Analysis of machining process and thermal conditions during vibration-assisted cortical bone drilling based on generated bone chip morphologies

Direct approach for bone fracture treatment usually involves restoring the fractured parts to their initial position and immobilizing them with plates, screws and wires. This approach needs a bone surgery drilling to produce hole for screw insertion. But this drilling process causes mechanical damages, i.e microcracks, burr formation and delamination, that can reduce the stability of the fixation. One of the ways to minimize it is by using coolant. Moreover, it is noted that bone has anisotropic microstucture. The object of this study is to understand the effect of coolant on mechanical damages that occur in bone drilling and to understand the effect of microstructure difference on microcracks that occur in the drilled walls holes. Adult bovine bones and adult goat bones were used in this study as the specimens to represent differences in cortical bone microstructure. Five consecutive holes from the distal to the proximal in each specimen were generated using manual hand-drill (spindle speed (n) = 1000 rpm; drill bit (d) = 4 mm diameter) with the use of coolant as variation. The drilling holes then stained and observed using a microscope. As the result, it was found that the use of coolant can significantly reduce the drilling temperature. Microcracks, burr formation and delamination were found to be quite large in the drilling holes without coolant. However, there is no microcrack found in the drilling holes with coolant, there is only a small number of burr formation was found. In addition, it was found that the differences in bone microstructure affect the number and length of microcracks that occur in the wall of the hole. It can be concluded from this study that the application of coolant is very effective to reduce the drilling temperature and enhancing the quality of the hole generated by bone drilling and the higher the density of osteon in cortical bone, the easier the microcrack to initiate and propagate.

Download Full-text

Modern Approach to Delivery Coolants, Lubricants and Antiadhesives in the Environmentally Friendly Grinding Processes

International Journal of Precision Engineering and Manufacturing-Green Technology ◽

10.1007/s40684-020-00270-y ◽

2020 ◽

Author(s):

Krzysztof Nadolny ◽

Seweryn Kieraś ◽

Paweł Sutowski

Keyword(s):

Physical State ◽

Hybrid Methods ◽

Environmentally Friendly ◽

Thermal Conditions ◽

Machining Process ◽

Modern Trend ◽

Machining Processes ◽

Modern Approach ◽

Effective Delivery ◽

Cooling And Lubrication

Abstract Control of thermal conditions in the grinding zone is possible through effective delivery of substances with cooling, lubricating and antiadhesive properties during the machining process. In addition to the benefits of coolants, however, a number of economic and ecological problems arise, which include the costs of purchase, use and maintenance as well as the environmental impact of its disposal. These negative aspects of the use of cooling and lubricating liquids have contributed to the modern trend of minimizing their output in machining processes, including grinding. This article presents comprehensive characteristics of knowledge in the field of liquids, gases and solids with cooling, lubricating and antiadhesive properties. The author’s original classification of cooling and lubricating agents by their physical state was proposed and a complete list of known modern environmentally friendly methods of cooling and lubrication of the grinding zone was presented. In order to highlight their beneficial features, the background of conventional methods of delivery coolants, lubricants and antiadhesives to the grinding zone used for years were also characterised. A comprehensive list of all known methods of cooling and lubrication of the grinding zone classified according to the physical state of the delivered medium with a clear separation of hybrid methods consisting in simultaneous delivery of many cooling and lubricating agents was described in the summary. The article concludes with the characteristics of directions of further development in the field of cooling and lubrication of the grinding zone.

Download Full-text