STUDY OF MATERIAL REMOVAL RATE OF DIFFERENT TOOL MATERIALS DURING EDM OF H 11 STEEL AT REVERSE POLARITY
Electric Discharge Machining (EDM) is a non-traditional machining process that involved a momentary spark discharges through the fluid due to the potential difference between the electrode and the workpiece. In EDM, improper choose of the electrode material may cause poor machining rate (or) performance. This is due to material removal rate characteristics. Less material removal rate (MRR) needs more time for machining process and become waste which is not good for production. Hence in this study, the effect of input parameters of EDM process ie. electrode type, peak current, gap voltage, and duty cycle on material removal rate of H11 steel are experimentally investigated. A L18 Taguchi’s standard orthogonal array is used for experimental design. Conventional Copper (Cu) and powder metallurgy (PM) copper tungsten (CuW) are used as tool materials. It was found that conventional copper tool electrode gives maximum MRR and best parametric setting for maximum MRR was found at, Cu (99% Cu) tool electrode, 9 ampere current, 50 volts gap voltage and 0.92 duty cycle. ie. A1B2C2D3.
INFLUENCE OF ELECTRICAL PARAMETERS IN POWDER MIXED ELECRIC DISCHARGE MACHINING ( PMEDM ) OF HASTELLOY
PMEDM is a complex machining process which is controlled by a number of machining parameters. Each machining parameter has its own influence on performance of the process. The objective of this paper is to analyze the effect of electrical parameters on the performance of this process. Peak current, gap voltage, pulse on time and duty cycle are taken as machining parameters. Material removal rate, tool wear rate, % wear ratio and surface roughness are taken as response parameters to measure process performance. The experimental investigations are carried out using copper electrode. Nineteen experiments are performed on hastelloy using electronica make smart ZNC electric discharge machine tool. Variations of response parameters are plotted against input machining parameters. The study indicates that all the input machining parameters strongly affect the machining performance of hastelloy.
Neutron Residual Stress Measurements on Rail Sections for Different Production Conditions
Rail sectioning with subsequent neutron diffraction experiments has been used to assess residual stresses in the rails. In this study we present the results of neutron stress measurements performed at the NIST Center for Neutron Research (NCNR) on rail sections from rails that were produced under various conditions. Specifically, these are air-cooled, air-cooled and roller-straightened, head-hardened and head-hardened and roller-straightened. More significantly, a head-hardened and roller-straightened rail was also studied after service to elucidate evolution of the service-induced residual stresses. In the latter case both a transverse-cut slice and the central region of a 0.53 m long piece were studied. Measurements on this piece are the first in which triaxial stresses have been determined for an intact rail. Neutron strain measurements with 3×3×3 mm3 spatial resolution were successfully employed for transversally cut slices to verify the difference in the stress state depending on the production process. Although examination of slices allows determination of only two-dimensional stresses in the plane of the slice, additional measurements on obliquely-cut slices, which were also carried out, and utilization of FEM gives the possibility of reconstructing the full triaxial stress distribution. Together, these approaches provide a better understanding of rail fabrication and the possibility of improving the durability and safety of rails in the future.Copyright © 2004 by ASME