Cutting force model and damage formation mechanism in milling of 70wt%Si/Al composite

High-mass fraction silicon aluminium composite(Si/Al composite) has unique properties of high specific strength, low thermal expansion coefficient, excellent wear resistance and weldability. It has attracted many applications in terms of radar communication, aerospace and automobile industry. However, rapid tool wear resulted from high cutting force and hard abrasion, and damaged machined surfaces are the main problem in machining Si/Al composite. This work aims to reveal the mechanisms of milling-induced damages of 70wt% Si/Al composites. A cutting force analytical model considering the characteristics of both the primary silicon particles and the cutting-edge radius was established. Milling experiments were conducted to verify the validity of the model. The results show that the analytical model exhibits a good consistency with the experimental results, and the error is about 10%. The cutting-edge radius has significant effects on the cutting force, surface roughness and damage formation. With the increase in the cutting-edge radius, both the cutting force and the surface roughness decrease firstly and then increase. When the cutting-edge radius is 27 μm, the surface roughness(Sa) reaches the minimum of 2.3 μm.Milling-induced surface damages mainly contain cracks, pits, scratches, matrix coating and burrs.The damage formation is dominated by the failure mode of primary silicon particles, which includes compressive breakage, intragranular fracture, particle pull-out, and interface debonding. In addition, the high ductility of aluminium matrix leads to matrix coating. This work provides guidance for tool selection and damage inhibition in high-efficiency and high-precision machining of high mass fraction Si/Al composites.

Fiber-reinforced composites in milling and grinding:machining bottlenecks and advanced strategies

Fiber-reinforced composites have become the preferred material in the fields of aviation and aerospace because of their high-strength performance in unit weight.The composite components are manufactured by near netshape and only require finishing operations to achieve final dimensional and assembly tolerances.Milling and grinding arise as the preferred choices because of their precision processing.Nevertheless,given their laminated,anisotropic,and heterogeneous nature,these materials are considered difficult-to-machine.As undesirable results and challenging breakthroughs,the surface damage and integrity of these materials is a research hotspot with important engineering significance.This review summarizes an up-to-date progress of the damage formation mechanisms and suppression strategies in milling and grinding for the fiber-reinforced composites reported in the literature.First,the formation mechanisms of milling damage,including delamination,burr,and tear,are analyzed.Second,the grinding mechanisms,covering material removal mechanism,thermal mechanical behavior,surface integrity,and damage,are discussed.Third,suppression strategies are reviewed systematically from the aspects of advanced cutting tools and technologies,including ultrasonic vibration-assisted machining,cryogenic cooling,minimum quantity lubrication(MQL),and tool optimization design.Ultrasonic vibration shows the greatest advantage of restraining machining force,which can be reduced by approximately 60%compared with conventional machining.Cryogenic cooling is the most effective method to reduce temperature with a maximum reduction of approximately 60%.MQL shows its advantages in terms of reducing friction coefficient,force,temperature,and tool wear.Finally,research gaps and future exploration directions are prospected,giving researchers opportunity to deepen specific aspects and explore new area for achieving high precision surface machining of fiber-reinforced composites.