tailieunhanh - Handbook of Advanced Ceramics Machining Episode 2

Tham khảo tài liệu 'handbook of advanced ceramics machining episode 2', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | 16 Handbook of Advanced Ceramics Machining 2 f max R dc yc R dc yc If dc dc yc 2 1 the equation is simplified as dh 19 This model is useful since it acknowledges the occurrence of the cracks in the cutting zone or the zone to be cut and the effectiveness of reducing the machining energy. However it is difficult to predict the crack path and to control its growth rate. In the final finishing the available alternative for feed rate fmax dc as if concerning the crack growth and its penetration depth. Eda et 13 have developed a new ultraprecision machine with an actuator capable of controlling the specific material removal within the condition fmax dc with which the surface roughness of subnanometer was achieved for a wide range of materials. The grinding energy required for ductile mode is different from that for brittle mode. Based on the concept of the critical depth-of-cut dc which has attracted considerable attention so far a general description has been successfully introduced to express the brittle-ductile relationship. The total grinding energy Eb required for brittle materials is the sum of the energy for brittle grinding Ef and the energy for ductile grinding Ep. Out of Eb Ef is expressed as Ef 2pCl7s 2Cm s p aSpdp L where CL is the lateral crack radius L the length of CL cylinder gs the energy for surface generation Cm the median crack radius Sp the yield stress dp the diameter of plastic flow zone and a a constant whereas Ep is Ep FtL 1 11 where Ft is the tangential grinding force and L the grinding length. Dividing this by the removed volume Vf at the brittle mode or Vp at the ductile mode the specific grinding energy mf and mp are given as m Ef Vf Kfd -4 Kp mp Ep Vp SY H Kp As grinding shifts from the brittle mode to the perfect ductile mode the specific energy for brittle grinding mf should agree with the condition Sp s sf shown in Figure and the specific energy for ductile grinding mp should take a value equivalent to .