Deposits of clastic carbonate-dominated (calciclastic) sedimentary slope systems in the rock record have been identified mostly as linearly-consistent carbonate apron deposits, even though most ancient clastic carbonate slope deposits fit the submarine fan systems better. Calciclastic submarine fans are consequently rarely described and are poorly understood. Subsequently, very little is known especially in mud-dominated calciclastic submarine fan systems. Presented in this study are a sedimentological core and petrographic characterisation of samples from eleven boreholes from the Lower Carboniferous of Bowland Basin (Northwest England) that reveals a >250 m thick calciturbidite complex deposited in a calciclastic submarine fan setting. Seven facies are recognised from core and thin section characterisation and are grouped into three carbonate turbidite sequences. They include: 1) Calciturbidites, comprising mostly of highto low-density, wavy-laminated bioclast-rich facies; 2) low-density densite mudstones which are characterised by planar laminated and unlaminated muddominated facies; and 3) Calcidebrites which are muddy or hyper-concentrated debrisflow deposits occurring as poorly-sorted, chaotic, mud-supported floatstones. These

Phd by thesis

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American Society for Testing and Materials

It is well known that mechanical surface treatments, such as deep rolling, shot peening and laser shock peening, can significantly improve the fatigue behavior of highly-stressed metallic components. Deep rolling (DR) is particularly attractive since it is possible to generate, near the surface, deep compressive residual stresses and work hardened layers while retaining a relatively smooth surface finish. In the present investigation, the effect of DR on the low-cycle fatigue (LCF) and high-cycle fatigue (HCF) behavior of a Ti–6Al–4V alloy is examined, with particular emphasis on the thermal and mechanical stability of the residual stress states and the near-surface microstructures. Preliminary results on laser shock peened Ti–6Al–4V are also presented for comparison. Particular emphasis is devoted to the question of whether such surface treatments are effective for improving the fatigue properties at elevated temperatures up to ∼450 °C, i.e. at a homologous temperature of ∼0.4 T/T m (where T m is the melting temperature). Based on cyclic deformation and stress/life ( S / N ) fatigue behavior, together with the X-ray diffraction and in situ transmission electron microscopy (TEM) observations of the microstructure, it was found that deep rolling can be quite effective in retarding the initiation and initial propagation of fatigue cracks in Ti–6Al–4V at such higher temperatures, despite the almost complete relaxation of the near-surface residual stresses. In the absence of such stresses, it is shown that the near-surface microstructures, which in Ti–6Al–4V consist of a layer of work hardened nanoscale grains, play a critical role in the enhancement of fatigue life by mechanical surface treatment.

On the influence of mechanical surface treatments—deep rolling and laser shock peening—on the fatigue behavior of Ti–6Al–4V at ambient and elevated temperatures

A critical review of powder-based additive manufacturing of ferrous alloys: Process parameters, microstructure and mechanical properties

Grain refinement mechanism of multiple laser shock processing impacts on ANSI 304 stainless steel

Laser shock processing and its effects on microstructure and properties of metal alloys: a review

The fatigue behaviour of an ultra-high strength steel (>1800 MPa) was evaluated to assess the potential of using laser cladding as a repair tool for such steels in aeronautical structural applications. AISI 4340 and AerMet 100 steel powder were used to clad over a grind-out region in an AISI 4340 steel substrate using a 2.5 kW ND:YAG laser. Post-clad heat treatment (PCHT) was also investigated. Results showed very poor tensile properties and significantly reduced fatigue life of the AISI 4340 as-clad with a very high hardness and brittle fracture in the clad and HAZ zone. Residual stress results showed a compressive residual stress in the clad region and tensile residual stress in the HAZ. Changing the alloy of the clad layer to AerMet 100 steel, as well as applying a PCHT process, showed promising results as the fatigue life was improved from that of the grind-out substrate.

Effect of laser clad repair on the fatigue behaviour of ultra-high strength AISI 4340 steel

Assessing organisational factors in aircraft accidents using a hybrid Reason and AcciMap model

Laser cladding (LC) was used to investigate the repair of high strength steel in aircraft applications, such as landing gears. This paper reports on the microstructure and microhardness properties of the deposited AISI 4340 clad layer on AISI 4340 steel substrate. Microhardness results showed the clad layer was 30-40% harder than the base material. Stress relieving the clad allowed the clad and HAZ areas to soften 10% below the base material. High dilution provided a favorable result on the hardness at the interface.

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Microstructure and mechanical properties of laser cladding repair of AISI 4340 steel

Aircraft paint schemes (paint and sealant) are a key element of corrosion preventive measures, and ensuring that such schemes and other coatings are effective and durable under service conditions is essential if corrosion costs and maintenance costs are to be minimized Coatings can degrade under the influence of environmental factors such as exposure to moisture, high temperature, ultraviolet radiation, and so forth Coating failure is often particularly evident at joints, and while failure may be accelerated in some regions by local variations in coating thickness and geometry at features such as edges, or by erosion, it is likely that the displacements which occur at these locations under service loads will be a contributing factor The impact of in-service mechanical loading on coating degradation has so far received little attention, despite clear evidence that coatings tend to fail first at specific sites such as sheet ends and around fastener heads This paper argues that the magnitude of the applied service loads and the nature of the load history should be considered in predicting and assessing rates of coating degradation, and that development of a thermomechanical history is a more appropriate approach The likely impact of joint displacements on the protection of aging aircraft is also discussed

Graham Clark

Papers

Laser shock processing and its effects on microstructure and properties of metal alloys: a review

Effect of laser clad repair on the fatigue behaviour of ultra-high strength AISI 4340 steel

Assessing organisational factors in aircraft accidents using a hybrid Reason and AcciMap model

Microstructure and mechanical properties of laser cladding repair of AISI 4340 steel

Impact of Mechanical Strain Environment on Aircraft Protective Coatings and Corrosion Protection