Raj Das’s research while affiliated with RMIT University and other places

This paper investigates the damage mechanisms of 3D needled C/SiC composites through finite element method analysis and orthogonal turning experiments using polycrystalline diamond (PCD) tools. The results show that material can be removed in a fragmented manner due to its brittleness. The SiC ceramic matrix fractures earlier than the carbon fibers, leading to cracks along the fiber-reinforcement direction and machining surface defects that are primarily characterized by matrix cracking, fiber fracture, fiber pull-out, and microcracks. Chips resulting from the fracture of carbon fiber bundles are typically elongated and flat, whereas those containing SiC ceramic matrix are irregularly block-shaped, with cracks present on their surface. The optimized turning parameters were found to be – a spindle speed of 200 r/min, a feed rate of 0.15 mm/r, and a cutting depth of 0.1 mm, which led to a 50.38% increase in material removal rate compared to current turning process parameters.

Aero-engines, the core of air travel, rely on advanced high strength-toughness alloys (THSAs) such as titanium alloys, nickel-based superalloys, intermetallics, and ultra-high strength steel. The precision of cutting techniques is crucial for the manufacture of key components, including blades, discs, shafts, and gears. However, machining THSAs pose significant challenges, including high cutting forces and temperatures, which lead to rapid tool wear, reduced efficiency, and compromised surface integrity. This review thoroughly explores the current landscape and future directions of cutting techniques for THSAs in aero-engines. It examines the principles, mechanisms, and benefits of energy-assisted cutting technologies like laser-assisted machining and cryogenic cooling. The review assesses various tool preparation methods, their effects on tool performance, and strategies for precise shape and surface integrity control. It also outlines intelligent monitoring technologies for machining process status, covering aspects such as tool wear, surface roughness, and chatter, contributing to intelligent manufacturing. Additionally, it highlights emerging trends and potential future developments, including multi-energy assisted cutting mechanisms, advanced cutting tools, and collaborative control of structure shape and surface integrity, alongside intelligent monitoring software and hardware. This review serves as a reference for achieving efficient and high-quality manufacturing of THSAs in aero-engines.

The intermittent cutting behavior, performing as periodic contact phase and separation phase between abrasive grit and workpiece, is an important characteristic in the ultrasonic vibration-assisted grinding (UVAG). This study investigated the effect of intermittent cutting behavior on the grinding force in UVAG. At first, a grinding force model was established by determining the quantity of effective grits and the grinding force of a single grit. Then, the influences of ultrasonic vibration phase on the intermittent cutting behavior and grinding force were discussed. Finally, the prediction accuracy of the model was tested through experiments. Results indicated that the intermittent cutting behavior was divided into the contact phase and separation phase. A large unchanged chip thickness of 1.05 μm was generated at the start of contact phase. The quantity of effective grits firstly increased to maximum 232 at the vibration phase of 0.5 π and then gradually decreased to zero when entering the separation phase. The maximum error of the grinding force model was 15%, indicating that the model was of high accuracy for the force prediction in UVAG.

The intermittent cutting behavior, performing as periodic contact phase and separation phase between abrasive grit and workpiece, is an important characteristic in the ultrasonic vibration-assisted grinding (UVAG). This study investigated the effect of intermittent cutting behavior on the grinding force in UVAG. At first, a grinding force model was established by determining the quantity of effective grits and the grinding force of a single grit. Then the influences of ultrasonic vibration phase on the intermittent cutting behavior and grinding force were discussed. Finally, the prediction accuracy of the model was tested through experiments. Results indicated that the quantity of effective grits, unchanged chip thickness and proportion of grits at the sliding, plowing, cutting stages were all changed with the vibration phase. A large unchanged chip thickness and 56% effective grits at the cutting stage were generated at the start of the grits-wheel contact phase. Then, the quantity of effective grits firstly increased to maximum 232 at the vibration phase of 0.5π and then decreased to zero when entering the grits-wheel separation phase. The maximum error of the grinding force model was 15%, indicating that the model was of high accuracy for the force prediction in UVAG.