Wear of Diamond-impregnated Bit in Drilling Engineering Ceramic
This paper describes experimental results using a scanning electron microscope (SEM) to observe the face of diamond-impregnated bit after its drilling engineering ceramic. Wear patterns and mechanisms were analyzed. The results show that several diamond wear patterns are found in the bit face including complete crystal shape, micro fragmentation, extensive fragmentation, whole fragmentation, wearing flat and particle shattered, bond abrasion mainly is in the form of shifting sand pattern, alternating thermal stress and mechanical stress are the main reasons which lead to the diamond wear, extrusion force, friction as well as abrasive debris erosion result in the shifting sand pattern of the bond.
Performances of Diamond Impregnated Bit in Hole Drilling of Engineering Ceramics
According to the mechanical characteristics of engineering ceramics,the special diamond impregnated bits are developed for hole drilling.The cutting performances of the bits are analyzed from the following aspects,such as bit wear,working life,machining efficiency and machining quality.The results show that: the whole bit wear process can be divided into three phases;the regularity of the machining time per hole with the number of holes machined is close to a periodic variation;higher machining efficiency or working life can be obtained when the drilling pressure and the wall thickness of the bit are advisable.Aiming at the drilling defects in engineering ceramics,drilling with compressive pre-stress is proposed.Experimental results show that the bit is suitable for the drilling of engineering ceramics.Research achievements provide technical bases for the application of diamond impregnated bits in hole drilling of engineering ceramics.
Flexural strength of creep feed ground ceramics: general pattern, ductile-brittle transition and mlp modeling
Three ceramic materials including two aluminas and one silicon nitride were ground under various creep feed conditions. Flexural strengths of the ground specimens were measured by four-point bending. The experimental data indicates a general flexural strength pattern consisted of three regimes as a function of mean unit load and grit depth of cut (or mean chip cross-sectional area). Defining ductile-brittle transition as the point where strength starts to degrade, it is found that the transition occurs at higher mean unit load, grit depth of cut, or mean chip cross-sectional area for the lower strength material. The percentage of fractured area is found not to be a good indicator of strength for alumina materials. The multi-layer perceptron (MLP) neural network is proposed to establish the strength model. The general form of the MLP-based strength models as well as the fitted parameters are given. The implications of the study are discussed with respect to past studies.