切削加工表面变质层厚度的图像识别技术

Evaluation of Thickness of Machined Surface Deformation Layer with Image Processing Technology

切削加工表面变质层影响零件的物理力学性能,会引起表面残余应力分布、显微硬度和微观组织结构等表面完整性的改变,进而影响零件疲劳寿命等服役性能.利用MATLAB图像处理工具,对切削加工表面变质层进行图像识别,探讨预分析图像质量对变质层厚度分析结果的影响,判定切削表面变质层与基体的边界,测量加工表面变质层的厚度.对镍基高温合金GH4169、粉末高温合金FGH95高速切削加工表面变质层分别进行了图像识别和变质层厚度的确定.结果表明:采用图像处理方法能正确识别加工表面基体和变质层的相含量差别,得到加工表面变质层深度,可用于加工表面完整性的检测.研究同时表明:图像亮度、纹理度、对比度和清晰度均会对变质层厚度分析结果产生较大影响,而图像色彩饱和度和尺寸大小的差异对变质层厚度分析结果影响较小.

In metal cutting, the state of a part＇s surface deformation layer is crucial for mechanical and physical prop- erties of machined workpiece, which influences the modification of surface integrity such as distribution of residual stress, microhardness and microstructure. As a result, the machined surface layer has a great effect on service perform- ance of the part. A image processing tool MATLAB was employed to recognize the machined surface deformation layer in this paper. The effect of the pre-analysis image quality on the recognition of deformation layer thickness was also investigated. The boundary of machined surface deformation layer and bulk was identified, and then the thickness of deformation layer was measured. The image processing and thickness measurement were carried out on the GH4169 and FGH95 machined surface deformation layer. The results show that image processing method can cor- rectly identify the difference of phase content between the machined surface deformation layer and the substrate; the depth of machined surface deformation layer can also be obtained. Thus, it can be used for the detection of surface integrity. The study also shows that the image brightness, texture, contrast, and sharpness all have a great impact on the analysis results of machined surface deformation layer thickness, while the image color saturation and size differences have little effects on the machined surface deformation layer thickness.