Bone Abrasive Machining: Influence of Tool Geometry and Cortical Bone Anisotropic Structure on Crack Propagation

Abstract

The abrasive machining of cortical tissue is used in many arthroplasties and craniofacial surgery procedures. However, this method requires further research due to the processes’ complexity and the tissue’s composite structure. Therefore, studies were carried out to assess the impact of grid geometry and the anisotropic structure of bone tissue on the cutting process and crack propagation. The analysis was performed based on an orthogonal cutting in three directions. The grain shape has been simplified, and the cutting forces, crack path and surface quality were monitored. The results indicate that a depth of cut at 100–25 µm allows the most accurate cutting control. A transverse cutting direction results in the greatest surface irregularity: Iz = 17.7%, Vvc = 3.29 mL/m2 and df = 5.22 µm and generates the most uncontrolled cracks. Maximum fracture force values of FF > 80 N were generated for d = 175 µm. For d < 5 µm, no cracks or only slight penetration occurs. A positive γ provides greater repeatability and crack control. Negative γ generates penetrating cracks and uncontrolled material damage. The individual types of cracks have a characteristic course of changes in Fx. The clearance angle did not affect the crack propagation.

The Influence of Osteon Orientation on Surface Topography Parameters after Machining of Cortical Bone Tissue

“…According to recent studies, the Young's modulus of the osteon, interstitial matrix, and cement line is 20, 21.87, and 7.4 GPa, respectively [47]. These differences affect the nature of crack propagation, as confirmed by studies such as those by Bai et al [8] and Zawadzki and Talar [46].…”

“…The cutting depth of 25 μm was chosen based on previous experimental studies—this value provides the highest sensitivity to the influence of osteon orientation, minimizing disturbances caused by crack propagation [ 46 ]. To reduce the influence of thermal effects on the cutting process, a constant cutting speed of v c = 30 mm/min was maintained, which research has shown to prevent thermal necrosis at speeds below this value [ 11 ].…”

“…The strongest but less frequent cracks are observed for the transverse direction. According to the observations of Zawadzki and Talar [46], the freedom of delamination of osteons for cutting in the parallel direction may cause an increased depth of cutting when the material cracks along the cement lines without significant resistance. Comparing the parameters of the 2D roughness profiles (see Figure 7), one can notice the similarity with crack propagation (see Figure 6).…”

Towards Metrology 4.0 in Dimensional Measurements

“…In this regard, there have also been very significant developments in recent years. In addition to the standard applications of surface topography measurements derived from tribology and related to plateau honed surfaces [44] or plasticity index [45], biotribological applications [46], primarily related to activities carried out on the human body, are increasingly appearing.…”