Prabhat Ranjan

Development of chemo-mechanical magnetorheological finishing process for super finishing of copper alloy

Nano finishing is an emerging field of manufacturing science, which imparts a high level of surface smoothness, wherein surface roughness lies in range of the nanometeric scale (0.1 to 100 nm). Nano finishing is needed to improve the functional quality of various products such as biomedical implants, laser optics, etc. Recently, a hybrid finishing process viz. chemo-mechanical magnetorheological finishing (CMMRF), has been developed for single crystal silicon. This process is capable for generating sub-nanometric finish (0.5 nm) on a planner silicon surface. In this paper, CMMRF process is used to carry out super finishing of metals and alloys. The process is studied, analysed and optimised to get a better surface finish on the copper alloy and the results are compared with the results of CMMRF on silicon (monocrystalline as well as polycrystalline).

Modelling and simulation of chemo-mechanical magnetorheological finishing (CMMRF) process

Nano–finishing is one of the emerging fields in the area of manufacturing. In the present era, nano–finished components are being developed by two different ways, i.e. soft loop as well as hard loop process; whereas soft loop process is widely used in industries. Recently, a novel nano–finishing process has been developed by combination of magnetorheological finishing (MRF) and chemo mechanical polishing (CMP), which is named as chemo–mechanical magnetorheological finishing (CMMRF) process. CMMRF process has been developed for nanofinishing of silicon and copper. Finishing parameters of CMMRF have not been studied theoretically. It is identified that the polishing pressure is a key factor of soft loop process. Hence, an analytical approach has been taken to study polishing pressure in CMMRF. In this work, a mathematical model has been developed to understand the finishing mechanism and to investigate polishing pressure with other controlling parameters. The model has been simulated and subsequently validated using experimentation.

Effects of the condition of the tubular electrode on hole size and shape in micro deep hole electrical discharge machining

An attempt has been made to find out the effects of the electrode condition on the micro drilled deep holes with electrical discharge machining process. With optimised machining parameters for copper electrode–brass work material combination, experiments were carried out with different electrode conditions viz. straight, tilted and bent electrodes. The objective was to find out the signatures of these electrode conditions on the size and shape of the hole obtained from the experimental results. Based on the results a geometrical model is constructed and presented.

Investigations into the mechanism of material removal and surface modification at atomic scale on stainless steel using molecular dynamics simulation

Abstract A molecular dynamics simulation (MDS) has been carried out to investigate the material removal phenomenon of chemo-mechanical magnetorheological finishing (CMMRF) process. To understand the role of chemical assisted mechanical abrasion in CMMRF process, material removal phenomenon is subdivided into three different stages. In the first stage, new atomic bonds viz. Fe–O–Si is created on the surface of the workpiece (stainless steel). The second stage deals with the rupture of parent bonds like Fe–Fe on the workpiece. In the final stage, removal of material from the surface in the form of dislodged debris (cluster of atoms) takes place. Effects of process parameters like abrasive particles, depth of penetration and initial surface condition on finishing force, potential energy (towards secondary phenomenon such as chemical instability of the finished surface) and material removal at atomic scale have been investigated. It was observed that the type of abrasive particle is one of the important parameters to produce atomically smooth surface. Experiments were also conducted as per the MDS to generate defect-free and sub-nanometre-level finished surface (Ra value better than 0.2 nm). The experimental results reasonably agree well with the simulation results.

Analysis, design and synthesis of water-based magnetorheological fluid for CMMRF process

Abstract A computational fluid dynamics (CFD) simulation has been performed to study the instability behaviour of water-based magnetorheological fluid (MR fluid) which is being used as a polishing medium of the chemo-mechanical magnetorheological finishing (CMMRF) process. This article deals with the flow behaviour of the dispersed solid phase in a continuous liquid phase due to the gravity-assisted flow, which results in sedimentation of the MR fluid with time. In the present work, the causes of the fluid sedimentation have been identified through the CFD simulation. The sedimentation effect is minimized by nano-coating on iron particles using hydrocarbon chains through chemical reaction which is studied and analysed by using ab initio molecular dynamics simulation through density functional theory (DFT). The phenomenon observed through the simulation work is experimentally validated. The experimental results show that the MR fluid with nano-coating yields better stability against sedimentation.

Tool Condition Monitoring in Microturning of Aluminium Alloy Using Multiple Sensors

In the present work, an attempt has been made to monitor the tool condition status during microturning of aluminium alloy (AA 6061) using multiple sensors such as cutting force dynamometer, acoustic emission (AE) and accelerometer. The tool wear (nose wear) is correlated with surface roughness (Ra), chip width, thrust force (Fx), tangential force (Fy), feed force (Fz), AERMS and vibration signals. It is observed that Ra, chip width and cutting forces are increased with increase in the tool wear. Among the cutting forces, the tangential force (Fy) is found to be more sensitive to the tool wear status compared to that of the thrust force (Fx) and feed force (Fz). From the signal analysis, it is observed that during machining with good tool condition, the dominant frequency of the AERMS and vibration signals are found to be 81 kHz-110 kHz and 2.07 kHz-3.84 kHz respectively, whereas with the worn out tool the dominant frequencies are shifted to higher levels. Chip morphological studies indicated that favourable type of chips are formed upto 40th minute and unfavourable chips are observed from 41st minute to 60th minute.