Optimisation
The Bevelled AnvilIt has been found though multiple studies that adding a bevel to the edge of the working face - i.e. decreasing the sharpness of the corner - will provide better support and thus allow the anvil to produce higher pressures within the sample before it fails. Introducing a smaller angle of departure from the sample and gasket reduces the corner where the stresses concentrate, allowing the sapphire to support higher pressures. A bevel also helps to direct the gasket flow meaning it can provide better lateral support to the anvil face under working conditions. However, if the angle of departure is too small then gasket flow will be restricted creating large shear stresses around the anvil face. It has been found for standard cut diamonds that a bevel of 8-9 degrees gives optimum working conditions.
The sapphire ball bearings used for this study are essentially bevelled already at an angle of 16 degrees from the gasket due to their spherical nature. Decreasing the bevel angle for this geometry will significantly decrease the bulk of the material, thus, reducing the bulk support it provides. Further simulations will be run to determine whether or not increasing the departure angle will indeed improve the spherical sapphire anvil. If so, attempt will be made to find the optimum angle of departure which finds a balance between allowing better gasket flow without restriction while not decreasing the bulk support of the sapphire too much. |
Preliminary Results
The graph opposite proves firstly that adding a bevel to the sapphire ball bearing can improve its anvil operability - i.e. allowing it to provide higher pressures in the sample before failure. Secondly the data obtained suggests that the is an optimum angle of departure between 11-15 degrees. |
The graph opposite suggests that there could be an optimum angle of departure of between 6-9 degrees. Here it is assumed the gasket it well directed while flowing without being restricted. |