interface during the machining process. The ability to accurately measure the peak temperature of the cutting tool and the modeling of temperature distribution near the interface in titanium alloy machining have been a well-recognized worldwide problem. In the context of dry lathe-turning of thin-walled titanium alloy, this proposal develops a method based on boundary temperature field obtained by means of non-contact infrared images to reconstruct the temperature field of the tool insert. Unlike traditional measured methods which base on limited thermocouple measurements or direct reading of absolute temperature from infrared images, the proposed method utilizes physical laws and heat transfer properties (including iso-temperature contours, temperature gradient and heat flux) to identify thermal discontinuities, separate chips from the tool insert temperature fields, and reconstruct the surface temperature of the tool insert obtruded by the chips. With the measured surface temperature as boundary conditions for solving the temperature fields in three dimensional space, the proposed research will overcome several limitations of the existing methods by providing a means to describe the steep temperature gradients at the tool-chip interface. This physics-based imaging method along with the coupled thermal-mechanical formulation based on state-space modeling will be built to efficiently model the temperature field in the entire machining interface.

钛合金材料以其比强度高、机械性能及抗蚀性能良好被当作飞机发动机核心零部件压气机盘的理想制造材料。但钛合金热导性差，切削时，在刀具-切屑融合的狭窄切削区内形成极为陡峭的温度梯度分布，其分布温度场的准确测量及建模是个世界难题。本课题以车削干切钛合金薄壁件为研究对象，以非接触式红外测得的局部温度场为基础，打破传统红外测温直接读取绝对温度场的方式，通过融入等温线、温度梯度及热流密度的热学物理模型，借助热学不连续特性对热图像的温度像素矩阵中切屑-刀具辨识分离，构建求解分布式温度的场边界条件，克服了一般研究中有限测量点无法描述急剧变化温度梯度信息的缺点。在此基础上，从热场本质出发，以温度梯度为导引，构建热-力耦合加工界面的三维热场不均匀柔性空间模型，对整个切削过程温度场实施逆向快速重构。利用远场接触式测温点的动态反馈，进化状态空间模型，获取工件实际工况下的全局温度场信息，为刀具磨损实时监控提供依据。

钛合金材料以其比强度高、机械性能及抗蚀性能良好被当作飞机发动机核心零部件压气机盘的理想制造材料。但钛合金热导性差，切削时，在刀具-切屑融合的狭窄切削区内形成极为陡峭的温度梯度分布，其分布温度场的准确测量及建模是个世界难题。本项目以车削加工钛合金材料Ti-6Al-4V过程中的温度场感知与在线监测为研究对象，建立了温度相关的改进Ti-6Al-4V材料本构模型，引入材料动态再结晶相关的温度项，揭示了高温和低温下不同的变形机理，准确反映了微观尺度下切屑-刀具加工界面热力耦合行为，实现了多工况下切削力、锯齿形切屑形态和界面热源的准确预测。在此基础上，创建了宏微结合的切削刀具温度场重构方法，包含了微观尺度下的切屑成形建模和宏观尺度下的刀具热传建模。该方法克服了传统温度传感手段无法直接测量切削区温度的难题，非接触式传感方式的采用使得该方法更具灵活性，免去了复杂且昂贵的接触式温度传感器的嵌入工艺，宏微观模型的结合和运用使得该方法能突破测量分辨率和切削位置的限制，实现对切削界面温度分布的高分辨率重构。基于此温度场离线状态下的准确重构，提出了数据驱动的刀具最高温在线监测方法。基于非接触式的红外热像仪测温手段，通过与模型数据训练的神经网络模型相结合，实现了切削过程中刀具表面和界面最高温度的高精度、高鲁棒性在线监测，计算效率满足实时性要求。