Knowledge of the settling behavior of solid particles through fluids is of significant importance for petroleum, mining, pharmaceutical and process engineering operations. The particles involved in most of the applications are observed to be irregularly shaped, which incidentally changes their settling behavior vis-à-vis smooth and symmetrical particles. The fluid medium—drilling fluid, polymer fluid, and clay slurry—through which the particles settle is often found to be non-Newtonian and this phenomenon is of importance to many industrial applications.

In this context, the first paper, “An Experimental Study of Settling Velocity in Turbulence Using the Digital Particle Image Velocimetry Technique”, presents the findings of a study carried out by the authors, Manoj Kumar, Jyoti Raman and Priya, to examine the settling behavior of various types of particles that are a few millimeters in size and slightly heavier than water in the turbulent field generated by a grid oscillating in the vertical direction. The authors have used Digital Particle Image Velocimetry (DPIV) with enhanced shadow processing function to carry out simultaneous velocity measurements of individual fine sand particles driven by gravity and the ambient fluid in the confined turbulent environment at different oscillating frequencies. The relative settling velocity was found to be generally smaller than the still water terminal velocity. The authors, however, opined that the reduced settling velocity cannot be simply correlated to turbulence intensity or other dimensionless parameters including the Stokes number. According to the authors, the prime findings of the study are: one, the turbulence decays followed the power law; and two, the integral length scale increases linearly with the distance from the grid. The authors have also found that shear flow perceptibility exists near the vertically oscillating grid while homogeneity of the turbulence can only be found at a distance from the oscillating grid.

Over half of the materials used in the aerospace industry are said to be nickel-based alloys. They are under constant improvement for bettering their strength and surface integrity. The authors, Panditrao S M, Patil T S, Soman A A, Achara U J and Shinde S N of the paper, “An Analysis of Surface Integrity of Machined Inconel-718”, have investigated the effect of cutting speed, feed rate and depth of cut on surface roughness, microstructure of machined part and tool wear in dry rough turning of Ni superalloy and Inconel-718, using PVD coated (TiAIN + TiN) carbide tool inserts. The results indicate that a low surface roughness of 0.61 µm can be achieved with 60 m/min cutting speed, 0.05 mm/rev feed and 0.25 mm depth of cut, while a high surface roughness value of 1.06 µm can be achieved with 40 m/min cutting speed, 0.01 mm/rev feed and 0.5 mm depth of cut. Similarly, the studies carried out to monitor tool wear revealed that a minimum tool wear of 0.12 mm was observed with 40 m/min cutting speed, 0.05 mm/rev feed and 0.25 mm depth of cut, while maximum tool wear of 0.25 mm was noticed with cutting speed of 60 m/min, 0.01 mm/rev speed and 0.5 mm depth of cut. Further, the authors have suggested that cutting speed of 60 m/min, feed rate of 0.05 mm/rev and depth of cut of 0.5 mm were optimum for producing best cutting results for PVD coated carbide tool inserts.

With the increased volume and variety of production, maintenance of production facilities has gained greater importance. In this context, Computerized Maintenance Management Information System (CMMIS) has emerged as an advanced tool to manage the maintenance efficiency and effectiveness of industrial establishments. Against this backdrop, the authors, Himanshu Arha, Paramjeet Yadav, Anshul Singhwal, Nishtha Saini and P C Tewari of the paper, “Development of Computerized Maintenance Management Information System for Rico Industries, Gurgaon”, developed CMMIS with C Sharp as front end and SQL server as back end for Rico Industries, Gurgaon. The CMMIS developed by them included modules such as equipment details, tools and spares, preventive maintenance schedules, maintenance staff and safety records, condition monitoring techniques and calibration and root cause analysis and feedback. Its adaption, according to the authors, reduces maintenance and inventory cost.

Metal Matrix Composites (MMCs) are a class of advanced materials which have been developed for weight-critical applications in the aerospace industry. Silicon nitride and graphite, the ceramic materials, are used in the fabrication of particulate MMCs. The authors, Pardeep Sharma, Dinesh Khanduja and Satpal Sharma, of the paper, “The Effect of Milling Time on Density and Microstructural Characterization of Si3N4/Gr Ceramic Powder”, have synthesized silicon nitride and graphite alloyed powder by using ball mill and evaluated the effect of milling time on morphology and the density of the alloy. Their findings revealed that with milling time density increased initially but then started decreasing—density at the start of the milling process was 2.83 g/cm3, which increased to 2.86 g/cm3 at 25 hours and later declined to 2.81 g/cm3 at 100 hours of milling. They have also concluded that ball milling results in proper mixing of powders that yields homogeneous microstructure and density.

GRK Murty
Consulting Editor