N Ramesh Babu

In this article, polished specimens are peened employing water jet pressures in the range of 100 MPa-300 MPa. The performance of peened specimens has been evaluated by examining the sliding wear, using pin-on-disc type wear testing machine. The performance of water jet peened specimens is compared with that of polished specimens in order to demonstrate the effectiveness of water jet peeningfor surface treatment.

This paper deals with the resolution of nesting algorithm, known as the irregular packing problem. It focuses on the geometric layer of the nesting algorithm, namely on the implementation of a semi-discrete representation of irregular geometric shapes and on the use of this representation in a nesting algorithm, proposed in previous publications. The proposed geometric scheme combines the features of discrete representation scheme and analytical concepts to quickly represent the geometry of part/sheet in digital form. The uniqueness of the proposed representation scheme lies in representing a part/sheet, of simple to complex geometry, with a series of equidistant vertical lines. These vertical lines not only aid in detecting collision among the parts easily but also assist in effective placement of parts on the sheet with bottom-left placement heuristic. With a view to enhance the speed of nesting, a scheme called Quick Void Skip is proposed to quickly identify the vacant regions on the sheet. For faster and effective nesting of a variety of parts on any geometry of sheet, the distance between the vertical lines, representing the part/sheet geometry, is adaptively chosen. Finally, the effectiveness of the proposed scheme is demonstrated by comparing its performance with that achieved by a semi-discrete approach, proposed in a previous study. © 2013 Copyright Taylor and Francis Group, LLC.

Producing quality features with abrasive waterjet milling requires the generation of shallow kerfs with low surface waviness. Typically, such kerfs are produced by deformation wear mode of material removal realized with certain combination of process parameters chosen based on an elaborate experimental analysis. Instead, these parameters can be selected through a modeling methodology developed based on deformation wear erosion theory. As a first part of this development, it is essential to identify the conditions for the prevalence of deformation wear during the generation of shallow kerfs with abrasive waterjets. To establish this condition, this article presents a theoretical analysis of kerf formation formulated based on deformation wear erosion by solid particles. In this analysis, the interaction of the abrasive particles with the material and the subsequent material removal through deformation wear is considered to define the geometry of the cutting front. The geometry of the cutting front was then used to determine the condition at which local impact angle of abrasives striking the cutting front changes to alter the mode of material removal from deformation wear to cutting wear. This analysis has brought out the boundary condition for deformation wear as the maximum depth of kerf to be equal to the average size of the abrasive particles used in the jet. The generic nature of this condition is established with kerfing experiments over three different ductile materials.

In this article, peening studies carried out on 6063-T6 Al alloy with high pressure water are presented. These studies have been carried out employing a round nozzle by varying the process parameters, such as, water-jet pressure, stand off distance, number of passes and traverse speed at three levels using Taguchi's L9 orthogonal array experimentation. The influence of these process parameters on residual stress, hardness and surface roughness are investigated. Finally, an empirical model, based on the mean analysis that relates the results with process parameters, is presented.

In this article, a novel ice bonded abrasive polishing (IBAP) process proposed for producing ultrafine surfaces on metallic surfaces is presented. An IBAP setup was developed for conducting the experiments under cryogenic conditions. The novelty of the process lies in the method of preparing cryogenic polishing tool by freezing the mixture of distilled water and ultrafine abrasive particles with suitable cryogenic fluids. Characterization of tool, by weight balance method, ensured uniform distribution of abrasives throughout the ice matrix. Experiments were conducted on 304L stainless steel and EC grade copper materials in order to examine the improvements in finish on polished surfaces. Experimental studies have revealed the generation of ultrafine surfaces, yielding roughness values in nanometric range, with the adhesive action of ice and abrasive action of material by fine abrasive particles. Copyright © Taylor & Francis Group, LLC.

In abrasive waterjet (AWJ) cutting system, the orifice and focusing tube undergo continuous wear due to which the quality and effectiveness of the process are affected. The present paper reports the experimental studies carried out to investigate the influence of orifice and focusing tube bore variation on the performance of abrasive waterjets in cutting 6063-T6 aluminum alloy. The performance was assessed in terms of different parameters such as depth of cut, kerf width and surface roughness. This study made use of Taguchi's design of experiments and analysis of variance (ANOVA) to analyze the performance of AWJs in cutting. These experimental data was used to build empirical models. An hybrid strategy combining the response equations of the empirical model with fuzzy model is proposed to arrive at suitable set of process parameters for achieving desired cutting performance considering the variation in orifice and focusing tube bore. The adequacy of the model is confirmed with suitable experiments. © 2006 Elsevier B.V. All rights reserved.

In this paper, a new approach proposed for modelling the three-dimensional (3D) topography produced on abrasive water jet (AWJ) cut surface is presented. It makes use of the trajectory of jet, predicted from the theory of ballistics and Bitter's theory of erosion for material removal, for numerically simulating the cutting front. The 2D topography at different depths of the cut surface is generated by considering the trajectories on the cutting front and the abrasive particles impacting the walls of cut surface randomly. For realistic generation of topography on cut surfaces, several instantaneous profiles generated in each region of cut are superimposed to obtain an effective profile. The nature of effective profiles thus predicted is analyzed and validated using power spectral density analysis. The effective profiles predicted at different depths are in turn used to generate the 3D topography of AWJ cut surface. Results obtained with the proposed model are validated with the experimental results. © 2002 Elsevier Science Ltd. All rights reserved.

In this paper, comparative studies on the effect of laser radiation on the abrasive and bond materials and preliminary investigations on the possibility of laser dressing of grinding wheels are presented. Scanning Electron Microscopy (SEM) observations of the Nd:YAG laser machined areas on Aluminium oxide (Al//2O//3) Silicon carbide (SiC) and vitrified bond showed the formation of craters and cracks inside the crater and upon the resolidified layer. More material was observed to have been removed from SiC than from the other two. This was verified from actual measurements and are in accordance with the theoretical predictions. A sample Al//2O//3 grinding wheel was dressed by laser and the resulting surface generated was observed under SEM. These observations point favourably on laser dressing of grinding wheels.

This article presents a decoupled approach for conflict free coordinated manipulation of multiple industrial robot agents operating in a typical industrial environment. Decoupled method proposed in this work plans the path for the robots in two steps. In the first step, for each participating robot agent a path collision free with respect to stationary obstacle is obtained. The coordination among agents is achieved in the second step of the approach by use of off-line strategy for conflict resolution. The key objective of the conflict resolution is dynamic assignment of priorities for path modification of the robot agents. Thus, the agents involved in a local conflict situation coordinate their movement by adopting the lowest movement cost motion paths. Results obtained from realistic simulation of multi-robot agent environment with three industrial robots demonstrate that the proposed approach assures the rapid, concurrent and conflict free coordinated motion of the robot agents. © 2009 IEEE.

This paper presents the efforts made in the design, development and characterisation of a novel method of ice bonded abrasive polishing process. Mechanisms in various types of polishing machines were studied to identify the suitable configuration for developing an ice bonded abrasive polishing setup. Initially, a setup was developed with suitable kinematics for ice bonded abrasive polishing of flat surfaces. With the experience gained with the setup, suitable modifications in the setup were made to build a new setup for effective polishing of flat metallic surfaces. The developed setup is designed to prepare the polishing tool in situ with suitable temperature controller. The novelty of polishing setup lies in the method of preparation of cryogenic polishing tool by freezing the mixture of ultrafine abrasive particles with suitable cryogenic fluids. The characterisation of tool with optical image analysis and weight balance method showed the uniform distribution of abrasives in ice matrix. Finally, the effectiveness of ice bonded abrasive polishing process was demonstrated by analysing the finish produced on flat copper specimen. © 2011 Inderscience Enterprises Ltd.