Experimental investigations on effects of frequency in ultrasonically-assisted end-milling of AISI 316L: a feasibility study

The effects of frequency in ultrasonic vibration assisted milling (UVAM) with axial vibration of the cutter is investigated in this paper. A series of face-mill experiment in dry conditions were conducted on AISI 316L, an alloy of widespread use in industry. The finished surfaces roughness were studied along with basic considerations on tool wear for both conventional milling and an array of frequencies for UVAM (20–40–60 kHz) in a wide range of cutting conditions. Surface residual stresses and cross-cut metallographic slides were used to investigate the hidden effects of UVAM. Experimental results showed competitive results for both surface roughness and residual stress in UVAM when compared with conventional milling especially in the low range of frequency with similar trend for tool wear

Surface Integrity of SA508 Gr 3 Subjected to Abusive Milling Conditions

SA508 Gr 3, a bainitic forging steel employed in the fabrication of nuclear pressure vessels has been characterised after dry-milling to investigate extent of machining abuse on the surface. A detailed study of the evolution of residual stresses, microstructure, micro-hardness and roughness in relation to different milling parameters is presented. A central composite orthogonal (CCO) design of experiments (DoE) was used to generate a statistic model of the milling process. Deformation of the sub-surface layer was assessed via SEM BSE imaging. The developed statistical model is discussed aiming to illustrate availability of different cost-effective manufacturing techniques meeting the high standards required by the industry

Ultrasonically assisted machining of Titanium alloys

In this chapter we discuss the nuances of a non-conventional machining technique known as ultrasonically assisted machining, which has been used to demonstrate tractable benefits in the machining of titanium alloys. We also demonstrate how further improvements may be achieved by combining this machining technique with the well known advantages of hot machining in metals and alloys

Effect of cutting parameters and CO2 flow rate on surface integrity in milling AISI 316L steel using supercritical CO2

The machining challenges commonly experienced in the milling of stainless steels, such as the formation of built-up material on the cutting tool edge and the low thermal conductivity resulting in high heat generation within the cutting zone, require the application of a lubricating cutting fluid. Manufacturing industry traditionally uses an oil-based coolant for dissipating frictional heat and reducing chip adhesion to the cutting tool; however, this is not environmentally sustainable. In this study, a design of experiment (DoE) approach was employed to investigate the impact of feed per tooth, cutting speed, and the flow rate of supercritical carbon dioxide (scCO2) on cutting forces and surface integrity during face milling of AISI 316L. As expected, it was observed that surface residual stresses increased with an increase in the feed rate. The surface roughness remained unaffected by changes in scCO2 flow rate and variations within the range of machining parameters considered in the experimental design. ScCO2 demonstrated its potential as a sustainable coolant substitute in the industrial machining of austenitic stainless steels

Ti alloy with enhanced machinability in UAT turning

Metastable β-titanium alloys such as Ti 15V 3Al 3Cr 3Sn are of great technological interest thanks to their high fatigue strength-to-density ratio. However, their high hardness and poor machinability increase machining costs. Additionally, formation of undesirable long chips increases the machining time. To address those issues, a metastable β-titanium alloy (Ti 15V 3Al 3Cr 2Zr 0.9La) with enhanced machinability was developed to produce short chips even at low cutting speeds. A hybrid ultrasonically assisted machining technique, known to reduce cutting forces, was employed in this study. Cutting force components and surface quality of the finished work-pieces were analyzed for a range of cutting speeds in comparison with those for more traditional Ti 15V 3Al 3Cr 3Sn. The novel alloy demonstrated slightly improved machining characteristics at higher cutting speeds and is now ready for industrial applications

Surface-roughness improvement in ultrasonically assisted turning

Ultrasonically assisted machining is a hybrid technique based on superimposition of ultrasonic vibration on a movement of a cutting tool. Such vibration with relatively small amplitude - below 20 microns - changes dramatically the response of a machined material to a cutting process. As a result, a significant - in excess of 80% in turning of aerospace superalloys - reduction of average cutting forces is observed together with improvement of surface roughness. The paper presents results of analysis of the effect of ultrasonically assisted turning (UAT) on surface roughness (using a broad range of parameters) for a broad range of metals and alloys - from copper, aluminium and stainless steel to Ni- And Ti-based alloys. The effect of machining parameters for both conventional turning and UAT was investigated to provide an optimum range for each material and its relation to surface roughness

MCNP5 MODELLING OF HPGE DETECTORS FOR EFFICIENCY AND COINCIDENCE SUMMING CORRECTION EVALUATIONS IN GAMMA-RAY SPECTROMETRY.

A modelling of HPGe detectors was performed through simulation with the MCNP5 Monte Carlo code. The simulation results concerning the values of the main physical parameters of the detector are in most cases different from those provided by the manufacturer. The use of “single-line” sources allows us to suitably modify the parameter values used in the detector model. For a detector model, the simulation assesses the distribution of photopeak and total efficiency for point sources, whereas for extended sources a control volume approach allows us to determine elementary efficiency behaviours. An integration of elementary efficiencies over the entire sample volume allows us to evaluate global efficiency

MCNP5 modelling of HPGe detectors for efficiency evaluation in gamma-ray spectrometry

A modelling of HPGe detectors was performed through simulation with the MCNP5 Monte Carlo code. The simulation results concerning the values of the main physical parameters of the detector are in most cases different from those provided by the manufacturer. The use of “single-line” sources allows us to suitably modify the parameter values used in the detector model. For a detector model, the simulation assesses the distribution of photopeak and total efficiency for point sources, whereas for extended sources a control volume approach allows us to determine elementary efficiency behaviours. An integration of elementary efficiencies over the entire sample volume allows us to evaluate global efficiency

Environmentally sustainable cooling strategies in milling of SA516 : effects on surface integrity of dry, flood and MQL machining

The recent move towards ‘Environmentally Sustainable Manufacturing’ (ESM) is leading heavy industries (e.g. oil & gas, nuclear) to explore low-impact manufacturing strategies. In machining, however, most processes are still performed using traditional cooling method using flood or high pressure lubricant emulsions. These emulsions are expensive in their maintenance and disposal, and present a significant environmental concern. This novel study combines evaluations of the performance of low-impact cooling strategies, such as dry milling or minimum quantity lubrication (MQL), in the manufacture of an industrially important pressure vessel carbon steel (SA516) using coated carbide inserts. Tool wear, surface roughness, residual stress and energy consumption were measured during metal cutting trials for each strategy and then compared. Likely tool wear performance when using candidate lubricants was screened prior to machining trials using standard tribological high frequency reciprocating tests. Significant improvements in surface integrity and tool wear were observed when machining with dry and MQL when compared with traditional flood coolant. Measured energy footprints for dry and MQL were also lower when compared to flood coolant machining providing cost savings and environmental advantages in manufacturing using ESM approaches