Development of decision support knowledge based system for tool wear diagnosis

This paper deals with the problems faced by small and medium sized metal cutting industries, with the perspective of tool monitoring. In a small or medium size metal cutting industry employing major metal cutting process, one of the primary problem is that of tool monitoring and wear diagnosis. The problem is of immediate concern especially in those industries where the processes or operations employed are flexible and production depends entirely on orders from customers. Due to a flexible manufacturing setup, almost all major metal cutting processers need to be carried out. However, it becomes increasingly difficult for such small or medium size metal cutting industries to employ skilled manpower for each operation as well as expert technicians to supervise the operation, and carry out fault diagnosis and tool monitoring. Also, the problem associated with tool monitoring is that human operator carrying out the monitoring has to rely either on observation such as ceasing of tool, rise in temperature, generation of fumes, noisy operation, vibrations, considerable change in shape etc, or by monitoring the quality of the finished product. Also, there can be instances where the operator does notice a symptom but does not have the expertise to identify the cause of the trouble. Errors in tool monitoring can lead to considerable damage both to the machine as well as the workpiece. On the other hand, if the tool is replaced before it reaches its useful life expectancy, it leads to unnecessary additional cost. A Decision Support Knowledge Based System (DSKBS) has therefore been developed in this paper with the above considerations. The DSKBS provides the user with a friendly environment to diagnose a particular tool wear and obtain the necessary repair or replacement instructions. The goal is to increase productivity, decrease cost of operation and enhance total quality and reliability of the operation.     

An ergonomic shoulder for robot-aided rehabilitation with hybrid control

Microsystem Technologies - Over the past years, robot-aided rehabilitation has gained traction to regain lost mobility in upper limb due to stroke. In most cases, rehabilitative robotic devices...     

Non-parametric rain/no rain screening method for satellite-borne passive microwave radiometers at 19–85 GHz channels with the Random Forests algorithm

This paper presents a novel non-parametric pattern recognition method to screen rain/no rain status for satellite-borne passive microwave radiometers in the 19–85 GHz channels. The method is based on randomized decision trees with bootstrap aggregation (Random Forests (RF) algorithm). It relies on pragmatic associations between the input features using Tropical Rainfall Measuring Mission (TRMM) Microwave Imager (TMI) calibrated brightness temperatures and precipitation radar (PR) rain/no rain information as targets. Both these instruments are carried on board the TRMM satellite. In order to develop the method, first, the 10 most significant input features are selected by using feature importance criteria through out-of-bag (OOB) statistics from a total of 17 input features. The input features include the brightness temperatures, as well as some computed signatures – polarization differences (PD), polarization-corrected temperatures (PCT), and scattering indices (SI) at in the 19–85 GHz channels. The feature selection is carried out for different types of surface terrain (ocean, land, and coast), and the selected features are then used for final RF algorithm development. During the dichotomous statistical assessment of the method against the PR rain/no rain status as ‘truth’, the presented method produced reasonable threat scores of 0.50, 0.43, and 0.39, respectively, over ocean, land, and coast surface terrains. Furthermore, the results are compared with the dichotomous scores derived by the Goddard profiling algorithm (GPROF) and, remarkably, the RF-based method corroborated better statistical scores than that of the GPROF. The presented method does not rely on any a priori information and is applicable to other passive microwave radiometers at similar frequencies.     

Fracture behaviour,microstructure, and performance of various layered-structured Al2O3-TiC-WC-Co composites

In this study, layered-structured Al₂O₃-based composites containing WC-Co, TiC, and MgO additives were prepared using hot-pressing sintering. The best comprehensive mechanical characteristics were acquired for the sample with a layer number (N_LN) of 7 and thickness ratio (η_TR) of 6. Its composite exhibited a fracture toughness of 8.5 and 8.4 MPa m^1/2 in the X and Z directions, respectively. Analysis of the micro characteristics of the fracture surfaces of the Al₂O₃-TiC-WC-Co layered composites revealed a significant enhancement in the bending strength, which could be attributed to the mixed fracture modes in the composite, including intergranular and trans-granular modes. As the displacement increased, first, the bending stress of all the composites increased gradually, after which all the samples showed abrupt elevation in stress. The enhancement in the damage resistance of Al₂O₃-TiC-WC-Co layered composites could be attributed to the microscopic and macroscopic crack deflection, bridging, and partial surface bonding that occurred in the layers. Finally, a new theoretical perspective was employed to discuss the mechanism of the effect of the layered structure on the toughness of the composites.     

Surface tension of Nanofluid-type fuels containing suspended nanomaterials

ABSTRACT: The surface tension of ethanol and n-decane based nanofluid fuels containing suspended aluminum (Al), aluminum oxide (Al2O3), and boron (B) nanoparticles as well as dispersible multi-wall carbon nanotubes (MWCNTs) were measured using the pendant drop method by solving the Young-Laplace equation. The effects of nanoparticle concentration, size and the presence of a dispersing agent (surfactant) on surface tension were determined. The results show that surface tension increases both with particle concentration (above a critical concentration) and particle size for all cases. This is because the Van der Waals force between particles at the liquid/gas interface increases surface free energy and thus increases surface tension. At low particle concentrations, however, addition of particles has little influence on surface tension because of the large distance between particles. An exception is when a surfactant was used or when (MWCNTs) was involved. For such cases, the surface tension decreases compared to the pure base fluid. The hypothesis is the polymer groups attached to (MWCNTs) and the surfactant layer between a particle and the surround fluid increases the electrostatic force between particles and thus reduce surface energy and surface tension.     

Laser Clad and HVOF-Sprayed Stellite 6 Coating in Chlorine-Rich Environment with KCl at 700 °C

Laser clads and HVOF coatings from a stellite 6 alloy (Co–Cr–W–C alloy) on 304 stainless steel substrates were exposed both bare and with KCl deposits in 500 ppm HCl with 5% O₂ for 250 h at 700 °C. SEM/EDX and PXRD analyses with Rietveld refinement were used for assessment of the attack and for analysis of the scales. The bare samples suffered from scale spallation and the scale was mostly composed of Cr₂O₃, CoCr₂O₄ and CoO, although due to dilution haematite (Fe₂O₃) was detected in the scale formed on the laser clad sample. A small amount of hydrated HCl was detected in bare samples. While the corrosion of the bare surfaces was limited to comparatively shallow depths and manifested by η and M₇C₃ carbide formation, the presence of KCl on the surface led to severe Cr depletion from the HVOF coating (to 1 wt%). Both inward and outward diffusion of elements occurred in the HVOF coating resulting in Kirdendall voids at the coating–steel interface. The laser clad sample performed significantly better in conditions of the KCl-deposit-induced corrosion. In addition to the oxides, CoCl₂ was detected in the HVOF sample and K₃CrO₄ was detected in the laser clad sample. Thermodynamic calculations and kinetic simulations were carried out to interpret the oxidation and diffusion behaviours of coatings.