www.lasers.org.uk

The Laser Group
at Liverpool

Lairdside Laser
Engineering Centre
Courses & Training Resources Information

Research Themes in Laser Material Processing

... being carried out by the Laser Group at the University of Liverpool
and the Lairdside Laser Engineering Centre

Laser Forming

Laser forming is a non-contact technique for the shaping of metallic sheet components.
It can be used for

rapid prototyping of complex 3D shapes

adjusting and aligning remotely of components

The mechanism of 2-D bending has been modelled using finite element analysis.
Current work is considering the laser scan parameters modeling and process control required for the formation of more complex 3-D shapes.
An example of application is in the use of laser bending to create on-board microactuators for the alignment of microelectronic components.
EPSRC GR/NL Contract Partners: University of Liverpool, Heriot - Watt University, University of Cambridge, Rolls - Royce, BAE Systems
Papers on Laser Forming
  • 3D laser forming of saddle shapes
    S.P.Edwardson,K.G.Watkins,G.Dearden,J.Magee
  • Laser Forming of Aerospace Alloys
    K. G. Watkins, S. P. Edwardson, J. Magee, G. Dearden, P. French, R. L. Cooke, J. Sidhu, N. J. Calder

 

Laser Cladding and Direct Fabrication  

 

Laser Direct Fabrication is the building of claddings or objects directly from powders using a laser for melting of the powders

Computer control of composition during laser cladding allows the whole composition range of alloy systems to be generated

 

Layer by layer deposition allows components to be deposited directly from CAD designs
Compositionally graded structures for optimised design and performance

Turbine blade

Hardness Map

Hip joint

Papers on Laser Cladding and Direct Fabrication

  • Achieving the potential of direct fabrication with lasers
    K.G.Watkins
  • Automated workstation for variable composition laser cladding - its use for rapid alloy scanning
Laser Scabbling

 

Removal of radioactively contaminated surface layers of concrete by novel laser method

Allows action at a distance so that expensive equipment is not itself contaminated during use

Can be applied with both high power CO2 and Nd:YAG lasers

Material removed by laser scabbling can be removed as high/medium level waste while the remaining structure can be classified as low level waste, hence minimising decommissioning costs

Being further investigated by BNFL as a possible means of decommissioning of nucelar installations


Concrete as received

Concrete after one pass laser scabbling

Papers on Laser Scabbling

  • Particle size analysis of material removed during CO2 laser scabbling of concrete for filtration design Lobo LM, Williams K, Johnson EP, Spencer JT
Laser Drilling

Laser percussion drilling is being developed to reduce hole formation time while maintaining hole quality

Turbine blades operate at high temperature as a result of a flow of air which produces boundary layer cooling Blades are hollow and require accurately machined holes to duct the required air flow

Mechanism of laser percussion drilling

Papers on Laser Drilling

  • Investigation of the Nd:YAG laser percussion drilling process using high speed filming

Laser Cleaning

Mechanisms of laser cleaning

 

Removal of surface particles or layers by pulsed laser radiation

Uses in art restoration, cleaning of microelectronic components, industrial cleaning

Not just one process, many mechanisms involved depending on laser fluence and pulse length

Two new mechanisms for laser cleaning


Angular laser cleaning

 


Laser shock cleaning

Papers on Cleaning

  • Two new mechanisms for laser cleaning using Nd:YAG sources
  • Ultraviolet laser removal of small metallic particles from silicon wafers
  • Effect of wavelength and incident angle in the laser removal of particles from silicon wafers
  • Chromatic modulation technique for in-line surface monitoring and diagnostic
  • A study of the effect of the wavelength in the Q-switched Nd:YAG laser cleaning of gilded wood
  • Dust Removal from Next Generation Tokamaks by Laser and Flashlamp Cleaning
  • More papers on Laser Cleaning can be found here
Laser Welding
Laser Conduction Welding of Aluminium Alloys for increased pentration

Semi-quantitative analysis of the LCW process

maximum penetration depth is produced as a result of the competition between the two processes; heat energy loss by boiling and heat transfer by conduction

At the critical spot size, when maximum penetration occurs, there is just sufficient input to maintain the surface at the boiling point. At larger sizes there is insufficient absorbed energy intensity to maintain the surface temperature at boiling. At smaller sizes excess energy causes increased boiling

Example of Laser Conduction Butt Weld

made in 3mm thick Aluminium Alloy

using YAG Laser

LC Welds show higher fracture strength than Laser Keyhole Welds in this material

Slower rates of cooling may enhance weld properties in traditionally difficult materials

Blast and Impact Resistance Studies of Laser Welded Panel Structures combining the expertise of the Laser and Impact Research Groups at the University of Liverpool

Blast testing of panel structures

FE analysis of laser welded panel

Papers on Welding

  • Laser Welding of Aluminium Alloy 5083
  • Blast and impact resistance studies of laser welded and riveted panel structures
Laser Ignition in IC Engines (LASIIC)
  • Laser ignition of air-fuel mixtures in the laboratory has shown that improved ignition and kernal growth in lean mixture may be possible, leading to an increase in the lean burn limit by 1 to 3 air-fuel ratios (AFR's) compared to conventional electric spark ignition
  • Faster burn rate is possible with higher thermal effiency
  • Reduction in peak cylinder pressure fluctuations may allow more stable combustion, more demanding lean burn strategies, lower idle speeds and better cold engine performance when compared to conventional spark plug ignition
  • LASIIC is investigating techniques for evaluating the practical feasibility of these potential advantages with realistic engineering constraints by applying laser ignition in the latest generation of vehicle test engines
  • The project is funded by the DTI / EPSRC Foresight Vehicle LINK initiative and involves a consortium comprising the University's Laser Group and IC Engines Group, Ford Motor Company and Spectron Laser Systems