Study on the effects of the machining process on porous bronze morphology via fractal dimension and pore parameters

The tortuous randomized pores inside porous bronze bring significant challenges to the machining technology and surface morphology evaluation. Additionally, some of the current measurement methods for morphology characterization can only reflect partial information about the porous surface. In this study, the cutting experiments with monocrystal diamond (MCD) tools were conducted on porous bronze to investigate the effects of machining parameters on surface morphology. Moreover, a series of image processing techniques were applied to batch-collected surface images. On this basis, before and after cutting experiments, the fractal dimensions and pore parameters were calculated to characterize and compare the changes in porous surface morphology. The experimental results indicated that the increase in cutting depth led to a larger fractal value while increased cutting speeds reduced the complexity of the machined surfaces. Among them, the cutting depth had the greatest influence on the material removal process, when the cutting depth exceeded 20 μm, the material removal process transitioned from the initial single plastic removal mode to the occurrence of brittle spalling. During the plastic removal model, the fractal dimension decreased by a maximum of 6.70 %. However, in the experimental group with brittle spalling, that value increased by 6.28 %. After processing experiments, the surface porosity of all samples ranged from 3.33 % to 12.8 %, showing a change of - 40 % to +52 % compared to the initial surface. Moreover, in this study, the fractal dimensions could provide a more comprehensive evaluation method for porous surface morphology through statistical analysis. The cutting experiments and surface morphology analysis are available to obtain the optimal machining parameters for achieving the relatively desired surface morphology.