Browsing by Author "Bell, Andrew John"
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Item Open Access Burn threshold prediction for high efficiency deep grinding(2011-06-01T00:00:00Z) Bell, Andrew John; Jin, T.; Stephenson, David J.Burn threshold diagrams are useful for the prediction of thermally induced grinding damage and were originally developed to describe the conventional shallow cut grinding regime. With the development of new high stock removal grinding processes such as High Efficiency Deep Grinding (HEDG), the prevention of thermal damage to the workpiece is of particular concern. The principle of HEDG is based around the change in thermal characteristics of the grinding process at high Peclet numbers, whereby less heat is partitioned to the workpiece. Conventional burn threshold diagrams are valid for Peclet numbers below 50, well below the values expected in HEDG. This study presents a modified approach to the construction of burn threshold diagrams which takes account of the change in thermal partitioning with Peclet number. The approach has been validated through grinding trials over a range of specific material removal rates.Item Open Access Temperatures in high efficiency deep grinding(Cranfield University, 2009-02) Bell, Andrew John; Stephenson, Tom; Jin, T.This research considers the temperatures generated in the workpiece during profile and cylindrical traverse grinding in the High Efficiency Deep Grinding (HEDG) regime. The HEDG regime takes large depths of cut at high wheel and workpiece speeds to create a highly efficient material removal process. This aggressive processing generates high temperatures in the contact zone between the wheel and workpiece. However, the beneficial contact angle and the rapid removal of the heated wheel – workpiece contact zone results in low temperatures in the finished surface. Temperatures in the ground surface can be predicted with knowledge of the specific grinding energy and the grinding parameters used. Specific grinding energies recorded at high specific material removal rates demonstrated a constant value of specific grinding energy dependent on cutting and contact conditions, improving accuracy of the predictive model. This was combined with a new approach to burn threshold modelling, which demonstrated an improved division of damaged and undamaged surfaces. Cutting and contact conditions in the grinding profile vary dependent on their position. This thesis shows how temperatures vary with location and estimates the partitioning of the heat flux to the regions of the grinding profile. This suggested a constant partitioning of energy to each of the three surfaces considered independently of specific material removal rates. Further a potential link was shown between the surface and the sidewall of the grinding profile, which allows temperatures in a secondary surface to be predicted given knowledge of that in the primary. Finally, the work has demonstrated the feasibility of the Superabrasive Turning process. Using small values of feed per turn and high workpiece feedrates promoted high values of removal rate with low depths of thermal penetration in the as ground surface. Thus the process has become viable for high speed cylindrical traverse grinding.