Study Of Surface Integrity Research Articles

A Study of Surface Integrity in WEDM-HS with Air Medium

In wire electro-discharge machining with high traveling speed(WEDM-HS), the emulsion is used as working liquid. Because there exists a functional electrolyte, this affects the surface quality of workpiece machined. An investigation has been made into the machining feasibility when the gas or air is employed as processing medium. The first cut on workpiece is done with emulsion, and then air or distilled water is used for the second cut and multi-cuts. After machining, the surface quality and mechanical performance of the specimen under different conditions are compared. The experimental results show that air and distilled water have little influence on the surface roughness, but they can improve the mechanical performance such as the increase of hardness and the decrease of surface cracks. An orthogonal design is adopted to optimize the electric parameters and cutting passes so as to obtain the best integrative result. The experiment with air as medium reveals that it is a feasible and effective way for eliminating the electrolytic layer and improving the surface integrity of workpiece.

Study of surface integrity using the small area EDM process with a copper–tungsten electrode

Abstract The present study performs the small area electro-discharge machining (EDM) process with a low wear-rate copper–tungsten electrode of diameter 1.5 mm to establish the influence of the EDM parameters on various aspects of the surface integrity of AISI 1045 carbon steel. The residual stress induced by the EDM process is measured using the Hole-Drilling Strain-Gage Method. The experimental results reveal that the values of material removal rate (MRR), surface roughness (SR), hole enlargement (HE), average white layer thickness (WLT), and induced residual stress tend to increase at higher values of pulse current and pulse-on duration. However, for an extended pulse-on duration, it is noted that the MRR, SR, and surface crack density all decrease. Furthermore, the results indicate that obvious cracks are always evident in thicker white layers. A smaller pulse current (i.e. 1 A) tends to increase the surface crack density, while a prolonged pulse-on duration (i.e. 23 μs) widens the opening degree of the surface crack, thereby reducing the surface crack density. The EDM hole drilling process induces a compressive residual stress within the workpiece. A linear relationship is identified between the maximum residual stress and the average white layer thickness. It is determined that the residual stress can be controlled effectively by specifying an appropriate pulse-on duration.

Investigation of surface integrity in high speed end milling of a low alloyed steel

Understanding the effects of cutting speed, feed rate and cutting depth on surface integrity is very important for the control of workpiece quality. This paper presents a global experimental study of surface integrity in the case of high speed end milling. In the global term, we include measurements of residual stresses, surface roughness and cutting forces. Our observations and conclusions are mainly concentrated on the effect of depth of cut with a set of constant parameters, such as cutting speed, feed rate, and tool/material couple. This set of constants has been determined using the theory of stability lobes. All experiments have been performed with an electro-spindle equipped with magnetic bearings. The results lead to a good understanding of the influence of cutting conditions on surface integrity in high speed milling of a low alloyed steel. The discussion examines a specific point where the residual stress and residual stress gradient are lowest and also the origin of the residual stress value.

High Efficiency Deep Grinding of a Low Alloy Steel with Plated CBN Wheels

High efficiency deep grinding (HEDG) of a low alloy steel (51CrV4) has been carried out on an Edgetek 5-axis CNC grinding machine, using electroplated CBN wheels. The initial tests were conducted in a surface grinding mode over a wide range of grinding conditions, to evaluate the levels of specific grinding energy, workpiece surface integrity and wheel wear. The burn threshold conditions for the ground workpiece surface have been proposed in terms of a critical heat flux which is shown to vary with material removal rate. Cylindrical grinding in HEDG mode has also been carried out based on the knowledge obtained from the surface grinding. It has shown that the HEDG technology can be transferred successfully to the field of cylindrical grinding to achieve very high specific material removal rates in excess of 400mm 3/mm.s. The successful application of HEDG to cylindrical components depends on the appropriate selection of grinding parameters and also the grinding fluid supply strategy. Thermal modelling of the HEDG process combined with surface integrity studies, has shown that under cylindrical grinding conditions a significant reduction in grinding fluid supply is possible even when operating within the HEDG regime.

Surface integrity studies on shot-peened thermal-treated En 24 steel spur gears

En 24 steel spur gears in untreated and thermal-treated conditions with and without shot peening were tested in a back-to-back gear test rig. Surface finish at the pitch region and wear loss were monitored. Surface integrity studies and ferrographic analysis of wear debris enabled the interpretation of failure. The surface deterioration was less pronounced in the case of shot-peened gears and further they exhibited good steady-state wear characteristics compared to unpeened gears.

Surface integrity studies on the grinding, lapping and polishing processes for optical products

This paper reports on studies carried out on aspherical and spherical surfaces on silicon, silicon carbide and glass. Industrial specimens were subject to grinding (better known as milling in optical industries), lapping, and polishing processes. Laboratory work consisted of grinding and polishing with glass and silicon, and fine grinding only with silicon carbide. These processes were individually evaluated for surface integrity, residual stresses, and sub-surface damage. The instrumentation used were surface testers with 10 nm accuracy (Form Talysurf), X-ray stress analyser (Rigaku), and a scanning electron microscope (Cambridge).

Wear behaviour of disc type roller cutter for tunnel boring machine: Wei, K.J. Proc. Conf. Wear of Materials 1991, Vol. II, Orlando, Florida, USA, Apr. 1991 pp 683–688

Boring Trepanning Association (BTA) drills are capable of machining holes, having large length-to-diameter ratios, in a single pass. This is a unique self-piloted operation in which cutting and burnishing are carried out at the same time. A study of surface integrity, which comprises surface topography and subsurface metallurgy on machined and burnished layers of the work sample in BTA drilling, would reveal quite useful information regarding the performance of BTA drills. Surface integrity is also useful in understanding the functional behaviour of the manufactured part, namely wear, friction etc.This paper deals with surface integrity studies on En — 9 steel samples machined using a BTA drill under different machining conditions. The study includes the analysis of scanning electron micrographs, surface profiles and the variations in microhardness and residual stress on machined and burnished layers with different machining conditions.

Investigations into surface topography, microhardness and residual stress in Boring Trepanning Association machining

Boring Trepanning Association (BTA) drills are capable of machining holes, having large length-to-diameter ratios, in a single pass. This is a unique self-piloted operation in which cutting and burnishing are carried out at the same time. A study of surface integrity, which comprises surface topography and subsurface metallurgy on machined and burnished layers of the work sample in BTA drilling, would reveal quite useful information regarding the performance of BTA drills. Surface integrity is also useful in understanding the functional behaviour of the manufactured part, namely wear, friction etc. This paper deals with surface integrity studies on En — 9 steel samples machined using a BTA drill under different machining conditions. The study includes the analysis of scanning electron micrographs, surface profiles and the variations in microhardness and residual stress on machined and burnished layers with different machining conditions.

A Study of the Ballizing Process

The ballizing process which involves the forcing of a precision ground tungsten carbide ball of a prescribed diameter through a slightly undersized hole, is a relatively new microfinishing process. Though ballizing equipment have been commercialised, very few reports on the process have been published; of these is the one by Prokuryakov et al. In the present study of low speed ballizing, tungsten carbide balls of various diameters were used on brass, aluminium and steel specimens. Surface finish, roundness and forces were measured. With the large volume of data collected, multiple linear regression techniques were used and empirical relationships were established. Optical and scanning electron microscopy were used for surface integrity studies.