Swansea University, United Kingdom
Title: Testing methodologies for thermo-mechanical fatigue evaluation in advanced aerospace materials
Biography: Mark Whittaker
Fatigue failures are common within structural components used throughout a range of industrial sectors, and are often a critical design criterion during the specification and development stage of a new product. However, most mechanical testing is performed under isothermal conditions which may not be truly representative of in service conditions. Thermo-mechanical fatigue (TMF) testing offers the opportunity for the evaluation of a range of advanced material under more appropriate thermal cycles, hence providing more appropriate lifing approaches to ensure component integrity.
TMF tests however, are complicated and difficult to perform, with much consideration necessary to understand the complex interactions of issues such as the heating/cooling method, the phase angle between thermal and mechanical strains/stresses, temperature measurement techniques and cycle frequencies.
Over the past 15 years, the Institute of Structural Materials at Swansea University has devoted significant effort in a number of developmental programmes which have led to internationally recognised expertise in experimental setup and lifing approaches. Consideration in this paper is given to the experimental difficulties associated with using traditional techniques for temperature and crack length measurements (thermocouples and direct current potential difference techniques) and the possibility of utilising more innovative approaches such as thermography is discussed. Research has shown that it is difficult to design a single solution for TMF testing due to the numerous testing requirements that include peak cycle temperature, heating/cooling rate, and the impact of electromagnetic fields associated with induction coils. As such, TMF experiments are often by their very nature, bespoke. Future developments such as the generation of a validated code of practice for crack growth measurements under TMF loading are also discussed
Recent Publications :
- Pretty, C., Whitaker, M. & Williams, S. (2017). Thermo-Mechanical Fatigue Crack Growth of RR1000. Materials 10(1), 34
- Jones, J., Whittaker, M., Lancaster, R. & Williams, S. (2017). The influence of phase angle, strain range and peak cycle temperature on the TMF crack initiation behaviour and damage mechanisms of the nickel-based superalloy, RR1000. International Journal of Fatigue , 98, 279-285
- Jones, J., Brookes, S., Whittaker, M. & Lancaster, R. (2014). Non-invasive temperature measurement and control techniques under thermomechanical fatigue loading. Materials Science and Technology 30(15), 1862-1876.
- Pretty, C., Whittaker, M. & Williams, S. (2014). Crack Growth of a Polycrystalline Nickel Alloy under TMF Loading. Advanced Materials Research 891-892, 1302-1307.
- Lancaster, R., Whittaker, M. & Williams, S. (2013). A review of thermo-mechanical fatigue behaviour in polycrystalline nickel superalloys for turbine disc applications. Materials at High Temperatures 30(1), 2-12.