Domestic object damage and fatigue behaviour of an advanced gamma TiAl alloy

Laboratory simulated domestic object damage (DOD) was imposed on aerofoil style specimens manufactured from a latest generation gamma titanium aluminide. The form of the impact sites was characterised in detail before assessment under fatigue loading at room temperature and 650°C. A reduction in fatigue strength due to the presence of DOD was shown to be sensitive to the projectile impact energy but independent of test … Continue reading Domestic object damage and fatigue behaviour of an advanced gamma TiAl alloy

Surface topography and the impact on fatigue performance

Areal characterization was applied to plain fatigue specimens manufactured from a nickel-based superalloy, Alloy 720Li, to determine the impact of machined/finished surface topography on fatigue performance of this material. Samples were subjected to fatigue testing in the as-turned and shot peened conditions to study the interaction between residual stresses and topography in influencing the fatigue performance. The turning process was deliberately manipulated to produce three … Continue reading Surface topography and the impact on fatigue performance

Surface Roughness, Areal Topographic Measurement, and Correlation to LCF Behavior in a Nickel-Based Superalloy

Surface roughness often determines fatigue performance of advanced engineering components making definition of this parameter essential subsequent to manufacture. Traditionally, topography measurements employ an average amplitude parameter, Ra, obtained from a two-dimensional contact measurement. This parameter, however, is highly localised making it relatively unreliable. This study attempts to correlate areal (3D) topographic, measurements with the low cycle fatigue (LCF) performance defined for a nickel-based superalloy … Continue reading Surface Roughness, Areal Topographic Measurement, and Correlation to LCF Behavior in a Nickel-Based Superalloy

The effects of machined topography on fatigue life of a nickel based superalloy

The surface topography of engineering components is known to affect fatigue behaviour. However, defining topography based on the average roughness (Ra) parameter is considered to be inadequate when correlating to fatigue performance. Alternative correlations utilising areal topographic parameters would therefore be valuable. This has been addressed through areal topographic measurements and fatigue testing of an advanced nickel based superalloy, Alloy720Li. Low cycle and high cycle … Continue reading The effects of machined topography on fatigue life of a nickel based superalloy

Titanium alloy developments for aeroengine fan systems

Recent research relating to two α+β processed titanium alloys, designed for specific employment in aeroengine fan disc and aerofoil components, is described. Timetal 575 (Ti575) and Timetal 639 (Ti639) are both novel compositions that provide relatively high strength compared to Ti–6Al–4V. Static and cyclic behaviour of the two developmental alloys were evaluated at room temperature. A dwell fatigue assessment of Ti575 is reported, while the … Continue reading Titanium alloy developments for aeroengine fan systems

Fatigue behaviour of geometric features subjected to laser shock peening: Experiments and modelling

Finite element models, using the eigenstrain approach, are described that predict the residual stress fields associated with laser shock peening (LSP) applied to aerospace grade aluminium alloys. The model was used to explain the results of laboratory fatigue experiments, containing different LSP patch geometries, supplementary stress raising features and different specimen thickness. It is shown that interactions between the LSP process and geometric features are … Continue reading Fatigue behaviour of geometric features subjected to laser shock peening: Experiments and modelling

Experimental and crystal plasticity studies of deformation and crack nucleation in a titanium alloy

This paper presents recent developments in crystal plasticity modelling to incorporate a non-local crack nucleation criterion and the comparison of experimental observations and model predictions for deformation and crack nucleation in a near-alpha titanium (Ti) alloy polycrystal. The model polycrystal was established so as to have grain morphology and crystallography nominally identical to that in the experiment, enabling direct interpretation and comparison of the results. … Continue reading Experimental and crystal plasticity studies of deformation and crack nucleation in a titanium alloy