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Ceramic cubic boron nitride (CBN) wheel is widely used in grinding field for its superior grinding performance. The random grain orientation of CBN grinding wheel with ceramic bond affects its grinding performance to a certain extent. In this paper, magnetically controlled ceramic CBN grinding wheel was prepared by magnetic field and sintering process. In order to improve the magnetic conductivity of the abrasive grains, nickel-plated CBN was used to replace the abrasive particles. It was found that the direction of the abrasive particles could be effectively controlled by adjusting the strength and properties of the magnetic field, so that the abrasive particles presented a chain distribution under the magnetic field. The experimental results showed that the nickel-plated CBN abrasive grains have good orientation and chain distribution in the bond power by using alternating magnetic field. Finally, experiments were carried out to study the grinding of GH4169 with magnetically controlled ceramic CBN grinding wheel, and the experimental results were compared with common ceramic CBN grinding wheel. It was confirmed that the grinding temperature and grinding force of GH4169 with magnetically controlled ceramic CBN grinding wheel were slightly lower than that of common grinding wheel, and the grinding surface quality is better than that of ordinary grinding wheel. In this paper, the method of preparing ceramic CBN grinding wheel with controllable grain orientation was established, and the system of evaluating the grinding wheel performance was constructed. It enriched the preparation process of ceramic bond CBN grinding wheel, and would have important significance for further expanding the application of ceramic CBN grinding wheel. [ABSTRACT FROM AUTHOR]

Grinding force is an important index for understanding grinding mechanism. In this paper, based on the single grain-grinding experiment, the grinding force under different grinding parameters was studied. Based on the undeformed chip, the grinding force model of multi-grain abrasive was established. Combined with the randomness of grains distribution, the grinding force model was further improved. And the grinding specific energy under different undeformed chip thickness was obtained by single CBN abrasive grain scratch tests. In addition, grinding experiments were carried out under different grinding parameters, and corresponding grinding force was measured. The results show that the grinding specific energy changes with the change of the undeformed chip thickness. For grinding 45 steel with ceramic bond CBN wheel, when the deformation cutting thickness reaches 50 μm, the grinding specific energy tends to 3460 J/mm3. Under the same grinding parameters, the calculated values of grinding force model are in good agreement with the experimental values. Confirmed by further research, the model has better applicability to small cutting depth, slow feed, and low speed cutting models. This study has certain guiding significance for further research on grinding mechanism and characterizing the grinding force. [ABSTRACT FROM AUTHOR]

In recent years, advancements in the field of nanotechnology have actively been reflected in the manufacturing industry, particularly in the production of aviation components, ships, and medical devices. However, titanium alloys have low thermal conductivity, making them difficult to cut at high temperatures. The traditional processing method is not only inefficient but can also cause serious harm to the environment and operators. In this paper, multi-walled carbon nanotubes were used as additives to disperse into degradable vegetable oil as a green cutting fluid. This green cutting fluid was cooled to analyze the processing of a titanium alloy (LN2 + nano-MQL (0.6%)). Cutting experiments were carried out under dry, MQL, LN2, LN2 + MQL, and LN2 + nano-MQL (0.6%) conditions. The temperature of the machining area, tool wear process, tool wear mechanism, surface roughness, and surface morphology were studied. The results show that the cutting-zone temperature is reduced by 65.1%, the tool life is prolonged by 30%, and the surface roughness is reduced by 48.1% under LN2 + nano-MQL (0.6%) conditions in comparison to the dry condition. The cutting environment supported by MQL is conducive to inhibiting the formation of craters. Element detection confirmed that the tool coating was well protected under the condition of LN2 + nano-MQL (0.6%). In addition, the tool nose wear is small under the LN2 + MQL and LN2 + nano-MQL (0.6%) conditions. [ABSTRACT FROM AUTHOR]

Titanium alloys have excellent specific strength, outstanding corrosion resistance, and good biocompatibility, which are widely used in mechanical and medical fields such as compressor disc, blade, stator, and hip and knee joint. Titanium alloy workpieces must be machined to obtain specific shapes. However, the machining marks inevitably exist on the titanium alloy surface, which have a poor effect on the performance of workpieces. Therefore, polishing is scheduled at the subsequent process to remove the machining marks. Because titanium alloys are typically difficult-to-polish materials, the polishing surface quality and efficiency require to be improved further. To have an in-depth and comprehensive understanding of the polishing technology of titanium alloys, this paper reviews systematically the material's polishing mechanisms and processes. To date, various fundamental mechanisms, including mechanics, heat, optic, electricity, magnetism, ultrasound, and chemistry, are employed to polish titanium alloy surface. On this basis, four types of polishing techniques were developed (i.e., mechanical polishing, high-energy beam polishing, chemical polishing, and compound polishing) to improve the high surface integrity of titanium alloys. Furthermore, the advantages and disadvantages of each polishing technique are discussed in detail from the views of model, optimization, equipment, efficiency, surface quality, and cost. Finally, this paper proposes the future development directions of the polishing techniques of titanium alloys. [ABSTRACT FROM AUTHOR]

Laminates of carbon fibre reinforced polymer (CFRP) and titanium (Ti) alloy are used in aerospace applications and require holes for joining to other components, which can weaken them. In this study, to determine the influences of drilling and helical milling on the geometric accuracy of holes, holes were made in a CFRP/Ti-laminated structure by these two techniques, and variations in aperture and roundness at different positions were investigated. In two processes, apertures are larger in the middle and smaller at the ends, and most are larger than the apertures of standard holes (6 mm). With drilling, roundness is relatively high at hole entrances and exits. In helical milling, the maximum roundness occurs just underneath the hole entrance, while the minimum occurs at the exit. In the drilling of Ti alloy, the maximum aperture occurs at the entrance; however, with helical milling, the hole entrance aperture is smaller. The aperture at other positions is relatively small. During drilling, the maximum roundness occurs at hole entrances, while the minimum occurs just underneath and then increases with depth. Helical milling produces a relatively large roundness at hole entrances, with consistent variation in other positions. Generally, helical milling of a laminated structure produces better geometric accuracy in holes in the Ti alloy layer, better hole roundness in the CFRP layer, and smaller roundness in the transition zone. However, drilling achieves better aperture accuracy in CFRP and smaller aperture errors in the transition zone. These results will help to produce stronger CFRP/Ti-laminated structures. [ABSTRACT FROM AUTHOR]

Predicting the surface roughness of machined materials can assure shaping quality and minimize the shaping period. In this study, a milling surface roughness prediction model is proposed that considers the geometric and mechanical factors that influence surface roughness. This model considers not only elasticoplastic deformation but also the influences of cutter parameters, microhardness, cutting force, and material properties. To verify the applicability and accuracy of the model, cutting tests were carried out using orthogonal tests of a Ti alloy (Ti6Al4V). Surface roughness was measured at different feed engagements, feed rates, cutting depths, and cutting widths. The results demonstrate that the proposed model has high applicability and accuracy in predicting the milling surface roughness of Ti6Al4V, the error rate of the best result is only 3.40%, and the average error rate of each group is 10.6%. It can be used in the prediction and analysis of surface roughness after material milling in actual machining. [ABSTRACT FROM AUTHOR]

Conventional drilling is widely adopted to manufacture holes in difficult-to-cut materials such as superalloys. However, as a newer hole processing technology, helical milling possesses several advantages including low cutting forces, reduced tool wear, and improved hole quality. In this study, different hole-making processes like conventional drilling and helical milling were conducted on the superalloy (MSRR7197). Combining the deformation mechanism of the hole wall material, the influence of both hole-making processes on the processing quality of the MSRR7197 were investigated. The experimental results demonstrate that the axial force for the helical milling is about 1/10 of that for the drilling. Compared with drilling, the flank wear, rake wear, and wear of tool tip for the helical milling are smaller. The hole wall quality such as surface morphology and roughness of helical milling is better than that of the drilling. Last but not least, the helical milling can get a higher machining accuracy such as circularity and aperture. Hence, helical milling remains the favorable and alternative to conventional drilling. [ABSTRACT FROM AUTHOR]

To investigate the edge chipping during drilling of the CFRP/Ti stack with carbide cemented tools, a drilling experiment was carried out and a tool failure model was proposed. Thrust force, drilling temperature, and tool wear were analyzed. A tool stressing model and a tool failure model of edge chipping were constructed respectively. On the basis of these, the prediction model on the edge chipping was established to forecast the failure time. Drilling temperature, Vickers hardness, and cutting speed were considered during the prediction model building. The results demonstrate that adhesive wear has a great influence on the edge chipping. The damage of adhesive wear for tool rake face leads to the load variation on rake face and the initial crack. Under the action of shear stress, the crack starts at rake face and then expands to the flank face, resulting in tool edge chipping. The affinity interaction (between titanium alloy with carbide cemented) and the thermal residual stress are two critical factors for tool edge chipping. Tear easily occurs inside the binding phase or at the boundary between hard phase and binder phase. As the drilling temperature increases, the hardness of the carbide cemented will gradually decrease. The prediction result of failure time is similar to the experimental result, and the effectiveness of the prediction model is verified. [ABSTRACT FROM AUTHOR]

With the wide application of high-speed cutting technology, high-speed machining approach of titanium alloy has become one of the most effective ways to improve processing efficiency and to reduce the processing cost, but the cutting chatter which often occurs in the cutting process not only affects the machining surface quality but also reduces the production efficiency. Regenerative chatter is a typical phenomenon during actual cutting, and it has the greatest impact on the cutting process. With the purpose of avoiding regenerative chatter and selecting appropriate cutting parameters to achieve a steady cutting process and a high surface quality, it is necessary to determine the critical boundary conditions where chatter occurs. Built on the work of previous theoretical researches of regenerative chatter, this paper utilized Visual C++ software to calculate the chatter stability domain during the finish machining of titanium alloy. It was shown that the border between a stable cut and an unstable cut can be visualized in terms of the axial depth of cut as a function of the spindle speed. Using the result, it can find the specific combination of machining parameters, which lead to the maximum chatter-free material removal rate. In order to verify the result, the high-speed milling experiment of an I-shaped thin-walled workpiece made of titanium alloy was conducted. It revealed that the actual machining result was consistent with the calculation prediction. This study will offer a useful guide for effective parameter selection in future CNC machining applications. [ABSTRACT FROM AUTHOR]